0000950170-23-017931 | 10-Q | XBRL Viewer

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Document And Entity Information - shares	3 Months Ended
Document And Entity Information - shares	Mar. 31, 2023	May 01, 2023
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Mar. 31, 2023
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	2023
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		52,121,309
Entity Shell Company	false
Entity Emerging Growth Company	false
Entity Small Business	true

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Current assets
Cash and cash equivalents	$ 43,482	$ 52,418
Marketable securities - short-term	29,534	39,192
Accounts receivable from collaboration	717	944
Prepaid expenses and other current assets	6,011	4,413
Total current assets	79,744	96,967
Property and equipment, net	619	743
Operating lease right-of-use (ROU) assets	2,419	3,195
Other assets	334	889
Total assets	83,116	101,794
Current liabilities
Accounts payable	1,224	2,493
Accrued research and development expenses	3,046	3,122
Other accrued expenses	3,154	7,317
Operating lease liabilities - short-term	2,546	3,364
Total current liabilities	9,970	16,296
Deferred revenue	2,733	2,733
Operating lease liabilities - long-term	80	101
Total liabilities	12,783	19,130
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 shares authorized as of March 31, 2023 and December 31, 2022; 52,015,268 and 48,894,973 shares issued and outstanding as of March 31, 2023 and December 31, 2022, respectively	52	49
Additional paid-in capital	814,264	807,938
Accumulated other comprehensive loss	(513)	(803)
Accumulated deficit	(743,470)	(724,520)
Total stockholders' equity	70,333	82,664
Total liabilities and stockholders' equity	$ 83,116	$ 101,794

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Mar. 31, 2023	Dec. 31, 2022
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	150,000,000
Common stock, shares issued	52,015,268	48,894,973
Common stock, shares outstanding	52,015,268	48,894,973

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Operating expenses
Research and development	$ 14,547	$ 17,205
General and administrative	5,012	5,957
Total operating expenses	19,559	23,162
Loss from operations	(19,559)	(23,162)
Other income
Interest and other income, net	609	71
Total other income	609	71
Net loss	(18,950)	(23,091)
Other comprehensive loss
Unrealized loss on marketable securities	290	(489)
Comprehensive loss	$ (18,660)	$ (23,580)
Net loss per share, basic	$ (0.37)	$ (0.48)
Net loss per share, diluted	$ (0.37)	$ (0.48)
Weighted average common shares outstanding, basic	51,012,450	48,123,930
Weighted average common shares outstanding, diluted	51,012,450	48,123,930

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, 2021	$ 168,929	$ 48	$ 800,728	$ (419)	$ (631,428)
Balance (in shares) at Dec. 31, 2021		48,120,437
Issuance of common stock for settlement of restricted stock units (RSUs) (in shares)		12,500
Unrealized gain (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
Balance at Dec. 31, 2022	82,664	$ 49	807,938	(803)	(724,520)
Balance (in shares) at Dec. 31, 2022		48,894,973
Issuance of common stock under at-the-market (ATM) equity offering program, net of issuance costs	4,492	$ 3	4,489
Issuance of common stock under at-the-market (ATM) equity offering program, net of issuance costs (in shares)		3,050,446
Issuance of common stock for settlement of restricted stock units (RSUs) (in shares)		69,849
Unrealized gain (loss) on marketable debt securities	290			290
Stock-based compensation	1,837		1,837
Net loss	(18,950)				(18,950)
Balance at Mar. 31, 2023	$ 70,333	$ 52	$ 814,264	$ (513)	$ (743,470)
Balance (in shares) at Mar. 31, 2023		52,015,268

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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- Definition

Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

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+ Details

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Cash flows from operating activities
Net loss	$ (18,950)	$ (23,091)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	124	120
Stock-based compensation	1,835	1,443
Net (accretion) amortization of investments in marketable debt securities	(52)	149
Non-cash rent expense	855	893
Changes in operating assets and liabilities:
Accounts receivable from collaboration	227	(188)
Prepaid expenses and other current assets	(1,598)	(12)
Other assets	555	(472)
Accounts payable	(1,269)	(1,252)
Accrued research and development expenses	(76)	196
Other accrued expenses	(4,161)	(4,365)
Operating lease liabilities	(918)	(923)
Net cash used in operating activities	(23,428)	(27,502)
Cash flows from investing activities
Proceeds from maturities of marketable securities	10,000	30,000
Proceeds from sale of marketable securities	0	7,000
Purchases of marketable securities	0	(3,951)
Net cash provided by investing activities	10,000	33,049
Cash flows from financing activities
Proceeds from the issuance of common stock under ATM equity offering program, net of issuance costs	4,492	0
Net cash provided by financing activities	4,492	0
Net (decrease) increase in cash and cash equivalents	(8,936)	(5,547)
Cash and cash equivalents at the beginning of the period	52,418	45,627
Cash and cash equivalents at the end of the period	$ 43,482	$ 51,174

Nature of Business

3 Months Ended

Mar. 31, 2023

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 biotechnology company developing innovative antiviral therapeutics with the potential to improve the lives of patients worldwide by targeting serious viral diseases, including high-recurrence genital herpes, transplant-related herpesviruses, chronic hepatitis delta virus (HDV) infection and chronic hepatitis B virus (HBV) infection. The Company operates in one segment and is headquartered in South San Francisco, California.

The Company has a broad research and development portfolio with multiple targets, including (1) a long-acting helicase inhibitor for the treatment of high-recurrence genital herpes, (2) a pan-herpes non-nucleoside polymerase inhibitor to treat multiple transplant-associated herpesvirus infections, (3) a small molecule approach to inhibit cell entry for both HDV and HBV, (4) a small molecule interferon-α receptor agonist designed to selectively activate the interferon-α pathway within the liver and offer the convenience of oral dosing and (5) small molecule core inhibitors that inhibit the HBV replication cycle and block the generation of covalently closed circular DNA (cccDNA).

Liquidity

The Company has not derived any revenue from product sales to date and currently has no approved products. Once a product has been developed, it will need to be approved for sale by the U.S. Food and Drug Administration (FDA) or an applicable foreign regulatory agency. Since inception, the Company’s operations have been financed primarily through the sale of equity securities, the proceeds from the exercise of warrants and stock options, the issuance of debt, and upfront payments related to collaboration agreements. The Company has incurred losses from operations since inception and expects to continue to incur substantial losses for the next several years as it continues its product development efforts. Management believes the Company currently has sufficient funds to meet its operating requirements for at least the next twelve months following the date 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, inflation or other factors could also adversely impact the Company’s ability to access capital when and as needed.

If the Company is unable to secure additional sources of funding, generate enough revenue from its collaborations, 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 Accounting Policies

3 Months Ended

Mar. 31, 2023

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, 2022, which are contained in the 2022 Annual Report. The results for the three

months ended March 31, 2023 are not necessarily indicative of results to be expected for the entire year ending December 31, 2023 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.

Significant 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.

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

The Company relies on contract research organizations (CROs), including one located in Ukraine which shut down operations due to Russia’s invasion. Though this CRO has resumed operations, the Company has reallocated certain work to other global CROs in case the CRO shuts down operations again.

U.S. and global financial markets have experienced volatility and disruption due to other macroeconomic and geopolitical events such as rising inflation, the risk of a recession, the ongoing conflict between Russia and Ukraine, as well as the ongoing impact of the COVID-19 pandemic. The Company cannot predict at this time to what extent, if at all, it and its employees, CROs, vendors and/or collaborators could potentially be negatively impacted by these events.

In April 2023, the Company announced it was evaluating potential partnering options for its core inhibitor portfolio. If the Company is unable to reach an agreement with a suitable collaboration partner for its core inhibitors or any such agreement has unfavorable terms, the Company may be unable to advance the product candidates through further clinical development.

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 could occur if securities or other contracts to issue common stock were exercised or converted into common stock or resulted in the issuance of common stock that then shared in the earnings of the entity unless inclusion of such shares would be anti-dilutive.

