Seagen Inc. - Quarter Report: 2017 March (Form 10-Q)

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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-Q

(Mark One)

For the quarterly period ended March 31, 2017

OR

For the transition period from                      to                     

Commission file number 0-32405

SEATTLE GENETICS, INC.

(Exact name of registrant as specified in its charter)

21823 30^th Drive SE

Bothell, Washington 98021

(Address of principal executive offices, including zip code)

(Registrant’s telephone number, including area code): (425) 527-4000

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days.    Yes  ☒    No  ☐

Indicate by check mark whether the registrant has submitted electronically and posted on its corporate Web site, if any, every Interactive Data File required to be submitted and posted pursuant to Rule 405 of Regulation S-T during the preceding 12 months (or for such shorter period that the registrant was required to submit and post such files).    Yes  ☒    No  ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act.  ☐

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act).    Yes  ☐    No  ☒

As of April 26, 2017, there were 142,716,597 shares of the registrant’s common stock outstanding.

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Seattle Genetics, Inc. Quarterly

Report on Form 10-Q

For the Quarter Ended March 31, 2017

INDEX

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PART I. FINANCIAL INFORMATION

Seattle Genetics, Inc.

Condensed Consolidated Balance Sheets

(Unaudited)

(In thousands, except par value)

The accompanying notes are an integral part of these condensed consolidated financial statements.

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Seattle Genetics, Inc.

Condensed Consolidated Statements of Comprehensive Loss

(Unaudited)

(In thousands, except per share amounts)

The accompanying notes are an integral part of these condensed consolidated financial statements.

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Seattle Genetics, Inc.

Condensed Consolidated Statements of Cash Flows

(Unaudited)

(In thousands)

The accompanying notes are an integral part of these condensed consolidated financial statements.

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Seattle Genetics, Inc.

Notes to Condensed Consolidated Financial Statements

(Unaudited)

1. Summary of significant accounting policies

Basis of presentation

The accompanying unaudited condensed consolidated financial statements reflect the accounts of Seattle Genetics, Inc. and its wholly-owned subsidiaries (collectively “Seattle Genetics” or the “Company”). All intercompany transactions and balances have been eliminated. Management has determined that the Company operates in one segment: the development and sale of pharmaceutical products on its own behalf or in collaboration with others. Substantially all of the Company’s assets and revenues are related to operations in the United States; however, the Company also has subsidiaries in Canada, Switzerland and the United Kingdom.

The condensed consolidated balance sheet data as of December 31, 2016 were derived from audited financial statements not included in this quarterly report on Form 10-Q. The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with the rules and regulations of the Securities and Exchange Commission, or SEC, and generally accepted accounting principles in the United States of America, or GAAP, for unaudited condensed consolidated financial information. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. The accompanying unaudited condensed consolidated financial statements reflect all adjustments consisting of normal recurring adjustments which, in the opinion of management, are necessary for a fair statement of the Company’s financial position and results of its operations, as of and for the periods presented.

Unless indicated otherwise, all amounts presented in financial tables are presented in thousands, except for per share and par value amounts.

These unaudited condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and accompanying notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2016, as filed with the SEC.

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the condensed consolidated financial statements and accompanying notes. Actual results could differ from those estimates. The results of the Company’s operations for the three month period ended March 31, 2017 are not necessarily indicative of the results to be expected for the full year.

Non-cash investing activities

The Company had $3.2 million and $8.1 million of accrued capital expenditures as of March 31, 2017 and December 31, 2016, respectively. Accrued capital expenditures have been treated as a non-cash investing activity and, accordingly, have not been included in the statement of cash flows until such amounts have been paid in cash.

Investments

The Company invests cash resources primarily in debt securities. In addition, as of March 31, 2017, the Company also held an equity investment in Immunomedics, Inc., or Immunomedics, common stock as further described in Note 6. These debt and equity securities are classified as available-for-sale, which are reported at estimated fair value with unrealized gains and losses included in accumulated other comprehensive income (loss) in stockholders’ equity. Realized gains, realized losses and declines in the value of securities judged to be other-than-temporary, are included in investment and other income, net. The cost of investments for purposes of computing realized and unrealized gains and losses is based on the specific identification method. Amortization of premiums and accretion of discounts on debt securities are included in investment and other income, net. Interest and dividends earned on all securities are included in investment and other income, net. The Company classifies investments in debt securities maturing within one year of the reporting date, or where management’s intent is to use the investments to fund current operations or to make them available for current operations, as short-term investments. The Company classifies its equity investment in Immunomedics in other non-current assets.

If the estimated fair value of a security is below its carrying value, the Company evaluates whether it is more likely than not that it will sell the security before its anticipated recovery in market value and whether evidence indicating that the cost of the investment is recoverable within a reasonable period of time outweighs evidence to the contrary. The Company also evaluates whether or not it intends to sell the investment. If the impairment is considered to be other-than-temporary, the security is written down to its estimated fair value. In addition, the Company considers whether credit losses exist for any securities. A credit loss exists if the present value of cash flows expected to be collected is less than the amortized cost basis of the security. Other-than-temporary declines in estimated fair value and credit losses are charged against investment and other income, net.

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Other non-current assets

In addition to the equity investment in Immunomedics, other non-current assets included a $5.0 million non-controlling investment in a privately-held company that is accounted for under the cost method of accounting. The Company periodically evaluates the carrying value of the investment if significant adverse events or circumstances indicate an impairment in value. As of March 31, 2017, no impairment in value had been observed.

Long-term incentive plans

The Company has established Long-Term Incentive Plans, or LTIPs. The LTIPs provide eligible employees with the opportunity to receive performance-based incentives, which may be comprised of a cash payment, stock options, and restricted stock units. As of March 31, 2017, the estimated value to be delivered under the LTIPs was $42.9 million. No compensation expense has been recorded to date under the LTIPs. The total potential value to be delivered under the LTIPs is expected to change in the future for several reasons, including the addition of more eligible employees to the LTIPs.

Revenue recognition

The Company’s revenues are comprised of ADCETRIS net product sales, amounts earned under its collaboration and licensing agreements and royalties. Revenue recognition is predicated upon persuasive evidence of an agreement existing, delivery of products or services being rendered, amounts payable being fixed or determinable, and collectibility being reasonably assured.

Net product sales

The Company sells ADCETRIS through a limited number of pharmaceutical distributors in the U.S. and Canada. Customers order ADCETRIS through these distributors and the Company typically ships product directly to the customer. The Company records product sales when title and risk of loss pass, which generally occurs upon delivery of the product to the customer. Product sales are recorded net of estimated government-mandated rebates and chargebacks, distribution fees, estimated product returns and other deductions. Accruals are established for these deductions and actual amounts incurred are offset against applicable accruals. The Company reflects these accruals as either a reduction in the related account receivable from the distributor, or as an accrued liability depending on the nature of the sales deduction. Sales deductions are based on management’s estimates that consider payer mix in target markets and experience to date. These estimates involve a substantial degree of judgment.

Government-mandated rebates and chargebacks: The Company has entered into a Medicaid Drug Rebate Agreement, or MDRA, with the Centers for Medicare & Medicaid Services. This agreement provides for a rebate based on covered purchases of ADCETRIS. Medicaid rebates are invoiced to the Company by the various state Medicaid programs. The Company estimates Medicaid rebates based on a variety of factors, including its experience to date. The Company has also completed a Federal Supply Schedule, or FSS, agreement under which certain U.S. government purchasers receive a discount on eligible purchases of ADCETRIS. The Company has entered into a Pharmaceutical Pricing Agreement with the Secretary of Health and Human Services, which enables certain entities that qualify for government pricing under the Public Health Services Act, or PHS, to receive discounts on their qualified purchases of ADCETRIS. Under these agreements, distributors process a chargeback to the Company for the difference between wholesale acquisition cost and the applicable discounted price. As a result of the Company’s direct-ship distribution model, it can determine the entities purchasing ADCETRIS and this information enables the Company to estimate expected chargebacks for FSS and PHS purchases based on each entity’s eligibility for the FSS and PHS programs. The Company also reviews historical rebate and chargeback information to further refine these estimates.

Distribution fees, product returns and other deductions: The Company’s distributors charge a volume-based fee for distribution services that they perform for the Company. The Company allows for the return of product that is within 30 days of its expiration date or that is damaged. The Company estimates product returns based on its experience to date. In addition, the Company considers its direct-ship distribution model, its belief that product is not typically held in the distribution channel, and the expected rapid use of the product by healthcare providers. The Company provides financial assistance to qualifying patients that are underinsured or cannot cover the cost of commercial coinsurance amounts through SeaGen Secure. SeaGen Secure is available to patients in the U.S. and its territories who meet various financial and treatment need criteria. Estimated contributions for commercial coinsurance under SeaGen Secure are deducted from gross sales and are based on an analysis of expected plan utilization. These estimates are adjusted as necessary to reflect the Company’s actual experience.

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Collaboration and license agreement revenues

The Company has developed a proprietary technology for linking cytotoxic agents to monoclonal antibodies called antibody-drug conjugates, or ADCs. This proprietary technology is the basis of ADC collaborations that the Company has entered into in the ordinary course of its business with a number of biotechnology and pharmaceutical companies. Under these ADC collaboration agreements, the Company grants its collaborators research and commercial licenses to the Company’s technology and provides technology transfer services, technical advice, supplies and services for a period of time.

If there are continuing performance obligations, the Company uses a time-based proportional performance model to recognize revenue over the Company’s performance period for the related agreement. Collaboration and license agreements are evaluated to determine whether the multiple elements and associated deliverables can be considered separate units of accounting. To date, the pre-commercial deliverables under the Company’s collaboration and license agreements have not qualified as separate units of accounting. The assessment of multiple element arrangements requires judgment in order to determine the appropriate point in time, or period of time, that revenue should be recognized. The Company believes that the development period in each agreement is a reasonable estimate of the performance obligation period of such agreement. Accordingly, all amounts received or due, including any upfront payments, maintenance fees, development and regulatory milestone payments and reimbursement payments, are recognized as revenue over the performance obligation periods of each agreement. These performance obligation periods typically range from one to three years. The agreements with Takeda Pharmaceutical Company Limited, or Takeda, and Genentech, Inc., a member of the Roche Group, or Genentech, have performance obligation periods of ten and seventeen years, respectively. All of the remaining performance obligation periods for our active collaborations are currently expected to be completed in three years or less. When no performance obligations are required of the Company, or following the completion of the performance obligation period, such amounts are recognized as revenue when collectibility is reasonably assured. Generally, all amounts received or due other than sales-based milestones and royalties are classified as collaboration and license agreement revenues as they are earned. Sales-based milestones and royalties are recognized as royalty revenue as they are reported to the Company.

The Company’s collaboration and license agreements include contractual milestones. Generally, the milestone events contained in the Company’s collaboration and license agreements coincide with the progression of the collaborators’ product candidates from development, to regulatory approval and then to commercialization and fall into the following categories.

Development milestones in the Company’s collaborations may include the following types of events:

Regulatory milestones in the Company’s collaborations may include the following types of events:

Commercialization milestones in the Company’s collaborations may include the following types of events:

The Company’s ADC collaborators are solely responsible for the development of their product candidates and the achievement of milestones in any of the categories identified above is based solely on the collaborators’ efforts.

In the case of the Company’s ADCETRIS collaboration with Takeda, the Company may be involved in certain development activities; however, the achievement of milestone events under the agreement is primarily based on activities undertaken by Takeda.

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The process of successfully developing a product candidate, obtaining regulatory approval and ultimately commercializing a product candidate is highly uncertain and the attainment of any milestones is therefore uncertain and difficult to predict. In addition, since the Company does not take a substantive role or control the research, development or commercialization of any products generated by its ADC collaborators, the Company is not able to reasonably estimate when, if at all, any milestone payments or royalties may be payable to the Company by its ADC collaborators. As such, the milestone payments associated with its ADC collaborations involve a substantial degree of uncertainty and risk that they may never be received. Similarly, even in those collaborations where the Company may have an active role in the development of the product candidate, such as the Company’s ADCETRIS collaboration with Takeda, the attainment of a milestone is based on the collaborator’s activities and is generally outside the direction and control of the Company.

The Company generally invoices its collaborators and licensees on a monthly or quarterly basis, or upon the completion of the effort or achievement of a milestone, based on the terms of each agreement. Deferred revenue arises from amounts received in advance of the culmination of the earnings process and is recognized as revenue in future periods when the applicable revenue recognition criteria have been met. Deferred revenue expected to be recognized within the next twelve months is classified as a current liability.

Royalty revenues and cost of royalty revenues

Royalty revenues primarily reflect amounts earned under the ADCETRIS collaboration with Takeda. These royalties include sales royalties, which are based on a percentage of Takeda’s net sales at rates that range from the mid-teens to the mid-twenties based on sales volume, and commercial sales-based milestones. Takeda bears a portion of third-party royalty costs owed on its sales of ADCETRIS. This amount is included in royalty revenue in the Company’s consolidated financial statements. Cost of royalty revenues reflects amounts owed to the Company’s third party licensors related to Takeda’s sales of ADCETRIS. These amounts are recognized in the quarter in which Takeda reports its sales activity to the Company, which is the quarter following the related sales. Royalty revenues also include amounts earned in connection with the Company’s ADC collaborations.

Recent accounting pronouncements

In May 2014, the Financial Accounting Standards Board, or FASB, issued an Accounting Standards Update entitled “ASU 2014-09, Revenue from Contracts with Customers.” The standard requires entities to recognize revenue through an evaluation that includes identification of the contract, identification of the performance obligations, determination of the transaction price, allocation of the transaction price to the performance obligations, and recognition of revenue as the entity satisfies the performance obligations. In August 2015, FASB issued an Accounting Standards Update entitled “ASU 2015-14, Revenue from Contracts with Customers: Deferral of the Effective Date”, which defers the effective date of ASU 2014-09 to the Company’s fiscal year beginning January 1, 2018. The FASB has continued to issue accounting standards updates to clarify and provide implementation guidance related to Revenue from Contracts with Customers, including “ASU 2016-08, Revenue from Contract with Customers: Principal versus Agent Considerations”, “ASU 2016-10, Revenue from Contracts with Customers: Identifying Performance Obligations and Licensing”, “ASU 2016-12, Revenue from Contracts with Customers: Narrow-Scope Improvements and Practical Expedients” and “ASU 2016-20, Technical Corrections and Improvements to Topic 606, Revenue from Contracts with Customers.” The Company’s preliminary assessment of this new standard is that it will generally not change the way in which the Company recognizes product revenue from sales of ADCETRIS. However, the Company expects that sales-based royalties and commercial sales-based milestones will be recorded in the period of the related sale based on estimates, rather than recording them as reported by the customer. In addition, the achievement of development milestones under the Company’s collaborations will be recorded in the period their achievement becomes probable, which may result in their recognition earlier than under current accounting principles. The new standard also requires more extensive disclosures related to revenue recognition, particularly in quarterly financial statements. The Company will adopt the standard on January 1, 2018 and intends to use the modified retrospective method of adoption. The Company is continuing to evaluate the impact of the standard on all of its revenues, including those mentioned above, and its assessments may change in the future based on its ongoing evaluation.

In January 2016, FASB issued an Accounting Standards Update entitled “ASU 2016-01, Financial Instruments: Overall.” The standard addresses certain aspects of recognition, measurement, presentation and disclosure of financial instruments. The Company will adopt the standard on January 1, 2018 using a modified retrospective approach. The standard will require that the Company record changes in the fair value of equity securities in net income or loss. The implementation of this standard is expected to increase the volatility of net income to the extent that the Company continues to hold equity securities.

In February 2016, FASB issued an Accounting Standards Update entitled “ASU 2016-02, Leases.” The standard requires entities to recognize in the consolidated balance sheet a liability to make lease payments and a right-of-use asset representing its right to use the underlying asset for the lease term. The standard will become effective for the Company beginning January 1, 2019, with early adoption permitted. The Company is currently evaluating the guidance to determine the potential impact on its financial condition, results of operations and cash flows, and financial statement disclosures.

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In March 2016, FASB issued an Accounting Standard Update entitled “ASU 2016-09, Compensation – Stock Compensation.” The standard is intended to simplify certain elements of accounting for share-based payment transactions, including the income tax impact, classification of awards as either equity or liabilities, and classification on the statement of cash flows. In addition, the standard allows an entity-wide accounting policy election to either estimate the number of awards that are expected to vest, as currently required, or account for forfeitures when they occur. The Company has elected to continue estimating the number of awards that are expected to vest. The Company adopted the standard as of January 1, 2017. Since the Company has incurred net losses since its inception and maintains a full valuation allowance on its net deferred tax assets, the adoption did not have a material impact on the Company’s financial condition, results of operations and cash flows.

In October 2016, FASB issued an Accounting Standard Update entitled “ASU 2016-16, Accounting for Income Taxes: Intra-Entity Asset Transfers of Assets Other than Inventory”. The standard is intended to simplify the accounting for intercompany sales of assets other than inventory. Under current GAAP, the tax effects of intra-entity asset transfers are deferred until the transferred asset is sold to a third party or otherwise recovered through use. Under the new guidance, a reporting entity would recognize the tax expense from the sale of the asset in the seller’s jurisdiction when the transfer occurs, even though the pre-tax effects of that transaction are eliminated in consolidation. Any deferred tax asset that arises in the buyer’s jurisdiction would also be recognized at the time of the transfer. The standard will become effective for the Company beginning on January 1, 2018. The Company is currently evaluating the new standard; however, since the Company has incurred net losses since its inception and maintains a full valuation allowance on its net deferred tax assets, the adoption is not expected to have a material impact on the Company’s financial condition, results of operations and cash flows, or financial statement disclosures.

In June 2016, FASB issued an Accounting Standard Update entitled “ASU 2016-13, Financial Instruments: Credit Losses”. The objective of the standard is to provide information about expected credit losses on financial instruments at each reporting date, and to change how other than temporary impairments on investments securities are recorded. The standard will become effective for the Company beginning on January 1, 2020 with early adoption permitted. The Company is currently evaluating the guidance to determine the potential impact on its financial condition, results of operations and cash flows, and financial statement disclosures.

In January 2017, FASB issued an Accounting Standard Update entitled, “ASU 2017-01, Business Combinations: Clarifying the Definition of a Business.” The objective of the standard is to clarify the definition of a business with the objective of adding guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions of assets or businesses. The Company adopted this standard on a prospective basis as of January 1, 2017. The adoption of this standard did not have a material impact on the Company’s financial condition, results of operations and cash flows, or financial statement disclosures.

2. Net loss per share

Basic and diluted net loss per share is computed by dividing net loss by the weighted average number of common shares outstanding during the period. The Company excluded all restricted stock units and options to purchase common stock from the calculation of basic and diluted net loss per share as such securities are anti-dilutive for all periods presented. The weighted-average number of restricted stock units and options to purchase common stock that have been excluded from the number of shares used to calculate basic and diluted net loss per share totaled 13,321,000 and 12,321,000 for the three months ended March 31, 2017 and 2016, respectively.

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3. Investments

Investments consisted of available-for-sale securities as follows (in thousands):

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Investments are presented in the accompanying consolidated balance sheets as follows (in thousands):

The aggregate estimated fair value of the Company’s investments with unrealized losses was as follows (in thousands):

4. Fair value

The Company holds short-term and long-term available-for-sale securities that are measured at fair value which is determined on a recurring basis according to a fair value hierarchy that prioritizes the inputs and assumptions used, and the valuation techniques used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1 measurements) and the lowest priority to unobservable inputs (Level 3 measurements). The three levels of the fair value hierarchy are described as follows:

The determination of a financial instrument’s level within the fair value hierarchy is based on an assessment of the lowest level of any input that is significant to the fair value measurement. The Company considers observable data to be market data which is readily available, regularly distributed or updated, reliable and verifiable, not proprietary, and provided by independent sources that are actively involved in the relevant market.

Level 1 investments are valued based on quoted market prices in active markets. The Company did not hold any Level 2 or 3 investments as of March 31, 2017 or December 31, 2016 and did not transfer any investments between Levels 1, 2 and 3 during the three month period ended March 31, 2017.

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The following table presents the Company’s available-for-sale securities by level within the fair value hierarchy for the periods presented (in thousands):

5. Inventories

The following table presents the Company’s inventories of ADCETRIS (in thousands):

The Company capitalizes ADCETRIS inventory costs. ADCETRIS inventory that is deployed into clinical, research or development use is charged to research and development expense when it is no longer available for use in commercial sales. The Company does not capitalize manufacturing costs for any of its product candidates.

6. Immunomedics, Inc. stock purchase agreement

In February 2017, the Company entered into a stock purchase agreement, or the Stock Purchase Agreement, with Immunomedics in connection with a potential development and license agreement, or the Immunomedics License. The Company paid Immunomedics $14.7 million as consideration for 3.0 million shares of Immunomedics common stock and a warrant to purchase an additional 8.7 million shares of common stock at an exercise price $4.90 per share. The consideration was allocated between the common stock and the warrant based on the relative fair values as of the closing date, or $12.7 million and $2.0 million, respectively. The shares of common stock are classified as available-for-sale securities and carried at estimated fair value with unrealized gains and losses included in accumulated other comprehensive income (loss) in stockholders’ equity. The common stock investment is included in other non-current assets as of March 31, 2017. Based on management’s assessment, the value of the warrant was determined to be substantially impaired as of March 31, 2017, and charged to investment and other income (loss), net, for the three months ended March 31, 2017.

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7. Legal matters

On January 10, 2017, the Company became a named defendant in a securities class action complaint seeking compensatory damages of an undisclosed amount. On March 29, 2017, a stockholder derivative lawsuit was filed in Washington Superior Court for the County of Snohomish, naming as defendants certain of the Company’s current and former executive officers and members of its board of directors. The Company is named as a nominal defendant. The Company does not believe it is feasible to predict or determine the outcome or resolution of these proceedings, or to estimate the amount of, or potential range of, loss with respect to these proceedings. In addition, the timing of the final resolution of these proceedings is uncertain. As a result of these lawsuits, the Company will incur litigation expenses and may incur indemnification expenses, and potential resolutions of the lawsuits could include settlements requiring payments. Those expenses could have a material impact on the Company’s financial position, results of operations, and cash flows.

