0001746473-24-000043 | 10-K | XBRL Viewer

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Stock-Based Compensation - 2020 Employee Stock Purchase Plan - Summary of Black-Scholes Option Pricing Model to Estimate Stock-based Compensation Expense for 2020 Employee Stock Purchase Plan (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividends	0.00%
2020 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate, minimum	5.20%	0.60%	0.06%
Risk-free interest rate, maximum	5.47%	3.34%	0.07%
Expected term (in years)	6 months	6 months	6 months
Expected volatility, minimum	54.78%	63.17%	67.16%
Expected volatility, maximum	69.15%	82.02%	89.51%
Expected dividends	0.00%	0.00%	0.00%

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

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+ Details

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2023

Accounting Policies [Abstract]

Summary of Useful Lives of Property and Equipment

The useful lives of property and equipment are as follows:


Laboratory equipment			5 years
Computer equipment and software			3 years
Leasehold improvements			Shorter of remaining lease term or estimated useful life

Property and Equipment, net

12 Months Ended

Dec. 31, 2023

Property, Plant and Equipment [Abstract]

Property and Equipment, net

Property and equipment, net consisted of the following (in thousands):


	December 31,
	2023		2022
Laboratory equipment	$	10,410	$	9,581
Leasehold improvements	1,663		1,650
Construction-in-progress	52		66
Computer equipment and software	124		30
Total property and equipment	12,249		11,327
Less: Accumulated depreciation	(8,682)		(6,841)
Total property and equipment, net	$	3,567	$	4,486

Depreciation expense during the years ended December 31, 2023 and 2022 was $1.8 million, and for 2021 depreciation expense was $1.5 million.

Stock-Based Compensation - Summary of Restricted Stock Activity (Details) - Restricted stock units	12 Months Ended
	Dec. 31, 2023 $ / shares shares
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Outstanding and unvested, beginning balance (in shares) \| shares	507,925
Granted (in shares) \| shares	683,703
Released (in shares) \| shares	(247,488)
Forfeited (in shares) \| shares	(69,392)
Outstanding and unvested, ending balance (in shares) \| shares	874,748
Weighted Average Grant Date Fair Value
Weighted-Average Grant Date fair value, Outstanding and unvested, beginning balance (USD per share) \| $ / shares	$ 17.43
Granted (USD per share) \| $ / shares	34.36
Released (USD per share) \| $ / shares	17.43
Forfeited (USD per share) \| $ / shares	27.69
Weighted-Average Grant Date fair value, Outstanding and unvested, ending balance (USD per share) \| $ / shares	$ 29.85

Cover - USD ($)	12 Months Ended
Cover - USD ($)	Dec. 31, 2023	Feb. 23, 2024	Jun. 30, 2023
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2023
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	001-39303
Entity Registrant Name	PLIANT THERAPEUTICS, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	47-4272481
Entity Address, Address Line One	260 Littlefield Avenue
Entity Address, City or Town	South San Francisco,
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94080
City Area Code	650
Local Phone Number	481-6770
Title of 12(b) Security	Common Stock, par value $0.0001 per share
Trading Symbol	PLRX
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Document Financial Statement Error Correction	false
Entity Shell Company	false
Entity Public Float			$ 1,008,132,383
Entity Common Stock, Shares Outstanding		60,239,176
Documents Incorporated by Reference	DOCUMENTS INCORPORATED BY REFERENCE Portions of the registrant’s definitive Proxy Statement for the 2024 Annual Meeting of Stockholders to be filed with the U.S. Securities and Exchange Commission pursuant to Regulation 14A not later than 120 days after the end of the fiscal year covered by this Annual Report on Form 10-K are incorporated by reference in Part III, Items 10-14 of this Annual Report on Form 10-K
Amendment Flag	false
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Entity Central Index Key	0001746473

Financial Instruments - Narrative (Details) - USD ($)	Dec. 31, 2023	Dec. 31, 2022
Fair Value, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities measured at fair value	$ 0	$ 0
Fair Value Measurements, Non-recurring Basis
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities measured at fair value	0	0
Assets measured at fair value	0	0
Fair Value, Inputs, Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities measured at fair value	0
Assets measured at fair value	$ 0	0
Fair Value, Inputs, Level 3 \| Fair Value, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities measured at fair value		$ 0

Stock-Based Compensation - Restricted Stock Units - Narrative (Details) - Restricted stock units $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost	$ 17.4
Unrecognized compensation expense, weighted average period	1 year 7 months 28 days
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	2 years
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

+ Details

Stock-Based Compensation - Summary of Classification of Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	5 Months Ended	12 Months Ended
	Jul. 31, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense		$ 44,483	$ 22,598	$ 10,437
Research and development expenses
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense		17,973	8,730	3,928
General and administrative expenses
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense		26,510	13,867	6,509
Restricted stock awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense		0	36	182
Stock options and ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense		21,313	13,280	10,255
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense		11,149	1,892	0
Performance-based restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 7,300	$ 12,021	$ 7,390	$ 0

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

+ Details

Summary of Significant Accounting Policies - Summary of Useful Lives of Property and Equipment (Details)	Dec. 31, 2023
Laboratory equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	5 years
Computer equipment and software
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	3 years

