bluebird bio, Inc. - Quarter Report: 2018 March (Form 10-Q)

!

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, DC 20549

FORM 10-Q

(Mark One)

For the quarterly period ended March 31, 2018

OR

For the transition period from                     to                    

Commission File Number: 001-35966

bluebird bio, Inc.

(Exact Name of Registrant as Specified in Its Charter)

(339) 499-9300

(Registrant’s Telephone Number, Including Area Code)

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, or a smaller reporting 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. (Check one):

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 27, 2018, there were 50,119,272 shares of the registrant’s Common Stock, par value $0.01 per share, outstanding.  

This Quarterly Report on Form 10-Q contains forward-looking statements that involve risks and uncertainties, as well as assumptions that, if they never materialize or prove incorrect, could cause our results to differ materially from those expressed or implied by such forward-looking statements. We make such forward-looking statements pursuant to the safe harbor provisions of the Private Securities Litigation Reform Act of 1995 and other federal securities laws. All statements other than statements of historical facts contained in this Quarterly Report on Form 10-Q are forward-looking statements. In some cases, you can identify forward-looking statements by words such as “anticipate,” “believe,” “contemplate,” “continue,” “could,” “estimate,” “expect,” “intend,” “may,” “plan,” “potential,” “predict,” “project,” “seek,” “should,” “target,” “would,” or the negative of these words or other comparable terminology. These forward-looking statements include, but are not limited to, statements about:

Any forward-looking statements in this Quarterly Report on Form 10-Q reflect our current views with respect to future events or to our future financial performance and involve known and unknown risks, uncertainties and other factors that may cause our actual results, performance or achievements to be materially different from any future results, performance or achievements expressed or implied by these forward-looking statements. Factors that may cause actual results to differ materially from current expectations include, among other things, those listed under Part II, Item 1A. Risk Factors and elsewhere in this Quarterly Report on Form 10-Q. Given these uncertainties, you should not place undue reliance on these forward-looking statements. Except as required by law, we assume no obligation to update or revise these forward-looking statements for any reason, even if new information becomes available in the future.

This Quarterly Report on Form 10-Q also contains estimates, projections and other information concerning our industry, our business, and the markets for certain diseases, including data regarding the estimated size of those markets, and the incidence and prevalence of certain medical conditions. Information that is based on estimates, forecasts, projections, market research or similar methodologies is inherently subject to uncertainties and actual events or circumstances may differ materially from events and circumstances reflected in this information. Unless otherwise expressly stated, we obtained this industry, business, market and other data from reports, research surveys, studies and similar data prepared by market research firms and other third parties, industry, medical and general publications, government data and similar sources.

bluebird bio, Inc.

Table of Contents

PART I. FINANCIAL INFORMATION

Item 1. Financial Statements

bluebird bio, Inc.

Condensed Consolidated Balance Sheets

(unaudited)

(in thousands, except par value amounts)

See accompanying notes to unaudited condensed consolidated financial statements.

2

bluebird bio, Inc.

Condensed Consolidated Statements of Operations and Comprehensive Loss

(unaudited)

(in thousands, except per share data)

See accompanying notes to unaudited condensed consolidated financial statements.

3

bluebird bio, Inc.

Condensed Consolidated Statements of Cash Flows

(unaudited)

(in thousands)

See accompanying notes to unaudited condensed consolidated financial statements.

4

bluebird bio, Inc.

Notes to Condensed Consolidated Financial Statements

(unaudited)

1. Description of the business

bluebird bio, Inc. (the “Company” or “bluebird”) was incorporated in Delaware on April 16, 1992, and is headquartered in Cambridge, Massachusetts. The Company researches, develops, manufactures and plans to commercialize gene therapies for the treatment of severe genetic diseases and cancer. Since its inception, the Company has devoted substantially all of its resources to its research and development efforts relating to its product candidates, including activities to manufacture product candidates, conduct clinical studies of its product candidates, perform preclinical research to identify new product candidates and provide general and administrative support for these operations.

The Company’s clinical programs in severe genetic diseases include its LentiGlobin^® product candidate to treat transfusion-dependent β-thalassemia, or TDT, and to treat severe sickle cell disease, or severe SCD, and its Lenti-D^TM product candidate to treat cerebral adrenoleukodystrophy, or CALD, a rare hereditary neurological disorder. The Company’s programs in oncology are built upon its leadership in lentiviral gene delivery and T cell engineering, with a focus on developing novel T cell-based immunotherapies, including chimeric antigen receptor (CAR) and T cell receptor (TCR) T cell therapies. bb2121 and bb21217, which are product candidates in oncology under the Company’s collaboration arrangement with Celgene Corporation (“Celgene”), are CAR T cell product candidates for the treatment of multiple myeloma. Refer to Note 8, “Collaboration revenue” for further discussion of the Company’s collaboration with Celgene.

As of March 31, 2018, the Company had cash, cash equivalents and marketable securities of $1.57 billion. Although the Company has incurred recurring losses and expects to continue to incur losses for the foreseeable future, the Company expects that its cash, cash equivalents and marketable securities will be sufficient to fund current operations for at least the next twelve months.  

2. Basis of presentation, principles of consolidation and significant accounting policies

Basis of presentation

The accompanying condensed consolidated financial statements are unaudited and have been prepared by the Company in accordance with accounting principles generally accepted in the United States (“GAAP”) as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Update (“ASU”) of the Financial Accounting Standards Board (“FASB”). Certain information and footnote disclosures normally included in the Company’s annual financial statements have been condensed or omitted. These interim condensed consolidated financial statements, in the opinion of management, reflect all normal recurring adjustments necessary for a fair presentation of the Company’s financial position and results of operations for the interim periods ended March 31, 2018 and 2017.

The results of operations for the interim periods are not necessarily indicative of the results of operations to be expected for the full year. These interim financial statements should be read in conjunction with the audited financial statements as of and for the year ended December 31, 2017, and the notes thereto, which are included in the Company’s Annual Report on Form 10-K filed with the Securities and Exchange Commission (the “SEC”) on February 21, 2018.

Certain items in the prior year’s condensed consolidated financial statements have been reclassified to conform to the current presentation.  As a result, no subtotals in the prior year condensed consolidated financial statements were impacted.

Amounts reported are computed based on thousands. As a result, certain totals may not sum due to rounding.

Principles of consolidation

The accompanying condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. As of March 31, 2018, there have been no changes to the Company’s subsidiary listing, which is included as an exhibit to its Annual Report on Form 10-K for the year ended December 31, 2017.  All intercompany balances and transactions have been eliminated in consolidation. Any reference in these notes to applicable guidance is meant to refer to GAAP. The Company views its operations and manages its business in one operating segment. All material long-lived assets of the Company reside in the United States.

5

Significant accounting policies

The significant accounting policies used in preparation of these condensed consolidated financial statements for the three months ended March 31, 2018 are consistent with those discussed in Note 2 to the consolidated financial statements in the Company’s 2017 Annual Report on Form 10-K, except as noted below with respect to the Company’s revenue recognition, collaboration revenue and license and royalty revenue accounting policies and as noted within the “Recent accounting pronouncements – Recently adopted” section below.  

Revenue recognition

Effective January 1, 2018, the Company adopted Accounting Standards Codification (“ASC”), Topic 606, Revenue from Contracts with Customers (“Topic 606”), using the modified retrospective transition method. Under this method, the Company has recognized the cumulative effect of the adoption as an adjustment to the opening balance of accumulated deficit in the current period condensed consolidated balance sheet.  The Company has not revised its consolidated financial statements for prior periods. This standard applies to all contracts with customers, except for contracts that are within the scope of other standards, such as collaboration arrangements and leases.

Under Topic 606, an entity recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration that the entity expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements that an entity determines are within the scope of Topic 606, the entity performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price, including variable consideration, if any; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the entity satisfies a performance obligation. The Company only applies the five-step model to contracts when it is probable that the entity will collect the consideration to which it is entitled in exchange for the goods or services it transfers to the customer.

Once a contract is determined to be within the scope of Topic 606, the Company assesses the goods or services promised within each contract and determines those that are performance obligations.  Arrangements that include rights to additional goods or services that are exercisable at a customer’s discretion are generally considered options.  The Company assesses if these options provide a material right to the customer and if so, they are considered performance obligations.  The exercise of a material right is accounted for as a contract modification for accounting purposes.

The Company assesses whether each promised good or service is distinct for the purpose of identifying the performance obligations in the contract. This assessment involves subjective determinations and requires management to make judgments about the individual promised goods or services and whether such are separable from the other aspects of the contractual relationship. Promised goods and services are considered distinct provided that: (i) the customer can benefit from the good or service either on its own or together with other resources that are readily available to the customer (that is, the good or service is capable of being distinct) and (ii) the entity’s promise to transfer the good or service to the customer is separately identifiable from other promises in the contract (that is, the promise to transfer the good or service is distinct within the context of the contract).  In assessing whether a promised good or service is distinct, the Company considers factors such as the research, manufacturing and commercialization capabilities of the collaboration partner and the availability of the associated expertise in the general marketplace. The Company also considers the intended benefit of the contract in assessing whether a promised good or service is separately identifiable from other promises in the contract. If a promised good or service is not distinct, an entity is required to combine that good or service with other promised goods or services until it identifies a bundle of goods or services that is distinct.

The transaction price is then determined and allocated to the identified performance obligations in proportion to their standalone selling prices (“SSP”) on a relative SSP basis. SSP is determined at contract inception and is not updated to reflect changes between contract inception and when the performance obligations are satisfied. Determining the SSP for performance obligations requires significant judgment. In developing the SSP for a performance obligation, the Company considers applicable market conditions and relevant entity-specific factors, including factors that were contemplated in negotiating the agreement with the customer and estimated costs. The Company validates the SSP for performance obligations by evaluating whether changes in the key assumptions used to determine the SSP will have a significant effect on the allocation of arrangement consideration between multiple performance obligations.

If the consideration promised in a contract includes a variable amount, the Company estimates the amount of consideration to which it will be entitled in exchange for transferring the promised goods or services to a customer. The Company determines the amount of variable consideration by using the expected value method or the most likely amount method. The Company includes the unconstrained amount of estimated variable consideration in the transaction price. The amount included in the transaction price is constrained to the amount for which it is probable that a significant reversal of cumulative revenue recognized will not occur. At the

6

end of each subsequent reporting period, the Company re-evaluates the estimated variable consideration included in the transaction price and any related constraint, and if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis in the period of adjustment.

If an arrangement includes development and regulatory milestone payments, the Company evaluates whether the milestones are considered probable of being reached and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant revenue reversal would not occur, the associated milestone value is included in the transaction price. Milestone payments that are not within the Company’s control or the licensee’s control, such as regulatory approvals, are generally not considered probable of being achieved until those approvals are received.

In determining the transaction price, the Company adjusts consideration for the effects of the time value of money if the timing of payments provides the Company with a significant benefit of financing.  The Company does not assess whether a contract has a significant financing component if the expectation at contract inception is such that the period between payment by the licensees and the transfer of the promised goods or services to the licensees will be one year or less.  The Company assessed each of its revenue generating arrangements in order to determine whether a significant financing component exists and concluded that a significant financing component does not exist in any of its arrangements.

The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) each performance obligation is satisfied at a point in time or over time, and if over time this is based on the use of an output or input method.

Collaboration revenue

To date, the Company’s collaboration revenue has been exclusively generated from its collaboration arrangement with Celgene, which was originally entered into in March 2013 and was subsequently amended in June 2015, as further described in Note 8, “Collaboration revenue”.

The Company analyzes its collaboration arrangements to assess whether they are within the scope of ASC 808, Collaborative Arrangements (“ASC 808”) to determine whether such arrangements involve joint operating activities performed by parties that are both active participants in the activities and exposed to significant risks and rewards dependent on the commercial success of such activities.  This assessment is performed throughout the life of the arrangement based on changes in the responsibilities of all parties in the arrangement.  For collaboration arrangements within the scope of ASC 808 that contain multiple elements, the Company first determines which elements of the collaboration are deemed to be within the scope of ASC 808 and those that are more reflective of a vendor-customer relationship and therefore within the scope of Topic 606. For elements of collaboration arrangements that are accounted for pursuant to ASC 808, an appropriate recognition method is determined and applied consistently, generally by analogy to Topic 606.  Amounts that are owed to collaboration partners are recognized as an offset to collaboration revenues as such amounts are incurred by the collaboration partner.  Where amounts owed to a collaboration partner exceed the Company’s collaboration revenues in each quarterly period, such amounts are classified as research and development expense. For those elements of the arrangement that are accounted for pursuant to Topic 606, the Company applies the five-step model described above.

License and royalty revenue

The Company enters into out-licensing agreements that are within the scope of Topic 606. The Company does not have any material license arrangements that contain more than one performance obligation. The terms of such out-license agreements include the license of functional intellectual property, given the functionality of the intellectual property is not expected to change substantially as a result of the licensor’s ongoing activities, and typically include payment of one or more of the following: non-refundable up-front license fees; development, regulatory and milestone payments based on the level of sales; and royalties on net sales of licensed products. Nonrefundable up-front license fees are recognized as revenue at a point in time when the licensed intellectual property is made available for the customer’s use and benefit, which is generally at the inception of the arrangement.  Milestone fees, which are a type of variable consideration, are recognized as revenue to the extent that it is probable that a significant reversal will not occur. For arrangements with licenses of intellectual property that include sales-based royalties, including milestone payments based on the level of sales, and the license is deemed to be the predominant item to which the royalties relate, the Company recognizes royalty revenue and sales-based milestones at the later of (i) when the related sales occur, or (ii) when the performance obligation to which the royalty has been allocated has been satisfied.

For a complete discussion of accounting for collaboration and other revenue-generating arrangements, see Note 8, “Collaboration revenue” and Note 9, “License and royalty revenue”.  Additionally, see “Recent accounting pronouncements - Recently adopted” below for discussion of the impact of adopting Topic 606, which was effective on January 1, 2018.

7

Use of estimates

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts in the financial statements and accompanying notes. Actual results could materially differ from those estimates. Management considers many factors in selecting appropriate financial accounting policies and controls, and in developing the estimates and assumptions that are used in the preparation of these financial statements. Management must apply significant judgment in this process. In addition, other factors may affect estimates, including: expected business and operational changes, sensitivity and volatility associated with the assumptions used in developing estimates, and whether historical trends are expected to be representative of future trends. The estimation process often may yield a range of potentially reasonable estimates of the ultimate future outcomes and management must select an amount that falls within that range of reasonable estimates. This process may result in actual results differing materially from those estimated amounts used in the preparation of the financial statements. Estimates are used in the following areas, among others: subsequent fair value estimates used to assess potential impairment of long-lived assets, including goodwill and intangible assets, financing lease obligation, contingent consideration, stock-based compensation expense, accrued expenses, revenue and income taxes.

