ENANTA PHARMACEUTICALS INC - Quarter Report: 2016 March (Form 10-Q)

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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Form 10-Q

For the quarterly period ended March 31, 2016

OR

Commission File Number 001-35839

ENANTA PHARMACEUTICALS, INC.

(Exact name of registrant as specified in its charter)

500 Arsenal Street

Watertown, Massachusetts 02472

(617) 607-0800

(Address, including zip code, and telephone number, including area code, of registrant’s principal executive offices)

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  x    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  x    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” and “smaller reporting company” in Rule 12b-2 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  x

The number of shares of the registrant’s Common Stock, $0.01 par value, outstanding as of May 1, 2016, was 18,957,233 shares.

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ENANTA PHARMACEUTICALS, INC.

FORM 10-Q — Quarterly Report

For the Quarterly Period Ended March 31, 2016

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PART I—FINANCIAL INFORMATION

ENANTA PHARMACEUTICALS, INC.

CONSOLIDATED BALANCE SHEETS

(unaudited)

(in thousands, except share and per share amounts)

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

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ENANTA PHARMACEUTICALS, INC.

CONSOLIDATED STATEMENTS OF OPERATIONS

(unaudited)

(in thousands, except share and per share amounts)

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

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ENANTA PHARMACEUTICALS, INC.

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME

(unaudited)

(in thousands)

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

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ENANTA PHARMACEUTICALS, INC.

CONSOLIDATED STATEMENTS OF CASH FLOWS

(unaudited)

(in thousands)

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

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ENANTA PHARMACEUTICALS, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS

(unaudited)

(Amounts in thousands, except share and per share data)

Enanta Pharmaceuticals, Inc. (the “Company”), incorporated in Delaware in 1995, is a research and development-focused biotechnology company that uses its robust chemistry-driven approach and drug discovery capabilities to create small molecule drugs primarily for the treatment of viral infections and liver diseases. The Company’s research and development is currently focused on four disease targets: hepatitis C virus (“HCV”); hepatitis B virus (“HBV”); non-alcoholic steatohepatitis (“NASH”); and respiratory syncytial virus (“RSV”).

The Company is subject to risks common to companies in the biotechnology industry including, but not limited to, the uncertainties of research and development, competition from technological innovations of others, dependence on collaborative arrangements, protection of proprietary technology, dependence on key personnel, compliance with government regulations and the need to obtain additional financing. Product candidates currently under development will require significant additional research and development efforts, including extensive preclinical and clinical testing and regulatory approval, prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel infrastructure, and extensive compliance reporting capabilities.

Unaudited Interim Financial Information

The consolidated balance sheet at September 30, 2015 was derived from audited financial statements, but does not include all disclosures required by accounting principles generally accepted in the United States of America (“GAAP”). The accompanying unaudited consolidated financial statements as of March 31, 2016 and for the three and six months ended March 31, 2016 and 2015 have been prepared by the Company, pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”) for interim financial statements. Certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. These financial statements should be read in conjunction with the Company’s audited financial statements and the notes thereto included in the Company’s Annual Report on Form 10-K for the year ended September 30, 2015.

In the opinion of management, all adjustments, consisting only of normal recurring adjustments necessary for a fair statement of the Company’s financial position as of March 31, 2016 and results of operations for the three and six months ended March 31, 2016 and 2015 and cash flows for the six months ended March 31, 2016 and 2015 have been made. The results of operations for the three and six months ended March 31, 2016 are not necessarily indicative of the results of operations that may be expected for subsequent quarters or the year ending September 30, 2016.

The accompanying consolidated financial statements have been prepared in conformity with GAAP. All dollar amounts in the consolidated financial statements and in the notes to the consolidated financial statements, except share and per share amounts, are in thousands unless otherwise indicated.

For the Company’s Significant Accounting Policies refer to its Annual Report on Form 10-K for the fiscal year ended September 30, 2015.

Use of Estimates

The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the consolidated financial statements, and the reported amounts of revenues and expenses during the reporting period. Significant estimates and assumptions reflected in these consolidated financial statements include, but are not limited to, management’s judgments of separate units of accounting and best estimate of selling price of those units of accounting within its revenue arrangements; valuation of stock-based awards; the useful lives of property and equipment; and the accounting for income taxes, including uncertain tax positions and the valuation of net deferred tax assets. Estimates are periodically reviewed in light of changes in circumstances, facts and experience. Actual results could differ from the Company’s estimates.

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Recently Issued Accounting Pronouncements

In May 2014, the Financial Accounting Standards Board (the “FASB”) issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606), which supersedes all existing revenue recognition requirements, including most industry-specific guidance. The new standard requires a company to recognize revenue when it transfers goods or services to customers in an amount that reflects the consideration that the company expects to receive for those goods or services. In addition, in March 2016, the FASB issued ASU No. 2016-08, Revenue from Contracts with Customers: Principal versus Agent Considerations. The amendment includes indicators to assist an entity in determining whether it controls a specified good or service before it is transferred to the customers. The FASB also issued ASU No. 2016-10, Revenue from Contracts with Customers: Identifying Performance Obligations and Licensing in April 2016 to clarify guidance from ASU 2014-09. Specifically, this amendment addresses an entity’s identification of its performance obligations in a contract, as well as an entity’s evaluation of the nature of its promise to grant a license of intellectual property and whether or not that revenue is recognized over time or at a point in time. These new standards will be effective for the Company on October 1, 2018. The Company is currently evaluating the potential impact that Topic 606 may have on its financial position and results of operations.

In November 2015, the FASB issued ASU No. 2015-17, Balance Sheet Classification of Deferred Taxes (“ASU 2015-17”), which simplifies the presentation of deferred income taxes by eliminating the need for entities to separate deferred income tax liabilities and assets into current and noncurrent amounts in a classified statement of financial position. This amendment is effective for the Company in the fiscal year beginning October 1, 2017, but early adoption is permissible. The Company is currently evaluating the potential impact that ASU 2015-17 may have on its financial position.

In February 2016, the FASB issued ASU No. 2016-02, Leases (“ASU 2016-02”), which will replace the existing guidance in ASC 840, “Leases.” The updated standard aims to increase transparency and comparability among organizations by requiring lessees to recognize lease assets and lease liabilities on the balance sheet and requiring disclosure of key information about leasing arrangements. This amendment is effective for the Company in the fiscal year beginning October 1, 2019, but early adoption is permissible. The Company is currently evaluating the potential impact that ASU 2016-02 may have on its financial position and results of operations.

In March 2016, the FASB issued ASU No. 2016-09, Improvements to Employee Share-Based Payment Accounting (“ASU 2016-09”), which intends to simplify several aspects of accounting for share-based payment transactions, including the income tax consequences, classification of awards as either equity or liabilities, an option to recognize gross stock compensation expense with actual forfeitures recognized as they occur, as well as certain classifications on the statement of cash flows. This amendment is effective for the Company in the fiscal year beginning October 1, 2017, but early adoption is permissible. The Company is currently evaluating the potential impact that ASU 2016-92 may have on its financial position and results of operations.

Other accounting standards that have been issued or proposed by the FASB or other standards-setting bodies that do not require adoption until a future date are not expected to have a material impact on the Company’s financial statements upon adoption.

The following tables present information about the Company’s financial assets and liabilities that were subject to fair value measurement on a recurring basis as of March 31, 2016 and September 30, 2015 and indicate the fair value hierarchy of the valuation inputs utilized to determine such fair value:

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During the three and six months ended March 31, 2016 and 2015, there were no transfers between Level 1, Level 2 and Level 3.

As of March 31, 2016 and September 30, 2015, respectively, the warrant liability was comprised of the value of warrants for the purchase of Series 1 nonconvertible preferred stock measured at fair value. The outstanding Series 1 nonconvertible preferred stock was also measured at fair value. The fair value of both of these instruments was based on significant inputs not observable in the market, which represented a Level 3 measurement within the fair value hierarchy. The Company utilized a probability-weighted valuation model which takes into consideration various outcomes that may require the Company to transfer assets upon exercise. Changes in the fair value of the warrant liability and Series 1 nonconvertible preferred stock are recognized in the consolidated statements of operations.

As of March 31, 2016 and September 30, 2015, the recurring Level 3 fair value measurements of the Company’s warrant liability and Series 1 nonconvertible preferred stock using probability-weighted discounted cash flow include the following significant unobservable inputs:

March 31, 2016

September 30, 2015

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The following table provides a rollforward of the aggregate fair values of the Company’s warrants for the purchase of Series 1 nonconvertible preferred stock and the outstanding Series 1 nonconvertible preferred stock for which fair value is determined by Level 3 inputs:

As of March 31, 2016 and September 30, 2015, the fair value of available-for-sale marketable securities by type of security was as follows:

As of March 31, 2016, marketable securities consisted of investments that mature within one year, with the exception of certain corporate bonds, which have maturities within three years and an aggregate fair value of $25,224.

Accrued expenses and other current liabilities as well as other long-term liabilities consisted of the following as of March 31, 2016 and September 30, 2015:

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AbbVie Collaboration

The Company has a Collaborative Development and License Agreement (the “AbbVie Agreement”), as amended, with AbbVie Inc. to identify, develop and commercialize HCV NS3 and NS3/4A protease inhibitor compounds, including paritaprevir, under which it has received license payments, proceeds from a sale of preferred stock, research funding payments, milestone payments and royalties totaling $367,000 through March 31, 2016. As of March 31, 2016 the Company is eligible to receive additional milestone payments totaling up to $80,000 upon AbbVie’s achievement of commercialization regulatory approval in the U.S. and other selected world markets for any additional protease inhibitor commercialized by AbbVie. Since the Company completed all its performance obligations under the AbbVie Agreement by the end of fiscal 2011, any milestone payments received since then have been and will be recognized as revenue when the milestones are achieved by AbbVie. The Company is also receiving annually tiered royalties per product ranging from the low double digits up to twenty percent, or on a blended basis from the low double digits up to the high teens, on calendar year net sales by AbbVie allocated to the collaboration’s protease inhibitors. Beginning with each January 1 the cumulative net sales of a given royalty-bearing product start at zero for purposes of calculating the tiered royalties.

During the three and six months ended March 31, 2016, the Company earned and recognized milestone revenue of $0 and $30,000, respectively, upon AbbVie’s achievement of commercialization regulatory approval of a paritaprevir-containing regimen in Japan. During the three and six months ended March 31, 2015, the Company earned and recognized milestone revenue of $50,000 and $125,000, respectively, upon AbbVie’s achievement of commercialization regulatory approval of VIEKIRAX in Europe in January 2015 and VIEKIRA PAK in the U.S in December 2014.

In October and November 2010, the Company issued warrants to purchase up to a total of 1,999,989 shares of Series 1 nonconvertible preferred stock, which expire on October 4, 2017. As these warrants are free-standing financial instruments that may require the Company to transfer assets upon exercise, these warrants are classified as liabilities. The Company is required to remeasure the fair value of these preferred stock warrants at each reporting date, with any adjustments recorded within the change in fair value of warrant liability included in other income (expense), net, in the consolidated statement of operations.

The Company may grant stock-based awards under its existing 2012 Equity Incentive Plan (the “2012 Plan”) and its Employee Stock Purchase Plan (the “ESPP”). The Company also has outstanding stock-based awards under its 1995 Equity Incentive Plan (the “1995 Plan”), but is no longer granting awards under this plan. As of March 31, 2016, 524,960 shares of common stock are available for issuance under the 2012 Plan based on the target number of units awarded, none of which have yet vested. As of March 31, 2016, a total of 185,614 shares of common stock are available for issuance under the ESPP. As of March 31, 2016, the Company had not commenced any offering under the ESPP and no shares have been issued.

The Company applies the fair value recognition provisions for all stock-based awards granted or modified in accordance with authoritative guidance. Under this guidance the Company records compensation costs over the requisite service period of the award based on the grant-date fair value. The straight-line method is applied to all grants with service conditions, while the graded vesting method is applied to all grants with both service and performance conditions.

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In December 2015, the Company awarded certain executive officers a total of 50,000 share units consisting of 25,000 performance share units, or PSUs, and 25,000 relative total shareholder return units, or rTSRUs. The number of units represents the target number of shares of common stock that may be earned; however, the actual number of shares that may be earned ranges from 0% to 200% of the target number. The PSUs will vest and result in issuance, or settlement, of common shares, based upon continued employment and achievement of specified research and development milestones on or before December 31, 2017. The aggregate grant date fair value of the 25,000 PSUs ranges between $0 and $1,602. During the three and six months ended March 31, 2016, the Company recorded no compensation expense related to the PSU awards as none of the performance-based targets was probable of being achieved during this period.

The rTSRUs will vest and result in the issuance of common stock based on continuing employment and the relative ranking of the total shareholder return, or TSR, of the Company’s common stock in relation to the TSR of the component companies in the NASDAQ Biotech Index over a two-year period based on a comparison of average closing stock prices in November 2015 and December 2017. The number of market-based rTSRUs awarded represents the target number of shares of common stock that may be earned; however, the actual number of shares that may be earned ranges from 0% to 200% of the target number.

The Company used a Monte Carlo simulation model to estimate that the grant-date fair value of the rTSRUs was $942. The table below sets forth the assumptions used to value the awards and the estimated grant-date fair value:

The fair value related to the rTSRUs will be recorded as compensation expense over the period from date of grant to December 2017 regardless of whether the target relative total shareholder returns are reached.

In addition, in December 2015, the Company awarded an executive officer 5,250 share units consisting of 2,625 PSUs and 2,625 rTSRUs. The number of units represents the target number of shares of common stock that may be earned; however, the actual number of shares that may be earned ranges from 0% to 200% of the target number.

