Assembly Biosciences (ASMB) 10-Q 12 May 22 2022 Q1 Quarterly report Financial data

Document And Entity Information

Document And Entity Information - shares	3 Months Ended
	Mar. 31, 2022	May 09, 2022
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Mar. 31, 2022
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	2022
Document Fiscal Period Focus	Q1
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, par value $0.001
Entity Common Stock, Shares Outstanding		48,216,473
Entity Shell Company	false
Entity Emerging Growth Company	false
Entity Small Business	true

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Current assets
Cash and cash equivalents	$ 51,174	$ 45,627
Marketable securities - short-term	71,826	101,000
Accounts receivable from collaborations	524	336
Prepaid expenses and other current assets	7,253	7,241
Total current assets	130,777	154,204
Marketable securities - long-term	23,459	27,972
Property and equipment, net	1,019	1,139
Operating lease right-of-use (ROU) assets	5,300	6,042
Other assets	2,175	1,703
Total assets	162,730	191,060
Current liabilities
Accounts payable	1,407	2,659
Accrued research and development expenses	3,596	3,400
Other accrued expenses	2,499	6,863
Operating lease liabilities - short-term	3,207	3,151
Total current liabilities	10,709	16,073
Deferred revenue	2,733	2,733
Operating lease liabilities - long-term	2,497	3,325
Total liabilities	15,939	22,131
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 March 31, 2022 and December 31, 2021; 48,132,937 and 48,120,437 shares issued and outstanding as of March 31, 2022 and December 31, 2021, respectively	48	48
Additional paid-in capital	802,170	800,728
Accumulated other comprehensive loss	(908)	(419)
Accumulated deficit	(654,519)	(631,428)
Total stockholders' equity	146,791	168,929
Total liabilities and stockholders' equity	$ 162,730	$ 191,060

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Mar. 31, 2022	Dec. 31, 2021
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	48,132,937	48,132,937
Common stock, shares outstanding	48,120,437	48,120,437

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Operating expenses
Research and development	$ 17,205	$ 18,554
General and administrative	5,957	8,704
Total operating expenses	23,162	27,258
Loss from operations	(23,162)	(27,258)
Other income
Interest and other income, net	71	58
Total other income	71	58
Net loss	(23,091)	(27,200)
Other comprehensive loss
Unrealized loss on marketable securities	(489)	(1)
Comprehensive loss	$ (23,580)	$ (27,201)
Net loss per share, basic and diluted	$ (0.48)	$ (0.69)
Weighted average common shares outstanding, basic and diluted	48,123,930	39,679,734

CONDENSED CONSOLIDATED STATEM_2

CONDENSED 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, 2020	$ 240,578	$ 34	$ 742,387	$ (270)	$ (501,573)
Balance (in shares) at Dec. 31, 2020		34,026,680
Issuance of common stock under at-the-market (ATM) equity offering program, net of issuance costs	34,137	$ 6	34,131
Issuance of common stock under at-the-market (ATM) equity offering program, net of issuance costs (share)		5,991,858
Issuance of shares of common stock for settlement of restricted stock units (RSUs) (in shares)		86,146
Unrealized loss on marketable debt securities	(1)			(1)
Stock-based compensation	(270)		(270)
Net loss	(27,200)				(27,200)
Balance at Mar. 31, 2021	247,244	$ 40	776,248	(271)	(528,773)
Balance (in shares) at Mar. 31, 2021		40,104,684
Balance at Dec. 31, 2021	168,929	$ 48	800,728	(419)	(631,428)
Balance (in shares) at Dec. 31, 2021		48,120,437
Issuance of shares of common stock for settlement of restricted stock units (RSUs) (in shares)		12,500
Unrealized loss on marketable debt securities	(489)			(489)
Stock-based compensation	1,442		1,442
Net loss	(23,091)				(23,091)
Balance at Mar. 31, 2022	$ 146,791	$ 48	$ 802,170	$ (908)	$ (654,519)
Balance (in shares) at Mar. 31, 2022		48,132,937

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Cash flows from operating activities
Net loss	$ (23,091)	$ (27,200)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	120	107
Stock-based compensation	1,443	(286)
Net amortization of investments in marketable debt securities	149	92
Non-cash rent expense	893	1,135
Loss on disposal of property and equipment	0	1,611
Changes in operating assets and liabilities:
Accounts receivable from collaboration	(188)	1,027
Prepaid expenses and other current assets	(12)	303
Other assets	(472)	358
Accounts payable	(1,252)	(1,036)
Accrued research and development expenses	196	(102)
Other accrued expenses	(4,365)	(8,312)
Operating lease liabilities	(923)	(1,041)
Net cash used in operating activities	(27,502)	(33,344)
Cash flows from investing activities
Purchases of property and equipment	0	(3,078)
Proceeds from sale of property and equipment	0	857
Purchases of marketable securities	(3,951)	(49,213)
Proceeds from maturities of marketable securities	30,000	66,450
Proceeds from sale of marketable securities	7,000	3,000
Net cash provided by investing activities	33,049	18,016
Cash flows from financing activities
Proceeds from the issuance of common stock under ATM equity offering program, net of issuance costs	0	34,137
Net cash provided by financing activities	0	34,137
Net increase in cash and cash equivalents	5,547	18,809
Cash and cash equivalents at the beginning of the period	45,627	59,444
Cash and cash equivalents at the end of the period	51,174	78,253
Supplemental non-cash investing and financing activities
Operating lease liabilities arising from obtaining ROU assets	0	42
Remeasurement of lease liabilities arising from modification of ROU assets	$ 0	$ (788)