Income Taxes - Summary of Reconciliation of U.S. Federal Statutory Income Tax Rate to Company’s Effective Income Tax Rate (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Income tax computed at federal statutory rate	21.00%	21.00%	21.00%
State taxes, net of federal tax benefit	6.70%	7.30%	7.70%
General business credit—federal	5.30%	3.60%	5.30%
Stock-based compensation	0.90%	(1.00%)	(0.70%)
Other permanent differences	0.10%	(0.40%)	(0.10%)
Section 162(m)	(3.80%)	0.00%	0.00%
Change in valuation allowance	(30.20%)	(30.50%)	(33.20%)
Effective income tax rate	0.00%	0.00%	0.00%

Accrued Liabilities

12 Months Ended

Dec. 31, 2023

Accrued Liabilities and Other Liabilities [Abstract]

Accrued Liabilities

Accrued liabilities consisted of the following (in thousands):


	December 31,
	2023		2022
Accrued compensation and benefits	$	9,042	$	7,200
Other accrued liabilities	1,177		1,458
Total accrued liabilities	$	10,219	$	8,658

Accrued compensation and benefits consist primarily of accrued bonuses and accrued vacation.

Leases - Narrative (Details) $ in Thousands		12 Months Ended
Leases - Narrative (Details) $ in Thousands	Sep. 28, 2023 USD ($) ft²	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Lessee, Lease, Description [Line Items]
Total undiscounted lease payments		$ 1,382
Decrease in right-of -use assets and liabilities from lease modifications		1,821	$ 0	$ 0
Other Non-current Assets
Lessee, Lease, Description [Line Items]
Refundable security deposit		400
California
Lessee, Lease, Description [Line Items]
Leased premises under non cancelable operating lease \| ft²	100,904
Lease term	7 years
Lease term extension period	8 years
Total undiscounted lease payments		$ 43,700
California \| Landlord \| Letter of Credit \| Pliant Therapeutics
Lessee, Lease, Description [Line Items]
Line of credit	$ 1,400

Preferred Stock	12 Months Ended
Preferred Stock	Dec. 31, 2023
Temporary Equity Disclosure [Abstract]
Preferred Stock	Preferred Stock Under the Company’s Amended and Restated Certificate of Incorporation, the Company is authorized to issue two classes of shares: preferred stock and common stock. The preferred stock may be issued in series, and the Company’s board of directors is authorized to determine the rights, preferences, and terms of each series. These rights, preferences and terms could include dividend rights, conversion rights, voting rights, terms of redemptions, liquidation preferences and sinking fund terms. As of December 31, 2023 and 2022, the Company was authorized to issue 10,000,000 shares of preferred stock and there was no outstanding preferred stock as of December 31, 2023 and 2022.

Financial Instruments

12 Months Ended

Dec. 31, 2023

Fair Value Disclosures [Abstract]

Financial Instruments

The Company’s short-term investments consist of U.S. Treasury securities, U.S. Government agency securities and highly rated, investment-grade corporate debt securities with original maturities beyond three months at the date of purchase. The Company has classified and accounted for its short-term investments as available-for-sale securities as the Company may sell these securities at any time even prior to maturity and such investments represent cash available for current operations. As a result, short-term investments may include securities with maturities beyond twelve months that are classified within current assets in the Balance Sheets. The Company’s short-term investments classified as available-for-sale are carried at fair market value with unrealized gain or loss recognized in other comprehensive gain (loss).

Assets and liabilities recorded at fair value on a recurring basis in the Balance Sheets and assets and liabilities measured at fair value on a non-recurring basis or disclosed at fair value, are categorized based upon the level of judgment associated with inputs used to measure their fair values. Fair value is defined as the price that would be received upon the sale of an asset or paid to transfer a liability (an exit price) in an orderly transaction between market participants at the measurement date. Accounting guidance establishes a three-level valuation hierarchy that prioritizes the inputs to valuation techniques used to measure fair value based upon whether such inputs are observable or unobservable. Observable inputs reflect market data obtained from independent sources, while unobservable inputs reflect market assumptions made by the reporting entity. The three-level hierarchy for the inputs to valuation techniques is briefly summarized as follows:

•Level 1—Inputs are unadjusted, quoted prices in active markets for identical assets or liabilities at the measurement date;

•Level 2—Inputs are observable, unadjusted quoted prices in active markets for similar assets or liabilities, unadjusted quoted prices for identical or similar assets or liabilities in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the related assets or liabilities; and

•Level 3—Unobservable inputs that are significant to the measurement of the fair value of the assets or liabilities that are supported by little or no market data.

The fair value of the Company’s cash equivalent Money Market Funds are classified as Level 1 because they are valued using quoted market prices. The fair value of the Company’s U.S. Treasury securities, U.S. government agency securities and corporate debt securities are classified as Level 2 because they are valued using observable inputs to quoted market prices, benchmark yields, reported trades, broker/dealer quotes or alternative pricing sources with reasonable levels of price transparency. These Level 2 instruments require more management judgment and subjectivity compared to Level 1 instruments which include determining which instruments are most similar to the instrument being priced, determining whether the market is active and determining which model-derived valuations are to be used when calculating fair value. The Company performs its analysis with the assistance of investment advisors.

There were no assets or liabilities recorded at fair value using Level 3 inputs as of December 31, 2023 and 2022.

