Assembly Biosciences (ASMB) 10-Q 9 Aug 22 2022 Q2 Quarterly report Financial data

Document And Entity Information

Document And Entity Information - shares	6 Months Ended
	Jun. 30, 2022	Aug. 04, 2022
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Jun. 30, 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	Q2
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		48,436,880
Entity Shell Company	false
Entity Emerging Growth Company	false
Entity Small Business	true

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Current assets
Cash and cash equivalents	$ 43,063	$ 45,627
Marketable securities - short-term	73,626	101,000
Accounts receivable from collaborations	523	336
Prepaid expenses and other current assets	7,082	7,241
Total current assets	124,294	154,204
Marketable securities - long-term	11,908	27,972
Property and equipment, net	899	1,139
Operating lease right-of-use (ROU) assets	4,711	6,042
Other assets	1,635	1,703
Total assets	143,447	191,060
Current liabilities
Accounts payable	2,454	2,659
Accrued research and development expenses	4,446	3,400
Other accrued expenses	4,750	6,863
Operating lease liabilities - short-term	3,311	3,151
Total current liabilities	14,961	16,073
Deferred revenue	2,733	2,733
Operating lease liabilities - long-term	1,773	3,325
Total liabilities	19,467	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; 150,000,000 and 100,000,000 shares authorized as of June 30, 2022 and December 31, 2021, respectively; 48,362,736 and 48,120,437 shares issued and outstanding as of June 30, 2022 and December 31, 2021, respectively	48	48
Additional paid-in capital	803,910	800,728
Accumulated other comprehensive loss	(998)	(419)
Accumulated deficit	(678,980)	(631,428)
Total stockholders' equity	123,980	168,929
Total liabilities and stockholders' equity	$ 143,447	$ 191,060

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Jun. 30, 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	150,000,000	100,000,000
Common stock, shares issued	48,362,736	48,120,437
Common stock, shares outstanding	48,362,736	48,120,437

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Operating expenses
Research and development	$ 17,792	$ 16,749	$ 34,997	$ 35,303
General and administrative	6,781	6,917	12,738	15,621
Total operating expenses	24,573	23,666	47,735	50,924
Loss from operations	(24,573)	(23,666)	(47,735)	(50,924)
Other income
Interest and other income, net	112	71	183	129
Total other income	112	71	183	129
Net loss	(24,461)	(23,595)	(47,552)	(50,795)
Other comprehensive loss
Unrealized loss on marketable securities	(90)	(2)	(579)	(3)
Comprehensive loss	$ (24,551)	$ (23,597)	$ (48,131)	$ (50,798)
Net loss per share, basic	$ (0.51)	$ (0.55)	$ (0.99)	$ (1.23)
Net loss per share, diluted	$ (0.51)	$ (0.55)	$ (0.99)	$ (1.23)
Weighted average common shares outstanding, basic	48,293,495	42,876,268	48,208,735	41,286,831
Weighted average common shares outstanding, diluted	48,293,495	42,876,268	48,208,735	41,286,831

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 Income (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	40,152	$ 8	40,144
Issuance of common stock under at-the-market (ATM) equity offering program, net of issuance costs (share)		7,449,901
Issuance of common stock under Employee Stock Purchase Plan (ESPP)	144		144
Issuance of common stock under Employee Stock Purchase Plan (ESPP) (in shares)		42,803
Issuance of shares of common stock for settlement of restricted stock units (RSUs) (in shares)		151,054
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)		2,108,621
Unrealized loss on marketable debt securities	(3)			(3)
Stock-based compensation	1,718		1,718
Net loss	(50,795)				(50,795)
Balance at Jun. 30, 2021	231,794	$ 44	784,391	(273)	(552,368)
Balance (in shares) at Jun. 30, 2021		43,779,059
Balance at Mar. 31, 2021	247,244	$ 40	776,248	(271)	(528,773)
Balance (in shares) at Mar. 31, 2021		40,104,684
Issuance of common stock under at-the-market (ATM) equity offering program, net of issuance costs	6,015	$ 2	6,013
Issuance of common stock under at-the-market (ATM) equity offering program, net of issuance costs (share)		1,458,043
Issuance of common stock under Employee Stock Purchase Plan (ESPP)	144		144
Issuance of common stock under Employee Stock Purchase Plan (ESPP) (in shares)		42,803
Issuance of shares of common stock for settlement of restricted stock units (RSUs) (in shares)		64,908
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)		2,108,621
Unrealized loss on marketable debt securities	(2)			(2)
Stock-based compensation	1,988		1,988
Net loss	(23,595)				(23,595)
Balance at Jun. 30, 2021	231,794	$ 44	784,391	(273)	(552,368)
Balance (in shares) at Jun. 30, 2021		43,779,059
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 common stock under Employee Stock Purchase Plan (ESPP)	177		177
Issuance of common stock under Employee Stock Purchase Plan (ESPP) (in shares)		134,888
Issuance of shares of common stock for settlement of restricted stock units (RSUs) (in shares)		107,411
Unrealized loss on marketable debt securities	(579)			(579)
Stock-based compensation	3,005		3,005
Net loss	(47,552)				(47,552)
Balance at Jun. 30, 2022	123,980	$ 48	803,910	(998)	(678,980)
Balance (in shares) at Jun. 30, 2022		48,362,736
Balance at Mar. 31, 2022	146,791	$ 48	802,170	(908)	(654,519)
Balance (in shares) at Mar. 31, 2022		48,132,937
Issuance of common stock under Employee Stock Purchase Plan (ESPP)	177		177
Issuance of common stock under Employee Stock Purchase Plan (ESPP) (in shares)		134,888
Issuance of shares of common stock for settlement of restricted stock units (RSUs) (in shares)		94,911
Unrealized loss on marketable debt securities	(90)			(90)
Stock-based compensation	1,563		1,563
Net loss	(24,461)				(24,461)
Balance at Jun. 30, 2022	$ 123,980	$ 48	$ 803,910	$ (998)	$ (678,980)
Balance (in shares) at Jun. 30, 2022		48,362,736