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,
	2023			2022
Numerator:
Net loss	$	(18,950	)	$	(23,091	)
Denominator:
Weighted average common shares outstanding - basic and diluted		51,012,450			48,123,930
Net loss per share - basic and diluted	$	(0.37	)	$	(0.48	)

Securities excluded from the computation of diluted net loss per share because including them would have been antidilutive are as follows:


	March 31,
	2023		2022
Options to purchase common stock		10,517,404		7,475,876
Common stock subject to purchase under ESPP		92,889		129,107
Unvested RSUs		1,718,173		1,553,755
Total		12,328,466		9,158,738

Recently Adopted Accounting Standards

In June 2016, the Financial Accounting Standards Board (the FASB) issued Accounting Standards Update (ASU) No. 2016-13, Instruments – Credit Losses: Measurement of Credit Losses on Financial Instruments (ASU 2016-13), which requires expected credit losses relating to financial assets measured on an amortized cost basis and available-for-sale debt securities be recorded through an allowance for credit losses. ASU 2016-13 limits the amount of credit losses to be recognized for available-for-sale debt securities to the amount by which carrying value exceeds fair value and requires the reversal of previously recognized credit losses if fair value increases. The FASB issued additional amendments to the new guidance related to transition and clarification and deferred the effective date of this standard for all entities except SEC filers that are not smaller reporting companies to fiscal years beginning after December 15, 2022, including interim periods within those fiscal years. The Company adopted ASU 2016-13 effective January 1, 2023 on a modified retrospective basis. The Company elected to exclude accrued interest receivable from the amortized cost basis of its available-for-sale debt securities and to not measure an allowance for credit losses for accrued interest receivable. The adoption of ASU 2016-13 did not have a material impact on the Company’s consolidated financial statements.

Fair Value Measurements and Investments in Marketable Securities

3 Months Ended

Mar. 31, 2023

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, 2023
	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss			Fair Value
Cash equivalents
Money market fund	$	42,374	$	—	$	—		$	42,374
Total cash equivalents		42,374		—		—			42,374
Short-term marketable securities
U.S. and foreign corporate debt securities		14,853		—		(112	)		14,741
U.S. treasury securities		8,992		—		(128	)		8,864
U.S. and foreign commercial paper		5,929		—		—			5,929
Total short-term marketable securities		29,774		—		(240	)		29,534
Total cash equivalents and marketable securities	$	72,148	$	—	$	(240	)	$	71,908


	December 31, 2022
	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss			Fair Value
Cash equivalents
Money market fund	$	49,676	$	—	$	—		$	49,676
Total cash equivalents		49,676		—		—			49,676
Short-term marketable securities
U.S. and foreign corporate debt securities		18,903		—		(306	)		18,597
U.S. treasury securities		11,968		—		(224	)		11,744
U.S. and foreign commercial paper		8,851		—		—			8,851
Total short-term marketable securities		39,722		—		(530	)		39,192
Total cash equivalents and marketable securities	$	89,398	$	—	$	(530	)	$	88,868

As of March 31, 2023 and 2022, investments which were in an unrealized loss position were not material and were not the result of a decline in credit quality. Unrealized losses are generally due to interest rate fluctuations, as opposed to declines in credit quality. The Company determined it has the intent and ability to hold all marketable securities that have been in a continuous loss position until recovery of their amortized cost basis, which may be until maturity. As a result, the Company did not recognize any credit losses related to its investments and all unrealized gains and losses on available-for-sale securities are recorded in accumulated other comprehensive loss on the condensed consolidated balance sheets during the three months ended March 31, 2023 and 2022.

Accrued interest receivable was $0.2 million as of March 31, 2023 and 2022, and was recorded in prepaid expenses and other current assets on the condensed consolidated balance sheets. The Company did not write off any accrued interest receivable during the three months ended March 31, 2023.

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, 2023
	Level 1		Level 2		Level 3		Fair Value
Cash equivalents
Money market fund	$	42,374	$	—	$	—	$	42,374
Total cash equivalents		42,374		—		—		42,374
Short-term marketable securities
U.S. and foreign corporate debt securities		—		14,741		—		14,741
U.S. treasury securities		—		8,864		—		8,864
U.S. and foreign commercial paper		—		5,929		—		5,929
Total short-term marketable securities		—		29,534		—		29,534
Total assets measured at fair value	$	42,374	$	29,534	$	—	$	71,908