The following tables show the Company’s cash and cash equivalents and short-term investments by significant investment category as of December 31, 2023 and 2022 (in thousands):


		As of December 31, 2023								As of December 31, 2022
		Adjusted Cost		Unrealized Gains		Unrealized Losses		Market Value		Adjusted Cost		Unrealized Gains		Unrealized Losses		Market Value
Money Market Funds	Level 1	$	57,241	$	—	$	—	$	57,241	$	28,312	$	—	$	—	$	28,312
U.S. Treasury securities	Level 2	27,250		46		(8)		27,288		4,446		—		(5)		4,441
U.S. Government Agency Securities	Level 2	133,655		563		(132)		134,086		28,746		—		(111)		28,635
Corporate debt securities	Level 2	269,761		213		(337)		269,637		266,267		45		(1,887)		264,425
Total financial assets		$	487,907	$	822	$	(477)	$	488,252	$	327,771	$	45	$	(2,003)	$	325,813


	As of December 31, 2023								As of December 31, 2022
Classified as:	Adjusted Cost		Unrealized Gains		Unrealized Losses		Market Value		Adjusted Cost		Unrealized Gains		Unrealized Losses		Market Value
Cash equivalents	$	57,241	$	—	$	—	$	57,241	$	28,312	$	—	$	—	$	28,312
Short-term investments	430,666		822		(477)		431,011		299,459		45		(2,003)		297,501
Total	$	487,907	$	822	$	(477)	$	488,252	$	327,771	$	45	$	(2,003)	$	325,813

The Company may sell certain of its short-term securities prior to their stated maturities for reasons including, but not limited to, managing liquidity, credit risk, duration and asset allocation.

The following summarizes the remaining contractual maturities of the Company’s short-term investments as of December 31, 2023:


	Adjusted Cost		Market Value
Mature in 1 year or less	$	316,700	$	316,366
Mature in 1 to 2 years	113,966		114,645
Total	$	430,666	$	431,011

There were no liabilities measured at fair value on a recurring basis as of December 31, 2023 and 2022. There have been no transfers between fair value measurement levels during the years ended December 31, 2023 and 2022. In addition, there were no assets or liabilities measured at fair value on a non-recurring basis as of December 31, 2023 and 2022.

The Company records interest income and accretion income earned on Money Market Funds and U.S. Treasury, U.S. government agency and corporate debt securities to interest and other income(expense),net in its statement of operations and comprehensive gain (loss).

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Defined Contribution Plan	12 Months Ended
Defined Contribution Plan	Dec. 31, 2023
Retirement Benefits [Abstract]
Defined Contribution Plan	Defined Contribution Plan The Company sponsors a defined contribution plan under Section 401(k) of the Internal Revenue Code covering substantially all full-time U.S. employees. Employee contributions are voluntary and are determined on an individual basis subject to the maximum allowable under federal tax regulations. The Company made contributions to the plan of $1.0 million, $0.8 million and $0.6 million during the years ended December 31, 2023, 2022 and 2021, respectively.

Stock-Based Compensation - Equity Incentive Plan - Narrative (Details) - shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total shares reserved for future issuance (in shares)	12,544,982	11,435,241
Shares of common stock available for future grants under the 2020 Stock Option and Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total shares reserved for future issuance (in shares)	2,882,239	2,937,769
Exercise price as a percentage of estimated grant date fair value of shares	10.00%
Expiration period from date of grant	5 years
Shares of common stock available for future grants under the 2020 Stock Option and Incentive Plan \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options under plan may be granted for periods	10 years
Exercise price as a percentage of estimated grant date fair value of shares	110.00%
Shares of common stock available for future issuance under the 2022 Inducement Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total shares reserved for future issuance (in shares)	700,000	1,000,000

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

+ Details

Organization and Description of Business (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended
	Jan. 31, 2023	Jul. 31, 2022
Public Offering
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Public and private offering, shares issued (in shares)	9,583,334	12,432,432
Private Placement \| Underwriters
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Public and private offering, shares issued (in shares)	1,250,000	1,621,621
Public Offering And Private Placement
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Share price of shares issued (USD per share)	$ 30.00	$ 18.50
Proceeds from the sale of shares	$ 269.8	$ 215.4

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Reference 79: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Stock-Based Compensation - 2020 Employee Stock Purchase Plan Narrative (Details) - USD ($) $ in Thousands	1 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Jun. 30, 2020	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total shares reserved for future issuance (in shares)			12,544,982	11,435,241
Share-based payment arrangement, expense			$ 44,483	$ 22,598	$ 10,437
2020 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total shares reserved for future issuance (in shares)	700,000	700,000
Employee stock purchase plan, description	The 2020 ESPP is subject to automatic increases on January 1 of each calendar year, beginning January 1, 2021, by the lesser of (i) 1% of the outstanding shares on the immediately preceding December 31, (ii) 700,000 shares or (iii) such lesser amount as determined by, the compensation committee of the Board of Directors.
Common stock shares outstanding percentage	1.00%
Percentage of payroll deductions	15.00%	15.00%
Employee stock purchase plan offering period	6 months
Common stock fair market value percentage		85.00%
Share-based payment arrangement, expense			$ 600	$ 400	$ 500
Number of common stock issued (in shares)			82,428	85,969	86,902

Statements of Operations and Comprehensive Gain (Loss) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Statement [Abstract]
Revenue	$ 1,580	$ 9,685	$ 7,572
Operating expenses:
Research and development	(127,797)	(96,936)	(77,549)
General and administrative	(57,928)	(39,949)	(27,558)
Total operating expenses	(185,725)	(136,885)	(105,107)
Loss from operations	(184,145)	(127,200)	(97,535)
Interest and other income (expense), net	24,076	4,670	272
Interest expense	(1,267)	(791)	0
Net loss	$ (161,336)	$ (123,321)	$ (97,263)
Earnings Per Share [Abstract]
Basic (USD per share)	$ (2.75)	$ (2.94)	$ (2.71)
Diluted (USD per share)	$ (2.75)	$ (2.94)	$ (2.71)
Weighted Average Number of Shares Outstanding, Diluted [Abstract]
Basic (in shares)	58,719,083	42,015,908	35,846,421
Diluted (in shares)	58,719,083	42,015,908	35,846,421
Comprehensive loss:
Net loss	$ (161,336)	$ (123,321)	$ (97,263)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract]
Net unrealized gain (loss) on short-term investments	2,303	(1,757)	(169)
Total other comprehensive gain (loss)	2,303	(1,757)	(169)
Comprehensive loss	$ (159,033)	$ (125,078)	$ (97,432)