The PSUs will vest and result in issuance, or settlement, of common shares, based upon continued employment and achievement of specified research and development milestones on or before December 31, 2016. The aggregate grant date fair value of the 2,625 PSUs ranges between $0 and $168. During the three and six months ended March 31, 2016, the Company recorded no compensation expense related to the PSU awards as none of the performance-based targets was probable of being achieved during this period.

The rTSRUs will vest and result in the issuance of common stock based on continuing employment and the relative ranking of the total shareholder return, or TSR, of the Company’s common stock in relation to the TSR of the component companies in the NASDAQ Biotech Index over a two-year period based on a comparison of average closing stock prices in December 2014 and December 2016. The number of market-based rTSRUs awarded represents the target number of shares of common stock that may be earned; however, the actual number of shares that may be earned ranges from 0% to 200% of the target number.

The Company used a Monte Carlo simulation model to estimate that the grant-date fair value of the rTSRUs was $44. The table below sets forth the assumptions used to value the awards and the estimated grant-date fair value:

The fair value related to the rTSRUs will be recorded as compensation expense over the period from date of grant to December 2016 regardless of whether the target relative total shareholder returns are reached.

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The Company recognized stock-based compensation expense on all awards in the following expense categories:

As of March 31, 2016, the Company had an aggregate of $26,432 of unrecognized stock-based compensation cost, which is expected to be recognized over a weighted average period of 2.5 years.

Basic and diluted net income (loss) per share attributable to common stockholders was calculated as follows for the three and six months ended March 31, 2016 and 2015:

The impact of dilutive common stock equivalents were excluded from the calculation of diluted net income (loss) per share for the three months ended March 31, 2016 due to the fact that the Company was in a loss position for the period.

As of March 31, 2016 the Company excluded 72,050 and 139,226 of unvested restricted stock units and performance based options, respectively, from the calculation of diluted net income per share attributable to common stockholders as these awards contain performance and market conditions that would not have been achieved as of March 31, 2016 had the measurement period been as of that date.

For the three months ended March 31, 2016 and March 31, 2015, the Company recorded an income tax provision of $1,552 and $20,018, respectively. The income tax provision for the three months ended March 31, 2016 and 2015 was primarily attributable to the tax provision on the earnings of the Company’s domestic operations. During the three months ended March 31, 2016, the Company increased its estimate of its annual effective tax rate for fiscal 2016, which resulted in an income tax provision despite a pre-tax loss for the quarter. For the three months ended March 31, 2015 the Company’s effective tax rate of 41.0% differs from the statutory rate of 35% primarily due to state income taxes and certain expenditures which are permanently not deductible for tax purposes.

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For the six months ended March 31, 2016 and March 31, 2015, the Company recorded an income tax provision of $11,286 and $48,520, respectively, representing an effective tax rate of 31.5% and 40.7%, respectively. For the six months ended March 31, 2016, the Company’s effective tax rate differs from the statutory rate of 35% primarily due to reinstatement of the federal research and development tax credits which are included in the Company’s annual effective tax rate. For the six months ended March 31, 2015, the Company’s effective tax rate differs from the statutory rate of 35% primarily due to state income taxes and certain expenditures which are permanently not deductible for tax purposes.

The Company files tax returns as prescribed by the tax laws of the jurisdictions in which it operates. In the normal course of business, the Company is subject to examination by federal and state jurisdictions, where applicable. There are currently no pending income tax examinations. The Company’s tax years are still open under statute from 2008 to the present. Earlier years may be examined to the extent that tax credit or net operating loss carryforwards are used in future periods.

The Company had an unrecognized tax benefit of $510 and $448 as of March 31, 2016 and September 30, 2015, respectively. Unrecognized tax benefits represent tax positions for which reserves have been established. The Company’s policy is to record interest and penalties related to uncertain tax positions as part of its income tax provision.

Leases

The Company has an office and laboratory lease that expires in September 2022. Payment escalation as specified in the lease agreement is accrued such that rent expense is recognized on a straight-line basis over the term of occupancy. The Company recorded rent expense of $507 and $243 for the three months ended March 31, 2016 and 2015, respectively, and $1,013 and $480 for the six months ended March 31, 2016 and 2015, respectively.

In connection with the lease, the Company has outstanding a $608 letter of credit, collateralized by a money market account. As of March 31, 2016 and September 30, 2015, the Company classified $608 related to the letter of credit as restricted cash. Additionally, the lease, as amended, included a $598 tenant improvement allowance from the landlord, which allowance is accounted for as a capital lease obligation.

Intellectual Property Licenses

The Company has a non-exclusive intellectual property license agreement with a third party, under which the Company is required to pay (1) annual maintenance fees of $105 for each year that the agreement remains in effect, commencing on the first anniversary of the agreement, in order to maintain the right to use the license, and (2) a one-time fee of $50 in each circumstance in which the Company provides the licensed intellectual property to one of its collaborators with the prior consent of the licensor.

The Company also has a non-exclusive license with respect to patents it uses in its HCV research. Under the license, the Company is obligated to pay milestones totaling up to $5,000, plus low single digit royalties, for the development and regulatory approval of each HCV product outside of the Company’s collaboration with AbbVie and any other collaboration it may enter into in the future with a partner that has already licensed these patents. During the six months ended March 31, 2016 the Company made a $500 milestone payment under this license agreement upon its filing to commence clinical development of its cyclophilin inhibitor candidate. During the three and six months ended March 31, 2015, no events triggering such payment occurred.

Litigation and Contingencies Related to Use of Intellectual Property

From time to time, the Company may become subject to legal proceedings, claims and litigation arising in the ordinary course of business. The Company currently is not a party to any threatened or pending litigation. However, third parties might allege that the Company or its collaborators are infringing their patent rights or that the Company is otherwise violating their intellectual property rights. Such third parties may resort to litigation against the Company or its collaborators, which the Company has agreed to indemnify. With respect to some of these patents, the Company expects that it will be required to obtain licenses and could be required to pay license fees or royalties, or both. These licenses may not be available on acceptable terms, or at all. A costly license, or inability to obtain a necessary license, would have a material adverse effect on the Company’s financial condition, results of operations or cash flows. The Company accrues contingent liabilities when it is probable that future expenditures will be made and such expenditures can be reasonably estimated.

Indemnification Agreements

In the ordinary course of business, the Company may provide indemnifications of varying scope and terms to customers, vendors, lessors, business partners, and other parties with respect to certain matters including, but not limited to, losses arising out of breach of such agreements, from services to be provided by the Company, or from intellectual property infringement claims made by third parties. In addition, the Company has entered into indemnification agreements with members of its board of directors and its executive

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officers that will require the Company, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors or officers. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is, in many cases, unlimited. To date, the Company has not incurred any material costs as a result of such indemnifications. In addition, the Company maintains officers and directors insurance coverage. The Company does not believe that the outcome of any claims under indemnification arrangements will have a material effect on its financial position, results of operations or cash flows, and it has not accrued any liabilities related to such obligations in its financial statements as of March 31, 2016.

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ITEM 2. MANAGEMENT’S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS OF OPERATIONS

The following discussion and analysis of our financial condition and results of operations should be read in conjunction with the unaudited consolidated financial statements and notes thereto included elsewhere in this Quarterly Report on Form 10-Q and the audited consolidated financial statements and notes thereto for our fiscal year ended September 30, 2015 included in our Annual Report on Form 10-K for that fiscal year. This Quarterly Report on Form 10-Q contains “forward-looking statements” within the meaning of Section 21E of the Securities Exchange Act of 1934, as amended, or the Exchange Act. These statements are often identified by the use of words such as “may,” “will,” “expect,” “believe,” “anticipate,” “intend,” “could,” “should,” “estimate,” or “continue,” and similar expressions or variations. Such forward-looking statements are subject to risks, uncertainties and other factors that could cause actual results and the timing of certain events to differ materially from future results expressed or implied by such forward-looking statements. Factors that could cause or contribute to such differences include, but are not limited to, those discussed in the section titled “Risk Factors,” set forth in Part II, Item 1A of this Quarterly Report on Form 10-Q. The forward-looking statements in this Quarterly Report on Form 10-Q represent our views as of the date of this Quarterly Report on Form 10-Q. We anticipate that subsequent events and developments will cause our views to change. However, while we may elect to update these forward-looking statements at some point in the future, we have no current intention of doing so except to the extent required by applicable law. You should, therefore, not rely on these forward-looking statements as representing our views as of any date subsequent to the date of this Quarterly Report on Form 10-Q.

Overview

We are a research and development-focused biotechnology company that uses its robust chemistry-driven approach and drug discovery capabilities to create small molecule drugs primarily for the treatment of viral infections and liver diseases. Our research and development is currently focused on four disease targets: hepatitis C virus, or HCV; hepatitis B virus, or HBV; non-alcoholic steatohepatitis, or NASH; and respiratory syncytial virus, or RSV. Our lead product, paritaprevir, a protease inhibitor designed for use against HCV, is a key compound in AbbVie’s marketed HCV treatment regimens. We also have a second HCV protease inhibitor in phase 3 development with AbbVie, as well as a wholly-owned HCV program using a different class of molecules known as cyclophilin inhibitors, one of which is now in phase 1 development. In addition, we have a program in NASH, with a lead candidate, EDP-305, which we plan to take into clinical trials in the second half of calendar 2016. EDP-305 may have utility in primary biliary cholangitis, or PBC, as well. We also have research programs targeting HBV and RSV.

Our HCV protease inhibitors have been discovered and developed through our collaboration with AbbVie (formerly Abbott Laboratories), including:

In fiscal 2015, we received $125 million in milestone payments for commercialization regulatory approvals of paritaprevir, and we earned $34.1 million in royalties on the portion of AbbVie’s net sales of its HCV regimens allocated to paritaprevir. In the first six months of our fiscal 2016, we received a $30 million milestone payment for the November 2015 reimbursement approval of

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paritaprevir in Japan, and earned $30.9 million in royalties on the portion of AbbVie’s net sales of its HCV regimens allocated to paritaprevir. We earned $13.0 million of those royalties in the three months ended March 31, 2016. We had $245.6 million in cash and marketable securities at March 31, 2016, exclusive of the $13.0 million in royalty receivables due to us from AbbVie at that date. These existing resources will allow us to continue to invest for the foreseeable future in our current research and development programs in virology, namely HCV, HBV and RSV, and in liver disease (non-virology), namely NASH and PBC:

We have utilized our internal chemistry and drug discovery capabilities to generate all of our development-stage programs.

We are currently funding all research and development for our internal programs. We have prioritized our cyclophilin program because we believe that high-barrier-to-resistance mechanisms are going to be increasingly important for the treatment of HCV patients, including those that have failed on current DAA therapies. We expect to incur substantially greater expenses as we continue to advance our cyclophilin inhibitor, EDP-494, through Phase 1 clinical development, which began in January 2016. We are also funding our FXR agonist program, including substantial preclinical development work, which we expect will enable us to initiate clinical development of our lead candidate, EDP-305, in the second half of calendar 2016. In addition, we have increased expenses in fiscal 2016 as we advance other compounds into substantial preclinical development.

Since commencing our operations in 1995, we have devoted substantially all of our resources to the discovery and development of novel compounds for the treatment of infectious diseases and liver diseases. For the periods included in this report we have funded our operations primarily through payments received under our collaborations and a NIAID government contract, as well as net proceeds of approximately $59.9 million that we received from our March 2013 IPO, after deducting underwriting discounts and commissions.

Our revenue from our collaboration agreements has resulted in our reporting net income in each of our past five fiscal years. We expect that our revenue in the near term will continue to be dependent on our collaboration with AbbVie, including royalties from sales of paritaprevir-containing regimens and potential milestone payments and royalties from the development program for ABT-493, our second protease inhibitor being developed with AbbVie. Given the schedule of potential milestone payments and the uncertainties due to the nature and timing of clinical development and regulatory approval and market acceptance of any AbbVie regimen containing ABT-493, as well as uncertainty regarding the extent of royalty payments related to paritaprevir, we cannot be certain as to when or whether we will receive further milestone payments or the extent of our royalty revenues under this collaboration or whether we will continue to report net income in future periods.

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Financial Operations Overview

Revenue

Since our inception, our revenue has been derived from two primary sources: collaboration agreements with pharmaceutical companies and one government research and development contract. We have entered into three significant collaboration agreements and contracts since 2006, the most significant of which is our collaboration agreement with AbbVie. Our second collaboration was with Novartis, from February 2012 through September 2014. In addition, from September 2011 through August 2015, we had a contract with NIAID, which funded the preclinical and early clinical development of an antibiotic product candidate for potential use in biodefense.

Beginning in our fiscal year ended September 30, 2015, we generated royalty revenue from AbbVie’s net sales allocable to paritaprevir, which is part of AbbVie’s treatment regimens for HCV approved in the U.S. in December 2014, in the EU in January 2015 and in dozens of other countries since then. AbbVie received reimbursement approval for paritaprevir in Japan in November 2015.

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The following table is a summary of revenue recognized from our collaboration agreement and our government contract for the three and six months ended March 31, 2016 and 2015:

AbbVie Agreement

Since all of our research obligations under the AbbVie agreement were concluded by June 30, 2011, all milestone payments received since then, have been recognized as revenue upon achievement of each milestone by AbbVie. During the six months ended March 31, 2016 we earned and recognized as revenue a $30.0 million milestone payment upon AbbVie’s achievement of commercialization regulatory approval of a paritaprevir-containing regimen in Japan. During the six months ended March 31, 2015, we earned and recognized as revenue a $75.0 million milestone payment related to AbbVie’s FDA approval of a combination containing paritaprevir. We also earned and recognized as revenue a $50.0 million milestone payment from AbbVie upon commercialization regulatory approval of a similar regimen in Europe during that same period in 2015. Under the terms of the AbbVie agreement, we are eligible to receive additional future milestone payments from AbbVie totaling up to $80.0 million related to the successful commercialization regulatory approvals in major markets of the first HCV treatment regimen incorporating another of our collaboration’s protease inhibitors.