	December 31, 2022
	Level 1		Level 2		Level 3		Fair Value
Cash equivalents
Money market fund	$	49,676	$	—	$	—	$	49,676
Total cash equivalents		49,676		—		—		49,676
Short-term marketable securities
U.S. and foreign corporate debt securities		—		18,597		—		18,597
U.S. treasury securities		—		11,744		—		11,744
U.S. and foreign commercial paper		—		8,851		—		8,851
Total short-term marketable securities		—		39,192		—		39,192
Total assets measured at fair value	$	49,676	$	39,192	$	—	$	88,868

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

3 Months Ended

Mar. 31, 2023

Payables And Accruals [Abstract]

Other Accrued Expenses

Note 4 – Other Accrued Expenses

Other accrued expenses consist of the following (in thousands):


	March 31, 2023		December 31, 2022
Accrued expenses:
Accrued compensation	$	2,498	$	6,228
Accrued restructuring charges		344		599
Accrued professional fees and other		312		490
Total accrued expenses	$	3,154	$	7,317

Restructuring

3 Months Ended

Mar. 31, 2023

Restructuring and Related Activities [Abstract]

Restructuring

Note 5 – Restructuring

In July 2022, the Company and its board of directors approved a strategic plan to align with its refocused pipeline on its next generation core inhibitors and research programs and reduced its workforce by approximately 30%. The Company expects to incur total restructuring charges of $1.1 million. Restructuring charges consist solely of employee severance and related benefits which include $1.0 million in severance payments to executive officers impacted by the restructuring, $0.8 million in one-time termination severance payments and other employee-related costs associated with the restructuring and a reversal of $0.7 million for previously recognized stock-based compensation expense related to forfeited awards based on the Company's policy of recognizing stock-based awards with graded vesting schedules using an accelerated attribution method on a straight-line basis over the requisite service period for each separately vesting portion of the award and to recognize forfeitures when they occur.

There were no restructuring charges incurred during the three months ended March 31, 2023. The Company incurred cumulative restructuring charges of $1.1 million through March 31, 2023.

A summary of accrued restructuring charges, included as a component of other accrued expenses on the Company's condensed consolidated balance sheet as of March 31, 2023, is as follows (in thousands):


	Employee Severance and Related Benefits			Asset Impairment and Other Costs		Total Accrued Restructuring Charges
Accrued balance as of December 31, 2022	$	599		$	—	$	599
Reductions for cash payments		(255	)		—		(255	)
Accrued balance as of March 31, 2023	$	344		$	—	$	344

The Company expects the accrued restructuring charges to be fully paid by mid-2023.

Sale of Common Stock

3 Months Ended

Mar. 31, 2023

Equity [Abstract]

Sale of Common Stock

Note 6 – Sale of Common Stock

In August 2020, 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), pursuant to its shelf registration statement on Form S-3 on file with the SEC. During the three months ended March 31, 2023, the Company sold 3,050,446 shares of common stock under the 2020 ATM, for which the Company received net proceeds of $4.5 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.

- Definition

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-URI https://asc.fasb.org/topic&trid=2208762

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496158-112644

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 13
-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496158-112644

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 14
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496171-112644

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 14
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496171-112644

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI https://asc.fasb.org/extlink&oid=120397183&loc=d3e187085-122770

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 18
-Subparagraph (d)
-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496189-112644

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (g)
-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496158-112644

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 18
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496189-112644

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (h)
-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496158-112644

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 14
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496171-112644

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 18
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496189-112644

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 16
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496180-112644

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (i)
-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496158-112644

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(e)(1))
-URI https://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 40
-Section 50
-Paragraph 6
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126731327&loc=SL126733271-114008

+ Details

Stock-Based Compensation

3 Months Ended

Mar. 31, 2023

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-Based Compensation

Note 7 – Stock-Based Compensation

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,
	2023		2022
Research and development	$	910	$	778
General and administrative		925		665
Total stock-based compensation expense	$	1,835	$	1,443

As of March 31, 2023, there was $7.1 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 1.7 years.