Accrued Liabilities (Tables)

12 Months Ended

Dec. 31, 2023

Accrued Liabilities and Other Liabilities [Abstract]

Summary of Accrued Liabilities

Accrued liabilities consisted of the following (in thousands):


	December 31,
	2023		2022
Accrued compensation and benefits	$	9,042	$	7,200
Other accrued liabilities	1,177		1,458
Total accrued liabilities	$	10,219	$	8,658

Summary of Significant Accounting Policies - Narrative (Details)	12 Months Ended
	Dec. 31, 2023 USD ($) segment	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Accounting Policies [Line Items]
Percentage of revenue contributed by related party	100.00%
Number of operating segments \| segment	1
Number of reportable segments \| segment	1
Restricted cash \| $	$ 1,400,000
Impairment of long-lived assets \| $	$ 0	$ 0	$ 0
Expected dividends	0.00%
Novartis Agreement
Accounting Policies [Line Items]
Description of customer payment terms	The Company performs credit evaluations of its customer, and the risk with respect to accounts receivable is further mitigated by the short duration of customer payment terms, generally within 60 days, and the pedigree of the customer base.
Customer payment term duration	60 days

Related Party Transactions - (Details) - USD ($)	1 Months Ended		12 Months Ended
Related Party Transactions - (Details) - USD ($)	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2023
Related Party Transaction [Line Items]
Related party transaction amount			$ 0
Outstanding stock option awards \| Third Rock Ventures \| Non-employee Director
Related Party Transaction [Line Items]
Options granted (in shares)	15,000	26,572
Grant date fair value of stock option	$ 100,000	$ 500,000

Accrued Liabilities - Summary of Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Accrued Liabilities and Other Liabilities [Abstract]
Accrued compensation and benefits	$ 9,042	$ 7,200
Other accrued liabilities	1,177	1,458
Total accrued liabilities	$ 10,219	$ 8,658

Commitments and Contingencies (Details)	12 Months Ended
Commitments and Contingencies (Details)	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Contractual arrangements cancellation period	30 days

Organization and Description of Business	12 Months Ended
Organization and Description of Business	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Description of Business	Organization and Description of Business Pliant Therapeutics, Inc. (the “Company” or "Pliant" or “we” or “our” or “us”) is a late stage clinical stage biopharmaceutical company focused on discovering and developing novel therapies for the treatment of fibrosis with an initial focus on treating fibrosis by inhibiting integrin-mediated activation of TGF-β. Fibrosis refers to the abnormal thickening and scarring of connective tissue due to the production and deposition of excess collagen in the extra-cellular matrix. Fibrosis can occur in many different tissues including lung, liver, kidney, muscle, skin and the GI tract, and often causes severe and debilitating disease leading to organ failure. The Company is located in South San Francisco, California, and was incorporated in the state of Delaware in June 2015. Public Offerings In July 2022, the Company completed a public offering of 12,432,432 shares of common stock, including the exercise in full of the underwriters' option to purchase 1,621,621 additional shares of common stock. The shares were offered at a price of $18.50 per share, resulting in aggregate proceeds of approximately $215.4 million, net of underwriting discounts, commissions and offering expenses. In January 2023, the Company completed a public offering of 9,583,334 shares of common stock, including the exercise in full of the underwriters' option to purchase 1,250,000 additional shares of common stock. The shares were offered at a price of $30.00 per share, resulting in aggregate proceeds of approximately $269.8 million, net of underwriting discounts, commissions and offering expenses payable by us.

Common Stock - Summary of Shares Reserved for Future Issuance (Details) - shares	Dec. 31, 2023	Dec. 31, 2022
Class of Stock [Line Items]
Total shares reserved for future issuance (in shares)	12,544,982	11,435,241
Shares of common stock available for future grants under the 2020 Stock Option and Incentive Plan
Class of Stock [Line Items]
Total shares reserved for future issuance (in shares)	2,882,239	2,937,769
Shares of common stock available for future issuance under the 2020 ESPP
Class of Stock [Line Items]
Total shares reserved for future issuance (in shares)	805,756	888,184
Shares of common stock available for future issuance under the 2022 Inducement Plan
Class of Stock [Line Items]
Total shares reserved for future issuance (in shares)	700,000	1,000,000
Outstanding stock option awards
Class of Stock [Line Items]
Total shares reserved for future issuance (in shares)	6,953,487	5,569,567
Restricted stock units
Class of Stock [Line Items]
Total shares reserved for future issuance (in shares)	874,748	507,925
Performance Stock Units
Class of Stock [Line Items]
Total shares reserved for future issuance (in shares)	328,752	531,796
Performance-based restricted stock units
Class of Stock [Line Items]
Target level of achievement percentage	100.00%

Stock-Based Compensation

12 Months Ended

Dec. 31, 2023

Share-Based Payment Arrangement [Abstract]

Stock-Based Compensation

Equity Incentive Plans

In 2015, the Company's Board of Directors adopted the 2015 Equity Incentive Plan, as amended in 2018, 2019 and 2020 (the “2015 Plan”), which provided for the grant of incentive stock options, nonqualified stock options or other awards including stock appreciation rights and restricted stock awards to the Company’s employees, officers, directors, advisors, and consultants. In May 2020, the Board of Directors adopted the 2020 Stock Option and Incentive Plan (the “2020 Plan”) and suspended the 2015 Plan. Awards outstanding under either the 2015 Plan or 2020 Plan that are cancelled, expire or otherwise terminated subsequent to May 2020 will become available for issuance as common stock under the 2020 Plan. Additionally, the 2020 Plan is subject to automatic increases on January 1 of each year beginning January 1, 2021. The number of shares added each January 1 will be equal to the lesser of: (i) 5% of the outstanding shares on the immediately preceding December 31 or (ii) such amount as determined by the compensation committee of the Board of Directors.

