Item 7. Management’s Discussion and Analysis of Financial Condition and Results of Operation

The following discussion and analysis of our financial condition and results of operations should be read in conjunction with “Selected Financial Data”, our consolidated financial statements and the related notes thereto and other financial information appearing elsewhere in this Annual Report on Form 10-K. The following discussion contains forward-looking statements that involve risks and uncertainties. Our actual results could differ materially from those expressed or implied in any forward-looking statements as a result of various factors, including those set forth in this Form 10-K under “Item 1A. Risk Factors.”

Overview

We are a clinical-stage biotechnology company advancing a novel class of oral therapeutic candidates for the treatment of chronic hepatitis B virus (HBV) infection. According to the World Health Organization (WHO), approximately 270 million people worldwide are chronically infected with HBV. Our research and development programs are pursuing multiple drug candidates designed to inhibit the HBV replication cycle and block the generation of covalently closed circular DNA (cccDNA), with the aim of discovering and developing finite and curative therapies for patients with HBV. We have discovered several novel core inhibitors, which are small molecules that directly target and allosterically modulate the HBV core (HBc) protein in a way that affects assembly and stability of HBV nucleocapsids.

The ongoing COVID-19 pandemic has affected certain aspects of our business. As further detailed below, those effects have been primarily limited to where and how our employees work in our labs and offices. To date, our current and future planned clinical trials and pre-clinical studies have not been subject to significant impact as a result of the COVID-19 pandemic.

As previously announced, in January 2021, we wound down our Microbiome program to prioritize and focus our resources on discovering and developing finite and curative therapies for HBV. Our Microbiome program had been developing a novel class of oral live microbial biotherapeutics candidates designed to treat disorders associated with the microbiome.

Our Primary Focus: Targeting HBV Core Protein to Achieve a Cure

HBV is a DNA virus that infects hepatocytes and establishes a reservoir of cccDNA, a unique DNA moiety that resides in the cell nucleus of HBV-infected hepatocytes and is associated with viral persistence and chronic infection. No currently approved oral therapies target cccDNA activity directly, which makes molecules that can modulate cccDNA generation or disrupt its function highly sought in the HBV field. As a result, most of our research and development efforts to date have focused on discovering and developing compounds targeting the core protein, a highly conserved viral structural protein that has no human homologue and is involved in numerous aspects of the HBV replication cycle, including the generation of HBV cccDNA. Through our research efforts, we have discovered several chemically distinct series of small molecule core inhibitors that directly target and allosterically inhibit core protein functions.

Vebicorvir

Vebicorvir (VBR), our lead core inhibitor product candidate, is licensed from Indiana University. The conduct of the Phase 2 studies, Study 201 and 202 and our open-label extension study, Study 211, are all complete. We presented interim updates on our clinical studies at a variety of conferences, including at the European Association for the Study of the Liver’s (EASL) Digital International Liver CongressTM in August 2020 and the American Association for the Study of Liver Diseases (AASLD) Annual Meeting in November 2020.

Our most recently completed study for VBR, Study 211, involved transitioning patients who met the requisite stopping criteria, as determined with our lead investigators and the U.S. Food and Drug Administration (FDA), off of therapy to test for sustained virologic response (SVR). SVR refers to sustained viral suppression (more than six months) of HBV DNA below the lower limit of quantification (LLOQ) and would be consistent with a successful finite treatment for HBV. In November 2020, it became clear that patients who stopped therapy in Study 211 had not achieved meaningful SVR rates as 39 of 41 patients relapsed, meaning they had detectable HBV. We continue to collect and analyze Study 211 data and intend to submit more detailed findings to a future medical meeting; however, it is clear that combination therapy of VBR plus nucelos(t)ide analog reverse transcriptase inhibitors (NrtI) alone is not sufficient to cure HBV. Based on these results, we terminated Study 211 prior to its completion.