We also receive annually tiered, double-digit royalties per product on AbbVie’s net sales allocable to any one of our collaboration’s protease inhibitors. Under the terms of our agreement, as amended in October 2014, 30% of net sales of 3-DAA regimens containing paritaprevir and 45% of net sales of 2-DAA regimens containing paritaprevir are allocated to paritaprevir for purposes of calculating our annually tiered royalties. Beginning with each January 1 the cumulative net sales of a given royalty-bearing product start at zero for purposes of calculating the tiered royalties.

Operating Expenses

The following table summarizes our operating expenses for the three and six months ended March 31, 2016 and 2015:

Research and Development Expenses

Research and development expenses consist of costs incurred to conduct basic research, such as the discovery and development of novel small molecules as therapeutics. We expense all costs of research and development as incurred. These expenses consist primarily of:

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Project-specific expenses reflect costs directly attributable to our clinical development candidates and preclinical candidates nominated and selected for further development. Remaining research and development expenses are reflected in research and drug discovery, which represents early-stage drug discovery programs. At any given time, we typically have several active early stage research and drug discovery projects. Our internal resources, employees and infrastructure are not directly tied to any individual research or drug discovery project and are typically deployed across multiple projects. As such, we do not maintain information regarding costs incurred for our early-stage research and drug discovery programs on a project-specific basis.

We expect that our research and development expenses will continue to increase in the future as we advance our cyclophilin inhibitor program for HCV and our research and development efforts in NASH, HBV and RSV.

Our research and drug discovery programs are at early stages; therefore, the successful development of our product candidates is highly uncertain and may not result in approved products. Completion dates and completion costs can vary significantly for each product candidate and are difficult to predict. Given the uncertainty associated with clinical trial enrollments and the risks inherent in the development process, we are unable to determine the duration and completion costs of the current or future clinical trials of our product candidates or if, or to what extent, we will generate revenue from the commercialization and sale of any of our product candidates. We anticipate that we will make determinations as to which development programs to pursue and how much funding to direct to each program on an ongoing basis in response to the preclinical and clinical success of each product candidate, as well as ongoing assessments of the commercial potential of each product candidate.

General and Administrative Expenses

General and administrative expenses consist primarily of personnel costs, which include salaries, related benefits and stock-based compensation, of our executive, finance, business and corporate development and other administrative functions. General and administrative expenses also include travel expenses, allocated facility-related costs not otherwise included in research and development expenses, director’s and officer’s liability insurance premiums, and professional fees for auditing, tax and legal services and patent expenses.

Other Income (Expense)

Interest income. Interest income consists of interest earned on our cash equivalents and short-term and long-term marketable securities balances

Interest expense. Interest expense consists of interest expense related to our capital lease obligation and to the value of accrued third-party license fees.

Change in fair value of warrant liability and Series 1 nonconvertible preferred stock. We have issued warrants for the purchase of our Series 1 nonconvertible preferred stock and we have issued Series 1 nonconvertible preferred stock, both of which we believe are financial instruments that may require a transfer of assets because of the liquidation preference features of the underlying stock. Therefore, we have classified these warrants and Series 1 nonconvertible preferred stock as liabilities that we remeasure to fair value at each reporting period and we record the changes in the fair value of the warrants and Series 1 nonconvertible preferred stock as a component of other income (expense).

Income Tax Expense

Income tax expense is based on our best estimate of applicable income tax rates for the entire fiscal year applied to pre-tax profit reported for the year to date period.

Critical Accounting Policies

Our consolidated financial statements are prepared in accordance with accounting principles generally accepted in the United States of America. The preparation of our consolidated financial statements and related disclosures requires us to make estimates and assumptions that affect the reported amount of assets, liabilities, revenue, costs and expenses, and related disclosures. We believe that the estimates and assumptions involved in the accounting policies described below may have the greatest potential impact on our consolidated financial statements and, therefore, consider these to be our critical accounting policies. We evaluate our estimates and assumptions on an ongoing basis. Our actual results may differ from these estimates under different assumptions and conditions. See also our Annual Report on Form 10-K for the fiscal year ended September 30, 2015 (referred to as our 2015 Form 10-K) for information about these accounting policies as well as a description of our other significant accounting policies. We believe that of our significant accounting policies, the following accounting policies involve the most judgment and complexity:

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Accordingly, we believe the policies set forth above are critical to fully understanding and evaluating our financial condition and results of operations. If actual results or events differ materially from the estimates, judgments and assumptions used by us in applying these policies, our reported financial condition and results of operations could be materially affected.

There have been no material changes in our critical accounting policies since September 30, 2015. For further information, please see the discussion of critical accounting policies included in our 2015 Form 10-K.

Results of Operations

Comparison of Three Months Ended March 31, 2016 and 2015

Revenue.

We recognized revenue of $13.0 million during the three months ended March 31, 2016, as compared to $57.4 million during the three months ended March 31, 2015. During the three months ended March 31, 2016, revenue consisted of royalties on the portion of AbbVie’s net sales of its HCV treatment regimens allocable to paritaprevir. During the three months ended March 31, 2015, revenue consisted of a $50.0 million milestone payment from AbbVie upon commercialization regulatory approval of paritaprevir-containing regimens in Europe, $7.0 million in royalties on the portion of AbbVie’s net sales of its HCV treatment regimen allocable to paritaprevir, and $0.4 million under our contract with NIAID, which ended in fiscal 2015.

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Research and development expenses.

Research and development expenses increased $3.8 million from the three months ended March 31, 2015, as compared to the same period in 2016. The increase was primarily due to an increase in headcount to support our preclinical activities, expansion of our research facility and an increase in clinical and preclinical activities in our virology and liver disease programs.

General and administrative expenses. General and administrative expenses increased by $1.0 million from the three months ended March 31, 2015, as compared to the same period in 2016. The increase was primarily due to an increase in stock-based compensation expense related to an increase in headcount, additional stock option grants to employees, and achievement of performance-based option milestones granted to management.

Other income (expense). Changes in components of other income (expense), net, were as follows:

Interest income. The increase in interest income for the three months ended March 31, 2016, as compared to the same period in 2015, was due to higher average investment balances in the second fiscal quarter of 2016 as compared to 2015.

Change in fair value of warrant liability and Series 1 nonconvertible preferred stock. During the three months ended March 31, 2016, we recorded income due to a decrease in the fair value of our warrant liability and Series 1 nonconvertible preferred stock as a result of the remeasurement of our warrant liability and Series 1 nonconvertible preferred stock. During the same period in 2015, we recorded an expense due to an increase in the fair value of our warrant liability and Series 1 nonconvertible preferred stock as a result of the remeasurement of our warrant liability and Series 1 nonconvertible preferred stock.

Income tax expense. For the three months ended March 31, 2016 and March 31, 2015, we recorded an income tax provision of $1.6 million and $20.0 million, respectively. For the three months ended March 31, 2016 we increased our estimate of our annual effective tax rate for fiscal 2016, which resulted in an income tax provision of $1.6 million, despite our pre-tax loss for the quarter. For the three months ended March 31, 2015 we recorded an income tax provision of $20.0 million, which represented an effective tax rate of 41.0%.

Comparison of Six Months Ended March 31, 2016 and 2015

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Revenue.

We recognized revenue of $61.4 million during the six months ended March 31, 2016, as compared to $134.9 million during the six months ended March 31, 2015. During the six months ended March 31, 2016 and 2015, we recognized $30.0 million and $125.0 million, respectively, in milestone payments under our collaboration with AbbVie as a result of regulatory approvals for AbbVie’s paritaprevir-containing regimens in Japan and the U.S. and EU, respectively. We earned royalties of $30.9 million and $8.4 million during the six months ended March 31, 2016 and 2015, respectively, related to net sales of AbbVie’s paritaprevir-containing regimens. Government contract revenue was $0.6 million and $1.5 million during the six months ended March 31, 2016 and 2015, respectively, under our contract with NIAID which ended in fiscal 2015. We recognized revenue under our NIAID contract in the first quarter of fiscal 2016 based on final billings after the contract was completed at the end of fiscal 2015.

Research and development expenses.

Research and development expenses increased $8.3 million from the six months ended March 31, 2015, as compared to the same period in 2016. The increase was primarily due to an increase in headcount to support our preclinical activities, expansion of our research facility and an increase in clinical and preclinical activities in our virology and liver disease programs.

General and administrative expenses. General and administrative expenses increased by $2.0 million from the six months ended March 31, 2015, as compared to the same period in 2016. The increase was primarily due to an increase in stock-based compensation expense as a result of an increase in headcount, additional stock option grants to employees, and achievement of performance-based option milestones granted to management.

Other income (expense). Changes in components of other income (expense), net, were as follows:

Interest income. The increase in interest income for the six months ended March 31, 2016, as compared to the six months ended March 31, 2015, was due to higher average investment balances in the first six months of 2016 as compared to the same period in 2015.

Change in fair value of warrant liability and Series 1 nonconvertible preferred stock. During the six months ended March 31, 2016 and 2015, we recorded income due to a decrease in the fair value of our warrant liability and Series 1 nonconvertible preferred stock as a result of the remeasurement of our warrant liability and Series 1 nonconvertible preferred stock.

Income tax expense. For the six months ended March 31, 2016 and March 31, 2015, we recorded an income tax provision of $11.3 million and $48.5 million, respectively, representing an estimated annual effective tax rate of 31.5% and 40.7%, respectively. For the six months ended March 31, 2016 our estimated annual effective tax rate was lower than in the comparable period of 2015 primarily due to Congress’ reinstatement of federal research and development tax credits during the most recent fiscal year which is included in the 2016 annual effective tax rate.

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Liquidity and Capital Resources

At March 31, 2016, our principal sources of liquidity were cash, cash equivalents and short-term and long-term marketable securities totaling $245.6 million.

From our inception through March 31, 2016, we have financed our operations, primarily through contract payments under our collaborations, government research and development contracts and grants, private placements, and our initial public offering of our equity. The following table shows a summary of our cash flows for the six months ended March 31, 2016 and 2015.

Net cash provided by operating activities

The decrease in cash provided by operating activities of $53.2 million from the six months ended March 31, 2015 to the same period in 2016 is primarily driven by a decrease in cash receipts of $64.2 million under our collaboration with AbbVie. We received $62.2 million in cash from AbbVie during the first six months of fiscal 2016 compared to $126.4 million during the first six months of 2015. Receipts from AbbVie in the first six months of 2015 were primarily triggered by achievement of milestones upon commercialization regulatory approval in the U.S. and EU for AbbVie’s first HCV treatment regimen containing paritaprevir. In the first six months of 2016, we generated cash receipts from a $30.0 million payment upon commercialization regulatory approval of paritaprevir in Japan and royalties of $32.2 million based on AbbVie’s net sales of its HCV regimens. In addition, we increased cash spending on research and development by $7.6 million during the first six months of 2016 compared to the same period in 2015 in order to progress clinical and preclinical studies in our proprietary programs. This decrease in our cash balance was partially offset by a decrease of $16.4 million in income tax payments in 2016 as compared to 2015.

Net cash used in investing activities

The decrease in cash used in investing activities of $94.4 million from the six months ended March 31, 2015 to the same period in 2016 was driven by timing of purchases and maturities of marketable securities. During the six months ended March 31, 2016, we utilized $84.6 million of cash to purchase marketable securities, offset by $82.2 million of cash received from the maturity of marketable securities, compared to $135.8 million of cash used to purchase marketable securities, offset by maturities of marketable securities of $33.7 million and sales of marketable securities of $2.2 million in the same comparable period in 2015. During the six months ended March 31, 2016 we also utilized cash of $3.7 million as part of the expansion of our research facility compared to $0.4 million of cash used to purchase fixed assets in the same comparable period in 2015.

Net cash provided by financing activities

The decrease in net cash provided by financing activities of $1.6 million from the six months ended March 31, 2015 to the same period in 2016 was driven by a lower income tax benefit from the exercise of stock options of $1.9 million, partially offset by an increase in proceeds from exercises of stock options of $0.3 million.

Funding requirements

As of March 31, 2016, we had $245.6 million in cash, cash equivalents and short-term and long-term marketable securities. We believe that our existing cash, cash equivalents and marketable securities as of March 31, 2016, will be sufficient to meet our anticipated cash requirements for the foreseeable future. However, our forecast of the period of time through which our financial resources will be adequate to support our operations is a forward-looking statement that involves risks and uncertainties, and actual results could vary materially.

Our future capital requirements are difficult to forecast and will depend on many factors, including:

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Off-Balance Sheet Arrangements

We do not engage in any off-balance sheet financing activities. We do not have any interest in entities referred to as variable interest entities, which include special purpose entities and other structured finance entities.

Contractual Obligations and Commitments

In our Annual Report on Form 10-K for the year ended September 30, 2015, Part II, Item 7, Management’s Discussion and Analysis of Financial Conditions and Results of Operations, under the heading “Contractual Obligations and Commitments”, we have described our commitments and contingencies. There were no material changes in our commitments and contingencies during the six months ended March 31, 2016.

Recently Issued Accounting Pronouncements

A description of recently issued accounting pronouncements that may potentially impact our financial position and results of operations is set forth in Note 2 to the consolidated financial statements included in this Quarterly Report on Form 10-Q.

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Interest Rate Sensitivity

We had cash, cash equivalents and short-term and long-term marketable securities of $245.6 million at March 31, 2016 consisting of cash, money market funds, commercial paper, corporate bonds and government securities. Interest income is sensitive to changes in the general level of interest rates; however, due to the nature of these investments, we do not believe that we have any material exposure to changes in the fair value of our investment portfolio as a result of changes in interest rates. We had no debt outstanding as of March 31, 2016.

a) Conclusion Regarding the Effectiveness of Disclosure Controls and Procedures.