Recent accounting pronouncements

Recently adopted

ASU No. 2014-09, Revenue from Contracts with Customers

In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers, which superseded the revenue recognition requirements in ASC 605, Revenue Recognition and created a new Topic 606, Revenue from Contracts with Customers.  In 2015 and 2016, the FASB issued additional ASUs related to Topic 606 that delayed the effective date of the guidance and clarified various aspects of the new revenue guidance.  The new standard became effective on January 1, 2018.  Topic 606 allows for either a full retrospective adoption, in which the standard is applied to all periods presented in an entity’s financial statements, or a modified retrospective approach, in which the standard is applied to the most current period presented in an entity’s financial statements with the cumulative effect of adoption recognized as an adjustment to the opening balance of accumulated deficit in the period of adoption. The Company adopted this new standard on January 1, 2018 using the modified retrospective approach, which has been applied consistently to all contracts, and has elected to use the following practical expedient that is permitted under the rules of adoption:

As a result of adopting Topic 606, the Company recorded a $29.4 million adjustment to the opening balance of accumulated deficit in the first quarter of 2018 primarily as a result of the treatment of the up-front consideration received in March 2013 under ASC 605-25 versus Topic 606.  Refer below for a summary of the amount by which each financial statement line item was affected by the impact of the cumulative adjustment:

The amount by which each financial statement line item is affected in the current reporting period by Topic 606 as compared with the guidance that was in effect prior to adoption is disclosed below.

8

The most significant change above relates to the Company’s collaboration revenue, which to date has been exclusively generated from its collaboration arrangement with Celgene. Under ASC 605, the Company accounted for contract modifications to the Celgene collaboration as they occurred and the accounting for those changes was prospective in nature.  Through the application of the practical expedient discussed above in connection with the adoption of Topic 606, the Company reflected the aggregate effect of all modifications to the Celgene collaboration when identifying the satisfied and unsatisfied performance obligations, determining the transaction price, and allocating the transaction price. As a result, although the performance obligations identified under Topic 606 were generally consistent with the units of account identified under ASC 605, the timing of the allocation of the transaction price to the identified performance obligations under Topic 606 differed from the allocations of consideration under ASC 605. Accordingly, the transaction price ultimately allocated to each performance obligation under Topic 606 differed from the amounts allocated under ASC 605.

As a result of adopting Topic 606, the Company established a deferred revenue deferred tax asset, and an offsetting valuation allowance, of $7.9 million through its accumulated deficit given it is not more likely than not that the deferred tax asset will be realized due to historical and expected future losses, such that there was no tax impact on the Company’s condensed consolidated financial statements as a result of adopting Topic 606.

ASU 2016-15, Statement of Cash Flows: Classification of Certain Cash Receipts and Cash Payments

In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows: Classification of Certain Cash Receipts and Cash Payments (“Topic 230”). The new standard clarifies certain aspects of the statement of cash flows, including the classification of contingent consideration payments made after a business combination and several other clarifications not currently applicable to the Company. The new standard also clarifies that an entity should determine each separately identifiable source or use within the cash receipts and cash payments on the basis of the nature of the underlying cash flows. In situations in which cash receipts and payments have aspects of more than one class of cash flows and cannot be separated by source or use, the appropriate classification should depend on the activity that is likely to be the predominant source or use of cash flows for the item. The new standard was effective for the Company on January 1, 2018. The adoption of this standard did not have a material impact on the Company’s condensed consolidated statements of cash flows upon adoption.

9

ASU 2016-18, Statement of Cash Flows: Restricted Cash

In November 2016, the FASB issued ASU 2016-18, Statement of Cash Flows: Restricted Cash (“ASU 2016-18”). The amendments in this update require that amounts generally described as restricted cash and restricted cash equivalents be included within cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. ASU 2016-18 was effective January 1, 2018.  As a result of adopting ASU 2016-18, the Company includes its restricted cash balance in the cash and cash equivalents reconciliation of operating, investing and financing activities.  The following table provides a reconciliation of cash, cash equivalents, and restricted cash within the statement of financial position that sum to the total of the same such amounts shown in the statement of cash flows.

ASU 2017-09, Compensation – Stock Compensation (Topic 718): Scope Modification Accounting

In May 2017, the FASB issued ASU 2017-09, Compensation – Stock Compensation (Topic 718): Scope Modification Accounting.  The new standard is intended to reduce the diversity in practice and cost and complexity when applying the guidance in Topic 718 to a change to the terms or conditions of a share-based payment award.  The new standard was effective beginning January 1, 2018. The adoption of this standard did not have a material impact on the Company’s financial position or results of operations upon adoption.      

Not yet adopted

ASU 2016-02, Leases

In February 2016, the FASB issued ASU 2016-02, Leases, (“ASU 2016-02”), which requires a lessee to recognize assets and liabilities on the balance sheet for operating leases and changes many key definitions, including the definition of a lease. The new standard includes a short-term lease exception for leases with a term of 12 months or less, as part of which a lessee can make an accounting policy election not to recognize lease assets and lease liabilities. Lessees will continue to differentiate between finance leases (previously referred to as capital leases) and operating leases using classification criteria that are substantially similar to the previous guidance. The new standard will be effective beginning January 1, 2019 and early adoption is permitted for public entities. The Company is currently evaluating the potential impact ASU 2016-02 may have on its financial position and results of operations.

ASU 2017-04, Intangibles – Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment

In January 2017, the FASB issued ASU 2017-04, Intangibles – Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment.  To address concerns over the cost and complexity of the two-step goodwill impairment test, the amendments in this ASU remove the second step of the test. An entity will instead apply a one-step quantitative test and record the amount of goodwill impairment as the excess of a reporting unit's carrying amount over its fair value, not to exceed the total amount of goodwill allocated to the reporting unit. The new guidance does not amend the optional qualitative assessment of goodwill impairment. The new standard will be effective beginning January 1, 2020 and early adoption is permitted with measurement dates on or after January 1, 2017. The adoption of this standard is not expected to have a material impact on the Company’s financial position or results of operations upon adoption.

ASU 2017-08, Receivables – Nonrefundable Fees and Other Costs

In April 2017, the FASB issued ASU 2017-08, Receivables – Nonrefundable Fees and Other Costs (“Subtopic 310-20”). The new standard amends the amortization period for certain purchased callable debt securities held at a premium by shortening the amortization period for the premium to the earliest call date. Subtopic 310-20 calls for a modified retrospective application under which a cumulative-effect adjustment will be made to retained earnings as of the beginning of the first reporting period in which the guidance is adopted. The new standard will be effective beginning January 1, 2019 and early adoption is permitted for public entities. The adoption of this standard is not expected to have a material impact on the Company’s financial position or results of operations upon adoption.

10

ASU 2018-02, Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income

In February 2018, the FASB issued ASU 2018-02, Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income (“ASU 2018-01”).  The new standard allows for a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the Tax Cuts and Jobs Act.  The new standard will be effective beginning January 1, 2019 and early adoption is permitted.  The Company is currently evaluating the potential impact ASU 2018-02 may have on its financial position and results of operations upon adoption.

3. Marketable securities

The following table summarizes the available-for-sale securities held at March 31, 2018 and December 31, 2017 (in thousands):

The amortized cost of available-for-sale securities is adjusted for amortization of premiums and accretion of discounts to maturity. At March 31, 2018 and December 31, 2017, the balance in the Company’s accumulated other comprehensive loss was composed primarily of activity related to the Company’s available-for-sale marketable securities. There were no material realized gains or losses recognized on the sale or maturity of available-for-sale securities during the three months ended March 31, 2018 or 2017, and as a result, the Company did not reclassify any amounts out of accumulated other comprehensive loss for the same periods.

The aggregate fair value of securities held by the Company in an unrealized loss position for less than twelve months as of March 31, 2018 and December 31, 2017 was $918.9 million and $704.1 million, respectively. As of March 31, 2018 and December 31, 2017, there were $142.7 million and $134.4 million in securities held by the Company in an unrealized loss position for more than twelve months, respectively. The Company has the intent and ability to hold such securities until recovery. The Company determined that there was no material change in the credit risk of the above investments. As a result, the Company determined it did not hold any investments with any other-than-temporary impairment as of March 31, 2018 and December 31, 2017.

No available-for-sale securities held as of March 31, 2018 or December 31, 2017 had remaining maturities greater than three years.

11

4. Fair value measurements

The following table sets forth the Company’s assets and liabilities that are measured at fair value on a recurring basis as of March 31, 2018 and December 31, 2017 (in thousands):

Cash, cash equivalents and marketable securities

The Company considers all highly liquid securities with original final maturities of 90 days or less from the date of purchase to be cash equivalents. As of March 31, 2018, cash and cash equivalents comprises funds in cash, money market accounts, U.S. treasury securities, and government agency securities. As of December 31, 2017, cash and cash equivalents comprises funds in cash and money market accounts.

Cash equivalents and marketable securities classified as Level 2 within the valuation hierarchy generally consist of U.S. treasury securities and government agency securities. The Company estimates the fair values of these marketable securities by taking into consideration valuations obtained from third-party pricing sources. These pricing sources utilize industry standard valuation models, including both income and market-based approaches, for which all significant inputs are observable, either directly or indirectly, to estimate fair value. These inputs include market pricing based on real-time trade data for the same or similar securities, issuer credit spreads, benchmark yields, and other observable inputs. The Company validates the prices provided by our third-party pricing sources by understanding the models used, obtaining market values from other pricing sources and analyzing pricing data in certain instances.

Contingent consideration

In connection with its prior acquisition of Pregenen, the Company may be required to pay future consideration that is contingent upon the achievement of specified development, regulatory approvals or sales-based milestone events. Contingent consideration is measured at fair value and is based on significant inputs not observable in the market, which represents a Level 3 measurement within the fair value hierarchy. The valuation of contingent consideration uses assumptions the Company believes would be made by a market participant. The Company assesses these estimates on an on-going basis as additional data impacting the assumptions is obtained. Future changes in the fair value of contingent consideration related to updated assumptions and estimates are recognized within the condensed consolidated statements of operations and comprehensive loss. In the absence of new information, changes in fair value will reflect changing discount rates and the passage of time.

12

The significant unobservable inputs used in the measurement of fair value of the Company’s contingent consideration are probabilities of successful achievement of clinical and commercial milestones, the period in which these milestones are expected to be achieved ranging from 2021 to 2028 and discount rates ranging from 15.2% to 16.0%. Significant increases or decreases in any of the probabilities of success would result in a significantly higher or lower fair value measurement, respectively. Significant increases or decreases in the other inputs would result in a significantly lower or higher fair value measurement, respectively.

The table below provides a roll-forward of fair value of the Company’s contingent consideration obligations, which include Level 3 inputs (in thousands):

Please refer to Note 7, “Commitments and contingencies” for further information.

5. Property, plant and equipment, net

Property, plant and equipment, net, consists of the following (in thousands):

North Carolina manufacturing facility

In November 2017, the Company acquired a manufacturing facility, which is in the process of construction, in Durham, North Carolina for the future manufacture of lentiviral vector for the Company’s gene and cell therapies.  Construction-in-progress as of March 31, 2018 and December 31, 2017 includes $16.3 million and $12.9 million, respectively, related to the North Carolina manufacturing facility.

60 Binney Street lease

As of March 31, 2018, total property, plant and equipment, gross, includes $165.6 million related to the Company’s headquarters at 60 Binney Street in Cambridge, Massachusetts, of which $156.0 million was incurred by the landlord. As of December 31, 2017, total property, plant and equipment, gross, includes $164.4 million related to the Company’s headquarters at 60 Binney Street in Cambridge, Massachusetts, of which $156.0 million was incurred by the landlord.  Please refer to Note 7, "Commitments and contingencies" for further information.

13

6. Accrued expenses and other current liabilities

Accrued expenses and other current liabilities consist of the following (in thousands):

7. Commitments and contingencies

Operating lease commitments

On June 3, 2016, the Company entered into a strategic manufacturing agreement for the future commercial production of the Company’s Lenti-D and LentiGlobin product candidates with a contract manufacturing organization. Under this 12 year agreement, the contract manufacturing organization will complete the design, construction, validation and process validation of the leased suites prior to anticipated commercial launch of the product candidates. During construction, the Company was required to pay $12.5 million upon the achievement of certain contractual milestones, and may pay up to $8.0 million in additional contractual milestones if the Company elects its option to lease additional suites. The Company paid $5.0 million for the achievement of the first and second contractual milestones during 2016 and paid $5.5 million for the third and fourth contractual milestones achieved during 2017.  In March 2018, $1.5 million of the possible $2.0 million related to the fifth contractual milestone was achieved and will be paid in the second quarter of 2018.  Given that construction was completed in March 2018, beginning in April 2018 the Company will pay $5.1 million per year in fixed suite fees as well as certain fixed labor, raw materials, testing and shipping costs for manufacturing services, and may pay additional suite fees if it elects its option to reserve or lease additional suites. The Company may terminate this agreement at any time upon payment of a one-time termination fee and up to 24 months of fixed suite and labor fees. The Company concluded that this agreement contains an embedded lease as the suites are designated for the Company’s exclusive use during the term of the agreement. The Company concluded that it is not the deemed owner during construction nor is it a capital lease under ASC 840-10, Leases – Overall.  As a result, the Company accounts for the agreement as an operating lease and expenses the rental payments on a straight-line basis over the non-cancellable term of the embedded lease.

On November 18, 2016, the Company entered into an agreement for future clinical and commercial production of the Company’s LentiGlobin gene therapy drug products with a contract manufacturing organization at an existing facility. The term of the agreement is five years with a three year renewal at the mutual option of each party. Under the agreement, the Company is required to pay an up-front fee of €3.0 million, €2.0 million of which was paid in the fourth quarter of 2016 and €1.0 million of which is expected to be paid in mid-2018, and annual maintenance and production fees of up to €9.8 million, depending on its production needs. The Company may terminate this agreement with six months’ notice and a one-time termination fee prior to July 1, 2018, or twelve months’ notice and a one-time termination fee thereafter. The Company concluded that this agreement contains an embedded lease as the clean rooms are designated for the Company’s exclusive use during the term of the agreement, and determined that it is not a capital lease under ASC 840-10, Leases – Overall. As a result, the Company accounts for the agreement as an operating lease and expenses the rental payments on a straight-line basis over the non-cancellable term of the embedded lease.