On February 13, 2017, the Company was named a co-defendant in a lawsuit filed by venBio in the Delaware Chancery Court, or the Court, against the members of the board of directors of Immunomedics. The lawsuit alleges that the members of the Immunomedics board breached their fiduciary duties toward their stockholders by hastily licensing IMMU-132 to the Company. The Company is alleged to have aided and abetted the breach of fiduciary duties. On March 9, 2017, the Court issued a temporary restraining order enjoining taking any action in furtherance of the closing of the transactions contemplated by the Immunomedics License. The temporary restraining order will remain in place pending a trial on the merits scheduled for June 19, 2017. The Company cannot predict the outcome of the lawsuit or the impact it may have on the Immunomedics License or the Stock Purchase Agreement, or the closing of the transactions contemplated by the Immunomedics License. Further, it is possible that, in connection with the lawsuit, the Immunomedics License or the Stock Purchase Agreement could be terminated, rescinded or reformed in a way that is disadvantageous to us, including a potential increase in the transaction consideration payable to Immunomedics under the Immunomedics License, or that otherwise adversely affects the anticipated benefits to us of the Immunomedics License. The Company does not believe it is feasible to predict or determine the outcome or resolution of this lawsuit, or to estimate the amount of, or potential range of, loss with respect to this lawsuit, including any potential impacts on the value of the common stock purchased by the Company. In addition, the timing of the final resolution of this lawsuit is uncertain. As a result of the lawsuit, the Company will incur litigation expenses, and potential resolution of the lawsuit could include a settlement requiring payments. Those expenses could have a material impact on the Company’s financial position, results of operations, and cash flows.

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Forward-Looking Statements

The following discussion of our financial condition and results of operations contains forward-looking statements within the meaning of Section 27A of the Securities Act of 1933 and Section 21E of the Securities Exchange Act of 1934. Forward-looking statements are based on our management’s beliefs and assumptions and on information currently available to our management. All statements other than statements of historical facts are “forward-looking statements” for purposes of these provisions, including those relating to future events or our future financial performance and financial guidance. In some cases, you can identify forward-looking statements by terminology such as “may,” “might,” “will,” “should,” “expect,” “plan,” “anticipate,” “project,” “believe,” “estimate,” “predict,” “potential,” “intend” or “continue,” the negative of terms like these or other comparable terminology, and other words or terms of similar meaning in connection with any discussion of future operating or financial performance. These statements are only predictions. All forward-looking statements included in this Quarterly Report on Form 10-Q are based on information available to us on the date hereof, and we assume no obligation to update any such forward-looking statements except as required by law. Any or all of our forward-looking statements in this document may turn out to be incorrect. Actual events or results may differ materially. Our forward-looking statements can be affected by inaccurate assumptions we might make or by known or unknown risks, uncertainties and other factors. We discuss many of these risks, uncertainties and other factors in this Quarterly Report on Form 10-Q in greater detail under the heading “Item 1A—Risk Factors.” We caution investors that our business and financial performance are subject to substantial risks and uncertainties.

Overview

Seattle Genetics is a biotechnology company focused on the development and commercialization of targeted therapies for the treatment of cancer. Our marketed product ADCETRIS^®, or brentuximab vedotin, is now approved by the United States Food and Drug Administration, or FDA, and the European Commission for three indications, encompassing several settings for the treatment of relapsed Hodgkin lymphoma and relapsed systemic anaplastic large cell lymphoma, or sALCL. ADCETRIS is commercially available in 66 countries around the world, including in the United States, Canada, members of the European Union and Japan. We are collaborating with Takeda Pharmaceutical Company Limited, or Takeda, to develop and commercialize ADCETRIS on a global basis. Under this collaboration, Seattle Genetics retains commercial rights for ADCETRIS in the United States and its territories and in Canada, and Takeda has commercial rights in the rest of the world.

Beyond our current labeled indications, we and Takeda have a broad development strategy for ADCETRIS evaluating its therapeutic potential in earlier lines of therapy for patients with Hodgkin lymphoma or mature T-cell lymphoma, or MTCL, also known as peripheral T-Cell lymphoma, or PTCL, including sALCL, and in other CD30-expressing malignancies. We and Takeda are currently conducting three phase 3 clinical trials of ADCETRIS: ALCANZA, ECHELON-1 and ECHELON-2. All of these trials are being conducted under Special Protocol Assessment, or SPA, agreements with the FDA and pursuant to scientific advice from the European Medicines Agency, or EMA. An SPA is an agreement with the FDA regarding the design of the clinical trial, including size and clinical endpoints, to support an efficacy claim in a new drug application or a Biologics License Application, or BLA, submission to the FDA if the trial achieves its primary endpoints. We plan to submit a supplemental Biologics License Application, or sBLA, to the FDA in mid-2017 to seek approval for a new indication in CD30-expressing relapsed CTCL. We have also completed enrollment of 1,334 patients in our ECHELON-1 trial and expect to report data in 2017. In November 2016, we completed enrollment of 452 patients in our ECHELON-2 trial, and expect to report data in 2018.

We are also advancing the development of SGN-CD33A, or vadastuximab talirine. A phase 3 clinical trial, called the CASCADE trial, was initiated in the second quarter of 2016 based on data from our phase 1 clinical trial for patients with acute myeloid leukemia, or AML. The CASCADE trial is evaluating SGN-CD33A in combination with hypomethylating agents, or HMAs, in previously untreated older patients with AML who are not candidates for intensive induction chemotherapy. In addition, we plan to initiate a randomized phase 2 trial during 2017 evaluating SGN-CD33A in combination with standard of care chemotherapy in frontline, younger AML patients. On March 6, 2017, we announced that the FDA had lifted the clinical hold announced on December 27, 2016 on phase 1 trials of SGN-CD33A in AML.

In addition, in collaboration with Astellas Pharma, Inc., or Astellas, we are developing ASG-22ME, or enfortumab vedotin. Based on recent discussions with the FDA, in the second half of 2017, we and Astellas plan to initiate a pivotal phase 2 clinical trial for metastatic urothelial cancer patients who have been previously treated with a checkpoint inhibitor therapy.

Our clinical-stage pipeline also includes six other antibody-drug conjugate, or ADC, programs consisting of SGN-LIV1A, SGN-CD19A, or denintuzumab mafodotin, SGN-CD19B, SGN-CD123A, SGN-CD352A, and ASG-15ME, as well as two immuno-oncology agents, SEA-CD40, which is based on our sugar-engineered antibody, or SEA, technology, and SGN-2FF, which is a novel small molecule. In addition, we have multiple preclinical and research-stage programs that employ our proprietary technologies, including SGN-CD48A.

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We announced on February 10, 2017 that we had entered into a development and license agreement, or the Immunomedics License, with Immunomedics, Inc., or Immunomedics, pursuant to which, upon the terms and subject to the conditions set forth in the Immunomedics License, we would receive exclusive worldwide rights to develop, manufacture and commercialize sacituzumab govitecan, or IMMU-132. IMMU-132 is an ADC targeted to TROP-2, which is expressed in several solid tumors, and is in a pivotal phase 1/2 trial for patients with triple negative breast cancer, or TNBC, and is being investigated in other solid tumors. IMMU-132 received Breakthrough Therapy Designation, or BTD, from the FDA for the treatment of patients with TNBC who have failed prior therapies for metastatic disease. In the event that the transaction closes, under the terms of the Immunomedics License, we would pay Immunomedics an upfront payment of $250 million. In addition, Immunomedics would also be eligible to receive development, regulatory and sales-dependent milestone payments across multiple indications and geographical regions of up to a total maximum of approximately $1.7 billion, as well as royalties which would be based on a percentage of annual net sales of the licensed products, if any, beginning in the teens and rising to twenty percent based on sales volume. In addition, on February 10, 2017, we also entered into an agreement, or the Stock Purchase Agreement, to purchase 3,000,000 shares of common stock of Immunomedics at an aggregate purchase price of $14.7 million, and on February 16, 2017, Immunomedics issued us a warrant to purchase up to 8,655,804 additional shares of common stock of Immunomedics at an exercise price of $4.90 per share which is exercisable until February 10, 2020. On February 13, 2017, we were named a co-defendant in a lawsuit filed by venBio Select Advisors LLC, or venBio, in the Delaware Chancery Court, or the Court, against the members of the board of directors of Immunomedics pursuant to which, among other things, venBio sought to enjoin the closing of the transactions contemplated by the Immunomedics License. On March 9, 2017, the Court issued a temporary restraining order enjoining taking any action in furtherance of the closing of the transactions contemplated by the Immunomedics License. The temporary restraining order will remain in place pending a trial on the merits currently scheduled for June 19, 2017. We cannot predict the outcome of this legal proceeding or the impact it may have on the Immunomedics License or the Stock Purchase Agreement, or the closing of the transactions contemplated by the Immunomedics License. However, it is possible that, in connection with the venBio lawsuit, the Immunomedics License or the Stock Purchase Agreement could be terminated, rescinded or reformed in a way that is disadvantageous to us, including a potential increase in the transaction consideration payable to Immunomedics under the Immunomedics License, or that otherwise adversely affects the anticipated benefits to us of the Immunomedics License. In any event, we may be unable to consummate the transactions contemplated by the Immunomedics License, whether as a result of the venBio lawsuit or otherwise, in which case we will not realize any of the benefits of the licensing of IMMU-132.

We have collaborations for our ADC technology with a number of biotechnology and pharmaceutical companies, including AbbVie Biotechnology Ltd., or AbbVie; Bayer Pharma AG, or Bayer; Celldex Therapeutics, Inc., or Celldex; Genentech, Inc., a member of the Roche Group, or Genentech; GlaxoSmithKline LLC, or GSK; Pfizer, Inc., or Pfizer; and PSMA Development Company LLC, a subsidiary of Progenics Pharmaceuticals Inc., or Progenics. In addition, we have entered into a 50/50 co-development agreement with Agensys, Inc., an affiliate of Astellas, for the development of ADCs, including ASG-22ME. We also have an option for an ADC co-development agreement with Genmab A/S, or Genmab, and a collaboration with Unum Therapeutics, Inc., or Unum, to develop and commercialize novel antibody-coupled T-cell receptor, or ACTR, therapies incorporating our antibodies for the treatment of cancer.

Our ongoing research, development and commercial activities will require substantial amounts of capital and may not ultimately be successful. Over the next several years, we expect that we will incur substantial expenses, primarily as a result of activities related to the commercialization of ADCETRIS, and the continued development of ADCETRIS and SGN-CD33A. Our other product candidates are in relatively early stages of development; SGN-CD33A, and our other product candidates will require significant further development, financial resources and personnel to pursue and obtain regulatory approval and develop into commercially viable products, if at all. In addition, SGN-CD33A is our only product candidate in late stage clinical development and if we are unable to advance the development of SGN-CD33A, or if we fail to produce positive results in the CASCADE trial, the commercialization prospects for SGN-CD33A, as well as our business and financial prospects, would be materially adversely affected. Our commitment of resources to the continuing development, regulatory and commercialization activities for ADCETRIS, the research, continued development and manufacturing of our product candidates, and the transactions contemplated by the Immunomedics License, if consummated, would likely require us to raise substantial amounts of additional capital and our operating expenses would fluctuate as a result of such activities. In addition, we may incur significant milestone payment obligations to certain of our licensors as our product candidates progress through clinical trials towards potential commercialization.

We recognize revenue from ADCETRIS product sales in the United States and Canada. Our future ADCETRIS product sales are difficult to accurately predict from period to period. In this regard, our product sales have varied, and may continue to vary, significantly from period to period and may be affected by a variety of factors. Such factors include the incidence rate of new patients in ADCETRIS’ approved indications, customer ordering patterns, the overall level of demand for ADCETRIS, the duration of therapy for patients receiving ADCETRIS, and the extent to which coverage and reimbursement for ADCETRIS is available from government and other third-party payers. Obtaining and maintaining appropriate coverage and reimbursement for ADCETRIS is increasingly challenging due to, among other things, the attention being paid to healthcare cost containment and other austerity measures in the U.S. and worldwide, as well as increasing legislative and enforcement interest in the United States with respect to pharmaceutical drug pricing practices. We anticipate that healthcare reform measures that may be adopted in the future may result in more rigorous coverage criteria and an additional downward pressure on the price that we receive for ADCETRIS. We also anticipate that Congress, state legislatures, and third-party payors may continue to review and assess alternative healthcare delivery and payment systems and may in the future propose and adopt legislation or policy changes or implementations effecting additional fundamental changes in the healthcare delivery system,

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any of which could negatively affect our revenue or sales of ADCETRIS (or any future approved products). We also believe that the level of our current ADCETRIS sales in the United States has been attributable to the incidence flow of patients eligible for treatment with ADCETRIS, which can vary significantly from period to period. Moreover, we believe that the incidence rate in ADCETRIS’ approved indications is relatively low, particularly when compared to many other oncology indications. For these and other reasons, we expect that our ability to accelerate ADCETRIS sales growth, if at all, will depend primarily on our ability to continue to expand ADCETRIS’ labeled indications of use, particularly with respect to the frontline Hodgkin lymphoma and frontline MTCL indications. Our efforts to continue to expand ADCETRIS’ labeled indications of use will continue to require additional time and investment in clinical trials to complete and may not be successful. Our ability to successfully commercialize ADCETRIS and to continue to expand its labeled indications of use are subject to a number of risks and uncertainties, including those discussed in Part II, Item 1A of this Quarterly Report on Form 10-Q. In particular, negative or inconclusive results in our ECHELON-1 and ECHELON-2 trials would negatively impact, or preclude altogether, our ability to obtain regulatory approval in the frontline Hodgkin lymphoma and frontline MTCL indications, respectively, either of which could limit our sales of, and the commercial potential of, ADCETRIS. In addition, although we reported in August 2016 that the ALCANZA trial evaluating ADCETRIS in patients with relapsed CTCL met its primary endpoint demonstrating a statistically significant improvement in the rate of objective response lasting at least four months and we plan to submit an sBLA to the FDA to seek approval for a new indication in CD30-expressing relapsed CTCL, there can be no assurance that the FDA will accept our planned sBLA for filing or that we will ultimately obtain approval of our planned sBLA in a timely manner or at all. Our failure to obtain regulatory approval and commercialize ADCETRIS in the ALCANZA treatment setting would also limit our sales of, and the commercial potential of, ADCETRIS. We also expect that amounts earned from our collaboration agreements, including royalties, will continue to be an important source of our revenues and cash flows. These revenues will be impacted by future development funding and the achievement of development, clinical and commercial success by our collaborators under our existing collaboration and license agreements, including our ADCETRIS collaboration with Takeda, as well as by entering into potential new collaboration and license agreements. Our results of operations may vary substantially from year to year and from quarter to quarter and, as a result, we believe that period to period comparisons of our operating results may not be meaningful and should not be relied upon as being indicative of our future performance.

Financial summary

For the three months ended March 31, 2017, total revenues decreased to $109.1 million, compared to $111.2 million for the same period in 2016. This decrease was driven primarily by royalty revenues, which included a one-time $20.0 million milestone payment in 2016, offset by an increase in ADCETRIS net product sales. Net product sales of ADCETRIS were $70.3 million for the three months ended March 31, 2017, compared to $58.6 million for the three months ended March 31, 2016. For the three months ended March 31, 2017, total costs and expenses increased to $168.4 million, compared to $132.2 million for the same period in 2016. This primarily reflects increased investment in ASG-22ME and SGN-CD33A, as well as investment in our growing pipeline of pre-clinical and clinical-stage programs. As of March 31, 2017, we had $536.4 million in cash, cash equivalents and short- and long-term investments, and $603.4 million in total stockholders’ equity.

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Results of operations

Three months ended March 31, 2017 and 2016

Net product sales

We sell ADCETRIS in the U.S. and Canada. Our net product sales were as follows ($ in thousands):

The increase in net product sales for the three months ended March 31, 2017 over the comparable period in 2016 primarily resulted from an increase in sales volume in the 2017 period, and to a lesser extent, from the effect of price increases instituted since the 2016 period. The increase in sales volume in 2017 was primarily driven by increased use of ADCETRIS across multiple lines of therapy in Hodgkin lymphoma and for the treatment of other CD30-expressing malignancies.

We expect continued growth in ADCETRIS sales in 2017 as compared to 2016. Our ability to accelerate the rate of ADCETRIS sales growth in future periods, if at all, will be primarily dependent on our ability to continue to expand ADCETRIS’ labeled indications of use. Our efforts to expand ADCETRIS’ labeled indications of use will continue to require additional time and investment in clinical trials to complete and may not be successful.

We sell ADCETRIS through a limited number of pharmaceutical distributors. Customers order ADCETRIS through these distributors and we typically ship product directly to the customer. We record product sales when title and risk of loss pass, which generally occurs upon delivery of the product to the customer. Product sales are recorded net of estimated government-mandated rebates and chargebacks, distribution fees, estimated product returns and other deductions. These are generally referred to as gross-to-net deductions. Accruals are established for these deductions and actual amounts incurred are offset against applicable accruals. We reflect these accruals as either a reduction in the related account receivable from the distributor, or as an accrued liability depending on the nature of the sales deduction. Sales deductions are based on our estimates that consider payer mix in target markets and our experience to date. These estimates involve a substantial degree of judgment.

Government-mandated rebates and chargebacks: We have entered into a Medicaid Drug Rebate Agreement with the Centers for Medicare & Medicaid Services. This agreement provides for a rebate to participating states based on covered purchases of ADCETRIS. Medicaid rebates are invoiced to us by the various state Medicaid programs. We estimate Medicaid rebates based on a variety of factors, including our experience to date. We also have completed our Federal Supply Schedule, or FSS, agreement under which certain U.S. government purchasers receive a discount on eligible purchases of ADCETRIS. We have entered into a Pharmaceutical Pricing Agreement with the Secretary of Health and Human Services which enables certain entities that qualify for government pricing under the Public Health Services Act, or PHS, to receive discounts on their qualified purchases of ADCETRIS. Under these agreements, distributors process a chargeback to us for the difference between wholesale acquisition cost and the applicable discounted price. As a result of our direct-ship distribution model, we can identify the entities purchasing ADCETRIS and this information enables us to estimate expected chargebacks for FSS and PHS purchases based on each entity’s eligibility for the FSS and PHS programs. We also review actual rebate and chargeback information to further refine these estimates.

Distribution fees, product returns and other deductions: Our distributors charge a volume-based fee for distribution services that they perform for us. We allow for the return of product that is within 30 days of its expiration date or that is damaged. We estimate product returns based on our experience to date. In addition, we consider our direct-ship distribution model, our belief that product is not typically held in the distribution channel, and the expected rapid use of the product by healthcare providers. We provide financial assistance to qualifying patients that are underinsured or cannot cover the cost of commercial coinsurance amounts through SeaGen Secure. SeaGen Secure is available to patients in the U.S. and its territories who meet various financial and treatment need criteria. Estimated contributions for commercial coinsurance under SeaGen Secure are deducted from gross sales and are based on an analysis of expected plan utilization. These estimates are adjusted as necessary to reflect our actual experience.

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Gross-to-net deductions, net of related payments and credits, are summarized as follows (in thousands):

Mandatory government discounts are the most significant component of our total gross to net deductions and the discount percentage has been increasing. These discount percentages increased during the three months ended March 31, 2017 over the comparable period in 2016 as a result of price increases we instituted that exceeded the rate of inflation, and to a lesser extent, as a result of an increase in sales eligible for government mandated rebates or chargebacks. Generally, the change in government prices is limited to the rate of inflation. We expect future gross-to-net deductions to fluctuate based on the volume of purchases eligible for government mandated discounts and rebates, as well as changes in the discount percentage which is impacted by potential future price increases, the rate of inflation, and other factors.

We implemented a price increase at the beginning of 2017. As a result of this price increase and a continued increase in the percentage of our gross sales that are eligible for government mandated rebates and chargebacks, we expect gross-to-net deductions to increase in 2017. In recent months there has been extensive discussion in the United States about expanding government discount programs, including allowing Medicare to negotiate drug prices, and pressure on pharmaceutical drug pricing is expected to increase. If government discounted programs are expanded or discounts increased as a result of changes in regulations in the United States, our gross to net deductions will increase and our net sales will be negatively impacted.

Collaboration and license agreement revenues

Our proprietary ADC technologies are the basis of our ADC collaborations that we have entered into in the ordinary course of business with a number of biotechnology and pharmaceutical companies. Under these ADC collaboration agreements, we grant our collaborators research and commercial licenses to our technology and typically provide technology transfer services, technical advice, supplies and services for a period of time.

If there are continuing performance obligations, we use a time-based proportional performance model to recognize revenue over our performance period for the related agreement. Collaboration and license agreements are evaluated to determine whether the multiple elements and associated deliverables can be considered separate units of accounting. To date, the pre-commercial deliverables under our collaboration and license agreements have not qualified as separate units of accounting. The assessment of multiple element arrangements requires judgment in order to determine the appropriate point in time, or period of time, that revenue should be recognized. We believe that the development period in each agreement is a reasonable estimate of the performance obligation period of such agreement. Accordingly, all amounts received or due, including any upfront payments, maintenance fees, development and regulatory milestone payments and reimbursement payments, are recognized as revenue over the performance obligation periods of each agreement. These performance obligation periods typically range from one to three years. The agreements with Takeda and Genentech have performance obligation periods of ten and seventeen years, respectively. All of the remaining performance obligation periods for our active collaborations are currently expected to be completed in three years or less. When no performance obligations are required of us, or following the completion of the performance obligation period, such amounts are recognized as revenue when collectibility is reasonably assured. Generally, all amounts received or due other than sales-based milestones and royalties are classified as collaboration and license agreement revenues as they are earned. Sales-based milestones and royalties are recognized as royalty revenue as they are reported to us.

Our collaboration and license agreements include contractual milestones. Generally, the milestone events contained in our collaboration and license agreements coincide with the progression of the collaborators’ product candidates from development to regulatory approval and then to commercialization.

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Development milestones in our collaborations may include the following types of events:

Regulatory milestones in our collaborations may include the following types of events:

Commercialization milestones in our collaborations may include the following types of events:

Our ADC collaborators are solely responsible for the development of their product candidates and the achievement of milestones in any of the categories identified above is based solely on the collaborators’ efforts.

In the case of our ADCETRIS collaboration with Takeda, we may be involved in certain development activities; however, the achievement of development, regulatory and commercial milestone events under the agreement is primarily based on activities undertaken by Takeda.