The fair value of 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,
	2023	2022
Exercise price	$0.89 - $1.53	$1.53 - $2.45
Expected volatility	77.5% - 82.8%	79.2% - 81.6%
Risk-free rate	3.59% - 4.00%	1.41% - 2.48%
Expected term (years)	5.5 - 7.0	5.5 - 7.5
Expected dividend yield	0%	0%

Collaboration Agreements

3 Months Ended

Mar. 31, 2023

Collaboration Agreement [Abstract]

Collaboration Agreements

Note 8 - 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 March 31, 2023, 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 March 31, 2023 and December 31, 2022, 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, 2023 and 2022, 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, 2023 and December 31, 2022, 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 a nucleos(t)ide analog reverse transcriptase inhibitor (NrtI) compared to the double combinations of VBR with a NrtI and AB-729 with a NrtI. Under the Arbutus Biopharma Agreement, Assembly and Arbutus Biopharma share responsibility for the costs of the trial equally, excluding manufacturing supply which are the burden of each company to supply their respective drugs, VBR and AB-729. Assembly is responsible for conducting this clinical trial with Arbutus Biopharma reimbursing Assembly its share of expenses. In February 2023, Assembly and Arbutus Biopharma decided to terminate the Phase 2 clinical trial early, at the end of the 48-week on-treatment period, and are in the process of closing the study.

Reimbursements and cost-sharing portions from Arbutus Biopharma are reflected as a reduction of research and development expense when realized in the Company’s condensed consolidated statements of operations. During both the three months ended March 31, 2023 and 2022, the Company recognized a reduction of research and development expenses of $0.6 million under the Arbutus Biopharma Agreement.

Milestones and Research Agreements

3 Months Ended

Mar. 31, 2023

Milestones And Research Agreements [Abstract]

Milestones and Research Agreements

Note 9 - 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 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 both the three months ended March 31, 2023 and 2022.

Summary of Significant Accounting Policies (Policies)

3 Months Ended

Mar. 31, 2023

Accounting Policies [Abstract]

Basis of Presentation

months ended March 31, 2023 are not necessarily indicative of results to be expected for the entire year ending December 31, 2023 or future operating periods.

Use of Estimates

Other Risks and Uncertainties

Net Loss per Share

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,
	2023			2022
Numerator:
Net loss	$	(18,950	)	$	(23,091	)
Denominator:
Weighted average common shares outstanding - basic and diluted		51,012,450			48,123,930
Net loss per share - basic and diluted	$	(0.37	)	$	(0.48	)

Securities excluded from the computation of diluted net loss per share because including them would have been antidilutive are as follows:


	March 31,
	2023		2022
Options to purchase common stock		10,517,404		7,475,876
Common stock subject to purchase under ESPP		92,889		129,107
Unvested RSUs		1,718,173		1,553,755
Total		12,328,466		9,158,738

Recently Adopted Accounting Standards

Summary of Significant Accounting Policies (Tables)

3 Months Ended

Mar. 31, 2023

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,
	2023			2022
Numerator:
Net loss	$	(18,950	)	$	(23,091	)
Denominator:
Weighted average common shares outstanding - basic and diluted		51,012,450			48,123,930
Net loss per share - basic and diluted	$	(0.37	)	$	(0.48	)

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,
	2023		2022
Options to purchase common stock		10,517,404		7,475,876
Common stock subject to purchase under ESPP		92,889		129,107
Unvested RSUs		1,718,173		1,553,755
Total		12,328,466		9,158,738

Fair Value Measurements and Investments in Marketable Securities (Tables)

3 Months Ended

Mar. 31, 2023

Investments Debt And Equity Securities [Abstract]

Schedule of Investments in Marketable Securities

Investments in marketable securities consisted of the following (in thousands):


	March 31, 2023
	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss			Fair Value
Cash equivalents
Money market fund	$	42,374	$	—	$	—		$	42,374
Total cash equivalents		42,374		—		—			42,374
Short-term marketable securities
U.S. and foreign corporate debt securities		14,853		—		(112	)		14,741
U.S. treasury securities		8,992		—		(128	)		8,864
U.S. and foreign commercial paper		5,929		—		—			5,929
Total short-term marketable securities		29,774		—		(240	)		29,534
Total cash equivalents and marketable securities	$	72,148	$	—	$	(240	)	$	71,908


	December 31, 2022
	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss			Fair Value
Cash equivalents
Money market fund	$	49,676	$	—	$	—		$	49,676
Total cash equivalents		49,676		—		—			49,676
Short-term marketable securities
U.S. and foreign corporate debt securities		18,903		—		(306	)		18,597
U.S. treasury securities		11,968		—		(224	)		11,744
U.S. and foreign commercial paper		8,851		—		—			8,851
Total short-term marketable securities		39,722		—		(530	)		39,192
Total cash equivalents and marketable securities	$	89,398	$	—	$	(530	)	$	88,868