60 Binney Street Lease commitments

On September 21, 2015, the Company entered into a lease agreement for office and laboratory space located in a building (the “Building”) at 60 Binney Street, Cambridge, Massachusetts (the “60 Binney Street Lease”) to become its new corporate headquarters with a term through March 31, 2027.  Although the Company does not legally own the premises, it is deemed to be the owner of the building for accounting purposes because the Company was involved in the construction project, including having responsibility to pay for a portion of the costs of finish work and mechanical, electrical, and plumbing elements of the Building during the construction period. Accordingly, construction costs that were incurred by the landlord directly or indirectly through reimbursement to the Company as part of its tenant improvement allowance have been recorded as an asset in “Property, plant and equipment, net” with a related financing obligation in “Accrued expenses and other current liabilities” and “Financing lease obligation, net of current portion” on the Company’s condensed consolidated balance sheets.

14

The Company evaluated the 60 Binney Street Lease upon occupancy on March 27, 2017 and determined that the 60 Binney Street Lease did not meet the criteria for “sale-leaseback” treatment. This determination was based on, among other things, the Company's continuing involvement with the property in the form of non-recourse financing to the lessor. Accordingly, upon occupancy, the Company commenced depreciating the portion of the building in service over a useful life of 40 years and incurred interest expense related to the financing obligation of $3.9 million for the three months ended March 31, 2018.  The Company currently maintains a $13.8 million letter of credit as required under the terms of the lease.  Subject to the terms of the lease and certain reduction requirements specified therein, including market capitalization requirements, this amount may decrease back to $9.2 million over time.

Contingent consideration related to business combinations

On June 30, 2014, the Company acquired Pregenen. The Company may be required to make up to $120.0 million in remaining future contingent cash payments to the former equityholders of Pregenen upon the achievement of certain clinical and commercial milestones related to the Pregenen technology, of which $20.1 million relates to clinical milestones and $99.9 million relates to commercial milestones. In accordance with accounting guidance for business combinations, contingent consideration liabilities are required to be recognized on the consolidated balance sheets at fair value. Estimating the fair value of contingent consideration requires the use of significant assumptions primarily relating to probabilities of successful achievement of certain clinical and commercial milestones, the expected timing in which these milestones will be achieved and discount rates. The use of different assumptions could result in materially different estimates of fair value. Please refer to Note 4, “Fair value measurements” for additional information.

Other funding commitments

The Company is party to various agreements, principally relating to licensed technology, that require future payments relating to milestones not met at March 31, 2018 and December 31, 2017 or royalties on future sales of specified products.  Additionally, the Company is party to various contracts with contract research organizations and contract manufacturers that generally provide for termination on notice, with the exact amounts in the event of termination to be based on the timing of the termination and the terms of the agreement.  In each of 2018 and 2019, the Company expects to make payments of approximately $12.0 million under an agreement with a contract manufacturer.

8. Collaboration revenue

To date, the Company’s collaboration revenue has been exclusively generated from its collaboration arrangement with Celgene, which was originally entered into in March 2013 and was subsequently amended in June 2015, as further described below.

Original Collaboration Agreement

On March 19, 2013, the Company entered into a Master Collaboration Agreement (the “Collaboration Agreement”) with Celgene to discover, develop and commercialize potentially disease-altering gene therapies in oncology. The collaboration is focused on applying gene therapy technology to genetically modify a patient’s own T cells, known as chimeric antigen receptor, or CAR T cells, to target and destroy cancer cells. Additionally, on March 19, 2013, the Company entered into a Platform Technology Sublicense Agreement with Celgene pursuant to which the Company obtained a sublicense to certain intellectual property from Celgene, originating under Celgene’s license from Baylor College of Medicine, for use in the collaboration.

Under the terms of the Collaboration Agreement, the Company received a $75.0 million up-front, non-refundable cash payment. The Company is responsible for conducting discovery, research and development activities through completion of Phase I clinical studies during the initial term of the Collaboration Agreement, or three years. The collaboration is governed by a joint steering committee (“JSC”) formed by an equal number of representatives from the Company and Celgene. The JSC, among other activities, reviews the collaboration program, reviews and evaluates product candidates and approves regulatory plans. In addition to the JSC, the Collaboration Agreement provides that the Company and Celgene each appoint representatives to a patent committee, which is responsible for managing the intellectual property developed and used during the collaboration.

Amended Collaboration Agreement

On June 3, 2015, the Company and Celgene amended and restated the Collaboration Agreement (the “Amended Collaboration Agreement”).  Under the Amended Collaboration Agreement, the parties narrowed the focus of the collaboration exclusively to anti- B-cell maturation antigen (“BCMA”) product candidates for a new three-year term ending in June 2018. In connection with the Amended Collaboration Agreement, the Company received an upfront, one-time, non-refundable, non-creditable payment of $25.0 million. The collaboration will continue to be governed by the JSC. Under the terms of the Amended Collaboration Agreement, for up

15

to two product candidates selected for development under the collaboration, the Company is responsible for conducting and funding all research and development activities performed up through completion of the initial Phase I clinical study of such product candidate.

On a product candidate-by-product candidate basis, up through a specified period following enrollment of the first patient in an initial Phase I clinical study for such product candidate (the “Option Period”), the Company granted Celgene an option to obtain an exclusive worldwide license to develop and commercialize such product. Following Celgene’s license of each product candidate, the Company is entitled to elect to co-develop and co-promote each product candidate in the U.S.

bb2121 License Agreement

On February 10, 2016, Celgene exercised its option to obtain an exclusive worldwide license to develop and commercialize bb2121, the first product candidate under the Amended Collaboration Agreement, pursuant to an executed license agreement (“bb2121 License Agreement”) entered into by the parties on February 16, 2016 and paid the Company an option fee of $10.0 million. Pursuant to the bb2121 License Agreement, Celgene is responsible for development and related funding of bb2121 after the substantial completion of the on-going Phase I clinical trial. The Company is responsible for the manufacture of vector and associated payload throughout development and, upon Celgene’s request, commercialization, which is fully reimbursed by Celgene, and Celgene is responsible for the manufacture of drug product throughout development and commercialization.

bb2121 Co-Development, Co-Promote and Profit Share Agreement

On March 28, 2018, the Company elected to co-develop and co-promote bb2121 within the U.S. pursuant to the execution of the Amended and Restated Co-Development, Co-Promote and Profit Share Agreement (“bb2121 CCPS”).  The responsibilities of the parties remain unchanged from those under the bb2121 License Agreement, however, the Company will share equally in all profits and losses relating to developing, commercializing and manufacturing bb2121 within the U.S. and has the right to participate in the development and promotion of bb2121 in the U.S. Under the bb2121 CCPS, the Company may receive up to $70.0 million in development milestone payments for the first indication to be addressed by the bb2121 product candidate, with the ability to obtain additional milestone payments for a second indication and modified licensed products.  In addition, to the extent bb2121 is commercialized, the Company would be entitled to receive tiered royalty payments ranging from the mid-single digits to low-teens based on a percentage of net sales generated outside of the U.S., subject to certain reductions.

bb21217 License Agreement

On September 22, 2017, Celgene exercised its option to obtain an exclusive worldwide license to develop and commercialize bb21217, the second product candidate under the Amended Collaboration Agreement, pursuant to an executed license agreement (“bb21217 License Agreement”) entered into by the parties on September 28, 2017 and paid the Company an option fee of $15.0 million. Pursuant to the bb21217 License Agreement, Celgene is responsible for development and related funding of bb21217 after the substantial completion of the on-going Phase I clinical trial.  The Company is responsible for the manufacture of vector and associated payload throughout development and, upon Celgene’s request, commercialization, which is fully reimbursed by Celgene, and Celgene is responsible for the manufacture of drug product throughout development and commercialization.

The Company currently expects it will exercise its option to co-develop and co-promote bb21217 within the U.S.  The Company’s election to co-develop and co-promote bb21217 must be made by the substantial completion of the ongoing Phase I trial of bb21217.  If elected, the Company expects the responsibilities of the parties to remain largely unchanged, however, the Company expects it will share equally in all profits and losses relating to developing, commercializing and manufacturing bb21217 within the U.S. and to have the right to participate in the development and promotion of bb21217 in the U.S.  Under this scenario, the Company expects to receive, per product, up to $70.0 million in development milestone payments for the first indication to be addressed by the bb21217 product candidate, with the ability to obtain additional milestone payments for a second indication and modified licensed products.  In addition, to the extent bb21217 is commercialized, the Company would be entitled to receive tiered royalty payments ranging from the mid-single digits to low-teens based on a percentage of net sales generated outside of the U.S., subject to certain reductions.

In the event the Company does not exercise its option to co-develop and co-promote bb21217, the Company will receive an additional fee in the amount of $10.0 million. Under this scenario, the Company may be eligible to receive up to $10.0 million in clinical milestone payments, up to $117.0 million in regulatory milestone payments, and up to $78.0 million in commercial milestone payments. In addition, to the extent bb21217 is commercialized, the Company would be entitled to receive tiered royalty payments ranging from the mid-single digits to low-teens based on a percentage of net sales, subject to certain reductions.

16

Accounting analysis – bb2121

The Company has elected to use a practical expedient within Topic 606 that allow entities to reflect the aggregate effect of all contract modifications when identifying the satisfied and unsatisfied performance obligations for contracts that were modified prior to Topic 606 adoption. Celgene’s option to in-license the first product candidate, bb2121, under the arrangement was considered a material right at the time the Amended Collaboration Agreement was executed in June 2015 given the product candidate had been formally nominated by the JSC and that substantially all investigational new drug application, or IND, enabling activities had been completed by that time.  Therefore, Celgene’s February 2016 exercise of its option that was considered a material right to obtain an exclusive worldwide license to develop and commercialize the first product candidate, bb2121, under the collaboration represented a contract modification. As a result, the Collaboration Agreement, Amended Collaboration Agreement, and bb2121 License Agreement are combined for accounting purposes and treated as a single arrangement. As of February 2016, Celgene’s option to license an additional product candidate under the collaboration did not represent a material right. Therefore, the license to the Company’s second product candidate, bb21217, which was executed in September 2017, is accounted for as a separate contract.  Refer below for discussion of the bb21217 accounting analysis.

As of the February 2016 contract modification date, the Company concluded the arrangement contained the following promised goods and services: (i) research and development services, (ii) a license to the first product candidate, bb2121, and (iii) manufacture of vectors and associated payload for incorporation into bb2121 through development.  The Company determined that the manufacture of commercial vector represents an option to acquire additional goods and services that is not representative of a material right. In addition, at this time Celgene has not exercised its option to purchase any commercial vector. Accordingly, the manufacture of commercial vector is not considered to be a performance obligation at this time.

The Company concluded that the research and development services are distinct from the other promised goods and services under the arrangement and thus such services are considered to be a separate performance obligation.  The Company concluded that the license to bb2121 is not distinct from the vector manufacturing services because the manufacturing is essential to the use of the license. Accordingly, these two promised goods and services are considered a single combined performance obligation.  

The up-front non-refundable fees of $100.0 million, the option fee of $10.0 million, and the variable consideration related to the estimated reimbursement from Celgene for the manufacture of vectors and associated payload through development constitute the total amount of consideration of $176.2 million to be included in the transaction price. This consideration has been allocated to the performance obligations identified based on a relative SSP basis.  The Company estimated the SSP of the license after considering potential future cash flows under the license. The Company then discounted these probability-weighted cash flows to their present value. The Company estimated the SSP of each of the research and development services and manufacturing services to be provided based on the Company’s estimated cost of providing the services plus an applicable profit margin commensurate with observable market data for similar services.

None of the clinical or regulatory milestones have been included in the transaction price, as all milestone amounts are fully constrained. As part of its evaluation of the constraint, the Company considered numerous factors, including the fact that achievement of the milestones is outside the control of the Company and contingent upon the future success of its clinical trials, the licensee’s efforts, and the receipt of regulatory approval. Any consideration related to sales-based milestones (including royalties) will be recognized when the related sales occur as these amounts have been determined to relate predominantly to the license granted to Celgene and therefore are recognized at the later of when the performance obligation is satisfied, or the related sales occur. The Company will re-evaluate the transaction price, including its estimated variable consideration included in the transaction price and all constrained amounts, in each reporting period and as uncertain events are resolved or other changes in circumstances occur.

bb2121 research and development services

The Company allocated $34.8 million of the transaction price to the research and development services.  The Company will satisfy this performance obligation as the research and development services are performed.  The Company determined that the period of performance of the research and development services was three years through projected initial Phase I clinical study substantial completion, or through May 2018.  The Company recognizes revenue related to research and development services performed using an input method by calculating costs incurred at each period end relative to total costs expected to be incurred.  

The Company recognized revenue related to bb2121 research and development services of $2.2 million and $1.5 million for the three months ended March 31, 2018 and 2017, respectively. The Company had $0.1 million remaining in deferred revenue as of March 31, 2018 associated with research and development services.

17

bb2121 license and manufacturing services

The Company allocated $141.4 million of the transaction price to the combined unit of accounting which consists of the license and manufacture of vectors and associated payload for incorporation into bb2121.

The Company accounts for its vector manufacturing services for development in the U.S. and Celgene’s U.S. development efforts within the scope of ASC 808 given that both parties are active participants in the activities and both parties are exposed to significant risks and rewards dependent on the commercial success of the activities.  The Company recognizes revenue for its U.S. manufacturing services by analogy to Topic 606.  The portion of Celgene’s U.S. development costs that bluebird is responsible for are recognized as a reduction to its collaboration revenues, or, if in excess of such revenues in a given quarter, as research and development expense.

Revenue recognition for the combined unit of accounting commenced during the first quarter of 2017.  The Company recognizes revenue associated with the combined unit of accounting using the proportional performance method, as the Company will satisfy this performance obligation as the manufacturing services are performed through development. In using this method the Company estimated its development plan for bb2121, including expected demand from Celgene, and the costs associated with the manufacture of vectors and associated payload for incorporation into bb2121. On a quarterly basis, the Company determines the proportion of effort incurred as a percentage of total effort it expects to expend.  This ratio is applied to the transaction price, which included variable consideration, allocated to the combined performance obligation consisting of the bb2121 license and manufacturing services. Management has applied significant judgment in the process of developing its budget estimates and any changes to these estimates will be recognized in the period in which they change as a cumulative catch up.