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Cash flows from operating activities
Net loss	$ (47,552)	$ (50,795)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	240	227
Stock-based compensation	3,024	1,700
Net amortization of investments in marketable debt securities	214	249
Non-cash rent expense	1,784	2,037
Loss on disposal of property and equipment	0	1,625
Changes in operating assets and liabilities:
Accounts receivable from collaboration	(187)	933
Prepaid expenses and other current assets	159	666
Other assets	68	299
Accounts payable	(205)	(1,732)
Accrued research and development expenses	1,046	(768)
Other accrued expenses	(2,132)	(7,649)
Operating lease liabilities	(1,846)	(1,944)
Net cash used in operating activities	(45,387)	(55,152)
Cash flows from investing activities
Purchases of marketable securities	(15,854)	(84,800)
Proceeds from maturities of marketable securities	46,500	98,950
Proceeds from sale of marketable securities	12,000	3,000
Purchases of property and equipment	0	(3,078)
Proceeds from sale of property and equipment	0	857
Net cash provided by investing activities	42,646	14,929
Cash flows from financing activities
Proceeds from the issuance of common stock under ESPP	177	144
Proceeds from the issuance of common stock under ATM equity offering program, net of issuance costs	0	40,152
Net cash provided by financing activities	177	40,296
Net (decrease) increase in cash and cash equivalents	(2,564)	73
Cash and cash equivalents at the beginning of the period	45,627	59,444
Cash and cash equivalents at the end of the period	43,063	59,517
Supplemental non-cash investing and financing activities
Operating lease liabilities arising from obtaining ROU assets	171	126
Remeasurement of lease liabilities arising from modification of ROU assets	$ 0	$ (788)

Nature of Business

Nature of Business	6 Months Ended
	Jun. 30, 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. 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 early-stage programs evaluating (1) a novel small molecule approach to inhibit entry for both HBV and hepatitis delta viruses (HDV), (2) a novel, small molecule interferon-α receptor (IFNAR) agonist designed to selectively activate the interferon-α pathway within the liver and offer the convenience of oral dosing and (3) two additional undisclosed viral targets. 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	6 Months Ended
	Jun. 30, 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 and six months ended June 30, 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 nonclinical studies were largely unaffected, but as the pandemic has continued, its impacts have increased. Certain nonclinical animal studies and shipping of compounds necessary for the Company’s research programs have been delayed, and conduct of Study 203, which is currently in the process of being closed, has also been impacted by the shutdowns occurring in the first half of 2022 in China. The Company relies on contract research organizations (CROs), some of which are in China and India, and these CROs have experienced pandemic-related impacts from time to time. In addition to the Company’s CROs in China and India, the Company also contracts with a CRO in Ukraine, which shut down operations due to Russia’s invasion of Ukraine. Though this CRO has resumed operations, the Company has reallocated certain work to other global CROs incase the CRO shuts down operations again. Income Taxes Effective January 1, 2022, a provision of the Tax Cuts and Jobs Act (TCJA) took 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. This provision is not expected to have a significant impact to the consolidated financial statements. 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 June 30, Six Months Ended June 30, 2022 2021 2022 2021 Numerator: Net loss $ (24,461 ) $ (23,595 ) $ (47,552 ) $ (50,795 ) Denominator: Weighted average common shares and pre-funded warrants outstanding - basic and diluted (1) 48,293,495 42,876,268 48,208,735 41,286,831 Net loss per share - basic and diluted $ (0.51 ) $ (0.55 ) $ (0.99 ) $ (1.23 ) (1) Securities excluded from the computation of diluted net loss per share because including them would have been antidilutive are as follows: June 30, 2022 2021 Options to purchase common stock 7,370,204 6,538,401 Common stock subject to purchase under ESPP 92,555 40,690 Unvested RSUs 1,516,609 607,788 Total 8,979,368 7,186,879