The 2020 Plan provides for the grant of incentive stock options, nonqualified stock options or other awards including stock appreciation rights, restricted stock awards and restricted stock units to the Company’s employees, officers, directors, advisors and consultants. As of December 31, 2023, the 2020 Plan had 2,882,239 shares of common stock available for future issuance.

In 2022, the Board of Directors adopted the 2022 Inducement Plan ("Inducement Plan"), under which the Company may grant nonqualified stock options or other awards including stock appreciation rights and restricted stock awards. As of December 31, 2023, 700,000 shares of common stock were available for issuance.

Options under the 2020 Plan and Inducement Plan may be granted for periods of up to 10 years and at prices no less than the market price of the Company’s common stock on the date of grant, provided, however, that the exercise price of an incentive stock option granted to a 10% shareholder shall not be less than 110% of the fair value of the shares on the date of grant and the option is not exercisable after the expiration of five years from the date of grant.

Incentive Stock Options and Nonqualified Stock Options

Stock options issued under either the 2015 Plan, the 2020 Plan or the Inducement Plan generally vest over four years and expire ten years from the date of grant. Certain options provide for accelerated vesting if there is a change in control, as defined in the respective plans.

The Company used Black-Scholes option pricing model to estimate stock-based compensation expense for stock option awards with the following assumptions:


	Year Ended December 31,
	2023		2022		2021
	Min	Max	Min	Max	Min	Max
Expected volatility	80.97%	83.28%	73.78%	80.64%	74.83%	76.31%
Risk-free interest rate	3.42%	4.68%	1.64%	4.16%	0.61%	1.39%
Expected dividend	—	—	—	—	—	—
Expected term (in years)	5.31	6.08	5.33	6.08	5.44	6.08
Underlying common stock fair value	$15.25	$34.65	$4.92	$24.23	$15.20	$38.23

A summary of option activity under the 2015 Plan and the 2020 Plan is as follows:


	Number of Options	Weighted- Average Exercise Price per Share		Weighted- Average Remaining Contractual Term (in Years)	Aggregate Intrinsic Value (in thousands)
Outstanding as of December 31, 2022	5,569,567	$	13.34	7.96	$	43,696
Granted	2,158,764	$	27.22
Exercised	(534,706)	$	6.91
Forfeited	(240,138)	$	18.81
Outstanding as of December 31, 2023	6,953,487	$	17.95	7.70	$	32,646
Exercisable as of December 31, 2023	3,515,801	$	15.03	6.74	$	23,184
Vested and expected to vest as of December 31, 2023	6,953,487	$	17.95	7.70	$	32,646

As of December 31, 2023, there was $46.4 million of unrecognized compensation costs that is expected to be recognized over the weighted-average periods of 2.5 years related to stock options. The total intrinsic value of stock options exercised was $11.4 million, $2.0 million and $6.9 million for December 31, 2023, 2022 and 2021, respectively. Intrinsic value represents the difference between the current fair value of the underlying stock and the exercise price of the stock option at the respective balance sheet dates. The weighted-average grant date fair value of options granted during the years ended December 31, 2023, 2022 and 2021 was $27.22, $7.82 and $16.94 per share, respectively.

Restricted Stock Units

The service-based condition for restricted stock units ("RSUs") is generally satisfied over two or three years. The following table sets forth the outstanding RSUs and related activity for the year ended December 31, 2023:


	Restricted Stock Units	Weighted Average Grant Date Fair Value
Unvested and outstanding as of December 31, 2022	507,925	$	17.43
Granted	683,703	$	34.36
Released	(247,488)	$	17.43
Forfeited	(69,392)	$	27.69
Unvested and outstanding as of December 31, 2023	874,748	$	29.85

As of December 31, 2023, the Company had $17.4 million of unrecognized stock-based compensation expense related to outstanding RSUs expected to be recognized over a weighted-average period of 1.66 years.

Performance-Based Restricted Stock Units

In July 2022 the Company granted performance-based restricted stock units ("PSUs") that vest upon the achievement of market and performance conditions. Market conditions include the Company's total shareholder return ("TSR") relative to the NASDAQ Biotechnology Index over the term of the award ending on June 30, 2024, and performance conditions consist of multiple clinical development milestones associated with bexotegrast. The performance vesting conditions generally must be satisfied within a two-year period and are forfeited if the vesting conditions are not met. Additionally, the number of shares of common stock issued upon vesting will range from 0% to 200% of the PSUs based on achievement of certain targets.