Our management, with the participation of the principal executive officer and principal financial officer, has evaluated the effectiveness of the design and operation of our disclosure controls and procedures (as defined in Rules 13a-15(e) and 15d-15(e) under the Securities Exchange Act of 1934, as amended (the “Exchange Act”)) as of the end of the period covered by this quarterly report. Based on this evaluation, the principal executive officer and principal financial officer concluded that these disclosure controls and procedures are effective and designed to ensure that the information required to be disclosed in our reports filed or submitted under the Exchange Act is recorded, processed, summarized and reported within the requisite time periods.

b) Changes in Internal Control Over Financial Reporting.

There was no change in our internal control over financial reporting (as defined in Rules 13a-15(f) and 15d-15(f) under the Exchange Act) identified in connection with the evaluation of our internal control performed during the last fiscal quarter that has materially affected, or is reasonably likely to materially affect, our internal control over financial reporting.

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PART II – OTHER INFORMATION

RISK FACTORS

Our business faces significant risks and uncertainties. Certain factors may have a material adverse effect on our business prospects, financial condition and results of operations, and you should carefully consider them. Accordingly, in evaluating our business, we encourage you to consider the following discussion of risk factors, in its entirety, in addition to other information contained in or incorporated by reference into this Annual Report on Form 10-K and our other public filings with the SEC. Other events that we do not currently anticipate or that we currently deem immaterial may also affect our business, prospects, financial condition and results of operations.

Risks Related to Our Business

Our financial prospects for the next several years are dependent upon the development and commercialization efforts of AbbVie for combination therapies incorporating the protease inhibitors paritaprevir or ABT-493 for the treatment of HCV. AbbVie may act in its best interest rather than in our best interest, which could adversely affect our business.

We rely on AbbVie to fund and conduct the clinical development and commercialization of regimens containing paritaprevir or ABT-493 (our second protease inhibitor, in clinical development), over which AbbVie has complete control. Our ability to generate significant revenue in the near term will depend primarily on the successful development, regulatory approval, marketing and commercialization by AbbVie of combination therapies incorporating paritaprevir or ABT-493. Such success is subject to significant uncertainty, and we have no control over the resources, time and effort that AbbVie may devote to paritaprevir or ABT-493. Any of several events or factors could have a material adverse effect on our ability to generate revenue from AbbVie’s commercialization of paritaprevir or potentially ABT-493 in combination therapies. For example, AbbVie:

We do not have access to all information regarding the products being developed and potentially commercialized by AbbVie, including information about clinical trial design and execution, safety reports from clinical trials, spontaneous safety reports for any marketed product, regulatory affairs, process development, manufacturing, marketing, sales and other areas known by AbbVie. Thus, our ability to keep our stockholders informed about the status of products and product candidates under our collaboration is limited by the degree to which AbbVie keeps us informed. If AbbVie does not perform in the manner we expect or fulfill its responsibilities in a timely manner, or at all, the further development and global commercialization of paritaprevir and the clinical development, regulatory approval and commercialization efforts related to ABT-493 could be delayed or terminated or be commercially unsuccessful. In addition, AbbVie has the right to make decisions regarding the development and commercialization of product candidates without consulting us, and may make decisions with which we do not agree. Conflicts between us and AbbVie may arise if there is a dispute

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about the progress of the clinical development of a product candidate, the achievement and payment of a milestone amount, the relative values allocated to the pharmaceutically active ingredients, or the ownership of intellectual property developed during the course of our collaboration agreement. If AbbVie acts in a manner that is not in our best interest, then it could adversely affect our business and prospects.

We and AbbVie face substantial competition in the markets for HCV drugs, and there are many companies developing potential therapies for non-alcoholic steatohepatitis (“NASH”), hepatitis B virus (“HBV”) and respiratory syncytial virus (“RSV”), as well as other liver and viral diseases, which may result in others discovering, developing or commercializing products before we do or doing so more successfully than we or our collaborators.

The pharmaceutical and biotechnology industries are intensely competitive and rapidly changing. Many large pharmaceutical and biotechnology companies, academic institutions, governmental agencies and other public and private research organizations are commercializing or pursuing the development of products that target HCV, NASH, HBV, RSV and other infectious diseases or liver diseases that we may target in the future.

Many of our competitors have substantially greater commercial infrastructure and greater financial, technical and personnel resources than we have, as well as drug candidates in late-stage clinical development.

Our competitors may succeed in developing competing products and obtaining regulatory approval before we or any collaborator of ours does with our product candidates, or they may gain acceptance for the same markets that we are targeting. If we are not “first to market” with one of our product candidates in one or more disease indications, our competitive position could be compromised because it may be more difficult for us to obtain marketing approval for that product candidate and market acceptance of that product candidate as a second competitor. In addition, any new product that competes with an approved product typically must demonstrate compelling advantages in efficacy, convenience, tolerability or safety, or some combination of these factors, in order to overcome price competition and be commercially successful.

We expect our current and future product candidates to face intense and increasing competition as new products continue to enter the HCV and antiviral markets and advanced technologies become available, particularly in the case of HCV in combinations with existing products and other new products. First generation protease inhibitors, Incivek^® (telaprevir) of Vertex and Victrelis™ (boceprevir) of Merck, were approved in 2011 by the FDA for the treatment of HCV, which in combination with interferon and ribavirin, were the previous standard of care. However, by January 2015 both Vertex and Merck had announced they would discontinue the sale of these products, noting competing treatments and diminishing market demand. The evolving competitive landscape in HCV intensified in December 2013, when the FDA approved sofosbuvir (Sovaldi^®), a nucleotide analogue inhibitor of the HCV NS5B polymerase enzyme from Gilead, for patients with genotype 2 or 3 HCV and no requirement for interferon (also approved for patients with genotypes 1 or 4 when combined with pegylated interferon and ribavirin). On July 9, 2014, Bristol-Myers Squibb gained approval in Japan for the NS5A/protease inhibitor combination daclatasvir/asunaprevir. In October 2014 the FDA approved Gilead’s interferon-free Harvoni^®, a fixed-dose combination of sofosbuvir and ledipasvir (a NS5A inhibitor) for patients with genotype 1 HCV. Also in November 2014 the FDA approved an interferon-free combination therapy of simeprevir (brand name Olysio^®, from Janssen Therapeutics) and sofosbuvir for genotype 1 HCV patients. In December 2014, AbbVie’s VIEKIRA PAK treatment regimen containing our collaboration’s paritaprevir was approved by the FDA, and since then approvals of other paritaprevir-containing regimens and Harvoni followed in the EU and Japan. In July 2015, BMS received approval in the US for daclatasvir in combination with sofosbuvir for genotype 3 HCV patients. Also in that month, the FDA approved the paritaprevir-containing regimen Technivie^TM from our partner AbbVie for genotype 4 HCV patients. On January 28, 2016 Merck received FDA approval for its combination of a protease and an NS5A inhibitor for the treatment of patients with genotypes 1 or 4 HCV infection. Other all-oral treatment regimens are under development at Merck, Gilead and Johnson & Johnson and may obtain regulatory approvals for the treatment of HCV in the next year. These other potential new treatment regimens may render AbbVie’s treatment regimens containing any of our HCV product candidates noncompetitive. In particular, regimens containing our HCV product candidates may not be able to compete successfully with other products and regimens, a number of which remain under active development and involve multiple classes of inhibitors of HCV, including protease inhibitors, polymerase inhibitors (nucleoside and non-nucleoside), NS5A inhibitors, and others, under development by companies such as Achillion, Bristol-Myers Squibb, Co-Crystal Pharma, Gilead, Johnson & Johnson, Medivir, Merck, Regulus and Roche, as well as by our collaborator AbbVie.

Competitive products in the form of other treatment methods or a vaccine for HCV may render our product candidates licensed to others, as well as any future product candidates we may develop ourselves, obsolete or noncompetitive. Even if successfully developed and subsequently approved by the FDA, our product candidates will face competition based on their safety and effectiveness, the timing and scope of the regulatory approvals, reimbursement coverage, price, patent position, the availability and cost of supply, marketing and sales capabilities, and other factors. If the product candidates developed under our collaboration agreement with AbbVie face competition from generic products, the collaboration agreement provides that the royalty rate applicable to such product candidates is reduced significantly by a specified percentage on a product-by-product, country-by-country basis. If we and our collaborator are not able to compete effectively against our current and future competitors, our business will not grow and our financial condition, operations and stock price will suffer.

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Though there is currently no approved treatment for NASH, we expect significant competition from other companies in the development of new treatments for NASH and related conditions. We are aware of several companies with programs that are significantly more advanced than ours, including companies with compounds in Phase 3 in NASH, namely Intercept and Genfit. In addition, a number of companies are in Phase 2 clinical trials for NASH or related conditions. These companies include Alberio, Arisaph, Astra-Zeneca, BMS, Cempra, Conatus, Galectin, Galmed, Gilead, GlaxoSmithKline, Immuron, Medicinova, Novo Nordisk, and Tobira. A significant number of other companies are conducting earlier clinical trials that may be applicable in NASH and other cholestatic diseases, including Boehringer Ingelheim, Cymabay, Durect, Islet, Metabolic Solutions Development Company, NGM, Shire, and Viking, and there are additional companies conducting preclinical studies in these disease areas.

Similarly, HBV and RSV represent competitive therapeutic areas. While there are effective antiviral medications prescribed for HBV, they generally have low true cure rates. Many companies are seeking to develop new HBV drugs that alone or in combination with other mechanisms could lead to a functional cure of HBV. Gilead, Roche, Arbutus, and Arrowhead Pharmaceuticals have Phase 2 programs in progress, and a number of companies have Phase 1 or earlier stage HBV programs, including Alnylam, Arbutus, Assembly, Johnson & Johnson, Ionis, Spring Bank and Replicor.

For RSV, there are no safe and effective approved therapies. Several companies are seeking new antiviral treatments for RSV in adult and pediatric settings. Aviragen (formerly Biota), Johnson & Johnson and Gilead each have compounds in Phase 2 development, as does Ablynx with a potential therapeutic antibody. Earlier stage programs have also been reported by Ark Biosciences, and Medivir.

If we are not able to develop new products that can compete effectively against our current and future competitors, our business will not grow and our financial condition, operations and stock price will suffer.

We have not developed independently any approved products and we have limited clinical development experience, which makes it difficult to assess our ability to develop and commercialize our future product candidates.

AbbVie has been and will continue to be responsible for all of the clinical development of our paritaprevir and ABT-493 protease inhibitor product candidates. We have not yet demonstrated an ability to address successfully many of the risks and uncertainties associated with late stage clinical development, regulatory approval and commercialization of therapeutic products such as the ones we plan to develop independently. For example, to execute our business plan for development of our independent programs for HCV using our cyclophilin inhibitor in one or more combination regimens as well as for any of our research programs beyond HCV, we will need to successfully:

If we are unsuccessful in accomplishing these objectives, we may not be able to successfully develop and commercialize our future product candidates and expand our business or continue our operations.

If we are not successful in discovering further product candidates in addition to paritaprevir, ABT-493 and EDP-494 our ability to expand our business and achieve our strategic objectives will be impaired.

Most of our internal research programs are at preclinical stages. Research programs designed to identify product candidates require substantial technical, financial and human resources, whether or not any product candidates are ultimately identified. Our research

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programs may initially show promise in identifying additional potential product candidates, yet fail to yield product candidates for clinical development or commercialization for many reasons, including the following:

Additional drug candidates that we may develop will require significant research, preclinical and clinical studies, regulatory approvals and commitments of resources before they can be commercialized. We cannot give assurance that our research will lead to the discovery of any additional drug candidates that will generate additional revenue for us. If we are unable to identify additional compounds suitable for preclinical and clinical development, we may not be able to obtain sufficient product revenue in future periods, which likely would result in significant harm to our financial position and adversely impact our stock price.

If we fail to attract and keep senior management and key scientific personnel, we may be unable to successfully develop our product candidates, conduct our clinical trials and commercialize our product candidates.

Our success depends in part on our continued ability to attract, retain and motivate highly qualified management, clinical and scientific personnel. We are highly dependent upon our senior management, particularly Jay R. Luly, Ph.D., our Chief Executive Officer and President, and Yat Sun Or, Ph.D., our Senior Vice President, Research and Development and Chief Scientific Officer, as well as other employees and consultants. Although none of these individuals has informed us to date that he or she intends to retire or resign in the near future, the loss of the services of any of these individuals or one or more of our other members of senior management could delay or prevent the successful development of our future product candidates.

Although we have not historically experienced unique difficulties attracting and retaining qualified employees, we could experience such problems in the future. For example, competition for qualified personnel in the biotechnology and pharmaceutical fields is intense. In addition, we will need to hire additional personnel as we expand our clinical development and commercial activities. We may not be able to attract and retain quality personnel on acceptable terms.

We may encounter difficulties in managing our growth and expanding our operations successfully.

As we expand our research efforts and seek to advance our product candidates through clinical trials, we will need to expand our development, regulatory, manufacturing, marketing and sales capabilities or contract with third parties to provide these capabilities for us. As our operations expand, we expect that we will need to manage additional relationships with various strategic partners, suppliers and other third parties. Future growth will impose significant added responsibilities on members of management. Our future financial performance and our ability to commercialize our product candidates and to compete effectively will depend, in part, on our ability to manage any future growth effectively. To that end, we must be able to manage our development efforts and clinical trials effectively and hire, train and integrate additional management, administrative and sales and marketing personnel. We may not be able to accomplish these tasks, and our failure to accomplish any of them could prevent us from successfully growing our company.

Expenses associated with development of our product candidates may cause our earnings to fluctuate from period to period.