Fair Value Measurements and Inv

Fair Value Measurements and Investments in Marketable Securities	6 Months Ended
	Jun. 30, 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): June 30, 2022 Amortized Cost Gross Unrealized Gain Gross Unrealized Loss Fair Value Cash equivalents Money market fund $ 39,718 $ — $ — $ 39,718 Total cash equivalents 39,718 — — 39,718 Short-term marketable securities U.S. and foreign corporate debt securities 15,736 — (326 ) 15,410 Asset-backed securities 16,882 — (60 ) 16,822 U.S. and foreign commercial paper 41,395 — (1 ) 41,394 Total short-term marketable securities 74,013 — (387 ) 73,626 Long-term marketable securities U.S. and foreign corporate debt securities 3,273 — (95 ) 3,178 U.S. treasury securities 8,973 — (243 ) 8,730 Total long-term marketable securities 12,246 — (338 ) 11,908 Total cash equivalents and marketable securities $ 125,977 $ — $ (725 ) $ 125,252 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 June 30, 2022 had contractual maturities of less than one year. Long-term marketable securities held as of June 30, 2022 had contractual maturities of at least one year but less than two years. Realized gains and losses for the three and six months ended June 30, 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 June 30, 2022. The following tables present the fair value of the Company’s financial assets measured at fair value on a recurring basis (in thousands): June 30, 2022 Level 1 Level 2 Level 3 Fair Value Cash equivalents Money market fund $ 39,718 $ — $ — $ 39,718 Total cash equivalents 39,718 — — 39,718 Short-term marketable securities U.S. and foreign corporate debt securities — 15,410 — 15,410 Asset-backed securities — 16,822 — 16,822 U.S. and foreign commercial paper — 41,394 — 41,394 Total short-term marketable securities — 73,626 — 73,626 Long-term marketable securities U.S. and foreign corporate debt securities — 3,178 — 3,178 U.S. treasury securities — 8,730 — 8,730 Total long-term marketable securities — 11,908 — 11,908 Total assets measured at fair value $ 39,718 $ 85,534 $ — $ 125,252 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	6 Months Ended
	Jun. 30, 2022
Payables And Accruals [Abstract]
Other Accrued Expenses	Note 4 – Other Accrued Expenses Other accrued expenses consist of the following (in thousands): June 30, December 31, 2022 2021 Accrued expenses: Accrued compensation $ 4,406 $ 6,426 Accrued professional fees and other 344 437 Total accrued expenses $ 4,750 $ 6,863

Stale of Common Stock

Stale of Common Stock	6 Months Ended
	Jun. 30, 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. The Company did not sell any shares of common stock under the 2020 ATM during the six months ended June 30, 2022. During the six months ended June 30, 2021, the Company sold 7,449,901 shares of common stock under the 2020 ATM, for which the Company received net proceeds of $40.2 million, after deducting commissions, fees and expenses.

Stock Plans and Stock-Based Com

Stock Plans and Stock-Based Compensation	6 Months Ended
	Jun. 30, 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 2022, 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 8,600,000 and an amendment and restatement to the Fifth Amended and Restated Certificate of Incorporation to increase the authorized number of shares of common stock to 150,000,000. As of June 30, 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 Amended and Restated Assembly Biosciences, Inc. 2018 Employee Stock Purchase Plan. Stock Plan Activity Stock Options A summary of the Company’s option activity and related information for the six months ended June 30, 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 1,736,150 2.21 Forfeited (527,847 ) 18.08 Outstanding as of June 30, 2022 7,370,204 $ 9.07 6.9 $ 98 Options vested and exercisable as of June 30, 2022 4,126,895 $ 12.05 5.1 $ — The weighted-average grant-date fair value of options granted was $1.57 and $3.12 during the six months ended June 30, 2022 and 2021, respectively. There were no options exercised during the three and six months ended June 30, 2022 or 2021. RSUs A summary of the Company’s RSUs and related information for the six months ended June 30, 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 2.10 Vested (107,411 ) 13.11 Forfeited (76,594 ) 6.08 Nonvested as of June 30, 2022 1,516,609 $ 4.28 The total fair value of RSUs vested and settled during the six months ended June 30, 2022 and 2021 was $1.4 million and $2.8 million, respectively. The total intrinsic value of RSUs vested and settled during the six months ended June 30, 2022 and 2021 was $0.2 million and $0.7 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 June 30, 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 June 30, 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 June 30, 2022. The Company recognized stock-based compensation expense of $0.1 million ESPP Employees purchased 134,888 and 42,803 shares of common stock under the 2018 ESPP during the six months ended June 30, 2022 and 2021, respectively. 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 June 30, Six Months Ended June 30, 2022 2021 2022 2021 Exercise price $1.68 - $2.06 $4.03 - $4.16 $1.53 - $2.45 $4.03 - $5.79 Expected volatility 78.9% - 81.7% 80.7% - 88.9% 78.9% - 81.7% 80.7% - 91.2% Risk-free rate 2.48% - 3.02% 0.93% - 1.34% 1.41% - 3.02% 0.50% - 1.37% Expected term (years) 5.5 - 7.5 5.5 - 7.5 5.5 - 7.5 5.5 - 7.5 Expected dividend yield 0% 0% 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 and stock appreciation rights was 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 June 30, Six Months Ended June 30, 2022 2021 2022 2021 Research and development $ 654 $ 743 $ 1,431 $ (1,348 ) (1) General and administrative 927 1,243 1,593 3,048 Total stock-based compensation expense $ 1,581 $ 1,986 $ 3,024 $ 1,700 (1) Includes the reversal of previously recognized stock-based compensation expense of $4.1 million related to forfeited awards of terminated employees, $2.7 million of which resulted from the wind-down of the Company’s Microbiome program in January 2021. As of June 30, 2022, there was $9.2 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 1.6 years.