In developing the SSP for the combined performance obligation, management assumed that the Company would exercise its option to co-develop and co-promote bb2121, and therefore will recognize revenue related to 67.5% of worldwide development costs incurred, which represents the percentage the Company is contractually entitled to bill Celgene under the cost share provisions of the co-development and co-promotion agreement, upon its execution.  The Company exercised its option to co-develop and co-promote bb2121 in March 2018.  The period of performance and pattern of revenue recognition remained unchanged upon its execution and will be revisited as the development plan changes or if other events occur.

The Company recognized revenue of $3.9 million (representative of gross revenue of $11.8 million offset by approximately $7.9 million of cost reimbursement to Celgene) during the three months ended March 31, 2018 related to the combined unit of accounting for its license and vector manufacturing of bb2121 in the U.S.

Revenue related to the combined unit of accounting for its rest of world license and vector manufacturing services is accounted for in accordance with Topic 606 and is recognized as collaboration revenue. The Company recognized $8.8 million of revenue related to the combined unit of accounting for its rest of world license and vector manufacturing services for the three months ended March 31, 2018 in accordance with Topic 606.  The Company recognized $4.9 million of revenue related to the combined unit of accounting of accounting for its license and vector manufacturing services for the three months ended March 31, 2017 in accordance with ASC 605.

As of March 31, 2018, the aggregate amount of the transaction price allocated to the combined performance obligation, which consists of the bb2121 license and manufacturing services, that is unsatisfied, or partially unsatisfied, is $90.7 million, which the Company expects to recognize as revenue as manufacturing services are provided through the remaining development period which is estimated to be through 2021.  The Company had $48.6 million remaining deferred revenue as of March 31, 2018 associated with the combined performance obligation consisting of the bb2121 license and manufacturing services.

Accounting analysis – bb21217

On September 22, 2017, Celgene exercised its option to obtain an exclusive worldwide license to develop and commercialize bb21217, the second optioned product candidate, pursuant to the bb21217 License Agreement entered into by the parties on September 28, 2017.  The bb21217 License Agreement is considered a separate contract for accounting purposes as the option to obtain an exclusive worldwide license to develop and commercialize bb21217, or any other product candidate, was not considered a material right to Celgene at the time the practical expedient was applied. The Company made this evaluation after considering the significant uncertainty at that time regarding whether any additional product candidates would be identified under the Amended Collaboration Agreement. In particular, the Company considered that bb21217 had not been formally nominated as a product candidate under the collaboration at that time, primarily due to a lack of pre-clinical data as well as uncertainty surrounding the ability to successfully complete various IND-enabling activities.

At contract inception, the Company concluded that the arrangement contained the following promised goods and services: (i) research and development services, (ii) a license to the second product candidate, bb21217, and (iii) manufacture of vectors and associated payload for incorporation into bb21217 through development.  The Company determined that the manufacture of

18

commercial vector represents an option to acquire additional goods and services that is not representative of a material right. In addition, at this time Celgene has not exercised its option to purchase any commercial vector. Accordingly, the manufacture of commercial vector is not considered to be a performance obligation at this time.

The Company concluded that the research and development services are distinct from the other promised goods and services under the arrangement and thus is considered to be a performance obligation. Similar to bb2121, the Company concluded that the license to bb21217 is not distinct from the vector manufacturing services because the manufacturing is essential to the use of the license. Accordingly, these two promised goods and services are considered a single combined performance obligation.

The option fee of $15.0 million and the estimated variable consideration related to reimbursement from Celgene for the manufacturing services during development constituted the total amount of consideration of $41.7 million to be included in the transaction price and have been allocated to the performance obligations identified based on a relative SSP basis. The Company estimated the SSP of the license after considering potential future cash flows under the license. The Company then discounted these probability-weighted cash flows to their present value. The Company estimated the SSP of each of the research and development services and manufacturing services to be provided based on the Company’s estimated cost of providing the services plus an applicable profit margin commensurate with observable market data for similar services.

None of the clinical or regulatory milestones have been included in the transaction price, as all milestone amounts are fully constrained. As part of its evaluation of the constraint, the Company considered numerous factors, including the fact that achievement of the milestones is outside the control of the Company and contingent upon the future success of its clinical trials, the licensee’s efforts, and the receipt of regulatory approval. Any consideration related to sales-based milestones (including royalties) will be recognized when the related sales occur as these amounts have been determined to relate predominantly to the license granted to Celgene and therefore are recognized at the later of when the performance obligation is satisfied, or the related sales occur. The Company will re-evaluate the transaction price, including is estimated variable consideration included in the transaction price and all constrained amounts, in each reporting period and as uncertain events are resolved or other changes in circumstances occur.

bb21217 research and development services

The Company allocated $5.4 million of the transaction price to the research and development services. The Company will satisfy this performance obligation as the research and development services are performed.  The Company determined that the period of performance of the research and development services was two years through projected initial Phase I clinical study substantial completion, or through September 2019.  The Company recognizes revenue related to research and development services performed using an input method by calculating costs incurred at each period end relative to total costs expected to be incurred.

The Company recognized revenue related to bb21217 research and development services for Celgene of $0.7 million for the three months ended March 31, 2018.  During the three months ended March 31, 2017, the Company did not recognize any revenue under the bb21217 License Agreement.

The aggregate amount of the transaction price allocated to the bb21217 research and development services performance obligation that are unsatisfied, or partially unsatisfied, is $4.0 million, which the Company expects to recognize through September 2019 as research and development services are performed.  The Company had $4.3 million remaining in deferred revenue as of March 31, 2018 associated with research and development services.

bb21217 license and manufacturing services

The Company will satisfy its performance obligation related to the manufacture of vectors and associated payload for incorporation into bb21217 through development as the bb21217 manufacturing services are performed. As of March 31, 2018, the manufacturing services for bb21217 had not yet commenced.  Therefore, no revenue has been recognized for the combined unit of accounting for the three months ended March 31, 2018 and 2017.

The aggregate amount of the transaction price allocated to the combined performance obligation, which consists of the bb21217 license and manufacturing services, is $36.2 million.  The Company currently expects that recognition will commence in 2019 and has classified deferred revenue associated with the combined performance obligation as deferred revenue, net of current portion on its consolidated balance sheet. The Company had $9.8 million remaining deferred revenue as of March 31, 2018 associated with the combined performance obligation consisting of the bb21217 license and manufacturing services.

Contract assets and liabilities

19

The Company receives payments from Celgene based on billing schedules established in each contract. Up-front payments and fees are recorded as deferred revenue upon receipt or when due until such time as the Company satisfies its performance obligations under these arrangements. A contract asset is a conditional right to consideration in exchange for goods or services that the Company has transferred to a customer.  Amounts are recorded as accounts receivable when the Company’s right to consideration is unconditional.  The Company does not have any contract assets as of March 31, 2018.

The following table presents changes in the balances of the Company’s Celgene receivables and contract liabilities during the three months ended March 31, 2018:

The change in the receivables balance for the three months ended March 31, 2018 is primarily driven by an increase in the amounts owed to the Company for the satisfaction, or partial satisfaction, of vector manufacturing services performed in the period.  The decrease in deferred revenue during the three months ended March 31, 2018 is driven by revenue recognized for the combined performance obligation consisting of the bb2121 license and manufacturing services.

To date, there have been no impairment losses recognized on any receivables arising from the Company’s contracts with customers.

During the three months ended March 31, 2018, $14.0 million of the deferred revenue balance at the beginning of the period was recognized as gross revenues.

9. License and royalty revenue

Novartis Pharma AG

On April 26, 2017, the Company entered into a worldwide license agreement with Novartis Pharma AG, or Novartis. Under the terms of the agreement, Novartis non-exclusively licensed certain patent rights related to lentiviral vector technology to develop and commercialize CAR T cell therapies for oncology, including Kymriah (formerly known as CTL019), Novartis’s anti-CD19 CAR T therapy. At contract inception, financial terms of the agreement included a $7.5 million payment upon execution, $7.5 million of potential future milestone payments associated with regulatory approvals, and $1.1 million of payments for each subsequently licensed product, as well as low single digit royalty payments on net sales of covered products. In August 2017, Novartis received FDA approval for Kymriah and paid the Company $2.5 million as a result of the achievement of a related milestone.  

Given this arrangement is within the scope of Topic 606, the Company assessed this arrangement in accordance with Topic 606 and concluded that at the date of contract inception, only one performance obligation, consisting of the license which was satisfied at contract inception, was identified. Accordingly, the nonrefundable license fee of $7.5 million was recognized as revenue upon contract execution and the $2.5 million regulatory milestone was also recognized as revenue upon milestone achievement given there were no other unsatisfied performance obligations in the arrangement. This accounting conclusion was unchanged from its historical treatment under ASC 605. Because the single performance obligation was previously satisfied, all regulatory milestones will be recognized as revenue in full in the period in which the associated milestone is achieved. Regulatory approvals are not within the Company’s control or the licensee’s control and are generally not considered probable of being achieved until those approvals are received. As such, these milestones are constrained and excluded from the transaction price until such time as regulatory approvals are received.

The Company began recognizing royalty revenue from sales of Kymriah in the fourth quarter of 2017. As the license was deemed to be the predominant item to which the royalties relate, the Company recognizes royalties from the sales of Kymriah when the related sales occur. For the three months ended March 31, 2018, the Company recognized royalty revenue of $0.3 million. The associated cost of license revenue was less than $0.1 million for the same period.  For the three months ended March 31, 2017, there was no license and royalty revenue, or cost of license and royalty revenue, recognized.

Orchard Therapeutics Limited (formerly GlaxoSmithKline Intellectual Property Development Limited)

On April 28, 2017, the Company entered into a worldwide license agreement with GlaxoSmithKline Intellectual Property Development Limited, or GSK. Under the terms of the agreement, GSK non-exclusively licensed certain patent rights related to lentiviral vector technology to develop and commercialize gene therapies for Wiscott-Aldrich syndrome and metachromatic

20

leukodystrophy, two rare genetic diseases. Financial terms of the agreement include a nonrefundable upfront payment of $3.0 million as well as $1.3 million of potential milestone payments for each marketing authorization for each indication in any country as well as low single digit royalties on net sales of covered products. This license agreement was assigned by GSK to Orchard Therapeutics Limited, effective as of April 11, 2018.  

Given this arrangement is within the scope of Topic 606, the Company assessed this arrangement in accordance with Topic 606 and concluded that at the date of contract inception, only one performance obligation, consisting of the license which was satisfied at contract inception, was identified. Accordingly, the entire nonrefundable license fee of $3.0 million was recognized as revenue upon contract execution given there were no other unsatisfied performance obligations in the arrangement.  This accounting conclusion was unchanged from its historical treatment under ASC 605. Because the single performance obligation was previously satisfied, all regulatory milestones will be recognized as revenue in full in the period in which the associated milestone is achieved. Regulatory approvals are not within the Company’s control or the licensee’s control and are generally not considered probable of being achieved until those approvals are received. As such, these milestones are constrained and excluded from the transaction price until such time as regulatory approvals are received.  There was no revenue recognized under this arrangement in the three months ended March 31, 2018 and 2017.

10. Equity

On December 15, 2017, the Company sold 3.2 million shares of common stock (excluding any shares sold pursuant to an overallotment option granted to the underwriters in connection with the offering) through an underwritten public offering at a price of $185.00 per share for aggregate net proceeds of $569.8 million.  In January 2018, the Company sold 0.3 million shares of common stock pursuant to the partial exercise of an overallotment option granted to the underwriters in connection with the December 2017 underwritten public offering at a price of $185.00 per share for aggregate net proceeds of $48.7 million.

11. Stock-based compensation

In January 2018 and 2017, the number of shares of common stock available for issuance under the 2013 Stock Option and Incentive Plan (“2013 Plan”) was increased by approximately 2.0 million and 1.6 million shares, respectively, as a result of the automatic increase provision of the 2013 Plan. As of March 31, 2018, the total number of shares of common stock available for issuance under the 2013 Plan was approximately 2.0 million.

Stock-based compensation expense

The Company recognized stock-based compensation expense totaling $23.0 million and $11.5 million for the three months ended March 31, 2018 and 2017, respectively. Stock-based compensation expense by award type included within the condensed consolidated statements of operations and comprehensive loss was as follows (in thousands):

Stock-based compensation expense by classification included within the condensed consolidated statements of operations and comprehensive loss was as follows (in thousands): 

21

In February 2018, the Company issued 0.3 million restricted stock units with service and performance conditions to employees, none of which vested during the three months ended March 31, 2018. Vesting of these awards is contingent on the occurrence of a certain regulatory milestone event and fulfillment of any remaining service condition.  As a result, the related compensation cost is recognized as expense when achievement of the regulatory milestone is considered probable.  The Company did not recognize any expense during the three months ended March 31, 2018 related to this award. Upon achievement of the performance condition, and subject to the service-based condition, the Company may recognize up to $51.8 million in stock-based compensation expense.

As of March 31, 2018, the Company had $295.9 million of unrecognized stock-based compensation expense related to unvested stock options, restricted stock units and the employee stock purchase plan, which is expected to be recognized over a weighted-average period of 3.2 years, exclusive of any potential future stock-based compensation expense that may be recognized on any of the Company’s outstanding performance-based awards for which the performance conditions were deemed not probable of achievement as of March 31, 2018.  

Stock option activity

The following table summarizes the stock option activity under the Company’s equity award plans:

During the three months ended March 31, 2018, 0.3 million shares of common stock were exercised, resulting in total proceeds to the Company of $19.7 million. In accordance with the Company’s equity award plans, the shares were issued from a pool of shares reserved for issuance under the equity award plans.

Restricted stock unit activity

The following table summarizes the restricted stock unit activity under the Company’s equity award plans:

Refer above for discussion of the performance-based restricted stock units granted in February 2018, which are included in the table above.

Employee stock purchase plan

On June 3, 2013, the Company adopted its 2013 Employee Stock Purchase Plan (“2013 ESPP”), which authorized the initial issuance of up to a total of 238,000 shares of the Company’s common stock to participating employees. During the three months ended March 31, 2018 and 2017, 9,055 shares and 11,079 shares of common stock were issued under the 2013 ESPP, respectively.

22

12. Income taxes

Deferred tax assets and deferred tax liabilities are recognized based on temporary differences between the financial reporting and tax basis of assets and liabilities using statutory rates. A valuation allowance is recorded against deferred tax assets if it is more likely than not that some or all of the deferred tax assets will not be realized. Due to the uncertainty surrounding the realization of the favorable tax attributes in future tax returns, the Company has recorded a full valuation allowance against the Company’s otherwise recognizable net deferred tax assets. 