Many of the preclinical and clinical development activities required for our product candidates will have to be contracted out to CROs at significant expense. It is difficult to accurately predict the timing of these expenses, and we expect that they will vary from quarter to quarter. In addition, the FDA or other regulatory agencies may require more preclinical or clinical testing than we originally anticipated for any of our drug candidates. We may also be required to purchase expensive competitor drugs for use in our trials, either to demonstrate potential treatment combinations or as comparators to our product candidates. As a result, the expenses of our development programs and our operating results may fluctuate significantly from quarter to quarter, and our stock price may be adversely affected.

To date, our principal sources of revenue have been our collaboration agreements, including our current agreement with AbbVie and our prior agreement with Novartis. Future milestone payments and the level of royalties under the AbbVie agreement are uncertain. We have had no products approved for commercial sale by us. Therefore, it is possible that we may incur operating losses in one or more years in the future, and our ability to achieve sustained profitability is unproven.

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In each of our 2013, 2014 and 2015 fiscal years as well as in the first quarter of fiscal 2016, our net income resulted primarily from license payments, including milestone payments we earned from AbbVie and/or Novartis and royalties we earned since December 2014 on AbbVie’s net sales allocated to paritaprevir. There is no assurance, however, that we will report net income in subsequent years. To date, we have not commercialized any products ourselves.

Our principal source of revenue historically has been our collaboration agreements, including our current agreement with AbbVie. The level of future royalties on paritaprevir are uncertain given the competitive nature of the market for HCV therapies, the emergence of new, and in some cases, not yet approved, therapies for HCV, the changing nature of payer contracts of AbbVie and others, and the varying rates of reimbursement in different countries. In addition, it is not yet clear what will be the long-term impact, if any, of the October 2015 drug safety communication from the FDA regarding the risks of AbbVie’s VIEKIRA PAK and TECHNIVIE regimens in patients with decompensated cirrhosis, for which those regimens had never been recommended. Future milestone payments are uncertain because AbbVie may choose not to continue research or development activities for our ABT-493 product candidate. For example, under our previous collaboration with Novartis for the development of our NS5A inhibitor, Novartis decided in September 2014 not to pursue further development of the licensed product candidate in light of its decision that HCV was no longer a strategic focus of Novartis, which resulted in the NS5A inhibitor program being transferred back to us and our collaboration being terminated. In addition, under our AbbVie collaboration we may not achieve the specified milestones for ABT-493, that product candidate may not be approved by the FDA or other regulatory authorities or, if ABT-493 is approved, the combination containing it may not be accepted in the market. If we are unable to develop and commercialize any more of our product candidates, either alone or with a collaborator, or if any such product candidate does not achieve market acceptance, we may never generate sufficient product royalties or product sales. In addition, for any of our product candidates other than paritaprevir or ABT-493 included in a treatment regimen with more than one active compound, it would be uncertain what portion of net sales of the regimen would be allocated to our product candidate. The existence of multiple active compounds in the regimen or an unfavorable allocation to our product candidate could adversely affect our royalty revenue. Even if we do generate significant product royalties or product sales, we may not be able to sustain profitability on a quarterly or annual basis. Our failure to sustain profitability could depress the market price of our common stock and ultimately could impair our ability to raise capital, expand our business, diversify our product offerings or continue our operations. A decline in the market price of our common stock also could cause you to lose all or a part of your investment.

We may require substantial additional financing in the longer term to achieve our goals if the further commercialization of paritaprevir is delayed or curtailed or if the development of ABT-493 is delayed or terminated. A failure to obtain this necessary capital when needed could force us to delay, limit, reduce or terminate some or all of our product development efforts.

Since our inception, most of our resources have been dedicated to the discovery and preclinical development of our product candidates. In particular, we have expended, and believe that we will continue to expend for the foreseeable future, substantial resources discovering and developing our proprietary product candidates. These expenditures will include costs associated with research and development, preclinical manufacturing of product candidates, conducting preclinical experiments and clinical trials and obtaining regulatory approvals, as well as commercializing any products later approved for sale. For the foreseeable future, we expect to incur substantial additional costs associated with research and development for our internally developed programs, exclusive of costs incurred by our collaborator in developing our licensed product candidate ABT-493. In addition, we may seek opportunities to in-license or otherwise acquire new therapeutic candidates and therapies.

Our future capital requirements depend on many factors, including:

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Additional funds may not be available if and when we need them, on terms that are acceptable to us, or at all. Our ability to raise funds will depend on financial, economic and market conditions and other factors, many of which are beyond our control. If adequate funds are not available to us on a timely basis, we may be required to delay, limit, reduce or terminate preclinical studies, clinical trials or other research and development activities for one or more of our product candidates.

Our government funded contract for our antibiotic program, which was concluded in fiscal 2015, is subject to audit and adjustments that could affect our previously reported revenues.

Our contract with the National Institute of Allergy and Infectious Diseases, or NIAID, a division of the National Institutes of Health, an agency of the United States Department of Health and Human Services, to support our antibiotic program, was completed in fiscal 2015. Our contract related costs and fees, including allocated indirect costs, are subject to audits and adjustments by negotiation between us and the U.S. government. As part of the audit process, the government audit agency verifies that all charges made by a contractor against a contract are legitimate and appropriate. Audits may result in recalculation of contract revenues and non-reimbursement of some contract costs and fees. Any audits of our contract related costs and fees could result in material adjustments to our reported revenue and require payments by us to the U.S. government.

Risks Related to Development, Clinical Testing and Regulatory Approval of Our Product Candidates

Clinical drug development involves a lengthy and expensive process with uncertain timelines and uncertain outcomes. If clinical trials are prolonged or delayed, we, AbbVie or any other future collaborator may be unable to commercialize our product candidates on a timely basis.

Clinical testing is expensive and, depending on the stage of development, can take a substantial time period to complete. Its outcome is inherently uncertain, and failure can occur at any time during clinical development. None of our product candidates in our pipeline other than paritaprevir has yet advanced beyond Phase 2 clinical trials. Any future clinical trials of our other product candidates may fail to demonstrate sufficient safety and efficacy. Moreover, regulatory and administrative delays for any product candidate in our pipeline may adversely affect our or any collaborator’s clinical development plans and jeopardize our or any collaborator’s ability to attain product approval, commence product sales and compete successfully against other therapies.

Clinical trials can be delayed for a variety of reasons, including delays related to:

The results of any Phase 3 clinical trial may not be adequate to support marketing approval for one of AbbVie’s regimens containing a protease inhibitor. These clinical trials are lengthy and usually involve from many hundreds to thousands of patients. In addition, if the FDA or the EMA disagrees with AbbVie’s choice of the key testing criteria, or primary endpoint, or the results for the primary

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endpoint are not robust or significant relative to the control group of patients not receiving the experimental therapy or are subject to confounding factors, or are not adequately supported by other study endpoints, the FDA or the EMA, or both, may refuse to approve AbbVie’s product candidate. The FDA or the EMA also may require additional clinical trials as a condition for approving any of these product candidates. AbbVie estimates that it will be 2017 before an NDA for one of AbbVie’s HCV treatment regimens containing ABT-493 could be approved by the FDA or the EMA.

We could also encounter delays if a clinical trial is suspended or terminated by us, by the IRBs of the institutions in which such trial is being conducted, by any Data Safety Monitoring Board, or DSMB, for such trial, or by the FDA, the EMA or other regulatory authorities. Such authorities may impose such a suspension or termination due to a number of factors, including failure to conduct the clinical trial in accordance with regulatory requirements or our clinical protocols, inspection of the clinical trial operations or trial site by the FDA or other regulatory authorities resulting in the imposition of a clinical hold, unforeseen safety issues or adverse side effects, failure to demonstrate a benefit from using a drug, changes in governmental regulations or administrative actions or lack of adequate funding to continue the clinical trial. In addition, delays can occur due to safety concerns arising from trials or other clinical data regarding another company’s product candidate in the same compound class as one of ours. If we or our collaborators experience delays in the completion of, or termination of, any clinical trial of one of our product candidates, the commercial prospects of the product candidate will be harmed, and our or our collaborators’ ability to commence product sales and generate product revenues from the product candidate will be delayed. In addition, any delays in completing our clinical trials will increase our costs and slow down our product candidate development and approval process. Any of these occurrences may harm our business, financial condition and prospects significantly. In addition, many of the factors that cause, or lead to, a delay in the commencement or completion of clinical trials may also ultimately lead to the denial of regulatory approval of our product candidates.

EDP-494 or any product candidate in our current NASH program may have undesirable side effects which may delay or prevent marketing approval, or, if approval is received, require our product candidate to be taken off the market, require us to include safety warnings or otherwise limit sales.

We have designed our EDP-494 program to be substantially different from another cyclophilin inhibitor, alisporivir. The combination of interferon with ribavirin and alisporivir has been associated with pancreatitis in patients receiving treatment with the combination during clinical trials. We do not plan to develop EDP-494 in combination with interferon or ribavirin, which have also been associated with pancreatitis in other clinical contexts not including a cyclophilin inhibitor. However, we cannot give any assurance that EDP-494 will not result in any unforeseen side effects.

In our NASH program, we are developing agonists of the farnesoid X receptor, or FXR, that are designed to bind to that receptor and then trigger a response from it. With the exception of one drug approved to treat cholesterol gallstone dissolution and a rare lipid storage disease, there are no approved FXR agonists and the adverse effects from long-term exposure to this drug class are unknown. Unforeseen side effects from any of our product candidates could arise either during clinical development or, if approved, after the approved product has been marketed. The range and potential severity of possible side effects from systemic therapies like FXR agonists could be significant.

In addition, our drug candidates for NASH may be developed as a potential treatment for a severe disease that commonly occurs in patients with other serious conditions, including metabolic syndrome and diabetes. Any clinical trials in NASH will necessarily be conducted in patient populations that may be more prone than the general population to exhibit certain disease states or adverse events. It may be difficult to discern whether certain events or symptoms observed during our trials were due to our drug candidates or placebo, resulting in our company and our development programs being negatively affected even if such events or symptoms are ultimately determined to be unlikely related to our drug candidates.

If any of our product candidates receives marketing approval and we or others later identify undesirable or unacceptable side effects caused by such products:

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Any of these events could prevent us or any potential future collaborator from achieving or maintaining market acceptance of the affected product or could substantially increase commercialization costs and expenses, which in turn could delay or prevent us from generating significant revenue from the sale of any product we develop with EDP-494 or NASH.

If we, or AbbVie in the case of our protease inhibitor product candidates, are required to suspend or discontinue clinical trials due to side effects or other safety risks associated with our product candidates, or if we or AbbVie are required to conduct studies on the long-term effects associated with the use of any of those product candidates, efforts to commercialize any of those product candidates could be delayed or halted.

Clinical trials involving our product candidates may be suspended or terminated at any time for a number of safety-related reasons. For example, we or AbbVie may voluntarily suspend or terminate clinical trials if at any time one of our product candidates, or a combination therapy including any of them, presents an unacceptable safety risk to the clinical trial patients. In addition, IRBs or regulatory agencies may order the temporary discontinuation or termination of clinical trials at any time if they believe that the clinical trials are not being conducted in accordance with applicable regulatory requirements, including if they present an unacceptable safety risk to patients. Administering any product candidate to humans may produce undesirable side effects. The existence of undesirable side effects resulting from any of our product candidates, or a combination therapy including any of them, could cause us, AbbVie or regulatory authorities, such as the FDA or EMA, to interrupt, delay or halt clinical trials of our product candidates and could result in the FDA or EMA or other regulatory agencies denying further development or approval of our product candidates for any or all targeted indications. This, in turn, could prevent us or AbbVie from commercializing our product candidates.

Results of earlier clinical trials may not be predictive of the results of later-stage clinical trials.

The results of preclinical studies and early clinical trials of our product candidates, whether ABT-493, EDP-494, EDP-239, EDP-305 or any of our future product candidates, may not be predictive of the results of later-stage clinical trials, if any. In addition, results of Phase 3 clinical trials in one or more ethnic groups are not necessarily indicative of results in other ethnic groups. Product candidates in later stages of clinical trials may fail to show the desired safety and efficacy results despite having progressed through preclinical studies and initial clinical trials. Many companies in the biopharmaceutical industry have suffered significant setbacks in advanced clinical trials due to adverse safety profiles or lack of efficacy, notwithstanding promising results in earlier studies. Similarly, future clinical trial results may not be successful for these or other reasons.

Product candidate development risk is heightened by any changes in the planned clinical trials compared to the completed clinical trials. As product candidates are developed through preclinical early and late stage clinical trials towards approval and commercialization, it is customary that various aspects of the development program, such as manufacturing and formulation, are altered along the way in an effort to optimize processes and results. Such changes carry the risk that they will not achieve these intended objectives. Any of these changes could make the results of planned clinical trials or other future clinical trials we or our collaborators may initiate less predictable and could cause our product candidates to perform differently, which could delay completion of clinical trials, delay approval of our product candidates and/or jeopardize our or our collaborators’ ability to commence product sales and generate revenues.

The regulatory approval processes of the FDA, the EMA and other comparable foreign authorities are lengthy, time-consuming and inherently unpredictable, and if we or our collaborators are ultimately unable to obtain timely regulatory approval for our product candidates, our business will be substantially harmed.

The regulatory approval process is expensive and, while the time required to gain FDA and foreign regulatory approval is uncertain, it may take years. Regulatory approvals are unpredictable and depend upon numerous factors, including the substantial discretion of the regulatory authorities. In addition, approval policies, regulations, or the type and amount of preclinical and clinical data necessary to gain approval may change during the course of a product candidate’s clinical development and may vary among jurisdictions. We or our collaborators may be required to undertake and complete certain additional preclinical studies to generate toxicity and other data required to support the submission of a New Drug Application, or NDA, to the FDA or comparable application to other regulatory authorities. AbbVie obtained all regulatory approvals for paritaprevir, our sole approved product. We have not obtained regulatory approval by ourselves for any of our other product candidates and it is possible that none of our existing product candidates or any of our future product candidates will ever obtain regulatory approval. Furthermore, approval in the United States by the FDA does not ensure approval by regulatory authorities in other countries or jurisdictions, and approval by one foreign regulatory authority does not ensure approval by regulatory authorities in other foreign countries or by the FDA.