Collaboration Agreements

Collaboration Agreements	6 Months Ended
	Jun. 30, 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 vebicorvir (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 June 30, 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 June 30, 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 and six months ended June 30, 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 June 30, 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, pharmacokinetics 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. Reimbursements and cost-sharing portions from Arbutus are reflected as a reduction of research and development expense when realized in the Company’s condensed consolidated statements of operations. During the three and six months ended June 30, 2022, the Company recognized a reduction of research and development expenses of $0.6 million and $1.2 million, respectively, under the Arbutus Agreement. During the three and six months ended June 30, 2021, the Company recognized a reduction of research and development expenses of $0.4 million and $0.8 million, respectively, under the Arbutus Agreement. 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 triple combination therapy using VBR and Antios’s active site polymerase inhibitor nucleotide ATI-2173 for the treatment of HBV. Assembly and Antios were individually responsible for the study’s manufacturing costs but equally shared the remaining costs of the study. Antios was responsible for conducting the clinical trial with Assembly reimbursing Antios its share of expenses. In May 2022, the Company was notified by Antios that ATI-2173 had been placed on clinical hold by the FDA following submission of a safety report involving a patient who received a triple combination of VBR, ATI-2173 and a nucleos(t)ide analog reverse transcriptase inhibitor. Due to the clinical hold, the Company terminated the Antios Agreement effective May 2022. During the three and six months ended June 30, 2022 , the Company incurred $0.2 million and $0.3 million, respectively, in research and development expenses under the Antios Agreement.

Milestones and Research Agreeme

Milestones and Research Agreements	6 Months Ended
	Jun. 30, 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 six months ended June 30, 2022. No amounts were paid during the six months ended June 30, 2021. Door Pharma Agreement In November 2020, the Company and Door Pharmaceuticals, LLC (Door Pharma) entered into an exclusive, two-year The Company terminated the Door Pharma Agreement in May 2022, effective September 2022, . Under the terms of the Door Pharma Agreement, the Company is obligated to continue to reimburse Door Pharma for certain research and development costs through September 2022. Upon effectiveness of the termination, such reimbursements will cease. During the three and six months ended June 30, 2022, the Company incurred research and development funding of $0.5 million and $1.2 million , respectively, under the Door Pharma Agreement. During the three and six months ended June 30, 2021, the Company incurred research and development funding of $0.5 million and $0.8 million, respectively, under the Door Pharma Agreement. No success-based milestones were determined to have occurred under this agreement during the six months ended June 30, 2022 or 2021.