The fair value of PSUs with clinical development vesting conditions were determined to be equal to the fair market value of the Company's share price on the date of grant. The fair value of the TSR PSUs were derived from a Monte Carlo simulation model that used the following key assumptions:


Valuation date share price	$	17.57
Award term (years)	1.92
Volatility	70.62		%
Correlation coefficient	0.3508
Average peer group volatility	79.69		%
Average peer group correlation coefficient	0.4397
Risk free interest rate	2.84		%

The following table sets forth the outstanding PSUs associated with the TSR goal and related activity for the years ended December 31, 2023 and 2022:


	Performance Stock Units	Weighed Average Grant Date Fair Value
Unvested balance as of December 31, 2021
Granted	354,532	$	29.15
Vested	—	—
Unvested balance as of December 31, 2022	354,532	$	29.15
Forfeited	(25,782)	$	29.15
Unvested balance as of December 31, 2023	328,750	$	29.15

As of December 31, 2022 177,266 PSUs, with a weighted average grant date fair value of $17.57, associated with clinical development milestones met their vesting conditions. In March and July 2023 the second and the third clinical development vesting conditions were achieved and the remaining 531,792 PSUs relating to clinical development vesting

conditions vested, representing total stock based compensation of $7.3 million. There are no remaining PSUs with clinical development performance conditions outstanding as of December 31, 2023.

As of December 31, 2023, the Company had $2.6 million of unrecognized stock-based compensation expense related to unvested PSUs associated with market based vesting conditions are expected to be recognized over a remaining weighted-average period of 0.54 years.

2020 Employee Stock Purchase Plan

In June 2020, the Company adopted the 2020 Employee Stock Purchase Plan (the "2020 ESPP") and reserved 700,000 shares of common stock for future issuance under the plan. The 2020 ESPP is subject to automatic increases on January 1 of each calendar year, beginning January 1, 2021, by the lesser of (i) 1% of the outstanding shares on the immediately preceding December 31, (ii) 700,000 shares or (iii) such lesser amount as determined by, the compensation committee of the Board of Directors.

Under the 2020 ESPP, eligible employees may purchase shares of our common stock through payroll deductions that cannot exceed 15% of the employee’s salary. The 2020 ESPP provides for a six-month offering period. At the end of the purchase period, eligible employees are permitted to purchase shares of common stock at the lower of 85% of the fair market value at the beginning or end of the offering period subject to tax limitations on the total value of the purchase. The 2020 ESPP is considered a compensatory plan, and the Company recorded $0.6 million, $0.4 million and $0.5 million in stock-based compensation expense for years ended December 31, 2023, 2022 and 2021, respectively. During the years ended December 31, 2023, 2022 and 2021, 82,428 shares, 85,969 shares and 86,902 shares, respectively, of common stock were issued under the 2020 ESPP.

The Company used the Black-Scholes option pricing model to estimate stock-based compensation expense for the 2020 ESPP with the following assumptions:


	Year Ended December 31,
	2023	2022	2021
Risk-free interest rate	5.20% - 5.47%	0.60% -3.34%	0.06% -0.07%
Expected term of options (in years)	0.50	0.50	0.50
Expected stock price volatility	54.78% - 69.15%	63.17% - 82.02%	67.16% - 89.51%
Expected dividends	—%	—%	—%

Stock-Based Compensation Expense

The following table presents the classification of stock-based compensation expense during the years ended December 31, 2023, 2022 and 2021 (in thousands):


	Year Ended December 31,
	2023		2022		2021
Restricted stock awards	$	—	$	36	$	182
Stock options and ESPP	21,313		13,280		10,255
Restricted stock units	11,149		1,892		—
Performance-based restricted stock units	12,021		7,390		—
Total stock-based compensation expense	$	44,483	$	22,598	$	10,437
Research and development expenses	$	17,973	$	8,730	$	3,928
General and administrative expenses	$	26,510	$	13,867	$	6,509

Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2023	Dec. 31, 2022
Statement of Financial Position [Abstract]
Preferred stock, par value (USD per share)	$ 0.0001	$ 0.0001
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (USD per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	300,000,000	300,000,000
Common stock, shares issued (in shares)	59,921,002	48,941,254
Common stock, shares outstanding (in shares)	59,921,002	48,941,254

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2023

Share-Based Payment Arrangement [Abstract]

Summary of Black-Scholes Option Pricing Model to Estimate Stock-based Compensation Expense for Stock Option Awards

The Company used Black-Scholes option pricing model to estimate stock-based compensation expense for stock option awards with the following assumptions:


	Year Ended December 31,
	2023		2022		2021
	Min	Max	Min	Max	Min	Max
Expected volatility	80.97%	83.28%	73.78%	80.64%	74.83%	76.31%
Risk-free interest rate	3.42%	4.68%	1.64%	4.16%	0.61%	1.39%
Expected dividend	—	—	—	—	—	—
Expected term (in years)	5.31	6.08	5.33	6.08	5.44	6.08
Underlying common stock fair value	$15.25	$34.65	$4.92	$24.23	$15.20	$38.23

Summary of Option Activity Under the 2015 Plan and 2020 Plan

A summary of option activity under the 2015 Plan and the 2020 Plan is as follows:


	Number of Options	Weighted- Average Exercise Price per Share		Weighted- Average Remaining Contractual Term (in Years)	Aggregate Intrinsic Value (in thousands)
Outstanding as of December 31, 2022	5,569,567	$	13.34	7.96	$	43,696
Granted	2,158,764	$	27.22
Exercised	(534,706)	$	6.91
Forfeited	(240,138)	$	18.81
Outstanding as of December 31, 2023	6,953,487	$	17.95	7.70	$	32,646
Exercisable as of December 31, 2023	3,515,801	$	15.03	6.74	$	23,184
Vested and expected to vest as of December 31, 2023	6,953,487	$	17.95	7.70	$	32,646