On December 22, 2017, the SEC staff issued Staff Accounting Bulletin No. 118, Income Tax Accounting Implications of the Tax Cuts and Jobs Act (“SAB 118”), which allows the recording of provisional amounts during a measurement period not to extend beyond one year of the enactment date.   In accordance with SAB 118, the Company determined a provisional amount for the impact on its prior year deferred tax assets and valuation allowance in its prior year financial statements.  The Company has not updated the provisional amounts and expects to complete the final assessment of the impact within the measurement period.

13. Net loss per share

The following common stock equivalents were excluded from the calculation of diluted net loss per share for the periods indicated because including them would have had an anti-dilutive effect (in thousands):

23

Item 2. Management’s Discussion and Analysis of Financial Condition and Results of Operations

The following information should be read in conjunction with the unaudited financial information and the notes thereto included in this Quarterly Report on Form 10-Q and the audited financial information and the notes thereto included in our Annual Report on Form 10-K, which was filed with the Securities and Exchange Commission, or the SEC, on February 21, 2018.

Except for the historical information contained herein, the matters discussed in this Quarterly Report on Form 10-Q may be deemed to be forward-looking statements that involve risks and uncertainties. We make such forward-looking statements pursuant to the safe harbor provisions of the Private Securities Litigation Reform Act of 1995 and other federal securities laws. In this Quarterly Report on Form 10-Q, words such as “may,” “expect,” “anticipate,” “estimate,” “intend,” “plan,” and similar expressions (as well as other words or expressions referencing future events, conditions or circumstances) are intended to identify forward-looking statements.

Our actual results and the timing of certain events may differ materially from the results discussed, projected, anticipated, or indicated in any forward-looking statements. We caution you that forward-looking statements are not guarantees of future performance and that our actual results of operations, financial condition and liquidity, and the development of the industry in which we operate may differ materially from the forward-looking statements contained in this Quarterly Report. In addition, even if our results of operations, financial condition and liquidity, and the development of the industry in which we operate are consistent with the forward-looking statements contained in this Quarterly Report, they may not be predictive of results or developments in future periods.

The following information and any forward-looking statements should be considered in light of factors discussed elsewhere in this Quarterly Report on Form 10-Q, including those risks identified under Part II, Item 1A. Risk Factors.

We caution readers not to place undue reliance on any forward-looking statements made by us, which speak only as of the date they are made. We disclaim any obligation, except as specifically required by law and the rules of the SEC, to publicly update or revise any such statements to reflect any change in our expectations or in events, conditions or circumstances on which any such statements may be based, or that may affect the likelihood that actual results will differ from those set forth in the forward-looking statements.

Overview

We are a clinical-stage biotechnology company committed to developing potentially transformative gene therapies for severe genetic diseases and cancer. With our lentiviral-based gene therapy and gene editing capabilities, we have built an integrated product platform with broad potential application in these areas. We believe that gene therapy for severe genetic diseases has the potential to change the way these patients are treated by correcting the underlying genetic defect that is the cause of their disease, rather than offering treatments that only address their symptoms. Our clinical programs in severe genetic diseases include our LentiGlobin^® product candidate to treat transfusion-dependent β-thalassemia, or TDT, and to treat severe sickle cell disease, or severe SCD, and our Lenti-D^TM product candidate to treat cerebral adrenoleukodystrophy, or CALD, a rare hereditary neurological disorder. Our programs in oncology are built upon our leadership in lentiviral gene delivery and T cell engineering, with a focus on developing novel T cell-based immunotherapies, including chimeric antigen receptor (CAR) and T cell receptor (TCR) T cell therapies. bb2121 and bb21217, our product candidates in oncology, are CAR T cell product candidates for the treatment of multiple myeloma. We are co-developing and co-promoting the bb2121 product candidate in the United States with Celgene Corporation, or Celgene, and we have exclusively licensed to Celgene the development and commercialization rights for the bb2121 product candidate outside of the United States. We have exclusively licensed the development and commercialization rights for the bb21217 product candidate to Celgene, with an option to elect to co-develop and co-promote bb21217 within the U.S.

We are developing our LentiGlobin product candidate with the goal of filing for regulatory approval in the US and EU for different genotypes of TDT and for severe SCD.  Both TDT and severe SCD are rare, hereditary blood disorders that often lead to severe anemia and shortened lifespans.  We completed a Phase I/II study of our LentiGlobin product candidate in the United States, Australia, and Thailand for the treatment of subjects with TDT, called the Northstar Study (HGB-204). We are conducting the following clinical studies of our LentiGlobin product candidate: a single-center Phase I/II study in France of our LentiGlobin product candidate for the treatment of subjects with TDT or severe SCD (HGB-205); a multi-site, international, Phase III study for the treatment of subjects with TDT and a non-β⁰/β⁰ genotype, called the Northstar-2 Study (HGB-207); a multi-site, international, Phase III study for the treatment of subjects with TDT and a β⁰/β⁰ genotype, called the Northstar 3 Study (HGB-212); and a multi-site Phase I study in the United States for the treatment of subjects with severe SCD (HGB-206).  We have achieved our enrollment target for the adult and adolescent cohort in the Northstar 2 Study.  We anticipate filing a marketing authorization application in the EU for LentiGlobin for the treatment of adult and adolescent patients with TDT and a non-β⁰/β⁰ genotype during the second half of 2018, with a future Biologics License Application, or BLA, planned in the United States. We are also engaged with the U.S. Food and Drug Administration, or FDA, and the EMA in discussions regarding our proposed development plans for LentiGlobin in severe SCD.

24

We are developing our Lenti-D product candidate with the goal of filing for regulatory approval in the US and EU for CALD, a rare, hereditary neurological disorder that is often fatal.  We are planning to submit our first filing for regulatory approval of Lenti-D in 2019.  We are conducting a multi-site, international, Phase II/III clinical study of our Lenti-D^™ product candidate, called the Starbeam Study (ALD-102), for the treatment of subjects with CALD.  Seventeen subjects were treated with our Lenti-D product candidate in the initial cohort of the Starbeam Study, and we are enrolling up to thirteen additional subjects in an expansion cohort of this study. We are also conducting an observational study of subjects with CALD treated by allogeneic hematopoietic stem-cell transplant referred to as the ALD-103 study. If our Lenti-D product candidate shows a sufficiently compelling treatment effect, and pending further discussion with regulatory authorities, the results from the Starbeam study could potentially form the basis of a BLA and a Marketing Authorization Application, or MAA, submission in the United States and European Union, respectively.

We are developing, in collaboration with Celgene, our bb2121 and bb21217 product candidates with the goal of filing for regulatory approval in multiple myeloma on a global basis, a hematologic malignancy that develops in the bone marrow that is fatal if untreated.  We are conducting a multi-site Phase I clinical study in the United States of our bb2121 product candidate for the treatment of subjects with relapsed/refractory multiple myeloma (CRB-401). bb2121 is the lead product candidate arising from our multi-year collaboration with Celgene, for the discovery, development and commercialization of CAR T cell therapies targeting B-cell maturation antigen, or BCMA. In March 2018 we entered into an agreement with Celgene to co-develop and co-promote bb2121 in which both parties will share equally in U.S. costs and profits.  The FDA has granted Breakthrough Therapy designation and the EMA has granted PRIME eligibility to the bb2121 product candidate for relapsed/refractory multiple myeloma.  In February 2018, Celgene treated the first subject in a multi-site Phase II clinical study in the United States and Europe of our bb2121 product candidate for the treatment of subjects with relapsed/refractory multiple myeloma.  Celgene has announced plans to initiate an international Phase III study of bb2121 in third line multiple myeloma in 2018 and plans to file a BLA with the FDA in 2019 for bb2121 to treat relapsed/refractory multiple myeloma.

In September 2017, we initiated a Phase I clinical study of bb21217, the second anti-BCMA product candidate arising from our collaboration with Celgene, and Celgene exercised its option to obtain an exclusive worldwide license to develop and commercialize bb21217. We currently expect we will exercise our option to co-develop and co-promote bb21217 within the U.S.  The FDA has granted Orphan Drug status to both bb2121 and bb21217 product candidates for the treatment of patients with relapsed/refractory multiple myeloma.

As of March 31, 2018, we had cash, cash equivalents and marketable securities of approximately $1.57 billion. We expect that our existing cash, cash equivalents and marketable securities will be sufficient to fund our current operations into 2021.

Since our inception in 1992, we have devoted substantially all of our resources to our development efforts relating to our product candidates, including activities to manufacture product candidates in compliance with good manufacturing practices, or GMP, to conduct clinical studies of our product candidates, to provide general and administrative support for these operations and to protect our intellectual property. We do not have any products approved for sale and have not generated any revenue from product sales. We have funded our operations primarily through the sale of common stock in our public offerings, private placements of preferred stock and warrants and through collaborations.

We have never been profitable and have incurred net losses in each year since inception. Our net loss was $115.1 million for the three months ended March 31, 2018, and our accumulated deficit was $1.1 billion as of March 31, 2018. Substantially all of our net losses resulted from costs incurred in connection with our research and development programs and from general and administrative costs associated with our operations. We expect to continue to incur significant expenses and increasing operating losses for at least the next several years. We expect our expenses will increase substantially in connection with our ongoing and planned activities, as we:

25

We do not expect to generate revenue from product sales unless and until we successfully complete development and obtain regulatory approval for one or more of our product candidates, which we expect will take a number of years and is subject to significant uncertainty. We currently have no commercial-scale manufacturing facilities, and all of our manufacturing activities are contracted out to third parties. Additionally, we currently utilize third-party contract research organizations, or CROs, to carry out our clinical development activities. If we seek to obtain regulatory approval for any of our product candidates, we expect to incur significant commercialization expenses as we prepare for product sales, marketing, manufacturing, and distribution. Accordingly, we will seek to fund our operations through public or private equity or debt financings, strategic collaborations, or other sources. However, we may be unable to raise additional funds or enter into such other arrangements when needed on favorable terms or at all. Our failure to raise capital or enter into such other arrangements as and when needed would have a negative impact on our financial condition and our ability to develop our products.

Because of the numerous risks and uncertainties associated with product development, we are unable to predict the timing or amount of increased expenses or when or if we will be able to achieve or maintain profitability. Even if we are able to generate revenues from the sale of our products, we may not become profitable. If we fail to become profitable or are unable to sustain profitability on a continuing basis, then we may be unable to continue our operations at planned levels and be forced to reduce our operations.

Financial operations overview

Revenues

To date, we have not generated any revenues from the sale of products. Our revenues have been derived from collaboration arrangements, out-licensing arrangements, research fees, and grant revenues. Effective January 1, 2018, we adopted Accounting Standards Codification (“ASC”), Topic 606, Revenue from Contracts with Customers (“Topic 606”), using the modified retrospective transition method.  

Collaboration revenue is generated exclusively from our collaboration arrangement with Celgene. The terms of the arrangement contain multiple promised goods or services, which include at inception: (i) research and development services, (ii) a license to bb2121, and (iii) manufacture of vectors and associated payload for incorporation into bb2121 under the license.  As of September 2017, the collaboration also includes a license bb21217, the promised goods or services as part of which include: (i) research and development services, (ii) a license to bb21217, and (iii) manufacture of vectors and associated payload for incorporation into bb21217, under the license.  In March 2018, we entered into an agreement with Celgene to co-develop and co-promote bb2121 in which both parties will share equally in U.S. costs and profits.  Collaboration revenue is recognized as the performance obligations are satisfied.

We analyze our collaboration arrangements to assess whether they are within the scope of ASC 808, Collaborative Arrangements (“ASC 808”) to determine whether such arrangements involve joint operating activities performed by parties that are both active participants in the activities and exposed to significant risks and rewards dependent on the commercial success of such activities.  This assessment is performed throughout the life of the arrangement based on changes in the responsibilities of all parties in the arrangement.  For collaboration arrangements within the scope of ASC 808, we first determine which elements of the collaboration are deemed to be within the scope of ASC 808 and those that are more reflective of a vendor-customer relationship and therefore within the scope of Topic 606. For elements of collaboration arrangements that are accounted for pursuant to ASC 808, an appropriate recognition method is determined and applied consistently, generally by analogy to Topic 606.  Amounts that are owed to collaboration partners are recognized as an offset to collaboration revenues as such amounts are incurred by the collaboration partner.  Where amounts owed to a collaboration partner exceed our collaboration revenues in each quarterly period, such amounts are classified as research and development expense. For those elements of the arrangement that are accounted for pursuant to Topic 606, we apply the five-step model prescribed in Topic 606.

Nonrefundable license fees are recognized as revenue upon delivery of the license provided there are no unsatisfied performance obligations in the arrangement.  License revenue has historically been generated from our out-license agreements with Novartis Pharma AG, or Novartis, and GlaxoSmithKline Intellectual Property Development Limited, or GSK. This license agreement was assigned by GSK to Orchard Therapeutics Limited, effective as of April 11, 2018. Under our out-licensing agreements we may also recognize revenue from potential future milestone payments and royalties.

For arrangements with licenses of intellectual property that include sales-based royalties, including milestone payments based on the level of sales, and the license is deemed to be the predominant item to which the royalties relate, we recognize revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which the royalty has been allocated has been satisfied.

26

Research and development expenses

Research and development expenses consist primarily of costs incurred for the development of our product candidates, which include:

Research and development costs are expensed as incurred. Costs for certain development activities are recognized based on an evaluation of the progress to completion of specific tasks using information and data provided to us by our vendors and our clinical sites. We cannot determine with certainty the duration and completion costs of the current or future clinical studies of our product candidates or if, when, or to what extent we will generate revenues from the commercialization and sale of any of our product candidates that obtain regulatory approval. We may never succeed in achieving regulatory approval for any of our product candidates. The duration, costs, and timing of clinical studies and development of our product candidates will depend on a variety of factors, any of which could mean a significant change in the costs and timing associated with the development of our product candidates including:

We plan to increase our research and development expenses for the foreseeable future as we continue to advance the development of our Lenti-D, LentiGlobin, bb2121, and bb21217 product candidates, conduct research and development activities in oncology, including under our strategic collaboration with Celgene, and continue the research and development of product candidates using our gene editing technology platform. Our research and development activities include the following:

27

Our direct research and development expenses consist principally of external costs, such as fees paid to investigators, consultants, central laboratories and CROs in connection with our clinical studies, and costs related to acquiring and manufacturing clinical study materials. We allocate salary and benefit costs directly related to specific programs. We do not allocate personnel-related discretionary bonus or stock-based compensation costs, costs associated with our general discovery platform improvements, depreciation or other indirect costs that are deployed across multiple projects under development and, as such, the costs are separately classified as other research and development expenses in the table below:

The costs associated with our bb21217 program were included in pre-clinical programs until the third quarter of 2017 when we initiated the first clinical study for bb21217.