Subsequent Events

Subsequent Events	6 Months Ended
	Jun. 30, 2022
Subsequent Events [Abstract]
Subsequent Events	Note 9 – Subsequent Events In July 2022, the Company’s Board of Directors approved a strategic plan to discontinue clinical development of the Company’s first-generation core inhibitor, VBR, and prioritize its resources on its next-generation core inhibitors, ABI-H3733 and ABI-4334, and research activities, including a small molecule HBV and HDV entry inhibitor, a small molecule interferon-α receptor agonist and two additional undisclosed viral targets. The Company intends to align the organization to reflect its refocused pipeline and reduce its workforce by approximately 30%. The Company accrued restructuring charges of $1.0 million as of June 30, 2022 related to severance benefits to executive officers impacted by the restructuring as the severance benefits in their employment agreements were deemed to be probable of being paid. The Company expects to incur an additional $0.7 million in one-time termination severance payments and other employee-related costs associated with the restructuring, which the Company expects to recognize in the second half of 2022. This total of $1.7 million represents the total amount expected to be incurred in connection with the restructuring and is expected to be fully paid by mid-2023. In July 2022, the Company's Board of Directors also approved $2.5 million in retention bonuses to non-executive officers, 525,000 RSUs with performance-based vesting conditions with a grant date fair value of $1.1 million to executive officers and 2,288,200 options with a grant date fair value of $3.2 million to all retained employees, all of which will be recognized in future quarters. The $1.0 million accrued restructuring charges as of June 30, 2022 are included in other accrued expenses on the Company’s condensed consolidated balance sheet, of which $0.5 million are included in research and development expenses and $0.5 million in general and administrative expenses in the condensed consolidated statement of operations and comprehensive loss for the three and six months ended June 30, 2022.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 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 and six months ended June 30, 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 nonclinical studies were largely unaffected, but as the pandemic has continued, its impacts have increased. Certain nonclinical animal studies and shipping of compounds necessary for the Company’s research programs have been delayed, and conduct of Study 203, which is currently in the process of being closed, has also been impacted by the shutdowns occurring in the first half of 2022 in China. The Company relies on contract research organizations (CROs), some of which are in China and India, and these CROs have experienced pandemic-related impacts from time to time. In addition to the Company’s CROs in China and India, the Company also contracts with a CRO in Ukraine, which shut down operations due to Russia’s invasion of Ukraine. Though this CRO has resumed operations, the Company has reallocated certain work to other global CROs incase the CRO shuts down operations again.
Income Taxes	Income Taxes Effective January 1, 2022, a provision of the Tax Cuts and Jobs Act (TCJA) took 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. This provision is not expected to have a significant impact to the consolidated financial statements.
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 June 30, Six Months Ended June 30, 2022 2021 2022 2021 Numerator: Net loss $ (24,461 ) $ (23,595 ) $ (47,552 ) $ (50,795 ) Denominator: Weighted average common shares and pre-funded warrants outstanding - basic and diluted (1) 48,293,495 42,876,268 48,208,735 41,286,831 Net loss per share - basic and diluted $ (0.51 ) $ (0.55 ) $ (0.99 ) $ (1.23 ) (1) Securities excluded from the computation of diluted net loss per share because including them would have been antidilutive are as follows: June 30, 2022 2021 Options to purchase common stock 7,370,204 6,538,401 Common stock subject to purchase under ESPP 92,555 40,690 Unvested RSUs 1,516,609 607,788 Total 8,979,368 7,186,879

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	6 Months Ended
	Jun. 30, 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 June 30, Six Months Ended June 30, 2022 2021 2022 2021 Numerator: Net loss $ (24,461 ) $ (23,595 ) $ (47,552 ) $ (50,795 ) Denominator: Weighted average common shares and pre-funded warrants outstanding - basic and diluted (1) 48,293,495 42,876,268 48,208,735 41,286,831 Net loss per share - basic and diluted $ (0.51 ) $ (0.55 ) $ (0.99 ) $ (1.23 )
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	(1) Securities excluded from the computation of diluted net loss per share because including them would have been antidilutive are as follows: June 30, 2022 2021 Options to purchase common stock 7,370,204 6,538,401 Common stock subject to purchase under ESPP 92,555 40,690 Unvested RSUs 1,516,609 607,788 Total 8,979,368 7,186,879

Fair Value Measurements and I_2

Fair Value Measurements and Investments in Marketable Securities (Tables)	6 Months Ended
	Jun. 30, 2022
Investments Debt And Equity Securities [Abstract]
Schedule of Investments in Marketable Securities	Investments in marketable securities consisted of the following (in thousands): June 30, 2022 Amortized Cost Gross Unrealized Gain Gross Unrealized Loss Fair Value Cash equivalents Money market fund $ 39,718 $ — $ — $ 39,718 Total cash equivalents 39,718 — — 39,718 Short-term marketable securities U.S. and foreign corporate debt securities 15,736 — (326 ) 15,410 Asset-backed securities 16,882 — (60 ) 16,822 U.S. and foreign commercial paper 41,395 — (1 ) 41,394 Total short-term marketable securities 74,013 — (387 ) 73,626 Long-term marketable securities U.S. and foreign corporate debt securities 3,273 — (95 ) 3,178 U.S. treasury securities 8,973 — (243 ) 8,730 Total long-term marketable securities 12,246 — (338 ) 11,908 Total cash equivalents and marketable securities $ 125,977 $ — $ (725 ) $ 125,252 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): June 30, 2022 Level 1 Level 2 Level 3 Fair Value Cash equivalents Money market fund $ 39,718 $ — $ — $ 39,718 Total cash equivalents 39,718 — — 39,718 Short-term marketable securities U.S. and foreign corporate debt securities — 15,410 — 15,410 Asset-backed securities — 16,822 — 16,822 U.S. and foreign commercial paper — 41,394 — 41,394 Total short-term marketable securities — 73,626 — 73,626 Long-term marketable securities U.S. and foreign corporate debt securities — 3,178 — 3,178 U.S. treasury securities — 8,730 — 8,730 Total long-term marketable securities — 11,908 — 11,908 Total assets measured at fair value $ 39,718 $ 85,534 $ — $ 125,252 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)	6 Months Ended
	Jun. 30, 2022
Payables And Accruals [Abstract]
Schedule of Other Accrued Expenses	June 30, December 31, 2022 2021 Accrued expenses: Accrued compensation $ 4,406 $ 6,426 Accrued professional fees and other 344 437 Total accrued expenses $ 4,750 $ 6,863