Our product candidates could fail to receive regulatory approval for many reasons, including the following:

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We and our collaborators cannot be assured that after spending substantial time and resources, we or our collaborators will obtain regulatory approvals in any desired jurisdiction. Even if we or our collaborators were to obtain approval, regulatory authorities may grant approval contingent on the performance of costly post-marketing clinical trials, or may approve a product candidate with a label that does not include the labeling claims necessary or desirable for the successful commercialization of that product candidate. Significant clinical trial delays could allow our competitors to obtain marketing approval before we or our collaborators do or could in effect shorten the patent protection period during which we may have the exclusive right to commercialize our product candidates. In addition, we or our collaborators may not be able to ultimately achieve the prices intended for our products. In many foreign countries, including those in the European Union, a product candidate must be approved for reimbursement before it can be approved for sale in that country. Any of the foregoing scenarios could materially harm the commercial prospects for our product candidates and our business.

Even if we receive regulatory approval for any of our product candidates we develop independently, we will be subject to ongoing FDA obligations and continued regulatory review in other jurisdictions, which may result in significant additional expense. Additionally, our product candidates, if approved, could be subject to labeling and other restrictions and market withdrawal and we may be subject to penalties if we or our collaborators fail to comply with regulatory requirements or experience unanticipated problems with our products.

Any regulatory approvals that we receive for our product candidates we develop independently may be subject to limitations on the approved indicated uses for which the product may be marketed or subject to certain conditions of approval, or may contain requirements for potentially costly post-marketing testing, including Phase 4 clinical trials, and surveillance to monitor the safety and efficacy of the product candidate.

In addition, if the FDA approves any of our product candidates, the manufacturing processes, labeling, packaging, distribution, adverse event reporting, storage, advertising, promotion and recordkeeping for the product will be subject to extensive and ongoing regulatory requirements. These requirements include submissions of safety and other post-marketing information and reports, as well as continued compliance with current good manufacturing practices, or cGMP, and good clinical practices, or GCP, for any clinical trials that we or our collaborators conduct post-approval. Later discovery of previously unknown problems with a product, including adverse events of unanticipated severity or frequency, or with third-party manufacturers or manufacturing processes, or failure to comply with regulatory requirements, may result in, among other things:

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We cannot predict the likelihood, nature or extent of government regulation that may arise from future legislation or administrative action, either in the United States or abroad. If we or our collaborators are slow or unable to adapt to changes in existing requirements or the adoption of new requirements or policies, or if we or our collaborators are not able to maintain regulatory compliance, our product candidates may lose any marketing approval that may have been obtained and we may not achieve or sustain profitability, which would adversely affect our business.

We, or only AbbVie in the case of ABT-493, may delay or terminate the development of a product candidate at any time if we or AbbVie believe the perceived market or commercial opportunity does not justify further investment, which could materially harm our business and adversely affect our stock price.

Even though the results of preclinical studies and clinical trials that we or AbbVie have conducted or may conduct in the future may support further development of one or more of our product candidates, we, or only AbbVie in the case of ABT-493, may delay, suspend or terminate the future development of a product candidate at any time for strategic, business, financial or other reasons, including the determination or belief that the emerging profile of the product candidate is such that it may not receive regulatory approvals in key markets, gain meaningful market acceptance, otherwise provide any competitive advantages in its intended indication or market or generate a significant return to stockholders. Such a delay, suspension or termination could materially harm our business, results of operations or financial condition. In addition, AbbVie has the right to make decisions regarding the development and commercialization of paritaprevir and ABT-493 without consulting us, and may make decisions with which we do not agree.

Our internal computer systems, or those of our collaborators, CROs or other contractors or consultants, may fail or suffer security breaches, which could result in a material disruption of development programs for our product candidates.

Despite the implementation of security measures, our internal computer systems and those of our collaborators, CROs, and other contractors and consultants are vulnerable to damage from computer viruses, unauthorized access, natural disasters, terrorism, war and telecommunication and electrical failures. While we have not experienced any such system failure, accident or security breach to date, if such an event were to occur and cause interruptions in our operations, it could result in a material disruption of our independent drug development programs or those of our collaborators. For example, the loss of clinical trial data from ongoing or future clinical trials for any of our product candidates could result in delays in regulatory approval efforts and significantly increase costs to recover or reproduce the data. To the extent that any disruption or security breach were to result in a loss of or damage to data or applications, or inappropriate disclosure of confidential or proprietary information, we or our collaborators could incur liability and the further development of our product candidates could be delayed.

Risks Related to Commercialization of Our Product Candidates

Even if AbbVie successfully commercializes ABT-493 in new HCV treatment regimens, or even if we are able to commercialize EDP-494 or any other treatment regimen containing one of our product candidates, the resulting products, as well as AbbVie’s existing products containing paritaprevir, may become subject to unfavorable pricing regulations, third-party reimbursement practices or healthcare reform initiatives in the United States, which would harm our business.

The regulations that govern marketing approvals, pricing and reimbursement for new drug products vary widely from country to country. In the United States, the Patient Protection and Affordable Care Act, as amended by the Health Care and Education Affordability Reconciliation Act of 2010, collectively referred to as the ACA, is significantly changing the way healthcare is financed by both governmental and private insurers. While we cannot predict what impact on federal reimbursement policies this law will have in general or specifically on any product or regimen that we or any of our collaborators commercializes, the ACA may result in downward pressure on pharmaceutical reimbursement, which could negatively affect market acceptance of new products. In addition, although the United States Supreme Court has upheld the constitutionality of most of the ACA, some states have indicated that they intend not to implement certain sections of the ACA, and some members of the U.S. Congress are still working to repeal the ACA. We cannot predict whether these challenges will continue or other proposals will be made or adopted, or what impact these efforts may have on us or AbbVie. AbbVie or any other collaborator’s ability to commercialize any products successfully also will depend in part on the extent to which reimbursement for these products and related treatments will be available from government health administration authorities, private health insurers and other organizations. Government authorities and third-party payors, such as private health insurers and health maintenance organizations, decide which medications they will pay for and establish reimbursement levels. A primary trend in the U.S. healthcare industry is cost containment. Government authorities and third-party payors have attempted to control costs by limiting coverage and the amount of reimbursement for particular medications. In the case of HCV, limitations of coverage have recently been used to limit access to HCV treatments only for those patients with more advanced fibrosis. Increasingly, third-party payors are requiring that drug companies provide them with predetermined discounts from list prices and, in many cases involving HCV drugs, seeking discounts in exchange for greater patient access to a particular HCV drug. In addition, there are private and public payors challenging the prices charged for medical products. We cannot be sure that reimbursement will be available for any product that we or any collaborator commercialize and, if reimbursement is available, the level of reimbursement. In

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addition, reimbursement may impact the demand for, or the price of, any product candidate for which we or a collaborator obtains marketing approval. If reimbursement is not available or is available only to limited levels, we or AbbVie may not be able to successfully commercialize any product candidate for which marketing approval is obtained.

There may be significant delays in obtaining reimbursement for newly approved drugs, and coverage may be more limited than the purposes for which the drug is approved by the FDA or comparable authorities in other jurisdictions. Moreover, eligibility for reimbursement does not imply that any drug will be paid for in all cases or at a rate that covers our costs, including research, development, manufacture, sale and distribution. Interim reimbursement levels for new drugs, if applicable, may also be insufficient to cover our and any collaborator’s costs and may not be made permanent. Reimbursement rates may vary according to the use of the drug and the clinical setting in which it is used, may be based on reimbursement levels already set for lower cost drugs and may be incorporated into existing payments for other services. Net prices for drugs may be reduced by mandatory discounts or rebates required by government healthcare programs or private payors and by any future relaxation of laws that presently restrict imports of drugs from countries where they may be sold at lower prices than in the United States. Third-party payors often rely upon Medicare coverage policy and payment limitations in setting their own reimbursement policies. Our or any collaborator’s inability to promptly obtain coverage and profitable payment rates from both government-funded and private payors for any approved products that any collaborator or we develop could have a material adverse effect on our operating results, our ability to raise capital needed to commercialize products and our overall financial condition.

If, in the future, we are unable to establish our own sales, marketing and distribution capabilities or enter into licensing or collaboration agreements for these purposes, we may not be successful in commercializing any future product candidates.

We do not have a sales or marketing infrastructure and have no sales, marketing or distribution experience. We will seek to either build our own commercial infrastructure to commercialize any future products if and when they are approved, or enter into licensing or collaboration agreements where our collaborator is responsible for commercialization, as in the case of our collaboration with AbbVie, or where we have the right to assist in the future development and commercialization of such products.

To develop internal sales, distribution and marketing capabilities, we will have to invest significant amounts of financial and management resources, some of which will be committed prior to any confirmation that any of our proprietary product candidates will be approved. For product candidates for which we decide to perform sales, marketing and distribution functions ourselves, we could face a number of additional risks, including:

Where and when appropriate, we may elect to utilize contract sales forces or distribution partners to assist in the commercialization of our product candidates. If we enter into arrangements with third parties to perform sales, marketing and distribution services for our products, the resulting revenues or the profitability from these revenues to us are likely to be lower than if we had sold, marketed and distributed our products ourselves. In addition, we may not be successful in entering into arrangements with third parties to sell, market and distribute our product candidates or may be unable to do so on terms that are favorable to us. We likely will have little control over such third parties, and any of these third parties may fail to devote the necessary resources and attention to sell, market and distribute our products effectively.

If we do not establish sales, marketing and distribution capabilities successfully, either on our own or in collaboration with third parties, we will not be successful in commercializing our product candidates.

Our commercial success depends upon significant market acceptance among physicians, patients and healthcare payors of products containing paritaprevir or ABT-493 as well as similar market acceptance of any future product candidates we plan to develop independently or in collaboration with others.

Paritaprevir, ABT-493, as well as EDP-494 or any other product candidate that we may develop in the future that obtains regulatory approval, whether as part of a combination therapy or as a monotherapy, may not gain market acceptance among physicians, healthcare payors, patients and the medical community. For example, the standard of care in HCV is likely to continue to evolve

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rapidly as many new product candidates are being developed and tested. The degree of market acceptance of any product for which we or any collaborator of ours receives approval for commercial sale depends on a number of factors, including:

If treatment regimens containing one of our product candidates are approved and then fail to achieve market acceptance, we may not be able to generate significant additional revenue. Further, if new, more favorably received therapies are introduced after any such regimen achieves market acceptance, then we may not be able to maintain that market acceptance over time.

Foreign governments tend to impose strict price controls, which may adversely affect our future profitability.

In most foreign countries, particularly in the European Union, prescription drug pricing and/or reimbursement is subject to governmental control. In those countries that impose price controls, pricing negotiations with governmental authorities can take considerable time after the receipt of marketing approval for a product. To obtain reimbursement or pricing approval in some countries, we or our collaborators may be required to conduct a clinical trial that compares the cost-effectiveness of our product candidate to other available therapies.

Some countries require approval of the sale price of a drug before it can be marketed. In many countries, the pricing review period begins after marketing or product licensing approval is granted. In some foreign markets, prescription pharmaceutical pricing remains subject to continuing governmental control even after initial approval is granted. As a result, we or our collaborators might obtain marketing approval for a product in a particular country, but then be subject to price regulations that delay commercial launch of the product, possibly for lengthy time periods, and negatively impact the revenues that are generated from the sale of the product in that country. If reimbursement of our products is unavailable or limited in scope or amount, or if pricing is set at unsatisfactory levels, or if there is competition from lower priced cross-border sales, our results of operations will be negatively affected.

Risks Related to Our Dependence on Third Parties

We may not be successful in establishing new product collaborations, which could adversely affect our ability to develop and commercialize one or more of our future product candidates. If we are unsuccessful in maintaining or forming alliances on favorable terms, our business may not succeed.

We may seek to enter into additional product collaborations in the future, including alliances with other biotechnology or pharmaceutical companies, to enhance and accelerate the development and commercialization of one or more of our future product

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candidates. We face significant competition in seeking appropriate collaborators and the negotiation process is time-consuming and complex. Moreover, we may not be successful in our efforts to establish other product collaborations or other alternative arrangements for any future product candidates and programs because our research and development pipeline may be insufficient, our product candidates and programs may be deemed to be at too early of a stage of development for collaborative effort and/or third parties may not view our product candidates and programs as having the requisite potential to demonstrate safety and efficacy. Even if we are successful in our efforts to establish product collaborations, the terms that we agree upon may not be favorable to us and we may not be able to maintain such product collaborations if, for example, development or approval of a product candidate is delayed or sales of an approved product are disappointing.

If our existing collaboration agreement with AbbVie is terminated, or if we determine that entering into other product collaborations is in our best interest but we either fail to enter into, delay in entering into or fail to maintain such collaborations:

We intend to rely on third-party manufacturers to produce our clinical product candidate supplies and any commercial supplies of any approved future product candidates. Any failure by a third-party manufacturer to produce acceptable supplies for us may delay or impair our ability to initiate or complete our clinical trials or sell any resulting product.

We do not currently own or operate any manufacturing facilities. We plan to continue to work with third-party contract manufacturers to produce sufficient quantities of any future product candidates for preclinical testing, clinical trials and commercialization. If we are unable to arrange for such a third-party manufacturing source for any of our product candidates, or fail to do so on commercially reasonable terms, we may not be able to successfully produce, develop and market one or more of our future product candidates, or we may be delayed in doing so.