General and administrative expenses

General and administrative expenses consist primarily of salaries and related costs for personnel, including stock-based compensation and travel expenses for our employees in executive, operational, finance, legal, business development, commercial, information technology, and human resource functions. Other general and administrative expenses include facility-related costs, professional fees for accounting, tax, legal and consulting services, directors’ fees and expenses associated with obtaining and maintaining patents.

We anticipate that our general and administrative expenses will increase in the future as we increase our headcount to support our continued research and development and the potential commercialization of our product candidates. Additionally, we anticipate an increase in payroll and related expenses as a result of our preparation for commercial operations, especially as it relates to the sales and marketing of our product candidates.

Cost of license and royalty revenue

Cost of license and royalty revenue represents expense associated with amounts owed to third party licensors as a result of revenue recognized under our out-license arrangements with Novartis and GSK.

We anticipate that our cost of license and royalty revenue will increase in the future contingent upon the achievement of regulatory milestones by Novartis or GSK.  Additionally, we anticipate that our cost of license and royalty revenue will increase in the future as we expect to continue to recognize royalty revenue related to Novartis’ commercial sale of Kymriah.

28

Change in fair value of contingent consideration

On June 30, 2014, we acquired Pregenen.  The agreement provided for up to $135.0 million in future contingent cash payments by us upon the achievement of certain preclinical, clinical and commercial milestones related to the Pregenen technology.

As of March 31, 2018, there are $120.0 million in future contingent cash payments, of which $20.1 million relates to clinical milestones and $99.9 million relates to commercial milestones. We estimate future contingent cash payments have a fair value of $2.8 million as of March 31, 2018, all of which is classified as a non-current liability on our condensed consolidated balance sheet.

Interest income, net

Interest income, net consists primarily of interest expense on the 60 Binney financing obligation and interest income earned on investments.

Other income (expense), net

Other income (expense), net consists primarily of losses on disposal of assets and gains and losses on foreign currency.

Critical accounting policies and estimates

Our management’s discussion and analysis of our financial condition and results of operations are based on our financial statements, which have been prepared in accordance with generally accepted accounting principles. The preparation of these financial statements requires us to make estimates and judgments that affect the reported amounts of assets, liabilities, and expenses and the disclosure of contingent assets and liabilities in our financial statements. On an ongoing basis, we evaluate our estimates and judgments, including expected business and operational changes, sensitivity and volatility associated with the assumptions used in developing estimates, and whether historical trends are expected to be representative of future trends. We base our estimates on historical experience, known trends and events and various other factors that are believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. Actual results may differ from these estimates under different assumptions or conditions. In making estimates and judgments, management employs critical accounting policies. During the three months ended March 31, 2018, there were no material changes to our critical accounting policies as reported in our Annual Report on Form 10-K for the year ended December 31, 2017, which was filed with the SEC on February 21, 2018, except as otherwise described below.

Revenue recognition

Effective January 1, 2018, we adopted Accounting Standards Codification (“ASC”), Topic 606, Revenue from Contracts with Customers (“Topic 606”), using the modified retrospective transition method. Under this method, we have recognized the cumulative effect of the adoption as an adjustment to the opening balance of accumulated deficit in the current period condensed consolidated balance sheet.  We have not revised our consolidated financial statements for prior periods. This standard applies to all contracts with customers, except for contracts that are within the scope of other standards, such as collaboration arrangements and leases.

Under Topic 606, an entity recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration that the entity expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements that an entity determines are within the scope of Topic 606, the entity performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price, including variable consideration, if any; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the entity satisfies a performance obligation. We only apply the five-step model to contracts when it is probable that the entity will collect the consideration to which it is entitled in exchange for the goods or services it transfers to the customer.

Once a contract is determined to be within the scope of Topic 606, we assess the goods or services promised within each contract and determine those that are performance obligations.  Arrangements that include rights to additional goods or services that are exercisable at a customer’s discretion are generally considered options.  We assess if these options provide a material right to the customer and if so, they are considered performance obligations.  The exercise of a material right is accounted for as a contract modification for accounting purposes.

29

We assess whether each promised good or service is distinct for the purpose of identifying the performance obligations in the contract. This assessment involves subjective determinations and requires management to make judgments about the individual promised goods or services and whether such are separable from the other aspects of the contractual relationship. Promised goods and services are considered distinct provided that: (i) the customer can benefit from the good or service either on its own or together with other resources that are readily available to the customer (that is, the good or service is capable of being distinct) and (ii) the entity’s promise to transfer the good or service to the customer is separately identifiable from other promises in the contract (that is, the promise to transfer the good or service is distinct within the context of the contract).  In assessing whether a promised good or service is distinct, we consider factors such as the research, manufacturing and commercialization capabilities of the collaboration partner and the availability of the associated expertise in the general marketplace. We also consider the intended benefit of the contract in assessing whether a promised good or service is separately identifiable from other promises in the contract. If a promised good or service is not distinct, an entity is required to combine that good or service with other promised goods or services until it identifies a bundle of goods or services that is distinct.

The transaction price is then determined and allocated to the identified performance obligations in proportion to their standalone selling prices (“SSP”) on a relative SSP basis. SSP is determined at contract inception and is not updated to reflect changes between contract inception and when the performance obligations are satisfied. Determining the SSP for performance obligations requires significant judgment. In developing the SSP for a performance obligation, we consider applicable market conditions and relevant entity-specific factors, including factors that were contemplated in negotiating the agreement with the customer and estimated costs. We validate the SSP for performance obligations by evaluating whether changes in the key assumptions used to determine the SSP will have a significant effect on the allocation of arrangement consideration between multiple performance obligations.

If the consideration promised in a contract includes a variable amount, we estimate the amount of consideration to which it will be entitled in exchange for transferring the promised goods or services to a customer. We determine the amount of variable consideration by using the expected value method or the most likely amount method. We include the unconstrained amount of estimated variable consideration in the transaction price. The amount included in the transaction price is constrained to the amount for which it is probable that a significant reversal of cumulative revenue recognized will not occur. At the end of each subsequent reporting period, we re-evaluate the estimated variable consideration included in the transaction price and any related constraint, and if necessary, adjust our estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis in the period of adjustment.

If an arrangement includes development and regulatory milestone payments, we evaluate whether the milestones are considered probable of being reached and estimate the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant revenue reversal would not occur, the associated milestone value is included in the transaction price. Milestone payments that are not within our control or the licensee’s control, such as regulatory approvals, are generally not considered probable of being achieved until those approvals are received.

In determining the transaction price, we adjust consideration for the effects of the time value of money if the timing of payments provides us with a significant benefit of financing.  We do not assess whether a contract has a significant financing component if the expectation at contract inception is such that the period between payment by the licensees and the transfer of the promised goods or services to the licensees will be one year or less.  We assessed each of our revenue generating arrangements in order to determine whether a significant financing component exists and concluded that a significant financing component does not exist in any of our arrangements.

We then recognize as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) each performance obligation is satisfied at a point in time or over time, and if over time this is based on the use of an output or input method.

Collaboration revenue

To date, collaboration revenue has been exclusively generated from our collaboration arrangement with Celgene, which was originally entered into in March 2013 and was subsequently amended in June 2015, as further described in Note 8, “Collaboration revenue”.

We analyze our collaboration arrangements to assess whether they are within the scope of ASC 808, Collaborative Arrangements (“ASC 808”) to determine whether such arrangements involve joint operating activities performed by parties that are both active participants in the activities and exposed to significant risks and rewards dependent on the commercial success of such activities.  This assessment is performed throughout the life of the arrangement based on changes in the responsibilities of all parties in the arrangement.  For collaboration arrangements within the scope of ASC 808 that contain multiple elements, we first determine which elements of the collaboration are deemed to be within the scope of ASC 808 and those that are more reflective of a vendor-customer

30

relationship and therefore within the scope of Topic 606. For elements of collaboration arrangements that are accounted for pursuant to ASC 808, an appropriate recognition method is determined and applied consistently, generally by analogy to Topic 606.  Amounts that are owed to collaboration partners are recognized as an offset to collaboration revenues as such amounts are incurred by the collaboration partner.  Where amounts owed to a collaboration partner exceed our collaboration revenues in each quarterly period, such amounts are classified as research and development expense. For those elements of the arrangement that are accounted for pursuant to Topic 606, we apply the five-step model described above.

License and royalty revenue

We enter into out-licensing agreements that are within the scope of Topic 606. We do not have any material license arrangements that contain more than one performance obligation. The terms of such out-license agreements include the license of functional intellectual property, given the functionality of the intellectual property is not expected to change substantially as a result of the licensor’s ongoing activities, and typically include payment of one or more of the following: non-refundable up-front license fees; development, regulatory and milestone payments based on the level of sales; and royalties on net sales of licensed products. Nonrefundable up-front license fees are recognized as revenue at a point in time when the licensed intellectual property is made available for the customer’s use and benefit, which is generally at the inception of the arrangement.  Milestone fees, which are a type of variable consideration, are recognized as revenue to the extent that it is probable that a significant reversal will not occur. For arrangements with licenses of intellectual property that include sales-based royalties, including milestone payments based on the level of sales, and the license is deemed to be the predominant item to which the royalties relate, we recognize royalty revenue and sales-based milestones at the later of (i) when the related sales occur, or (ii) when the performance obligation to which the royalty has been allocated has been satisfied.

Impact of Topic 606 adoption

As a result of adopting Topic 606, we recorded a $29.4 million adjustment to the opening balance of accumulated deficit in the first quarter of 2018 primarily as a result of the treatment of the up-front consideration received in March 2013 under ASC 605-25 versus Topic 606.  Refer below for a summary of the amount by which each financial statement line item was affected the impact of the cumulative adjustment:

The amount by which each financial statement line item is affected in the current reporting period by Topic 606 as compared with the guidance that was in effect prior to adoption is disclosed below.

31

Results of Operations

Comparison of the three months ended March 31, 2018 and 2017:

Revenues. Total revenue was $16.0 million for the three months ended March 31, 2018, compared to $6.8 million for the three months ended March 31, 2017. The increase of $9.1 million was primarily attributable to collaboration revenue for the bb2121 license and manufacturing services under our agreement with Celgene and the $6.1 million adjustment associated with our adoption of Topic 606.

Research and development expenses. Research and development expenses were $97.1 million for the three months ended March 31, 2018, compared to $55.0 million for the three months ended March 31, 2017. The overall increase of $42.1 million was primarily attributable to the following:

General and administrative expenses. General and administrative expenses were $34.9 million for the three months ended March 31, 2018, compared to $20.3 million for the three months ended March 31, 2017. The increase of $14.6 million was primarily

32

attributable to $5.5 million of increased stock-based compensation expense, $3.9 million of increased employee compensation and benefit expense, as well as $1.1 million in other headcount related costs primarily due to an increase in headcount to support overall growth.  In addition, the overall increase is driven by increased market research costs of $1.7 million and increased professional and consulting fees of $1.7 million.

Cost of license and royalty revenue. Cost of license and royalty revenue was less than $0.1 million for the three months ended March 31, 2018 and nil for the three months ended March 31, 2017.  The increase was attributable to expense associated with amounts owed to third party licensors in connection with royalty revenue recognized under our out-license arrangement with Novartis.

Change in fair value of contingent consideration. The change in fair value of contingent consideration is driven by changes in assumptions related to estimated milestone achievement dates and probabilities of achievement.

Interest income, net.  The change in interest income, net was primarily related to interest income earned on investments, offset by interest expense on the 60 Binney financing obligation.

Other income (expense), net.  The change in other income (expense), net was primarily related to gains and losses on foreign currency.

Liquidity and Capital Resources

As of March 31, 2018, we had cash, cash equivalents and marketable securities of approximately $1.57 billion. We expect cash, cash equivalents and marketable securities to fund our planned operations into 2021. Cash in excess of immediate requirements is invested in accordance with our investment policy, primarily with a view to liquidity and capital preservation. As of March 31, 2018, our funds are primarily held in U.S. Treasury securities, U.S. government agency securities, certificates of deposit and money market accounts.

We have incurred losses and cumulative negative cash flows from operations since our inception in April 1992, and as of March 31, 2018 we had an accumulated deficit of $1.1 billion. We anticipate that we will continue to incur losses for at least the next several years. We expect that our research and development and general and administrative expenses will continue to increase and, as a result, we will need additional capital to fund our operations, which we may raise through public or private equity or debt financings, strategic collaborations, or other sources.

Sources of Liquidity

Cash Flows

The following table sets forth the primary sources and uses of cash for each of the periods below:

Cash Flows from Operating Activities. The $33.5 million increase in cash used in operating activities for the three months ended March 31, 2018 compared to the three months ended March 31, 2017 was partially due to the increase in net loss during this period of $115.1 million, which was driven by increased payroll and payroll-related expenses and spending on our clinical and pre-clinical stage programs to support overall growth.  Cash used in operating activities was also driven by changes in operating assets and liabilities.

Cash Flows from Investing Activities. The $260.3 million increase in cash used by investing activities for the three months ended March 31, 2018 was primarily due to an increase of $319.5 million in cash used to purchase marketable securities, offset by an increase of $40.6 million in proceeds received from the maturity of marketable securities and a decrease of $18.6 million in cash used to purchase property, plant and equipment when compared to the three months ended March 31, 2017.

33

Cash Flows from Financing Activities. The $54.8 million increase in cash provided by financing activities was primarily driven by the January 2018 sale of 0.3 million shares of common stock pursuant to the partial exercise of an overallotment option granted to underwriters in connection with our December 2017 underwritten public offering, which generated net proceeds of $48.7 million.  The overall increase in cash provided by financing activities is also attributed to an increase of $16.9 million in proceeds from the issuance of common stock, offset by a decrease of $10.7 million in the reimbursement of tenant improvements under our financing lease obligation in the three months ended March 31, 2018 compared to the three months ended March 31, 2017.

Contractual Obligations and Commitments

There have been no material changes to our contractual obligations and commitments as included in our Annual Report on Form 10-K, which was filed with the SEC on February 21, 2018.