The process of successfully developing a product candidate, obtaining regulatory approval and ultimately commercializing a product candidate is highly uncertain and the attainment of any milestones is therefore uncertain and difficult to predict. In addition, since we do not take a substantive role or control the research, development or commercialization of any products generated by our ADC collaborators, we are not able to reasonably estimate when, if at all, any milestone payments or royalties may be payable to us by our ADC collaborators. As such, the milestone payments associated with our ADC collaborations involve a substantial degree of uncertainty and risk that they may never be received. Similarly, even in those collaborations where we may have an active role in the development of the product candidate, such as our ADCETRIS collaboration with Takeda, the attainment of a milestone is based on the collaborator’s activities and is generally outside our direction and control.

We generally invoice our collaborators and licensees on a monthly or quarterly basis, or upon the completion of the effort or achievement of a milestone, based on the terms of each agreement. Any deferred revenue arising from amounts received in advance of the culmination of the earnings process is recognized as revenue in future periods when the applicable revenue recognition criteria have been met. Deferred revenue expected to be recognized within the next twelve months is classified as a current liability.

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Collaboration and license agreement revenues by collaborator are summarized as follows:

Collaboration revenues from Takeda fluctuate based on changes in the earned portion of reimbursement funding under the ADCETRIS collaboration, which are influenced by the activities each party is performing under the collaboration agreement at a given time. Collaboration revenues from Takeda increased during the three months ended March 31, 2017 from the comparable period in 2016, primarily driven by an increase in drug product supply activities.

Revenues from AbbVie decreased during the three months ended March 31, 2017 from the comparable period in 2016 due to the completion of the performance obligation period in 2016, over which the upfront payments, maintenance fees, development milestone payments were being amortized.

Changes in revenues recognized from our other collaboration agreements, which include our ADC collaborations and our co-development collaborations, reflect the timing of development milestones and licensing fees.

Our collaboration and license agreement revenues are impacted by the term and duration of our collaboration and license agreements and by progress-dependent milestones, annual maintenance fees and reimbursement of materials and support services. Collaboration and license agreement revenues may vary substantially from year to year and quarter to quarter depending on the progress made by our collaborators with their product candidates, the level of support we provide to our collaborators, specifically to Takeda under our ADCETRIS collaboration, the timing of milestones achieved and our ability to enter into additional collaboration and co-development agreements. We expect our collaboration and license agreement revenues in 2017 to be consistent with 2016. We have a significant balance of deferred revenue, representing prior payments from our collaborators that have not yet been recognized as revenue. This deferred revenue will be recognized as revenue in future periods using a time-based approach as we fulfill our performance obligations.

Collaboration agreements

Takeda

Our ADCETRIS collaboration with Takeda provides for the global co-development of ADCETRIS by the companies and the commercialization of ADCETRIS by Takeda in its territory. We received an upfront payment and have received and are entitled to receive progress-dependent milestone payments based on Takeda’s achievement of significant events under the collaboration, in addition to tiered royalties with percentages starting in the mid-teens and escalating to the mid-twenties based on net sales of ADCETRIS within Takeda’s licensed territories. Additionally, the companies equally co-fund the cost of selected development activities conducted under the collaboration. We recognize as collaboration revenue the upfront payment, progress-dependent milestone payments, and net development cost reimbursement payments from Takeda over the ten-year development period of the collaboration, which began in December 2009. When the performance of development activities under the collaboration results in us making a reimbursement payment to Takeda, the effect is to reduce the amount of collaboration revenue that we record. We also receive reimbursement for the cost of drug product supplied to Takeda for its use and, in some cases, pay Takeda for drug product they supply to us. The earned portion of net collaboration payments is reflected as a component of collaboration and license agreement revenues.

As of March 31, 2017, total future potential milestone payments to us under the ADCETRIS collaboration could total approximately $165 million. Of the remaining amount, up to approximately $7 million relates to the achievement of development milestones, up to approximately $118 million relates to the achievement of regulatory milestones and up to approximately $40 million relates to the achievement of commercial milestones. As of March 31, 2017, $70 million in milestones had been achieved as a result of regulatory and commercial progress by Takeda.

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Astellas Co-development Agreement

We entered into an agreement with Agensys, subsequently acquired by Astellas, to jointly research, develop and commercialize ADCs for the treatment of several types of cancer. The collaboration encompasses combinations of our ADC technology with fully-human antibodies developed by Astellas to proprietary cancer targets.

Under the collaboration agreement, we and Astellas are co-funding all development and commercialization costs for ASG-22ME and ASG-15ME, and will share in any profits that may come from these product candidates if successfully commercialized on a 50/50 basis. Costs associated with co-development activities are included in research and development expense.

Astellas is developing another ADC product candidate on its own, subject to paying us annual maintenance fees, milestones, royalties and support fees for research and development services and material provided under the collaboration agreement. Amounts received for this product candidate being developed solely by Astellas are recognized as revenue.

Unum Therapeutics

We have a strategic collaboration and license agreement with Unum to develop and commercialize novel ACTR therapies incorporating our antibodies for cancer. We and Unum will initially develop two ACTR product candidates that combine Unum’s ACTR technology with our antibodies, and we have an option to expand the collaboration to include a third ACTR product candidate upon payment of an additional fee. Unum is obligated to conduct preclinical research and clinical development activities through phase 1 clinical trials and we are obligated to provide funding for these activities. The agreement calls for us to work together to co-develop and jointly fund programs after phase 1 clinical trials unless either company opts out. Costs associated with co-development activities are included in research and development expense.

We and Unum would co-commercialize any successfully developed product candidates and share any profits 50/50 on any co- developed programs in the United States. We retain exclusive commercial rights outside of the United States, paying Unum a royalty that is a high single digit to mid-teens percentage of ex-U.S. sales, if any. The potential future licensing and progress-dependent milestone payments to Unum under the collaboration may total up to $615 million across all three ACTR programs, payment of which is triggered by the achievement of development, regulatory and commercial milestones.

ADC Collaboration Agreements

We have other active collaborations with a number of companies to allow them to use our proprietary ADC technology. Under our ADC collaborations, which we have entered into in the ordinary course of business, we typically receive or are entitled to receive upfront cash payments, progress-dependent milestones and royalties on net sales of products incorporating our ADC technology, as well as annual maintenance fees and support fees for research and development services and materials provided under the agreements. These amounts are recognized as revenue as they are realized, or over the performance obligation period of the agreements during which we provide limited support to the collaborator. Our ADC collaborators are responsible for development, manufacturing and commercialization of any ADC product candidates that result from the collaborations and are solely responsible for the achievement of the potential milestones under these collaborations.

As of March 31, 2017, our ADC collaborations and co-development agreements had generated more than $350 million, primarily in the form of upfront payments. Total milestone payments to us under our current ADC collaboration and co-development agreements could total up to approximately $3.3 billion if all potential product candidates achieved all of their milestone events. Of this amount, approximately $0.5 billion relates to the achievement of development milestones, approximately $1.3 billion relates to the achievement of regulatory milestones and approximately $1.5 billion relates to the achievement of commercial milestones. Since we do not control the research, development or commercialization of any of the products that would generate these milestones, we are not able to reasonably estimate when, if at all, any milestone payments or royalties may be payable by our collaborators. Successfully developing a product candidate, obtaining regulatory approval and ultimately commercializing it is a significantly lengthy and highly uncertain process which entails a significant risk of failure. In addition, business combinations, changes in a collaborator’s business strategy and financial difficulties or other factors could result and have resulted in a collaborator abandoning or delaying development of its product candidates. As such, the milestone payments associated with our ADC collaborations and co-development agreements involve a substantial degree of risk and may never be received. Accordingly, we do not expect, and investors should not assume, that we will receive all of the potential milestone payments described above and it is possible that we may never receive any significant milestone payments under these agreements.

Royalty revenues and cost of royalty revenues

Royalty revenues primarily reflect royalties paid to us by Takeda under the ADCETRIS collaboration. These royalties include commercial sales-based milestones and sales royalties. The royalty rate paid by Takeda is calculated as a percentage of Takeda’s net sales of ADCETRIS, ranges from the mid-teens to the mid-twenties depending on sales volumes, and resets annually. Takeda bears a portion of third-party royalty costs owed on sales of ADCETRIS in its territory. This amount is included in our royalty revenues. Cost of royalty revenues reflect amounts owed to our third-party licensors related to the sale of ADCETRIS in Takeda’s territory.

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Our royalty revenues and cost of royalty revenues were as follows ($ in thousands):

Royalty revenues for the three months ended March 31, 2017 decreased from the comparable period in 2016 as the three month period ended March 31, 2016 included a one-time $20.0 million milestone payment triggered by Takeda’s exceeding $200 million in annual sales for the first time. The decrease driven by the milestone payment was partially offset in 2017 by increases in sales volume and thereby in the applicable royalty rate.

Cost of royalty revenues fluctuates based on the amount of net sales of ADCETRIS by Takeda in its territories.

We expect that royalty revenues will decrease in 2017 as compared to 2016 primarily as a result of the 2016 royalty revenues including the one-time $20 million sales milestone payment. We expect cost of royalty revenues to increase in 2017 primarily due to anticipated increases in sales volumes in Takeda’s territory.

Cost of sales

ADCETRIS cost of sales includes manufacturing costs of product sold, third-party royalty costs, amortization of technology license costs, and distribution and other costs. Our cost of sales was as follows ($ in thousands):

Cost of sales increased during the three month period ended March 31, 2017 as compared to 2016 primarily due to increased sales volumes, and to a lesser extent, due to an increase in the applicable royalty rate. We expect cost of sales to increase in 2017, primarily due to anticipated increases in sales volumes.

Research and development

Our research and development expenses are summarized as follows:

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Research expenses include, among other things, personnel, occupancy and laboratory expenses, technology access fees associated with the discovery and identification of new monoclonal antibodies and related technologies, and the development of novel classes of stable linkers and cell-killing agents for our ADC technology. Research expenses also include research activities associated with our product candidates, such as preclinical translational biology and in vitro and in vivo studies, and investigational new drug, or IND-enabling pharmacology and toxicology studies. The increase in research expenses during the three months ended March 31, 2017 as compared to the same period in 2016 reflects increases in staffing as well as increased cost reimbursement under our agreement with Astellas.

Development and contract manufacturing expenses include personnel and occupancy expenses, external contract manufacturing costs for the scale up and pre-approval manufacturing of drug product used in research and our clinical trials, and costs for drug product supplied to our collaborators. Development and contract manufacturing expenses also include quality control and assurance activities, and storage and shipment of our product candidates. The increase in development and contract manufacturing expenses during the three months ended March 31, 2017 as compared to the same period in 2016 primarily reflects increased development activities under our agreement with Astellas as well as increased drug product supplied to Takeda, and to a lesser extent, increases in staffing and other costs to support our growing pipeline of product candidates.

Clinical expenses include personnel, travel, occupancy costs, and external clinical trial costs including costs for clinical sites, clinical research organizations, contractors and regulatory activities associated with conducting human clinical trials. The increase in clinical expenses during the three months ended March 31, 2017 as compared to the same period in 2016 reflects increased clinical trial activity related to our product candidates, primarily SGN-CD33A, and related increases in staffing.

We utilize our employee and infrastructure resources across multiple development projects as well as our discovery and research programs directed towards identifying monoclonal antibodies and new classes of stable linkers and cell-killing agents for our ADC program. We track human resource efforts expended on many of our programs for purposes of billing our collaborators for time incurred at agreed upon rates and for resource planning. We do not account for actual costs on a project-by-project basis as it relates to our infrastructure, facility, employee and other indirect costs. We do, however, separately track significant third-party costs including clinical trial costs, manufacturing costs and other contracted service costs on a project-by-project basis.

The following table shows expenses incurred for research, contract manufacturing of our product candidates and clinical and regulatory services provided by third parties as well as pre-commercial milestone payments for in-licensed technology for ADCETRIS and each of our clinical-stage product candidates. The table also presents other third-party costs and overhead consisting of personnel, facilities and other indirect costs not directly charged to these development programs.

Third-party costs for ADCETRIS increased during the three months ended March 31, 2017 from the comparable period in 2016, primarily due to an increase in drug product supplied to Takeda, offset partially by a decrease in clinical trial activities. The cost of drug product supplied to Takeda is charged to research and development expense. We are reimbursed for the drug product, which is included as a component of collaboration revenue.

Third-party costs for SGN-CD33A increased during the three months ended March 31, 2017 from the comparable period in 2016 primarily due to an increase in clinical trial costs related to the phase 3 CASCADE clinical trial, and continued planning for potential additional SGN-CD33A phase 1 and 2 trials.

Third-party costs for ASG-22ME increased during the three months ended March 31, 2017 from the comparable period in 2016 primarily due to an increase in drug supply activities as we prepare to initiate additional clinical trials in 2017.

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Third-party costs for SGN-CD19A and our other development programs were consistent with the comparable period in 2016.

Other costs and overhead include third-party costs of our other preclinical programs, including our strategic collaboration with Unum, and costs associated with personnel and facilities. These costs increased during the three months ended March 31, 2017 from the comparable period in 2016 due to development activities to expand our product pipeline, including increases in staffing levels and the expansion of our facilities to accommodate our growth.

Our expenditures on our ADCETRIS clinical development program and on our current and future preclinical and clinical development programs are subject to numerous uncertainties in timing and cost to completion. In order to advance our product candidates toward commercialization, the product candidates are tested in numerous preclinical safety, toxicology and efficacy studies. We then conduct clinical trials for those product candidates that take several years or more to complete. The length of time varies substantially based upon the type, complexity, novelty and intended use of a product candidate. Likewise, in order to expand ADCETRIS’ labeled indications of use, we are required to conduct additional extensive clinical studies. The cost of clinical trials may vary significantly over the life of a project as a result of a variety of factors, including:

We anticipate that our total research and development expenses in 2017 will increase compared to 2016 due to increased costs for the development of our product candidates, primarily SGN-CD33A, ASG-22ME, SGN-CD19A, and SGN-LIV1A. If the transactions contemplated by the Immunomedics License are consummated, we expect total research and development expenses to potentially increase significantly as a result of the upfront and other milestone payments and development costs that we would undertake as part of the Immunomedics License. Certain ADCETRIS development activities, including some clinical studies, will be conducted by Takeda, the costs of which are not reflected in our research and development expenses. Because of these and other factors, expenses will fluctuate based upon many factors, including the degree of collaborative activities, timing of manufacturing campaigns, numbers of patients enrolled in our clinical trials and the outcome of each clinical trial event.

The risks and uncertainties associated with our research and development projects are discussed more fully in Part II, Item 1A—Risk Factors. As a result of the uncertainties discussed above, we are unable to determine with any degree of certainty the duration and completion costs of our research and development projects, anticipated completion dates or when and to what extent we will receive cash inflows from the commercialization and sale of ADCETRIS in any additional approved indications or of any of our product candidates.

Selling, general and administrative

Selling, general and administrative expenses increased during the three months ended March 31, 2017 from the comparable period in 2016 primarily due to increases in staffing to support our continued growth, and to a lesser extent, increases in expenses for legal matters.

We anticipate that selling, general and administrative expenses will increase in 2017 compared to 2016 as we continue our commercial activities in support of the commercialization of ADCETRIS, as well as our support of general operations. If the transactions contemplated by the Immunomedics License are consummated, we expect selling, general and administrative expenses to increase further.

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Investment and other income (loss), net

Investment and other income (loss), net, includes other non-operating income and amounts earned on our investments in U.S. Treasury securities. The decrease in investment and other income (loss), net from the comparable period in 2016 is primarily related to the impairment of our investment in the Immunomedics warrant.

Liquidity and capital resources

Our combined cash, cash equivalents and investment securities decreased during the three months ended March 31, 2017 from the balance at December 31, 2016, primarily reflecting our net loss for the period, purchases of property and equipment as we expand our facilities to support our growth, and our investment in Immunomedics.

The changes in net cash used in operating activities are primarily related to our net loss, working capital fluctuations and changes in our non-cash expenses, all of which are highly variable. The changes in cash provided by investing activities primarily reflect differences between the proceeds received from sale and maturity of our investments and amounts reinvested. Net cash provided by financing activities resulted from the proceeds of stock option exercises and our employee stock purchase plan.

We have primarily financed our operations through the issuance of equity securities, collections from commercial sales of ADCETRIS, and by amounts received pursuant to product collaborations and our ADC collaborations. To a lesser degree, we have also financed our operations through royalty revenues and interest earned on cash, cash equivalents and investment securities. These financing and revenue sources have historically allowed us to maintain adequate levels of cash and investments.

Our cash, cash equivalents, and investments in debt securities are held in a variety of non-interest bearing bank accounts and interest-bearing instruments subject to investment guidelines allowing for holdings in U.S. government and agency securities, corporate securities, taxable municipal bonds, commercial paper and money market accounts. Our investment portfolio is structured to provide for investment maturities and access to cash to fund our anticipated working capital needs. However, if our liquidity needs should be accelerated for any reason in the near term, or investments do not pay at maturity, we may be required to sell investments in debt securities in our portfolio prior to their scheduled maturities, which may result in a loss. As of March 31, 2017, we had $506.4 million held in cash and cash equivalents, or short-term investments scheduled to mature within the next twelve months.

At our currently planned spending rates we believe that our financial resources, together with product and royalty revenues from sales of ADCETRIS and the fees, milestone payments and reimbursements we expect to receive under our existing collaboration and license agreements, will be sufficient to fund our operations for at least the next twelve months, including with respect to the upfront payment we would be required to make to Immunomedics if the transactions contemplated by the Immunomedics License are consummated on the currently-agreed upon terms. Changes in our spending rate may occur that would consume available capital resources sooner, such as increased development, manufacturing and clinical trial expenses in connection with our expanding pipeline

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programs, including several phase 3 trials, or our undertaking of additional programs, business activities, or entry into strategic transactions, including potential additional acquisitions of products, technologies or businesses. In addition, we do not currently have sufficient capital to fund all of the potential milestone payments to Immunomedics, if the transactions contemplated by the Immunomedics License are consummated, and to Unum under our agreements with those companies. Accordingly, we may be required to, or may otherwise determine to, raise additional capital to fund those obligations. Further, in the event of a termination of the ADCETRIS collaboration agreement with Takeda, we would not receive development cost sharing payments or milestone payments or royalties for the development or sale of ADCETRIS in Takeda’s territory, and we would be required to fund all ADCETRIS development and commercial activities. Any of these factors could lead to a need for us to raise additional capital.

We expect to make additional capital outlays and to increase operating expenditures over the next several years as we hire additional employees, support our preclinical development, manufacturing and clinical trial activities for ADCETRIS and our other pipeline programs, and expand internationally, as well as commercialize ADCETRIS and position ADCETRIS for potential additional regulatory approvals. Our commitment of resources to the continuing development, regulatory and commercialization activities for ADCETRIS, and the research, continued development and manufacturing of our product candidates will likely require us to raise substantial amounts of additional capital. In addition, if the Immunomedics License transaction closes, we anticipate committing substantial capital resources to the transactions contemplated by the Immunomedics License and the anticipated transfer, integration and development activities related to IMMU-132, including with respect to our upfront and milestone payment obligations to Immunomedics. Further, we actively evaluate various strategic transactions on an ongoing basis, including licensing or otherwise acquiring complementary products, technologies or businesses, and we may require significant additional capital in order to complete or otherwise provide funding for any additional acquisitions. We may seek additional funding through some or all of the following methods: corporate collaborations, licensing arrangements and public or private debt or equity financings. We do not know whether additional capital will be available when needed, or that, if available, we will obtain financing on terms favorable to us or our stockholders. If we are unable to raise additional funds when we need them, we may be required to delay, reduce the scope of, or eliminate one or more of our development programs, which may adversely affect our business and operations.

Commitments

Our future minimum contractual commitments were reported in our Annual Report on Form 10-K for the year ended December 31, 2016, as filed with the SEC.

In the event that the transaction closes, under the terms of the Immunomedics License, we would pay Immunomedics an upfront payment of $250 million. In addition, Immunomedics would also be eligible to receive development, regulatory and sales-dependent milestone payments across multiple indications and geographical regions of up to a total maximum of approximately $1.7 billion, as well as royalties which would be based on a percentage of annual net sales of the licensed products, if any, beginning in the teens and rising to twenty percent based on sales volume. Other than with respect to the Immunomedics License, there were no other material changes from the contractual commitments previously disclosed in our Annual Report on Form 10-K for the year ended December 31, 2016, as filed with the SEC.

Recent accounting pronouncements

In May 2014, the Financial Accounting Standards Board, or FASB, issued an Accounting Standards Update entitled “ASU 2014-09, Revenue from Contracts with Customers.” The standard requires entities to recognize revenue through an evaluation that includes identification of the contract, identification of the performance obligations, determination of the transaction price, allocation of the transaction price to the performance obligations, and recognition of revenue as the entity satisfies the performance obligations. In August 2015, FASB issued an Accounting Standards Update entitled “ASU 2015-14, Revenue from Contracts with Customers: Deferral of the Effective Date”, which defers the effective date of ASU 2014-09 to our fiscal year beginning January 1, 2018. The FASB has continued to issue accounting standards updates to clarify and provide implementation guidance related to Revenue from Contracts with Customers, including “ASU 2016-08, Revenue from Contract with Customers: Principal versus Agent Considerations”, “ASU 2016-10, Revenue from Contracts with Customers: Identifying Performance Obligations and Licensing”, “ASU 2016-12, Revenue from Contracts with Customers: Narrow-Scope Improvements and Practical Expedients” and “ASU 2016-20, Technical Corrections and Improvements to Topic 606, Revenue from Contracts with Customers.” Our preliminary assessment of this new standard is that it will generally not change the way in which we recognize product revenue from sales of ADCETRIS. However, we expect that sales-based royalties and commercial sales-based milestones will be recorded in the period of the related sale based on estimates, rather than recording them as reported by the customer. In addition, the achievement of development milestones under our collaborations will be recorded in the period their achievement becomes probable, which may result in their recognition earlier than under current accounting principles. The new standard also requires more extensive disclosures related to revenue recognition, particularly in quarterly financial statements. We will adopt the standard on January 1, 2018 and intend to use the modified retrospective method of adoption. We are continuing to evaluate the impact of the standard on all of our revenues, including those mentioned above, and our assessments may change in the future based on our ongoing evaluation.

        In January 2016, FASB issued an Accounting Standards Update entitled “ASU 2016-01, Financial Instruments: Overall.” The standard addresses certain aspects of recognition, measurement, presentation and disclosure of financial instruments. We will adopt the standard on January 1, 2018 using a modified retrospective approach. The standard will require us to record changes in fair value of equity securities in net income or loss. The implementation of this standard is expected to increase the volatility of net income to the extent that we continue to hold equity securities.