Summary of Restricted Stock Activity

The following table sets forth the outstanding RSUs and related activity for the year ended December 31, 2023:


	Restricted Stock Units	Weighted Average Grant Date Fair Value
Unvested and outstanding as of December 31, 2022	507,925	$	17.43
Granted	683,703	$	34.36
Released	(247,488)	$	17.43
Forfeited	(69,392)	$	27.69
Unvested and outstanding as of December 31, 2023	874,748	$	29.85

Schedule of Share-Based Payment Award, Equity Instruments Other Than Options, Valuation Assumptions

The fair value of the TSR PSUs were derived from a Monte Carlo simulation model that used the following key assumptions:


Valuation date share price	$	17.57
Award term (years)	1.92
Volatility	70.62		%
Correlation coefficient	0.3508
Average peer group volatility	79.69		%
Average peer group correlation coefficient	0.4397
Risk free interest rate	2.84		%

Summary of Black-Scholes Option Pricing Model to Estimate Stock-based Compensation Expense for 2020 Employee Stock Purchase Plan

The Company used the Black-Scholes option pricing model to estimate stock-based compensation expense for the 2020 ESPP with the following assumptions:


	Year Ended December 31,
	2023	2022	2021
Risk-free interest rate	5.20% - 5.47%	0.60% -3.34%	0.06% -0.07%
Expected term of options (in years)	0.50	0.50	0.50
Expected stock price volatility	54.78% - 69.15%	63.17% - 82.02%	67.16% - 89.51%
Expected dividends	—%	—%	—%

Summary of Classification of Stock-based Compensation Expense

The following table presents the classification of stock-based compensation expense during the years ended December 31, 2023, 2022 and 2021 (in thousands):


	Year Ended December 31,
	2023		2022		2021
Restricted stock awards	$	—	$	36	$	182
Stock options and ESPP	21,313		13,280		10,255
Restricted stock units	11,149		1,892		—
Performance-based restricted stock units	12,021		7,390		—
Total stock-based compensation expense	$	44,483	$	22,598	$	10,437
Research and development expenses	$	17,973	$	8,730	$	3,928
General and administrative expenses	$	26,510	$	13,867	$	6,509

Share-Based Payment Arrangement, Restricted Stock and Restricted Stock Unit, Activity

The following table sets forth the outstanding PSUs associated with the TSR goal and related activity for the years ended December 31, 2023 and 2022:


	Performance Stock Units	Weighed Average Grant Date Fair Value
Unvested balance as of December 31, 2021
Granted	354,532	$	29.15
Vested	—	—
Unvested balance as of December 31, 2022	354,532	$	29.15
Forfeited	(25,782)	$	29.15
Unvested balance as of December 31, 2023	328,750	$	29.15

Debt

12 Months Ended

Dec. 31, 2023

Debt Disclosure [Abstract]

Debt Disclosure

Debt

In May 2022, as amended in October 2022, we entered into a term loan facility (the “Oxford Loan Agreement”) with Oxford Finance LLC (the "Lender") for up to $100.0 million. At closing, we entered into a term loan for $10.0 million and we decided not to draw upon the additional $65.0 million that became available to us over the course of 2023 as certain conditions related to the development of bexotegrast and one of our preclinical product candidates were satisfied. As of December 31, 2023, the time period to draw upon the additional $65.0 million had lapsed. In connection with the Oxford Loan Agreement, we granted a security interest in substantially all of our current and future assets. There are no warrants or financial covenants associated with the Oxford Loan Agreement.

Borrowings under the Oxford Loan Agreement bear interest at a rate per annum equal to 1-month term Secured Overnight Financing Rate (SOFR) plus 8.5%, subject to an agreed upon floor and cap. The Oxford Loan Agreement requires the Company to make monthly interest-only payments until July 1, 2026 with monthly interest and principal payments thereafter until the maturity date of May 1, 2027.

The estimated fair value of the term loan as of December 31, 2023 was measured using Level 3 inputs and approximates the carrying value recorded to the balance sheet. The effective interest rate for the term loan is 12.69% and interest expense during the years ended December 31, 2023 and 2022 was $1.3 million and $0.8 million, respectively.

Future maturities of debt as of December 31, 2023 are as follows (in thousands):


	As of December 31, 2023
2026	$	5,455
2027	4,545
Thereafter	—
Total	10,000
Less: unamortized debt issuance costs	(106)
Accretion of final payment	160
Total	$	10,054

- Definition

The entire disclosure for information about short-term and long-term debt arrangements, which includes amounts of borrowings under each line of credit, note payable, commercial paper issue, bonds indenture, debenture issue, own-share lending arrangements and any other contractual agreement to repay funds, and about the underlying arrangements, rationale for a classification as long-term, including repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, whether or not in compliance with debt covenants, and other matters important to users of the financial statements, such as the effects of refinancing and noncompliance with debt covenants.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1B

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
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-Name Accounting Standards Codification
-Section S99
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-Subparagraph (SX 210.4-08(c))
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+ Details

Common Stock

12 Months Ended

Dec. 31, 2023

Equity [Abstract]

Common Stock

As of December 31, 2023 and 2022, the Company had 300,000,000 authorized shares of common stock, at a par value of $0.0001 per share. The common stock has the following rights and privileges:

Voting

The holders of shares of common stock are entitled to one vote for each share of common stock held at any meeting of stockholders and at the time of any written action in lieu of a meeting.

Dividends

The holders of shares of common stock are entitled to receive dividends, when declared by the Company’s Board of Directors. Cash dividends may not be declared or paid to holders of shares of common stock until all unpaid dividends on the Preferred Stock have been paid in accordance with their terms. No dividends have been declared or paid by the Company since its inception.