Nature of Business

Nature of Business	3 Months Ended
	Mar. 31, 2022
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 advancing a novel class of oral therapeutic candidates for the treatment of chronic 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 and is currently advancing an early-stage program evaluating a novel small molecule approach to inhibit entry for both HBV and hepatitis delta viruses. 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 or an applicable foreign regulatory agency. Since inception, the Company’s operations have been financed primarily through the sale of equity securities, proceeds from the exercise of warrants and stock options, 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 these unaudited condensed 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. The Company cannot assure such funding will be available on reasonable terms, if at all. Market volatility resulting from the global 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	3 Months Ended
	Mar. 31, 2022
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Note 2 - Summary of Significant Accounting Policies Basis of Presentation The accompanying unaudited condensed consolidated financial statements include the accounts of the Company and its subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with the accounting principles generally accepted in the United States of America (U.S. GAAP) for interim financial information and pursuant to the instructions to Form 10-Q and Rule 10-01 of Regulation S-X of the SEC. In management’s opinion, the unaudited condensed consolidated financial statements have been prepared on the same basis as the annual audited consolidated financial statements and include normal recurring adjustments necessary for the fair presentation of the Company’s financial position and its results of operations and comprehensive loss and its cash flows for the periods presented. These statements do not include all disclosures required by U.S. GAAP and should be read in conjunction with the Company’s audited consolidated financial statements and accompanying notes for the fiscal year ended December 31, 2021 , which are contained in the 2021 Annual Report . The results for the three months ended March 31, 2022 are not necessarily indicative of results to be expected for the entire year ending December 31, 2022 or future operating periods. Use of Estimates The preparation of the unaudited condensed 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. Estimates inherent in the preparation of the accompanying unaudited condensed consolidated financial statements include estimates of costs incurred but not yet invoiced for research and development accruals, recoverability and useful lives of our long-lived assets, amounts receivable under collaboration agreements, measurement of operating lease liabilities, and the fair value of stock options, stock appreciation rights, and RSUs granted to employees, directors, and consultants. The Company’s estimates could be affected by external conditions, including those unique to the Company and general economic conditions. It is reasonably possible these external factors could have an effect on the Company’s estimates and could cause actual results to differ materially 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 clinical and preclinical studies were largely unaffected, but as the pandemic has continued, the Company has experienced enrollment delays for two of its multi-drug combination clinical studies, delayed animal studies and delayed shipping of compounds necessary for the Company’s research programs. Although the clinical studies that experienced enrollment delays are now fully enrolled, the lockdowns resulting from China’s strict “zero covid” policy are also impacting execution of one of these multi-drug clinical studies. The Company relies on contract research organizations (CROs), some of which are in China and India. While these CROs have experienced pandemic-related impacts from time to time, the latest shutdowns in China have impacted the Company more than earlier in the pandemic. In addition, the study plan of the Company’s triple combination study with Antios Therapeutics, Inc. (Antios) initially included a site in Ukraine, but the study will no longer be conducted there due to the instability resulting from Russia’s invasion. These changes to the Company’s study plan will result in a delayed data readout. Income Taxes Effective January 1, 2022, a provision of the Tax Cuts and Jobs Act (TCJA) has taken effect creating a significant change to the treatment of research and experimental expenditures under Section 174 of the IRC (Sec. 174 expenses). Historically, businesses have had the option of deducting Sec. 174 expenses in the year incurred or capitalizing and amortizing the costs over five years. The new TCJA provision, however, eliminates this option and will require Sec. 174 expenses associated with research conducted in the U.S to be capitalized and amortized over a five-year period. For expenses associated with research outside of the United States, Sec. 174 expenses will be capitalized and amortized over a 15-year period. The Company prepared an analysis of the tax impact of capitalizing and amortizing these costs over the required periods and for calendar year 2022, it is expecting to be in a loss position after the estimated addback. Net Loss per Share Basic net loss per share of common stock excludes dilution and is computed by dividing net loss by the weighted average number of shares of common stock outstanding during the period. Diluted net loss per share of common stock reflects the potential dilution that 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): Three Months Ended March 31, 2022 2021 Numerator: Net loss $ (23,091 ) $ (27,200 ) Denominator: Weighted average common shares and pre-funded warrants outstanding - basic and diluted 48,123,930 39,679,734 Net loss per share - basic and diluted $ (0.48 ) $ (0.69 ) Securities excluded from the computation of diluted net loss per share because including them would have been antidilutive are as follows: March 31, 2022 2021 Options to purchase common stock 7,475,876 7,382,515 Common stock subject to purchase under our Employee Stock Purchase Plan (ESPP) 129,107 44,870 Unvested RSUs 1,553,755 666,574 Total 9,158,738 8,093,959