Based on discussions with leading viral hepatitis experts, global regulatory discussions and feedback, and, with respect to the China territory, discussions and agreement with our collaboration partner, BeiGene, Ltd. (BeiGene), we

recently decided to not move forward with the global registrational studies for VBR as a chronic suppressive treatment (CST) with NrtI. The decision was made to focus on the greatest unmet medical need of patients, which lies predominantly in cure, rather than CST. As a result, we also expect to terminate Study 205, as we focus our efforts with VBR moving forward in combination with NrtI and additional mechanisms targeting finite and curative combination therapy.

ABI-H2158

Our second-generation core inhibitor product candidate, ABI-H2158 (2158), was internally discovered and developed and is chemically distinct from VBR.

We reported the final data from dose-ranging cohorts of the Phase 1b portion of the Phase 1a/1b dose-ranging clinical study at EASL in August 2020. Based on data from the Phase 1b dose-ranging study, we initiated a Phase 2 clinical study in June 2020 using a 300 mg daily dose of 2158. This study is being conducted in approximately ten countries in Asia, North America and Europe. We expect interim data from this study in the second half of 2021. While we will continue to monitor the situation closely, at this time, we do not expect our timelines for this study to be significantly impacted by the COVID-19 pandemic.

ABI-H3733

Our third core inhibitor product candidate, ABI-H3733 (3733), has completed Investigational New Drug (IND) enabling studies. 3733 has a novel chemical scaffold separate from both VBR and 2158. We presented a preclinical profile of this candidate in the first quarter of 2019.

In the first quarter of 2020, we initiated a Phase 1a clinical study to evaluate safety, tolerability and pharmacokinetics (PK) following single ascending dose and multiple ascending dose administration of 3733 in healthy subjects in New Zealand. Conduct for the study was completed in the fourth quarter of 2020 and preliminary data indicate that 3733 was generally well-tolerated and had favorable PK.

Additional Product Candidates

In addition to our three clinical-stage product candidates, our research discovery team is actively focused on identifying and selecting a fourth-generation core inhibitor candidate, which we anticipate in the first half of 2021.

Multi-Drug Combination Studies

We believe that core inhibitors and NrtI will be central to finite and curative therapies for chronic HBV infection. Therefore, as we continue to develop and advance our current and future core inhibitors through clinical studies, we plan to conduct multi-drug combination studies in parallel that add additional drugs (or compounds) with non-overlapping mechanisms of action to the core inhibitor + NrtI antiviral backbone. Specifically, we plan on only incorporating our current and future core inhibitors that have demonstrated they are well-tolerated and effective in clinical studies in dual combination with NrtI. As the 300 mg daily dose of VBR has been observed to be well-tolerated in all studies conducted to date, with no serious adverse effects or dose-limiting toxicities identified and no pattern of treatment-emergent clinical or laboratory abnormalities observed and has progressed beyond dual combination studies, we currently have two triple combination studies planned to study VBR in combination with NrtI and a third mechanism of action.

Beyond Core Inhibitors

In addition to the development and advancement of our core inhibitor portfolio and our current and future multi-drug combination studies, our research and development team is working on discovering and developing a potent fourth-generation core inhibitor, cccDNA disruptors and small molecules targeting novel undisclosed targets to add to the core inhibitor + NrtI antiviral backbone to achieve cure.

Operations

We currently have corporate and administrative offices and research laboratory space in South San Francisco, California, Groton, Connecticut and a small office in China.

Since our inception, we have had no revenue from product sales and have funded our operations principally through debt financings prior to our initial public offering in 2010 and through equity financings and collaborations since then. Our operations to date have been primarily limited to organizing and staffing our company, licensing our product candidates, discovering and developing our product candidates, maintaining and improving our patent portfolio and

raising capital. We have generated significant losses to date, and we expect to continue to generate losses as we continue to develop our product candidates. As of December 31, 2020, we had an accumulated deficit of $501.6 million. Because we do not generate revenue from any of our product candidates, our losses will continue as we further develop and seek regulatory approval for, and commercialize, our product candidates. As a result, our operating losses are likely to be substantial over the next several years as we continue the development of our product candidates and thereafter if none are approved or successfully launched. We are unable to predict the extent of any future losses or when we will become profitable, if at all.