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In February 2016, FASB issued an Accounting Standards Update entitled “ASU 2016-02, Leases.” The standard requires entities to recognize in the consolidated balance sheet a liability to make lease payments and a right-of-use asset representing its right to use the underlying asset for the lease term. The standard will become effective for us beginning January 1, 2019, with early adoption permitted. We are currently evaluating the guidance to determine the potential impact on our financial condition, results of operations and cash flows, and financial statement disclosures.

In March 2016, FASB issued an Accounting Standard Update entitled “ASU 2016-09, Compensation – Stock Compensation.” The standard is intended to simplify certain elements of accounting for share-based payment transactions, including the income tax impact, classification of awards as either equity or liabilities, and classification on the statement of cash flows. In addition, the standard allows an entity-wide accounting policy election to either estimate the number of awards that are expected to vest, as currently required, or account for forfeitures when they occur. We have elected to continue estimating the number of awards that are expected to vest. We adopted the standard as of January 1, 2017. Since we have incurred net losses since our inception and maintain a full valuation allowance on our net deferred tax assets, the adoption did not have a material impact on our financial condition, results of operations and cash flows.

In October 2016, FASB issued an Accounting Standard Update entitled “ASU 2016-16, Accounting for Income Taxes: Intra-Entity Asset Transfers of Assets Other than Inventory”. The standard is intended to simplify the accounting for intercompany sales of assets other than inventory. Under current GAAP, the tax effects of intra-entity asset transfers are deferred until the transferred asset is sold to a third party or otherwise recovered through use. Under the new guidance, a reporting entity would recognize the tax expense from the sale of the asset in the seller’s jurisdiction when the transfer occurs, even though the pre-tax effects of that transaction are eliminated in consolidation. Any deferred tax asset that arises in the buyer’s jurisdiction would also be recognized at the time of the transfer. The standard will become effective for us beginning on January 1, 2018. We are currently evaluating the new standard; however, since we have incurred net losses since our inception and maintain a full valuation allowance on our net deferred tax assets, the adoption is not expected to have a material impact on our financial condition, results of operations and cash flows, or financial statement disclosures.

In June 2016, FASB issued an Accounting Standard Update entitled “ASU 2016-13, Financial Instruments: Credit Losses”. The objective of the standard is to provide information about expected credit losses on financial instruments at each reporting date, and to change how other than temporary impairments on investments securities are recorded. The standard will become effective for us beginning on January 1, 2020 with early adoption permitted. We are currently evaluating the guidance to determine the potential impact on our financial condition, results of operations and cash flows, and financial statement disclosures.

In January 2017, FASB issued an Accounting Standard Update entitled, “ASU 2017-01, Business Combinations: Clarifying the Definition of a Business.” The objective of the standard is to clarify the definition of a business with the objective of adding guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions of assets or businesses. We adopted this standard on a prospective basis as of January 1, 2017. The adoption of this standard did not have a material impact on our financial condition, results of operations and cash flows, or financial statement disclosures.

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Interest Rate Risk

Our exposure to market risk for changes in interest rates relates primarily to our investment portfolio. We do not have any derivative financial instruments in our investment portfolio. We currently have holdings in U.S. Treasury securities. A summary of our investment in debt securities subject to interest rate risk are as follows (in thousands):

We have estimated the effect on our investment portfolio of a hypothetical increase in interest rates by one percent to be a reduction of $1.7 million in the fair value of our available-for-sale debt securities as of March 31, 2017. In addition, a hypothetical decrease of 10% in the effective yield of our available-for-sale debt securities would reduce our expected investment income by approximately $0.3 million over the next twelve months based on our investment balance at March 31, 2017.

Foreign Currency Risk

Most of our revenues and expenses are denominated in U.S. dollars and as a result, we have not experienced significant foreign currency transaction gains and losses to date. Our commercial sales in Canada are denominated in Canadian Dollars. We also had other transactions denominated in foreign currencies during the three months ended March 31, 2017, primarily related to contract manufacturing and ex-U.S. clinical trial activities, and we expect to continue to do so. Our royalties from Takeda are derived from their sales of ADCETRIS in multiple countries and in multiple currencies that are converted into U.S. dollars for purposes of determining the royalty owed to us. Our primary exposure is to fluctuations in the Euro, British Pound, Canadian Dollar and Swiss Franc. We do not anticipate that foreign currency transaction gains or losses will be significant at our current level of operations. However, transaction gains or losses may become significant in the future as we continue to expand our operations internationally. We have not engaged in foreign currency hedging to date; however, we may do so in the future.

(a) Evaluation of disclosure controls and procedures. Our management, with the participation of our Chief Executive Officer and our Chief Financial Officer, have evaluated our disclosure controls and procedures (as defined in Rules 13a-15(e) under the Securities Exchange Act of 1934, as amended) prior to the filing of this quarterly report. Based on that evaluation, our Chief Executive Officer and our Chief Financial Officer have concluded that, as of the end of the period covered by this quarterly report, our disclosure controls and procedures were, in design and operation, effective.

(b) Changes in internal control over financial reporting. There have not been any changes in our internal control over financial reporting during the quarter ended March 31, 2017 that have materially affected, or are reasonably likely to materially affect, our internal control over financial reporting.

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Part II. Other Information

Stockholder Class Action. On January 10, 2017, a purported securities class action lawsuit was commenced in the United States District Court for the Western District of Washington, naming as defendants us and certain of our officers. The lawsuit alleges material misrepresentations and omissions in public statements regarding our business, operational and compliance policies, violations by all named defendants of Section 10(b) of the Exchange Act, and Rule 10b-5 thereunder, as well as violations of Section 20(a) of the Exchange Act. The complaint seeks compensatory damages of an undisclosed amount. The plaintiff alleges, among other things, that we made false and/or misleading statements and/or failed to disclose that SGN-CD33A presents a significant risk of fatal hepatotoxicity and that we had therefore overstated the viability of SGN-CD33A as a treatment for AML. It is possible that additional suits will be filed, or allegations received from stockholders, with respect to these same matters and also naming us and/or our officers and directors as defendants. The court has not yet appointed a lead plaintiff or approved lead plaintiff’s counsel. We do not believe it is feasible to predict or determine the outcome or resolution of this litigation, or to estimate the amount of, or potential range of, loss with respect to this proceeding. In addition, the timing of the final resolution of this proceeding is uncertain. As a result of the lawsuit, we will incur litigation expenses and may incur indemnification expenses, and potential resolutions of the lawsuit could include a settlement requiring payments. Those expenses could have a material impact on our financial position, results of operations, and cash flows.

Stockholder Derivative Action. On March 29, 2017, a stockholder derivative lawsuit was filed in Washington Superior Court for the County of Snohomish. The complaint names as defendants certain of our current and former executives and members of our board of directors. We are named as a nominal defendant. The complaint generally makes the same allegations as the securities class action, claiming that the individual defendants breached their duties to us. The complaint seeks unspecified damages, disgorgement of compensation, corporate governance changes, and attorneys’ fees and costs. Because the complaint is derivative in nature, it does not seek monetary damages from us. As a result of the lawsuit, we may incur litigation and indemnification expenses.

venBio Action. On February 13, 2017, we were named a co-defendant in a lawsuit filed by venBio in the Delaware Chancery Court, or the Court, against the members of the board of directors of Immunomedics. The lawsuit, or the venBio lawsuit, alleges that the members of the Immunomedics board breached their fiduciary duties toward their stockholders by hastily licensing IMMU-132 to us. We are alleged to have aided and abetted the breach of fiduciary duties. Among other things, venBio sought to enjoin the closing of the transactions contemplated by the development and license agreement, or the Immunomedics License, we entered into with Immunomedics in February 2017. On March 9, 2017, the Court issued a temporary restraining order enjoining taking any action in furtherance of the closing of the transactions contemplated by the Immunomedics License. The temporary restraining order will remain in place pending a trial on the merits scheduled for June 19, 2017. We cannot predict the outcome of the venBio lawsuit or the impact it may have on the Immunomedics License, or on the Stock Purchase Agreement, or the closing of the transactions contemplated by the Immunomedics License. However, it is possible that, in connection with the venBio lawsuit, the Immunomedics License or the Stock Purchase Agreement could be terminated, rescinded or reformed in a way that is disadvantageous to us, including a potential increase in the transaction consideration payable to Immunomedics under the Immunomedics License, or that otherwise adversely affects the anticipated benefits to us of the Immunomedics License. We do not believe it is feasible to predict or determine the outcome or resolution of this lawsuit, or to estimate the amount of, or potential range of, loss with respect to this lawsuit. In addition, the timing of the final resolution of this lawsuit is uncertain. As a result of the lawsuit, we will incur litigation expenses, and potential resolution of the lawsuit could include a settlement requiring payments. Those expenses could have a material impact on our financial position, results of operations, and cash flows.

You should carefully consider the following risk factors, in addition to the other information contained in this Quarterly Report on Form 10-Q, including our condensed consolidated financial statements and related notes. If any of the events described in the following risk factors occurs, our business, operating results and financial condition could be seriously harmed. This Quarterly Report on Form 10-Q also contains forward-looking statements that involve risks and uncertainties. Our actual results could differ materially from those anticipated in the forward-looking statements as a result of factors that are described below and elsewhere in this Quarterly Report on Form 10-Q.

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Risks Related to Our Business

Our near-term prospects are substantially dependent on ADCETRIS. If we and/or Takeda are unable to effectively commercialize ADCETRIS for the treatment of patients in its approved indications and to continue to expand its labeled indications of use, our ability to generate significant revenue or potentially achieve profitability will be adversely affected.

ADCETRIS^®, or brentuximab vedotin, is now approved by the United States Food and Drug Administration, or FDA, and the European Commission for three indications, encompassing several settings for the treatment of relapsed Hodgkin lymphoma and relapsed systemic anaplastic large cell lymphoma, or sALCL. ADCETRIS is our only product approved for marketing and our ability to generate revenue from product sales and potentially achieve profitability is substantially dependent on our continued ability to effectively commercialize ADCETRIS for the treatment of patients in its approved indications and our ability to continue to expand its labeled indications of use. We may not be able to fully realize the commercial potential of ADCETRIS for a number of reasons, including:

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In December 2009, we entered into an agreement with Takeda to develop and commercialize ADCETRIS, under which we have commercial rights in the United States and its territories and Canada, and Takeda has commercial rights in the rest of the world. The success of this collaboration and the activities of Takeda will significantly impact the commercialization of ADCETRIS in countries other than the United States and in Canada. In October 2012, Takeda announced that it had received conditional marketing authorization for ADCETRIS from the European Commission for patients with relapsed Hodgkin lymphoma or relapsed sALCL, and has since obtained marketing approvals for ADCETRIS in many other countries. Conditional marketing authorization by the European Commission includes obligations to provide additional clinical data at a later stage to confirm the positive benefit-risk balance. In July 2016, Takeda announced that it had received marketing authorization for ADCETRIS from the European Commission for the treatment of adult patients with CD30-positive Hodgkin lymphoma at increased risk of relapse or progression following autologous stem cell transplant. We cannot control the amount and timing of resources that Takeda dedicates to the commercialization of ADCETRIS, or to its marketing and distribution, and our ability to generate revenues from ADCETRIS product sales by Takeda depends on Takeda’s ability to achieve market acceptance of, and to otherwise effectively market, ADCETRIS for its approved indications in Takeda’s territory.

We believe that the level of our ongoing ADCETRIS sales in the United States is largely attributable to the incidence flow of patients eligible for treatment with ADCETRIS. We also believe that the incidence rate of new patients in ADCETRIS’ approved indications is relatively low, particularly when compared to many other oncology indications. For these and other reasons, we expect that our ability to accelerate ADCETRIS sales growth, if at all, will depend primarily on our ability to continue to expand ADCETRIS’ labeled indications of use. Accordingly, we are exploring the use of ADCETRIS as a single agent and in combination therapy regimens earlier in the treatment of Hodgkin lymphoma and MTCL, including sALCL, and in a range of CD30-expressing hematologic malignancies, including CD30-expressing relapsed CTCL. This will continue to require additional time and investment in clinical trials and there can be no assurance that we and/or Takeda will obtain and maintain the necessary regulatory approvals to market ADCETRIS for any additional indications. In particular, negative or inconclusive results in our ECHELON-1 and ECHELON-2 trials would negatively impact, or preclude altogether, our ability to obtain regulatory approval in the frontline Hodgkin lymphoma and frontline MTCL, indications, respectively, either of which could limit our sales of, and the commercial potential of, ADCETRIS. For example, the SPA agreements for the ECHELON-1 and ECHELON-2 trials require that the trials continue until a specified number of events designated for each trial occur (i.e. progressions or deaths), and since we do not control the rate of events, the final data analysis for the applicable trial could be delayed beyond our expectations. In addition, until the final data analysis is completed for the applicable trial, we cannot be certain that the number of events designated in the applicable SPA agreement has actually occurred and if the designated number of events has not occurred, the FDA may treat the applicable SPA as rescinded and the statistical power of that trial based on the original statistical analysis plan could be negatively impacted, making it more difficult for us to demonstrate that ADCETRIS is safe and effective and to successfully obtain regulatory approval for the specific indication studied in that trial. We may also undertake additional discussions with regulatory authorities or amend the protocol for one or both of these trials, and we cannot predict the outcome of those discussions or whether we would be able to reach agreement with the regulatory authorities, which could result in a delay in our ability to conduct the final data analysis from the applicable trial or otherwise negatively impact the ability of the applicable trial to support approval of ADCETRIS for the specific indication studied in that trial.

In addition, although we reported in August 2016 that the ALCANZA trial evaluating ADCETRIS in patients with relapsed CTCL met its primary endpoint demonstrating a statistically significant improvement in the rate of objective response lasting at least four months and we plan to submit a supplemental Biologics License Application, or sBLA, to the FDA to seek approval for a new indication in CD30-expressing relapsed CTCL, there can be no assurance that the FDA will accept our planned sBLA for filing or that we will ultimately obtain approval of our planned sBLA in a timely manner or at all. Our failure to obtain regulatory approval and commercialize ADCETRIS in the ALCANZA treatment setting would also limit our sales of, and the commercial potential of, ADCETRIS. In addition, while ADCETRIS product sales grew from 2014 to 2015 and from 2015 to 2016, and our future plans assume that sales of ADCETRIS will increase, we cannot assure you that ADCETRIS sales will continue to grow or that we can maintain sales of ADCETRIS at or near current levels.

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We and Takeda have formed a collaboration with Ventana Medical Systems, Inc., or Ventana, under which Ventana is working to develop, manufacture and commercialize a molecular companion diagnostic test with the goal of identifying patients who might respond to treatment with ADCETRIS based on CD30 expression levels in their tissue specimens. However, Ventana may not be able to successfully develop and obtain regulatory approval for a molecular companion diagnostic that may be required by regulatory authorities to support regulatory approval of ADCETRIS in other CD30-expressing malignancies in a timely manner or at all.

Even if we and Takeda receive the required regulatory approvals to market ADCETRIS for any additional indications or in additional jurisdictions, we and Takeda may not be able to effectively commercialize ADCETRIS, including for the reasons set forth above. Our ability to grow ADCETRIS product sales in future periods is also dependent on price increases and we periodically increase the price of ADCETRIS. Price increases on ADCETRIS and negative publicity regarding drug pricing and price increases generally, whether on ADCETRIS or products distributed by other pharmaceutical companies, could negatively affect market acceptance of, and sales of, ADCETRIS. In any event, we cannot assure you that price increases we have taken or may take in the future will not in the future negatively affect ADCETRIS sales.

Reports of adverse events or safety concerns involving ADCETRIS or our product candidates could delay or prevent us from obtaining or maintaining regulatory approvals, or could negatively impact sales of ADCETRIS or the prospects for our product candidates.

Reports of adverse events or safety concerns involving ADCETRIS could interrupt, delay or halt clinical trials of ADCETRIS, including the ongoing FDA-required ADCETRIS post-approval confirmatory study as well as the post-approval confirmatory studies that Takeda is required to conduct as a condition to the conditional marketing authorization of ADCETRIS by the European Commission. For example, during 2013 concerns regarding pancreatitis caused an investigator conducting an independent study involving ADCETRIS to temporarily halt enrollment in the trial and to amend the eligibility criteria and monitoring for the trial. Subsequently, we have revised our prescribing information to add pancreatitis as a known adverse event. In addition, reports of adverse events or safety concerns involving ADCETRIS could result in regulatory authorities denying or withdrawing approval of ADCETRIS for any or all indications, including the use of ADCETRIS for the treatment of patients in its approved indications. There are no assurances that patients receiving ADCETRIS will not experience serious adverse events in the future. Further, there are no assurances that patients receiving ADCETRIS with co-morbid diseases not previously studied, such as autoimmune diseases, will not experience new or different serious adverse events in the future.

Adverse events may negatively impact the sales of ADCETRIS. We may be required to further update the ADCETRIS prescribing information, including boxed warnings, based on reports of adverse events or safety concerns or implement a Risk Evaluation and Mitigation Strategy, or REMS, which could adversely affect ADCETRIS’ acceptance in the market, make competition easier or make it more difficult or expensive for us to distribute ADCETRIS. For example, the prescribing information for ADCETRIS includes pancreatitis, impaired hepatic function, impaired renal function, pulmonary toxicity, and gastrointestinal complications as known adverse events as well as a boxed warning related to the risk that JC virus infection resulting in progressive multifocal leukoencephalopathy, or PML, and death can occur in patients receiving ADCETRIS. Further, based on the identification of future adverse events, we may be required to further revise the prescribing information, including ADCETRIS’ boxed warning, which could negatively impact sales of ADCETRIS or adversely affect ADCETRIS’ acceptance in the market.

Likewise, reports of adverse events or safety concerns involving ADCETRIS or our product candidates could interrupt, delay or halt clinical trials of such product candidates, or could result in our inability to obtain regulatory approvals for any of our product candidates. For example, in December 2016, we announced that we had received notice from the FDA that a clinical hold had been placed on several early stage trials of SGN-CD33A in AML to evaluate the potential risk of hepatotoxicity following adverse medical events, including fatal events. In March 2017, we announced that the FDA had lifted the clinical hold and that we plan to resume two phase 1 trials of SGN-CD33A in AML and to initiate a randomized phase 2 trial during 2017 evaluating SGN-CD33A in combination with standard of care chemotherapy in frontline, younger AML patients. We also announced that we will not resume our phase 1/2 trial of SGN-CD33A monotherapy in pre- and post-allogeneic transplant AML patients given the challenges of developing therapies in that specific setting. Despite our ongoing and planned trials of SGN-CD33A, we cannot assure you that the FDA or another regulatory authority will not place an additional clinical hold on one or more of our trials of SGN-CD33A, including our ongoing phase 3 randomized CASCADE trial in frontline older AML patients. In addition, we have implemented additional risk mitigation measures in all SGN-CD33A studies, including certain stopping rules that could require us to suspend one or more trials of SGN-CD33A if certain safety events occur. Further, SGN-CD33A may face heightened regulatory scrutiny with regard to safety because other therapeutics that may be similar to SGN-CD33A have encountered challenges obtaining or maintaining regulatory approval due to safety concerns. If the FDA imposes a clinical hold on the CASCADE trial or one of our other trials of SGN-CD33A, or if there are additional safety results, including from our ongoing trials of SGN-CD33A, that result in the application of stopping rules, or alter the benefit-risk profile of SGN-CD33A or cause it to become unacceptable, we would be further delayed or prevented from advancing the clinical development of SGN-CD33A, which would adversely affect our business, results of operations and prospects.

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Concerns regarding the safety of ADCETRIS or our product candidates as a result of undesirable side effects identified during clinical testing or otherwise could cause the FDA to order us to cease further development or commercialization of ADCETRIS or the applicable product candidate. Undesirable side effects caused by ADCETRIS or our product candidates could also result in denial of regulatory approval by the FDA or other regulatory authorities for any or all targeted indications, the requirement of additional trials or the inclusion of unfavorable information in our product labeling, and in turn delay or prevent us from commercializing ADCETRIS or the applicable product candidate. In addition, actual or potential drug-related side effects could affect patient recruitment or the ability of enrolled patients to complete a trial for ADCETRIS or our product candidates or result in potential product liability claims. Any of these events could prevent us from developing or commercializing ADCETRIS or the particular product candidate, and could significantly harm our business, results of operations and prospects.

Even though we have obtained approval to market ADCETRIS in three indications, we are subject to extensive ongoing regulatory obligations and review, including post-approval requirements that could result in the withdrawal of ADCETRIS from the market for certain indications if such requirements are not met.

ADCETRIS is approved for treating patients in one indication, the relapsed sALCL indication, under accelerated approval regulations in the U.S. and approval with conditions in two indications in Canada, which allow for approval of products for cancer or other serious or life threatening illnesses based on a surrogate endpoint or on a clinical endpoint other than survival or irreversible morbidity. Under these types of approvals, we are subject to certain post-approval requirements pursuant to which we are conducting an additional confirmatory phase 3 trial to verify and describe the clinical benefit of ADCETRIS. Our failure to complete this required post-approval study, or to confirm a clinical benefit during this post-approval study, could result in the withdrawal of approval of ADCETRIS in the relapsed sALCL indication in the U.S. and both indications in Canada, which would seriously harm our business. In addition, under the FDA’s accelerated approval regulations, the labeling, packaging, adverse event reporting, storage, advertising and promotion of ADCETRIS for the treatment of patients with relapsed sALCL is subject to extensive regulatory requirements all of which entails significant expense and may limit our ability to commercialize ADCETRIS for the relapsed sALCL indication. Similarly, the conditional marketing authorization of ADCETRIS for two indications by the European Commission includes obligations to provide additional clinical data at a later time to confirm the results of the two pivotal studies. Takeda’s failure to provide these additional clinical data or to confirm the results of the pivotal studies, could result in the European Commission withdrawing approval of ADCETRIS in the European Union, which would negatively impact anticipated royalty revenue from ADCETRIS sales by Takeda in the European Union and could adversely affect our results of operations. In addition, we are subject to extensive ongoing obligations and continued regulatory review from applicable regulatory agencies with respect to any product for which we have obtained regulatory approval, including ADCETRIS in each of its approved indications, such as continued adverse event reporting requirements and the requirement to have some of our promotional materials pre-cleared by the FDA. There may also be additional post-marketing obligations, all of which may result in significant expense and limit our ability to commercialize ADCETRIS in the United States, Canada or potentially other jurisdictions.