Stock Plans and Stock-Based C_2

Stock Plans and Stock-Based Compensation (Tables)	6 Months Ended
	Jun. 30, 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 six months ended June 30, 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 1,736,150 2.21 Forfeited (527,847 ) 18.08 Outstanding as of June 30, 2022 7,370,204 $ 9.07 6.9 $ 98 Options vested and exercisable as of June 30, 2022 4,126,895 $ 12.05 5.1 $ —
Summary of Restricted Stock Units and Related Information	A summary of the Company’s RSUs and related information for the six months ended June 30, 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 2.10 Vested (107,411 ) 13.11 Forfeited (76,594 ) 6.08 Nonvested as of June 30, 2022 1,516,609 $ 4.28
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 June 30, Six Months Ended June 30, 2022 2021 2022 2021 Exercise price $1.68 - $2.06 $4.03 - $4.16 $1.53 - $2.45 $4.03 - $5.79 Expected volatility 78.9% - 81.7% 80.7% - 88.9% 78.9% - 81.7% 80.7% - 91.2% Risk-free rate 2.48% - 3.02% 0.93% - 1.34% 1.41% - 3.02% 0.50% - 1.37% Expected term (years) 5.5 - 7.5 5.5 - 7.5 5.5 - 7.5 5.5 - 7.5 Expected dividend yield 0% 0% 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 June 30, Six Months Ended June 30, 2022 2021 2022 2021 Research and development $ 654 $ 743 $ 1,431 $ (1,348 ) (1) General and administrative 927 1,243 1,593 3,048 Total stock-based compensation expense $ 1,581 $ 1,986 $ 3,024 $ 1,700 (1) Includes the reversal of previously recognized stock-based compensation expense of $4.1 million related to forfeited awards of terminated employees, $2.7 million of which resulted from the wind-down of the Company’s Microbiome program in January 2021.

Nature of Business - Additional

Nature of Business - Additional Information (Details)	6 Months Ended
	Jun. 30, 2022 segment product
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)	6 Months Ended
	Jun. 30, 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		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Numerator:
Net loss	$ (24,461)	$ (23,595)	$ (47,552)	$ (50,795)
Denominator:
Weighted average common shares and pre-funded warrants outstanding - basic	48,293,495	42,876,268	48,208,735	41,286,831
Weighted average common shares and pre-funded warrants outstanding - diluted	48,293,495	42,876,268	48,208,735	41,286,831
Net loss per share - basic	$ (0.51)	$ (0.55)	$ (0.99)	$ (1.23)
Net loss per share - diluted	$ (0.51)	$ (0.55)	$ (0.99)	$ (1.23)

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share (Details) - shares	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities excluded from computation of loss per share	8,979,368	7,186,879
Options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities excluded from computation of loss per share	7,370,204	6,538,401
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	92,555	40,690
Unvested RSUs
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities excluded from computation of loss per share	1,516,609	607,788

Fair Value Measurements and I_3

Fair Value Measurements and Investments in Marketable Securities - Schedule of Investments in Marketable Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Investments in marketable securities:
Amortized Cost	$ 43,063	$ 45,627
Fair Value	73,626	101,000
Amortized Cost	125,977	171,625
Gross Unrealized Gain	0	0
Gross Unrealized Loss	(725)	(146)
Fair Value	125,252	171,479
Cash equivalents
Investments in marketable securities:
Amortized Cost	39,718	42,507
Gross Unrealized Gain	0	0
Gross Unrealized Loss	0	0
Fair Value	39,718	42,507
Short-term marketable securities
Investments in marketable securities:
Amortized Cost	74,013	101,041
Gross Unrealized Gain	0	0
Gross Unrealized Loss	(387)	(41)
Fair Value	73,626	101,000
Long-term marketable securities
Investments in marketable securities:
Amortized Cost	12,246	28,077
Gross Unrealized Gain	0	0
Gross Unrealized Loss	(338)	(105)
Fair Value	11,908	27,972
Money market fund | Cash equivalents
Investments in marketable securities:
Amortized Cost	39,718	42,507
Gross Unrealized Gain	0	0
Gross Unrealized Loss	0	0
Fair Value	39,718	42,507
U.S and foreign corporate debt securities | Short-term marketable securities
Investments in marketable securities:
Amortized Cost	15,736	7,015
Gross Unrealized Gain	0	0
Gross Unrealized Loss	(326)	(2)
Fair Value	15,410	7,013
U.S and foreign corporate debt securities | Long-term marketable securities
Investments in marketable securities:
Amortized Cost	3,273	19,117
Gross Unrealized Gain	0	0
Gross Unrealized Loss	(95)	(74)
Fair Value	3,178	19,043
Asset-backed securities | Short-term marketable securities
Investments in marketable securities:
Amortized Cost	16,882	29,097
Gross Unrealized Gain	0	0
Gross Unrealized Loss	(60)	(38)
Fair Value	16,822	29,059
U.S. and foreign commercial paper | Short-term marketable securities
Investments in marketable securities:
Amortized Cost	41,395	64,929
Gross Unrealized Gain	0	0
Gross Unrealized Loss	(1)	(1)
Fair Value	41,394	64,928
U.S. treasury securities | Long-term marketable securities
Investments in marketable securities:
Amortized Cost	8,973	8,960
Gross Unrealized Gain	0	0
Gross Unrealized Loss	(243)	(31)
Fair Value	$ 8,730	$ 8,929