Financial Operations Overview

Research and Development Expense

Research and development expenses consist primarily of costs incurred for our research activities, including our drug discovery efforts, target validation, lead optimization and the development of our product candidates, which include:

• fees related to our license agreements; and

Research and development costs are expensed as incurred. Nonrefundable advance payments for goods or services to be received in the future for use in research and development activities are deferred and capitalized. The capitalized amounts are expensed as the related goods are delivered or the services are rendered.

We use our employee and infrastructure resources across multiple research and development programs, and we allocate internal employee-related and infrastructure costs, as well as certain third-party costs, to each of our programs based on the personnel resources allocated to such program. Our research and development expenses, by major program, are outlined in the table below (in thousands):

Year Ended December 31,

The successful discovery and development of our product candidates is highly uncertain. As such, at this time, we cannot reasonably estimate, or know the nature, timing and estimated costs, of the efforts that will be necessary to complete the remainder of their development. We are also unable to predict when, if ever, material net cash inflows will commence from our product candidates. This is due to the numerous risks and uncertainties associated with developing medicines, including the uncertainty of:

• successful enrollment in, and completion of, clinical studies;

• making arrangements with third-party manufacturers; and

A change in the outcome of any of these variables or variables discussed in “Item 1A. Risk Factors” with respect to the development of any of our product candidates would significantly change the costs and timing associated with the development of that product candidate.

Research and development activities are central to our business model. Product candidates in later stages of clinical development generally have higher development costs than those in earlier stages of clinical development, primarily due to the increased size and duration of later-stage clinical studies. However, we do not believe that it is possible at this time to accurately project total program-specific expenses through commercialization. There are numerous factors associated with the successful commercialization of any of our product candidates, including future trial design and various regulatory requirements, many of which cannot be determined with accuracy at this time based on our stage of development. Additionally, future commercial and regulatory factors beyond our control will impact our clinical development programs and plans.

General and administrative expenses

General and administrative expenses consist primarily of salaries and other related costs, including stock-based compensation, for personnel in executive, finance, accounting, business development, legal and human resources functions. Other significant costs include facility costs not otherwise included in research and development expenses, insurance costs, legal fees relating to patents and corporate matters and fees for accounting and consulting services.

We anticipate that our general and administrative expenses will increase in the future to support continued research and development activities, potential commercialization of our product candidates and costs of operating as a public company. These increases will likely include increased costs related to the hiring of additional personnel and fees to outside consultants, lawyers and accountants, among other expenses. Additionally, we anticipate increased costs associated with being a public company, including expenses related to services associated with maintaining compliance with exchange listing and U.S. Securities and Exchange Commission (SEC) requirements, insurance, and investor relations costs.

Interest income

Interest income consists of interest earned on our cash and cash equivalents and available-for-sale securities.

Critical Accounting Policies and Significant Judgments and Estimates

Our management’s discussion and analysis of our financial condition and results of operations is based on our consolidated financial statements, which we have prepared in accordance with accounting principles generally accepted in the United States. The preparation of these consolidated financial statements requires us to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the financial statements, as well as the reported amounts of revenues and expenses during the reporting periods. We evaluate our estimates and judgments, including those described in greater detail below, on an ongoing basis. We base our estimates on historical experience and on various other factors that we believe are

reasonable under the circumstances, the results of which form the basis for making judgments about the carrying value of assets and liabilities that are not readily apparent from other sources. Actual results may differ from these estimates under different assumptions or conditions.

While our significant accounting policies are described in more detail in the notes to our consolidated financial statements included elsewhere in this Annual Report on Form 10-K, we believe that the following accounting policies are the most critical to aid you in fully understanding and evaluating our financial condition and results of operations.

Revenue Recognition and Accounts Receivable from Collaboration

We analyze our collaboration arrangements to assess whether such arrangements, or transactions between arrangement participants, involve joint operating activities performed by parties that are both active participants in the activities and exposed to significant risks and rewards dependent on the commercial success of such activities or are more akin to a vendor-customer relationship. In making this evaluation, we consider whether the activities of the collaboration are considered to be distinct and deemed to be within the scope of the collaborative arrangement accounting standard and those that are more reflective of a vendor-customer relationship and, therefore, within the scope of the revenue with contracts with customers accounting standard. This assessment is performed throughout the life of the arrangement based on changes in the responsibilities of all parties in the arrangement.

For elements of collaboration arrangements that are not accounted for pursuant to the revenue from contracts with customers accounting standard, an appropriate recognition method is determined and applied consistently, generally by analogy to the revenue from contracts with customers accounting standard. Amounts related to transactions with a counterparty in a collaborative arrangement that is not a customer are presented as collaboration revenue and on a separate line item from revenue recognized from contracts with customers, if any, in our consolidated statements of operations and comprehensive loss.

Under certain collaborative arrangements, we are reimbursed for a portion of our research and development expenses or participate in the cost-sharing of such research and development expenses. Such reimbursements and cost-sharing arrangements are reflected as a reduction of research and development expense our consolidated statements of operations and comprehensive loss, as we do not consider performing these activities for reimbursement to be a part of our ongoing major or central operations.

For arrangements or transactions between arrangement participants determined to be within the scope of the contracts with customers accounting standard, we evaluate the term of the arrangement and recognize revenue when the customer obtains control of promised goods or services in a contract for an amount that reflects the consideration we expect to receive in exchange for those goods or services. For contracts with customers, we apply the following five-step model in order to determine this amount: (1) identification of the promised goods or services in the contract; (2) determination of whether the promised goods or services are performance obligations, including whether they are distinct in the context of the contract; (3) measurement of the transaction price, including the constraint on variable consideration; (4) allocation of the transaction price to the performance obligations; and (5) recognition of revenue when (or as) we satisfy each performance obligation.

We have provided standard indemnification and protection of licensed intellectual property for our customers. These provisions are part of assurance that the licenses meet the agreements, representations and are not obligations to provide goods or services.

We only apply the five-step model to contracts when it is probable we will collect the consideration we are entitled to in exchange for the goods or services it transfers to the customer. As part of the accounting for contracts with customers, we must develop assumptions that require judgment to determine the standalone selling price of each performance obligation identified in the contract. We then allocate the total transaction price to each performance obligation based on the estimated standalone selling prices of each performance obligation. We recognize the amount of the transaction price that is allocated to the respective performance obligation when the performance obligation is satisfied or as it is satisfied as revenue.

Upfront License Fees

If a license to our intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, we recognize revenues from nonrefundable, upfront license fees based on the relative value prescribed to the license compared to the total value of the arrangement. The revenue is recognized when the license is transferred to the collaborator and the collaborator is able to use and benefit from the license. For licenses that are not distinct from other obligations identified in the arrangement, we utilize judgment to assess the nature of the combined

performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time. If the combined performance obligation is satisfied over time, we apply an appropriate method of measuring progress for purposes of recognizing revenue from nonrefundable, upfront license fees. We evaluate the measure of progress each reporting period and, if necessary, adjust the measure of performance and related revenue recognition.

Research and Development Service Payments

Under the Allergan Agreement, we were reimbursed at a certain percentage for performing research and development services based on hours worked by our employees at a fixed contractual rate per hour and third-party pass-through costs we incurred on a quarterly basis. Research and development service payments were included in the transaction price in the reporting period we concluded it was probable that recording revenue in the period would not result in a significant reversal in amounts recognized in future periods. Accounts receivable were recorded when the right to the research and development service payment consideration became unconditional. We recorded the full reimbursed portion of these expenses accounted for under the contract with customer accounting standard as collaboration revenue in our consolidated statements of operations as we consider performing research and development services to be a part of our ongoing and central operations.

Development and Regulatory Milestone Payments

Depending on facts and circumstances, we may record revenues from certain milestones in a reporting period before the milestone is achieved if we conclude that achievement of the milestone is probable and that recognition of revenue related to the milestone will not result in a significant reversal in amounts recognized in future periods. We record a corresponding contract asset when this conclusion is reached. Milestone payments that have not been included in the transaction price to date are fully constrained. We re-evaluate the probability of achievement of such milestones and any related constraint each reporting period. We adjust our estimate of the overall transaction price, including the amount of collaborative revenue that was recorded, if necessary.

Sales-based Milestone and Royalty Payments

Our customer may be required to pay us sales-based milestone payments or royalties on future sales of commercial products. We recognize revenues related to sales-based milestone and royalty payments upon the later to occur of (1) achievement of the collaborator’s underlying sales or (2) satisfaction of any performance obligation(s) related to these sales, in each case assuming our licensed intellectual property is deemed to be the predominant item to which the sales-based milestones and/or royalties relate.

We receive payments from our customer based on billing schedules established in each contract. Upfront payments and fees are recorded as deferred revenue upon receipt or when due until we perform our obligations under the arrangement. If the related performance obligation is expected to be satisfied within the next 12 months, these amounts will be classified in current liabilities. We recognize a contract asset relating to our conditional right to consideration that is not subject to a constraint. Amounts are recorded as accounts receivable when our right to consideration is unconditional.

A net contract asset or liability is presented for each contract with a customer. We do not assess whether a contract has a significant financing component if the expectation at contract inception is such that the period between payment by the customer and the transfer of the promised goods or services to the customer will be one year or less.

We may be required to exercise considerable judgment in estimating revenue to be recognized. Judgment is required in identifying performance obligations, estimating the transaction price, estimating the standalone selling prices of identified performance obligations, which may include forecasted revenue, development timelines, reimbursement rates for personnel and other research and development costs, discount rates and probabilities of technical and regulatory success, and estimating the progress towards satisfaction of performance obligations.

On January 1, 2018, we adopted ASU No. 2014-09, Revenue from Contracts with Customers, as amended (Accounting Standards Codification Topic 606) (ASC 606) using the modified retrospective method applied to those contracts which were not completed as of January 1, 2018. We also elected to use the practical expedient that allows an entity to expense the incremental cost of obtaining a contract as an expense when incurred if the amortization period of the asset that an entity otherwise would have recognized is less than one year. Results for the year ended December 31, 2018 are presented under ASC 606, while prior period amounts are not adjusted and continue to be reported in

accordance with historic accounting under the previous revenue recognition accounting standard. As of the adoption date of ASC 606, we had only one contract with a customer, Allergan, that had not been completed. Based on our analysis, we concluded there was no significant change in applying ASC 606 to our agreement with Allergan and no amounts have been recognized within “accumulated deficit” in the consolidated balance sheet related to the adoption of the new standard.

Goodwill and Indefinite-Lived Intangible Assets

Goodwill and indefinite-lived intangible assets are reviewed for impairment at least annually in the fourth quarter and more frequently if events or other changes in circumstances indicate that the carrying amount of the assets may not be recoverable. Impairment of goodwill and indefinite-lived intangibles is determined to exist when the fair value is less than the carrying value of the net assets being tested.

Goodwill

We determined that we have only one operating segment and reporting unit. Accordingly, our review of goodwill impairment indicators is performed at the entity-wide level. In performing each annual impairment assessment and any interim impairment assessment, we determine if we should qualitatively assess whether it is more likely than not that the fair value of goodwill is less than its carrying amount (the qualitative impairment test). Some of the factors considered in the assessment include general macroeconomic conditions, conditions specific to the industry and market, cost factors, the overall financial performance and whether there have been sustained declines in our share price. If we conclude it is more likely than not that the fair value of the reporting unit is less than its carrying amount, or elect not to use the qualitative impairment test, a quantitative impairment test is performed. Effective January 1, 2020, we early adopted ASU 2017-04, Intangibles-Goodwill and Other (Topic 350):Simplifying the Test for Goodwill Impairment (ASU 2017-04), which simplifies how an entity is required to test goodwill for impairment by eliminating Step 2 from the goodwill impairment test. Under this accounting standard, annual or interim quantitative impairment testing is performed by comparing the estimated fair value of the reporting unit to its carrying value. An impairment charge is recognized for the amount by which the carrying amount exceeds the reporting unit’s fair value, not to exceed the carrying value of goodwill. We use our market capitalization as an indicator of fair value. We believe that since our reporting unit is publicly traded, the ability of a controlling stockholder to benefit from synergies and other intangible assets that arise from control might cause the fair value of our reporting unit as a whole to exceed our market capitalization. However, we believe that the fair value measurement need not be based solely on the quoted market price of an individual share of our common stock, but also can consider the impact of a control premium in measuring the fair value of its reporting unit. The control premium utilized is based on control premiums observed in recent acquisitions of entities similar to us that were made on a non-minority basis. Should our market capitalization be less than our total stockholders’ equity as of our annual test date or as of any interim impairment testing date, we would also consider market comparables, recent trends in our stock price over a reasonable period and, if appropriate, use an income approach (discounted cash flow) to determine whether the fair value of our reporting unit is greater than our carrying amount. If we were to use an income approach, we would establish a fair value by estimating the present value of our projected future cash flows expected to be generated from our business. The discount rate applied to the projected future cash flows to arrive at the present value would be intended to reflect all risks of ownership and the associated risks of realizing the stream of projected future cash flows. Our discounted cash flow methodology would consider projections of financial performance for a period of several years combined with an estimated residual value. The most significant assumptions we would use in a discounted cash flow methodology are the discount rate, the residual value and expected future revenues, gross margins and operating costs, along with considering any implied control premium. In 2020, we elected to bypass the qualitative goodwill impairment assessment. As of October 1, 2020, we have determined through a quantitative impairment test that the fair value significantly exceeded the carrying value of our single reporting unit, and concluded that goodwill was not impaired. In November 2020, after our public announcement that it became clear that patients who stopped therapy in Study 211 had not achieved meaningful SVR rates as 39 of 41 patients relapsed, our stock price declined 152% closing on November 5 at $15.90 and opening on November 6 at $6.30. Due to a sustained decline in our stock price during the remainder of the fourth quarter of 2020, we determined these factors were an indication of a triggering event of impairment and an interim goodwill impairment test was performed as of December 31, 2020. However, our interim quantitative impairment test still determined the fair value exceeded the carrying value of our single reporting unit and concluded that goodwill was still not impaired. We did not recognize any goodwill impairment in any of the years presented.

Indefinite-Lived Intangible Asset

Our indefinite-lived intangible asset consists of in-process research and development (IPR&D) projects acquired in a business combination that are used in research and development activities but have not yet reached technological feasibility, regardless of whether they have alternative future use. The primary basis for determining the technological

feasibility or completion of these projects is obtaining regulatory approval to market the underlying products in an applicable geographic region. We classify in-process research and development acquired in a business combination as an indefinite-lived intangible asset until the completion or abandonment of the associated research and development efforts. Upon completion of the associated research and development efforts, we perform a final test for impairment and will determine the useful life of the technology and begin amortizing the assets to reflect their use over their remaining lives. Upon permanent abandonment, we would write off the remaining carrying amount of the associated IPR&D intangible asset.

In performing each annual impairment assessment and any interim impairment assessment, we determine if we should qualitatively assess whether it is more likely than not that the fair value of our IPR&D asset is less than its carrying amount (the qualitative impairment test). If we conclude that is the case, or elect not to use qualitative impairment test, we would proceed with quantitatively determining the fair value of the IPR&D asset and comparing its fair value to its carrying value to determine the amount of impairment, if any (the quantitative impairment test).

In performing the qualitative impairment test, we consider the results of the most recent quantitative impairment test and identify the most relevant drivers of the fair value for the IPR&D asset. The most relevant drivers of fair value we have identified are consistent with the assumptions used in the quantitative estimate of the IPR&D asset discussed below. Using these drivers, we identify events and circumstances that may have an effect on the fair value of the IPR&D asset since the last time the IPR&D’s fair value was quantitatively determined. We then weigh these factors to determine and conclude if it is not more likely than not that the IPR&D asset is impaired. If it is more likely than not that the IPR&D asset is impaired we proceed with quantitatively determining the fair value of the IPR&D asset.

We use the income approach to determine the fair value of our IPR&D asset. This approach calculates fair value by estimating the after-tax cash flows attributable to an in-process project over its useful life and then discounting these after-tax cash flows back to a present value. This estimate includes significant assumptions regarding the estimates that market participants would make in evaluating the IPR&D asset, including the probability of successfully completing clinical trials and obtaining regulatory approval to market the IPR&D asset, the timing of and the expected costs to complete IPR&D projects, future net cash flows from potential drug sales, which are based on estimates of the sales price of the drug, the number of patients who will be diagnosed and treated and our competitive position in the marketplace, and appropriate discount and tax rates. Any impairment to be recorded is calculated as the difference between the fair value of the IPR&D asset as of the date of the assessment with the carrying value of the IPR&D asset on our consolidated balance sheet.

For our 2020 impairment test, we performed a qualitative test and concluded it was more-likely-than-not that the fair value of our IPR&D asset exceeded its carrying value and no further testing was required. This was based on a decrease in the probability of success based on the impact of the Study 211 and dual combination VBR and NrtI therapy’s ability to serve as a finite and curative therapy for chronic HBV infection offset by an increase in the probability of success of 2158 and 3733 based on their advancement into Phase 2 and Phase 1 trials during 2020, respectively and the significance of the future net cash flows from potential drug sales for a finite and curative therapy for chronic HBV infection as primarily driven by the number of patients who will be diagnosed and treated and our competitive position in the marketplace. We did not recognize any IPR&D impairment in any of the years presented.

For asset purchases outside of business combinations, we expense any purchased research and development assets as of the acquisition date if they have no alternative future uses.

Research and Development Expense and Accruals

Research and development costs include personnel-related costs, outside contracted services including clinical study costs, facilities costs, fees paid to consultants, milestone payments prior to FDA approval, license fees prior to FDA approval, professional services, travel costs, dues and subscriptions, depreciation and materials used in clinical trials as well as research and development and costs incurred under our collaboration agreements. Research and development costs are expensed as incurred unless there is an alternative future use in other research and development projects. Payments made prior to the receipt of goods or services to be used in research and development are capitalized until the goods or services are received. Such payments are evaluated for current or long-term classification based on when they will be realized or consumed. Assets acquired as part of an asset acquisition that are used in research and development or are IPR&D are immediately expensed as research and development unless there is an alternative future use in other research and development projects.

As part of the process of preparing our consolidated financial statements, we are required to estimate certain research and development expenses. This process involves reviewing quotations and contracts, reviewing the terms of our license agreements, communicating with our vendors and applicable personnel to identify services that have been performed on our behalf and estimating the level of service performed and the associated cost incurred for the service

when we have not yet been invoiced or otherwise notified of the actual cost. The majority of our service providers invoice us monthly in arrears for services performed or when contractual milestones are met. Payments made prior to the receipt of goods or services to be used in research and development are capitalized until the goods or services are received. Such payments are evaluated for current or long-term classification based on when they will be realized or consumed. Examples of estimated amortized or accrued research and development expenses include fees to:

• CROs and other service providers in connection with clinical studies;

• CMOs in connection with the production of clinical trial materials; and

• vendors in connection with preclinical development activities.

We base our expenses related to clinical studies on our estimates of the services received and efforts expended pursuant to contracts with multiple research institutions and contract research organizations that conduct and manage clinical studies on our behalf. The financial terms of these agreements are subject to negotiation, vary from contract to contract and may result in uneven payment flows and expense recognition. Payments under some of these contracts depend on factors such as the successful enrollment of patients and the completion of clinical trial milestones. In either amortizing or accruing service fees, we estimate the time period over which services will be performed and the level of effort to be expended in each period. If the actual timing of the performance of services or the level of effort varies from our estimate, we adjust the related prepayment or accrual accordingly. Our understanding of the status and timing of services performed relative to the actual status and timing of services performed may vary and may result in our reporting changes in estimates in any particular period. Adjustments to prior period estimates have not been material for the years ended December 31, 2020 and 2019.

We have and may continue to enter into license agreements to access and utilize certain technology. In each case, we evaluate if the license agreement results in the acquisition of an asset or a business. To date, none of our license agreements have been considered to be acquisitions of businesses. For asset acquisitions, the upfront payments to acquire such licenses, as well as any future milestone payments, are immediately recognized as research and development expense when paid, provided there is no alternative future use of the rights in other research and development projects. These license agreements may also include contingent consideration in the form of cash payments to be made for future milestone events. We assess whether such contingent consideration meets the definition of a derivative and to date we have determined that such contingent consideration are not derivatives.

Restructuring Charges

We recognize restructuring charges related to reorganization plans that have been committed to by us and when liabilities have been incurred. In connection with these activities, we record restructuring charges at fair value for (1) contractual employee termination benefits when obligations are associated to services already rendered, rights to such benefits have vested, and payment of benefits is probable and can be reasonably estimated, (2) one-time employee termination benefits when we have committed to a plan of termination, the plan identifies the employees and their expected termination dates, the details of termination benefits are complete, it is unlikely changes to the plan will be made or the plan will be withdrawn and communication to such employees has occurred, and (3) contract termination costs when a contract is terminated before the end of its term.

One-time employee termination benefits are recognized in their entirety when communication has occurred and future services are not required. If future services are required, the costs are recorded ratably over the remaining period of service. Contract termination costs to be incurred over the remaining contract term without economic benefit are recorded in their entirety when the contract is canceled.

The recognition of restructuring charges requires us to make certain judgments and estimates regarding the nature, timing and amount of costs associated with the planned reorganization plan. To the extent the actual results differ from its estimates and assumptions, we may be required to revise the estimates of future accrued restructuring liabilities, requiring the recognition of additional restructuring charges or the reduction of accrued restructuring liabilities previously recognized. Such changes to previously estimated amounts may be material to our consolidated financial statements. Changes in the estimates of the restructuring charges are recorded in the period in which the change is determined.

At the end of each reporting period, we evaluate the remaining accrued restructuring balances to ensure that no excess accruals are retained and the utilization of the provisions are for their intended purpose in accordance with developed restructuring plans.

Off-Balance Sheet Arrangements

Since our inception, we have not engaged in any off-balance sheet arrangements.

Contractual Obligations

We have contractual and commercial obligations under our operating lease commitments and licenses. The following table summarizes our future contractual obligations and commercial commitments at December 31, 2020 (in thousands):

Payments Due By Period

Less than 1 year 1-3 years 3-5 years More than 5 years Total

In general, milestone, royalty and other contingent fees associated with certain collaboration and license agreements have not been included in the above table of contractual obligations, because we cannot reasonably estimate if or when they will occur. The milestone payments included in the table of contractual obligations above are payments we believe are reasonably likely to occur during the indicated time periods. We enter into contracts in the normal course of business with CROs for clinical trials and CMO’s for clinical supply manufacturing and with vendors for preclinical research studies and other services and products for operating purposes, which generally provide for termination within 30 days of notice, and therefore, are cancelable contracts and not included in the table above. Further, we anticipate that our operating lease obligations will be higher than projected as we renew existing real estate leases that expire in 2020 and enter into new or expanded real estate leases.

Results of Operations

General

At December 31, 2020, we had an accumulated deficit of $501.6 million primarily as a result of research and development expenses and general and administrative expenses. While we may in the future generate revenue from a variety of sources, including license fees, milestone payments, research and development payments in connection with strategic partnerships and/or product sales, our product candidates are in the clinical stage of development and may never be successfully developed or commercialized. Accordingly, we expect to continue to incur substantial losses from operations for the foreseeable future and there can be no assurance that we will ever generate significant revenues.

Comparison of the Years Ended December 31, 2020 and 2019

Collaboration Revenue

The following table summarizes the period-over-period changes in our collaboration revenue (in thousands, except for percentages):