We and the manufacturers of ADCETRIS are also required to comply with current Good Manufacturing Practices, or cGMP, regulations, which include requirements relating to quality control and quality assurance as well as the corresponding maintenance of records and documentation. Further, regulatory agencies must approve these manufacturing facilities before they can be used to manufacture ADCETRIS, and these facilities are subject to ongoing regulatory inspections. In addition, regulatory agencies subject an approved product, its manufacturer and the manufacturer’s facilities to continual review and inspections, including periodic unannounced inspections. The subsequent discovery of previously unknown problems with ADCETRIS, including adverse events of unanticipated severity or frequency, or problems with the facilities where ADCETRIS is manufactured, may result in restrictions on the marketing of ADCETRIS, up to and including withdrawal of ADCETRIS from the market. If our manufacturing facilities or those of our suppliers fail to comply with applicable regulatory requirements, such noncompliance could result in regulatory action and additional costs to us.

Failure to comply with applicable FDA and other regulatory requirements may subject us to administrative or judicially imposed sanctions, including:

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The policies of the FDA and other regulatory agencies may change and additional government regulations may be enacted that could prevent or delay regulatory approval of ADCETRIS in any additional indications or further restrict or regulate post-approval activities. We cannot predict the likelihood, nature or extent of adverse government regulation that may arise from future legislation or administrative action, either in the United States or abroad. If we are not able to maintain regulatory compliance, we or Takeda might not be permitted to market ADCETRIS and our business would suffer.

If we or our collaborators are not able to obtain or maintain required regulatory approvals, we or our collaborators will not be able to successfully commercialize ADCETRIS or our product candidates.

The research, testing, manufacturing, labeling, approval, selling, marketing and distribution of drug products are subject to extensive regulation by the FDA and other regulatory authorities in the United States and other countries, which regulations differ from country to country. Neither we nor our collaborators are permitted to market our product candidates in the United States or foreign countries until we obtain marketing approval from the FDA or other foreign regulatory authorities, and we or our collaborators may never receive regulatory approval for the commercial sale of any of our product candidates. In addition, part of our strategy is to continue to explore the use of ADCETRIS earlier in the treatment of Hodgkin lymphoma and MTCL and in other CD30-expressing malignancies, including CTCL, and we are currently conducting multiple clinical trials for ADCETRIS. However, we and/or Takeda may be unable to obtain or maintain any regulatory approvals for the commercial sale of ADCETRIS for any additional indications. Obtaining marketing approval is a lengthy, expensive and uncertain process and approval is never assured, and we have only limited experience in preparing and submitting the applications necessary to gain regulatory approvals. Further, the FDA and other foreign regulatory agencies have substantial discretion in the approval process, and determining when or whether regulatory approval will be obtained for any product candidate we develop, including any regulatory approvals for the potential commercial sale of ADCETRIS in additional indications or in any additional territories. In this regard, even if we believe the data collected from clinical trials of ADCETRIS and our product candidates are promising, such data may not be sufficient to support approval by the FDA or any other foreign regulatory authority. In addition, the FDA or their advisors may disagree with our interpretations of data from preclinical studies and clinical trials. In this regard, based on the positive data we reported from the ALCANZA trial, we plan to submit an sBLA to the FDA to seek approval for a new indication in CD30-expressing relapsed CTCL. Even if the FDA accepts our planned sBLA for filing, the FDA may disagree with our interpretations of the data from the ALCANZA trial and/or may otherwise determine not to approve our planned sBLA in a timely manner or at all. Moreover, even though our ALCANZA, ECHELON-1 and ECHELON-2 trials are being conducted under SPA agreements with the FDA, this is not a guarantee or indication of approval, and we cannot be certain that the design of, or data collected from, any of our current or potential future clinical trials that were or are being conducted under SPAs with the FDA will be sufficient to support FDA approval. Further, an SPA agreement is not binding on the FDA if public health concerns unrecognized at the time the SPA agreement is entered into become evident, other new scientific concerns regarding product safety or efficacy arise, new drugs are approved in the same indication, or if we have failed to comply with the agreed upon trial protocols, including as a result of completing a clinical trial with fewer events than planned. In addition, an SPA agreement may be changed by us or the FDA on written agreement of both parties, and the FDA retains significant latitude and discretion in interpreting the terms of an SPA agreement and the data and results from the applicable clinical trial. For example, even though we believe that the data from the ALCANZA trial are supportive of approval of ADCETRIS in the ALCANZA treatment setting, our SPA with the FDA covering the ALCANZA trial is not a guarantee or indication of approval of ADCETRIS in the ALCANZA treatment setting (or in any other indication). Regulatory agencies also may approve a product candidate for fewer indications than requested or may grant approval subject to the performance of post-approval studies or REMS for a product candidate. Similarly, regulatory agencies may not approve the labeling claims that are necessary or desirable for the successful commercialization of ADCETRIS in additional indications, including any indications in the ALCANZA treatment setting.

In addition, changes in regulatory requirements and guidance may occur and we may need to amend clinical trial protocols and/or related SPA agreements to reflect these changes. Amendments may require us to resubmit our clinical trial protocols to institutional review boards, or IRBs, for reexamination, which may impact the costs, timing or successful completion of a clinical trial. In addition, as part of the U.S. Prescription Drug User Fee Act, or PDUFA, the FDA has a goal to review and act on a percentage of all regulatory submissions in a given time frame. However, the FDA does not always meet its PDUFA targeted action dates and if the FDA were to fail to meet a PDUFA targeted action date in the future for ADCETRIS or any of our product candidates, including in connection with our planned sBLA submission to seek approval to market ADCETRIS in the ALCANZA treatment setting, the commercialization of the

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affected product candidate or of ADCETRIS in any additional indications could be delayed or impaired. Due to these and other factors, ADCETRIS and our product candidates could take a significantly longer time to gain regulatory approvals than we expect or may never gain new regulatory approvals, which could delay or eliminate any potential product revenue from sales of our product candidates or of ADCETRIS in any additional indications, which could significantly delay or prevent us from achieving profitability.

The successful commercialization of ADCETRIS and product candidates will depend in part on the extent to which governmental authorities and health insurers establish adequate coverage and reimbursement levels and pricing policies.

Successful sales of ADCETRIS and any future products will depend, in part, on the extent to which coverage and reimbursement for our products will be available from government and health administration authorities, private health insurers and other third-party payors. To manage healthcare costs, many governments and third-party payors increasingly scrutinize the pricing of new products and require greater levels of evidence of favorable clinical outcomes and cost-effectiveness before extending coverage. In light of such challenges to prices, we cannot be sure that we will achieve and continue to have coverage available for ADCETRIS and any other product candidate that we commercialize and, if available, that the reimbursement rates will be adequate. If we are unable to obtain adequate levels of coverage and reimbursement for our product candidates, their marketability will be negatively and materially impacted.

Moreover, eligibility for coverage and reimbursement does not imply that a drug will be paid for in all cases or at a rate that covers our costs, including research, development, manufacture, sale and distribution. In addition, obtaining and maintaining adequate coverage and reimbursement status is time-consuming and costly. Third-party payors may deny coverage and reimbursement status altogether of a given drug product, or cover the product but may also establish prices at levels that are too low to enable us to realize an appropriate return on our investment in product development. Further, one payor’s determination to provide coverage for a product does not assure that other payors will also provide coverage for the product. Because the rules and regulations regarding coverage and reimbursement change frequently, in some cases at short notice, even when there is favorable coverage and reimbursement, future changes may occur that adversely impact the favorable status.

The unavailability or inadequacy of third-party coverage and reimbursement could have a material adverse effect on the market acceptance of ADCETRIS and any of our future products and the future revenues we may expect to receive from those products. In addition, we are unable to predict what additional legislation or regulation relating to the healthcare industry or third-party coverage and reimbursement may be enacted in the future, or what effect such legislation or regulation would have on our business. Recent negative publicity regarding pharmaceutical prices and the results of the 2016 United States presidential and congressional elections create significant uncertainty regarding regulation of the healthcare industry and third party coverage and reimbursement.

Healthcare law and policy changes may have a material adverse effect on us.

In March 2010, the Patient Protection and Affordable Care Act of 2010, as amended by the Health Care and Education Reconciliation Act of 2010, or collectively PPACA, became law in the United States. PPACA substantially changed the way healthcare is financed by both governmental and private insurers and significantly affects the pharmaceutical industry. The provisions of PPACA of greatest importance to the pharmaceutical industry include increased Medicaid rebates, expanded Medicaid eligibility, extension of Public Health Service eligibility, annual fees payable by manufacturers and importers of branded prescription drugs, annual reporting of financial relationships with physicians and teaching hospitals, and a new Patient-Centered Outcomes Research Institute. Many of these provisions have had the effect of reducing the revenue generated by our sales of ADCETRIS and will have the effect of reducing any revenue generated by sales of any future commercial products we may have. Further, there have been judicial and Congressional challenges to certain aspects of PPACA. Further, on January 20, 2017, President Trump signed an Executive Order directing federal agencies with authorities and responsibilities under PPACA to waive, defer, grant exemptions from, or delay the implementation of any provision of PPACA that would impose a fiscal or regulatory burden on states, individuals, healthcare providers, health insurers, or manufacturers of pharmaceuticals or medical devices. Further, in March 2017, following the passage of the budget resolution for fiscal year 2017, the U.S. House of Representatives introduced legislation known as the American Health Care Act, or the AHCA, which, if enacted, would have amended or repealed significant portions of the PPACA. However, consensus over the scope of the AHCA could not be reached by its proponents in the U.S. House of Representatives. Thus, the AHCA has been withdrawn and the prospects for legislative action on the AHCA are uncertain. Congress could consider other legislation to repeal or replace elements of PPACA. Because of the continued uncertainty about the implementation of PPACA, including the potential for further legal challenges or repeal of PPACA, we cannot quantify or predict with any certainty the likely impact of the PPACA or its repeal on our business, prospects, financial condition or results of operations.

In addition, we anticipate that PPACA, as well as other healthcare reform measures that may be adopted in the future, may result in more rigorous coverage criteria and an additional downward pressure on the price that we receive for ADCETRIS or any future approved product, which may harm our business. For example, increased discounts, rebates or chargebacks may be mandated by governmental or private insurers or fee caps and pricing pressures could be enacted by industry organizations or state and federal governments, any of which could significantly affect the revenue generated by sales of our products, including ADCETRIS. In addition,

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drug- pricing by pharmaceutical companies has recently come under increased scrutiny. Specifically, there have been several recent U.S. Congressional inquiries and proposed federal and state legislation designed to, among other things, bring more transparency to drug pricing, reduce the out-of-pocket cost of prescription drugs, review the relationship between pricing and manufacturer patient programs and reform government program reimbursement methodologies for drugs. We expect further federal and state legislation and healthcare reforms to continue to be proposed to control increasing healthcare costs and to control the rising cost of prescription drugs. These proposals, if implemented, could limit the price for ADCETRIS or any future approved products. Commercial opportunity could be negatively impacted by legislative action that controls pricing, mandates price negotiations, or increases government discounts and rebates. For example, in March 2016, the Centers for Medicare and Medicaid Services, or CMS, proposed to conduct a demonstration project that would have reduced the Medicare payment rates for most Part B drugs for approximately half of all providers. The proposed rule was withdrawn in December 2016. However, if implemented, this project would have potentially limited our ability to change pricing for ADCETRIS and all drugs reimbursed under Medicare Part B. Any implementation of any future legislation could negatively impact future revenue from sales of ADCETRIS.

Also, price increases on ADCETRIS and negative publicity regarding drug pricing and price increases generally, whether on ADCETRIS or products distributed by other pharmaceutical companies, could negatively affect market acceptance of, and sales of, ADCETRIS. In addition, although ADCETRIS is approved in the European Union, Japan and other countries outside of the United States, government austerity measures or further healthcare reform measures and pricing pressures in other countries could adversely affect demand and pricing for ADCETRIS, which would negatively impact anticipated royalty revenue from ADCETRIS sales by Takeda.

Other legislative changes have also been proposed and adopted since PPACA was enacted. The Budget Control Act of 2011, among other things, created the Joint Select Committee on Deficit Reduction to recommend to Congress proposals in spending reductions. The Joint Select Committee did not achieve a targeted deficit reduction of at least $1.2 trillion for the years 2013 through 2021, triggering the legislation’s automatic reduction to several government programs. This includes a 2% reduction in Medicare provider payments paid under Medicare Part B to physicians for physician-administered drugs, such as certain oral oncology drugs, which went into effect in April 2013 and, following passage of the Bipartisan Budget Act of 2015, will remain in effect through 2025 unless additional congressional action is taken. The American Taxpayer Relief Act of 2012, among other things, reduced Medicare payments to several providers and increased the statute of limitations period for the government to recover overpayments to providers from three to five years. In addition, legislation has been proposed to shorten the period of biologic data and market exclusivity granted by the FDA. If such legislation is enacted, we may face competition from biosimilars of ADCETRIS or any future approved products earlier than otherwise would have occurred. Increased competition may negatively impact coverage and pricing of ADCETRIS, which could negatively affect our financial condition or results of operations.

We cannot predict what healthcare reform initiatives may be adopted in the future. However, we anticipate that Congress, state legislatures, and third-party payors may continue to review and assess alternative healthcare delivery and payment systems and may in the future propose and adopt legislation or policy changes or implementations effecting additional fundamental changes in the healthcare delivery system. We also expect ongoing initiatives to increase pressure on drug pricing. We cannot assure you as to the ultimate content, timing, or effect of changes, nor is it possible at this time to estimate the impact of any such potential legislation; however, such changes or the ultimate impact of changes could negatively affect our revenue or sales of ADCETRIS or any future approved products.

Enhanced governmental scrutiny, private litigation scrutiny and private litigation involving pharmaceutical manufacturer donations to patient assistance programs offered by charitable foundations may require us to modify our programs.

To help patients afford our products, we have a patient assistance program and also occasionally make donations to independent charitable foundations that help financially needy patients. These types of programs designed to assist patients afford pharmaceuticals have become the subject of scrutiny. In recent years, some pharmaceutical manufacturers were named in class action lawsuits challenging the legality of their patient assistance programs and support of independent charitable patient support foundations under a variety of federal and state laws. At least one insurer also has directed its network pharmacies to no longer accept manufacturer co-payment coupons for certain specialty drugs the insurer identified. Our patient assistance program and support of independent charitable foundations could become the target of similar litigation.

In addition, there has been regulatory review and enhance government scrutiny of donations by pharmaceutical companies to patient assistance programs operated by charitable foundations. For example, the Office of Inspector General of the U.S. Department of Health & Human Services, or OIG, has established specific guidelines permitting pharmaceutical manufacturers to make donations to charitable organizations who provide co-pay assistance to Medicare patients, provided that such organizations are bona fide charities, are entirely independent of and not controlled by the manufacturer, provide aid to applicants on a first-come basis according to consistent financial criteria, and do not link aid to use of a donor’s product. If we or our vendors or donation recipients are deemed to fail to

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comply with laws or regulations in the operation of these programs, we could be subject to damages, fines, penalties or other criminal, civil or administrative sanctions or enforcement actions. Further, numerous organizations, including pharmaceutical manufacturers, have received subpoenas from the OIG and other enforcement authorities seeking information related to their patient assistance programs and support. We cannot ensure that our compliance controls, policies and procedures will be sufficient to protect against acts of our employees, business partners or vendors that may violate the laws or regulations of the jurisdictions in which we operate. Regardless of whether we have complied with the law, a government investigation could impact our business practices, harm our reputation, divert the attention of management and increase our expenses.

Clinical trials are expensive and time consuming, may take longer than we expect or may not be completed at all, and their outcome is uncertain.

We are currently conducting multiple clinical trials for ADCETRIS and our product candidates and we plan to commence additional trials of ADCETRIS and our product candidates in the future. We are also conducting a phase 3 clinical trial for our product candidate SGN-CD33A, or the CASCADE trial, designed to evaluate SGN-CD33A in combination with hypomethylating agents, or HMAs, in previously untreated older AML patients. We initiated the CASCADE trial based on interim data presented at the December 2015 American Society of Hematology annual meeting from a cohort of a phase 1 trial that evaluated SGN-CD33A in combination with HMAs. While the interim phase 1 data may be promising, SGN-CD33A has not previously been evaluated in a randomized trial with other active agents and we cannot be certain that the design of, or data collected from, the CASCADE trial will be adequate to demonstrate the safety and efficacy of SGN-CD33A for the treatment of patients with AML, or will otherwise be sufficient to support FDA or any foreign regulatory approvals. In addition, as previously discussed, certain trials of SGN-CD33A were previously subject to a clinical hold, and the FDA may impose future holds on our clinical trials at any time, which may delay or prevent us from advancing the clinical development of SGN-CD33A or our other product candidates and may adversely affect our business, results of operations and prospects.

Each of our clinical trials requires the investment of substantial expense and time and the timing of the commencement, continuation and completion of these clinical trials may be subject to significant delays relating to various causes, including scheduling conflicts with participating clinicians and clinical institutions, difficulties in identifying and enrolling patients who meet trial eligibility criteria, failure of patients to complete the clinical trial, delays in accumulating the required number of clinical events for data analyses, delay or failure to obtain IRB approval to conduct a clinical trial at a prospective site, and shortages of available drug supply. For example, the SPA agreements for the ECHELON-1 and ECHELON-2 trials require that the trials continue until a specified number of events designated for each trial occur (i.e. progressions or deaths), and since we do not control the rate of events, the final data analysis for the applicable trial could be delayed beyond our expectations. In addition, until the final data analysis is completed for the applicable trial, we cannot be certain that the number of events designated in the applicable SPA agreement has actually occurred and if the designated number of events has not occurred, the FDA may treat the applicable SPA as rescinded and the statistical power of that trial based on the original statistical analysis plan could be negatively impacted, making it more difficult for us to demonstrate that ADCETRIS is safe and effective and to successfully obtain regulatory approval for the specific indication studied in that trial. We may also undertake additional discussions with regulatory authorities or amend the protocol for one or both of these trials, and we cannot predict the outcome of those discussions or whether we would be able to reach agreement with the regulatory authorities, which could result in a delay in our ability to conduct the final data analysis from the applicable trial or otherwise negatively impact the ability of the applicable trial to support approval of ADCETRIS for the specific indication studied in that trial.

Additionally, patient enrollment is a function of many factors, including the size of the patient population, the proximity of patients to clinical sites, the eligibility criteria for the trial, the existence of competing clinical trials, perceived side effects and the availability of alternative or new treatments. Many of our future and ongoing ADCETRIS clinical trials are being or will be coordinated with Takeda, which may delay the commencement or affect the continuation or completion of these trials. From time to time, we have experienced enrollment-related delays in clinical trials and we will likely continue to experience similar delays in our current and future trials. We depend on medical institutions and clinical research organizations, or CROs, to conduct some of our clinical trials in compliance with Good Clinical Practice, or GCP, and to the extent they fail to enroll patients for our clinical trials, fail to conduct our trials in accordance with GCP, or are delayed for a significant time in achieving full enrollment, we may be affected by increased costs, program delays or both, which may harm our business. In addition, we conduct clinical trials in foreign countries which may subject us to further delays and expenses as a result of increased drug shipment costs, additional regulatory requirements and the engagement of foreign CROs, as well as expose us to risks associated with less experienced clinical investigators who are unknown to the FDA, different standards of medical care, and foreign currency transactions insofar as changes in the relative value of the U.S. dollar to the foreign currency where the trial is being conducted may impact our actual costs.

Clinical trials must be conducted in accordance with FDA or other applicable foreign government guidelines and are subject to oversight by the FDA, other foreign governmental agencies, the data safety monitoring boards for such trials and the IRBs for the institutions in which such trials are being conducted. In addition, clinical trials must be conducted with supplies of ADCETRIS or our

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product candidates produced under cGMP and other requirements in foreign countries, and may require large numbers of test patients. We, the FDA, other foreign governmental agencies or the applicable data safety monitoring boards and IRBs could delay, suspend, halt or modify our clinical trials of ADCETRIS or any of our product candidates, and we and/or the FDA could terminate or modify any related SPA agreements, for numerous reasons, including:

Negative or inconclusive clinical trial results could adversely affect our ability to obtain regulatory approvals of our product candidates or to market ADCETRIS and/or expand ADCETRIS into other indications. In particular, negative or inconclusive results in our ECHELON-1 and ECHELON-2 trials would negatively impact or preclude altogether, our ability to obtain regulatory approval in the frontline Hodgkin lymphoma and frontline MTCL indications, respectively, either of which could limit our sales of, and the commercial potential of, ADCETRIS. In addition, clinical trial results are frequently susceptible to varying interpretations that may delay, limit or prevent regulatory approvals. For example, although we reported that our ALCANZA trial met its primary endpoint and we plan to submit an sBLA to the FDA to seek approval for a new indication in CD30-expressing relapsed CTCL, regulatory agencies, including the FDA, or their advisors, may disagree with our interpretations of data from the ALCANZA trial and may not approve the expansion of ADCETRIS’ labeled indications of use based on the results of the ALCANZA trial or any other of our clinical trials. Adverse medical events during a clinical trial, including patient fatalities, could cause a trial to be redone or terminated, curtail or end the development of a product candidate, and may result in other negative consequences to us. In addition, we may experience significant setbacks in advanced clinical trials, even after promising results in earlier trials, including unexpected adverse events that may occur when our product candidates are combined with other therapies. Further, some of our clinical trials, including the CASCADE trial, are overseen by an independent data monitoring committee, or IDMC, and an IDMC may determine to delay or suspend one or more of these trials due to safety or futility findings based on events occurring during a clinical trial. In addition, we may be required to

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implement additional risk mitigation measures that could require us to suspend our clinical trials if certain safety events occur. For example, we have agreed to implement stopping rules in all SGN-CD33A studies that could require us to suspend one or more trials if certain safety events occur during one or more clinical trials of SGN-CD33A.

We face intense competition and rapid technological change, which may result in others discovering, developing or commercializing competing products before or more successfully than we do.

The biotechnology and biopharmaceutical industries are characterized by rapidly advancing technologies, intense competition and a strong emphasis on proprietary products. Many third parties compete with us in developing various approaches to treating cancer. They include pharmaceutical companies, biotechnology companies, academic institutions and other research organizations.