Fair Value Measurements and I_4

Fair Value Measurements and Investments in Marketable Securities - Additional Information (Details) - USD ($)	6 Months Ended
	Jun. 30, 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	Jun. 30, 2022	Dec. 31, 2021
Short-term marketable securities
Short-term marketable securities	$ 73,626	$ 101,000
Long-term marketable securities
Marketable securities - long-term	11,908	27,972
Recurring
Cash equivalents
Cash equivalents	39,718	42,507
Short-term marketable securities
Short-term marketable securities	73,626	101,000
Long-term marketable securities
Marketable securities - long-term	11,908	27,972
Total assets measured at fair value	125,252	171,479
Recurring | U.S and foreign corporate debt securities
Short-term marketable securities
Short-term marketable securities	15,410	7,013
Long-term marketable securities
Marketable securities - long-term		19,043
Recurring | Asset-backed securities
Short-term marketable securities
Short-term marketable securities	16,822	29,059
Recurring | U.S. and foreign commercial paper
Short-term marketable securities
Short-term marketable securities	41,394	64,928
Recurring | U.S. treasury securities
Long-term marketable securities
Marketable securities - long-term	8,730	8,929
Recurring | U.S and foreign corporate debt securities
Long-term marketable securities
Marketable securities - long-term	3,178
Recurring | Money market fund
Cash equivalents
Cash equivalents	39,718	42,507
Recurring | Level 1
Cash equivalents
Cash equivalents	39,718	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	39,718	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	39,718	42,507
Recurring | Level 2
Cash equivalents
Cash equivalents	0	0
Short-term marketable securities
Short-term marketable securities	73,626	101,000
Long-term marketable securities
Marketable securities - long-term	11,908	27,972
Total assets measured at fair value	85,534	128,972
Recurring | Level 2 | U.S and foreign corporate debt securities
Short-term marketable securities
Short-term marketable securities	15,410	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	16,822	29,059
Recurring | Level 2 | U.S. and foreign commercial paper
Short-term marketable securities
Short-term marketable securities	41,394	64,928
Recurring | Level 2 | U.S. treasury securities
Long-term marketable securities
Marketable securities - long-term	8,730	8,929
Recurring | Level 2 | U.S and foreign corporate debt securities
Long-term marketable securities
Marketable securities - long-term	3,178
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	Jun. 30, 2022	Dec. 31, 2021
Accrued expenses:
Accrued compensation	$ 4,406	$ 6,426
Accrued professional fees and other	344	437
Total accrued expenses	$ 4,750	$ 6,863

Sale of Common Stock - Addition

Sale of Common Stock - Additional Information (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2022	Jun. 30, 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	7,449,901
Net proceeds from the issuance of common stock through equity plans		$ 40.2
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 ($)		1 Months Ended			3 Months Ended			6 Months Ended
	Jul. 31, 2021	Mar. 31, 2022	Jul. 31, 2021	Sep. 30, 2019	Jun. 30, 2022	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2022	Jun. 30, 2021	May 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award
Shares reserved for issuance (in shares)										8,600,000
Weighted-average grant-date fair value of options granted								$ 1.57	$ 3.12
Options exercised					0	0		0	0
Stock-based compensation expense					$ 1,581,000	$ 1,986,000		$ 3,024,000	$ 1,700,000
Unrecognized stock-based compensation expense					$ 9,200,000			$ 9,200,000
Unrecognized stock-based compensation expense expected to be recognized, term								1 year 7 months 6 days
2018 ESPP
Share-based Compensation Arrangement by Share-based Payment Award
Issuance of common stock under Employee Stock Purchase Plan (ESPP) (in shares)								134,888	42,803
RSUs
Share-based Compensation Arrangement by Share-based Payment Award
Total fair value of awards vested and settled								$ 1,400,000	$ 2,800,000
Total intrinsic value of awards vested and settled								$ 200,000	$ 700,000
Granted								730,275
Forfeited								76,594
Outstanding awards					1,516,609			1,516,609			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		$ 100,000			$ 100,000
Stock-based compensation arrangement by share-based payment award, requisite service period		1 year 6 months
Fifth Amended and Restated Certificate of Incorporation
Share-based Compensation Arrangement by Share-based Payment Award
Shares reserved for issuance (in shares)										150,000,000

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	6 Months Ended	12 Months Ended
	Jun. 30, 2022	Dec. 31, 2021
Number of Shares
Options, Outstanding at beginning of period	6,161,901
Option, Granted	1,736,150
Option, Forfeited	(527,847)
Option, Outstanding at end of period	7,370,204	6,161,901
Options vested and exercisable	4,126,895
Weighted Average Exercise Price Per Share
Options, Outstanding at beginning of period	$ 11.77
Option, Granted	2.21
Option, Forfeited	18.08
Option, Outstanding at end of period	9.07	$ 11.77
Options vested and exercisable	$ 12.05
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	$ 98	$ 53