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, 2023
	Level 1		Level 2		Level 3		Fair Value
Cash equivalents
Money market fund	$	42,374	$	—	$	—	$	42,374
Total cash equivalents		42,374		—		—		42,374
Short-term marketable securities
U.S. and foreign corporate debt securities		—		14,741		—		14,741
U.S. treasury securities		—		8,864		—		8,864
U.S. and foreign commercial paper		—		5,929		—		5,929
Total short-term marketable securities		—		29,534		—		29,534
Total assets measured at fair value	$	42,374	$	29,534	$	—	$	71,908


	December 31, 2022
	Level 1		Level 2		Level 3		Fair Value
Cash equivalents
Money market fund	$	49,676	$	—	$	—	$	49,676
Total cash equivalents		49,676		—		—		49,676
Short-term marketable securities
U.S. and foreign corporate debt securities		—		18,597		—		18,597
U.S. treasury securities		—		11,744		—		11,744
U.S. and foreign commercial paper		—		8,851		—		8,851
Total short-term marketable securities		—		39,192		—		39,192
Total assets measured at fair value	$	49,676	$	39,192	$	—	$	88,868

- Definition

Tabular disclosure of financial instruments measured at fair value, including those classified in shareholders' equity measured on a recurring or nonrecurring basis. Disclosures include, but are not limited to, fair value measurements recorded and the reasons for the measurements, level within the fair value hierarchy in which the fair value measurements are categorized and transfers between levels 1 and 2. Nonrecurring fair value measurements are those that are required or permitted in the statement of financial position in particular circumstances.

+ References + Details

Other Accrued Expenses (Tables)

3 Months Ended

Mar. 31, 2023

Payables And Accruals [Abstract]

Schedule of Other Accrued Expenses


	March 31, 2023		December 31, 2022
Accrued expenses:
Accrued compensation	$	2,498	$	6,228
Accrued restructuring charges		344		599
Accrued professional fees and other		312		490
Total accrued expenses	$	3,154	$	7,317

Restructuring (Tables)

3 Months Ended

Mar. 31, 2023

Restructuring and Related Activities [Abstract]

Schedule of Accrued Restructuring Charges

A summary of accrued restructuring charges, included as a component of other accrued expenses on the Company's condensed consolidated balance sheet as of March 31, 2023, is as follows (in thousands):


	Employee Severance and Related Benefits			Asset Impairment and Other Costs		Total Accrued Restructuring Charges
Accrued balance as of December 31, 2022	$	599		$	—	$	599
Reductions for cash payments		(255	)		—		(255	)
Accrued balance as of March 31, 2023	$	344		$	—	$	344

The Company expects the accrued restructuring charges to be fully paid by mid-2023.

Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2023

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Assumptions Used to Estimate Fair Values of Stock Options Grants

The fair value of 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,
	2023	2022
Exercise price	$0.89 - $1.53	$1.53 - $2.45
Expected volatility	77.5% - 82.8%	79.2% - 81.6%
Risk-free rate	3.59% - 4.00%	1.41% - 2.48%
Expected term (years)	5.5 - 7.0	5.5 - 7.5
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,
	2023		2022
Research and development	$	910	$	778
General and administrative		925		665
Total stock-based compensation expense	$	1,835	$	1,443

Nature of Business - Additional Information (Details)	3 Months Ended
Nature of Business - Additional Information (Details)	Mar. 31, 2023 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 Accounting Policies - Schedule of Earnings Per Share, Basic and Diluted (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Numerator:
Net loss	$ (18,950)	$ (23,091)
Denominator:
Weighted average common shares outstanding - basic	51,012,450	48,123,930
Weighted average common shares outstanding - diluted	51,012,450	48,123,930
Net loss per share - basic	$ (0.37)	$ (0.48)
Net loss per share - diluted	$ (0.37)	$ (0.48)

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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- Definition

The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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+ Details

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

+ Details

Summary of Significant Accounting Policies - Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share (Details) - shares	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities excluded from computation of loss per share	12,328,466	9,158,738
Options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities excluded from computation of loss per share	10,517,404	7,475,876
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	92,889	129,107
Unvested RSUs
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities excluded from computation of loss per share	1,718,173	1,553,755