Many of our competitors have significantly greater financial resources and expertise in research and development, manufacturing, preclinical testing, conducting clinical trials, obtaining regulatory approval and marketing than we do. In addition, many of these competitors are active in seeking patent protection and licensing arrangements in anticipation of collecting royalties for use of technology that they have developed. Smaller or early-stage companies may also prove to be significant competitors, particularly through collaborative arrangements with large and established companies. These third parties compete with us in recruiting and retaining qualified scientific and management personnel, as well as in acquiring technologies complementary to our programs.

With respect to ADCETRIS, there are several other FDA-approved drugs for the treatment of relapsed or refractory Hodgkin lymphoma or sALCL, including Bristol-Myers Squibb’s Opdivo , Celgene’s Istodax, Merck’s Keytruda, and Spectrum Pharmaceuticals’ Folotyn. Merck is also conducting a clinical trial in relapsed or refractory classical Hodgkin lymphoma comparing Keytruda (pembrolizumab) with ADCETRIS. In addition, we are aware of multiple investigational agents that are currently being studied, including Pfizer’s crizotinib, AbbVie’s ibrutinib, Kyowa’s mogamulizumab, and Gilead’s idelalisib, which, if successful, may compete with ADCETRIS in the future. Data have also been presented on several developing technologies, including bispecific antibodies and CAR modified T-cell therapies that may compete with ADCETRIS in the future. Further, there are many competing approaches used in the treatment of patients in ADCETRIS’ three approved indications, including auto-HSCT, conventional therapies, combination chemotherapy, clinical trials with experimental agents and single-agent regimens.

With respect to SGN-CD33A, there are several investigational agents that, if approved, could be competitive with our product candidate, including AbbVie’s venetoclax, which received breakthrough therapy designation from the FDA in 2016, Jazz Pharmaceutical’s Vyxeos, a new drug application for which has been submitted to the FDA in March 2017, Pfizer’s Mylotarg, Astex’s guadecitabine (SGI-110), and agents targeting biomarkers such as FLT3 and IDH1/2.

Many other pharmaceutical and biotechnology companies are developing and/or marketing therapies for the same types of cancer that our product candidates are designed and being developed to treat. For example, we believe that companies including AbbVie, ADC Therapeutics, Affimed, Agios, Amgen, Astellas, Bayer, Biogen, Bristol-Myers Squibb, Celgene, Eisai, Genentech, GSK, Gilead, ImmunoGen, Immunomedics, Infinity, Karyopharm, MedImmune, MEI Pharma, Merck, Novartis, Pfizer, Sanofi-Aventis, Spectrum Pharmaceuticals, Takeda, Teva, and Xencor are developing and/or marketing products or technologies that may compete with ours. In addition, our ADC collaborators may develop compounds utilizing our technology that may compete with product candidates that we are developing.

We are aware of other companies that have technologies that may be competitive with ours, including Astellas, AstraZeneca, Bristol-Myers Squibb, ImmunoGen, Immunomedics, MedImmune, Mersana and Pfizer, all of which have ADC technology. ImmunoGen has several ADCs in development that may compete with our product candidates. ImmunoGen has also established partnerships with other pharmaceutical and biotechnology companies to allow those other companies to utilize ImmunoGen’s technology, including Sanofi-Aventis, Genentech, Novartis, Takeda and Lilly. We are also aware of a number of companies developing monoclonal antibodies directed at the same antigen targets or for the treatment of the same diseases as our product candidates. For example, we believe Bristol-Myers Squibb has an anti-CD30 antibody program that may be competitive with ADCETRIS, and Amgen and Xencor have anti-CD19 programs that may be competitive with our product candidates.

In addition, in the United States, the Biologics Price Competition and Innovation Act of 2009 created an abbreviated approval pathway for biological products that are demonstrated to be “highly similar” or “biosimilar” to or “interchangeable” with an FDA-approved biological product. This pathway allows competitors to reference the FDA’s prior approvals regarding innovative biological products and data submitted with a BLA to obtain approval of a biosimilar application 12 years after the time of approval of the innovative biological product. The 12-year exclusivity period runs from the initial approval of the innovator product and not from approval of a new indication. In addition, the 12-year exclusivity period does not prevent another company from independently developing a product that is highly similar to the innovative product, generating all the data necessary for a full BLA and seeking approval. Exclusivity only assures that another company cannot rely on the FDA’s prior approvals in approving a BLA for an innovator’s biological product to support the biosimilar product’s approval. Further, under the FDA’s current interpretation, it is possible

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that a biosimilar applicant could obtain approval for one or more of the indications approved for the innovator product by extrapolating clinical data from one indication to support approval for other indications. The FDA approved the first biosimilar product in the United States in May 2015. In the European Union, the European Commission has granted marketing authorizations for several biosimilars pursuant to a set of general and product class-specific guidelines for biosimilar approvals issued since 2005. We are aware of many pharmaceutical and biotechnology and other companies that are actively engaged in research and development of biosimilars or interchangeable products.

It is possible that our competitors will succeed in developing technologies that are more effective than ADCETRIS, SGN-CD33A or our other product candidates or that would render our technology obsolete or noncompetitive, or will succeed in developing biosimilar or interchangeable products for ADCETRIS, SGN-CD33A or our other product candidates. We anticipate that we will face increased competition in the future as new companies enter our market and scientific developments surrounding biosimilars and other cancer therapies continue to accelerate. We cannot predict to what extent the entry of biosimilars or other competing products will impact potential future sales of ADCETRIS, SGN-CD33A or our other product candidates.

Our operating results are difficult to predict and may fluctuate. If our operating results are below the expectations of securities analysts or investors, the trading price of our stock could decline.

Our operating results are difficult to predict and may fluctuate significantly from quarter to quarter and year to year. In addition, although we provide sales guidance for ADCETRIS from time to time, you should not rely on ADCETRIS sales results in any period as being indicative of future performance. Such guidance is based on assumptions that may be incorrect or that may change from quarter to quarter. Sales of ADCETRIS have, on occasion, been below the expectations of securities analysts and investors and have been below prior period sales, and sales of ADCETRIS in the future may also be below prior period sales, our own guidance and/or the expectations of securities analysts and investors. To the extent that we do not meet our guidance or the expectations of analysts or investors, our stock price may be adversely impacted, perhaps significantly. We believe that our quarterly and annual results of operations may be affected by a variety of factors, including:

In addition, we have entered into licensing and collaboration agreements with other companies that include development funding and milestone payments to us, and we expect that amounts earned from our collaboration agreements will continue to be an important source of our revenues. Accordingly, our revenues will also depend on development funding and the achievement of development and clinical milestones under our existing collaboration and license agreements, including, in particular, our ADCETRIS collaboration with Takeda, as well as entering into potential new collaboration and license agreements. These upfront and milestone payments may vary significantly from quarter to quarter and any such variance could cause a significant fluctuation in our operating results from one quarter to the next.

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Further, changes in our operations, such as increased development, manufacturing and clinical trial expenses in connection with our expanding pipeline programs, including several phase 3 trials, or our undertaking of additional programs, business activities or entry into strategic transactions, including potential additional acquisitions of products, technologies or businesses may also cause significant fluctuations in our expenses. In addition, we measure compensation cost for stock-based awards made to employees at the grant date of the award, based on the fair value of the award, and recognize the cost as an expense over the employee’s requisite service period. As the variables that we use as a basis for valuing these awards change over time, including our underlying stock price, the magnitude of the expense that we must recognize may vary significantly. Additionally, we have implemented long-term incentive plans for our employees, and the incentives provided under these plans are contingent upon the achievement of certain regulatory milestones. Costs of performance-based compensation under our long-term incentive plans are not recorded as an expense until the achievement of the applicable milestones is deemed probable of being met, which may result in large fluctuations to the expense we must recognize in any particular period.

For these and other reasons, it is difficult for us to accurately forecast future sales of ADCETRIS, collaboration and license agreement revenues, royalty revenues, operating expenses or future profits or losses. As a result, our operating results in future periods could be below our guidance or the expectations of securities analysts or investors, which could cause the trading price of our common stock to decline, perhaps substantially.

We have a history of net losses. We expect to continue to incur net losses and may not achieve profitability for some time, if at all.

We have incurred substantial net losses in each of our years of operation. We have incurred these losses principally from costs incurred in our research and development programs and from our selling, general and administrative expenses. We expect to continue to spend substantial amounts on research and development, including amounts for conducting required post-approval and other clinical trials of, and seeking additional regulatory approvals for, ADCETRIS as well as commercializing ADCETRIS for the treatment of patients in its three approved indications. In addition, we expect to make substantial expenditures to further develop and potentially commercialize SGN-CD33A and our other product candidates. Likewise, if the Immunomedics transaction closes, we would incur substantial upfront and milestone payment obligations and expect to make substantial expenditures to potentially further develop and potentially commercialize IMMU-132. Accordingly, we expect to continue to incur net losses and may not achieve profitability for some time, if at all. Although we recognize revenue from ADCETRIS product sales and we continue to earn amounts under our collaboration agreements, our revenue and profit potential is unproven and our limited commercialization history makes our future operating results difficult to predict. Even if we do achieve profitability, we may not be able to sustain or increase profitability on a quarterly or annual basis. If we are unable to achieve and sustain profitability, the market value of our common stock will likely decline.

We depend on collaborative relationships with other companies to assist in the research and development of ADCETRIS and for the development and commercialization of product candidates utilizing or incorporating our technologies. If we are not able to locate suitable collaborators or if our collaborators do not perform as expected, this may negatively affect our ability to commercialize ADCETRIS, develop other product candidates and/or generate revenues through technology licensing, or may otherwise negatively affect our business.

We have established collaborations with third parties to develop and market ADCETRIS and some of our current and future product candidates. For example, we entered into a collaboration agreement with Takeda in December 2009 that granted Takeda rights to develop and commercialize ADCETRIS outside of the United States and Canada. In addition, we have entered into a 50/50 co-development agreement with Astellas for the development of ADCs, including ASG-22ME. We also have ADC collaborations with AbbVie, Bayer, Celldex, Genentech, GSK, Pfizer and Progenics, and an ADC co-development agreement with Genmab. In addition, we have entered into a collaboration agreement with Unum to develop and commercialize novel antibody-coupled T-cell receptor, or ACTR, therapies incorporating our antibodies for cancer. Our dependence on collaborative arrangements to assist in the development and commercialization of ADCETRIS and for the development and commercialization of product candidates utilizing or incorporating our technologies subjects us to a number of risks, including:

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If our collaborative or co-development arrangements are not successful as a result of any of the above factors, or any other factors, then our ability to advance the development and commercialization of the applicable products and product candidates and to otherwise generate revenue from these arrangements and to become profitable will be adversely affected, and our business and business prospects may be materially harmed. In particular, if Takeda were to terminate the ADCETRIS collaboration, we would not receive milestone payments, co-funded development payments or royalties for the sale of ADCETRIS outside the United States and Canada. As a result of such termination, we may have to engage another collaborator to complete the ADCETRIS development process and to commercialize ADCETRIS outside the United States and Canada, or to complete the development process and undertake commercializing ADCETRIS outside the United States and Canada ourselves, either of which could significantly delay the continued development and commercialization of ADCETRIS and increase our costs. In turn, this could significantly harm our financial position, adversely affect our stock price and require us to incur all the costs of developing and commercializing ADCETRIS, which are now being co-funded by Takeda.

In the future, we may not be able to locate third-party collaborators or co-development partners to develop and market products and product candidates utilizing or incorporating our technologies, and we may lack the capital and resources necessary to develop and market these products and product candidates alone.

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We have engaged in, and may in the future engage in strategic transactions that increase our capital requirements, dilute our stockholders, cause us to incur debt or assume contingent liabilities and subject us to other risks.

We actively evaluate various strategic transactions on an ongoing basis, including licensing or otherwise acquiring complementary products, technologies or businesses. Any potential acquisitions or in-licensing transactions, such as our potential in-licensing of IMMU-132, may entail numerous risks, including but not limited to:

As a result of these or other problems and risks, businesses, technologies or products we acquire or invest in or obtain licenses to may not produce the revenues, earnings or business synergies that we anticipated, acquired or licensed technologies may not result in regulatory approvals, and acquired or licensed products may not perform as expected. As a result, we may incur higher costs and realize lower revenues than we had anticipated. We cannot assure you that any acquisitions or investments we have made or may make in the future will be completed or that, if completed, the acquired business, licenses, investments, products, or technologies will generate sufficient revenue to offset the negative costs or other negative effects on our business. Failure to manage effectively our growth through acquisition or in-licensing transactions could adversely affect our growth prospects, business, results of operations, financial condition, and cash flow.

In addition, we may spend significant amounts, issue dilutive securities, assume or incur significant debt obligations, incur large one-time expenses and acquire intangible assets in connection with acquisitions and in-licensing transactions that could result in significant future amortization expense and write-offs. Moreover, we may not be able to locate suitable acquisition opportunities and this inability could impair our ability to grow or obtain access to technology or products that may be important to the development of our business. Even if appropriate opportunities are available, we may not be able to successfully identify them or we may not have the financial resources necessary to pursue them, and if pursued, we may be unable to structure and execute transactions in the anticipated timeframe, or at all. Other pharmaceutical companies, many of which may have substantially greater financial, marketing and sales resources, compete with us for these opportunities.

Even if we are able to successfully identify and acquire complementary products, technologies or businesses, we cannot assure you that we will be able to successfully manage the risks associated with integrating acquired products, technologies or businesses or the risks arising from anticipated and unanticipated problems in connection with an acquisition or in-licensing transaction. Further, while we seek to mitigate risks and liabilities of potential acquisitions and in-licensing transactions through, among other things, due diligence, there may be risks and liabilities that such due diligence efforts fail to discover, that are not disclosed to us, or that we inadequately assess. Any failure in identifying and managing these risks and uncertainties effectively would have a material adverse effect on our business. Additionally, we may not realize the anticipated benefits of such transactions, including the possibility that expected synergies and accretion will not be realized or will not be realized within the expected time frame.

Our current product candidates are in various stages of clinical development, and it is possible that none of these product candidates will ever become commercial products.

Our current product candidates are in various stages of clinical development, and other than SGN-CD33A, our product candidates are in relatively early stages of development. Our product candidates will require significant further development, financial resources and personnel to obtain regulatory approval and develop into commercially viable products, if at all. In 2016, we initiated the

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CASCADE trial, which is designed to evaluate SGN-CD33A in combination with HMAs in previously untreated older AML patients. SGN-CD33A has not previously been evaluated in a randomized trial with other active agents and we cannot be certain that the design of, or data collected from, the CASCADE trial will be adequate to demonstrate the safety and efficacy of SGN-CD33A for the treatment of patients with AML, or will otherwise be sufficient to support FDA or any foreign regulatory approvals.

Currently, our other clinical-stage product candidates include seven ADC programs, which consist of ASG-22ME, SGN-LIV1A, SGN-CD19A, SGN-CD19B, SGN-CD123A, SGN-352A, and ASG-15ME, as well as two immuno-oncology agents, SEA-CD40, which is based on our sugar-engineered antibody, or SEA, technology, and SGN-2FF, which is a novel small molecule. If a product candidate fails at any stage of development or we otherwise determine to discontinue development of that product candidate, we will not have the anticipated revenues from that product candidate to fund our operations, and we may not receive any return on our investment in that product candidate. Moreover, we still have only limited data from our phase 1 trials of our product candidates. In this regard, preclinical studies and any encouraging or positive preliminary and interim data from our clinical trials of our product candidates may not necessarily be predictive of the results of ongoing or later clinical trials. Even if we are able to complete our planned clinical trials of our product candidates according to our current development timeline, the encouraging or positive results from clinical trials of our product candidates in earlier stage trials may not be replicated in subsequent clinical trial results. As a result, we may conduct lengthy and expensive clinical trials of our product candidates only to learn that a product candidate is not an effective treatment or is not superior to existing approved therapies, or has an unacceptable safety profile, which could prevent or significantly delay regulatory approval for such product candidate. Also, our later-stage clinical trials could differ in significant ways from earlier stage clinical trials, which could cause the outcome of the later-stage trials to differ from our earlier stage clinical trials. For instance, though we reported phase 1 interim efficacy data that supported our decision to initiate the CASCADE trial, we may not receive positive results for SGN-CD33A even if we complete the CASCADE trial. Differences in earlier and later stage clinical trials may include changes to inclusion and exclusion criteria, efficacy endpoints and statistical design. Many companies in the pharmaceutical and biotechnology industries, including us, have suffered significant setbacks in late-stage clinical trials after achieving encouraging or positive results in early-stage development. We cannot be certain that we will not face similar setbacks in our ongoing clinical trials, for instance, in the CASCADE trial. We have not yet completed any late-stage clinical trials for our current product candidates, and if we fail to produce positive results in our ongoing or planned clinical trials of any of our product candidates, the development timeline and regulatory approval and commercialization prospects for our product candidates, and, correspondingly, our business and financial prospects, would be materially adversely affected.

Due to the uncertain and time-consuming clinical development and regulatory approval process, we may not successfully develop any of our product candidates and it is possible that none of our current product candidates will ever become commercial products. In addition, we expect that much of our effort and many of our expenditures over the next few years will be devoted to the additional clinical development of and commercialization activities associated with ADCETRIS, which may restrict or delay our ability to develop our clinical and preclinical product candidates.

To date, we have depended on a small number of collaborators for a substantial portion of our revenue. The loss of any one of these collaborators or changes in their product development or business strategy could result in a material decline in our revenue.

We have collaborations with a limited number of companies. To date, a substantial portion of our revenue has resulted from payments made under agreements with our corporate collaborators, and although ADCETRIS sales currently comprise a greater proportion of our revenue, we expect that a portion of our revenue will continue to come from corporate collaborations. Even though we market ADCETRIS in the United States and Canada, our revenues still depend in part on Takeda’s ability and willingness to market ADCETRIS outside of the United States and Canada. The loss of our collaborators, especially Takeda, changes in product development or business strategies of our collaborators, or the failure of our collaborators to perform their obligations under their agreements with us for any reason, including paying license or technology fees, milestone payments, royalties or reimbursements, could have a material adverse effect on our financial performance. Payments under our existing and potential future collaboration agreements are also subject to significant fluctuations in both timing and amount, which could cause our revenue to fall below the expectations of securities analysts and investors and cause a decrease in our stock price.

We are dependent upon a small number of distributors for a significant portion of our net sales, and the loss of, or significant reduction or cancellation in sales to, any one of these distributors could adversely affect our operations and financial condition.

In the United States and Canada, we sell ADCETRIS through a limited number of pharmaceutical distributors. Customers order ADCETRIS through these distributors. We generally receive orders from distributors and ship product directly to the customer. We do not promote ADCETRIS to these distributors and they do not set or determine demand for ADCETRIS; however, our ability to effectively commercialize ADCETRIS will depend, in part, on the performance of these distributors. Although we believe we can find alternative distributors on relatively short notice, the loss of a major distributor could materially and adversely affect our results of operations and financial condition.

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We currently rely on third-party manufacturers and other third parties for production of our drug products and our dependence on these manufacturers may impair the continued development and commercialization of ADCETRIS.

We do not currently have the internal ability to manufacture the drug products that we sell or need to conduct our clinical trials, and we therefore rely on corporate collaborators and contract manufacturing organizations to supply drug product for commercial supply and our IND-enabling studies and clinical trials. For the monoclonal antibody used in ADCETRIS, we have contracted with AbbVie for clinical and commercial supplies. For the drug linker used in ADCETRIS, we have contracted with Sigma Aldrich Fine Chemicals, or SAFC, for clinical and commercial supplies. We have multiple contract manufacturers for conjugating the drug linker to the antibody and producing the ADCETRIS product. For our ADC product candidates, multiple contract manufacturers, including AbbVie and SAFC, perform antibody and drug-linker manufacturing and several other contract manufacturers perform conjugation of the drug-linker to the antibody and fill/finish of the drug product. In addition, we rely on other third parties to perform additional steps in the manufacturing process, including shipping and storage of ADCETRIS and our product candidates. For the foreseeable future, we expect to continue to rely on contract manufacturers and other third parties to produce, vial and store sufficient quantities of ADCETRIS for use in our clinical trials and for commercial sale. If our contract manufacturers or other third parties fail to deliver ADCETRIS for clinical use or sale on a timely basis, with sufficient quality, and at commercially reasonable prices, and we fail to find replacement manufacturers or to develop our own manufacturing capabilities, we may be required to delay or suspend clinical trials or otherwise discontinue development, production and sale of ADCETRIS. Moreover, contract manufacturers have a limited number of facilities in which ADCETRIS can be produced and any interruption of the operation of those facilities due to events such as equipment malfunction or failure or damage to the facility by natural disasters or as the result of regulatory actions could result in the cancellation of shipments, loss of product in the manufacturing process, a shortfall in ADCETRIS supply, or the inability to sell our products in the U.S. or abroad. In addition, we have committed to provide Takeda with their needs of certain parts of the ADCETRIS supply chain for a limited period of time, which may require us to arrange for additional manufacturing supply. Moreover, we depend on outside vendors for the supply of raw materials used to produce ADCETRIS. If the third-party suppliers were to cease production or otherwise fail to supply us with quality raw materials and we were unable to contract on acceptable terms for these raw materials with alternative suppliers, our ability to have ADCETRIS manufactured to meet commercial and clinical requirements would be adversely affected.

We are subject to various state and federal laws and regulations, including healthcare laws and regulations, that may impact our business and could subject us to significant fines and penalties or other negative consequences.

Our operations may be directly or indirectly subject to various state and federal healthcare laws, including, without limitation, the federal Anti-Kickback Statute, federal civil and criminal false claims laws, HIPAA/HITECH, the federal civil monetary penalties statute, and the federal transparency requirements under the PPACA. These laws may impact, among other things, the sales, marketing and education programs for ADCETRIS.

The federal Anti-Kickback Statute prohibits persons and entities from knowingly and willingly soliciting, offering, receiving or providing remuneration, directly or indirectly, in exchange for or to induce either the referral of an individual, or the furnishing or arranging for a good or service, for which payment may be made under a federal healthcare program such as the Medicare and Medicaid programs. Several courts have interpreted the statute’s intent requirement to mean that if any one purpose of an arrangement involving remuneration is to induce referrals of federal healthcare covered business, the statute has been violated. Additionally, PPACA amended the intent requirement of the federal Anti-Kickback Statute such that a person or entity no longer needs to have actual knowledge of the statute or specific intent to violate it. The Anti-Kickback Statute is broad and prohibits many arrangements and practices that are lawful in businesses outside of the healthcare industry. Penalties for violations of the federal Anti-Kickback Statute include criminal penalties and civil sanctions such as fines, imprisonment and possible exclusion from Medicare, Medicaid and other federal healthcare programs.