Fair Value Measurements and Inv

Fair Value Measurements and Investments in Marketable Securities	3 Months Ended
	Mar. 31, 2022
Investments Debt And Equity Securities [Abstract]
Fair Value Measurements and Investments in Marketable Securities	Note 3 – Fair Value Measurements and Investments in Marketable Securities 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 that approximate their fair value due to their liquid or short-term nature, such as cash, accounts receivable, accounts payable and accrued expenses. 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 that 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. Investments in marketable securities consisted of the following (in thousands): March 31, 2022 Amortized Cost Gross Unrealized Gain Gross Unrealized Loss Fair Value Cash equivalents Money market fund $ 48,361 $ — $ — $ 48,361 Total cash equivalents 48,361 — — 48,361 Short-term marketable securities U.S. and foreign corporate debt securities 4,097 — (63 ) 4,034 Asset-backed securities 21,978 — (97 ) 21,881 U.S. and foreign commercial paper 45,913 — (2 ) 45,911 Total short-term marketable securities 71,988 — (162 ) 71,826 Long-term marketable securities U.S. and foreign corporate debt securities 14,966 — (280 ) 14,686 U.S. treasury securities 8,966 — (193 ) 8,773 Total long-term marketable securities 23,932 — (473 ) 23,459 Total cash equivalents and marketable securities $ 144,281 $ — $ (635 ) $ 143,646 December 31, 2021 Amortized Cost Gross Unrealized Gain Gross Unrealized Loss 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 7,015 — (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 Short-term marketable securities held as of March 31, 2022 had contractual maturities of less than one year. Long-term marketable securities held as of March 31, 2022 had contractual maturities of at least one year but less than two years. Realized gains and losses for the three months ended March 31, 2022 and 2021 were not significant. None of the Company’s investments have been in a continuous unrealized loss position for more than 12 months as of March 31, 2022. The following tables present the fair value of the Company’s financial assets measured at fair value on a recurring basis (in thousands): March 31, 2022 Level 1 Level 2 Level 3 Fair Value Cash equivalents Money market fund $ 48,361 $ — $ — $ 48,361 Total cash equivalents 48,361 — — 48,361 Short-term marketable securities U.S. and foreign corporate debt securities — 4,034 — 4,034 Asset-backed securities — 21,881 — 21,881 U.S. and foreign commercial paper — 45,911 — 45,911 Total short-term marketable securities — 71,826 — 71,826 Long-term marketable securities U.S. and foreign corporate debt securities — 14,686 — 14,686 U.S. treasury securities — 8,773 — 8,773 Total long-term marketable securities — 23,459 — 23,459 Total assets measured at fair value $ 48,361 $ 95,285 $ — $ 143,646 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 The Company estimates the fair value of its investments in marketable securities 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. There were no transfers between Level 1, Level 2 or Level 3 during the periods presented.

Other Accrued Expenses

Other Accrued Expenses	3 Months Ended
	Mar. 31, 2022
Payables And Accruals [Abstract]
Other Accrued Expenses	Note 4 – Other Accrued Expenses Other accrued expenses consist of the following (in thousands): March 31, December 31, 2022 2021 Accrued expenses: Accrued compensation $ 2,161 $ 6,426 Accrued professional fees and other 338 437 Total accrued expenses $ 2,499 $ 6,863

Stale of Common Stock

Stale of Common Stock	3 Months Ended
	Mar. 31, 2022
Equity [Abstract]
Sale of Common Stock	Note 5 – 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 three months ended March 31, 2021, the Company sold 5,991,858 shares of common stock under the 2020 ATM, for which the Company received net proceeds of $34.1 million, after deducting commissions, fees and expenses. The Company did not sell any shares of common stock under the 2020 ATM during the three months ended March 31, 2022.

Stock Plans and Stock-Based Com

Stock Plans and Stock-Based Compensation	3 Months Ended
	Mar. 31, 2022
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock Plans and Stock-Based Compensation	Note 6 – Stock Plans and Stock-Based Compensation Equity Incentive Plans In May 2021, the Company’s stockholders approved an amendment to the Assembly Biosciences, Inc. 2018 Stock Incentive Plan (2018 Plan) that increased the aggregate number of shares of common stock reserved under the 2018 Plan to 6,600,000 and an Amended and Restated Assembly Biosciences, Inc. 2018 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 March 31, 2022, the Company had awards outstanding under the following shareholder-approved plans: the 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. The Company issues new shares of common stock to settle options exercised and 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 A summary of the Company’s option activity and related information for the three months ended March 31, 2022 is as follows: 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, 2021 6,161,901 $ 11.77 6.4 $ 53 Granted 1,479,550 2.29 Forfeited (141,264 ) 16.46 Expired (24,311 ) 26.86 Outstanding as of March 31, 2022 7,475,876 $ 9.76 6.9 $ 6 Options vested and exercisable as of March 31, 2022 4,120,830 $ 12.87 5.1 $ — The weighted-average grant-date fair value of options granted was $1.63 and $3.15 during the three months ended March 31, 2022 and 2021, respectively. There were no options exercised during the three months ended March 31, 2022 or 2021. RSUs A summary of the Company’s RSUs and related information for the three months ended March 31, 2022 is as follows: Number of RSUs Weighted Average Fair Value Per RSU at Grant Price Nonvested as of December 31, 2021 970,339 $ 7.04 Granted 730,275 2.30 Vested (92,286 ) 12.10 Forfeited (54,573 ) 6.81 Nonvested as of March 31, 2022 1,553,755 $ 4.96 The total fair value of RSUs vested and settled during the three months ended March 31, 2022 and 2021 was $1.1 million and $2.5 million, respectively. The total intrinsic value of RSUs vested and settled during the three months ended March 31, 2022 and 2021 was $0.2 million and $0.6 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 March 31, 2022. 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 its 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 March 31, 2022. In March 2022, the Company granted 255,000 RSUs with market-based vesting conditions to members of management, including its executive officers. The awards had a grant date fair value of $0.4 million and are being recognized over the derived service period of 1.5 years and vest upon the achievement of certain market-based conditions which have not been achieved as of March 31, 2022. Stock-based compensation expense for the awards was nominal during the three months ended March 31, 2022. ESPP There were no shares purchased under the 2018 ESPP during the three months ended March 31, 2022 or 2021. Valuation Assumptions The fair value of the stock options granted or modified during the periods indicated was estimated using the Black-Scholes option pricing model, based on the following assumptions: Three Months Ended March 31, 2022 2021 Exercise price $1.53 - $2.45 $4.33 - $5.79 Expected volatility 79.2% - 81.6% 81.4% - 91.2% Risk-free rate 1.41% - 2.48% 0.50% - 1.37% Expected term (years) 5.5 - 7.0 5.5 - 7.0 Expected dividend yield 0% 0% The fair value of RSUs granted is determined based on the price of the Company’s common stock on the date of grant. The fair value of market-based RSUs granted is determined using the Monte-Carlo simulation model. The fair value of ESPP purchase rights were not material for any period presented. Stock-Based Compensation Expense The following table summarizes the components of total stock-based compensation expense included in the condensed consolidated statements of operations and comprehensive loss (in thousands): Three Months Ended March 31, 2022 2021 Research and development $ 778 $ (2,091 ) (1) General and administrative 665 1,805 Total stock-based compensation expense $ 1,443 $ (286 ) (1) Includes the reversal of previously recognized stock-based compensation expense of $3.6 million related to forfeited awards of terminated employees, $2.7 million of which resulted from the wind-down of the Company’s Microbiome program. As of March 31, 2022, there was $10.9 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 1.8 years.