Fair Value Measurements and Investments in Marketable Securities - Schedule of Investments in Marketable Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Investments in marketable securities:
Amortized Cost	$ 43,482	$ 52,418
Amortized Cost, Short-term marketable securities	29,774	39,722
Gross Unrealized Gain, Short-term marketable securities	0	0
Gross Unrealized Loss, Short-term marketable securities	(240)	(530)
Fair Value, Short-term marketable securities	29,534	39,192
Amortized Cost	72,148	89,398
Gross Unrealized Gain	0	0
Gross Unrealized Loss	(240)	(530)
Fair Value	71,908	88,868
Cash equivalents
Investments in marketable securities:
Amortized Cost	42,374	49,676
Gross Unrealized Gain	0	0
Gross Unrealized Loss	0	0
Fair Value	42,374	49,676
Money market fund \| Cash equivalents
Investments in marketable securities:
Amortized Cost	42,374	49,676
Gross Unrealized Gain	0	0
Gross Unrealized Loss	0	0
Fair Value	42,374	49,676
U.S and foreign corporate debt securities
Investments in marketable securities:
Amortized Cost, Short-term marketable securities	14,853	18,903
Gross Unrealized Gain, Short-term marketable securities	0	0
Gross Unrealized Loss, Short-term marketable securities	(112)	(306)
Fair Value, Short-term marketable securities	14,741	18,597
U.S. treasury securities
Investments in marketable securities:
Amortized Cost, Short-term marketable securities	8,992	11,968
Gross Unrealized Gain, Short-term marketable securities	0	0
Gross Unrealized Loss, Short-term marketable securities	(128)	(224)
Fair Value, Short-term marketable securities	8,864	11,744
U.S. and foreign commercial paper
Investments in marketable securities:
Amortized Cost, Short-term marketable securities	5,929	8,851
Gross Unrealized Gain, Short-term marketable securities	0	0
Gross Unrealized Loss, Short-term marketable securities	0	0
Fair Value, Short-term marketable securities	$ 5,929	$ 8,851

Fair Value Measurements and Investments in Marketable Securities - Additional Information (Details) - USD ($)	Mar. 31, 2023	Mar. 31, 2022
Investments in marketable securities:
Fair value assets transfers between level 1, level 2 or level 3	$ 0
Accrued interest receivable	$ 200,000	$ 200,000

Fair Value Measurements and Investments in Marketable Securities - Schedule of Fair Value of Financial Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Short-term marketable securities
Short-term marketable securities	$ 29,534	$ 39,192
U.S. treasury securities
Short-term marketable securities
Short-term marketable securities	8,864	11,744
U.S and foreign corporate debt securities
Short-term marketable securities
Short-term marketable securities	14,741	18,597
Recurring
Cash equivalents
Cash equivalents	42,374	49,676
Short-term marketable securities
Short-term marketable securities	29,534	39,192
Long-term marketable securities
Total assets measured at fair value	71,908	88,868
Recurring \| U.S and foreign corporate debt securities
Short-term marketable securities
Short-term marketable securities	14,741	18,597
Recurring \| U.S. treasury securities
Short-term marketable securities
Short-term marketable securities	8,864	11,744
Recurring \| U.S. and foreign commercial paper
Short-term marketable securities
Short-term marketable securities	5,929	8,851
Recurring \| Money market fund
Cash equivalents
Cash equivalents	42,374	49,676
Recurring \| Level 1
Cash equivalents
Cash equivalents	42,374	49,676
Short-term marketable securities
Short-term marketable securities	0	0
Long-term marketable securities
Total assets measured at fair value	42,374	49,676
Recurring \| Level 1 \| U.S and foreign corporate debt securities
Short-term marketable securities
Short-term marketable securities	0	0
Recurring \| Level 1 \| U.S. treasury securities
Short-term marketable securities
Short-term marketable securities	0	0
Recurring \| Level 1 \| U.S. and foreign commercial paper
Short-term marketable securities
Short-term marketable securities	0	0
Recurring \| Level 1 \| Money market fund
Cash equivalents
Cash equivalents	42,374	49,676
Recurring \| Level 2
Cash equivalents
Cash equivalents	0	0
Short-term marketable securities
Short-term marketable securities	29,534	39,192
Long-term marketable securities
Total assets measured at fair value	29,534	39,192
Recurring \| Level 2 \| U.S and foreign corporate debt securities
Short-term marketable securities
Short-term marketable securities	14,741	18,597
Recurring \| Level 2 \| U.S. treasury securities
Short-term marketable securities
Short-term marketable securities	8,864	11,744
Recurring \| Level 2 \| U.S. and foreign commercial paper
Short-term marketable securities
Short-term marketable securities	5,929	8,851
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
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
Recurring \| Level 3 \| U.S. treasury 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 \| Money market fund
Cash equivalents
Cash equivalents	$ 0	$ 0

Other Accrued Expenses - Schedule of Other Accrued Expenses (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Accrued expenses:
Accrued compensation	$ 2,498	$ 6,228
Accrued restructuring charges	344	599
Accrued professional fees and other	312	490
Total accrued expenses	$ 3,154	$ 7,317

Restructuring - Additional Information (Details) - USD ($) $ in Millions	1 Months Ended		3 Months Ended
	Jul. 31, 2022	Jul. 31, 2021	Mar. 31, 2023
Restructuring Cost and Reserve [Line Items]
Percentage of workforce reduced	30.00%
Restructuring charges		$ 1.1	$ 0.0
Cumulative restructuring charges			$ 1.1
Employee severance and related benefits	$ 1.0
Restructuring one-time termination Cost	0.8
Restructuring costs reversal	$ 0.7

Restructuring - Schedule of Accrued Restructuring Charges (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2023 USD ($)
Restructuring Cost and Reserve [Line Items]
Accrued balance as of December 31, 2022	$ 599
Reductions for cash payments	(255)
Accrued balance as of March 31, 2023	344
Employee Severance and Related Benefits
Restructuring Cost and Reserve [Line Items]
Accrued balance as of December 31, 2022	599
Reductions for cash payments	(255)
Accrued balance as of March 31, 2023	344
Asset Impairment and Other Costs
Restructuring Cost and Reserve [Line Items]
Accrued balance as of December 31, 2022	0
Reductions for cash payments	0
Accrued balance as of March 31, 2023	$ 0

Sale of Common Stock - Additional Information (Details) - 2020 At the Market Offerings - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Aug. 31, 2020
Subsidiary Sale Of Stock [Line Items]
Number of shares sold	3,050,446	0
Net proceeds from the issuance of common stock through equity plans	$ 4.5
Maximum
Subsidiary Sale Of Stock [Line Items]
Initial public offering value of shares authorized			$ 100.0

Stock-Based Compensation - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation expense	$ 1,835	$ 1,443
Unrecognized stock-based compensation expense	$ 7,100
Unrecognized stock-based compensation expense expected to be recognized, term	1 year 8 months 12 days

Stock-Based Compensation -Schedule of Recognized Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Compensation expense:
Stock-based compensation expense	$ 1,835	$ 1,443
Research and Development
Compensation expense:
Stock-based compensation expense	910	778
General and Administrative
Compensation expense:
Stock-based compensation expense	$ 925	$ 665

Stock-Based Compensation - Summary of Assumptions Used to Estimate Fair Values of Stock Options Grants (Details) - $ / shares	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
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	$ 0.89	$ 1.53
Expected volatility	77.50%	79.20%
Risk-free rate	3.59%	1.41%
Expected term (years)	5 years 6 months	5 years 6 months
Maximum
Share-based Compensation Arrangement by Share-based Payment Award
Exercise price	$ 1.53	$ 2.45
Expected volatility	82.80%	81.60%
Risk-free rate	4.00%	2.48%
Expected term (years)	7 years	7 years 6 months

Collaboration Agreements - Additional Information (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Research And Development Arrangement Contract To Perform For Others [Line Items]
Deferred revenue	$ 2,733,000		$ 2,733,000
Research and development expense	14,547,000	$ 17,205,000
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	$ 600,000

Milestones and Research Agreements - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Milestone and Research Agreements:
Potential milestone payment	$ 0.8
Milestone payment, diligence maintenance fees	$ 0.1	$ 0.1