The federal civil and criminal false claims laws, including the civil False Claims Act, prohibit, among other things, persons or entities from knowingly presenting, or causing to be presented, a false claim to, or the knowing use of false statements to obtain payment from or approval by the federal government, including the Medicare and Medicaid programs, or knowingly making, using, or causing to be made or used a false record or statement material to a false or fraudulent claim or to avoid, decrease, or conceal an obligation to pay money to the federal government. PPACA provides that the government may assert that a claim including items or services resulting from a violation of the federal Anti-Kickback Statute constitutes a false or fraudulent claim for purposes of the civil False Claims Act. Suits filed under the civil False Claims Act, known as “qui tam” actions, can be brought by any individual on behalf of the government and such individuals, commonly known as “whistleblowers,” may share in any amounts paid by the entity to the government in fines or settlement. Many pharmaceutical and other healthcare companies have recently been investigated or subject to lawsuits by whistleblowers and have reached substantial financial settlements with the federal government under the False Claims Act for a variety of alleged improper marketing or other activities, including providing free product to customers with the expectation that the customers would bill federal programs for the product; providing consulting fees, grants, free travel, and other benefits to physicians to induce them to prescribe the company’s products; and inflating prices reported to private price publication services, which are used to set drug reimbursement rates under government healthcare programs.

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The federal Health Insurance Portability and Accountability Act of 1996, or HIPAA, created additional federal criminal statutes that prohibit, among other things, knowingly and willfully executing, or attempting to execute, a scheme to defraud any healthcare benefit program, knowingly and willfully embezzling or stealing from a healthcare benefit program, willfully obstructing a criminal investigation of a healthcare offense, and knowingly and willfully falsifying, concealing, or covering up a material fact or making any materially false, fictitious, or fraudulent statement in connection with the delivery of or payment for healthcare benefits, items, or services. Similar to the Anti-Kickback Statute, PPACA amended the intent requirement of the criminal healthcare fraud statutes such that a person or entity no longer needs to have actual knowledge of the statute or intent to violate it.

HIPAA, as amended by the Health Information Technology for Economic and Clinical Health Act, or HITECH, and its implementing regulations, governs certain types of individuals and entities with respect to the conduct of certain electronic healthcare transactions and imposes certain obligations with respect to the security and privacy of protected health information.

The federal civil monetary penalties statute imposes penalties against any person or entity that, among other things, is determined to have presented or caused to be presented a claim to a federal health program that the person knows or should know is for an item or service that was not provided as claimed or is false or fraudulent.

The federal transparency requirements under PPACA, the Physician Payments Sunshine Act, require certain manufacturers of drugs, devices, biologics and medical supplies for which payment is available under Medicare, Medicaid, or the Children’s Health Insurance Program to annually report to the U.S. Department of Health and Human Services’ Centers for Medicare & Medicaid Services information related to payments and other transfers of value to physicians and teaching hospitals, and physician ownership and investment interests.

There are foreign and state law equivalents of these laws and regulations, such as anti-kickback, false claims, and data privacy and security laws, to which we are currently and/or may in the future, be subject. We may also be subject to state laws that require manufacturers to report information related to payments and other transfers of value to physicians and other healthcare providers or marketing expenditures. Many of these state laws differ from each other in significant ways, thus complicating compliance efforts.

The FDA and other governmental authorities also actively investigate allegations of off-label promotion activities in order to enforce regulations prohibiting these types of activities. In recent years, private whistleblowers have also pursued False Claims Act cases against a number of pharmaceutical companies for causing false claims to be submitted as a result of off-label promotion. If we are found to have promoted an approved product, including ADCETRIS, for off-label uses we may be subject to significant liability, including civil and administrative financial penalties and other remedies as well as criminal financial penalties and other sanctions. Even when a company is not determined to have engaged in off-label promotion, the allegation from government authorities or market participants that a company has engaged in such activities could have a significant impact on the company’s sales, business and financial condition. The U.S. government has also required companies to enter into complex corporate integrity agreements and/or non-prosecution agreements that impose significant reporting and other burdens on the affected companies.

We are also subject to numerous other laws and regulations that are not specific to the healthcare industry. For instance, the U.S. Foreign Corrupt Practices Act, or FCPA, prohibits companies and individuals from engaging in specified activities to obtain or retain business or to influence a person working in an official capacity. Under the FCPA, it is illegal to pay, offer to pay, or authorize the payment of anything of value to any foreign government official, governmental staff members, political party or political candidate in an attempt to obtain or retain business or to otherwise influence a person working in an official capacity. The FCPA also requires public companies to make and keep books and records that accurately and fairly reflect the transactions of the corporation and to devise and maintain an adequate system of internal accounting controls.

The number and complexity of both U.S. federal and state laws continue to increase. In addition to enforcement by governmental agencies, we also expect a continuation of the trend of private plaintiff lawsuits against pharmaceutical manufacturers under the whistleblower provisions of the False Claims Act and state equivalents or other laws and regulations such as securities rules and the evolution of new theories of liability under those statutes. Government agencies will likely continue to intervene in such private whistleblower lawsuits and such intervention typically raises the company’s cost significantly. For example, federal enforcement agencies have recently scrutinized product and patient assistance programs, including manufacturer reimbursement support services as well as relationships with specialty pharmacies. Several investigations have resulted in government enforcement authorities intervening in related whistleblower lawsuits and obtaining significant civil and criminal settlements.

In order to comply with these laws, we have implemented a comprehensive compliance program to actively identify, prevent and mitigate risk through the implementation of compliance policies and systems and by promoting a culture of compliance. Although we take our obligation to maintain our compliance with these various laws and regulations seriously and our compliance program is designed to prevent the violation of these laws and regulations, we cannot guarantee that our compliance program will be sufficient or effective, that our employees will comply with our policies and that our employees will notify us of any violation of our policies, that we will have the ability to take appropriate and timely corrective action in response to any such violation, or that we will make decisions

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and take actions that will necessarily limit or avoid liability for whistleblower claims that individuals, such as employees or former employees, may bring against us or that governmental authorities may prosecute against us based on information provided by individuals. If we are found to be in violation of any of the laws and regulations described above or other applicable state and federal healthcare laws, we may be subject to penalties, including civil and criminal penalties, damages, fines, disgorgement, contractual damages, reputational harm, imprisonment, diminished profits and future earnings, exclusion from government healthcare reimbursement programs, additional reporting requirements and oversight if we become subject to a corporate integrity agreement or similar agreement to resolve allegations of non-compliance with these laws, and/or the curtailment or restructuring of our operations, any of which could have a material adverse effect on our business, results of operations and growth prospects. Any action against us for violation of these laws or regulations, even if we successfully defend against it, could cause us to incur significant legal expenses and divert our management’s attention from the operation of our business. Moreover, achieving and sustaining compliance with applicable federal, state and foreign healthcare laws is costly and time-consuming for our management.

As we expand our operations internationally, we are subject to an increased risk of conducting activities in a manner that violates applicable anti-bribery or anti-corruption laws. We are also subject to foreign laws and regulations covering data privacy and the protection of health-related and other personal information. These laws and regulations could create liability for us or increase our cost of doing business, any of which could have a material adverse effect on our business, results of operations and growth prospects.

We are expanding our operations internationally, and we currently have subsidiaries in the U.K., Switzerland and Canada. Though we are at an early stage with our international expansion, our business activities outside of the United States are subject to the FCPA, which is described above, and similar anti-bribery or anti-corruption laws, regulations or rules of other countries in which we currently and may in the future operate, including the U.K. Bribery Act. The U.K. Bribery Act prohibits giving, offering, or promising bribes to any person, including non-U.K. government officials and private persons, as well as requesting, agreeing to receive, or accepting bribes from any person. In addition, under the U.K. Bribery Act, companies which carry on a business or part of a business in the U.K. may be held liable for bribes given, offered or promised to any person, including non-U.K. government officials and private persons, by employees and persons associated with such company in order to obtain or retain business or a business advantage for such company. In the course of expanding our operations internationally, we will need to establish and expand business relationships with various third parties, such as independent contractors, distributors, vendors, advocacy groups and physicians, and we will interact more frequently with foreign officials, including regulatory authorities and physicians employed by state-run healthcare institutions who may be deemed to be foreign officials under the FCPA, U.K. Bribery Act or similar laws of other countries that may govern our activities. Any interactions with any such parties or individuals where compensation is provided that are found to be in violation of such laws could result in substantial fines and penalties and could materially harm our business. Furthermore, any finding of a violation under one country’s laws may increase the likelihood that we will be prosecuted and be found to have violated another country’s laws. If our business practices outside the United States are found to be in violation of the FCPA, U.K. Bribery Act or other similar laws, we may be subject to significant civil and criminal penalties which could have a material adverse effect on our business, results of operations and growth prospects. We are also subject to foreign laws and regulations covering data privacy and the protection of health-related and other personal information. In this regard, European Union member states and other foreign jurisdictions, including Switzerland, have adopted data protection laws and regulations which impose significant compliance obligations. Failure to comply with these laws could lead to government enforcement actions and significant penalties against us, which could have a material adverse effect on our business, results of operations and growth prospects.

Any failures or further setbacks in our ADC development program would negatively affect our business and financial position.

ADCETRIS and our SGN-CD33A, ASG-22ME, SGN-LIV1A, SGN-CD19A, SGN-CD19B, SGN-CD123A, SGN-CD352A, and ASG-15ME product candidates are all based on our ADC technology, which utilizes proprietary stable linkers and potent cell-killing synthetic agents. Our ADC technology is also the basis of our collaborations with AbbVie, Astellas, Bayer, Celldex, Genentech, GSK, Pfizer, and Progenics, and our co-development agreements with Takeda, Astellas, and Genmab. Although ADCETRIS has received marketing approval in the United States, Canada, the European Union, Japan and other countries, ADCETRIS is our first and only ADC product that has been approved for commercial sale in any jurisdiction. Any failures or further setbacks in our ADC development program, including adverse effects resulting from the use of this technology in human clinical trials and/or the imposition of additional clinical holds on our trials of SGN-CD33A or any of our other product candidates, could have a detrimental impact on the continued commercialization of ADCETRIS in its current or any potential future approved indications and on our internal product candidate pipeline, as well as our ability to maintain and/or enter into new corporate collaborations regarding our ADC technology, which would negatively affect our business and financial position.

We have been named a defendant in a purported securities class action lawsuit, a stockholder derivative lawsuit, and a lawsuit in connection with the Immunomedics License. These, and potential similar or related lawsuits, could result in substantial damages and may divert management’s time and attention from our business.

On January 10, 2017, a purported securities class action lawsuit was commenced in the United States District Court for the Western District of Washington, naming as defendants us and certain of our officers. The lawsuit alleges material misrepresentations and

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omissions in public statements regarding our business, operational and compliance policies, violations by all named defendants of Section 10(b) of the Exchange Act, and Rule 10b-5 thereunder, as well as violations of Section 20(a) of the Exchange Act. The complaint seeks compensatory damages of an undisclosed amount. The plaintiff alleges, among other things, that we made false and/or misleading statements and/or failed to disclose that SGN-CD33A presents a significant risk of fatal hepatotoxicity and that we had therefore overstated the viability of SGN-CD33A as a treatment for AML. It is possible that additional suits will be filed, or allegations received from stockholders, with respect to these same matters and also naming us and/or our officers and directors as defendants. The court has not yet appointed a lead plaintiff or approved lead plaintiff’s counsel in this lawsuit.

On March 29, 2017, a stockholder derivative lawsuit was filed in Washington Superior Court for the County of Snohomish. The complaint names as defendants certain of our current and former executives and members of our board of directors. We are named as a nominal defendant. The complaint generally makes the same allegations as the securities class action, claiming that the individual defendants breached their duties to us. The complaint seeks unspecified damages, disgorgement of compensation, corporate governance changes, and attorneys’ fees and costs. Because the complaint is derivative in nature, it does not seek monetary damages from us. As a result of the lawsuit, we may incur litigation and indemnification expenses.

In addition, on February 13, 2017, we were named a co-defendant in a lawsuit filed by venBio in the Delaware Chancery Court, or the Court, against the members of the board of directors of Immunomedics. The venBio lawsuit alleges that the members of the Immunomedics board breached their fiduciary duties toward their stockholders by hastily licensing IMMU-132 to us. We are alleged to have aided and abetted the breach of fiduciary duties. Among other things, venBio seeks to enjoin the closing of the transactions contemplated by the Immunomedics License. On March 9, 2017, the Court issued a temporary restraining order enjoining taking any action in furtherance of the closing of the transactions contemplated by the Immunomedics License. The temporary restraining order will remain in place pending a trial on the merits currently scheduled for June 19, 2017. We cannot predict the outcome of the venBio lawsuit or the impact it may have on the Immunomedics License or the Stock Purchase Agreement, or the closing of the transactions contemplated by the Immunomedics License. However, it is possible that, in connection with the venBio lawsuit, the Immunomedics License or the Stock Purchase Agreement could be terminated, rescinded or reformed in a way that is disadvantageous to us, including a potential increase in the transaction consideration payable to Immunomedics under the Immunomedics License, or that otherwise adversely affects the anticipated benefits to us of the Immunomedics License.

These lawsuits and any other related lawsuits are subject to inherent uncertainties, and the actual costs to be incurred relating to the lawsuits will depend upon many unknown factors. The outcome of these lawsuits is necessarily uncertain, and we could be forced to expend significant resources in the defense of these lawsuits, and we may not prevail. Monitoring and defending against legal actions is time-consuming for our management and detracts from our ability to fully focus our internal resources on our business activities, which could result in delays of our clinical trials or our development and commercialization efforts. In addition, we may incur substantial legal fees and costs in connection with these lawsuits. We are also generally obligated, to the extent permitted by law, to indemnify our current and former directors and officers who are named as defendants in these and similar lawsuits. We are not currently able to estimate the possible cost to us from these matters, as these lawsuits are currently at an early stage and we cannot be certain how long it may take to resolve these matters or the possible amount of any damages that we may be required to pay. We have not established any reserves for any potential liability relating to these lawsuits. It is possible that we could, in the future, incur judgments or enter into settlements of claims for monetary damages. Decisions adverse to our interests in these lawsuits could result in the payment of substantial damages, or possibly fines, and could have a material adverse effect on our cash flow, results of operations and financial position. Decisions adverse to our interests in the venBio lawsuit could also result in the termination of the Immunomedics License or otherwise frustrate our ability to, or increase our costs to, consummate the transactions contemplated by the Immunomedics License. In addition, the uncertainty of the currently pending litigation could lead to increased volatility in our stock price.

We may need to raise significant amounts of additional capital that may not be available to us.

We expect to make additional capital outlays and to increase operating expenditures over the next several years as we hire additional employees, support our preclinical development, manufacturing and clinical trial activities for ADCETRIS and our other pipeline programs, and expand internationally, as well as commercialize ADCETRIS and position ADCETRIS for potential additional regulatory approvals. Our commitment of resources to the continuing development, regulatory and commercialization activities for ADCETRIS, and the research, continued development and manufacturing of our product candidates will likely require us to raise substantial amounts of additional capital. In addition, if the Immunomedics License transaction closes, we anticipate committing substantial capital resources to the transactions contemplated by the Immunomedics License and the anticipated transfer, integration and development activities related to IMMU-132, including with respect to our upfront and milestone payment obligations to Immunomedics. Further, we actively evaluate various strategic transactions on an ongoing basis, including licensing or otherwise acquiring complementary products, technologies or businesses, and we may require significant additional capital in order to complete or otherwise provide funding for any additional acquisitions. We may seek additional funding through some or all of the following

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methods: corporate collaborations, licensing arrangements and public or private debt or equity financings. We do not know whether additional capital will be available when needed, or that, if available, we will obtain financing on terms favorable to us or our stockholders. If we are unable to raise additional funds when we need them, we may be required to delay, reduce the scope of, or eliminate one or more of our development programs, which may adversely affect our business and operations. Our future capital requirements will depend upon a number of factors, including:

In addition, changes in our spending rate may occur that would consume available capital resources sooner, such as increased development, manufacturing and clinical trial expenses in connection with our expanding pipeline programs, including several phase 3 trials, or our undertaking of additional programs, business activities or entry into strategic transactions, including potential additional acquisitions of products, technologies or businesses. To the extent that we raise additional capital by issuing equity securities, our stockholders may experience substantial dilution. To the extent that we raise additional funds through collaboration and licensing arrangements, we may be required to relinquish some rights to our technologies or product candidates, or grant licenses on terms that are not favorable to us.

During the past several years, domestic and international financial markets have experienced extreme disruption from time to time, including, among other things, high volatility and significant declines in stock prices and severely diminished liquidity and credit availability for both borrowers and investors. For example, in June 2016, the electorate in the U.K. voted in favor of leaving the European Union (commonly referred to as “Brexit”). The withdrawal of the U.K. from the European Union will take effect either on the effective date of the withdrawal agreement or, in the absence of agreement, two years after the United Kingdom provides a notice of withdrawal pursuant to the EU Treaty. The U.K. government delivered a notice of withdrawal in March 2017. It is likely that the withdrawal of the U.K. from the European Union will involve a process of lengthy negotiations between the U.K and European Union member states to determine the future terms of the U.K.’s relationship with the European Union. This could lead to a period of considerable uncertainty, particularly in relation to global financial markets which in turn could adversely affect our ability to raise additional capital. Such adverse capital and credit market conditions could make it more difficult to obtain additional capital on favorable terms, or at all, which could have a material adverse effect on our business and growth prospects.

We rely on license agreements for certain aspects of ADCETRIS and our ADC technology. Failure to maintain these license agreements or to secure any required new licenses could prevent us from continuing to develop and commercialize ADCETRIS and our product candidates.

We have entered into agreements with third-party commercial and academic institutions to license technology for use in ADCETRIS and our ADC technology. Currently, we have license agreements with Bristol-Myers Squibb and the University of Miami, among others. In addition to royalty provisions, some of these license agreements contain diligence and milestone-based termination provisions, in which case our failure to meet any agreed upon royalty or diligence requirements or milestones may allow the licensor to terminate the agreement. Many of our license agreements grant us exclusive licenses to the underlying technologies. If our licensors terminate our license agreements or if we are unable to maintain the exclusivity of our exclusive license agreements, we may be unable to continue to develop and commercialize ADCETRIS or our product candidates. Further, we have had in the past, and may in the future

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have, disputes with our licensors, which may impact our ability to develop and commercialize ADCETRIS or our product candidates or require us to enter into additional licenses. An adverse result in potential future disputes with our licensors may impact our ability to develop and commercialize ADCETRIS and our product candidates, or may require us to enter into additional licenses or to incur additional costs in litigation or settlement. In addition, continued development and commercialization of ADCETRIS and our product candidates will likely require us to secure licenses to additional technologies. We may not be able to secure these licenses on commercially reasonable terms, if at all.

If we are unable to enforce our intellectual property rights or if we fail to sustain and further build our intellectual property rights, we may not be able to successfully commercialize ADCETRIS or future products and competitors may be able to develop competing therapies.

Our success depends, in part, on obtaining and maintaining patent protection and successfully enforcing these patents and defending them against third-party challenges in the United States and other countries. We own multiple U.S. and foreign patents and pending patent applications for our technologies. We also have rights to issued U.S. patents, patent applications, and their foreign counterparts, relating to our monoclonal antibody, linker and drug-based technologies. Our rights to these patents and patent applications are derived in part from worldwide licenses from third parties. In addition, we have licensed certain of our U.S. and foreign patents and patent applications to third parties.

The standards that the U.S. Patent and Trademark Office, or USPTO, and foreign patent offices use to grant patents are not always applied predictably or uniformly and can change. Consequently, our pending patent applications may not be allowed and, if allowed, may not contain the type and extent of patent claims that will be adequate to conduct our business as planned. Additionally, any issued patents we currently own or obtain in the future may have a shorter patent term than expected or may not contain claims that will permit us to stop competitors from using our technology or similar technology or from copying our products. Similarly, the standards that courts use to interpret patents are not always applied predictably or uniformly and may evolve, particularly as new technologies develop. In addition, changes to patent laws in the United States or other countries may be applied retroactively to affect the validation enforceability, or term of our patent. For example, the U.S. Supreme Court has recently modified some legal standards applied by the USPTO in examination of U.S. patent applications, which may decrease the likelihood that we will be able to obtain patents and may increase the likelihood of challenges to patents we obtain or license. In addition, changes to the U.S. patent system have come into force under the Leahy-Smith America Invents Act, or the America Invents Act, including changes from a “first-to-invent” system to a “first to file” system, changes to examination of U.S. patent applications and changes to the processes for challenging issued patents. These changes include provisions that affect the way patent applications are being filed, prosecuted and litigated. For example, the America Invents Act enacted proceedings involving post-issuance patent review procedures, such as inter partes review, or IPR, and post-grant review and covered business methods. These proceedings are conducted before the Patent Trial and Appeal Board, or PTAB, of the USPTO. Each proceeding has different eligibility criteria and different patentability challenges that can be raised. In this regard, the IPR process permits any person (except a party who has been litigating the patent for more than a year) to challenge the validity of some patents on the grounds that it was anticipated or made obvious by prior art. As a result, non-practicing entities associated with hedge funds, pharmaceutical companies who may be our competitors and others have challenged certain valuable pharmaceutical U.S. patents based on prior art through the IPR process. A decision in such a proceeding adverse to our interests could result in the loss of valuable patent rights which would have a material adverse effect on our business, financial condition, results of operations and growth prospects. In any event, the America Invents Act and any other potential future changes to the U.S. patent system could increase the uncertainties and costs surrounding the prosecution of our patent applications and the enforcement or defense of our issued patents, all of which could have a material adverse effect on our business, financial condition, results of operations and growth prospects.

We rely on trade secrets and other proprietary information where we believe patent protection is not appropriate or obtainable. However, trade secrets and other proprietary information are difficult to protect. We have taken measures to protect our unpatented trade secrets and know-how, including the use of confidentiality and assignment of inventions agreements with our employees, consultants and certain contractors. It is possible, however, that these persons may breach the agreements or that our competitors may independently develop or otherwise discover our trade secrets or other proprietary information. Our research collaborators may publish confidential data or other restricted information to which we have rights. If we cannot maintain the confidentiality of our technology and other confidential information in connection with our collaborations, then our ability to receive patent protection or protect our proprietary information may be impaired.