Off-Balance Sheet Arrangements

As of March 31, 2018, we did not have any off-balance sheet arrangements as defined in the rules and regulations of the SEC.

Item 3. Quantitative and Qualitative Disclosures about Market Risks

We are exposed to market risk related to changes in interest rates. As of March 31, 2018 and December 31, 2017, we had cash, cash equivalents and marketable securities of $1.57 billion and $1.61 billion, respectively, primarily invested in U.S. government agency securities and treasuries, federally insured certificates of deposit and money market accounts invested in U.S. government agency securities. Our primary exposure to market risk is interest rate sensitivity, which is affected by changes in the general level of U.S. interest rates, particularly because our investments are in short-term securities. Our available for sale securities are subject to interest rate risk and will fall in value if market interest rates increase. If market interest rates were to increase immediately and uniformly by 100 basis points, or one percentage point, from levels at March 31, 2018, the net fair value of our interest-sensitive marketable securities would have resulted in a hypothetical decline of approximately $9.3 million.

Item 4. Controls and Procedures

Management’s Evaluation of our Disclosure Controls and Procedures

We maintain disclosure controls and procedures that are designed to ensure that information required to be disclosed in the reports that we file or submit under the Securities and Exchange Act of 1934 is (1) recorded, processed, summarized, and reported within the time periods specified in the SEC’s rules and forms and (2) accumulated and communicated to our management, including our principal executive officer and principal financial officer, to allow timely decisions regarding required disclosure.

As of March 31, 2018, our management, with the participation of our principal executive officer and principal financial officer, evaluated the effectiveness of our disclosure controls and procedures (as defined in Rules 13a-15(e) and 15d-15(e) under the Securities and Exchange Act of 1934). Our management recognizes that any controls and procedures, no matter how well designed and operated, can provide only reasonable assurance of achieving their objectives, and management necessarily applies its judgment in evaluating the cost-benefit relationship of possible controls and procedures. Our principal executive officer and principal financial officer have concluded based upon the evaluation described above that, as of March 31, 2018, our disclosure controls and procedures were effective at the reasonable assurance level.

Changes in Internal Control over Financial Reporting

During the quarter ended March 31, 2018, we implemented certain internal controls in connection with our adoption of Topic 606.  There were no other changes in our internal control over financial reporting during the first quarter of 2018, as such term is defined in Rules 13a-15(f) and 15(d)-15(f) promulgated under the Securities Exchange Act of 1934, that have materially affected, or are reasonably likely to materially affect, our internal control over financial reporting.

PART II. OTHER INFORMATION

Item 1. Legal Proceedings

In the ordinary course of business, we are from time to time involved in lawsuits, claims, investigations, proceedings, and threats of litigation relating to intellectual property, commercial arrangements, employment and other matters. While the outcome of these proceedings and claims cannot be predicted with certainty, as of March 31, 2018, we were not party to any legal or arbitration

34

proceedings that may have, or have had in the recent past, significant effects on our financial position. No governmental proceedings are pending or, to our knowledge, contemplated against us. We are not a party to any material proceedings in which any director, member of executive management or affiliate of ours is either a party adverse to us or our subsidiaries or has a material interest adverse to us or our subsidiaries.

Item 1A. Risk Factors

An investment in shares of our common stock involves a high degree of risk. You should carefully consider the following information about these risks, together with the other information appearing elsewhere in this Quarterly Report on Form 10-Q, including our financial statements and related notes hereto, before deciding to invest in our common stock. The occurrence of any of the following risks could have a material adverse effect on our business, financial condition, results of operations and future growth prospects. In these circumstances, the market price of our common stock could decline, and you may lose all or part of your investment.

Those risk factors below denoted with a “*” are newly added or have been materially updated from our Annual Report on 10-K filed with the Securities and Exchange Commission, or the SEC, on February 21, 2018.

Risks related to the discovery and development of our product candidates

Our gene therapy product candidates are based on a novel technology, which makes it difficult to predict the time and cost of product candidate development and subsequently obtaining regulatory approval.  Only a few gene therapy products have been approved in the United States and European Union, or EU.

We have concentrated our therapeutic product research and development efforts on our gene therapy platform, and our future success depends on the successful development of this therapeutic approach. There can be no assurance that any development problems we experience in the future related to our gene therapy platform will not cause significant delays or unanticipated costs, or that such development problems can be solved. We may also experience delays in developing a sustainable, reproducible and commercial-scale manufacturing process or transferring that process to commercial partners, which may prevent us from completing our clinical studies or commercializing our products on a timely or profitable basis, if at all.

In addition, the clinical study requirements of the U.S. Food and Drug Administration, or FDA, the European Medicines Agency, or EMA, and other regulatory agencies and the criteria these regulators use to determine the safety and efficacy of a product candidate vary substantially according to the type, complexity, novelty and intended use and market of the potential products. The regulatory approval process for novel product candidates such as ours can be more expensive and take longer than for other, better known or more extensively studied pharmaceutical or other product candidates. Currently, only a few gene therapy products have been approved in the Western world, including Spark’s gene therapy product, which received approval from the FDA in 2017, Orchard Therapeutic’s Strimvelis, and Novartis’s and Gilead’s CAR-T therapies, which received approval from the FDA in 2017. Given the few precedents of approved gene therapy products, it is difficult to determine how long it will take or how much it will cost to obtain regulatory approvals for our product candidates in the United States, the EU or other jurisdictions. Approvals by the EMA and the European Commission may not be indicative of what the FDA may require for approval.

Regulatory requirements governing gene and cell therapy products have evolved and may continue to change in the future. For example, the FDA has established the Office of Cellular, Tissue and Gene Therapies within its Center for Biologics Evaluation and Research, or CBER, to consolidate the review of gene therapy and related products, and the Cellular, Tissue and Gene Therapies Advisory Committee to advise CBER on its review. Gene therapy clinical studies conducted at institutions that receive funding for recombinant DNA research from the U.S. National Institutes of Health, or NIH, are also subject to review by the NIH Office of Biotechnology Activities’ Recombinant DNA Advisory Committee, or RAC. Although the FDA decides whether individual gene therapy protocols may proceed, the RAC review process can impede the initiation of a clinical study, even if the FDA has reviewed the study and approved its initiation. Clinical trial sites in the United States that receive NIH funding for research involving recombinant or synthetic nucleic acid molecules are required to follow RAC recommendations, or risk losing NIH funding for such research or needing NIH pre-approval before conducting such research. In addition, the FDA can put an investigational new drug application, or IND, on clinical hold if the information in an IND is not sufficient to assess the risks in pediatric patients. Before a clinical study can begin at any institution, that institution’s institutional review board, or IRB, and its Institutional Biosafety Committee will have to review the proposed clinical study to assess the safety of the study. Moreover, serious adverse events or developments in clinical trials of gene therapy product candidates conducted by others may cause the FDA or other regulatory bodies to initiate a clinical hold on our clinical trials or otherwise change the requirements for approval of any of our product candidates.

These regulatory review agencies, committees and advisory groups and the new requirements and guidelines they promulgate may lengthen the regulatory review process, require us to perform additional or larger studies, increase our development costs, lead to

35

changes in regulatory positions and interpretations, delay or prevent approval and commercialization of these treatment candidates or lead to significant post-approval studies, limitations or restrictions. As we advance our product candidates, we will be required to consult with these regulatory and advisory groups and comply with applicable requirements and guidelines. If we fail to do so, we may be required to delay or discontinue development of our product candidates. Delay or failure to obtain, or unexpected costs in obtaining, the regulatory approval necessary to bring a potential product to market could decrease our ability to generate sufficient product revenue to maintain our business.

We may find it difficult to enroll patients in our clinical studies, which could delay or prevent clinical studies of our product candidates.

Identifying and qualifying patients to participate in clinical studies of our product candidates is critical to our success. The timing of our clinical studies depends on the speed at which we can recruit eligible patients to participate in testing our product candidates. We have experienced delays in some of our clinical studies, and we may experience similar delays in the future. If patients are unwilling to participate in our gene therapy studies because of negative publicity from adverse events in the biotechnology or gene therapy industries or for other reasons, including competitive clinical studies for similar patient populations, the timeline for recruiting patients, conducting studies and obtaining regulatory approval of potential products may be delayed. These delays could result in increased costs, delays in advancing our product development, delays in testing the effectiveness of our technology or termination of the clinical studies altogether.

We may not be able to identify, recruit and enroll a sufficient number of patients, or those with required or desired characteristics to achieve diversity in a study, to complete our clinical studies in a timely manner. Patient enrollment is affected by factors including:

In particular, each of the conditions for which we plan to evaluate our current hematopoietic stem cell, or HSC, product candidates are rare genetic disorders with limited patient pools from which to draw for clinical studies. Further, because newborn screening for CALD is not widely adopted, and it can be difficult to diagnose CALD in the absence of a genetic screen, we may have difficulty finding patients who are eligible to participate in our study. The eligibility criteria of our clinical studies will further limit the pool of available study participants. Additionally, the process of finding and diagnosing patients may prove costly. Finally, our treatment process requires that the procurement of autologous cells from subjects be conducted where the cells can be shipped to a transduction facility within the required timelines, as the HSCs and T cells, in the case of our oncology product candidate, have limited viability following harvest.

Our current product candidates are being developed to treat severe genetic diseases and certain cancers. We plan to seek initial marketing approval in the United States and the European Union. We may not be able to initiate or continue clinical studies if we cannot enroll a sufficient number of eligible patients to participate in the clinical studies required by the FDA or the EMA or other regulatory agencies. Our ability to successfully initiate, enroll and complete a clinical study in any foreign country is subject to numerous risks unique to conducting business in foreign countries, including:

36

If we have difficulty enrolling a sufficient number of patients to conduct our clinical studies as planned, we may need to delay, limit or terminate ongoing or planned clinical studies, any of which would have an adverse effect on our business.

We may encounter substantial delays in our clinical studies or we may fail to demonstrate safety and efficacy to the satisfaction of applicable regulatory authorities.

Before obtaining marketing approval from regulatory authorities for the sale of our product candidates, we must conduct extensive clinical studies to demonstrate the safety, purity and potency, or efficacy, of the product candidates in humans. Clinical testing is expensive, time-consuming and uncertain as to outcome. We cannot guarantee that any clinical studies will be conducted as planned or completed on schedule, if at all. A failure of one or more clinical studies can occur at any stage of testing. Events that may prevent successful or timely completion of clinical development include:

Any inability to successfully complete preclinical and clinical development could result in additional costs to us or impair our ability to generate revenues from product sales, regulatory and commercialization milestones and royalties. In addition, if we make manufacturing or formulation changes to our product candidates, we may need to conduct additional studies to demonstrate comparability of our modified product candidates to earlier versions. Clinical study delays could also shorten any periods during which we may have the exclusive right to commercialize our product candidates or allow our competitors to bring products to market before we do, which could impair our ability to successfully commercialize our product candidates and may harm our business and results of operations.

If the results of our clinical studies are inconclusive or if there are safety concerns or adverse events associated with our product candidates, we may:

37

Treatment with our gene therapy product candidates involves chemotherapy and myeloablative treatments, which can cause side effects or adverse events that are unrelated to our product candidates, but may still impact the success of our clinical studies. Additionally, our product candidates could potentially cause other adverse events that have not yet been predicted. The inclusion of critically ill patients in our clinical studies may result in deaths or other adverse medical events due to other therapies or medications that such patients may be using, or the progression of their disease. As described above, any of these events could prevent us from achieving or maintaining market acceptance of our product candidates and impair our ability to commercialize our products.

We have not completed any clinical studies of our current product candidates. Initial success in our ongoing clinical studies may not be indicative of results obtained when these studies are completed. Furthermore, success in early clinical studies may not be indicative of results obtained in later studies.

Our product candidates first initiated evaluation in human clinical studies in 2013, and we may experience unexpected results in the future. Results from previous or ongoing studies are not necessarily predictive of our future clinical study results, and initial or interim results may not continue or be confirmed upon completion of the study. There is limited data concerning long-term safety and efficacy following treatment with our gene therapy and T cell-based product candidates. These data, or other positive data, may not continue or occur for these subjects or for any future subjects in our ongoing or future clinical studies, and may not be repeated or observed in ongoing or future studies involving our product candidates. For instance, while patients with TDT or severe SCD who have been treated with our LentiGlobin product candidate may experience a reduction or temporary elimination of transfusion support, there can be no assurance that they will not require transfusion support in the future. Similarly, patients with relapsed/refractory multiple myeloma who have been treated with the bb2121 or the bb21217 product candidate may experience disease progression. Furthermore, our product candidates may also fail to show the desired safety and efficacy in later stages of clinical development despite having successfully advanced through initial clinical studies. There can be no assurance that any of these studies will ultimately be successful or support further clinical advancement or regulatory approval of our product candidates.

There is a high failure rate for drugs and biologics proceeding through clinical studies. A number of companies in the pharmaceutical and biotechnology industries have suffered significant setbacks in later stage clinical studies even after achieving promising results in earlier stage clinical studies. Data obtained from preclinical and clinical activities are subject to varying interpretations, which may delay, limit or prevent regulatory approval. In addition, regulatory delays or rejections may be encountered as a result of many factors, including changes in regulatory policy during the period of product development.

Patients with different genotypes of TDT may experience different outcomes from treatment with our product candidates, which may result in the delay of our clinical development and commercialization plans.

Initial results from our clinical studies of LentiGlobin suggest that patients with TDT and a non-β⁰/β⁰ genotype experienced better outcomes to treatment with our LentiGlobin product candidate than patients with TDT and a β⁰/β⁰ genotype. Consequently, we expect to seek FDA approval of our LentiGlobin product candidate initially for the treatment of patients with TDT and a non-β⁰/β⁰ genotype. In order to support an application for FDA approval of our LentiGlobin product candidate in patients with TDT and a β⁰/β⁰ genotype, we initiated the HGB-212 study, but we do not know if or when our LentiGlobin product candidate may be commercially available to patients with all genotypes.

* The results from our Starbeam Study may not be sufficiently robust to support the submission of marketing approval for our Lenti-D product candidate.