Collaboration Agreements

Collaboration Agreements	3 Months Ended
	Mar. 31, 2022
Collaboration Agreement [Abstract]
Collaboration Agreements	Note 7 - Collaboration Agreements 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 (the Licensed Product Candidates) for chronic HBV infection in the People’s Republic of China, Hong Kong, Taiwan and Macau. As of March 31, 2022 the only remaining performance obligation under the BeiGene Agreement not considered to be complete is the transfer of the ABI-H3733 License. The transaction price allocated to ABI-H3733 of $2.7 million was recognized as a long-term deferred revenue contract liability as of both March 31, 2022 and December 31, 2021, and will be recognized as revenue when the Company provides pre-Phase 3 clinical study know-how and development results for ABI-H3733 to BeiGene or a termination of the BeiGene Agreement for ABI-H3733. During the three months ended March 31, 2022 and 2021, the Company did not recognize any revenue or 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 in 2020. 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 March 31, 2022 and December 31, 2021, the remaining unamortized contract costs are $0.2 million and are included in other assets on the condensed consolidated balance sheet. Arbutus Biopharma Agreement In August 2020, the Company and Arbutus Biopharma Corporation (Arbutus Biopharma) entered into a Clinical Trial Collaboration Agreement (the Arbutus Biopharma 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. During the three months ended March 31, 2022 and 2021, the Company recognized a reduction of research and development expenses of $0.6 million and $0.5 million, respectively, under the Arbutus Biopharma Antios Agreement In July 2021, the Company and Antios entered into a Clinical Trial Collaboration Agreement (the Antios Agreement) to collaborate on a triple combination therapy using VBR and Antios’s active site polymerase inhibitor nucleotide ATI-2173 for the treatment of HBV. Assembly and Antios are individually responsible for the study’s manufacturing costs but will equally share the remaining costs of the study. During the three months ended March 31, 2022 , the Company incurred $0.1 million in research and development expenses under the Antios Agreement.

Milestones and Research Agreeme

Milestones and Research Agreements	3 Months Ended
	Mar. 31, 2022
Milestones And Research Agreements [Abstract]
Milestones and Research Agreements	Note 8 - 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 such fees for that year. The Company paid IURTC $0.1 million in diligence maintenance fees during the three months ended March 31, 2022. No amounts were paid during the three months ended March 31, 2021. 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. 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. No amounts were accrued for this agreement as of and for the three months ended March 31, 2022 or 2021. Door Pharma Agreement In November 2020, the Company and Door Pharmaceuticals, LLC (Door Pharma) entered into an exclusive, two-year During the three months ended March 31, 2022 and 2021, the Company incurred research and development funding of $0.7 million and $0.4 million, respectively, under the Door Pharma Agreement. No success-based milestones were determined to have occurred under this agreement during the three months ended March 31, 2022 or 2021. The Company terminated the Door Pharma Agreement in May 2022, effective September 2022, . Under the consolidation accounting standard, the Company determined Door Pharma is a variable interest entity. The Company does not have the power to direct the activities which 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 March 31, 2022, the Company has not provided financial or other support to Door Pharma that was not contractually required.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2022
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited condensed consolidated financial statements include the accounts of the Company and its subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with the accounting principles generally accepted in the United States of America (U.S. GAAP) for interim financial information and pursuant to the instructions to Form 10-Q and Rule 10-01 of Regulation S-X of the SEC. In management’s opinion, the unaudited condensed consolidated financial statements have been prepared on the same basis as the annual audited consolidated financial statements and include normal recurring adjustments necessary for the fair presentation of the Company’s financial position and its results of operations and comprehensive loss and its cash flows for the periods presented. These statements do not include all disclosures required by U.S. GAAP and should be read in conjunction with the Company’s audited consolidated financial statements and accompanying notes for the fiscal year ended December 31, 2021 , which are contained in the 2021 Annual Report . The results for the three months ended March 31, 2022 are not necessarily indicative of results to be expected for the entire year ending December 31, 2022 or future operating periods.
Use of Estimates	Use of Estimates The preparation of the unaudited condensed 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. Estimates inherent in the preparation of the accompanying unaudited condensed consolidated financial statements include estimates of costs incurred but not yet invoiced for research and development accruals, recoverability and useful lives of our long-lived assets, amounts receivable under collaboration agreements, measurement of operating lease liabilities, and the fair value of stock options, stock appreciation rights, and RSUs granted to employees, directors, and consultants. The Company’s estimates could be affected by external conditions, including those unique to the Company and general economic conditions. It is reasonably possible these external factors could have an effect on the Company’s estimates and could cause actual results to differ materially 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 clinical and preclinical studies were largely unaffected, but as the pandemic has continued, the Company has experienced enrollment delays for two of its multi-drug combination clinical studies, delayed animal studies and delayed shipping of compounds necessary for the Company’s research programs. Although the clinical studies that experienced enrollment delays are now fully enrolled, the lockdowns resulting from China’s strict “zero covid” policy are also impacting execution of one of these multi-drug clinical studies. The Company relies on contract research organizations (CROs), some of which are in China and India. While these CROs have experienced pandemic-related impacts from time to time, the latest shutdowns in China have impacted the Company more than earlier in the pandemic. In addition, the study plan of the Company’s triple combination study with Antios Therapeutics, Inc. (Antios) initially included a site in Ukraine, but the study will no longer be conducted there due to the instability resulting from Russia’s invasion. These changes to the Company’s study plan will result in a delayed data readout.
Income Taxes	Income Taxes Effective January 1, 2022, a provision of the Tax Cuts and Jobs Act (TCJA) has taken effect creating a significant change to the treatment of research and experimental expenditures under Section 174 of the IRC (Sec. 174 expenses). Historically, businesses have had the option of deducting Sec. 174 expenses in the year incurred or capitalizing and amortizing the costs over five years. The new TCJA provision, however, eliminates this option and will require Sec. 174 expenses associated with research conducted in the U.S to be capitalized and amortized over a five-year period. For expenses associated with research outside of the United States, Sec. 174 expenses will be capitalized and amortized over a 15-year period. The Company prepared an analysis of the tax impact of capitalizing and amortizing these costs over the required periods and for calendar year 2022, it is expecting to be in a loss position after the estimated addback.
Net Loss per Share	Net Loss per Share Basic net loss per share of common stock excludes dilution and is computed by dividing net loss by the weighted average number of shares of common stock outstanding during the period. Diluted net loss per share of common stock reflects the potential dilution that 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): Three Months Ended March 31, 2022 2021 Numerator: Net loss $ (23,091 ) $ (27,200 ) Denominator: Weighted average common shares and pre-funded warrants outstanding - basic and diluted 48,123,930 39,679,734 Net loss per share - basic and diluted $ (0.48 ) $ (0.69 ) Securities excluded from the computation of diluted net loss per share because including them would have been antidilutive are as follows: March 31, 2022 2021 Options to purchase common stock 7,475,876 7,382,515 Common stock subject to purchase under our Employee Stock Purchase Plan (ESPP) 129,107 44,870 Unvested RSUs 1,553,755 666,574 Total 9,158,738 8,093,959

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 2022
Accounting Policies [Abstract]
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): Three Months Ended March 31, 2022 2021 Numerator: Net loss $ (23,091 ) $ (27,200 ) Denominator: Weighted average common shares and pre-funded warrants outstanding - basic and diluted 48,123,930 39,679,734 Net loss per share - basic and diluted $ (0.48 ) $ (0.69 )
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	Securities excluded from the computation of diluted net loss per share because including them would have been antidilutive are as follows: March 31, 2022 2021 Options to purchase common stock 7,475,876 7,382,515 Common stock subject to purchase under our Employee Stock Purchase Plan (ESPP) 129,107 44,870 Unvested RSUs 1,553,755 666,574 Total 9,158,738 8,093,959

Fair Value Measurements and I_2

Fair Value Measurements and Investments in Marketable Securities (Tables)	3 Months Ended
	Mar. 31, 2022
Investments Debt And Equity Securities [Abstract]
Schedule of Investments in Marketable Securities	Investments in marketable securities consisted of the following (in thousands): March 31, 2022 Amortized Cost Gross Unrealized Gain Gross Unrealized Loss Fair Value Cash equivalents Money market fund $ 48,361 $ — $ — $ 48,361 Total cash equivalents 48,361 — — 48,361 Short-term marketable securities U.S. and foreign corporate debt securities 4,097 — (63 ) 4,034 Asset-backed securities 21,978 — (97 ) 21,881 U.S. and foreign commercial paper 45,913 — (2 ) 45,911 Total short-term marketable securities 71,988 — (162 ) 71,826 Long-term marketable securities U.S. and foreign corporate debt securities 14,966 — (280 ) 14,686 U.S. treasury securities 8,966 — (193 ) 8,773 Total long-term marketable securities 23,932 — (473 ) 23,459 Total cash equivalents and marketable securities $ 144,281 $ — $ (635 ) $ 143,646 December 31, 2021 Amortized Cost Gross Unrealized Gain Gross Unrealized Loss 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 7,015 — (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
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 (in thousands): March 31, 2022 Level 1 Level 2 Level 3 Fair Value Cash equivalents Money market fund $ 48,361 $ — $ — $ 48,361 Total cash equivalents 48,361 — — 48,361 Short-term marketable securities U.S. and foreign corporate debt securities — 4,034 — 4,034 Asset-backed securities — 21,881 — 21,881 U.S. and foreign commercial paper — 45,911 — 45,911 Total short-term marketable securities — 71,826 — 71,826 Long-term marketable securities U.S. and foreign corporate debt securities — 14,686 — 14,686 U.S. treasury securities — 8,773 — 8,773 Total long-term marketable securities — 23,459 — 23,459 Total assets measured at fair value $ 48,361 $ 95,285 $ — $ 143,646 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

Other Accrued Expenses (Tables)

Other Accrued Expenses (Tables)	3 Months Ended
	Mar. 31, 2022
Payables And Accruals [Abstract]
Schedule of Other Accrued Expenses	Other accrued expenses consist of the following (in thousands): March 31, December 31, 2022 2021 Accrued expenses: Accrued compensation $ 2,161 $ 6,426 Accrued professional fees and other 338 437 Total accrued expenses $ 2,499 $ 6,863

Stock Plans and Stock-Based C_2

Stock Plans and Stock-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2022
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Stock Option Activity and Related Information	A summary of the Company’s option activity and related information for the three months ended March 31, 2022 is as follows: 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, 2021 6,161,901 $ 11.77 6.4 $ 53 Granted 1,479,550 2.29 Forfeited (141,264 ) 16.46 Expired (24,311 ) 26.86 Outstanding as of March 31, 2022 7,475,876 $ 9.76 6.9 $ 6 Options vested and exercisable as of March 31, 2022 4,120,830 $ 12.87 5.1 $ —
Summary of Restricted Stock Units and Related Information	A summary of the Company’s RSUs and related information for the three months ended March 31, 2022 is as follows: Number of RSUs Weighted Average Fair Value Per RSU at Grant Price Nonvested as of December 31, 2021 970,339 $ 7.04 Granted 730,275 2.30 Vested (92,286 ) 12.10 Forfeited (54,573 ) 6.81 Nonvested as of March 31, 2022 1,553,755 $ 4.96
Summary of Assumptions Used to Estimate Fair Values of Stock Options Grants	The fair value of the stock options granted or modified during the periods indicated was estimated using the Black-Scholes option pricing model, based on the following assumptions: Three Months Ended March 31, 2022 2021 Exercise price $1.53 - $2.45 $4.33 - $5.79 Expected volatility 79.2% - 81.6% 81.4% - 91.2% Risk-free rate 1.41% - 2.48% 0.50% - 1.37% Expected term (years) 5.5 - 7.0 5.5 - 7.0 Expected dividend yield 0% 0%
Schedule of Recognized Stock-Based Compensation Expense	The following table summarizes the components of total stock-based compensation expense included in the condensed consolidated statements of operations and comprehensive loss (in thousands): Three Months Ended March 31, 2022 2021 Research and development $ 778 $ (2,091 ) (1) General and administrative 665 1,805 Total stock-based compensation expense $ 1,443 $ (286 ) (1) Includes the reversal of previously recognized stock-based compensation expense of $3.6 million related to forfeited awards of terminated employees, $2.7 million of which resulted from the wind-down of the Company’s Microbiome program.

Nature of Business - Additional

Nature of Business - Additional Information (Details)	3 Months Ended
	Mar. 31, 2022segmentproduct
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- Additional Information (Details)	3 Months Ended
	Mar. 31, 2022
Significant Accounting Policies [Line Items]
Capitalized and amortized costs period	5 years
Outside of United States
Significant Accounting Policies [Line Items]
Capitalized and amortized costs period	15 years

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Schedule of Earnings Per Share, Basic and Diluted (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Numerator:
Net loss	$ (23,091)	$ (27,200)
Denominator:
Weighted average common shares outstanding, basic and diluted	48,123,930	39,679,734
Net loss per share, basic and diluted	$ (0.48)	$ (0.69)

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share (Details) - shares	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities excluded from computation of loss per share	9,158,738	8,093,959
Options
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities excluded from computation of loss per share	7,475,876	7,382,515
Common stock subject to purchase under Employee Stock Purchase Plan (ESPP)
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities excluded from computation of loss per share	129,107	44,870
RSUs
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities excluded from computation of loss per share	1,553,755	666,574

Fair Value Measurements and I_3

Fair Value Measurements and Investments in Marketable Securities - Schedule of Investments in Marketable Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Investments in marketable securities:
Amortized Cost	$ 51,174	$ 45,627
Fair Value	71,826	101,000
Amortized Cost	144,281	171,625
Gross Unrealized Gain	0	0
Gross Unrealized Loss	(635)	(146)
Fair Value	143,646	171,479
Cash equivalents
Investments in marketable securities:
Amortized Cost	48,361	42,507
Gross Unrealized Gain	0	0
Gross Unrealized Loss	0	0
Fair Value	48,361	42,507
Short-term marketable securities
Investments in marketable securities:
Amortized Cost	71,988	101,041
Gross Unrealized Gain	0	0
Gross Unrealized Loss	(162)	(41)
Fair Value	71,826	101,000
Long-term marketable securities
Investments in marketable securities:
Amortized Cost	23,932	28,077
Gross Unrealized Gain	0	0
Gross Unrealized Loss	(473)	(105)
Fair Value	23,459	27,972
Money market fund | Cash equivalents
Investments in marketable securities:
Amortized Cost	48,361	42,507
Gross Unrealized Gain	0	0
Gross Unrealized Loss	0	0
Fair Value	48,361	42,507
U.S and foreign corporate debt securities | Short-term marketable securities
Investments in marketable securities:
Amortized Cost	4,097	7,015
Gross Unrealized Gain	0	0
Gross Unrealized Loss	(63)	(2)
Fair Value	4,034	7,013
U.S and foreign corporate debt securities | Long-term marketable securities
Investments in marketable securities:
Amortized Cost	14,966	19,117
Gross Unrealized Gain	0	0
Gross Unrealized Loss	(280)	(74)
Fair Value	14,686	19,043
Asset-backed securities | Short-term marketable securities
Investments in marketable securities:
Amortized Cost	21,978	29,097
Gross Unrealized Gain	0	0
Gross Unrealized Loss	(97)	(38)
Fair Value	21,881	29,059
U.S. and foreign commercial paper | Short-term marketable securities
Investments in marketable securities:
Amortized Cost	45,913	64,929
Gross Unrealized Gain	0	0
Gross Unrealized Loss	(2)	(1)
Fair Value	45,911	64,928
U.S. treasury securities | Long-term marketable securities
Investments in marketable securities:
Amortized Cost	8,966	8,960
Gross Unrealized Gain	0	0
Gross Unrealized Loss	(193)	(31)
Fair Value	$ 8,773	$ 8,929

Fair Value Measurements and I_4

Fair Value Measurements and Investments in Marketable Securities - Additional Information (Details) - USD ($)	3 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Investments in marketable securities:
Fair value assets transfers between level 1, level 2 or level 3	$ 0	$ 0
Short-term marketable securities
Investments in marketable securities:
Available for sale securities maturity term	less than one year
Long-term marketable securities
Investments in marketable securities:
Available for sale securities maturity term	at least one year but less than two years.

Fair Value Measurements and I_5

Fair Value Measurements and Investments in Marketable Securities - Schedule of Fair Value of Financial Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Short-term marketable securities
Short-term marketable securities	$ 71,826	$ 101,000
Long-term marketable securities
Marketable securities - long-term	23,459	27,972
Recurring
Cash equivalents
Cash equivalents	48,361	42,507
Short-term marketable securities
Short-term marketable securities	71,826	101,000
Long-term marketable securities
Marketable securities - long-term	23,459	27,972
Total assets measured at fair value	143,646	171,479
Recurring | U.S and foreign corporate debt securities
Short-term marketable securities
Short-term marketable securities	4,034	7,013
Long-term marketable securities
Marketable securities - long-term		19,043
Recurring | Asset-backed securities
Short-term marketable securities
Short-term marketable securities	21,881	29,059
Recurring | U.S. and foreign commercial paper
Short-term marketable securities
Short-term marketable securities	45,911	64,928
Recurring | U.S. treasury securities
Long-term marketable securities
Marketable securities - long-term	8,773	8,929
Recurring | U.S and foreign corporate debt securities
Long-term marketable securities
Marketable securities - long-term	14,686
Recurring | Money market fund
Cash equivalents
Cash equivalents	48,361	42,507
Recurring | Level 1
Cash equivalents
Cash equivalents	48,361	42,507
Short-term marketable securities
Short-term marketable securities	0	0
Long-term marketable securities
Marketable securities - long-term	0	0
Total assets measured at fair value	48,361	42,507
Recurring | Level 1 | U.S and foreign corporate debt securities
Short-term marketable securities
Short-term marketable securities	0	0
Long-term marketable securities
Marketable securities - long-term		0
Recurring | Level 1 | Asset-backed securities
Short-term marketable securities
Short-term marketable securities	0	0
Recurring | Level 1 | U.S. and foreign commercial paper
Short-term marketable securities
Short-term marketable securities	0	0
Recurring | Level 1 | U.S. treasury securities
Long-term marketable securities
Marketable securities - long-term	0	0
Recurring | Level 1 | U.S and foreign corporate debt securities
Long-term marketable securities
Marketable securities - long-term	0
Recurring | Level 1 | Money market fund
Cash equivalents
Cash equivalents	48,361	42,507
Recurring | Level 2
Cash equivalents
Cash equivalents	0	0
Short-term marketable securities
Short-term marketable securities	71,826	101,000
Long-term marketable securities
Marketable securities - long-term	23,459	27,972
Total assets measured at fair value	95,285	128,972
Recurring | Level 2 | U.S and foreign corporate debt securities
Short-term marketable securities
Short-term marketable securities	4,034	7,013
Long-term marketable securities
Marketable securities - long-term		19,043
Recurring | Level 2 | Asset-backed securities
Short-term marketable securities
Short-term marketable securities	21,881	29,059
Recurring | Level 2 | U.S. and foreign commercial paper
Short-term marketable securities
Short-term marketable securities	45,911	64,928
Recurring | Level 2 | U.S. treasury securities
Long-term marketable securities
Marketable securities - long-term	8,773	8,929
Recurring | Level 2 | U.S and foreign corporate debt securities
Long-term marketable securities
Marketable securities - long-term	14,686
Recurring | Level 2 | Money market fund
Cash equivalents
Cash equivalents	0	0
Recurring | Level 3
Cash equivalents
Cash equivalents	0	0
Short-term marketable securities
Short-term marketable securities	0	0
Long-term marketable securities
Marketable securities - long-term	0	0
Total assets measured at fair value	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
Marketable securities - long-term		0
Recurring | Level 3 | Asset-backed securities
Short-term marketable securities
Short-term marketable securities	0	0
Recurring | Level 3 | U.S. and foreign commercial paper
Short-term marketable securities
Short-term marketable securities	0	0
Recurring | Level 3 | U.S. treasury securities
Long-term marketable securities
Marketable securities - long-term	0	0
Recurring | Level 3 | U.S and foreign corporate debt securities
Long-term marketable securities
Marketable securities - long-term	0
Recurring | Level 3 | Money market fund
Cash equivalents
Cash equivalents	$ 0	$ 0

Other Accrued Expenses - Schedu

Other Accrued Expenses - Schedule of Other Accrued Expenses (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Accrued expenses:
Accrued compensation	$ 2,161	$ 6,426
Accrued professional fees and other	338	437
Total accrued expenses	$ 2,499	$ 6,863

Sale of Common Stock - Addition

Sale of Common Stock - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Aug. 31, 2020
Subsidiary Sale Of Stock [Line Items]
Initial public offering value of shares authorized			$ 300
2020 At the Market Offerings
Subsidiary Sale Of Stock [Line Items]
Number of shares sold	0	5,991,858
Net proceeds from the issuance of common stock through equity plans		$ 34.1
2020 At the Market Offerings | Maximum
Subsidiary Sale Of Stock [Line Items]
Initial public offering value of shares authorized			$ 100

Stock Plans and Stock-Based C_3

Stock Plans and Stock-Based Compensation - Additional Information (Details) - USD ($)	Jul. 31, 2021	Mar. 31, 2022	Jul. 31, 2021	Sep. 30, 2019	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021	May 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award
Shares reserved for issuance (in shares)								6,600,000
Weighted-average grant-date fair value of options granted					$ 1.63	$ 3.15
Options exercised					0	0
Stock-based compensation expense					$ 1,443,000	$ (286,000)
Unrecognized stock-based compensation expense		$ 10,900,000			$ 10,900,000
Unrecognized stock-based compensation expense expected to be recognized, term					1 year 9 months 18 days
2018 ESPP
Share-based Compensation Arrangement by Share-based Payment Award
Number of common stock purchased by employees					0	0
RSUs
Share-based Compensation Arrangement by Share-based Payment Award
Total fair value of awards vested and settled					$ 1,100,000	$ 2,500,000
Total intrinsic value of awards vested and settled					$ 200,000	$ 600,000
Granted					730,275
Forfeited					54,573
Outstanding awards		1,553,755			1,553,755		970,339
RSUs | Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award
Granted				100,000
Forfeited	25,000					25,000
Outstanding awards		50,000			50,000
Total fair value of awards					$ 400,000
Stock-based compensation expense					$ 0
RSUs | Employees Including Executive Officers
Share-based Compensation Arrangement by Share-based Payment Award
Granted		255,000	324,214
Total fair value of awards		$ 400,000	$ 1,200,000
Stock-based compensation expense			$ 0
Stock-based compensation arrangement by share-based payment award, requisite service period		1 year 6 months
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award
Shares reserved for issuance (in shares)								1,300,000

Stock Plans and Stock-Based C_4

Stock Plans and Stock-Based Compensation - Summary of Stock Option Activity and Related Information (Details) - Options - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Number of Shares
Options, Outstanding at beginning of period	6,161,901
Option, Granted	1,479,550
Option, Forfeited	(141,264)
Option, Expired	(24,311)
Option, Outstanding at end of period	7,475,876	6,161,901
Options vested and exercisable	4,120,830
Weighted Average Exercise Price Per Share
Options, Outstanding at beginning of period	$ 11.77
Option, Granted	2.29
Option, Forfeited	16.46
Option, Expired	26.86
Option, Outstanding at end of period	9.76	$ 11.77
Options vested and exercisable	$ 12.87
Options Outstanding, Weighted Average Remaining Contractual Term (Years)	6 years 10 months 24 days	6 years 4 months 24 days
Options Vested and Exercisable, Weighted Average Remaining Contractual Term (Years)	5 years 1 month 6 days
Total Intrinsic Value
Option, Outstanding	$ 6	$ 53

Stock Plans and Stock-Based C_5

Stock Plans and Stock-Based Compensation - Summary of Restricted Stock Units and Related Information (Details) - RSUs	3 Months Ended
	Mar. 31, 2022$ / sharesshares
Number of Shares
Beginning of period | shares	970,339
Granted | shares	730,275
Vested | shares	(92,286)
Forfeited | shares	(54,573)
Ending of period | shares	1,553,755
Weighted Average Fair Value Per RSU at Grant Price
Beginning of period | $ / shares	$ 7.04
Granted | $ / shares	2.30
Vested | $ / shares	12.10
Forfeited | $ / shares	6.81
Ending of period | $ / shares	$ 4.96

Stock Plans and Stock-Based C_6

Stock Plans and Stock-Based Compensation - Summary of Assumptions Used to Estimate Fair Values of Stock Options Grants (Details) - $ / shares	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
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	$ 1.53	$ 4.33
Expected volatility	79.20%	81.40%
Risk-free rate	1.41%	0.50%
Expected term (years)	5 years 6 months	5 years 6 months
Maximum
Share-based Compensation Arrangement by Share-based Payment Award
Exercise price	$ 2.45	$ 5.79
Expected volatility	81.60%	91.20%
Risk-free rate	2.48%	1.37%
Expected term (years)	7 years	7 years

Stock Plans and Stock-Based C_7

Stock Plans and Stock-Based Compensation -Schedule of Recognized Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Compensation expense:
Stock-based compensation expense	$ 1,443	$ (286)
Research and Development
Compensation expense:
Stock-based compensation expense	778	(2,091)
General and Administrative
Compensation expense:
Stock-based compensation expense	$ 665	$ 1,805

Stock Plans and Stock-Based C_8

Stock Plans and Stock-Based Compensation -Schedule of Stock-Based Compensation Expense (Parenthetical) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Compensation expense:
Stock-based compensation expense	$ 1,443	$ (286)
Terminated Employees
Compensation expense:
Stock-based compensation expense	(3,600)
Wind-down of Microbiome Program
Compensation expense:
Stock-based compensation expense	$ (2,700)

Collaboration Agreements - Addi

Collaboration Agreements - Additional Information (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Research And Development Arrangement Contract To Perform For Others [Line Items]
Deferred revenue	$ 2,733,000		$ 2,733,000
Research and development expense	17,205,000	$ 18,554,000
BeiGene Agreement
Research And Development Arrangement Contract To Perform For Others [Line Items]
Deferred revenue	2,700,000		2,700,000
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		$ 200,000
Arbutus Biopharma Agreement
Research And Development Arrangement Contract To Perform For Others [Line Items]
Research and development expense	600,000	$ 500,000
Antios Agreement
Research And Development Arrangement Contract To Perform For Others [Line Items]
Research and development expense	$ 100,000

Milestones and Research Agree_2

Milestones and Research Agreements - Additional Information (Details) - USD ($)	1 Months Ended	3 Months Ended
	Nov. 30, 2020	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Milestone and Research Agreements:
Potential milestone payment		$ 800,000
Milestone payment, diligence maintenance fees		100,000	$ 0
Accrued expenses		2,499,000		$ 6,863,000
Microbiome Targeted Colonic Delivery Program
Milestone and Research Agreements:
Accrued expenses		0	0
Door Pharma Agreement
Milestone and Research Agreements:
License agreement term	2 years
Research and development funding charges		700,000	400,000
Door Pharma Agreement | Maximum
Milestone and Research Agreements:
Success Based Milestones Payment		$ 0	$ 0