Reliance on third-party manufacturers entails risks to which we would not be subject if we manufactured product candidates ourselves, including reliance on the third party for regulatory compliance and quality control and assurance, volume production, the possibility of breach of the manufacturing agreement by the third party because of factors beyond our control (including a failure to synthesize and manufacture our product candidates in accordance with our product specifications) and the possibility of termination or nonrenewal of the agreement by the third party at a time that is costly or damaging to us. In addition, the FDA and other regulatory authorities require that our product candidates be manufactured according to cGMP and similar foreign standards. Pharmaceutical manufacturers and their subcontractors are required to register their facilities and/or products manufactured at the time of submission of the marketing application and then annually thereafter with the FDA and certain state and foreign agencies. They are also subject to periodic unannounced inspections by the FDA, state and other foreign authorities. Any subsequent discovery of problems with a product, or a manufacturing or laboratory facility used by us or our collaborators, may result in restrictions on the product or on the manufacturing or laboratory facility, including marketed product recall, suspension of manufacturing, product seizure, or a voluntary withdrawal of the drug from the market. Any failure by our third-party manufacturers to comply with cGMP or failure to scale up manufacturing processes, including any failure to deliver sufficient quantities of product candidates in a timely manner, could lead to a delay in, or failure to obtain, regulatory approval of any of our product candidates.

We plan to rely on third-party manufacturers to purchase from third-party suppliers the materials necessary to produce our future product candidates for our clinical studies. There are a small number of suppliers for certain capital equipment and materials that we plan to use to manufacture our drugs. Such suppliers may not sell these materials to our manufacturers at the times we need them or on commercially reasonable terms. Moreover, we currently do not have any agreements for the production of these materials. Although we do not intend to begin a clinical trial unless we believe we have a sufficient supply of a product candidate to complete the clinical trial, any significant delay in the supply of a product candidate or the material components thereof for an ongoing clinical trial due to the need to replace a third-party manufacturer could considerably delay completion of our clinical studies, product testing and potential regulatory approval of our product candidates. If our manufacturers or we are unable to purchase these materials after regulatory approval has been obtained for our product candidates, the commercial launch of our product candidates would be delayed or there would be a shortage in supply, which would impair our ability to generate revenue from the sale of our product candidates.

Contract manufacturers may not be able to manufacture our product candidates at a cost or in quantities or in a timely manner necessary to develop and commercialize them. If we successfully commercialize any of our product candidates, to meet our projected needs we may need to find third parties that will increase their scale of production, or we may have to establish or access large-scale commercial manufacturing capabilities. We may require additional funds, personnel and other resources to build, lease or operate any manufacturing facility.

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A portion of our research and a portion of our manufacturing of certain key intermediates used in the manufacture of the active pharmaceutical ingredients for our future product candidates takes place in China through third-party researchers and manufacturers, a significant disruption in the operation of those researchers or manufacturers or political unrest in China could materially adversely affect our business, financial condition and results of operations.

Although manufacturing for our lead product candidates paritaprevir and ABT-493 is being conducted by AbbVie, we have relied on third parties located in China to manufacture and supply certain key intermediates used in the manufacture of our active pharmaceutical ingredients, or API, for our research product candidates, and we expect to continue to use such third party manufacturers for such intermediates for any future product candidates we develop independently. Any disruption in production or inability of our manufacturers in China to produce adequate quantities to meet our needs, whether as a result of a natural disaster or other causes, could impair our ability to operate our business on a day-to-day basis and to continue our research and development of our future product candidates. We also use contract researchers in China to conduct a portion of our search for our early stage programs. Any disruption in the team conducting that research could cause delays in one or more of our research programs and could require us to curtail one or more programs, at least until we could contract for that research to be done elsewhere. Furthermore, since these researchers and manufacturers are located in China, we are exposed to the possibility of product supply disruption and increased costs in the event of changes in the policies of the Chinese government, political unrest or unstable economic conditions in China. Any of these matters could materially and adversely affect our business and results of operations. Any recall of the manufacturing lots or similar action regarding our API used in clinical trials could delay the trials or detract from the integrity of the trial data and its potential use in future regulatory filings. In addition, manufacturing interruptions or failure to comply with regulatory requirements by any of these manufacturers could significantly delay clinical development of potential products and reduce third-party or clinical researcher interest and support of proposed trials. These interruptions or failures could also impede commercialization of our future product candidates and impair our competitive position. Further, we may be exposed to fluctuations in the value of the local currency in China. Future appreciation of the local currency could increase our costs. In addition, our labor costs could continue to rise as wage rates increase due to increased demand for skilled laborers and the availability of skilled labor declines in China.

We will rely on third parties to monitor, support, conduct and/or oversee clinical trials of our future product candidates that we develop independently and, in some cases, to maintain regulatory files for those product candidates. If we are not able to maintain or secure agreements with such third parties on acceptable terms, if these third parties do not perform their services as required, or if these third parties fail to timely transfer any regulatory information held by them to us, we may not be able to obtain regulatory approval for, or commercialize, our product candidates.

We will rely on CROs, hospitals, clinics, academic institutions and other third-party collaborators who are outside our control to monitor, support, conduct and/or oversee preclinical and clinical studies of our future product candidates. We will also rely on third parties to perform clinical trials of our future product candidates when they reach that stage. As a result, we have less control over the timing and cost of these studies and the ability to recruit trial subjects than if we conducted these trials wholly by ourselves. If we are unable to maintain or enter into agreements with these third parties on acceptable terms, or if any such engagement is terminated, we may be unable to enroll patients on a timely basis or otherwise conduct our trials in the manner we anticipate. In addition, there is no guarantee that these third parties will devote adequate time and resources to our studies or perform as required by a contract or in accordance with regulatory requirements, including maintenance of clinical trial information regarding our future product candidates. If these third parties fail to meet expected deadlines, fail to timely transfer to us any regulatory information, fail to adhere to protocols or fail to act in accordance with regulatory requirements or our agreements with them, or if they otherwise perform in a substandard manner or in a way that compromises the quality or accuracy of their activities or the data they obtain, then clinical trials of our future product candidates may be extended, delayed or terminated, or our data may be rejected by the FDA or regulatory agencies.

To the extent we elect to enter into additional licensing or collaboration agreements to partner our future product candidates, our dependence on such relationships may adversely affect our business.

Our commercialization strategy for some of our future product candidates may depend on our ability to enter into collaboration agreements with other companies to obtain access to other compounds for use in combination with any of our product candidates or for assistance and funding for the development and potential commercialization of any of these product candidates, similar to what we have done with AbbVie. Supporting diligence activities conducted by potential collaborators and negotiating the financial and other terms of a collaboration agreement are long and complex processes with uncertain results. Even if we are successful in entering into one or more additional collaboration agreements, collaborations can involve greater uncertainty for us, as we may have limited or no control over certain aspects of our collaborative programs. We may determine that continuing a collaboration under the terms provided is not in our best interest, and we may terminate the collaboration. Our collaborators could delay or terminate their agreements with us, and our product candidates subject to collaborative arrangements may never be successfully commercialized.

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Further, our collaborators may develop alternative products or pursue alternative technologies either on their own or in collaboration with others, including our competitors, and the priorities or focus of our collaborators may shift such that our programs receive less attention or resources than we would like, or they may be terminated altogether. Any such actions by our collaborators may adversely affect our business prospects and ability to earn revenue. In addition, we could have disputes with our collaborators, such as the interpretation of terms in our agreements. Any such disagreements could lead to delays in the development or commercialization of any potential products or could result in time-consuming and expensive litigation or arbitration, which may not be resolved in our favor.

Even with respect to programs that we intend to commercialize ourselves, we may enter into agreements with collaborators to share in the burden of conducting clinical trials, manufacturing and marketing our product candidates or products. In addition, our ability to apply our proprietary technologies to develop proprietary compounds will depend on our ability to establish and maintain licensing arrangements or other collaborative arrangements with the holders of proprietary rights to such compounds. We may not be able to establish such arrangements on favorable terms or at all, and our collaborative arrangements may not be successful.

Risks Related to Our Intellectual Property Rights

We could be unsuccessful in obtaining or maintaining adequate patent protection for one or more of our product candidates.

Our commercial success will depend, in large part, on our ability to obtain and maintain patent and other intellectual property protection with respect to our product candidates. We cannot be certain that patents will be issued or granted with respect to our patent applications that are currently pending, or that issued or granted patents will not later be found to be invalid and/or unenforceable, be interpreted in a manner that does not adequately protect our products, or otherwise provide us with any competitive advantage. The patent position of biotechnology and pharmaceutical companies is generally uncertain because it involves complex legal and factual considerations. The standards applied by the United States Patent and Trademark Office and foreign patent offices in granting patents are not always applied uniformly or predictably. For example, there is no uniform worldwide policy regarding patentable subject matter or the scope of claims allowable in biotechnology and pharmaceutical patents. Consequently, patents may not issue from our pending patent applications. As such, we do not know the degree of future protection that we will have on our proprietary products and technology, if any, and a failure to obtain adequate intellectual property protection with respect to our product candidates and proprietary technology could have a material adverse impact on our business.

In addition, certain of our activities have been funded, and may in the future be funded, by the United States federal government. For example, the preclinical and early clinical development of our lead antibiotic candidate, which we are no longer developing, was funded under a contract with NIAID, an entity of the United States federal government. When new technologies are developed with United States federal government funding, the government obtains certain rights in any resulting patents, including a nonexclusive license authorizing the government to use the invention for non-commercial purposes. These rights may permit the government to disclose our confidential information to third parties and to exercise “march-in” rights to use or allow third parties to use our patented technology. The government can exercise its march-in rights if it determines that action is necessary because we fail to achieve practical application of the United States government-funded technology, or because action is necessary to alleviate health or safety needs, to meet requirements of federal regulations or to give preference to United States industry. In addition, United States government-funded inventions must be reported to the government and United States government funding must be disclosed in any resulting patent applications. In addition, our rights in such inventions are subject to certain requirements to manufacture products in the United States.

Issued patents covering one or more of our product candidates could be found invalid or unenforceable if challenged in court.

Despite measures we take to obtain patent and other intellectual property protection with respect to our product candidates and proprietary technology, any of our intellectual property rights could be challenged or invalidated. For example, if we were to initiate legal proceedings against a third party to enforce a patent covering one of our product candidates, the defendant could counterclaim that our patent is invalid and/or unenforceable. In patent litigation in the United States and in some other jurisdictions, defendant counterclaims alleging invalidity and/or unenforceability are commonplace. Grounds for a validity challenge could be an alleged failure to meet any of several statutory requirements, for example, lack of novelty, obviousness or non-enablement. Grounds for an unenforceability assertion could be an allegation that someone connected with prosecution of the patent withheld relevant information from the United States Patent and Trademark Office, or the applicable foreign counterpart, or made a misleading statement, during prosecution. Although we believe that we have conducted our patent prosecution in accordance with the duty of candor and in good faith, the outcome following legal assertions of invalidity and unenforceability during patent litigation is unpredictable. With respect to the validity question, for example, we cannot be certain that there is no invalidating prior art, of which we and the patent examiner

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were unaware during prosecution. If a defendant were to prevail on a legal assertion of invalidity and/or unenforceability, we would lose at least part, and perhaps all, of the patent protection on a product candidate. Even if a defendant does not prevail on a legal assertion of invalidity and/or unenforceability, our patent claims may be construed in a manner that would limit our ability to enforce such claims against the defendant and others. Any loss of patent protection could have a material adverse impact on one or more of our product candidates and our business.

Enforcing our intellectual property rights against third parties may also cause such third parties to file other counterclaims against us, which could be costly to defend and could require us to pay substantial damages, cease the sale of certain products or enter into a license agreement and pay royalties (which may not be possible on commercially reasonable terms or at all). Any efforts to enforce our intellectual property rights are also likely to be costly and may divert the efforts of our scientific and management personnel.

Claims that our product candidates or the sale or use of our future products infringe the patent or other intellectual property rights of third parties could result in costly litigation or could require substantial time and money to resolve, even if litigation is avoided.

Our commercial success depends upon our ability to develop, manufacture, market and sell our product candidates and use our proprietary technology without infringing the intellectual property rights of others. We cannot guarantee that our product candidates or any uses of our product candidates do not and will not in the future infringe third-party patents or other intellectual property rights. Third parties might allege that we or our collaborators are infringing their patent rights or that we have misappropriated their trade secrets, or that we are otherwise violating their intellectual property rights, whether with respect to the manner in which we have conducted our research or to the composition, use or manufacture of the compounds we have developed or are developing with our collaborators. Such third parties might resort to litigation against us or other parties we have agreed to indemnify, which litigation could be based on either existing intellectual property or intellectual property that arises in the future.

It is also possible that we failed to identify, or may in the future fail to identify, relevant patents or patent applications held by third parties that cover our product candidates. For example, applications filed before November 29, 2000 and certain applications filed after that date that will not be filed outside the United States remain confidential until patents issue. Other patent applications in the United States and several other jurisdictions are published approximately 18 months after the earliest filing for which priority is claimed, with such earliest filing date being commonly referred to as the priority date. Furthermore, publication of discoveries in the scientific or patent literature often lags behind actual discoveries. Therefore, we cannot be certain that we or our collaborators were the first to invent, or the first to file patent applications on, our product candidates or for their uses, or that our product candidates will not infringe patents that are currently issued or that are issued in the future. In the event that a third party has also filed a patent application covering one of our product candidates or a similar invention, we may have to participate in an adversarial proceeding, known as an interference, declared by the U.S. Patent and Trademark Office or its foreign counterpart to determine priority of invention. Additionally, pending patent applications which have been published can, subject to certain limitations, be later amended in a manner that could cover our products or their use.