Stock Plans and Stock-Based C_5

Stock Plans and Stock-Based Compensation - Summary of Restricted Stock Units and Related Information (Details) - RSUs	6 Months Ended
	Jun. 30, 2022 $ / shares shares
Number of Shares
Beginning of period | shares	970,339
Granted | shares	730,275
Vested | shares	(107,411)
Forfeited | shares	(76,594)
Ending of period | shares	1,516,609
Weighted Average Fair Value Per RSU at Grant Price
Beginning of period | $ / shares	$ 7.04
Granted | $ / shares	2.10
Vested | $ / shares	13.11
Forfeited | $ / shares	6.08
Ending of period | $ / shares	$ 4.28

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		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Share-based Compensation Arrangement by Share-based Payment Award
Expected dividend yield	0%	0%	0%	0%
Minimum
Share-based Compensation Arrangement by Share-based Payment Award
Exercise price	$ 1.68	$ 4.03	$ 1.53	$ 4.03
Expected volatility	78.90%	80.70%	78.90%	80.70%
Risk-free rate	2.48%	0.93%	1.41%	0.50%
Expected term (years)	5 years 6 months	5 years 6 months	5 years 6 months	5 years 6 months
Maximum
Share-based Compensation Arrangement by Share-based Payment Award
Exercise price	$ 2.06	$ 4.16	$ 2.45	$ 5.79
Expected volatility	81.70%	88.90%	81.70%	91.20%
Risk-free rate	3.02%	1.34%	3.02%	1.37%
Expected term (years)	7 years 6 months	7 years 6 months	7 years 6 months	7 years 6 months

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		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Compensation expense:
Stock-based compensation expense	$ 1,581	$ 1,986	$ 3,024	$ 1,700
Research and Development
Compensation expense:
Stock-based compensation expense	654	743	1,431	(1,348)
General and Administrative
Compensation expense:
Stock-based compensation expense	$ 927	$ 1,243	$ 1,593	$ 3,048

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		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Compensation expense:
Stock-based compensation expense	$ 1,581	$ 1,986	$ 3,024	$ 1,700
Terminated Employees
Compensation expense:
Stock-based compensation expense			(4,100)
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		6 Months Ended		12 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Research And Development Arrangement Contract To Perform For Others [Line Items]
Deferred revenue	$ 2,733,000		$ 2,733,000		$ 2,733,000
Research and development expense	17,792,000	$ 16,749,000	34,997,000	$ 35,303,000
BeiGene Agreement
Research And Development Arrangement Contract To Perform For Others [Line Items]
Deferred revenue	2,700,000		2,700,000		2,700,000
Research and development expense	0	0	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	$ 400,000	1,200,000	$ 800,000
Antios Agreement
Research And Development Arrangement Contract To Perform For Others [Line Items]
Research and development expense	$ 200,000		$ 300,000

Milestones and Research Agree_2

Milestones and Research Agreements - Additional Information (Details) - USD ($)	1 Months Ended	3 Months Ended		6 Months Ended
	Nov. 30, 2020	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Milestone and Research Agreements:
Potential milestone payment		$ 800,000		$ 800,000
Milestone payment, diligence maintenance fees				100,000	$ 0
Door Pharma Agreement
Milestone and Research Agreements:
License agreement term	2 years
Research and development funding charges		$ 500,000	$ 500,000	1,200,000	800,000
Door Pharma Agreement | Maximum
Milestone and Research Agreements:
Success Based Milestones Payment				$ 0	$ 0

Subsequent Events - Additional

Subsequent Events - Additional Information (Details) $ / shares in Millions, $ in Millions	1 Months Ended	3 Months Ended	6 Months Ended
	Jul. 31, 2022 USD ($) $ / shares shares	Jun. 30, 2022 USD ($)	Jun. 30, 2022 USD ($) Target
Subsequent Event [Line Items]
Percentage of reduction in workforce			30%
Number of additional undisclosed viral targets | Target			2
Accrued restructuring charges			$ 1
Severance payments		$ 0.7	0.7
Restructuring and is expected amount, total			1.7
Other Accrued Expenses
Subsequent Event [Line Items]
Accrued restructuring charges		1	1
Research and Development Expenses
Subsequent Event [Line Items]
Accrued restructuring charges		0.5	0.5
General and Administrative Expenses
Subsequent Event [Line Items]
Accrued restructuring charges		$ 0.5	$ 0.5
Subsequent Event | Non-Executive Officers
Subsequent Event [Line Items]
Retention bonuses costs	$ 2.5
Subsequent Event | Executive Officer
Subsequent Event [Line Items]
Performance-based vesting conditions | shares	525,000
Grant date fair value non options | $ / shares	$ 1.1
Subsequent Event | Retained Employees
Subsequent Event [Line Items]
Options | shares	2,288,200
Options grant date fair value | $ / shares	$ 3.2