We may incur substantial costs and lose important rights or may not be able to continue to commercialize ADCETRIS or to commercialize any of our product candidates that may be approved for commercial sale as a result of litigation or other proceedings relating to patent and other intellectual property rights, and we may be required to obtain patent and other intellectual property rights from others.

We may face potential lawsuits by companies, academic institutions or others alleging infringement of their intellectual property. Because patent applications can take a few years to publish, there may be currently pending applications of which we are unaware that may later result in issued patents that adversely affect the continued commercialization of ADCETRIS or future commercialization of

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our product candidates in development. In addition, we are monitoring the progress of multiple pending patent applications of other organizations that, if granted, may require us to license or challenge their enforceability in order to continue commercializing ADCETRIS or to commercialize our product candidates that may be approved for commercial sale. Our challenges to patents of other organizations may not be successful, which may affect our ability to commercialize ADCETRIS or our product candidates. As a result of the patent infringement lawsuits that have been filed or may be filed against us in the future by third parties alleging infringement by us of patent or other intellectual property rights, we may be required to pay substantial damages, including lost profits, royalties, treble damages, attorneys’ fees and costs, for past infringement if it is ultimately determined that our products infringe a third party’s intellectual property rights. Even if infringement claims against us are without merit, the results may be unpredictable. In addition, defending lawsuits takes significant time, may be expensive and may divert management’s attention from other business concerns. Further, we may be stopped from developing, manufacturing or selling our products until we obtain a license from the owner of the relevant technology or other intellectual property rights, or be forced to undertake costly design-arounds, if feasible. If such a license is available at all, it may require us to pay substantial royalties or other fees.

We are or may be from time to time involved in the defense and enforcement of our patent or other intellectual property rights in a court of law, USPTO interference, IPR, post-grant review or reexamination proceeding, foreign opposition proceeding or related legal and administrative proceeding in the United States and elsewhere. In addition, if we choose to go to court to stop a third party from infringing our patents, that third party has the right to ask the court to rule that these patents are invalid, not infringed and/or should not be enforced. Under the America Invents Act, a third party may also have the option to challenge the validity of certain patents at the PTAB, whether they are accused of infringing our patents or not, and certain entities associated with hedge funds, pharmaceutical companies and other entities have challenged valuable pharmaceutical patents through the IPR process. These lawsuits and administrative proceedings are expensive and consume time and other resources, and we may not be successful in these proceedings or in stopping infringement. In addition, there is a risk that a court will decide that these patents are not valid or not infringed or otherwise not enforceable, or that the PTAB will decide that certain patents are not valid or should have a shorter term, and that we do not have the right to stop a third party from using the patented subject matter. Successful challenges to our patent or other intellectual property rights through these proceedings could result in a loss of rights in the relevant jurisdiction and may allow third parties to use our proprietary technologies without a license from us or our collaborators, which may also result in loss of future royalty payments. Furthermore, if such challenges to our rights are not resolved promptly in our favor, our existing business relationships may be jeopardized and we could be delayed or prevented from entering into new collaborations or from commercializing potential products, which could adversely affect our business and results of operations. In addition, we may challenge the patent or other intellectual property rights of third parties and if we are unsuccessful in actions we bring against the rights of such parties, through litigation or otherwise, and it is determined that we infringe the intellectual property rights of such parties, we may be prevented from commercializing potential products in the relevant jurisdiction, or may be required to obtain licenses to those rights or develop or obtain alternative technologies, any of which could harm our business.

If we lose our key personnel or are unable to attract and retain additional qualified personnel, our future growth and ability to compete would suffer.

We are highly dependent on the efforts and abilities of the principal members of our senior management. Additionally, we have scientific personnel with significant and unique expertise in monoclonal antibodies, ADCs and related technologies. The loss of the services of any one of the principal members of our managerial or scientific staff may prevent us from achieving our business objectives.

In addition, the competition for qualified personnel in the biotechnology field is intense, and our future success depends upon our ability to attract, retain and motivate highly skilled scientific, technical and managerial employees. In order to commercialize ADCETRIS, we have been required to expand our workforce, particularly in the areas of manufacturing, clinical trials management, regulatory affairs, business development, sales and marketing. These activities required the addition of new personnel, including sales and marketing management, and the development of additional expertise by existing management personnel. We continue to face intense competition for qualified individuals from numerous pharmaceutical and biotechnology companies, as well as academic and other research institutions. To the extent we are not able to retain these individuals on favorable terms or attract any additional personnel that may be required, our business may be harmed.

If we are unable to manage our growth, our business, financial condition, results of operations and prospects may be adversely affected.

We have experienced and expect to continue to experience significant growth in the number of our employees and in the scope of our operations. This growth places significant demands on our management, operational and financial resources, and our current and planned personnel, systems, procedures and controls may not be adequate to support our growth. To effectively manage our growth, we must continue to improve existing, and implement new, operational and financial systems, procedures and controls and must expand, train and manage our growing employee base, and there can be no assurance that we will effectively manage our growth without experiencing operating inefficiencies or control deficiencies. We expect that we may need to increase our management personnel to oversee our expanding operations, and recruiting and retaining qualified individuals is difficult. In addition, the physical expansion of

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our operations may lead to significant costs and may divert our management and capital resources. If we are unable to manage our growth effectively, or are unsuccessful in recruiting qualified management personnel, our business, financial condition, results of operations and prospects may be adversely affected.

Product liability and product recalls could harm our business, and we may not be able to obtain adequate insurance to protect us against product liability losses.

The current and future use of ADCETRIS by us and our corporate collaborators in clinical trials and the sale of ADCETRIS, expose us to product liability claims. These claims have and may in the future be made directly by consumers or healthcare providers or indirectly by pharmaceutical companies, our corporate collaborators or others selling such products. We may experience substantial financial losses in the future due to product liability claims. We have obtained product liability coverage, including coverage for human clinical trials and product sold commercially. However, we may not be able to maintain insurance coverage at a reasonable cost or in sufficient amounts to protect us against all losses. If a successful product liability claim or series of claims is brought against us for uninsured liabilities or in excess of insured amounts, our assets may not be sufficient to cover such claims and our business operations could be impaired.

Product recalls may be issued at our discretion, or at the discretion of government agencies and other entities that have regulatory authority for pharmaceutical sales. Any recall of ADCETRIS could materially adversely affect our business by rendering us unable to sell ADCETRIS for some time and by adversely affecting our reputation.

Risks associated with operating in foreign countries could materially adversely affect our business.

We are expanding our operations internationally, and we currently have subsidiaries in the U.K., Switzerland and Canada. Consequently, we are, and will continue to be, subject to risks related to operating in foreign countries. Risks associated with conducting operations in foreign countries include:

For example, since a significant proportion of the regulatory framework in the U.K. is derived from European Union directives and regulations, Brexit could materially change the regulatory regime applicable to our operations and those of our collaborators, including with respect to marketing authorizations for ADCETRIS and our product candidates. We may also face new regulatory costs and challenges as result of Brexit that could have a material adverse effect on our operations. Depending on the terms of Brexit, the U.K. could lose the benefits of global trade agreements negotiated by the European Union on behalf of its members, which may result in increased trade barriers which could make our doing business in Europe more difficult. In addition, currency exchange rates for the British Pound and the Euro with respect to each other and the U.S. dollar have already been affected by Brexit. Should this foreign exchange volatility continue, it could cause volatility in our quarterly financial results. In any event, we cannot predict to what extent these changes will impact our business or results of operations, or our ability to conduct operations in Europe.

These and other risks described elsewhere in these risk factors associated with expanding our international operations could materially adversely affect our business.

Our operations involve hazardous materials and are subject to environmental, health and safety controls and regulations.

We are subject to environmental, health and safety laws and regulations, including those governing the use of hazardous materials, and we spend considerable time complying with such laws and regulations. Our business activities involve the controlled use of

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hazardous materials and although we take precautions to prevent accidental contamination or injury from these materials, we cannot completely eliminate the risk of using these materials. In the event of an accident or environmental discharge, we may be held liable for any resulting damages, which may materially harm our business, financial condition and results of operations.

If any of our facilities are damaged or our clinical, research and development or other business processes are interrupted, our business could be seriously harmed.

We conduct most of our business in a limited number of facilities in a single geographical location in Bothell, Washington. Damage or extended periods of interruption to our corporate, development or research facilities due to fire, natural disaster, power loss, communications failure, unauthorized entry or other events could cause us to cease or delay development of some or all of our product candidates or interrupt the sales process for ADCETRIS. Although we maintain property damage and business interruption insurance coverage on these facilities, our insurance might not cover all losses under such circumstances and our business may be seriously harmed by such delays and interruption.

If we experience a significant disruption in our information technology systems or breaches of data security, our business could be adversely affected.

We rely on information technology systems to keep financial records, capture laboratory data, maintain clinical trial data and corporate records, communicate with staff and external parties and operate other critical functions. Our information technology systems are potentially vulnerable to disruption due to breakdown, malicious intrusion and computer viruses or other disruptive events including but not limited to natural disaster. If we were to experience a prolonged system disruption in our information technology systems or those of certain of our vendors, it could delay or negatively impact the development and commercialization of ADCETRIS and our product candidates, which could adversely impact our business. Although we maintain offsite back-ups of our data, if operations at our facilities were disrupted, it may cause a material disruption in our business if we are not capable of restoring function on an acceptable timeframe. In addition, our information technology systems are potentially vulnerable to data security breaches—whether by employees or others—which may expose sensitive data to unauthorized persons. Such data security breaches could lead to the loss of trade secrets or other intellectual property, or could lead to the public exposure of personal information (including sensitive personal information) of our employees, customers and others, any of which could have a material adverse effect on our business, financial condition and results of operations. Moreover, a security breach or privacy violation that leads to disclosure or modification of, personally identifiable information, could harm our reputation, compel us to comply with federal and/or state breach notification laws, subject us to mandatory corrective action, require us to verify the correctness of database contents and otherwise subject us to liability under laws and regulations that protect personal data, resulting in increased costs or loss of revenue. In addition, a data security breach could result in loss of clinical trial data or damage to the integrity of that data. If we are unable to prevent such security breaches or privacy violations or implement satisfactory remedial measures, our operations could be disrupted, and we may suffer loss of reputation, financial loss and other negative consequences because of lost or misappropriated information. In addition, these breaches and other inappropriate access can be difficult to detect, and any delay in identifying them may lead to increased harm of the type described above.

Increasing use of social media could give rise to liability.

We are increasingly relying on social media tools as a means of communications. To the extent that we continue to use these tools as a means to communicate about ADCETRIS and our product candidates or about the diseases that ADCETRIS and our product candidates are intended to treat, there are significant uncertainties as to either the rules that apply to such communications, or as to the interpretations that health authorities will apply to the rules that exist. As a result, despite our efforts to comply with applicable rules, there is a significant risk that our use of social media for such purposes may cause us to nonetheless be found in violation of them. Such uses of social media could have a material adverse effect on our business, financial condition and results of operations.

Legislative actions and new accounting pronouncements are likely to impact our future financial position or results of operations.

Future changes in financial accounting standards may cause adverse, unexpected revenue fluctuations and affect our financial position or results of operations. New pronouncements and varying interpretations of pronouncements have occurred with frequency in the past and are expected to occur again in the future and as a result we may be required to make changes in our accounting policies. Those changes could adversely affect our reported revenues and expenses, future profitability or financial position. Compliance with new regulations regarding corporate governance and public disclosure may result in additional expenses.

For example, in May 2014, the Financial Accounting Standards Board, or FASB, issued an Accounting Standards Update entitled “ASU 2014-09, Revenue from Contracts with Customers” which will replace the existing revenue recognition guidance in U.S. GAAP when it becomes effective for us on January 1, 2018. Our preliminary assessment of this new standard is that it will generally not change the way in which we recognize product revenue from sales of ADCETRIS. However, we expect that sales-based royalties and commercial sales-based milestones will be recorded in the period of the related sale based on estimates, rather than recording them as reported by the customer. In addition, the achievement of development milestones under our collaborations will be recorded in the period their achievement becomes probable, which may result in their recognition earlier than under current accounting principles. We are continuing to evaluate the impact of the

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new standard on all of our revenues, including those mentioned above, and our assessments may change in the future based on our continuing evaluation. In any event, the application of existing or future financial accounting standards, particularly those relating to the way we account for revenues and costs, could have a significant impact on our reported results. In addition, compliance with new regulations regarding corporate governance and public disclosure may result in additional expenses. As a result, we intend to invest all reasonably necessary resources to comply with evolving standards, and this investment may result in increased general and administrative expenses and a diversion of management time and attention from science and business activities to compliance activities.

Risks Related to the Immunomedics License

Failure to consummate the transactions contemplated by the Immunomedics License could negatively impact our stock price and our future business and financial results.

We announced on February 10, 2017 that we had entered into the Immunomedics License pursuant to which, upon the terms and subject to the conditions set forth in the Immunomedics License, we would receive exclusive worldwide rights to develop and commercialize IMMU-132. On February 13, 2017, we were named a co-defendant in a lawsuit filed by venBio in the Delaware Chancery Court against the members of the board of directors of Immunomedics, pursuant to which, among other things, venBio sought to enjoin the closing of the transactions contemplated by the Immunomedics License. On March 9, 2017, the Delaware Chancery Court issued a temporary restraining order enjoining taking any action in furtherance of the closing of the transactions contemplated by the Immunomedics License. The temporary restraining order will remain in place pending a trial on the merits scheduled for June 19, 2017. We cannot predict the outcome of the venBio lawsuit or the impact it may have on the Immunomedics License, the Stock Purchase Agreement, or the closing of the transactions contemplated by the Immunomedics License. However, in connection with the venBio lawsuit, the Immunomedics License or the Stock Purchase Agreement could be terminated, rescinded or reformed in a way that is disadvantageous to us, including a potential increase in the transaction consideration payable to Immunomedics to obtain rights to IMMU-132, or that otherwise adversely affects the anticipated benefits to us of the transaction with Immunomedics. If the transactions contemplated by the Immunomedics License are not consummated, our ongoing business may be adversely affected and, without realizing any of the benefits of having consummated the transactions contemplated by the Immunomedics License, we will be subject to a number of risks, including the following:

We also could be subject to additional litigation related to any failure to consummate the transactions contemplated by the Immunomedics License or to perform our obligations under the Immunomedics License. If the transactions contemplated by the Immunomedics License are not consummated, these risks may materialize and may adversely affect our business, financial results and stock price.

If the transactions contemplated by the Immunomedics License are consummated, we may not be able to successfully integrate IMMU-132 or any other potential future product candidates we may acquire or license rights to, or we may otherwise fail to realize their full potential.

We actively evaluate various strategic transactions on an ongoing basis, including licensing or otherwise acquiring complementary products, technologies or businesses, and in February 2017, we announced our entry into the Immunomedics License with Immunomedics pursuant to which, if consummated, we would be granted an exclusive worldwide license to IMMU-132. However, even if the transactions contemplated by the Immunomedics License are consummated, we cannot ensure that we would be able to manage the risks associated with the transfer of development, regulatory and manufacturing activities for IMMU-132 from Immunomedics to us or manage the risks associated with integrating IMMU-132 into our existing business and infrastructure. We may encounter unexpected difficulties during the transfer, integration or further development of IMMU-132, any of which may cause us to expend greater funds and efforts or may slow, delay or limit the progress of IMMU-132’s development. Unexpected difficulties may further be disruptive to our ongoing development and commercialization efforts, put a strain on our existing personnel, infrastructure and business and divert management’s time and attention. As a result of these or other problems and risks, even if the transactions contemplated by the Immunomedics License are consummated, we may never receive regulatory approval for IMMU-132, we may not realize the full potential of IMMU-132 or we may never generate significant value or revenues from IMMU-132.

In addition, the market price of our common stock may decline if the integration or further development of IMMU-132 is unsuccessful, takes longer than expected or fails to result in benefits to the extent anticipated by financial analysts or investors, or the effect of our license of IMMU-132 on our financial position and results of operations is otherwise not consistent with the expectations of financial analysts or investors.

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Risks Related to Our Common Stock

Our stock price is volatile and our shares may suffer a decline in value.

The market price of our stock has in the past been, and is likely to continue in the future to be, very volatile. During the first quarter ended March 31, 2017, our closing stock price fluctuated between $53.00 and $68.91 per share. As a result of fluctuations in the price of our common stock, you may be unable to sell your shares at or above the price you paid for them. The market price of our common stock may be subject to substantial volatility in response to many risk factors listed in this section, and others beyond our control, including:

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The stock markets in general, and the markets for biotechnology and pharmaceutical stocks in particular, have historically experienced significant volatility that has often been unrelated or disproportionate to the operating performance of particular companies. For example, negative publicity regarding drug pricing and price increases by pharmaceutical companies has negatively impacted, and may continue to negatively impact, the markets for biotechnology and pharmaceutical stocks. Likewise, as a result of Brexit and/or significant changes in U.S. social, political, regulatory and economic conditions or in laws and policies governing foreign trade and health care spending and delivery, including the potential repeal and/or replacement of all or portions of PPACA or greater restrictions on free trade stemming from Trump Administration policies, the financial markets could experience significant volatility that could also negatively impact the markets for biotechnology and pharmaceutical stocks. These broad market fluctuations have adversely affected and may in the future adversely affect the trading price of our common stock.

In the past, class action or derivative litigation has often been instituted against companies whose securities have experienced periods of volatility in market price. In this regard, we have become, and may in the future again become, subject to claims and litigation alleging violations of the securities laws or other related claims, which could harm our business and require us to incur significant costs. The pending purported securities class action lawsuit and any additional lawsuits brought against us could result in substantial costs, which would hurt our financial condition and results of operations and divert management’s attention and resources, which could result in delays of our clinical trials or our development and commercialization efforts.

Substantial future sales of shares of our common stock or equity-related securities could cause the market price of our common stock to decline.

Sales of a substantial number of shares of our common stock into the public market, including sales by members of our management or board of directors or entities affiliated with such members, could occur at any time. These sales, or the perception in the market that the holders of a large number of shares intend to sell shares, could reduce the market price of our common stock and could impair our ability to raise capital through the sale of additional equity or equity-related securities. We are unable to predict the effect that such sales may have on the prevailing market price of our common stock. As of April 26, 2017, we had 142,716,597 shares of common stock outstanding, all of which shares are eligible for sale in the public market, subject in some cases to the volume limitations and manner of sale and other requirements under Rule 144. In addition, we may issue a substantial number of shares of our common stock or equity- related securities, including convertible debt, to meet our capital needs, including in connection with funding acquisition or licensing opportunities, capital expenditures or product development costs, which issuances could be substantially dilutive and could adversely affect the market price of our common stock. Likewise, future issuances by us of our common stock upon the exercise, conversion or settlement of equity-based awards or other equity-related securities would dilute existing stockholders’ ownership interest in our company and any sales in the public market of these shares, or the perception that these sales might occur, could also adversely affect the market price of our common stock.

Moreover, we have in the past and may in the future grant rights to some of our stockholders that require us to register the resale of our common stock or other securities on behalf of these stockholders and/or facilitate public offerings of our securities held by these stockholders, including in connection with potential future acquisition or capital-raising transactions. For example, in connection with our September 2015 public offering of common stock, we entered into a registration rights agreement with entities affiliated with Baker Bros. Advisors LP, or the Baker Entities, that together, based on information available to us, collectively beneficially owned approximately 32.3% of our common stock as of April 26, 2017. Under the registration rights agreement, if at any time and from time to time the Baker Entities demand that we register their shares of our common stock for resale under the Securities Act of 1933, we would be obligated to effect such registration. On October 12, 2016, pursuant to the registration rights agreement, we registered for resale, from time to time, up to 44,059,594 shares of our common stock held by the Baker Entities. Our registration obligations under the registration rights agreement cover all shares now held or hereafter acquired by the Baker Entities, will continue in effect for up to ten years, and include our obligation to facilitate certain underwritten public offerings of our common stock by the Baker Entities in the future. If the Baker Entities, by its exercise of these registration and/or underwriting rights in the future, or otherwise, sell a large number of our shares, or the market perceives that the Baker Entities intend to sell a large number of our shares, including in connection with our October 2016 registration of shares held by the Baker Entities for resale, this could adversely affect the market price of our common stock. We have also filed registration statements to register the sale of our common stock reserved for issuance under our equity incentive and employee stock purchase plans. Accordingly, these shares will be able to be freely sold in the public market upon issuance as permitted by any applicable vesting requirements.

Our existing stockholders have significant control of our management and affairs.

Our executive officers and directors and holders of greater than five percent of our outstanding voting stock, together with entities that may be deemed affiliates of, or related to, such persons or entities, beneficially owned approximately 68.2% of our voting power as of April 26, 2017. As a result, these stockholders, acting together, are able to control our management and affairs and matters requiring stockholder approval, including the election of directors and approval of significant corporate transactions, such as mergers, consolidations or the sale of substantially all of our assets. Consequently, this concentration of ownership may have the effect of

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delaying, deferring or preventing a change in control, including a merger, consolidation, takeover or other business combination involving us or discourage a potential acquirer from making a tender offer or otherwise attempting to obtain control, which might affect the market price of our common stock.

Anti-takeover provisions could make it more difficult for a third party to acquire us.

Our Board of Directors has the authority to issue up to 5,000,000 shares of preferred stock and to determine the price, rights, preferences, privileges and restrictions, including voting rights, of those shares without any further vote or action by the stockholders, which authority could be used to adopt a “poison pill” that could act to prevent a change of control of Seattle Genetics that has not been approved by our Board of Directors. The rights of the holders of common stock may be subject to, and may be adversely affected by, the rights of the holders of any preferred stock that may be issued in the future. The issuance of preferred stock may have the effect of delaying, deferring or preventing a change of control of Seattle Genetics without further action by the stockholders and may adversely affect the voting and other rights of the holders of common stock. Further, certain provisions of our charter documents, including provisions eliminating the ability of stockholders to take action by written consent and limiting the ability of stockholders to raise matters at a meeting of stockholders without giving advance notice, may have the effect of delaying or preventing changes in control or management of Seattle Genetics, which could have an adverse effect on the market price of our stock. In addition, our charter documents provide for a classified board, which may make it more difficult for a third party to gain control of our Board of Directors. Similarly, state anti-takeover laws in Delaware and Washington related to corporate takeovers may prevent or delay a change of control of Seattle Genetics.

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SIGNATURES

Pursuant to the requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

Date: May 1, 2017

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EXHIBIT INDEX

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