The FDA has previously advised us that our Starbeam Study, which is a single-arm, open-label study to evaluate the safety and efficacy of our Lenti-D product candidate to halt the progression of CALD, may not be deemed to be a pivotal study or may not provide sufficient support for a Biologics License Application, or BLA, submission. The FDA normally requires two pivotal clinical studies to approve a drug or biologic product. The FDA typically does not consider a single clinical study to be adequate to serve as a pivotal study unless it is, among other things, well-controlled and demonstrates a clinically meaningful effect on mortality, irreversible morbidity, or prevention of a disease with potentially serious outcome, and a confirmatory study would be practically or ethically impossible. Due to the nature of CALD and the limited number of patients with this condition, we believe a placebo-controlled and blinded study is not practicable for ethical and other reasons. However, it is still possible that, even if we achieve favorable results in the Starbeam Study, the FDA may require us to enroll additional subjects or conduct additional clinical studies, possibly involving a larger sample size or a different clinical study design, particularly if the FDA does not find the results from the Starbeam Study to be sufficiently persuasive to support a BLA submission. The FDA may also require that we conduct a longer follow-up period of subjects treated with our Lenti-D product candidate prior to accepting our BLA submission.

38

The Starbeam Study was not designed to achieve a statistically significant efficacy determination. Rather, we anticipate that the safety and efficacy of our Lenti-D product candidate will be evaluated in light of the data collected in our observational ALD-103 study. We expect that the FDA will assess the totality of the safety and efficacy data from our CALD clinical studies in reviewing any future BLA submission for our Lenti-D product candidate. Based on this assessment, the FDA may require that we conduct additional clinical studies prior to submitting or approving a BLA for this indication.

It is possible that the FDA or the EMA may not consider the results of this study to be sufficient for approval of our Lenti-D product candidate for this indication. If the FDA or the EMA requires additional studies, we would incur increased costs and delays in the marketing approval process, which may require us to expend more resources than we have available. In addition, it is possible that the FDA and the EMA may have divergent opinions on the elements necessary for a successful BLA and Marketing Authorization Application, or MAA, respectively, which may cause us to alter our development, regulatory and/or commercialization strategies.

We cannot be certain that our Northstar-2 Study in patients with TDT and a non-β⁰/β⁰ genotype, or our Northstar-3 Study in patients with TDT and a β⁰/β⁰ genotype, together with data from our Northstar Study and HGB-205 study, will be sufficient to form the basis for a BLA submission for our LentiGlobin product candidate.

In general, the FDA requires the successful completion of two pivotal trials to support approval of a BLA, but in certain circumstances, will approve a BLA based on only one pivotal trial. If successful, we believe the results from our ongoing Northstar-2 Study, together with data from our Northstar Study and ongoing HGB-205 study, could be sufficient to form the basis for a BLA submission for our LentiGlobin product candidate to treat adult and adolescent patients with TDT and a non-β⁰/β⁰ genotype. In addition, if successful, we believe the results from our Northstar-3 Study, together with data from our Northstar Study and ongoing Northstar-2 Study, could be sufficient to form the basis for a BLA supplement submission for our LentiGlobin product candidate to treat patients with TDT and a β⁰/β⁰ genotype. However, it should be noted that our ability to submit and obtain approval of a BLA is ultimately an FDA review decision, which will be dependent upon the data available at such time, and the available data may not be sufficiently robust from a safety and/or efficacy perspective to support the submission or approval of a BLA. Depending on the outcome of these ongoing clinical studies, the FDA may require that we conduct additional or larger pivotal trials before we can submit or obtain approval for a BLA for our LentiGlobin product candidate for the treatment of TDT.

There can be no assurance that we will ultimately receive conditional marketing approval of our LentiGlobin product candidate in the European Union, or the nature of the conditions that would be imposed on us if conditionally approved.

The EMA Adaptive Pathways pilot program in which we are participating is intended to facilitate either an initial approval in a well-defined patient subgroup with a high medical need and subsequent widening of the indication to a larger patient population through iterative extension of the indication, or an early regulatory approval (e.g. conditional approval), which is prospectively planned, and where uncertainty is reduced through the collection of post-approval data on the use in of medicinal product in patients. Based on our discussions with the EMA, we believe that we may be able to seek conditional approval for our LentiGlobin product candidate, with our refined manufacturing process, for the treatment of adult and adolescent subjects with TDT and a non- β⁰/β⁰ genotype on the basis of the totality of the clinical data from our ongoing studies with LentiGlobin.  For efficacy, we believe that the Northstar Study and supportive ongoing HGB-205 study, together with the data available from our ongoing Northstar-2 Study and our long-term follow-up study LTF-303, could support the filing of a marketing authorization application in the European Union. This plan is contingent upon all of the studies conducted in patients with TDT with the LentiGlobin product candidate demonstrating sufficient efficacy and safety, and in particular, transfusion independence and reduction in transfusion requirements, for efficacy analyses in the Northstar, HGB-205 and Northstar-2 studies.

However, it should be noted that the EMA Adaptive Pathways program is a pilot program, and as such there is limited information and precedent regarding the potential outcomes for sponsors that participate in this program. Whether our LentiGlobin product candidate is eligible for conditional approval will ultimately be determined at the discretion of the EMA and will be dependent upon the data available at such time, and the available data may not be sufficiently robust from a safety and/or efficacy perspective to support conditional approval. Depending on the outcome of our planned and ongoing clinical trials, the EMA may require that we conduct additional or larger clinical trials before our LentiGlobin product candidate is eligible for conditional approval. Even if conditional approval is obtained, the conditions to be imposed on us under this program are unknown and will be imposed at the time of any such conditional approval.

* Changes in our manufacturing processes may cause delays in our clinical development and commercialization plans.

The manufacturing processes for our lentiviral vectors and our product candidates are complex. We have developed and have implemented an improved manufacturing process of our LentiGlobin drug product that is being administered in our Northstar-2 Study in patients with TDT and a non-β⁰/β⁰ genotype, our amended ongoing HGB-206 study in patients with severe SCD, and our Northstar-3 Study in patients with TDT and a β⁰/β⁰ genotype. The LentiGlobin drug product manufactured using the improved manufacturing

39

process may not lead to similar or improved efficacy or safety results in subjects, as compared to the LentiGlobin drug product used in the Northstar Study, the ongoing HGB-205 study, or the HGB-206 study under the original protocol.

As we develop a commercial-scale manufacturing process for our LentiGlobin and Lenti-D product candidates, we are implementing improvements to the manufacturing process for both producing our lentiviral vectors and for our product candidates on a continual basis. In some circumstances, changes in the manufacturing process may require us to perform additional comparability studies or to collect additional clinical data from patients prior to undertaking additional clinical studies or filing for regulatory approval. These requirements may lead to delays in our clinical development and commercialization plans.

In previous clinical studies involving viral vectors for gene therapy, some subjects experienced serious adverse events, including the development of leukemia due to vector-related insertional oncogenesis.  If our vectors demonstrate a similar effect, we may be required to halt or delay further clinical development of our product candidates.

A significant risk in any gene therapy product based on viral vectors is that the vector will insert in or near cancer-causing oncogenes leading to uncontrolled clonal proliferation of mature cancer cells in the patient.  For example, in 2003, 20 subjects treated for X-linked severe combined immunodeficiency in two gene therapy studies using a murine, or mouse-derived, gamma-retroviral vector showed correction of the disease, but the studies were terminated after five subjects developed leukemia (four of whom were subsequently cured). The cause of these adverse events was shown to be insertional oncogenesis, which is the process whereby the corrected gene inserts in or near a gene that is important in a critical cellular process like growth or division, and this insertion results in the development of a cancer (often leukemia). Using molecular diagnostic techniques, it was determined that clones from these subjects showed retrovirus insertion in proximity to the promoter of the LMO2 proto-oncogene. Earlier generation retroviruses like the one used in these two studies have been shown to preferentially integrate in regulatory regions of genes that control cell growth.

These well-publicized adverse events led to the development of new viral vectors, such as lentiviral vectors, with improved safety profiles and also the requirement of enhanced safety monitoring in gene therapy clinical trials, including periodic analyses of the therapy’s genetic insertion sites. In published studies, lentiviral vectors have demonstrated an improved safety profile over gamma-retroviral vectors, with no disclosed events of gene therapy-related adverse events, which we believe is due to a number of factors including the tendency of these vectors to integrate within genes rather than in areas that control gene expression, as well as their lack of strong viral enhancers. However, it should be noted that in our Phase I/II study (the LG001 Study) of autologous HSCs transduced ex vivo using an earlier generation of our LentiGlobin vector, called HPV569, we initially observed in one subject that a disproportionate number of the cells expressing our functional gene had the same insertion site. Tests showed that this partial clonal dominance contained an insertion of the functional gene in the HMGA2 gene that persisted for a period of two to three years. Although there was some initial concern that the observed clonal dominance might represent a pre-leukemic event, there have been no adverse clinical consequences of this event, or any signs of cancer, in over seven years since the observation was made. The presence of the HMGA2 clone has steadily declined in this subject over time to the point that it is no longer the most common clone observed in this subject.

Notwithstanding the historical data regarding the potential safety improvements of lentiviral vectors, the risk of insertional oncogenesis remains a significant concern for gene therapy and we cannot assure that it will not occur in any of our ongoing or planned clinical studies. There is also the potential risk of delayed adverse events following exposure to gene therapy products due to persistent biological activity of the genetic material or other components of products used to carry the genetic material. The FDA has stated that lentiviral vectors possess characteristics that may pose high risks of delayed adverse events. If any such adverse events occur, further advancement of our clinical studies could be halted or delayed, which would have a material adverse effect on our business and operations.

In previous clinical studies involving T cell-based immunotherapies, some subjects experienced serious adverse events. Our T cell-based immunotherapy product candidates may demonstrate a similar effect or have other properties that could halt their clinical development, prevent their regulatory approval, limit their commercial potential, or result in significant negative consequences.

The bb2121 and bb21217 product candidates are chimeric antigen receptor, or CAR, T cell-based immunotherapy. In previous and ongoing clinical studies involving CAR T cell products, many subjects experienced side effects such as neurotoxicity and cytokine release syndrome, which have in some cases resulted in clinical holds in ongoing clinical trials of CAR T product candidates. There have been life threatening events related to severe neurotoxicity and cytokine release syndrome, requiring intense medical intervention such as intubation or pressor support, and in several cases, resulted in death. Severe neurotoxicity is a condition that is currently defined clinically by cerebral edema, confusion, drowsiness, speech impairment, tremors, seizures, or other central nervous system side effects, when such side effects are serious enough to lead to intensive care. In some cases, severe neurotoxicity was thought to be associated with the use of certain lymphodepletion regimens used prior to the administration of the CAR T cell products. Cytokine release syndrome is a condition that is currently defined clinically by certain symptoms related to the release of cytokines, which can include fever, chills, low blood pressure, when such side effects are serious enough to lead to intensive care with mechanical

40

ventilation or significant vasopressor support. The exact cause or causes of cytokine release syndrome and severe neurotoxicity in connection with treatment of CAR T cell products is not fully understood at this time. In addition, subjects have experienced other adverse events in these studies, such as a reduction in the number of blood cells (in the form of neutropenia, thrombocytopenia, anemia or other cytopenias), febrile neutropenia, chemical laboratory abnormalities (including elevated liver enzymes), and renal failure.

Undesirable side effects caused by the bb2121 or bb21217 product candidate, other CAR T product candidates targeting BCMA, or our other T cell-based immunotherapy product candidates, could cause us or regulatory authorities to interrupt, delay or halt clinical studies and could result in a more restrictive label or the delay or denial of regulatory approval by the FDA or other comparable foreign regulatory authorities. Results of our studies could reveal a high and unacceptable severity and prevalence of side effects or unexpected characteristics. Treatment-related side effects could also affect patient recruitment or the ability of enrolled subjects to complete the studies or result in potential product liability claims. In addition, these side effects may not be appropriately recognized or managed by the treating medical staff, as toxicities resulting from T cell-based immunotherapies are not normally encountered in the general patient population and by medical personnel. We expect to have to train medical personnel regarding our T cell-based immunotherapy product candidates to understand their side effects for both our planned clinical trials and upon any commercialization of any T cell-based immunotherapy product candidates. Inadequate training in recognizing or managing the potential side effects of T cell-based immunotherapy product candidates could result in patient deaths. Any of these occurrences may harm our business, financial condition and prospects significantly.  

Even if we complete the necessary preclinical and clinical studies, we cannot predict when or if we will obtain regulatory approval to commercialize a product candidate or the approval may be for a more narrow indication than we expect.

We cannot commercialize a product until the appropriate regulatory authorities have reviewed and approved the product candidate. Even if our product candidates demonstrate safety and efficacy in clinical studies, the regulatory agencies may not complete their review processes in a timely manner, or we may not be able to obtain regulatory approval. Additional delays may result if an FDA Advisory Committee or other regulatory advisory group or authority recommends non-approval or restrictions on approval. In addition, we may experience delays or rejections based upon additional government regulation from future legislation or administrative action, or changes in regulatory agency policy during the period of product development, clinical studies and the review process. Regulatory agencies also may approve a treatment candidate for fewer or more limited indications than requested or may grant approval subject to the performance of post-marketing studies. In addition, regulatory agencies may not approve the labeling claims that are necessary or desirable for the successful commercialization of our treatment candidates. For example, the development of our product candidates for pediatric use is an important part of our current business strategy, and if we are unable to obtain regulatory approval for the desired age ranges, our business may suffer.

Even if we obtain regulatory approval for a product candidate, our products will remain subject to regulatory scrutiny.

Even if we obtain regulatory approval in a jurisdiction, the regulatory authority may still impose significant restrictions on the indicated uses or marketing of our product candidates, or impose ongoing requirements for potentially costly post-approval studies, post-market surveillance or patient or drug restrictions. For example, the FDA typically advises that patients treated with gene therapy undergo follow-up observations for potential adverse events for a 15-year period. Additionally, the holder of an approved BLA is obligated to monitor and report adverse events and any failure of a product to meet the specifications in the BLA. The holder of an approved BLA must also submit new or supplemental applications and obtain FDA approval for certain changes to the approved product, product labeling or manufacturing process. Advertising and promotional materials must comply with FDA rules and are subject to FDA review, in addition to other potentially applicable federal and state laws.

In addition, product manufacturers and their facilities are subject to payment of user fees and continual review and periodic inspections by the FDA and other regulatory authorities for compliance with good manufacturing practices, or GMP, and adherence to commitments made in the BLA. If we or a regulatory agency discovers previously unknown problems with a product such as adverse events of unanticipated severity or frequency, or problems with the facility where the product is manufactured, a regulatory agency may impose restrictions relative to that product or the manufacturing facility, including requiring recall or withdrawal of the product from the market or suspension of manufacturing.

If we fail to comply with applicable regulatory requirements following approval of any of our product candidates, a regulatory agency may:

41