In order to avoid or settle potential claims with respect to any patent or other intellectual property rights of third parties, we may choose or be required to seek a license from a third party and be required to pay license fees or royalties or both, which could be substantial. These licenses may not be available on acceptable terms, or at all. Even if we or any future collaborators were able to obtain a license, the rights may be nonexclusive, which could result in our competitors gaining access to the same intellectual property. Ultimately, we could be prevented from commercializing a product, or be forced, by court order or otherwise, to cease some or all aspects of our business operations, if, as a result of actual or threatened patent or other intellectual property claims, we are unable to enter into licenses on acceptable terms. Further, we could be found liable for significant monetary damages as a result of claims of intellectual property infringement. For example, we have received, and may in the future receive, offers to license and demands to license from third parties claiming that we are infringing their intellectual property or owe license fees and, even if such claims are without merit, there can be no assurance that we will successfully avoid or settle such claims.

In addition, if AbbVie licenses or otherwise acquires rights to intellectual property controlled by a third party in various circumstances, for example, where a product could not be legally developed or commercialized in a country without the third-party intellectual property right, it is entitled under our collaboration agreement to decrease payments payable to us on a product-by-product basis and, in certain cases, on a country-by-country basis. Any of the foregoing events could harm our business significantly.

Defending against claims of patent infringement, misappropriation of trade secrets or other violations of intellectual property rights could be costly and time consuming, regardless of the outcome. Thus, even if we were to ultimately prevail, or to settle at an early stage, such litigation could burden us with substantial unanticipated costs. In addition, litigation or threatened litigation could result in significant demands on the time and attention of our management team, distracting them from the pursuit of other company business. Claims that our product candidates or the sale or use of our future products infringe, misappropriate or otherwise violate third-party intellectual property rights could therefore have a material adverse impact on our business.

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Unfavorable outcomes in intellectual property litigation could limit our research and development activities and/or our ability to commercialize certain products.

If third parties successfully assert their intellectual property rights against us, we might be barred from using certain aspects of our technology, or barred from developing and commercializing certain products. Prohibitions against using certain technologies, or prohibitions against commercializing certain products, could be imposed by a court or by a settlement agreement between us and a plaintiff. In addition, if we are unsuccessful in defending against allegations that we have infringed, misappropriated or otherwise violated patent or other intellectual property rights of others, we may be forced to pay substantial damage awards to the plaintiff. There is inevitable uncertainty in any litigation, including intellectual property litigation. There can be no assurance that we would prevail in any intellectual property litigation, even if the case against us is weak or flawed. If litigation leads to an outcome unfavorable to us, we may be required to obtain a license from the intellectual property owner in order to continue our research and development programs or to market any resulting product. It is possible that the necessary license will not be available to us on commercially acceptable terms, or at all. Alternatively, we may be required to modify or redesign our products in order to avoid infringing or otherwise violating third-party intellectual property rights. This may not be technically or commercially feasible, may render our products less competitive, or may delay or prevent the entry of our products to the market. Any of the foregoing could limit our research and development activities, our ability to commercialize one or more product candidates, or both.

Most of our competitors are larger than we are and have substantially greater resources. They are, therefore, likely to be able to sustain the costs of complex intellectual property litigation longer than we could. In addition, the uncertainties associated with litigation could have a material adverse effect on our ability to raise the funds necessary to conduct our clinical trials, continue our internal research programs, in-license needed technology, or enter into strategic partnerships that would help us bring our product candidates to market.

In addition, any future intellectual property litigation, interference or other administrative proceedings will result in additional expense and distraction of our personnel. An adverse outcome in such litigation or proceedings may expose us or any future strategic partners to loss of our proprietary position, expose us to significant liabilities, or require us to seek licenses that may not be available on commercially acceptable terms, if at all, each of which could have a material adverse effect on our business.

Intellectual property litigation may lead to unfavorable publicity that harms our reputation and causes the market price of our common stock to decline.

During the course of any intellectual property litigation, there could be public announcements of the results of hearings, rulings on motions, and other interim proceedings in the litigation. If securities analysts or investors regard these announcements as negative, the perceived value of our products, programs or intellectual property could be diminished. Accordingly, the market price of our common stock may decline. Such announcements could also harm our reputation or the market for our future products, which could have a material adverse effect on our business.

Confidentiality agreements with employees and third parties may not prevent unauthorized disclosure of trade secrets and other proprietary information.

In addition to patents, we rely on trade secrets, technical know-how and proprietary information concerning our business strategy and product candidates in order to protect our competitive position in the field of HCV, other antivirals and liver disease. In the course of our research and development activities and our business activities, we often rely on confidentiality agreements to protect our proprietary information. Such confidentiality agreements are used, for example, when we talk to vendors of laboratory or clinical development services or potential strategic partners. In addition, each of our employees is required to sign a confidentiality agreement and invention assignment agreement upon joining our company. We take steps to protect our proprietary information, and our confidentiality agreements and invention assignment agreements are carefully drafted to protect our proprietary interests. Nevertheless, there can be no guarantee that an employee or an outside party will not make an unauthorized disclosure of our proprietary confidential information. This might happen intentionally or inadvertently. It is possible that a competitor will make use of such information, and that our competitive position will be compromised, in spite of any legal action we might take against persons making such unauthorized disclosures. In addition, to the extent that our employees, consultants or contractors use intellectual property owned by others in their work for us, disputes may arise as to the rights in related or resulting know-how and inventions.

Trade secrets are difficult to protect. Although we use reasonable efforts to protect our trade secrets, our employees, consultants, contractors, business partners or outside scientific collaborators might intentionally or inadvertently disclose our trade secret information to competitors or our trade secrets may otherwise be misappropriated. Enforcing a claim that a third party illegally obtained and is using any of our trade secrets is expensive and time consuming, and the outcome is unpredictable. In addition, courts outside the United States sometimes are less willing than United States courts to protect trade secrets. Moreover, our competitors may independently develop equivalent knowledge, methods and know-how.

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Our collaborators may have rights to publish data and other information to which we have rights. In addition, we sometimes engage individuals or entities to conduct research relevant to our business. The ability of these individuals or entities to publish or otherwise publicly disclose data and other information generated during the course of their research is subject to certain contractual limitations. These contractual provisions may be insufficient or inadequate to protect our confidential information. If we do not apply for patent protection prior to such publication, or if we cannot otherwise maintain the confidentiality of our proprietary technology and other confidential information, then our ability to obtain patent protection or to protect our trade secret information may be jeopardized, which could adversely affect our business.

Intellectual property rights do not necessarily protect us from all potential threats to our competitive advantage.

The degree of future protection afforded by our intellectual property rights is uncertain because intellectual property rights have limitations, and may not adequately protect our business, or permit us to maintain our competitive advantage. The following examples are illustrative:

Any of the aforementioned threats to our competitive advantage could have a material adverse effect on our business.

Changes in patent law could diminish the value of patents in general, thereby impairing our ability to protect our products.

As is the case with many other biopharmaceutical companies, our success is heavily dependent on intellectual property, particularly patents. Obtaining, maintaining and enforcing patents in the biopharmaceutical industry involves both technological complexity and legal complexity. Therefore, obtaining, maintaining and enforcing biopharmaceutical patents is costly, time-consuming and inherently uncertain. In addition, recent legislative and judicial developments in the United States and elsewhere have in some cases narrowed the protection afforded to patent owners, made patents more difficult to obtain, or increased the uncertainty regarding the ability to obtain, maintain and enforce patents. For example, Congress recently passed patent reform legislation, and may pass patent reform

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legislation in the future. The United States Supreme Court has ruled on several patent cases in recent years, and in certain circumstances has narrowed the scope of patent protection available or otherwise weakened the rights of patent owners. In addition to increasing uncertainty with regard to our ability to obtain patents in the future, this combination of events has created uncertainty with respect to the value of patents, once obtained. Depending on decisions and actions by the United States Congress, the federal courts, the United States Patent and Trademark Office, and their respective foreign counterparts, the laws and regulations governing patents could change in unpredictable ways that could weaken our ability to obtain new patents or to maintain and enforce our existing patents and patents that we might obtain in the future.

Risks Related to Industry

Unstable market and economic conditions may have serious adverse consequences on our business, financial condition and stock price.

As has been widely reported, global credit and financial markets have been experiencing extreme disruptions over the past several years, including declines in consumer confidence, declines in economic growth, and uncertainty about economic stability. There can be no assurance that deterioration in credit and financial markets and confidence in economic conditions will not occur. Our general business strategy may be adversely affected by the volatile business environment and continued unpredictable and unstable market conditions, particularly for securities of biotechnology companies such as our common stock. There is a possibility that our stock price may decline, due in part to the volatility of the stock market and any general economic downturn. If the current equity and credit markets become more volatile, deteriorate or do not improve, it may make any debt or equity financing more difficult to secure, more costly and/or more dilutive if our circumstances change and we seek such financing. Failure to secure any necessary financing in a timely manner and on favorable terms could have a material adverse effect on our growth strategy, financial performance and stock price and could require us to delay or abandon our business and clinical development plans. In addition, there is a risk that one or more of our current service providers, manufacturers and other partners may not survive these difficult economic times, which could directly affect our ability to attain our operating goals on schedule and on budget.

If product liability lawsuits are brought against us, we may incur substantial liabilities and may be required to limit commercialization of our product candidates.

We face an inherent risk of product liability as a result of the clinical testing of our product candidates, and we will face an even greater risk if we commercialize any product candidates. For example, we may be sued if any of our product candidates, including any that are developed in combination therapies, allegedly causes injury or is found to be otherwise unsuitable during product testing, manufacturing, marketing or sale. Any such product liability claims may include allegations of defects in manufacturing, defects in design, a failure to warn of dangers inherent in the product, negligence, strict liability and a breach of warranties. Claims could also be asserted under state consumer protection acts. If we cannot successfully defend ourselves against product liability claims, we may incur substantial liabilities or be required to limit commercialization of our product candidates. Even successful defense would require significant financial and management resources. There is also risk that third parties we have agreed to indemnify could incur liability.

Regardless of the merits or eventual outcome, liability claims may result in:

Our inability to obtain and retain sufficient product liability insurance at an acceptable cost to protect against potential product liability claims could prevent or inhibit the commercialization of products we develop. We currently carry product liability insurance covering our clinical studies in the amount of $5.0 million in the aggregate. Although we maintain such insurance, any claim that may be brought against us could result in a court judgment or settlement in an amount that is not covered, in whole or in part, by our insurance

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or that is in excess of the limits of our insurance coverage. Our insurance policies also have various exclusions, and we may be subject to a product liability claim for which we have no coverage. We will have to pay any amounts awarded by a court or negotiated in a settlement that exceed our coverage limitations or that are not covered by our insurance, and we may not have, or be able to obtain, sufficient capital to pay such amounts.

Our relationships with customers and third-party payors in the United States and elsewhere will be subject to applicable anti-kickback, fraud and abuse and other healthcare laws and regulations, which could expose us to criminal sanctions, civil penalties, contractual damages, reputational harm and diminished profits and future earnings.

Healthcare providers, physicians and third-party payors in the United States and elsewhere play a primary role in the recommendation and prescription of any product candidates for which we obtain marketing approval. Our future arrangements with third-party payors and customers may expose us to broadly applicable fraud and abuse and other healthcare laws and regulations that may constrain the business or financial arrangements and relationships through which we market, sell and distribute our products for which we obtain marketing approval. Restrictions under applicable federal, state and foreign healthcare laws and regulations include the following:

Efforts to ensure that our business arrangements with third parties will comply with applicable healthcare laws and regulations will involve substantial costs. It is possible that governmental authorities will conclude that our business practices may not comply with current or future statutes, regulations or case law involving applicable fraud and abuse or other healthcare laws and regulations. If our operations are found to be in violation of any of these laws or any other governmental regulations that may apply to us, we may be subject to significant civil, criminal and administrative penalties, damages, fines, exclusion from government funded healthcare programs, such as Medicare and Medicaid, and the curtailment or restructuring of our operations, which could have a material adverse effect on our business. If any of the physicians or other providers or entities with whom we expect to do business, including our collaborators, are found not to be in compliance with applicable laws, they may be subject to criminal, civil or administrative sanctions, including exclusions from government funded healthcare programs, which could also materially affect our business.

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If we fail to comply with environmental, health and safety laws and regulations, we could become subject to fines or penalties or incur costs that could have a material adverse effect on the success of our business.

We are subject to numerous environmental, health and safety laws and regulations, including those governing laboratory procedures and the handling, use, storage, treatment and disposal of hazardous materials and wastes. Our operations involve the use of hazardous and flammable materials, including chemicals. Our operations also produce hazardous waste products. We generally contract with third parties for the disposal of these materials and wastes. We cannot eliminate the risk of contamination or injury from these materials. In the event of contamination or injury resulting from our use of hazardous materials or our or third parties’ disposal of hazardous materials, we could be held liable for any resulting damages, and any liability could exceed our resources. We also could incur significant costs associated with civil or criminal fines and penalties.

We may incur substantial costs in order to comply with current or future environmental, health and safety laws and regulations. These current or future laws and regulations may impair our research, development or production efforts. Failure to comply with these laws and regulations also may result in substantial fines, penalties or other sanctions.

We maintain workers’ compensation insurance to cover us for costs and expenses we may incur due to injuries to our employees resulting from the use of hazardous materials. This insurance may not provide adequate coverage against potential liabilities. We do not maintain insurance for environmental liability or toxic tort claims that may be asserted against us in connection with our storage or disposal of hazardous or radioactive materials.

Risks Related to Our Common Stock

Our stock price has been, and is likely to continue to be, volatile, and thus our stockholders could incur substantial losses.

Our stock price has been volatile and could be subject to wide fluctuations in response to various factors, many of which are beyond our control. Since our initial public offering in March 2013, the price of our common stock on The NASDAQ Global Select Market has ranged from $16.49 to $52.58. The stock market in general and the market for biopharmaceutical companies, and for those developing potential therapies for HCV in particular, have experienced extreme volatility that has often been unrelated to the operating performance of particular companies. As a result of this volatility, you may not be able to sell your common stock at or above your purchase price, if at all. The market price for our common stock may be influenced by many factors, including: