Assembly Biosciences (ASMB) 10-K 11 Mar 22 2021 FY Annual report Financial data

Document And Entity Information

Document And Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Feb. 28, 2022	Jun. 30, 2021
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Transition Report	false
Document Period End Date	Dec. 31, 2021
Entity File Number	001-35005
Entity Registrant Name	ASSEMBLY BIOSCIENCES, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	20-8729264
Entity Address, Address Line One	331 Oyster Point Blvd.
Entity Address, Address Line Two	Fourth Floor
Entity Address, City or Town	South San Francisco
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94080
City Area Code	833
Local Phone Number	509-4583
Amendment Flag	false
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Entity Central Index Key	0001426800
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Trading Symbol	ASMB
Security Exchange Name	NASDAQ
Title of 12(b) Security	Common Stock, $0.001 Par Value
Entity Common Stock, Shares Outstanding		48,120,437
ICFR Auditor Attestation Flag	false
Entity Shell Company	false
Entity Emerging Growth Company	false
Entity Small Business	true
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Public Float			$ 168.3
Auditor Name	Ernst & Young LLP
Auditor Firm ID	42
Auditor Location	Redwood City, California
Documents Incorporated by Reference	Part III of this Annual Report on Form 10-K incorporates information by reference to portions of the definitive proxy statement for the Company’s Annual Meeting of Stockholders to be held in 2022, to be filed within 120 days of the registrant’s fiscal year ended December 31, 2021.

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Current assets
Cash and cash equivalents	$ 45,627	$ 59,444
Marketable securities - short-term	101,000	156,969
Accounts receivable from collaborations	336	1,230
Prepaid expenses and other current assets	7,241	6,850
Total current assets	154,204	224,493
Marketable securities - long-term	27,972
Property and equipment, net	1,139	1,600
Operating lease right-of-use (ROU) assets	6,042	9,131
Other assets	1,703	6,392
Indefinite-lived intangible asset		29,000
Goodwill		12,638
Total assets	191,060	283,254
Current liabilities
Accounts payable	2,659	4,598
Accrued research and development expenses	3,400	4,444
Other accrued expenses	6,863	11,987
Operating lease liabilities - short-term	3,151	3,404
Total current liabilities	16,073	24,433
Deferred tax liabilities		2,531
Deferred revenue	2,733	8,987
Operating lease liabilities - long-term	3,325	6,725
Total liabilities	22,131	42,676
Commitments and contingencies
Stockholders' equity
Preferred stock, $0.001 par value; 5,000,000 shares authorized; no shares issued or outstanding
Common stock, $0.001 par value; 100,000,000 shares authorized as of December 31, 2021 and December 31, 2020; 48,120,437 and 34,026,680 shares issued and outstanding as of December 31, 2021 and December 31, 2020, respectively	48	34
Additional paid-in capital	800,728	742,387
Accumulated other comprehensive loss	(419)	(270)
Accumulated deficit	(631,428)	(501,573)
Total stockholders' equity	168,929	240,578
Total liabilities and stockholders' equity	$ 191,060	$ 283,254

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2021	Dec. 31, 2020
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	48,120,437	34,026,680
Common stock, shares outstanding	48,120,437	34,026,680

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Income Statement [Abstract]
Collaboration revenue	$ 6,254	$ 79,105
Operating expenses
Research and development	68,524	106,823
General and administrative	28,780	37,058
Impairment of goodwill and indefinite-lived intangible asset	41,638	0
Total operating expenses	138,942	143,881
Loss from operations	(132,688)	(64,776)
Other income
Interest and other income, net	302	2,624
Total other income	302	2,624
Loss before income taxes	(132,386)	(62,152)
Income tax benefit	2,531	0
Net loss	(129,855)	(62,152)
Other comprehensive loss
Unrealized loss on marketable securities	(149)	(69)
Comprehensive loss	$ (130,004)	$ (62,221)
Net loss per share, basic and diluted	$ (3)	$ (1.75)
Weighted average common shares outstanding, basic and diluted	43,280,383	35,427,120

CONSOLIDATED STATEMENTS OF CHAN

CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit
Balance at Dec. 31, 2019	$ 273,217	$ 32	$ 712,807	$ (201)	$ (439,421)
Balance (in shares) at Dec. 31, 2019		32,558,307
Issuance of common stock under ATM equity offering program, net of issuance costs	5,452	$ 1	5,451
Issuance of common stock under at-the-market (ATM) equity offering program, net of issuance costs (in shares)		892,840
Issuance of common stock upon exercise of stock options	1,467	$ 1	1,466
Issuance of common stock upon exercise of stock options ( in shares )		175,579
Issuance of common stock under Employee Stock Purchase Plan (ESPP)	680		680
Issuance of common stock under Employee Stock Purchase Plan (ESPP) (in shares)		86,812
Issuance of shares of common stock for settlement of restricted stock units (RSUs) (in shares)		313,142
Unrealized loss on marketable securities	(69)			(69)
Stock-based compensation	21,983		21,983
Net loss	(62,152)				(62,152)
Balance at Dec. 31, 2020	240,578	$ 34	742,387	(270)	(501,573)
Balance (in shares) at Dec. 31, 2020		34,026,680
Issuance of common stock under ATM equity offering program, net of issuance costs	52,806	$ 11	52,795
Issuance of common stock under at-the-market (ATM) equity offering program, net of issuance costs (in shares)		11,234,207
Issuance of common stock under Employee Stock Purchase Plan (ESPP)	258		258
Issuance of common stock under Employee Stock Purchase Plan (ESPP) (in shares)		88,820
Issuance of common stock for settlement of restricted stock units (RSUs)		$ 1	(1)
Issuance of shares of common stock for settlement of restricted stock units (RSUs) (in shares)		347,096
Issuance of common stock upon cashless exercise of pre-funded warrants		$ 2	(2)
Issuance of common stock upon cashless exercise of pre-funded warrants (in shares)		2,423,634
Unrealized loss on marketable securities	(149)			(149)
Stock-based compensation	5,291		5,291
Net loss	(129,855)				(129,855)
Balance at Dec. 31, 2021	$ 168,929	$ 48	$ 800,728	$ (419)	$ (631,428)
Balance (in shares) at Dec. 31, 2021		48,120,437

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Cash flows from operating activities
Net loss	$ (129,855)	$ (62,152)
Adjustments to reconcile net loss to net cash used in operating activities:
Impairment of goodwill and indefinite-lived intangible asset	41,638	0
Depreciation and amortization	466	691
Non-cash in-process research and development (IPR&D) expense	0	1,750
Stock-based compensation	5,237	21,853
Net accretion and amortization of investments in marketable debt securities	586	(13)
Non-cash rent expense	3,840	5,214
Deferred income tax benefit	(2,531)	0
Loss on disposal of property and equipment	1,624	9
Gain on the sale of Microbiome assets	(3,000)	0
Changes in operating assets and liabilities:
Accounts receivable from collaboration	894	2,144
Prepaid expenses and other current assets	1,109	(1,487)
Other assets	4,689	(4,708)
Accounts payable	(1,939)	2,867
Accrued research and development expenses	(1,044)	(382)
Other accrued expenses	(5,070)	3,831
Deferred revenue	(6,254)	(28,061)
Operating lease liabilities	(3,786)	(4,513)
Net cash used in operating activities	(93,396)	(62,957)
Cash flows from investing activities
Purchases of property and equipment	(3,096)	(470)
Proceeds from sale of property and equipment	857	0
Purchase of IPR&D from an acquisition of assets	0	(1,750)
Proceeds from the sale of Microbiome assets	1,500	0
Purchases of marketable securities	(160,446)	(193,188)
Proceeds from maturities of marketable securities	175,200	221,617
Proceeds from sale of marketable securities	12,500	41,861
Net cash provided by investing activities	26,515	68,070
Cash flows from financing activities
Proceeds from the issuance of common stock under ATM equity offering program, net of issuance costs	52,806	5,452
Proceeds from the issuance of common stock under ESPP	258	680
Proceeds from the exercise of stock options	0	1,467
Net cash provided by financing activities	53,064	7,599
Net increase (decrease) in cash and cash equivalents	(13,817)	12,712
Cash and cash equivalents at the beginning of the period	59,444	46,732
Cash and cash equivalents at the end of the period	45,627	59,444
Supplemental non-cash investing and financing activities
Operating lease liabilities arising from obtaining ROU assets	126	1,302
Remeasurement of lease liabilities arising from modification of ROU assets	(788)	0
Receivable from sale of Microbiome assets included in prepaid expenses and other current assets	$ (1,500)	$ 0

Nature of Business

Nature of Business	12 Months Ended
	Dec. 31, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Nature of Business	Note 1 - Nature of Business Overview Assembly Biosciences, Inc., together with its subsidiaries (Assembly or the Company), incorporated in Delaware in October 2005, is a clinical-stage biotechnology company focused on discovery and development of novel therapeutics for the treatment of hepatitis B virus (HBV) infection and other viral diseases. The Company operates in one segment and is headquartered in South San Francisco, California, with operations in California and China. Prior to the Company’s wind-down of its Microbiome program in January 2021, the Company also had operations in Connecticut. The Company’s research and development programs are pursuing multiple drug candidates that 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. The Company has discovered several novel core inhibitors, which are small molecules that directly target and allosterically modify the HBV core (HBc) protein in a way that affects assembly and stability of HBV nucleocapsids. Liquidity The Company has not derived any revenue from product sales to date and currently has no approved products. Once a product has been developed, it will need to be approved for sale by the U.S. Food and Drug Administration (FDA) or an applicable foreign regulatory agency. Since inception, the Company’s operations have been financed primarily through the sale of equity securities, the proceeds from the exercise of warrants and stock options, the issuance of debt, and upfront payments related to collaboration agreements. The Company has incurred losses from operations since inception and expects to continue to incur substantial losses for the next several years as it continues its product development efforts. Management believes the Company currently has sufficient funds to meet its operating requirements for at least the next twelve months following the date that these consolidated financial statements are issued. If the Company cannot generate significant cash from its operations, it intends to obtain any additional funding it requires through strategic relationships, public or private equity or debt financings, grants or other arrangements (see Note 8 for recent sales of common stock). The Company cannot assure such funding will be available on reasonable terms, if at all. Market volatility resulting from the novel coronavirus disease (COVID-19) pandemic or other factors could also adversely impact the Company’s ability to access capital when and as needed. If the Company is unable to generate enough revenue from its collaborations, secure additional sources of funding or receive full and timely collections of amounts due, it may be necessary to significantly reduce the current rate of spending through reductions in staff and delaying, scaling back, or stopping certain research and development programs, including more costly clinical trials.

Summary of Significant Accounti

Summary of Significant Accounting Policies and Recent Accounting Pronouncements	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Summary of Significant Accounting Policies and Recent Accounting Pronouncements	Note 2 - Summary of Significant Accounting Policies and Recent Accounting Pronouncements Basis of Presentation These consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (U.S. GAAP) and include the accounts of the Company and its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. Use of Estimates The preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that may affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and reported amounts of expenses during the reporting period. Actual results could differ from those estimates. Significant estimates inherent in the preparation of the accompanying consolidated financial statements include estimates of costs incurred but not yet invoiced for research and development accruals, the estimated fair value of our indefinite-lived intangible asset and the estimated fair value of our reporting unit for purposes of evaluating goodwill impairment. The Company’s estimates could be affected by external conditions, including those unique to the Company and general economic conditions. It is reasonably possible that these external factors could have an effect on the Company’s estimates and could cause actual results to differ from those estimates and assumptions. Other Risks and Uncertainties In March 2020, the World Health Organization declared the COVID-19 outbreak a pandemic. The ongoing COVID-19 pandemic and its broad, global impacts, including supply chain disruptions, have impacted certain aspects of the Company’s business, including where and how the Company’s employees work in its labs and offices and how and when the Company’s nonclinical and clinical studies are conducted. Early in the pandemic, the Company’s current and future planned clinical trials and preclinical studies were largely unaffected, but as the pandemic has continued, the Company has experienced enrollment delays for its current clinical studies, particularly its two ongoing multi-drug combination studies. However, the Company cannot at this time predict the specific extent, duration, or full impact the COVID-19 pandemic will have on its business, operations, strategy, prospects and financial condition and results. The impact of the COVID-19 pandemic on the Company’s financial performance will depend on future developments, including the duration and spread of the outbreak and related governmental advisories and restrictions. These developments and the impact of the COVID-19 pandemic on the financial markets and the overall economy are highly uncertain. If the financial markets and/or the overall economy are impacted for an extended period, the Company’s results may be adversely affected. In addition, the study design of an upcoming triple combination study initially included a site in Ukraine. The Company will no longer be conducting the study there due to the instability resulting from Russia’s recent invasion of Ukraine. These changes to the Company’s study plan will result in a delayed data readout. Cash and Cash Equivalents All highly liquid investments, including money market funds, with original maturities of three months or less at the time of purchase are considered to be cash equivalents. All of the Company’s cash equivalents have liquid markets and high credit ratings. The Company maintains its cash in bank deposits and other accounts, the balances of which, at times as of and during the years ended December 31, 2021 and 2020, exceed federally insured limits. Investments in Marketable Securities The Company invests its excess cash in debt securities with high credit ratings including but not limited to money market funds classified as cash equivalents, asset backed securities, securities issued by the U.S. government and its agencies, corporate debt securities and commercial paper. The Company has designated its investments in marketable securities as available-for-sale and measures these securities at their respective fair values. Marketable securities are classified as short-term or long-term based on the maturity date and their availability to meet current operating requirements. Marketable securities that mature in one year or less from the consolidated balance sheet date are classified as short-term available-for-sale securities, while marketable securities with maturities in one year or beyond one year from the consolidated balance sheet date are classified as long-term. Securities that are classified as available-for-sale are measured at fair value with temporary unrealized gains and losses reported in other comprehensive loss, and as a component of stockholders' equity until their disposition. The Company reviews all available-for-sale securities at each period end to determine if they remain available-for-sale based on their current intent and ability to sell the security if it is required to do so. Realized gains and losses from the sale of marketable securities, if any, are calculated using the specific-identification method. Marketable securities are subject to a periodic impairment review. The Company may recognize an impairment charge when a decline in the fair value of investments below the cost basis is determined to be other-than-temporary. In determining whether a decline in market value is other-than-temporary, various factors are considered, including the cause, duration of time and severity of the impairment, any adverse changes in the investees’ financial condition, and the Company’s intent and ability to hold the security for a period of time sufficient to allow for an anticipated recovery in market value. To date, there have been no declines in value deemed to be other than temporary for any of the Company’s investments in marketable securities . Goodwill and Indefinite-Lived Intangible Asset Goodwill and indefinite-lived intangible asset 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. Goodwill The difference between the purchase price and the fair value of assets acquired and liabilities assumed in a business combination is allocated to goodwill. Goodwill is evaluated for impairment on an annual basis as of October 1, and more frequently if indicators are present or changes in circumstances suggest impairment may exist. In performing each annual impairment assessment and any interim impairment assessment, the Company determines if it should qualitatively assess whether it is more likely than not the fair value of goodwill is less than its carrying amount (the qualitative impairment test). If the Company concludes it is more likely than not 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. The Company’s annual or interim quantitative impairment testing is performed by comparing the estimated Indefinite-Lived Intangible Asset The Company’s indefinite-lived intangible asset consists of IPR&D associated with small molecule core inhibitors that directly target and allosterically inhibit core protein functions associated with HBV which were acquired with the acquisition of Assembly Pharmaceutics, Inc. in 2014. IPR&D represents the fair value assigned to incomplete research projects the Company acquired through a business combination which, at the time of acquisition, had not reached technological feasibility, regardless of whether they had 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. The Company classifies IPR&D 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, the Company performed 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, the Company would write-off the remaining carrying amount of the associated IPR&D intangible asset. Indefinite-lived intangible assets are not amortized, but instead are reviewed for impairment at least annually, or more frequently if events occur or circumstances change that would indicate the carrying amount may be impaired. In performing each annual impairment assessment and any interim impairment assessment, the Company determines if it should qualitatively assess whether it is more likely than not the fair value of its IPR&D asset is less than its carrying amount (the qualitative impairment test). If the Company concludes that is the case, or elects not to use the qualitative impairment test, the Company 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, the Company considers the results of the most recent quantitative impairment test and identifies the most relevant drivers of the fair value for the IPR&D asset. The most relevant drivers of fair value identified are consistent with the assumptions used in the quantitative estimate of the IPR&D asset. Using these drivers of fair value, the Company identifies events and circumstances which 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. The Company then weighs these factors to determine and conclude if it is not more likely than not the IPR&D asset is impaired. If it is more likely than not the IPR&D asset is impaired, the Company proceeds with quantitatively determining the fair value of the IPR&D asset. When performing the quantitative impairment test, the Company uses the income approach to determine the fair value of its 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 judgmental 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 size of the patient population and cure rate, our competitive position in the marketplace, and appropriate discount and tax rates. Any impairment to be recorded is calculated as the difference between the estimated fair value and the carrying value of the IPR&D asset on the Company’s consolidated balance sheet. Leases All of the Company’s leases are operating leases for facilities and equipment. The Company recognizes a lease asset for its right to use the underlying asset and a lease liability for the corresponding lease obligation. The Company determines whether an arrangement is or contains a lease at contract inception. Operating leases with a duration greater than one year are included in operating lease right-of-use assets, operating lease liabilities - short-term, and operating lease liabilities - long-term in the Company’s consolidated balance sheets. Operating lease right-of-use assets and liabilities are recognized at the lease commencement date based on the present value of lease payments over the lease term. In determining the net present value of lease payments, the Company uses its incremental borrowing rate based on the information available at the lease commencement date. The incremental borrowing rate represents the interest rate the Company would incur at lease commencement to borrow an amount equal to the lease payments on a collateralized basis over the term of a lease. The Company considers a lease term to be the noncancelable period that it has the right to use the underlying asset, including any periods where it is reasonably assured the Company will exercise the option to extend the contract. Periods covered by an option to extend are included in the lease term if the lessor controls the exercise of that option. The operating lease right-of-use assets also include any lease payments made and exclude lease incentives. Lease expense is recognized on a straight-line basis over the expected lease term. Variable lease expenses are recorded when incurred. The Company has elected not to separate lease and non-lease components for its leased assets and accounts for all lease and non-lease components of its agreements as a single lease component. Impairment of Long-Lived Assets The Company monitors the carrying value of long-lived assets, including ROU operating lease assets, for potential impairment and tests the recoverability of such assets whenever events or changes in circumstances indicate that the carrying amounts may not be recoverable. If a change in circumstance occurs, the Company performs a test of recoverability by comparing the carrying value of the asset or asset group to its undiscounted expected future cash flows. If cash flows cannot be separately and independently identified for a single asset, the Company will determine whether impairment has occurred for the group of assets for which the Company can identify the projected cash flows. If the carrying values are in excess of undiscounted expected future cash flows, the Company measures any impairment by comparing the fair value of the asset or asset group to its carrying value. In conjunction with the decision to wind down the Microbiome program in December 2020, the Company evaluated its ROU assets and property and equipment used in the Microbiome program for impairment. The Company determined the carrying value was no longer recoverable and, based on the fair value of the assets determined from market quotes, recorded an impairment loss of $0.7 million included in research and development expenses in 2020. There were no indicators of impairment of long-lived assets during the year ended Property and Equipment, Net Property and equipment are stated at cost and consist of lab and office equipment, leasehold improvements and computer hardware and software. The Company records depreciation under the straight-line method over the estimated useful lives of its property and equipment ranging from three to seven years. Leasehold improvements are amortized over the remaining terms of the respective leases or the estimated useful life of the leasehold improvements, whichever is less. Maintenance and repair costs are expensed as incurred. Fair Value Measurements The Company follows accounting guidance on fair value measurements for financial instruments measured on a recurring basis, as well as for certain assets and liabilities that are initially recorded at their estimated fair values. Fair value is defined as the exit price, or the amount that would be received from selling an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. The Company uses the following three-level hierarchy that maximizes the use of observable inputs and minimizes the use of unobservable inputs to value its financial instruments: Level 1: Observable inputs such as unadjusted quoted prices in active markets for identical instruments. Level 2: Quoted prices for similar instruments that are directly or indirectly observable in the marketplace. Level 3: Significant unobservable inputs which are supported by little or no market activity and that are financial instruments whose values are determined using pricing models, discounted cash flow methodologies, or similar techniques, as well as instruments for which the determination of fair value requires significant judgment or estimation. Financial instruments measured at fair value are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. The assessment of the significance of a particular input to the fair value measurement in its entirety requires the Company to make judgments and consider factors specific to the asset or liability. The use of different assumptions and/or estimation methodologies may have a material effect on estimated fair values. Accordingly, the fair value estimates disclosed or initial amounts recorded may not be indicative of the amount the Company or holders of the instruments could realize in a current market exchange. The carrying amounts of cash equivalents and marketable securities approximate their fair value based upon quoted market prices. Certain of the Company’s financial instruments are not measured at fair value on a recurring basis but are recorded at amounts which approximate their fair value due to their liquid or short-term nature, such as cash, accounts receivable, accounts payable and accrued expenses. The following tables present the fair value of the Company’s financial assets measured at fair value on a recurring basis using the above input categories (in thousands): December 31, 2021 Level 1 Level 2 Level 3 Fair Value Cash equivalents Money market fund $ 42,507 $ — $ — $ 42,507 Total cash equivalents 42,507 — — 42,507 Short-term marketable securities U.S. and foreign corporate debt securities — 7,013 — 7,013 Asset-backed securities — 29,059 — 29,059 U.S. and foreign commercial paper — 64,928 — 64,928 Total short-term marketable securities — 101,000 — 101,000 Long-term marketable securities U.S. and foreign corporate debt securities — 19,043 — 19,043 U.S. treasury securities — 8,929 — 8,929 Total long-term marketable securities — 27,972 — 27,972 Total assets measured at fair value $ 42,507 $ 128,972 $ — $ 171,479 December 31, 2020 Level 1 Level 2 Level 3 Fair Value Cash equivalents Money market fund $ 47,553 $ — $ — $ 47,553 U.S. and foreign commercial paper — 6,498 — 6,498 Total cash equivalents 47,553 6,498 — 54,051 Short-term marketable securities U.S. and foreign corporate debt securities — 16,939 — 16,939 Asset-backed securities — 12,675 — 12,675 U.S. treasury securities — 23,999 — 23,999 U.S. and foreign commercial paper — 103,356 — 103,356 Total short-term marketable securities — 156,969 — 156,969 Total assets measured at fair value $ 47,553 $ 163,467 $ — $ 211,020 Money market funds are highly liquid and actively traded marketable securities that generally transact at a stable $1.00 net asset value representing its estimated fair value. The Company estimates the fair value of its U.S. and foreign corporate debt securities, asset backed securities, U.S. treasury securities and U.S. and foreign commercial paper by taking into consideration valuations obtained from third-party pricing services. The pricing services utilize industry standard valuation models, including both income and market-based approaches, for which all significant inputs are observable, either directly or indirectly, to estimate fair value. These inputs include reported trades of and broker/dealer quotes on the same or similar securities, issuer credit spreads; benchmark securities; prepayment/default projections based on historical data; and other observable inputs. During the quarter ended December 31, 2021, there was a triggering event that required the Company to perform an impairment analysis for both its goodwill and indefinite-lived asset. As a result, the Company recognized an impairment charge of $41.6 million for its goodwill and indefinite-lived asset. The Company considers the fair value used to determine the impairment charge to be a Level 3 measurement. See additional discussion relating to the Company’s impairment of goodwill and indefinite-lived asset in Note 5. There have been no transfers between Level 1, Level 2 or Level 3 for any of the periods presented. See Note 3 for further information regarding the carrying value of the Company’s investments in marketable securities. Revenue Recognition and Accounts Receivable from Collaborations The Company analyzes its 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, the Company considers 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 the Company’s consolidated statements of operations and comprehensive loss. Under certain collaborative arrangements, the Company has been reimbursed for a portion of its research and development expenses or participates 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 in the Company’s consolidated statements of operations and comprehensive loss, as the Company does not consider performing these activities for reimbursement to be a part of its 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 , the Company evaluates the term of the arrangement and recognizes revenue when the customer obtains control of promised goods or services in a contract for an amount that reflects the consideration the Company expects to receive in exchange for those goods or services. For contracts with customers, the Company applies 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 transa ction price to the performance obligations; and ( 5 ) recognition of revenue when (or as) the Company satisfies each performance obligation. The Company has provided standard indemnification and protection of licensed intellectual property for its customer. These provisions are part of assurance that the licenses meet the agreements, representations and are not obligations to provide goods or services. The Company only applies the five-step model to contracts when it is probable the Company will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. As part of the accounting for contracts with customers, the Company must develop assumptions that require judgment to determine the SSP of each performance obligation identified in the contract. The Company then allocates the total transaction price to each performance obligation based on the estimated standalone selling price (SSP) of each performance obligation. The Company recognizes 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 the Company’s intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, the Company recognizes 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, the Company utilizes 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, the Company applies an appropriate method of measuring progress for purposes of recognizing revenue from nonrefundable, upfront license fees. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. Development and Regulatory Milestone Payments Depending on facts and circumstances, the Company may record revenues from certain milestones in a reporting period before the milestone is achieved if the Company concludes achievement of the milestone is probable and recognition of revenue related to the milestone will not result in a significant reversal in amounts recognized in future periods. The Company records 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. The Company re-evaluates the probability of achievement of such milestones and any related constraint each reporting period. The Company adjusts its estimate of the overall transaction price, including the amount of collaborative revenue that was recorded, if necessary. Research and Development Service Payments Under the Research, Development, Collaboration and License Agreement (Allergan Agreement) with Allergan Pharmaceuticals International Limited (Allergan), the Company was reimbursed at a certain percentage for performing research and development services based on hours worked by the Company’s employees, at a fixed contractual rate per hour, and third-party pass-through costs the Company incurred on a quarterly basis. Research and development service payments were included in the transaction price in the reporting period the Company 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. The Company recorded the full reimbursed portion of these expenses as collaboration revenue associated with the Allergan Agreement in its consolidated statements of operations as the Company consider performing research and development services to be a part of its ongoing and central operations. Sales-based Milestone and Royalty Payment s The Company’s customer may be required to pay the Company sales-based milestone payments or royalties on future sales of commercial products. The Company recognizes revenues related to sales-based milestone and royalty payments upon the later to occur of (i) achievement of the collaborator’s underlying sales or (ii) satisfaction of any performance obligation(s) related to these sales, in each case assuming the Company’s licensed intellectual property is deemed to be the predominant item to which the sales-based milestones and/or royalties relate. The Company receives payments from its customer based on billing schedules established in the contract. Upfront payments and fees are recorded as deferred revenue upon receipt or when due until the Company performs its obligations under the arrangement. If the related performance obligation is expected to be satisfied within the next twelve months, these amounts will be classified in current liabilities. The Company recognizes a contract asset relating to its conditional right to consideration that is not subject to a constraint. Amounts are recorded as accounts receivable when the Company’s right to consideration is unconditional. A net contract asset or liability is presented for each contract with a customer. The Company does not assess whether a contract has a significant financing component if the expectation at contract inception is such that the period between payment by the customer and the transfer of the promised goods or services to the customer will be one year or less. At December 31, 2021 and 2020, all accounts receivable from collaborations are deemed collectible. Contract Liabilities The following tables present changes in the Company’s contract liabilities (in thousands): Balance at Beginning of Period Additions Deductions Balance at End of Period Year Ended December 31, 2021 Contract liabilities: Deferred revenue $ 8,987 $ — $ (6,254 ) $ 2,733 Year Ended December 31, 2020 Contract liabilities: Deferred revenue $ 37,048 $ 40,000 $ (68,061 ) $ 8,987 Year Ended December 31, 2021 2020 Collaboration revenue recognized in the period from Amounts included in deferred revenue at the beginning of the period $ 6,254 $ 37,048 Performance obligations satisfied in previous period — — Stock-Based Compensation The Company measures stock-based compensation to employees, consultants, Board members, and non-employees at fair value on the grant date of the award. The fair value of RSUs is determined based on the number of shares granted and the quoted market price of the Company’s common stock on the date of grant. Compensation cost is recognized as expense on a straight-line basis over the requisite service period of the award. Stock-based awards with graded vesting schedules are recognized using the accelerated attribution method on a straight-line basis over the requisite service period for each separately vesting portion of the award. For awards that have a performance condition, compensation cost is measured based on the fair value of the award on the grant date, the date performance targets are established, and is expensed over the requisite service period for each separately vesting tranche when achievement of the performance condition becomes probable. The Company assesses the probability of the performance conditions being met on a continuous basis. Forfeitures are recognized when they occur. The Company estimates the fair value of stock option grants that do not contain market-based vesting conditions using the Black-Scholes option pricing model . T he assumptions used in estimating the fair value of these awards, such as expected term, expected dividend yield , volatility and risk-free interest rate, represent management’s best estimates and involve inherent uncertainties and the application of management’s judgment. The Company is also required to make estimates as to the probability of achieving the specific performance conditions. If actual results are not consistent with the Company’s assumptions and judgments used in making these estimates, the Company may be required to increase or decrease compensation expense, which could be material to the Company’s consolidated results of operations. 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 and research and development and costs incurred under the Company’s collaboration agreements. Research and development costs are expensed as incurred unless there is an al

Investments in Marketable Secur

Investments in Marketable Securities	12 Months Ended
	Dec. 31, 2021
Investments Debt And Equity Securities [Abstract]
Investments in Marketable Securities	Note 3 - Investments in Marketable Securities Investments in marketable available-for-sale securities consisted of the following (in thousands): December 31, 2021 Amortized Cost Gross Unrealized Gain Gross Unrealized Loss Fair Value Cash equivalents Money market funds $ 42,507 $ — $ — $ 42,507 Total cash equivalents 42,507 — — 42,507 Short-term marketable securities U.S. and foreign corporate debt securities 7,015 — (2 ) 7,013 Asset-backed securities 29,097 — (38 ) 29,059 U.S. and foreign commercial paper 64,929 — (1 ) 64,928 Total short-term marketable securities 101,041 — (41 ) 101,000 Long-term marketable securities U.S. and foreign corporate debt securities 19,117 — (74 ) 19,043 U.S. treasury securities 8,960 — (31 ) 8,929 Total long-term marketable securities 28,077 — (105 ) 27,972 Total cash equivalents and marketable securities $ 171,625 $ — $ (146 ) $ 171,479 December 31, 2020 Amortized Cost Gross Unrealized Gain Gross Unrealized Loss Fair Value Cash equivalents Money market funds $ 47,553 $ — $ — $ 47,553 U.S. and foreign commercial paper 6,498 — — 6,498 Total cash equivalents 54,051 — — 54,051 Short-term marketable securities U.S. and foreign corporate debt securities 16,939 3 (3 ) 16,939 Asset-backed securities 12,674 2 (1 ) 12,675 U.S. treasury securities 23,997 2 — 23,999 U.S. and foreign commercial paper 103,356 — — 103,356 Total short-term marketable securities 156,966 7 (4 ) 156,969 Total cash equivalents and marketable securities $ 211,017 $ 7 $ (4 ) $ 211,020 Short-term marketable securities held as of December 31, 2021 had contractual maturities of less than one year. Long-term marketable securities December 31, 2021 had contractual maturities of at least one year but less than two years. Realized gains and losses for the years ended December 31, 2021 and 2020 were not significant. None of the Company’s investments have been in a continuous unrealized loss position for more than 12 months as of December 31, 2021. See Note 2 for further information regarding the fair value of our investments in marketable securities.

Property and Equipment, Net

Property and Equipment, Net	12 Months Ended
	Dec. 31, 2021
Property Plant And Equipment [Abstract]
Property and Equipment, Net	Note 4 - Property and Equipment, Net Property and equipment, net consists of the following (in thousands): December 31, 2021 2020 Lab equipment 18 247 Office equipment 699 699 Leasehold improvement 1,629 2,490 Total property and equipment 2,346 3,436 Less: Accumulated depreciation (1,207 ) (1,836 ) Property and equipment, net $ 1,139 $ 1,600 Depreciation expense for the years ended December 31, 2021 and 2020 was $0.5 million, and $0.7 million, respectively, and was recorded in both research and development expense and general and administrative expense in the consolidated statements of operations and comprehensive loss. Primarily all of the Company’s property and equipment is located in the U.S.

Goodwill and Indefinite-Lived I

Goodwill and Indefinite-Lived Intangible Assets Impairment	12 Months Ended
	Dec. 31, 2021
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill and Indefinite-Lived Intangible Asset Impairment	Note 5 - Goodwill and Indefinite-Lived Intangible Asset Impairment Goodwill The Company elected to perform a quantitative impairment assessment of goodwill for its single reporting unit in the fourth quarter of 2021 due to a sustained decline in its market capitalization, an increase in negative economic outlook for biotech markets and a fourth quarter unfavorable clinical trial result for a competitor’s curative combination therapy for HBV infection. The Company estimated and reconciled the fair value of its reporting unit using both a market approach, utilizing the Company’s market capitalization adjusted for an estimated control premium, and the income approach, discounting future cash flows based on management’s expectations of timelines to complete clinical trials, regulatory and commercial probabilities of technical success as well as future earnings forecast. Based on this analysis, and after completing an impairment assessment of its indefinite-lived and long-lived assets, the Company concluded the fair value of its single reporting unit was less than its carrying value and therefore recognized a goodwill impairment charge of $ 12.6 million. This was primarily driven by increased risks impacting the Company that, from the standpoint of a market participant, were captured through an increase in estimated discount rates. The calculation of the impairment charge includes substantial fact-based determinations and estimates including discount rates, future revenue, profitability, cash flows, probabilities of technical success and fair values of assets and liabilities, and any changes to these assumptions could result in changes to the fair value of our single reporting unit. The goodwill impairment charge is reflected in impairment of goodwill and indefinite-lived intangible asset in the consolidated statements of operations and comprehensive loss. No goodwill impairment charges were recorded in 2020. Indefinite-Lived Intangible Asset During the fourth quarter of 2021 and prior to the goodwill impairment test, the Company also completed a quantitative impairment test for its IPR&D asset associated with the Assembly Pharmaceuticals, Inc. acquisition. The Company utilized the discounted cash flow model of the income approach and determined the carrying value of its IPR&D asset was fully impaired resulting in an impairment charge of $29.0 million. This was primarily driven by a higher discount rate applied to future cash flows based on a market participant’s view of increased risk associated with a negative economic outlook for biotech markets and a fourth quarter unfavorable clinical trial result for a competitor’s curative combination therapy for HBV infection. More significant assumptions inherent in the development of the model included the estimated annual cash flows, particularly net revenues, the appropriate discount rate to select in order to measure the risk inherent in the future cash flows, cost to complete the IPR&D project as well as other factors. The impairment charge recorded is reflected in impairment of goodwill and indefinite-lived intangible asset in the consolidated statements of operations and comprehensive loss. No indefinite-lived intangible asset impairment charges were recorded in 2020.

Other Accrued Expenses

Other Accrued Expenses	12 Months Ended
	Dec. 31, 2021
Payables And Accruals [Abstract]
Other Accrued Expenses	Note 6 – Other Accrued Expenses Other accrued expenses consist of the following (in thousands): December 31, 2021 2020 Accrued expenses: Accrued compensation $ 6,426 $ 7,016 Accrued restructuring charges — 4,164 Accrued professional fees and other 437 807 Total accrued expenses $ 6,863 $ 11,987

Restructurings

Restructurings	12 Months Ended
	Dec. 31, 2021
Restructuring And Related Activities [Abstract]
Restructurings	Note 7 – Restructurings Restructuring charges relate to the Company’s decision to relocate its headquarters to South San Francisco, California, which was approved by the Board of Directors effective January 2020 and the December 2020 wind-down of the Company’s Microbiome program. The following table summarizes the Company’s costs incurred (in thousands): Total Restructuring Cost Employee Severance and Related Benefits Asset Impairment and Other Costs Cumulative restructuring costs incurred through December 31, 2021 $ 6,430 $ 3,240 $ 3,190 Restructuring costs incurred for the year ended December 31, 2021 $ (1,348 ) $ (2,959 ) (1) $ 1,611 Restructuring costs incurred for the year ended December 31, 2020 $ 5,684 $ 4,105 $ 1,579 (1) The cumulative restructuring costs incurred through December 31, 2021 represents all costs to be incurred. The following table presents where the restructuring charges were recognized (in thousands): Year Ended December 31, 2021 2020 Research and development $ (1,625 ) $ 5,486 General and administrative 277 $ 198 Total $ (1,348 ) $ 5,684 The following table presents the activity in the accrued restructuring charges during the period (in thousands): Total Restructuring Cost Employee Severance and Related Benefits Asset Impairment and Other Costs Accrued balance as of December 31, 2019 $ 2,094 $ 2,094 $ — Costs incurred 3,843 3,843 — Reductions for cash payments (1,773 ) (1,773 ) — Accrued balance as of December 31, 2020 $ 4,164 $ 4,164 $ — Costs incurred 1,611 — 1,611 Reductions for cash payments (5,775 ) (4,164 ) (1,611 ) (1) Accrued balance as of December 31, 2021 $ — $ — $ — (1) The asset impairment and other costs includes $1.4 million for the remaining payment obligations of leased equipment the Company purchased and sold to third parties. Microbiome Purchase Agreement In December 2021, the Company entered into an asset purchase agreement (the Microbiome Purchase Agreement) with a third party pursuant to which the Company sold know-how, patents, materials and regulatory filings for the Company’s Microbiome program. The sale included ABI-M201 (M201), which had been the Company’s lead candidate in its Microbiome program. As consideration for the sale, the Company was entitled to receive $3.0 million, of which $1.5 million was received in December 2021 and the remaining $1.5 million was received in February 2022. The Company is also entitled to receive a $10.0 million milestone payment upon the achievement of a regulatory approval milestone as defined in the purchase agreement. The Microbiome Purchase Agreement is within the scope of gains and losses from the derecognition of nonfinancial assets guidance since the Company had previously wound-down the Microbiome program, M201 was no longer a part of the Company’s ongoing major or central operations. The Company determined all assets sold under the Microbiome Purchase Agreement represent one distinct nonfinancial asset as individually, they do not have standalone value. The transaction price at the inception of the agreement was limited to the $3.0 million upfront payments. The variable consideration relating to the $10.0 million milestone has not been included in the transaction price as it was fully constrained as of December 31, 2021. As part of the Company’s evaluation of the development milestone constraint, it determined the achievement of the milestone is contingent upon success in future clinical studies and regulatory approvals which are not within its control and uncertain at this stage. The assets sold had no carrying value and the full $3.0 million transaction price resulted in the recognition of a gain. The Company determined the transfer of control of the assets sold was completed in December 2021. The $3.0 million gain is included as a reduction of research and development expenses in the Company’s consolidated statements of operations and comprehensive loss. The $1.5 million due as of December 31, 2021 is included in prepaid expenses and other current assets on the Company’s consolidated balance sheet.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2021
Equity [Abstract]
Stockholders' Equity	Note 8 - Stockholders’ Equity The Company is authorized to issue 5,000,000 shares of preferred stock as of December 31, 2021 and 2020. As of December 31, 2021 and 2020, no shares of preferred stock were issued and outstanding. The Company is authorized to issue 100,000,000 shares of common stock as of December 31, 2021 and 2020. Sale of Common Stock In August 2020, the Company filed a shelf registration statement on Form S-3 with the SEC, File No. 333-248469, that became effective on September 4, 2020 (the 2020 Registration Statement). The Company may from time to time sell any combination of the securities described in the 2020 Registration Statement in one or more offerings up to an aggregate offering price of $300.0 million. In connection with the filing of the 2020 Registration Statement, the Company entered into a sales agreement under which the Company may offer and sell shares of its common stock having an aggregate offering price of up to $100.0 million through “at-the-market” offerings (2020 ATM), which shares are included in the $300.0 million of securities registered pursuant to the 2020 Registration Statement. During the year ended December 31, 2020, the Company issued and sold 892,840 shares of common stock under the 2020 ATM, for which the Company received net proceeds of $5.5 million, after deducting commissions, fees and expenses. During the year ended December 31, 2021, the Company issued and sold 11,234,207 shares of common stock under the 2020 ATM, for which the Company received net proceeds of $52.8 million, after deducting commissions, fees and expenses. Common Stock Warrants In December 2019, the Company sold to various investors an aggregate of 6,287,878 shares of common stock at a public offering price of $16.50 per share, which included the exercise in full by the underwriters of their option to purchase 1,136,363 shares of common stock, and pre-funded warrants to purchase 2,424,242 shares of common stock at a public offering price of $16.499. The Company received aggregate net proceeds of $134.7 million from the offering and the option exercise, after deducting underwriting discounts and commissions and offering expenses payable by the Company. The pre-funded warrants became immediately exercisable upon issuance at an exercise price of $0.001 per share, but under their terms, the outstanding pre-funded warrants to purchase shares of the Company’s common stock generally may not be exercised if the holder’s ownership of the Company’s common stock would exceed 19.99% following such exercise. The exercise price and number of shares of common stock issuable upon the exercise of the pre-funded warrants (Warrant Shares) are subject to adjustment in the event of any stock dividends and splits, reverse stock split, recapitalization, reorganization or similar transaction, as described in the pre-funded warrant agreements. Under certain circumstances, the pre-funded warrants may be exercisable on a “cashless” basis. Both the pre-funded warrants and the Warrant Shares are registered securities. The pre-funded warrants were classified as a component of permanent stockholders’ equity within additional paid-in-capital and were recorded at the issuance date using a relative fair value allocation method. The Company valued the pre-funded warrants at issuance, concluding their sales price approximated their fair value, and allocated net proceeds from the sale proportionately to the common stock and pre-funded warrants of which $37.5 million allocated to the pre-funded warrants and recorded as a component of additional paid-in-capital. T he following warrants to purchase shares of the Company’s common stock were issued and outstanding: Issue date Expiration date Exercise Price per Share As of December 31, 2021 As of December 31, 2020 December 16, 2019 None $ 0.001 — 2,424,242 During the year ended December 31, 2021, there were 2,424,242 pre-funded warrants exercised through a cashless exercise, resulting in the issuance of 2,423,634 shares of the Company’s common stock. There were no pre-funded warrants exercised during the year ended December 31, 2020. During the year ended December 31, 2020, 15,296 warrants to purchase common stock expired unexercised.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	Note 9 - Stock-Based Compensation Equity Incentive Plans In June 2020, the Company’s stockholders approved an amendment to the Assembly Biosciences, Inc. 2018 Stock Incentive Plan (the 2018 Plan) that increased the aggregate number of shares of common stock reserved under the 2018 Plan to 4,600,000. In May 2021, the Company’s stockholders approved an amendment to the 2018 Plan that increased the aggregate number of shares of common stock reserved under the 2018 Plan to 6,600,000 and the Assembly Biosciences, Inc. Employee Stock Purchase Plan (the 2018 ESPP) that, among other things, increased the number of shares of common stock reserved to an aggregate of 1,300,000. As of December 31, 2021, the Company had awards outstanding under the following shareholder approved plans: 2010 Equity Incentive Plan (the 2010 Plan), which has been frozen; the Amended and Restated 2014 Stock Incentive Plan (the 2014 Plan); and the 2018 Plan. Shares of common stock underlying awards that are forfeited under the 2010 Plan on or after June 2, 2016 will become available for issuance under the 2014 Plan. As of December 31, 2021, the Company also had awards outstanding under the Assembly Biosciences, Inc. 2017 Inducement Award Plan (the 2017 Plan), the 2019 Inducement Award Plan (the 2019 Plan) and the Assembly Biosciences, Inc. 2020 Inducement Award Plan (the 2020 Plan). The Company issues new shares of common stock to settle options exercised or vested RSUs. The Company also issues new shares of common stock in connection with purchases of shares of common stock by eligible employees under the Company’s 2018 ESPP. Stock Plan Activity Stock Options The following table summarizes the stock option activity and related information for 2021: Number of Shares Weighted Average Exercise Price Per Share Weighted Average Remaining Contractual Term (Years) Total Intrinsic Value (in thousands) Outstanding as of December 31, 2020 6,696,592 $ 15.70 6.9 $ 1,856 Granted 1,521,370 4.24 Forfeited (2,046,861 ) 18.93 Expired (9,200 ) 30.00 Outstanding as of December 31, 2021 6,161,901 $ 11.77 6.4 $ 53 Options vested and exercisable as of December 31, 2021 3,805,841 $ 13.53 5.0 $ 51 The weighted-average grant-date fair value of options granted was $3.05 and $10.64 during the years ended December 31, 2021 and 2020, respectively. The total intrinsic value of options exercised in 2020 was $2.0 million. There were no options exercised in 2021. RSUs The following table summarizes RSU activity and related information for 2021: Number of RSUs Weighted Average Fair Value Per RSU at Grant Price Nonvested as of December 31, 2020 886,868 $ 20.36 Granted 721,341 3.78 Vested (347,096 ) 27.97 Forfeited (290,774 ) 14.64 Nonvested as of December 31, 2021 970,339 $ 7.04 The total fair value of RSUs vested and settled during 2021 and 2020 was $3.7 million and $7.8 million, respectively. The total intrinsic value of RSUs vested and settled during 2021 and 2020 was $1.4 million and $4.4 million, respectively. In September 2019, the Company granted 100,000 RSUs with performance-based vesting conditions to its chief executive officer. On March 31, 2021, 25,000 of these awards were forfeited back to the Company due to the expiration of the time period to complete one of the performance conditions. On July 31, 2021, an additional 25,000 of these awards were forfeited back to the Company due to the expiration of the time period to complete one of the performance conditions. The outstanding 50,000 awards with an aggregate fair value of $0.4 million vest upon performance conditions not yet deemed probable. Accordingly, no stock-based compensation expense has been recognized as of December 31, 2021. In July 2020, the performance condition for 45,000 RSUs granted in December 2017 to a former executive officer was met associated with the execution of an HBV business development transaction. The Company recognized $0.7 million as a cumulative catch-up adjustment of stock-based compensation expense for this award for the year ended December 31, 2020. In July 2021, the Company granted a total of 324,214 RSUs with performance-based vesting conditions upon the achievement of clinical milestones to the majority of employees, including executive officers. The awards had a grant date fair value of $ 1.2 million and vest upon performance conditions not yet deemed probable. Accordingly, no stock-based compensation expense has been recognized as of December 31, 2021. Employee Stock Purchase Plan The 2018 ESPP provides for the purchase by employees of up to an aggregate of 1,300,000 shares of the Company’s common stock at a discount to the market price. Eligible employee may participate through payroll deductions of up to 15% of such employee’s compensation for each pay period subject to annual statutory limits and the 2018 ESPP’s limit, which the Company’s stockholders approved in May 2021 to increase from 1,000 to 2,500 shares of common stock per offering. Eligible employees can purchase the Company’s common stock at the end of a predetermined offering period at 85% of the lower of the fair market value at the beginning or end of the offering period. Under the 2018 ESPP, the offering periods end on the last business day occurring on or before May 14 or November 14. The ESPP is compensatory and results in stock-based compensation expense. In May and November 2020, employees purchased 42,266 and 44,546 shares of common stock, respectively, under the 2018 ESPP. In May and November 2021, employees purchased 42,803 and 46,017 shares of common stock, respectively, under the 2018 ESPP. As of December 31, 2021, 1,043,515 shares of common stock are available for future sale under the Company’s 2018 ESPP. Stock-based compensation expense recorded in connection with the 2018 ESPP was $0.1 million and $0.5 million for the years December 31, 2021 and 2020, respectively. Valuation Assumptions The Company used the Black-Scholes option-pricing model for determining the estimated fair value and stock-based compensation related to stock options and ESPP purchase rights. A summary of the assumptions used to estimate the fair values of stock options grants for the years presented is as follows: Year Ended December 31, 2021 2020 Exercise price $2.24 - $5.79 $5.62 - $23.30 Expected volatility 79.7% - 91.2% 66.4% - 92.3% Risk-free rate 0.50% - 1.37% 0.26% - 1.44% Expected term (years) 5.5 - 7.5 5.5 - 7.5 Expected dividend yield 0% 0% The risk-free interest rate assumption was based on the rates for U.S. Treasury zero-coupon bonds with maturities similar to those of the expected term of the stock option being valued. The expected dividend yield was zero as the Company currently does not intend to pay dividends in the foreseeable future. The weighted average expected term of options was calculated using the simplified method as prescribed by accounting guidance for stock-based compensation due to the Company’s limited history of relevant stock option exercise activity. The expected volatility was calculated based on the Company’s historical stock prices, supplemented as necessary with historical volatility of the common stock of several peer companies with characteristics similar to those of the Company. The fair value of ESPP purchase rights were not material for any period presented. Stock-Based Compensation Expense The Company recognized stock-based compensation expense included in the consolidated statement of operations and comprehensive loss for the years presented (in thousands): Year Ended December 31, 2021 2020 Research and development $ 548 $ 11,380 General and administrative 4,689 10,473 Total stock-based compensation expense $ 5,237 $ 21,853 Stock-based compensation expense for the year ended December 31, As of December 31, , there was $9.7 million of total unrecognized stock-based compensation related to outstanding equity awards which is expected to be recognized over a weighted average remaining amortization period of

Collaboration Agreements

Collaboration Agreements	12 Months Ended
	Dec. 31, 2021
Collaboration Agreement [Abstract]
Collaboration Agreements	Note 10 - Collaboration Agreements Allergan Agreement In January 2017, the Company and Allergan Pharmaceuticals International Limited (Allergan) entered into the Research, Development, Collaboration and License Agreement (the Allergan Agreement) to develop and commercialize select microbiome gastrointestinal disease therapies. In June 2020, following its acquisition of Allergan, AbbVie Inc. (AbbVie), on behalf of Allergan, gave written notice of termination of the Allergan Agreement, which subsequently became effective in October 2020. Upon termination, the licenses granted by the Company and its know-how reverted to the Company. For the year ended December 31, 2020, the Company recognized $48.1 million in collaboration revenue associated with the Allergan Agreement. A contract asset balance of $1.0 million was recorded as of December 31, 2020. There were no deferred revenue contract liabilities as of December 31, 2020 and no revenue, contract assets or contract liabilities recognized as of and for the year ended December 31, 2021 due to the termination of the Allergan Agreement in 2020. BeiGene Agreement In July 2020, the Company and BeiGene, Ltd. (BeiGene) entered into a Collaboration Agreement (the BeiGene Agreement) to develop and commercialize the Company’s novel core inhibitor product candidates VBR, ABI-H2158 and ABI-H3733 for chronic HBV infection (the Licensed Product Candidates) in the People’s Republic of China, Hong Kong, Taiwan and Macau (the Territory). Under the agreement, the Company and BeiGene are collaborating on certain global clinical studies and both the Company and BeiGene will independently conduct other clinical studies in their own respective territories. BeiGene agreed to pay all development and regulatory costs for the Licensed Product Candidates in the Territory up to an aggregate of $45.0 million. Development and regulatory costs for the Licensed Product Candidates for the Territory in excess of $45.0 million will be shared equally by the Company and BeiGene. If the Company conducts certain ancillary trials outside of the plan to develop these candidates in the Territory, BeiGene may elect to obtain access to the know-how and clinical data resulting for such ancillary trials and shall reimburse the Company proportionally for the Territory of the costs of such trials. although the parties may approve BeiGene to take on some or all of the commercial supply activities of the applicable Licensed Products in the Territory. The Company is not obligated to perform pre-phase 3 clinical trial development work outside the Territory on ABI-H2158 and ABI-H3733 but must provide BeiGene pre-Phase 3 clinical trial know-how and development results if and when such development efforts are completed. If, after ABI-H2158 and ABI-H3733 reach the end of Phase 2 clinical trials, the Company and BeiGene are unable to mutually agree on the terms of a Phase 3 global study, BeiGene may elect to terminate the BeiGene Agreement solely as it relates to that compound, as applicable. Such a termination would result in the Company regaining all rights to the applicable compound in the Territory. In addition, BeiGene may terminate the BeiGene Agreement for convenience at any time upon 90 days’ advance written notice to Assembly. The BeiGene Agreement also contains customary provisions for termination by either party, including in the event of breach of the BeiGene Agreement, subject to cure. Pursuant to the terms of the BeiGene Agreement, the Company received an upfront cash payment of $40.0 million from BeiGene for the delivery of exclusive, royalty-bearing licenses to develop and commercialize the Licensed Product Candidates in the Territory, and the Company was eligible to receive up to approximately $500.0 million in cash milestone payments, comprised of up to $ 113.8 million for development and regulatory milestones and up to $ 385.0 million in net sales milestones. In addition, the Company is eligible to receive tiered royalties at percentages ranging from the mid-teens to the low thirties of net sales. In September 2021, the Company discontinued development of ABI-H2158 following the observation of elevated alanine transaminase levels in the Phase 2 clinical study consistent with drug-induced hepatotoxicity. Due to the discontinuation of development of ABI-H2158, the maximum cash milestone payments the Company is eligible to receive for VBR and ABI-H3733 is $ 427.5 million, comprised of up to $ 97.5 million for development and regulatory milestones and up to $ 330.0 million in net sales milestones. The collaborative arrangements guidance as both parties are active participants and are exposed to significant risks and rewards dependent on the success of commercializing the Licensed Product Candidates in the Territory but that the unit of account related to the delivery of Licensed Product Candidates is within the scope of the contract with customers guidance. The remaining units of account related to participation on the JSC and subcommittees, clinical supply and other in Territory and global development activities (the Collaboration Activities) are within the scope of the collaborative arrangements guidance. Commercial supply will be evaluated as a separate contract when the agreement is executed and a purchase order is received from BeiGene. The Company identified the following material promises related to the contract with customers unit of account under the BeiGene Agreement ABI-H2158 , and 3) the transfer of the ABI-H3733 License. The Company concluded each of these licenses to be functional BeiGene . The ABI-H2158 and ABI-H3733 Licenses have a The agreed upon prices for the clinical and commercial supply of the Licensed Product Candidates to BeiGene do not represent material rights, and therefore are not performance obligations, and such pricing on an aggregate basis represents the SSP an entity would typically pay for such a product in that region or market. There are also no minimum purchase commitments. The Company estimated the SSP of the Licenses using an income-based valuation approach for the estimated value a licensor of the compounds would receive considering the stage of the compound’s development. The Company believes a change in the assumptions used to determine its best estimate of SSP would not have a significant value or significant impact on the allocation of consideration received. The transaction price at the inception of the agreement was limited to the $40.0 million upfront payment. The variable consideration related to the remaining development and commercialization milestone payments has not been included in the transaction price as these were fully constrained as of December 31, 2021 and 2020. As part of the Company’s evaluation of the development and commercialization milestones constraint, the Company determined the achievement of such milestones are contingent upon success in future clinical trials and regulatory approvals which are not within its control and uncertain at this stage. Any variable consideration related to sales-based milestones (including royalties) will be recognized when the related sales occur as they were determined to relate predominantly to the Licensed Product Candidates granted to BeiGene. The Company will reevaluate the transaction price in each reporting period as uncertain events are resolved or other changes in circumstances occur. During the year ended December 31, 2020, the Company recognized $31.0 million as collaboration revenue for the amount allocated to the VBR License as substantial completion of the license technology transfer had occurred. The remaining transaction price allocated to the ABI-H2158 and ABI-H3733 Licenses of $9.0 million was recorded as a long-term deferred revenue contract liability on the consolidated balance sheet as of December 31, 2020. Following the discontinuation of development of ABI-H2158 in September 2021, the obligation related to the technology transfer associated with the license of ABI-H2158 was considered to be complete. Accordingly, the Company recognized $6.3 million as collaboration revenue for the amount allocated to ABI-H2158 during the year ended December 31, 2021. The remaining transaction price allocated to the ABI-H3733 License of $2.7 million was recorded as a long-term deferred revenue contract liability on the consolidated balance sheet as of December 31, 2021. Payments to, or reimbursements from, BeiGene related to the Collaboration Activities will be accounted for as an increase to or reduction of research and development expenses when incurred or realized, respectively. During the years ended December 31, 2021 and 2020, the Company did not recognize any increase or reduction of research and development expense under the BeiGene Agreement. The Company incurred $3.5 million in incremental costs of obtaining the BeiGene Agreement. These contract costs have been capitalized and are being recognized consistent with the pattern of recognition of revenue associated with the Licensed Product Candidates. As of December 31, 2021 and 2020, the remaining unamortized contract costs are $0.2 million and $0.8 million, respectively, and are included in other assets on the consolidated balance sheet. Arbutus Agreement In August 2020, the Company and Arbutus Biopharma Corporation (Arbutus) entered into a Collaboration Agreement (Arbutus Agreement) to conduct a randomized, multi-center, open-label Phase 2 clinical trial to explore the safety, PK and antiviral activity of the triple combination of VBR, AB-729 and an NrtI compared to the double combinations of VBR with an NrtI and AB-729 with an NrtI. The Arbutus Agreement is within the scope of the collaborative arrangements guidance as both parties are active participants and are exposed to significant risks and rewards dependent on the success of the collaborative activity. Arbutus is not a customer as it does not obtain an output from the collaborative activities as they were not provided an exclusive license to VBR or the ability to manufacture VBR, and the Company does not consider performing such collaborative activities to be a part of its ongoing activities. The revenue from contracts with customers guidance was considered by analogy in determining the unit of account, and the recognition and measurement of such unit of account for collaborative activities under the Agreement and concluded there is one activity, to run open-label Phase 2 clinical trial is akin to performance obligation related to collaborative activities. Reimbursements and cost-sharing portions of this performance obligation will be reflected as a reduction of research and development expense when realized in the Company’s consolidated statements of operations, as the Company does not consider performing research and development services for reimbursement to be a part of its ongoing major or central operations. T 2.0 million he years ended December 31 Antios Agreement In July 2021, the Company and Antios Therapeutics, Inc. (Antios) entered into a Clinical Trial Collaboration Agreement (the Antios Agreement) to collaborate on a clinical trial of a combination therapy using either or both of the Company’s core inhibitors, VBR and ABI-H2158, and Antios’s active site polymerase inhibitor nucleotide ATI-2173 for the treatment of HBV. Assembly and Antios will individually be responsible for the study’s manufacturing costs but will equally share the remaining costs of the study. The Antios Agreement does not bind either party to conducting a collaboration trial or collaboration trial cohort unless and until a Joint Development Committee (the JDC) formed by both parties decides to initiate a collaboration trial or collaboration trial cohort. Due to the discontinuation of development of ABI-H2158 in September 2021, any study under the Antios Agreement would be with VBR. The Antios Agreement is within the scope of the collaborative arrangements guidance as both parties are active participants and are exposed to significant risks and rewards dependent on the success of the collaborative activity. Antios is not a customer as it does not obtain an output from the collaborative activities as they were not provided an exclusive license to ABI-H2158 or VBR or the ability to manufacture ABI-H2158 or VBR, and the Company does not consider performing such collaborative activities to be a part of its ongoing activities. In October 2021, the JDC agreed to initiate a collaboration trial cohort to evaluate a triple combination treatment in patients with chronic HBV infection. There were no costs incurred during the year ended December 31, 2021.

Milestones and Research Agreeme

Milestones and Research Agreements	12 Months Ended
	Dec. 31, 2021
Milestones And Research Agreements [Abstract]
Milestones and Research Agreements	Note 11 – Milestones and Research Agreements HBV Research Agreement with Indiana University Since September 2013, the Company has been party to an exclusive License Agreement dated September 3, 2013 with Indiana University Research and Technology Corporation (IURTC) from whom it has licensed aspects of the Company’s HBV program held by IURTC. The license agreement requires the Company to make milestone payments based upon the successful accomplishment of clinical and regulatory milestones. The aggregate amount of all performance milestone payments under the IURTC license agreement, should all milestones through development be met, is $0.8 million, with a portion related to the first performance milestone having been paid. The Company is obligated to pay IURTC royalty payments based on net sales of the licensed technology as well as a portion of any sublicensing revenue Assembly receives. The Company is also required to pay diligence maintenance fees each year to the extent that the royalty, sublicensing, and milestone payments to IURTC are less than the diligence maintenance fee for that year. A performance milestone totaling $0.1 million was determined to have occurred under this agreement and was paid during the year ended December 31, 2020. Additionally, the Company paid IURTC $0.7 million as a sublicensing fee during the year ended December 31, 2020. No Microbiome Targeted Colonic Delivery Platform In November 2013, the Company entered into a License and Collaboration Agreement with Therabiome, LLC (Therabiome), for all intellectual property and know-how owned or controlled by Therabiome relating to the oral delivery of pharmaceutical drugs to specific sites in the intestine, using a pH sensitive controlled release capsule-in-capsule technology. The Company will be solely responsible for all research and development activities with respect to any product it develops under the license. The Company was obligated to pay Therabiome clinical and regulatory milestones for each product or therapy advanced from the platform for U.S. regulatory milestones. In addition, the Company was obligated to pay Therabiome lesser amounts for foreign regulatory milestones, which varied by country and region. The Company was also required to pay Therabiome royalties on annual net sales of a product in the low to mid-single digit percentages plus, once annual net sales exceeded certain thresholds, a one-time cash payment upon reaching such thresholds. Therabiome was obligated to pay the Company royalties on annual net sales of any product Therabiome was permitted to develop using the intellectual property in the low double to mid-double-digit percentages, depending on the level of development or involvement the Company had in the product. No amounts were incurred or accrued for this agreement as of and for the years ended December 31, 2021 and 2020. In connection with the wind-down of the Microbiome program, the License and Collaboration Agreement with Therabiome was terminated in January 2021, and the termination became effective in April 2021. Door Agreement In November 2020, the Company and Door Pharmaceuticals, LLC (Door Pharma) entered into an exclusive, two-year During the years ended December 31, 2021 and 2020, the Company incurred research and development funding of $1.8 million and $0.3 million, respectively. Additionally, a performance milestone totaling $0.2 million was determined to have occurred under this agreement and was paid during the year ended December 31, 2021. Under the consolidation accounting standard , the Company determined that Door Pharma is a VIE. The Company does not have the power to direct the activities that most significantly affect the economic performance of Door Pharma and as such the Company is not the primary beneficiary and consolidation is not required. As of December 31, 202 1 , the Company has not provided financial or other support to Door Pharma that was not contractually required.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Income Taxes	Note 12 - Income Taxes Income tax benefit is as follows (in thousands): As of December 31, 2021 2020 Federal: Current — — Deferred 1,160 — $ 1,160 $ — State: Current — — Deferred 1,371 — $ 1,371 $ — Income tax benefit $ 2,531 $ — The effective tax rate of our provision for income taxes differs from the federal statutory rate as follows: As of December 31, 2021 2020 Statutory federal income tax rate 21.0 % 21.0 % State taxes, net of federal tax benefit 5.8 6.1 Research and development tax credits 2.3 2.2 Return to provision adjustments (0.2 ) 4.3 Other (0.6 ) 0.1 Uncertain tax positions (0.5 ) 2.2 Impairment of goodwill (2.0 ) — Stock-based compensation (4.5 ) 0.7 Change in valuation allowance (19.4 ) (36.6 ) Income taxes benefit 1.9 % 0.0 % Significant components of the Company’s deferred taxes are as follows (in thousands): As of December 31, 2021 2020 Deferred tax assets: Federal and state-operating loss carryforwards $ 133,671 $ 108,236 Stock-based compensation 11,082 16,563 Operating lease liabilities 1,656 2,600 Research and development credits 11,106 8,872 Other 1,125 2,317 Total deferred tax assets 158,640 138,588 Valuation allowance (157,095 ) (131,332 ) Deferred tax asset, net of valuation allowance $ 1,545 $ 7,256 Deferred tax liabilities: In-process research and development $ — $ (7,443 ) Operating lease right-of-use assets (1,545 ) (2,344 ) Total deferred tax liabilities (1,545 ) (9,787 ) Net deferred tax liability $ — $ (2,531 ) The Company maintains a valuation allowance on deferred tax assets due to the uncertainty regarding the ability to utilize these deferred tax assets in the future. The valuation allowance increased by $25.8 million and $22.8 million for the years ended December 31, and , respectively, Net operating loss and tax credit carryforwards as of December 31, 2021 are as follows (in thousands): Amount Expiration Years Net operating losses, federal (post December 31, 2017) $ 346,847 Indefinite Net operating losses, federal (pre January 1, 2018) 123,552 2027 - 2037 Net operating loss, state (Indefinite) 880 Indefinite Net operating loss, state (Definite) 545,256 2031 - 2041 Research and development tax credits, federal 10,845 2028 - 2041 Research and development tax credits, state 4,174 Indefinite Pursuant to Internal Revenue Code (IRC), Section 382 and 383, use of the Company’s U.S. federal and state net operating loss and research and development income tax credit carryforwards may be limited in the event of a cumulative change in ownership of more than 50.0% within a three-year period. The Company has performed an ownership change study through December 31, 2020 and has determined that a “change in ownership” as defined by IRC Section 382 and the rules and regulations promulgated thereunder, did occur in December 2010, January 2013 and October 2014. The Company has adjusted its net operating loss carryovers to appropriately reflect any attributes which will expire due to the limitation. The Company has not performed any additional analysis for IRC Sections 382 and 383 and there is a risk that additional changes in ownership could have occurred since December 31, 2020. If a change in ownership were to have occurred, additional net operating loss and tax credit carryforwards could be eliminated or restricted. If eliminated, the related asset would be removed from the deferred tax asset schedule with a corresponding reduction in the valuation allowance. The following table summarizes activity related to the Company’s gross unrecognized tax benefits (in thousands): As of December 31, 2021 2020 Balances as of beginning of year $ 2,655 $ 6,070 Increases related to prior year tax positions 1 — Decreases related to prior year tax positions (82 ) (4,162 ) Increases related to current year tax positions 663 747 Balances as of end of year $ 3,237 $ 2,655 The unrecognized tax benefits, if recognized, would not have an impact on the Company’s effective tax rate assuming the Company continues to maintain a full valuation allowance position. Based on prior year’s operations and experience, the Company does not expect a significant change to its unrecognized tax benefits over the next twelve months. The unrecognized tax benefits may increase or change during the next year for unexpected or unusual items for items that arise in the ordinary course of business. In subsequent periods, any interest and penalties related to uncertain tax positions will be recognized as a component of income tax expense. The Company files income tax returns in the U.S. federal, California and other state and foreign jurisdictions and is not currently under examination by federal, state, or local taxing authorities for any open tax years. Due to net operating loss carryforwards, all years effectively remain open for income tax examination by tax authorities in the U.S. and states in which the Company files tax returns.

Leases

Leases	12 Months Ended
	Dec. 31, 2021
Lease Cost [Abstract]
Leases	Note 13 - Leases Operating Leases The Company leases office and laboratory space in South San Francisco, California under a sub-sublease that expires in December 2023. The sub-sublease contains scheduled rent increases over the lease term. The Company also leases office space in Carmel, Indiana under a lease agreement that expires in August 2023. In February 2021, the Company subleased substantially all of the office space under lease in Carmel, Indiana for the remainder of its term. The Company also leased office and laboratory space in Groton, Connecticut that supported the Microbiome program under a lease that expired in June 2021. Due to the wind-down of the Microbiome program, the lease was not renewed. The Company’s China subsidiary leased office space and lab space in Shanghai, which the Company let expire in March 2021 and December 2020, respectively. The Company’s also leased office space in Beijing under a lease agreement which the Company let expire in December 2021. The Company’s China subsidiary leases registrational offices in Shanghai and Beijing under leases which expire in May 2022 and October 2022, respectively. Certain lease contracts contain renewal clauses that the Company assesses on a case-by-case basis. The Company also leases certain laboratory equipment accounted for as operating leases expiring at various dates, with the final lease expiring in 2024. In February 2021, the Company purchased substantially all of the leased equipment used for the Microbiome program from its leasing agency and sold this equipment to third parties (see Note 7). When the Company cannot determine the implicit rate in its leasing arrangements, the Company uses its incremental borrowing rate as the discount rate when measuring operating lease liabilities. The incremental borrowing rate represents an estimate of the interest rate the Company would incur at lease commencement to borrow an amount equal to the lease payments on a collateralized basis over the term of a lease within a particular currency environment. At December 31, 2021, the Company had operating lease liabilities of $6.5 million and right-of-use assets of $6.0 million. The following summarizes quantitative information about the Company’s operating leases (in thousands): Year Ended December 31, 2021 2020 Lease cost Operating lease cost $ 3,840 $ 5,214 Short-term lease cost 268 401 Variable lease cost 1,317 1,468 Sublease income (142 ) — Total lease cost, net $ 5,283 $ 7,083 Year Ended December 31, 2021 2020 Operating cash flows from operating leases $ 3,786 $ 4,513 ROU assets exchanged for new operating lease liabilities $ 126 $ 1,302 As of December 31, 2021, the weighted-average remaining lease term for operating leases was 1.9 years and the weighted-average discount rate for operating leases was 9.7%. As of December 31, 2021, the maturities of the Company’s operating lease liabilities were as follows (in thousands): 2022 3,643 2023 3,491 2024 10 Total 7,144 Less: present value discount (668 ) Operating lease liabilities $ 6,476

Employee Benefit Plan

Employee Benefit Plan	12 Months Ended
	Dec. 31, 2021
Compensation And Retirement Disclosure [Abstract]
Employee Benefit Plan	Note 14 - Employee Benefit Plan In January 2018, the Company established a defined contribution 401(k) plan (the Plan) for all employees who are at least 21 years of age. Employees are eligible to participate in the Plan upon commencement of employment. Under the terms of the Plan, employees may make voluntary contributions as a percentage of compensation. The Plan also permits the Company to make discretionary matching contributions. In both 2021 and 2020, the Company made discretionary matching contributions of $0.9 million.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies and Recent Accounting Pronouncements (Policies)	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation These consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (U.S. GAAP) and include the accounts of the Company and its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation.
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that may affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and reported amounts of expenses during the reporting period. Actual results could differ from those estimates. Significant estimates inherent in the preparation of the accompanying consolidated financial statements include estimates of costs incurred but not yet invoiced for research and development accruals, the estimated fair value of our indefinite-lived intangible asset and the estimated fair value of our reporting unit for purposes of evaluating goodwill impairment. The Company’s estimates could be affected by external conditions, including those unique to the Company and general economic conditions. It is reasonably possible that these external factors could have an effect on the Company’s estimates and could cause actual results to differ from those estimates and assumptions.
Other Risks And Uncertainties	Other Risks and Uncertainties In March 2020, the World Health Organization declared the COVID-19 outbreak a pandemic. The ongoing COVID-19 pandemic and its broad, global impacts, including supply chain disruptions, have impacted certain aspects of the Company’s business, including where and how the Company’s employees work in its labs and offices and how and when the Company’s nonclinical and clinical studies are conducted. Early in the pandemic, the Company’s current and future planned clinical trials and preclinical studies were largely unaffected, but as the pandemic has continued, the Company has experienced enrollment delays for its current clinical studies, particularly its two ongoing multi-drug combination studies. However, the Company cannot at this time predict the specific extent, duration, or full impact the COVID-19 pandemic will have on its business, operations, strategy, prospects and financial condition and results. The impact of the COVID-19 pandemic on the Company’s financial performance will depend on future developments, including the duration and spread of the outbreak and related governmental advisories and restrictions. These developments and the impact of the COVID-19 pandemic on the financial markets and the overall economy are highly uncertain. If the financial markets and/or the overall economy are impacted for an extended period, the Company’s results may be adversely affected. In addition, the study design of an upcoming triple combination study initially included a site in Ukraine. The Company will no longer be conducting the study there due to the instability resulting from Russia’s recent invasion of Ukraine. These changes to the Company’s study plan will result in a delayed data readout.
Cash and Cash Equivalents	Cash and Cash Equivalents All highly liquid investments, including money market funds, with original maturities of three months or less at the time of purchase are considered to be cash equivalents. All of the Company’s cash equivalents have liquid markets and high credit ratings. The Company maintains its cash in bank deposits and other accounts, the balances of which, at times as of and during the years ended December 31, 2021 and 2020, exceed federally insured limits.
Investments in Marketable Securities	Investments in Marketable Securities The Company invests its excess cash in debt securities with high credit ratings including but not limited to money market funds classified as cash equivalents, asset backed securities, securities issued by the U.S. government and its agencies, corporate debt securities and commercial paper. The Company has designated its investments in marketable securities as available-for-sale and measures these securities at their respective fair values. Marketable securities are classified as short-term or long-term based on the maturity date and their availability to meet current operating requirements. Marketable securities that mature in one year or less from the consolidated balance sheet date are classified as short-term available-for-sale securities, while marketable securities with maturities in one year or beyond one year from the consolidated balance sheet date are classified as long-term. Securities that are classified as available-for-sale are measured at fair value with temporary unrealized gains and losses reported in other comprehensive loss, and as a component of stockholders' equity until their disposition. The Company reviews all available-for-sale securities at each period end to determine if they remain available-for-sale based on their current intent and ability to sell the security if it is required to do so. Realized gains and losses from the sale of marketable securities, if any, are calculated using the specific-identification method. Marketable securities are subject to a periodic impairment review. The Company may recognize an impairment charge when a decline in the fair value of investments below the cost basis is determined to be other-than-temporary. In determining whether a decline in market value is other-than-temporary, various factors are considered, including the cause, duration of time and severity of the impairment, any adverse changes in the investees’ financial condition, and the Company’s intent and ability to hold the security for a period of time sufficient to allow for an anticipated recovery in market value. To date, there have been no declines in value deemed to be other than temporary for any of the Company’s investments in marketable securities .
Goodwill and Indefinite-Lived Intangible Asset	Goodwill and Indefinite-Lived Intangible Asset Goodwill and indefinite-lived intangible asset 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. Goodwill The difference between the purchase price and the fair value of assets acquired and liabilities assumed in a business combination is allocated to goodwill. Goodwill is evaluated for impairment on an annual basis as of October 1, and more frequently if indicators are present or changes in circumstances suggest impairment may exist. In performing each annual impairment assessment and any interim impairment assessment, the Company determines if it should qualitatively assess whether it is more likely than not the fair value of goodwill is less than its carrying amount (the qualitative impairment test). If the Company concludes it is more likely than not 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. The Company’s annual or interim quantitative impairment testing is performed by comparing the estimated Indefinite-Lived Intangible Asset The Company’s indefinite-lived intangible asset consists of IPR&D associated with small molecule core inhibitors that directly target and allosterically inhibit core protein functions associated with HBV which were acquired with the acquisition of Assembly Pharmaceutics, Inc. in 2014. IPR&D represents the fair value assigned to incomplete research projects the Company acquired through a business combination which, at the time of acquisition, had not reached technological feasibility, regardless of whether they had 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. The Company classifies IPR&D 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, the Company performed 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, the Company would write-off the remaining carrying amount of the associated IPR&D intangible asset. Indefinite-lived intangible assets are not amortized, but instead are reviewed for impairment at least annually, or more frequently if events occur or circumstances change that would indicate the carrying amount may be impaired. In performing each annual impairment assessment and any interim impairment assessment, the Company determines if it should qualitatively assess whether it is more likely than not the fair value of its IPR&D asset is less than its carrying amount (the qualitative impairment test). If the Company concludes that is the case, or elects not to use the qualitative impairment test, the Company 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, the Company considers the results of the most recent quantitative impairment test and identifies the most relevant drivers of the fair value for the IPR&D asset. The most relevant drivers of fair value identified are consistent with the assumptions used in the quantitative estimate of the IPR&D asset. Using these drivers of fair value, the Company identifies events and circumstances which 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. The Company then weighs these factors to determine and conclude if it is not more likely than not the IPR&D asset is impaired. If it is more likely than not the IPR&D asset is impaired, the Company proceeds with quantitatively determining the fair value of the IPR&D asset. When performing the quantitative impairment test, the Company uses the income approach to determine the fair value of its 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 judgmental 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 size of the patient population and cure rate, our competitive position in the marketplace, and appropriate discount and tax rates. Any impairment to be recorded is calculated as the difference between the estimated fair value and the carrying value of the IPR&D asset on the Company’s consolidated balance sheet.
Leases	Leases All of the Company’s leases are operating leases for facilities and equipment. The Company recognizes a lease asset for its right to use the underlying asset and a lease liability for the corresponding lease obligation. The Company determines whether an arrangement is or contains a lease at contract inception. Operating leases with a duration greater than one year are included in operating lease right-of-use assets, operating lease liabilities - short-term, and operating lease liabilities - long-term in the Company’s consolidated balance sheets. Operating lease right-of-use assets and liabilities are recognized at the lease commencement date based on the present value of lease payments over the lease term. In determining the net present value of lease payments, the Company uses its incremental borrowing rate based on the information available at the lease commencement date. The incremental borrowing rate represents the interest rate the Company would incur at lease commencement to borrow an amount equal to the lease payments on a collateralized basis over the term of a lease. The Company considers a lease term to be the noncancelable period that it has the right to use the underlying asset, including any periods where it is reasonably assured the Company will exercise the option to extend the contract. Periods covered by an option to extend are included in the lease term if the lessor controls the exercise of that option. The operating lease right-of-use assets also include any lease payments made and exclude lease incentives. Lease expense is recognized on a straight-line basis over the expected lease term. Variable lease expenses are recorded when incurred. The Company has elected not to separate lease and non-lease components for its leased assets and accounts for all lease and non-lease components of its agreements as a single lease component.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets The Company monitors the carrying value of long-lived assets, including ROU operating lease assets, for potential impairment and tests the recoverability of such assets whenever events or changes in circumstances indicate that the carrying amounts may not be recoverable. If a change in circumstance occurs, the Company performs a test of recoverability by comparing the carrying value of the asset or asset group to its undiscounted expected future cash flows. If cash flows cannot be separately and independently identified for a single asset, the Company will determine whether impairment has occurred for the group of assets for which the Company can identify the projected cash flows. If the carrying values are in excess of undiscounted expected future cash flows, the Company measures any impairment by comparing the fair value of the asset or asset group to its carrying value. In conjunction with the decision to wind down the Microbiome program in December 2020, the Company evaluated its ROU assets and property and equipment used in the Microbiome program for impairment. The Company determined the carrying value was no longer recoverable and, based on the fair value of the assets determined from market quotes, recorded an impairment loss of $0.7 million included in research and development expenses in 2020. There were no indicators of impairment of long-lived assets during the year ended
Property and Equipment, Net	Property and Equipment, Net Property and equipment are stated at cost and consist of lab and office equipment, leasehold improvements and computer hardware and software. The Company records depreciation under the straight-line method over the estimated useful lives of its property and equipment ranging from three to seven years. Leasehold improvements are amortized over the remaining terms of the respective leases or the estimated useful life of the leasehold improvements, whichever is less. Maintenance and repair costs are expensed as incurred.
Fair Value Measurements	Fair Value Measurements The Company follows accounting guidance on fair value measurements for financial instruments measured on a recurring basis, as well as for certain assets and liabilities that are initially recorded at their estimated fair values. Fair value is defined as the exit price, or the amount that would be received from selling an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. The Company uses the following three-level hierarchy that maximizes the use of observable inputs and minimizes the use of unobservable inputs to value its financial instruments: Level 1: Observable inputs such as unadjusted quoted prices in active markets for identical instruments. Level 2: Quoted prices for similar instruments that are directly or indirectly observable in the marketplace. Level 3: Significant unobservable inputs which are supported by little or no market activity and that are financial instruments whose values are determined using pricing models, discounted cash flow methodologies, or similar techniques, as well as instruments for which the determination of fair value requires significant judgment or estimation. Financial instruments measured at fair value are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. The assessment of the significance of a particular input to the fair value measurement in its entirety requires the Company to make judgments and consider factors specific to the asset or liability. The use of different assumptions and/or estimation methodologies may have a material effect on estimated fair values. Accordingly, the fair value estimates disclosed or initial amounts recorded may not be indicative of the amount the Company or holders of the instruments could realize in a current market exchange. The carrying amounts of cash equivalents and marketable securities approximate their fair value based upon quoted market prices. Certain of the Company’s financial instruments are not measured at fair value on a recurring basis but are recorded at amounts which approximate their fair value due to their liquid or short-term nature, such as cash, accounts receivable, accounts payable and accrued expenses. The following tables present the fair value of the Company’s financial assets measured at fair value on a recurring basis using the above input categories (in thousands): December 31, 2021 Level 1 Level 2 Level 3 Fair Value Cash equivalents Money market fund $ 42,507 $ — $ — $ 42,507 Total cash equivalents 42,507 — — 42,507 Short-term marketable securities U.S. and foreign corporate debt securities — 7,013 — 7,013 Asset-backed securities — 29,059 — 29,059 U.S. and foreign commercial paper — 64,928 — 64,928 Total short-term marketable securities — 101,000 — 101,000 Long-term marketable securities U.S. and foreign corporate debt securities — 19,043 — 19,043 U.S. treasury securities — 8,929 — 8,929 Total long-term marketable securities — 27,972 — 27,972 Total assets measured at fair value $ 42,507 $ 128,972 $ — $ 171,479 December 31, 2020 Level 1 Level 2 Level 3 Fair Value Cash equivalents Money market fund $ 47,553 $ — $ — $ 47,553 U.S. and foreign commercial paper — 6,498 — 6,498 Total cash equivalents 47,553 6,498 — 54,051 Short-term marketable securities U.S. and foreign corporate debt securities — 16,939 — 16,939 Asset-backed securities — 12,675 — 12,675 U.S. treasury securities — 23,999 — 23,999 U.S. and foreign commercial paper — 103,356 — 103,356 Total short-term marketable securities — 156,969 — 156,969 Total assets measured at fair value $ 47,553 $ 163,467 $ — $ 211,020 Money market funds are highly liquid and actively traded marketable securities that generally transact at a stable $1.00 net asset value representing its estimated fair value. The Company estimates the fair value of its U.S. and foreign corporate debt securities, asset backed securities, U.S. treasury securities and U.S. and foreign commercial paper by taking into consideration valuations obtained from third-party pricing services. The pricing services utilize industry standard valuation models, including both income and market-based approaches, for which all significant inputs are observable, either directly or indirectly, to estimate fair value. These inputs include reported trades of and broker/dealer quotes on the same or similar securities, issuer credit spreads; benchmark securities; prepayment/default projections based on historical data; and other observable inputs. During the quarter ended December 31, 2021, there was a triggering event that required the Company to perform an impairment analysis for both its goodwill and indefinite-lived asset. As a result, the Company recognized an impairment charge of $41.6 million for its goodwill and indefinite-lived asset. The Company considers the fair value used to determine the impairment charge to be a Level 3 measurement. See additional discussion relating to the Company’s impairment of goodwill and indefinite-lived asset in Note 5. There have been no transfers between Level 1, Level 2 or Level 3 for any of the periods presented. See Note 3 for further information regarding the carrying value of the Company’s investments in marketable securities.
Revenue Recognition and Accounts Receivable from Collaborations	Revenue Recognition and Accounts Receivable from Collaborations The Company analyzes its 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, the Company considers 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 the Company’s consolidated statements of operations and comprehensive loss. Under certain collaborative arrangements, the Company has been reimbursed for a portion of its research and development expenses or participates 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 in the Company’s consolidated statements of operations and comprehensive loss, as the Company does not consider performing these activities for reimbursement to be a part of its 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 , the Company evaluates the term of the arrangement and recognizes revenue when the customer obtains control of promised goods or services in a contract for an amount that reflects the consideration the Company expects to receive in exchange for those goods or services. For contracts with customers, the Company applies 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 transa ction price to the performance obligations; and ( 5 ) recognition of revenue when (or as) the Company satisfies each performance obligation. The Company has provided standard indemnification and protection of licensed intellectual property for its customer. These provisions are part of assurance that the licenses meet the agreements, representations and are not obligations to provide goods or services. The Company only applies the five-step model to contracts when it is probable the Company will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. As part of the accounting for contracts with customers, the Company must develop assumptions that require judgment to determine the SSP of each performance obligation identified in the contract. The Company then allocates the total transaction price to each performance obligation based on the estimated standalone selling price (SSP) of each performance obligation. The Company recognizes 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 the Company’s intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, the Company recognizes 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, the Company utilizes 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, the Company applies an appropriate method of measuring progress for purposes of recognizing revenue from nonrefundable, upfront license fees. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. Development and Regulatory Milestone Payments Depending on facts and circumstances, the Company may record revenues from certain milestones in a reporting period before the milestone is achieved if the Company concludes achievement of the milestone is probable and recognition of revenue related to the milestone will not result in a significant reversal in amounts recognized in future periods. The Company records 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. The Company re-evaluates the probability of achievement of such milestones and any related constraint each reporting period. The Company adjusts its estimate of the overall transaction price, including the amount of collaborative revenue that was recorded, if necessary. Research and Development Service Payments Under the Research, Development, Collaboration and License Agreement (Allergan Agreement) with Allergan Pharmaceuticals International Limited (Allergan), the Company was reimbursed at a certain percentage for performing research and development services based on hours worked by the Company’s employees, at a fixed contractual rate per hour, and third-party pass-through costs the Company incurred on a quarterly basis. Research and development service payments were included in the transaction price in the reporting period the Company 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. The Company recorded the full reimbursed portion of these expenses as collaboration revenue associated with the Allergan Agreement in its consolidated statements of operations as the Company consider performing research and development services to be a part of its ongoing and central operations. Sales-based Milestone and Royalty Payment s The Company’s customer may be required to pay the Company sales-based milestone payments or royalties on future sales of commercial products. The Company recognizes revenues related to sales-based milestone and royalty payments upon the later to occur of (i) achievement of the collaborator’s underlying sales or (ii) satisfaction of any performance obligation(s) related to these sales, in each case assuming the Company’s licensed intellectual property is deemed to be the predominant item to which the sales-based milestones and/or royalties relate. The Company receives payments from its customer based on billing schedules established in the contract. Upfront payments and fees are recorded as deferred revenue upon receipt or when due until the Company performs its obligations under the arrangement. If the related performance obligation is expected to be satisfied within the next twelve months, these amounts will be classified in current liabilities. The Company recognizes a contract asset relating to its conditional right to consideration that is not subject to a constraint. Amounts are recorded as accounts receivable when the Company’s right to consideration is unconditional. A net contract asset or liability is presented for each contract with a customer. The Company does not assess whether a contract has a significant financing component if the expectation at contract inception is such that the period between payment by the customer and the transfer of the promised goods or services to the customer will be one year or less. At December 31, 2021 and 2020, all accounts receivable from collaborations are deemed collectible. Contract Liabilities The following tables present changes in the Company’s contract liabilities (in thousands): Balance at Beginning of Period Additions Deductions Balance at End of Period Year Ended December 31, 2021 Contract liabilities: Deferred revenue $ 8,987 $ — $ (6,254 ) $ 2,733 Year Ended December 31, 2020 Contract liabilities: Deferred revenue $ 37,048 $ 40,000 $ (68,061 ) $ 8,987 Year Ended December 31, 2021 2020 Collaboration revenue recognized in the period from Amounts included in deferred revenue at the beginning of the period $ 6,254 $ 37,048 Performance obligations satisfied in previous period — —
Stock-Based Compensation	Stock-Based Compensation The Company measures stock-based compensation to employees, consultants, Board members, and non-employees at fair value on the grant date of the award. The fair value of RSUs is determined based on the number of shares granted and the quoted market price of the Company’s common stock on the date of grant. Compensation cost is recognized as expense on a straight-line basis over the requisite service period of the award. Stock-based awards with graded vesting schedules are recognized using the accelerated attribution method on a straight-line basis over the requisite service period for each separately vesting portion of the award. For awards that have a performance condition, compensation cost is measured based on the fair value of the award on the grant date, the date performance targets are established, and is expensed over the requisite service period for each separately vesting tranche when achievement of the performance condition becomes probable. The Company assesses the probability of the performance conditions being met on a continuous basis. Forfeitures are recognized when they occur. The Company estimates the fair value of stock option grants that do not contain market-based vesting conditions using the Black-Scholes option pricing model . T he assumptions used in estimating the fair value of these awards, such as expected term, expected dividend yield , volatility and risk-free interest rate, represent management’s best estimates and involve inherent uncertainties and the application of management’s judgment. The Company is also required to make estimates as to the probability of achieving the specific performance conditions. If actual results are not consistent with the Company’s assumptions and judgments used in making these estimates, the Company may be required to increase or decrease compensation expense, which could be material to the Company’s consolidated results of operations.
Research and Development Expense and Accruals	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 and research and development and costs incurred under the Company’s 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. The Company records expenses related to clinical studies and manufacturing development activities based on its estimates of the services received and efforts expended pursuant to contracts with multiple contract research organizations (CROs) and manufacturing vendors that conduct and manage these activities on its behalf. The financial terms of these agreements are subject to negotiation, vary from contract to contract, and may result in uneven payment flows. There may be instances in which payments made to the Company’s vendors will exceed the level of services provided and result in a prepayment of the expense. Payments under some of these contracts depend on factors such as the successful enrollment of subjects and the completion of clinical study milestones. In amortizing or accruing service fees, the Company estimates the time period over which services will be performed, enrollment of subjects, number of sites activated 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 the Company’s estimate, the Company will adjust the accrued or prepaid expense balance accordingly. To date, there have been no material differences from the Company’s estimates to the amounts actually incurred. The Company has entered and may continue to enter into license agreements to access and utilize certain technology. In each case, the Company evaluates if the license agreement results in the acquisition of an asset or a business. To date, none of the Company’s 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. The Company assesses whether such contingent consideration meets the definition of a derivative and to date the Company has determined that such contingent consideration are not derivatives.
Restructurings Charges	Restructuring Charges The Company recognizes restructuring charges related to reorganization plans that have been committed to by management and when liabilities have been incurred. In connection with these activities, the Company records 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 management has 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 the Company to make certain judgments and estimates regarding the nature, timing and amount of costs associated with the planned reorganization plan. To the extent the Company’s actual results differ from its estimates and assumptions, the Company 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 already recognized. Such changes to previously estimated amounts may be material to the consolidated financial statements. Changes in the estimates of the restructuring charges are recorded in the period the change is determined. At the end of each reporting period, the Company evaluates the remaining accrued restructuring balances to ensure that no excess accruals are retained, and the utilization of t he provisions are for their intended purpose in accordance with developed restructuring plans. For gains and losses on the derecognition of nonfinancial assets the Company determines if a contract exists, identifies the distinct non-financial assets, and determines when control transfers and, therefore, when to derecognize the asset. Additionally, the Company applies the measurement principles of revenue from contracts with customers within U.S. GAAP to determine the amount of consideration to include in the calculation of the gain or loss for the non-financial asset. Any gains or losses have been included within research and development expenses.
Variable Interest Entities	Variable Interest Entities The Company reviews agreements it enters into with third party entities, pursuant to which we may have a variable interest in the entity, in order to determine if the entity is a variable interest entity (VIE). If the entity is a VIE, the Company assesses whether or not it is the primary beneficiary of that entity. In determining whether the Company is the primary beneficiary of an entity, the Company applies a qualitative approach that determines whether it has both (1) the power to direct the economically significant activities of the entity and (2) the obligation to absorb losses of, or the right receive benefits from, the entity that could potentially be significant to that entity. If the Company were to determine it is the primary beneficiary of a VIE, the Company would consolidate the statements of operations and financial condition of the VIE into its consolidated financial statements. The Company’s determination about whether it should consolidate such VIEs is made continuously as changes to existing relationships or future transactions may result in a consolidation event. As of December 31, 2021, the Company did not consolidate any entities it had determined to be VIEs.
Income Taxes	Income Taxes The Company records income taxes using the asset and liability method. Deferred income tax assets and liabilities are recognized for the future tax effects attributable to temporary differences between the financial statement carrying amounts of existing assets and liabilities and their respective income tax bases, and operating loss and tax credit carryforwards. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period that includes the enactment date. The Company establishes a valuation allowance if it is more likely than not that the deferred tax assets will not be realized based on an evaluation of objective verifiable evidence. For tax positions that are more likely than not of being sustained upon audit, the Company recognizes the largest amount of the benefit that is greater than 50% likely of being realized. For tax positions that are not more likely than not of being sustained upon audit, the Company does not recognize any portion of the benefit. The Company recognizes and measures uncertain tax positions using a two-step approach set forth in authoritative guidance. The first step is to evaluate the tax position taken or expected to be taken by determining whether the weight of available evidence indicates that it is more likely than not that the tax position will be sustained in an audit, including resolution of any related appeals or litigation processes. The second step is to measure the tax benefit as the largest amount that is more than 50% likely to be realized upon ultimate settlement. Significant judgment is required to evaluate uncertain tax positions. The Company evaluates uncertain tax positions on a regular basis. The evaluations are based on a number of factors, including changes in facts and circumstances, changes in tax law, correspondence with tax authorities during the course of the audit, and effective settlement of audit issues. The provision for income taxes includes the effects of any accruals which the Company believes are appropriate. It is the Company’s policy to recognize interest and penalties related to income tax matters in income tax expense. No interest or penalties related to uncertain tax positions has been incurred or accrued for any periods presented . In March 2020, the Families First Coronavirus Response Act (FFCR Act) and the Coronavirus Aid, Relief, and Economic Security Act (CARES Act) were each enacted in response to the COVID-19 pandemic. The FFCR Act and the CARES Act contain numerous income tax provisions relating to refundable payroll tax credits, deferment of employer side social security payments, net operating loss carryback periods, alternative minimum tax credit refunds, modifications to the net interest deduction limitations and technical corrections to tax depreciation methods for qualified improvement property. In June 2020, Assembly Bill 85 (A.B. 85) was signed into California law. A.B. 85 provides for a three-year suspension of the use of net operating losses for medium and large businesses and a three-year cap on the use of business incentive tax credits to offset no more than $5.0 million of tax per year. A.B. 85 suspends the use of net operating losses for taxable years 2020, 2021 and 2022 for certain taxpayers with taxable income of $1.0 million or more. The carryover period for any net operating losses that are suspended under this provision will be extended. A.B. 85 also requires that business incentive tax credits including carryovers may not reduce the applicable tax by more than $5.0 million for taxable years 2020, 2021 and 2022. On February 9, 2022, Senate Bill No. 113 was enacted that removed the limitations on the use of NOLs and the cap on the business incentive tax credits that were suspended in accordance with AB 85 effective for tax year 2022. In December 2020, the Consolidated Appropriations Act, 2021 (CAA) was signed into law. The CAA included additional funding through tax credits as part of its economic package for 2021. In March 2021, the American Rescue Plan (H.R. 1319) was signed into law. This legislation extends and enhances a number of current-law tax incentives for businesses, but also expands the definition of a “covered employee” as defined by Section 162(m)(1) of the Internal Revenue Code. The FFCR Act, CARES Act, A.B. 85, CAA and H.R. 1319 did not have a material impact on the Company’s consolidated financial statements.
Net Loss per Share	Net Loss per Share Basic net loss per common share excludes dilution and is computed by dividing net loss by the weighted average number of common shares outstanding during the period. Diluted net loss per common share reflects the potential dilution that could occur if securities or other contracts to issue common stock were exercised or converted into common stock or resulted in the issuance of common stock that then shared in the earnings of the entity unless inclusion of such shares would be anti-dilutive. Since the Company has only incurred losses, basic and diluted net loss per share is the same. The Company had pre-funded warrants to purchase up to 2,424,242 shares of common stock outstanding as of December 31, 2020. All 2,424,242 of the pre-funded warrants were exercised through a cashless exercise A reconciliation of the numerators and the denominators of the basic and diluted net loss per common share computations is as follows (in thousands, except per share amounts): Year Ended December 31, 2021 2020 Numerator: Net loss $ (129,855 ) $ (62,152 ) Denominator: Weighted average common shares and pre-funded warrants outstanding - basic and diluted 43,280,383 35,427,120 Net loss per share - basic and diluted $ (3.00 ) $ (1.75 ) Securities excluded from the computation of diluted loss from per share because including them would have been antidilutive are as follows: Year Ended December 31, 2021 2020 Options to purchase common stock 6,161,901 6,696,592 Common stock subject to purchase under our ESPP 78,740 44,223 Unvested RSUs 970,339 746,868 Total 7,210,980 7,487,683
Comprehensive Loss	Comprehensive Loss Comprehensive loss is comprised of net loss and adjustments for the change in unrealized gains and losses on investments in available-for-sale marketable securities. The Company displays comprehensive loss and its components in the consolidated statements of operations and comprehensive loss, net of tax effects if any.
Concentrations of Risk	Concentrations of Risk Credit Risk Financial instruments which potentially subject the Company to credit risk consist primarily of cash, cash equivalents and marketable securities. The Company holds these investments in highly rated financial institutions, and, by policy, limits the amounts of credit exposure to any one financial institution. These amounts at times may exceed federally insured limits. The Company has not experienced any credit losses in such accounts and does not believe it is exposed to any significant credit risk on these funds. The Company has no off-balance sheet concentrations of credit risk, such as foreign currency exchange contracts, option contracts or other hedging arrangements. Supplier Risk Certain materials and key components the Company utilizes in its operations are obtained through single suppliers. Since the suppliers of key components and materials must be named in a New Drug Application (NDA) filed with the FDA for a product
Adoption of Recent Accounting Pronouncements	Adoption of Recent Accounting Pronouncements On January 1, 2021, the Company adopted Accounting Standards Update (ASU) 2020-10, Codification Improvements – Disclosures The adoption of this standard had no material impact on the Company’s consolidated financial statements and related disclosures. Accounting Pronouncements to Be Adopted In June 2016, the Financial Accounting Standards Board (the FASB) issued ASU 2016-13, Financial Instruments – Credit Losses: Measurement of Credit Losses on Financial Instruments Financial Instruments – Credit Losses (Topic 326) , Derivatives and Hedging (Topic 815) , and Leases (Topic 842): Effective Dates , The Company is currently evaluating the timing and impact of adopting ASU 2016-13 on its consolidated financial statements and related disclosures. In August 2020, the FASB issued ASU 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40): Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity (ASU 2020-06), which simplifies the accounting for certain financial instruments with characteristics of liabilities and equity, including convertible instruments and contracts on an entity’s own equity. Specifically, ASU 2020-06 simplifies accounting for convertible instruments by removing major separation models in ASC 470-20 that require separate accounting for embedded conversion features. ASU 2020-06 also removes certain settlement conditions in ASC 815-40 that are required for equity contracts to qualify for the derivative scope exception, which will permit more equity contracts to qualify for the scope exception and simplifies the diluted earnings per share calculation in certain areas. ASU 2020-06 is effective for interim and annual periods beginning after December 15, 2021, with early adoption permitted. Adoption of ASU 2020-06 can either be on a modified retrospective or full retrospective basis. The Company does not expect ASU 2020-06 to have a material impact on its consolidated financial statements and related disclosures. In May 2021, the FASB issued ASU 2021-04, Issuer's Accounting for Certain Modifications or Exchanges of Freestanding Equity-Classified Written Call Options

Summary of Significant Accoun_3

Summary of Significant Accounting Policies and Recent Accounting Pronouncements (Tables)	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Schedule of Fair Value of Financial Assets	The following tables present the fair value of the Company’s financial assets measured at fair value on a recurring basis using the above input categories (in thousands): December 31, 2021 Level 1 Level 2 Level 3 Fair Value Cash equivalents Money market fund $ 42,507 $ — $ — $ 42,507 Total cash equivalents 42,507 — — 42,507 Short-term marketable securities U.S. and foreign corporate debt securities — 7,013 — 7,013 Asset-backed securities — 29,059 — 29,059 U.S. and foreign commercial paper — 64,928 — 64,928 Total short-term marketable securities — 101,000 — 101,000 Long-term marketable securities U.S. and foreign corporate debt securities — 19,043 — 19,043 U.S. treasury securities — 8,929 — 8,929 Total long-term marketable securities — 27,972 — 27,972 Total assets measured at fair value $ 42,507 $ 128,972 $ — $ 171,479 December 31, 2020 Level 1 Level 2 Level 3 Fair Value Cash equivalents Money market fund $ 47,553 $ — $ — $ 47,553 U.S. and foreign commercial paper — 6,498 — 6,498 Total cash equivalents 47,553 6,498 — 54,051 Short-term marketable securities U.S. and foreign corporate debt securities — 16,939 — 16,939 Asset-backed securities — 12,675 — 12,675 U.S. treasury securities — 23,999 — 23,999 U.S. and foreign commercial paper — 103,356 — 103,356 Total short-term marketable securities — 156,969 — 156,969 Total assets measured at fair value $ 47,553 $ 163,467 $ — $ 211,020
Schedule of Changes in Contract Liabilities	The following tables present changes in the Company’s contract liabilities (in thousands): Balance at Beginning of Period Additions Deductions Balance at End of Period Year Ended December 31, 2021 Contract liabilities: Deferred revenue $ 8,987 $ — $ (6,254 ) $ 2,733 Year Ended December 31, 2020 Contract liabilities: Deferred revenue $ 37,048 $ 40,000 $ (68,061 ) $ 8,987
Schedule of Collaboration Revenue Recognized with the Period	Year Ended December 31, 2021 2020 Collaboration revenue recognized in the period from Amounts included in deferred revenue at the beginning of the period $ 6,254 $ 37,048 Performance obligations satisfied in previous period — —
Schedule of Earnings Per Share, Basic and Diluted	A reconciliation of the numerators and the denominators of the basic and diluted net loss per common share computations is as follows (in thousands, except per share amounts): Year Ended December 31, 2021 2020 Numerator: Net loss $ (129,855 ) $ (62,152 ) Denominator: Weighted average common shares and pre-funded warrants outstanding - basic and diluted 43,280,383 35,427,120 Net loss per share - basic and diluted $ (3.00 ) $ (1.75 )
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	Securities excluded from the computation of diluted loss from per share because including them would have been antidilutive are as follows: Year Ended December 31, 2021 2020 Options to purchase common stock 6,161,901 6,696,592 Common stock subject to purchase under our ESPP 78,740 44,223 Unvested RSUs 970,339 746,868 Total 7,210,980 7,487,683

Investments in Marketable Sec_2

Investments in Marketable Securities (Tables)	12 Months Ended
	Dec. 31, 2021
Investments Debt And Equity Securities [Abstract]
Schedule of Investments in Marketable Available-for-Sale Securities	Investments in marketable available-for-sale securities consisted of the following (in thousands): December 31, 2021 Amortized Cost Gross Unrealized Gain Gross Unrealized Loss Fair Value Cash equivalents Money market funds $ 42,507 $ — $ — $ 42,507 Total cash equivalents 42,507 — — 42,507 Short-term marketable securities U.S. and foreign corporate debt securities 7,015 — (2 ) 7,013 Asset-backed securities 29,097 — (38 ) 29,059 U.S. and foreign commercial paper 64,929 — (1 ) 64,928 Total short-term marketable securities 101,041 — (41 ) 101,000 Long-term marketable securities U.S. and foreign corporate debt securities 19,117 — (74 ) 19,043 U.S. treasury securities 8,960 — (31 ) 8,929 Total long-term marketable securities 28,077 — (105 ) 27,972 Total cash equivalents and marketable securities $ 171,625 $ — $ (146 ) $ 171,479 December 31, 2020 Amortized Cost Gross Unrealized Gain Gross Unrealized Loss Fair Value Cash equivalents Money market funds $ 47,553 $ — $ — $ 47,553 U.S. and foreign commercial paper 6,498 — — 6,498 Total cash equivalents 54,051 — — 54,051 Short-term marketable securities U.S. and foreign corporate debt securities 16,939 3 (3 ) 16,939 Asset-backed securities 12,674 2 (1 ) 12,675 U.S. treasury securities 23,997 2 — 23,999 U.S. and foreign commercial paper 103,356 — — 103,356 Total short-term marketable securities 156,966 7 (4 ) 156,969 Total cash equivalents and marketable securities $ 211,017 $ 7 $ (4 ) $ 211,020

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	12 Months Ended
	Dec. 31, 2021
Property Plant And Equipment [Abstract]
Schedule of Property and Equipment, Net	Property and equipment, net consists of the following (in thousands): December 31, 2021 2020 Lab equipment 18 247 Office equipment 699 699 Leasehold improvement 1,629 2,490 Total property and equipment 2,346 3,436 Less: Accumulated depreciation (1,207 ) (1,836 ) Property and equipment, net $ 1,139 $ 1,600

Other Accrued Expenses (Tables)

Other Accrued Expenses (Tables)	12 Months Ended
	Dec. 31, 2021
Payables And Accruals [Abstract]
Schedule of Other Accrued Expenses	Other accrued expenses consist of the following (in thousands): December 31, 2021 2020 Accrued expenses: Accrued compensation $ 6,426 $ 7,016 Accrued restructuring charges — 4,164 Accrued professional fees and other 437 807 Total accrued expenses $ 6,863 $ 11,987

Restructurings (Tables)

Restructurings (Tables)	12 Months Ended
	Dec. 31, 2021
Restructuring And Related Activities [Abstract]
Summary of Restructuring Costs	The following table summarizes the Company’s costs incurred (in thousands): Total Restructuring Cost Employee Severance and Related Benefits Asset Impairment and Other Costs Cumulative restructuring costs incurred through December 31, 2021 $ 6,430 $ 3,240 $ 3,190 Restructuring costs incurred for the year ended December 31, 2021 $ (1,348 ) $ (2,959 ) (1) $ 1,611 Restructuring costs incurred for the year ended December 31, 2020 $ 5,684 $ 4,105 $ 1,579 (1)
Schedule of Restructuring Charges	The following table presents where the restructuring charges were recognized (in thousands): Year Ended December 31, 2021 2020 Research and development $ (1,625 ) $ 5,486 General and administrative 277 $ 198 Total $ (1,348 ) $ 5,684
Schedule of Accrued Restructuring Charges	The following table presents the activity in the accrued restructuring charges during the period (in thousands): Total Restructuring Cost Employee Severance and Related Benefits Asset Impairment and Other Costs Accrued balance as of December 31, 2019 $ 2,094 $ 2,094 $ — Costs incurred 3,843 3,843 — Reductions for cash payments (1,773 ) (1,773 ) — Accrued balance as of December 31, 2020 $ 4,164 $ 4,164 $ — Costs incurred 1,611 — 1,611 Reductions for cash payments (5,775 ) (4,164 ) (1,611 ) (1) Accrued balance as of December 31, 2021 $ — $ — $ — (1)

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2021
Equity [Abstract]
Summary of Warrants to Purchase Shares of Company's Common Stock	T he following warrants to purchase shares of the Company’s common stock were issued and outstanding: Issue date Expiration date Exercise Price per Share As of December 31, 2021 As of December 31, 2020 December 16, 2019 None $ 0.001 — 2,424,242

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Stock Option Activity and Related Information	The following table summarizes the stock option activity and related information for 2021: Number of Shares Weighted Average Exercise Price Per Share Weighted Average Remaining Contractual Term (Years) Total Intrinsic Value (in thousands) Outstanding as of December 31, 2020 6,696,592 $ 15.70 6.9 $ 1,856 Granted 1,521,370 4.24 Forfeited (2,046,861 ) 18.93 Expired (9,200 ) 30.00 Outstanding as of December 31, 2021 6,161,901 $ 11.77 6.4 $ 53 Options vested and exercisable as of December 31, 2021 3,805,841 $ 13.53 5.0 $ 51
Summary of Restricted Stock Units and Related Information	The following table summarizes RSU activity and related information for 2021: Number of RSUs Weighted Average Fair Value Per RSU at Grant Price Nonvested as of December 31, 2020 886,868 $ 20.36 Granted 721,341 3.78 Vested (347,096 ) 27.97 Forfeited (290,774 ) 14.64 Nonvested as of December 31, 2021 970,339 $ 7.04
Summary of Assumptions Used to Estimate Fair Values of Stock Options Grants	A summary of the assumptions used to estimate the fair values of stock options grants for the years presented is as follows: Year Ended December 31, 2021 2020 Exercise price $2.24 - $5.79 $5.62 - $23.30 Expected volatility 79.7% - 91.2% 66.4% - 92.3% Risk-free rate 0.50% - 1.37% 0.26% - 1.44% Expected term (years) 5.5 - 7.5 5.5 - 7.5 Expected dividend yield 0% 0%
Schedule of Recognized Stock-Based Compensation Expense	The Company recognized stock-based compensation expense included in the consolidated statement of operations and comprehensive loss for the years presented (in thousands): Year Ended December 31, 2021 2020 Research and development $ 548 $ 11,380 General and administrative 4,689 10,473 Total stock-based compensation expense $ 5,237 $ 21,853

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Schedule of Deferred Income Tax Benefit	Income tax benefit is as follows (in thousands): As of December 31, 2021 2020 Federal: Current — — Deferred 1,160 — $ 1,160 $ — State: Current — — Deferred 1,371 — $ 1,371 $ — Income tax benefit $ 2,531 $ —
Effective Income Tax Rate of Provision for Income Taxes	The effective tax rate of our provision for income taxes differs from the federal statutory rate as follows: As of December 31, 2021 2020 Statutory federal income tax rate 21.0 % 21.0 % State taxes, net of federal tax benefit 5.8 6.1 Research and development tax credits 2.3 2.2 Return to provision adjustments (0.2 ) 4.3 Other (0.6 ) 0.1 Uncertain tax positions (0.5 ) 2.2 Impairment of goodwill (2.0 ) — Stock-based compensation (4.5 ) 0.7 Change in valuation allowance (19.4 ) (36.6 ) Income taxes benefit 1.9 % 0.0 %
Components of Deferred Taxes	Significant components of the Company’s deferred taxes are as follows (in thousands): As of December 31, 2021 2020 Deferred tax assets: Federal and state-operating loss carryforwards $ 133,671 $ 108,236 Stock-based compensation 11,082 16,563 Operating lease liabilities 1,656 2,600 Research and development credits 11,106 8,872 Other 1,125 2,317 Total deferred tax assets 158,640 138,588 Valuation allowance (157,095 ) (131,332 ) Deferred tax asset, net of valuation allowance $ 1,545 $ 7,256 Deferred tax liabilities: In-process research and development $ — $ (7,443 ) Operating lease right-of-use assets (1,545 ) (2,344 ) Total deferred tax liabilities (1,545 ) (9,787 ) Net deferred tax liability $ — $ (2,531 )
Summary of Net Operating Loss and Tax Credit Carryforwards	Net operating loss and tax credit carryforwards as of December 31, 2021 are as follows (in thousands): Amount Expiration Years Net operating losses, federal (post December 31, 2017) $ 346,847 Indefinite Net operating losses, federal (pre January 1, 2018) 123,552 2027 - 2037 Net operating loss, state (Indefinite) 880 Indefinite Net operating loss, state (Definite) 545,256 2031 - 2041 Research and development tax credits, federal 10,845 2028 - 2041 Research and development tax credits, state 4,174 Indefinite
Activity Related to Gross Unrecognized Tax Benefits	The following table summarizes activity related to the Company’s gross unrecognized tax benefits (in thousands): As of December 31, 2021 2020 Balances as of beginning of year $ 2,655 $ 6,070 Increases related to prior year tax positions 1 — Decreases related to prior year tax positions (82 ) (4,162 ) Increases related to current year tax positions 663 747 Balances as of end of year $ 3,237 $ 2,655

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2021
Lease Cost [Abstract]
Schedule of Quantitative Information of Operating Leases	The following summarizes quantitative information about the Company’s operating leases (in thousands): Year Ended December 31, 2021 2020 Lease cost Operating lease cost $ 3,840 $ 5,214 Short-term lease cost 268 401 Variable lease cost 1,317 1,468 Sublease income (142 ) — Total lease cost, net $ 5,283 $ 7,083 Year Ended December 31, 2021 2020 Operating cash flows from operating leases $ 3,786 $ 4,513 ROU assets exchanged for new operating lease liabilities $ 126 $ 1,302
Schedule of Maturities Operating Lease Liabilities	As of December 31, 2021, the maturities of the Company’s operating lease liabilities were as follows (in thousands): 2022 3,643 2023 3,491 2024 10 Total 7,144 Less: present value discount (668 ) Operating lease liabilities $ 6,476

Nature of Business - Additional

Nature of Business - Additional Information (Details)	12 Months Ended
	Dec. 31, 2021segmentproduct
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Operating segments (in segments) | segment	1
FDA approved products (in products) | product	0

Summary of Significant Accoun_4

Summary of Significant Accounting Policies and Recent Accounting Pronouncements - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Impairment loss	$ 0	$ 700,000
Impairment charges of goodwill and indefinite-lived assets	41,638,000	0
Fair value assets transfers between level 1, level 2 or level 3	0	0
Uncertain tax positions, income tax interest or penalties incurred	0	0
Uncertain tax positions, income tax interest or penalties accrued	$ 0	$ 0
Number of pre-funded warrants sold to purchase of common stock	2,423,634
ASU 2020-10
Change in Accounting Principle, Accounting Standards Update, Adoption Date	Jan. 1, 2021
Change in Accounting Principle, Accounting Standards Update, Adopted [true false]	true
Change in Accounting Principle, Accounting Standards Update, Immaterial Effect [true false]	true
Public Offering
Number of pre-funded warrants to purchase shares of common stock outstanding		2,424,242
Number of pre-funded warrants sold to purchase of common stock	2,424,242		2,424,242
Pre-funded warrants exercisable price per share	$ 0.001		$ 0.001
Maximum
Estimated useful lives of property and equipment	7 years
Minimum
Estimated useful lives of property and equipment	3 years

Summary of Significant Accoun_5

Summary of Significant Accounting Policies and Recent Accounting Pronouncements - Schedule of Fair Value of Financial Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Short-term marketable securities
Short-term marketable securities	$ 101,000	$ 156,969
Long-term marketable securities
Long-term marketable securities	27,972
Recurring
Cash equivalents
Total cash equivalents	42,507	54,051
Short-term marketable securities
Short-term marketable securities	101,000	156,969
Long-term marketable securities
Long-term marketable securities	27,972
Total assets measured at fair value	171,479	211,020
Recurring | U.S. and foreign commercial paper
Cash equivalents
Total cash equivalents		6,498
Short-term marketable securities
Short-term marketable securities	64,928	103,356
Recurring | U.S and foreign corporate debt securities
Short-term marketable securities
Short-term marketable securities	7,013	16,939
Long-term marketable securities
Long-term marketable securities	19,043
Recurring | Asset-backed securities
Short-term marketable securities
Short-term marketable securities	29,059	12,675
Recurring | U.S. treasury securities
Short-term marketable securities
Short-term marketable securities		23,999
Long-term marketable securities
Long-term marketable securities	8,929
Recurring | Money market fund
Cash equivalents
Total cash equivalents	42,507	47,553
Recurring | Level 1
Cash equivalents
Total cash equivalents	42,507	47,553
Short-term marketable securities
Short-term marketable securities	0	0
Long-term marketable securities
Long-term marketable securities	0
Total assets measured at fair value	42,507	47,553
Recurring | Level 1 | U.S. and foreign commercial paper
Cash equivalents
Total cash equivalents		0
Short-term marketable securities
Short-term marketable securities	0	0
Recurring | Level 1 | U.S and foreign corporate debt securities
Short-term marketable securities
Short-term marketable securities	0	0
Long-term marketable securities
Long-term marketable securities	0
Recurring | Level 1 | Asset-backed securities
Short-term marketable securities
Short-term marketable securities	0	0
Recurring | Level 1 | U.S. treasury securities
Short-term marketable securities
Short-term marketable securities		0
Long-term marketable securities
Long-term marketable securities	0
Recurring | Level 1 | Money market fund
Cash equivalents
Total cash equivalents	42,507	47,553
Recurring | Level 2
Cash equivalents
Total cash equivalents	0	6,498
Short-term marketable securities
Short-term marketable securities	101,000	156,969
Long-term marketable securities
Long-term marketable securities	27,972
Total assets measured at fair value	128,972	163,467
Recurring | Level 2 | U.S. and foreign commercial paper
Cash equivalents
Total cash equivalents		6,498
Short-term marketable securities
Short-term marketable securities	64,928	103,356
Recurring | Level 2 | U.S and foreign corporate debt securities
Short-term marketable securities
Short-term marketable securities	7,013	16,939
Long-term marketable securities
Long-term marketable securities	19,043
Recurring | Level 2 | Asset-backed securities
Short-term marketable securities
Short-term marketable securities	29,059	12,675
Recurring | Level 2 | U.S. treasury securities
Short-term marketable securities
Short-term marketable securities		23,999
Long-term marketable securities
Long-term marketable securities	8,929
Recurring | Level 2 | Money market fund
Cash equivalents
Total cash equivalents	0	0
Recurring | Level 3
Cash equivalents
Total cash equivalents	0	0
Short-term marketable securities
Short-term marketable securities	0	0
Long-term marketable securities
Long-term marketable securities	0
Total assets measured at fair value	0	0
Recurring | Level 3 | U.S. and foreign commercial paper
Cash equivalents
Total cash equivalents		0
Short-term marketable securities
Short-term marketable securities	0	0
Recurring | Level 3 | U.S and foreign corporate debt securities
Short-term marketable securities
Short-term marketable securities	0	0
Long-term marketable securities
Long-term marketable securities	0
Recurring | Level 3 | Asset-backed securities
Short-term marketable securities
Short-term marketable securities	0	0
Recurring | Level 3 | U.S. treasury securities
Short-term marketable securities
Short-term marketable securities		0
Long-term marketable securities
Long-term marketable securities	0
Recurring | Level 3 | Money market fund
Cash equivalents
Total cash equivalents	$ 0	$ 0

Summary of Significant Accoun_6

Summary of Significant Accounting Policies and Recent Accounting Pronouncements - Schedule of Changes in Contract Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Accounting Policies [Abstract]
Balance at Beginning of Period	$ 8,987	$ 37,048
Additions	0	40,000
Deductions	(6,254)	(68,061)
Balance at End of Period	$ 2,733	$ 8,987

Summary of Significant Accoun_7

Summary of Significant Accounting Policies and Recent Accounting Pronouncements - Schedule of Collaboration Revenue Recognized with the Period (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Collaboration revenue recognized in the period from
Amounts included in deferred revenue at the beginning of the period	$ 6,254	$ 37,048
Performance obligations satisfied in previous period	$ 0	$ 0

Summary of Significant Accoun_8

Summary of Significant Accounting Policies and Recent Accounting Pronouncements - Schedule of Earnings Per Share, Basic and Diluted (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Numerator:
Net loss	$ (129,855)	$ (62,152)
Denominator:
Weighted average common shares outstanding, basic and diluted	43,280,383	35,427,120
Net loss per share, basic and diluted	$ (3)	$ (1.75)

Summary of Significant Accoun_9

Summary of Significant Accounting Policies and Recent Accounting Pronouncements - Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share (Details) - shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities excluded from computation of loss per share	7,210,980	7,487,683
Options
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities excluded from computation of loss per share	6,161,901	6,696,592
Common stock subject to purchase under ESPP
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities excluded from computation of loss per share	78,740	44,223
RSUs
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities excluded from computation of loss per share	970,339	746,868

Investments in Marketable Sec_3

Investments in Marketable Securities - Schedule of Investments in Marketable Available-for-Sale Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Investments in marketable securities:
Amortized Cost	$ 45,627	$ 59,444
Fair Value	101,000	156,969
Amortized Cost	171,625	211,017
Gross Unrealized Gain	0	7
Gross Unrealized Loss	(146)	(4)
Fair Value	171,479	211,020
Cash equivalents
Investments in marketable securities:
Amortized Cost	42,507	54,051
Gross Unrealized Gain	0	0
Gross Unrealized Loss	0	0
Fair Value	42,507	54,051
Cash equivalents | Money market fund
Investments in marketable securities:
Amortized Cost	42,507	47,553
Gross Unrealized Gain	0	0
Gross Unrealized Loss	0	0
Fair Value	42,507	47,553
Short-term marketable securities
Investments in marketable securities:
Amortized Cost	101,041	156,966
Gross Unrealized Gain	0	7
Gross Unrealized Loss	(41)	(4)
Fair Value	101,000	156,969
Long-term marketable securities
Investments in marketable securities:
Amortized Cost	28,077
Gross Unrealized Gain	0
Gross Unrealized Loss	(105)
Fair Value	27,972
U.S and foreign corporate debt securities | Short-term marketable securities
Investments in marketable securities:
Amortized Cost	7,015	16,939
Gross Unrealized Gain	0	3
Gross Unrealized Loss	(2)	(3)
Fair Value	7,013	16,939
U.S and foreign corporate debt securities | Long-term marketable securities
Investments in marketable securities:
Amortized Cost	19,117
Gross Unrealized Gain	0
Gross Unrealized Loss	(74)
Fair Value	19,043
Asset-backed securities | Short-term marketable securities
Investments in marketable securities:
Amortized Cost	29,097	12,674
Gross Unrealized Gain	0	2
Gross Unrealized Loss	(38)	(1)
Fair Value	29,059	12,675
U.S. and foreign commercial paper | Cash equivalents
Investments in marketable securities:
Amortized Cost		6,498
Gross Unrealized Gain		0
Gross Unrealized Loss		0
Fair Value		6,498
U.S. and foreign commercial paper | Short-term marketable securities
Investments in marketable securities:
Amortized Cost	64,929	103,356
Gross Unrealized Gain	0	0
Gross Unrealized Loss	(1)	0
Fair Value	64,928	103,356
U.S. treasury securities | Short-term marketable securities
Investments in marketable securities:
Amortized Cost		23,997
Gross Unrealized Gain		2
Gross Unrealized Loss		0
Fair Value		$ 23,999
U.S. treasury securities | Long-term marketable securities
Investments in marketable securities:
Amortized Cost	8,960
Gross Unrealized Gain	0
Gross Unrealized Loss	(31)
Fair Value	$ 8,929

Investments in Marketable Sec_4

Investments in Marketable Securities - Additional Information (Details)	Dec. 31, 2021
Maximum | Short-term marketable securities
Investments in marketable securities:
Available for sale securities maturity term	1 year
Maximum | Long-term marketable securities
Investments in marketable securities:
Available for sale securities maturity term	2 years
Minimum
Investments in marketable securities:
Available for sale securities maturity term	1 year

Property and Equipment, Net - S

Property and Equipment, Net - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Property, Plant and Equipment
Total property and equipment	$ 2,346	$ 3,436
Less: Accumulated depreciation	(1,207)	(1,836)
Property and equipment, net	1,139	1,600
Lab equipment
Property, Plant and Equipment
Total property and equipment	18	247
Office equipment
Property, Plant and Equipment
Total property and equipment	699	699
Leasehold improvement
Property, Plant and Equipment
Total property and equipment	$ 1,629	$ 2,490

Property and Equipment, Net - A

Property and Equipment, Net - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Property Plant And Equipment [Abstract]
Depreciation	$ 0.5	$ 0.7

Goodwill and Indefinite-Lived_2

Goodwill and Indefinite-Lived Intangible Assets Impairment - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill impairment charge	$ 12,600,000	$ 0
Indefinite-lived intangible assets impairment charges	$ 29,000,000	$ 0

Other Accrued Expenses - Schedu

Other Accrued Expenses - Schedule of Other Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Accrued expenses:
Accrued compensation	$ 6,426	$ 7,016
Accrued restructuring charges		4,164	$ 2,094
Accrued professional fees and other	437	807
Total accrued expenses	$ 6,863	$ 11,987

Restructurings - Summary of Res

Restructurings - Summary of Restructuring Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Restructuring Cost And Reserve [Line Items]
Cumulative restructuring costs incurred through December 31, 2021	$ 6,430
Restructuring costs incurred	(1,348)	$ 5,684
Employee Severance and Related Benefits
Restructuring Cost And Reserve [Line Items]
Cumulative restructuring costs incurred through December 31, 2021	3,240
Restructuring costs incurred	(2,959)	4,105
Asset Impairment and Other Costs
Restructuring Cost And Reserve [Line Items]
Cumulative restructuring costs incurred through December 31, 2021	3,190
Restructuring costs incurred	$ 1,611	$ 1,579

Restructurings - Summary of R_2

Restructurings - Summary of Restructuring Costs (Parenthetical) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Restructuring Cost And Reserve [Line Items]
Restructuring costs incurred	$ (1,348)	$ 5,684
Employee Severance and Related Benefits
Restructuring Cost And Reserve [Line Items]
Restructuring costs incurred	$ (2,959)	$ 4,105

Restructurings - Schedule of Re

Restructurings - Schedule of Restructuring Charges (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Restructuring Cost And Reserve [Line Items]
Restructuring charges	$ (1,348)	$ 5,684
Research and Development
Restructuring Cost And Reserve [Line Items]
Restructuring charges	(1,625)	5,486
General and Administrative
Restructuring Cost And Reserve [Line Items]
Restructuring charges	$ 277	$ 198

Restructurings - Schedule of Ac

Restructurings - Schedule of Accrued Restructuring Charges (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Restructuring Cost And Reserve [Line Items]
Accrued balance	$ 4,164	$ 2,094
Costs incurred	1,611	3,843
Reductions for cash payments	(5,775)	(1,773)
Accrued balance		4,164
Employee Severance and Related Benefits
Restructuring Cost And Reserve [Line Items]
Accrued balance	4,164	2,094
Costs incurred		3,843
Reductions for cash payments	(4,164)	(1,773)
Accrued balance		$ 4,164
Asset Impairment and Other Costs
Restructuring Cost And Reserve [Line Items]
Costs incurred	1,611
Reductions for cash payments	$ (1,611)

Restructurings - Schedule of _2

Restructurings - Schedule of Accrued Restructuring Charges (Parenthetical) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Restructuring And Related Activities [Abstract]
Proceeds from sale of property and equipment	$ 857	$ 0

Restructurings - Additional Inf

Restructurings - Additional Information (Details) - USD ($) $ in Millions	1 Months Ended		12 Months Ended
	Feb. 28, 2022	Dec. 31, 2021	Dec. 31, 2021
Microbiome Purchase Agreement
Restructuring Cost And Reserve [Line Items]
Consideration from asset purchase agreement, entitled to receive		$ 3
Consideration from asset purchase agreement		1.5
Gain on sale assets		3
Reduction in research and development expense		3
Microbiome Purchase Agreement | Prepaid Expenses and Other Current Assets
Restructuring Cost And Reserve [Line Items]
Consideration due		1.5	$ 1.5
Microbiome Purchase Agreement | Subsequent Event
Restructuring Cost And Reserve [Line Items]
Consideration from asset purchase agreement	$ 1.5
Microbiome Purchase Agreement | Regulatory
Restructuring Cost And Reserve [Line Items]
Potential milestone payments		$ 10
Asset Impairment and Other Costs
Restructuring Cost And Reserve [Line Items]
Costs incurred for remaining payment obligations of leased equipment			$ 1.4

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2021	Dec. 31, 2020	Aug. 31, 2020
Subsidiary Sale Of Stock [Line Items]
Preferred stock, shares authorized		5,000,000	5,000,000
Common stock, shares authorized		100,000,000	100,000,000
Preferred stock, shares issued		0	0
Preferred stock, shares outstanding		0	0
Initial public offering value of shares authorized				$ 300
Number of pre-funded warrants sold to purchase of common stock		2,423,634
Warrants exercisable description		their terms, the outstanding pre-funded warrants to purchase shares of the Company’s common stock generally may not be exercised if the holder’s ownership of the Company’s common stock would exceed 19.99% following such exercise.
Proceeds from sale of pre-funded warrants	$ 37.5
Number of pre-funded warrants exercised		2,424,242	0
Warrant to purchase of common stock			15,296
Maximum
Subsidiary Sale Of Stock [Line Items]
Initial public offering value of shares authorized				300
Ownership percentage to exercise warrant	19.99%
2020 At the Market Offerings
Subsidiary Sale Of Stock [Line Items]
Number of shares sold		11,234,207	892,840
Net proceeds from the issuance of common stock through equity plans		$ 52.8	$ 5.5
2020 At the Market Offerings | Maximum
Subsidiary Sale Of Stock [Line Items]
Initial public offering value of shares authorized				$ 100
Public Offering
Subsidiary Sale Of Stock [Line Items]
Net proceeds from the issuance of common stock through equity plans	$ 134.7
Number of shares sold	6,287,878
Sale of stock, price per share	$ 16.50
Number of pre-funded warrants sold to purchase of common stock	2,424,242	2,424,242
Sale of stock, price per warrant	$ 16.499
Pre-funded warrants exercisable price per share	$ 0.001	$ 0.001
Additional Shares Sold by Underwriters
Subsidiary Sale Of Stock [Line Items]
Number of shares sold	1,136,363

Stockholders' Equity - Summary

Stockholders' Equity - Summary of Warrants to Purchase Shares of Company's Common Stock (Details) - Warrants Issued on December 16, 2019 - $ / shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Subsidiary Sale Of Stock [Line Items]
Issue date	Dec. 16, 2019
Exercise Price per Share	$ 0.001
Number of warrants outstanding		2,424,242

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) - USD ($)	Jul. 31, 2021	Nov. 30, 2021	Jul. 31, 2021	May 31, 2021	Nov. 30, 2020	Jul. 31, 2020	May 31, 2020	Sep. 30, 2019	Mar. 31, 2021	Dec. 31, 2021	Dec. 31, 2020	Jun. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award
Shares reserved for issuance (in shares)				6,600,000								4,600,000
Weighted-average grant-date fair value of options granted										$ 3.05	$ 10.64
Total intrinsic value of options exercised										$ 0	$ 2,000,000
Stock-based compensation expense										5,237,000	21,853,000
Unrecognized stock-based compensation expense										$ 9,700,000
Unrecognized stock-based compensation expense expected to be recognized, term										1 year 7 months 6 days
Research and Development
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation expense										$ 548,000	11,380,000
General and Administrative
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation expense										4,689,000	10,473,000
Terminated Employees | Research and Development
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation expense										(4,800,000)
Terminated Employees | General and Administrative
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation expense										(2,100,000)
2018 ESPP
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation expense										$ 100,000	500,000
Maximum shares available for purchase by employees (in shares)										1,300,000
Number of common stock to be issued per offering										1,000
Maximum number of common stock to be issued per offering										2,500
Percentage of payroll deductions in ESPP										15.00%
Purchase price after discount (in percent)										85.00%
Number of common stock purchased by employees		46,017		42,803	44,546		42,266
Common stock, capital shares reserved for future issuance										1,043,515
RSUs
Share-based Compensation Arrangement by Share-based Payment Award
Total fair value of awards vested and settled										$ 3,700,000	7,800,000
Total intrinsic value of awards vested and settled										$ 1,400,000	$ 4,400,000
Number of awards vested and settled										347,096
Granted										721,341
Forfeited										290,774
Outstanding awards										970,339	886,868
RSUs | Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award
Granted						45,000		100,000
Forfeited	25,000								25,000
Outstanding awards										50,000
Total fair value of awards										$ 400,000
Stock-based compensation expense										$ 0
Cumulative catch-up adjustment of stock-based compensation expense											$ 700,000
RSUs | Employees Including Executive Officers
Share-based Compensation Arrangement by Share-based Payment Award
Granted			324,214
Total fair value of awards			$ 1,200,000
Stock-based compensation expense			$ 0
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award
Shares reserved for issuance (in shares)				1,300,000

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock Option Activity and Related Information (Details) - Options - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Number of Shares
Options, Outstanding at beginning of period	6,696,592
Option, Granted	1,521,370
Option, Forfeited	(2,046,861)
Option, Expired	(9,200)
Option, Outstanding at end of period	6,161,901	6,696,592
Options vested and exercisable	3,805,841
Weighted Average Exercise Price Per Share
Options, Outstanding at beginning of period	$ 15.70
Option, Granted	4.24
Option, Forfeited	18.93
Option, Expired	30
Option, Outstanding at end of period	11.77	$ 15.70
Options vested and exercisable	$ 13.53
Options Outstanding, Weighted Average Remaining Contractual Term (Years)	6 years 4 months 24 days	6 years 10 months 24 days
Options Vested and Exercisable, Weighted Average Remaining Contractual Term (Years)	5 years
Total Intrinsic Value
Option, Outstanding	$ 53	$ 1,856
Options vested and exercisable	$ 51

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summary of Restricted Stock Units and Related Information (Details) - RSUs	12 Months Ended
	Dec. 31, 2021$ / sharesshares
Number of Shares
Beginning of period | shares	886,868
Granted | shares	721,341
Vested | shares	(347,096)
Forfeited | shares	(290,774)
Ending of period | shares	970,339
Weighted Average Fair Value Per RSU at Grant Price
Beginning of period | $ / shares	$ 20.36
Granted | $ / shares	3.78
Vested | $ / shares	27.97
Forfeited | $ / shares	14.64
Ending of period | $ / shares	$ 7.04

Stock-Based Compensation - Su_3

Stock-Based Compensation - Summary of Assumptions Used to Estimate Fair Values of Stock Options Grants (Details) - $ / shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award
Expected dividend yield	0.00%	0.00%
Minimum
Share-based Compensation Arrangement by Share-based Payment Award
Exercise price	$ 2.24	$ 5.62
Expected volatility	79.70%	66.40%
Risk-free rate	0.50%	0.26%
Expected term (years)	5 years 6 months	5 years 6 months
Maximum
Share-based Compensation Arrangement by Share-based Payment Award
Exercise price	$ 5.79	$ 23.30
Expected volatility	91.20%	92.30%
Risk-free rate	1.37%	1.44%
Expected term (years)	7 years 6 months	7 years 6 months

Stock-Based Compensation - Sche

Stock-Based Compensation - Schedule of Recognized Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Compensation expense:
Stock-based compensation expense	$ 5,237	$ 21,853
Research and Development
Compensation expense:
Stock-based compensation expense	548	11,380
General and Administrative
Compensation expense:
Stock-based compensation expense	$ 4,689	$ 10,473

Collaboration Agreements - Addi

Collaboration Agreements - Additional Information (Details) - USD ($)	1 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2021	Dec. 31, 2020	Jul. 17, 2020	Dec. 31, 2019
Research And Development Arrangement Contract To Perform For Others [Line Items]
Collaboration revenue		$ 6,254,000	$ 79,105,000
Deferred revenue		2,733,000	8,987,000
Contract liability/deferred revenue		2,733,000	8,987,000		$ 37,048,000
Accounts receivable from collaboration		336,000	1,230,000
Contract with customer, liability, noncurrent		2,733,000	8,987,000
Research and development expense		68,524,000	106,823,000
Collaborative Arrangement
Research And Development Arrangement Contract To Perform For Others [Line Items]
Cost of reimbursable expenses			48,100,000
Collaboration revenue		0
Contract with customer, liability, current		0
Deferred revenue		0
Contract liability/deferred revenue			0
Accounts receivable from collaboration			1,000,000
Contract with customer, liability, noncurrent		0
BeiGene Agreement
Research And Development Arrangement Contract To Perform For Others [Line Items]
Collaboration revenue		6,300,000	31,000,000
Deferred revenue		2,700,000	9,000,000
Agreed to pay maximum amount development and regulatory costs		45,000,000
Upfront cash payment received		40,000,000
Contract with customer, liability, noncurrent		2,700,000	9,000,000
Research and development expense		0	0
Incremental costs			3,500,000
BeiGene Agreement | Other Assets
Research And Development Arrangement Contract To Perform For Others [Line Items]
Incremental costs		200,000	800,000
BeiGene Agreement | Maximum
Research And Development Arrangement Contract To Perform For Others [Line Items]
Potential milestone payments	$ 427,500,000	500,000,000
BeiGene Agreement | Development and Regulatory | Maximum
Research And Development Arrangement Contract To Perform For Others [Line Items]
Potential milestone payments	97,500,000	113,800,000
BeiGene Agreement | Sales Milestone Payments | Maximum
Research And Development Arrangement Contract To Perform For Others [Line Items]
Potential milestone payments	$ 330,000,000	385,000,000
Bei Gene Limited
Research And Development Arrangement Contract To Perform For Others [Line Items]
Contract liability/deferred revenue				$ 40,000,000
Arbutus Agreement
Research And Development Arrangement Contract To Perform For Others [Line Items]
Research and development expense		2,000,000	$ 200,000
Antios Agreement
Research And Development Arrangement Contract To Perform For Others [Line Items]
Costs incurred		$ 0

Milestones and Research Agree_2

Milestones and Research Agreements - Additional Information (Details) - USD ($)	1 Months Ended	12 Months Ended
	Nov. 30, 2020	Dec. 31, 2021	Dec. 31, 2020
Milestone and Research Agreements:
Potential milestone payment		$ 800,000
Sublicensing Fee			$ 700,000
Performance milestone payment			100,000
Payment of milestone		0
Accrued expenses		6,863,000	11,987,000
Microbiome Targeted Colonic Delivery Program
Milestone and Research Agreements:
Accrued expenses		0	0
Door Agreement
Milestone and Research Agreements:
Performance milestone payment		200,000
License agreement term	2 years
Up-front payment	$ 1,800,000
Research and development funding charges		$ 1,800,000	$ 300,000
Door Agreement | Maximum
Milestone and Research Agreements:
Success-based milestones	35,000,000
Exercise and annual fees	2,000,000
Door Agreement | Minimum
Milestone and Research Agreements:
Exercise and annual fees	$ 100,000

Income Taxes - Schedule of Defe

Income Taxes - Schedule of Deferred Income Tax Benefit (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Federal:
Current	$ 0	$ 0
Deferred	1,160	0
Federal, current and deferred income tax expense benefit	1,160	0
State:
Current	0	0
Deferred	1,371	0
State, current and deferred income tax expense benefit	1,371	0
Income tax benefit	$ 2,531	$ 0

Income Taxes - Effective Income

Income Taxes - Effective Income Tax Rate of Provision for Income Taxes (Details)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Statutory federal income tax rate	21.00%	21.00%
State taxes, net of federal tax benefit	5.80%	6.10%
Research and development tax credits	2.30%	2.20%
Return to provision adjustments	(0.20%)	4.30%
Other	(0.60%)	0.10%
Uncertain tax positions	(0.50%)	2.20%
Impairment of goodwill	(2.00%)	0.00%
Stock-based compensation	(4.50%)	0.70%
Change in valuation allowance	(19.40%)	(36.60%)
Income taxes benefit	1.90%	0.00%

Income Taxes - Components of De

Income Taxes - Components of Deferred Taxes (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets:
Federal and state-operating loss carryforwards	$ 133,671	$ 108,236
Stock-based compensation	11,082	16,563
Operating lease liabilities	1,656	2,600
Research and development credits	11,106	8,872
Other	1,125	2,317
Total deferred tax assets	158,640	138,588
Valuation allowance	(157,095)	(131,332)
Deferred tax asset, net of valuation allowance	1,545	7,256
Deferred tax liabilities:
In-process research and development		(7,443)
Operating lease right-of-use assets	(1,545)	(2,344)
Total deferred tax liabilities	$ (1,545)	(9,787)
Net deferred tax liability		$ (2,531)

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Valuation allowance increased	$ 25,800	$ 22,800
Income tax benefit	$ 2,531	$ 0

Income Taxes - Summary of Net O

Income Taxes - Summary of Net Operating Loss and Tax Credit Carryforwards (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Income Taxes [Line Items]
Research and development credits	$ 11,106	$ 8,872
Federal
Income Taxes [Line Items]
Net operating losses	346,847
Net operating losses	123,552
Research and development credits	$ 10,845
Federal | Minimum
Income Taxes [Line Items]
Expiration Years	2027
Federal | Minimum | Research Tax Credit Carryforward
Income Taxes [Line Items]
Expiration Years	2028
Federal | Maximum
Income Taxes [Line Items]
Expiration Years	2037
Federal | Maximum | Research Tax Credit Carryforward
Income Taxes [Line Items]
Expiration Years	2041
State
Income Taxes [Line Items]
Net operating losses	$ 880
Net operating losses	545,256
Research and development credits	$ 4,174
State | Minimum
Income Taxes [Line Items]
Expiration Years	2031
State | Maximum
Income Taxes [Line Items]
Expiration Years	2041

Income Taxes - Activity Related

Income Taxes - Activity Related to Gross Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Balances as of beginning of year	$ 2,655	$ 6,070
Increases related to prior year tax positions	1	0
Decreases related to prior year tax positions	(82)	(4,162)
Increases related to current year tax positions	663	747
Balances as of end of year	$ 3,237	$ 2,655

Leases - Additional Information

Leases - Additional Information (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Leases [Abstract]
Operating lease, liability	$ 6,476
Operating lease, right-of-use asset	$ 6,042	$ 9,131
Weighted-average remaining lease term - operating leases	1 year 10 months 24 days
Weighted-average discount rate - operating leases	9.70%

Leases - Schedule of Quantitati

Leases - Schedule of Quantitative Information of Operating Leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Lease cost
Operating lease cost	$ 3,840	$ 5,214
Short-term lease cost	268	401
Variable lease cost	1,317	1,468
Sublease income	(142)
Total lease cost, net	5,283	7,083
Operating cash flows from operating leases	3,786	4,513
ROU assets exchanged for new operating lease liabilities	$ 126	$ 1,302

Leases - Schedule of Maturities

Leases - Schedule of Maturities Operating Lease Liabilities (Details) $ in Thousands	Dec. 31, 2021USD ($)
Lease Cost [Abstract]
2022	$ 3,643
2023	3,491
2024	10
Total	7,144
Less: present value discount	(668)
Operating lease liabilities	$ 6,476

Employee Benefit Plan - Additio

Employee Benefit Plan - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Compensation And Retirement Disclosure [Abstract]
Defined Contribution Plan, Employer Discretionary Contribution Amount	$ 0.9	$ 0.9