Liquidation

The holders of shares of common stock are entitled to share ratably in the Company’s remaining assets available for distribution to its stockholders in the event of any voluntary or involuntary liquidation, dissolution or winding up of the Company or upon occurrence of a deemed liquidation event.

Shares reserved for future issuance


	December 31,
	2023	2022
Outstanding stock option awards	6,953,487	5,569,567
Vesting of RSUs	874,748	507,925
Vesting of PSUs*	328,752	531,796
Shares of common stock available for future grants under the 2020 Stock Option and Incentive Plan	2,882,239	2,937,769
Shares of common stock available for future issuance under the 2020 ESPP	805,756	888,184
Shares of common stock available for future issuance under the 2022 Inducement Plan	700,000	1,000,000
Total shares reserved for future issuance	12,544,982	11,435,241
*PSUs granted and outstanding based on target level of achievement of 100%.

- Definition

The entire disclosure for equity.

+ References

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+ Details

Property and Equipment, net (Tables)

12 Months Ended

Dec. 31, 2023

Property, Plant and Equipment [Abstract]

Summary of Property and Equipment, Net

Property and equipment, net consisted of the following (in thousands):


	December 31,
	2023		2022
Laboratory equipment	$	10,410	$	9,581
Leasehold improvements	1,663		1,650
Construction-in-progress	52		66
Computer equipment and software	124		30
Total property and equipment	12,249		11,327
Less: Accumulated depreciation	(8,682)		(6,841)
Total property and equipment, net	$	3,567	$	4,486

Net Loss Per Share Attributable to Common Stockholders - Summary of Potentially Dilutive Securities Excluded from Computation of Diluted Net Loss Per Share (Details) - shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	8,156,985	6,432,024	3,642,021
Performance-based restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Target level of achievement percentage	100.00%
Options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	6,953,487	5,569,567	3,620,180
Restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	874,748	507,925	0
Performance-based restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	328,750	354,532	0
Unvested restricted shares
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	0	0	21,841

Pay vs Performance Disclosure - USD ($) $ in Thousands	12 Months Ended
Pay vs Performance Disclosure - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pay vs Performance Disclosure
Net loss	$ (161,336)	$ (123,321)	$ (97,263)

- Definition

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

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-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-32

Reference 31: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 60B
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482689/260-10-45-60B

Reference 32: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
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-Name Accounting Standards Codification
-Section 50
-Paragraph 31
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-31

Reference 33: http://www.xbrl.org/2003/role/disclosureRef
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-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (c)
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-URI https://asc.fasb.org//1943274/2147482810/280-10-50-32

Reference 34: http://www.xbrl.org/2003/role/disclosureRef
-Topic 205
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483499/205-20-50-7

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-Name Accounting Standards Codification
-Section 45
-Paragraph 28
-Publisher FASB
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Reference 36: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1A
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482790/220-10-45-1A

Reference 37: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1B
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482790/220-10-45-1B

Reference 38: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(20))
-Publisher FASB
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-Topic 942
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(22))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483589/942-220-S99-1

+ Details

Preferred Stock (Details)	Dec. 31, 2023 class shares	Dec. 31, 2022 shares
Temporary Equity Disclosure [Abstract]
Number of classes of stock authorized \| class	2
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, shares outstanding (in shares)	0	0

Financial Instruments - Summary of Cash and Cash Equivalents, Money Market Funds and Short-term Investments by Significant Investment Category (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	$ 487,907	$ 327,771
Unrealized Gains	822	45
Unrealized Losses	(477)	(2,003)
Market Value	488,252	325,813
Short-term investments
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	430,666	299,459
Unrealized Gains	822	45
Unrealized Losses	(477)	(2,003)
Market Value	431,011	297,501
Cash equivalents
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	57,241	28,312
Unrealized Gains	0	0
Unrealized Losses	0	0
Market Value	57,241	28,312
Level 1 \| Money Market Funds
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	57,241	28,312
Unrealized Gains	0	0
Unrealized Losses	0	0
Market Value	57,241	28,312
Level 2 \| U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	27,250	4,446
Unrealized Gains	46	0
Unrealized Losses	(8)	(5)
Market Value	27,288	4,441
Level 2 \| U.S. Government Agency Securities
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	133,655	28,746
Unrealized Gains	563	0
Unrealized Losses	(132)	(111)
Market Value	134,086	28,635
Level 2 \| Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	269,761	266,267
Unrealized Gains	213	45
Unrealized Losses	(337)	(1,887)
Market Value	$ 269,637	$ 264,425

Leases (Tables)

12 Months Ended

Dec. 31, 2023

Leases [Abstract]

Summary of Operating Lease Liability

The undiscounted future non-cancellable lease payments of the Company's operating lease liability as of December 31, 2023 were as follows (in thousands):


Year ending December 31:	Operating Leases
2024	$	1,382
Total undiscounted lease payments	1,382
Less: Present value discount	(64)
Total current operating lease liabilities	1,318
Total non-current operating lease liabilities	$	—

Summary of Weighted-average Remaining Lease Terms and Discount Rates

The weighted-average remaining lease terms and discount rates related to the Company's operating leases were as follows:


	As of December 31,
	2023		2022
Weighted-average remaining lease term (in years)	0.6		2.3
Weighted-average discount rate	13.60	%	8.2	%

Summary of Operating and Variable Lease Cost

Lease expenses for the years ended December 31, 2023, 2022 and 2021 are as follows (in thousands)


	As of December 31,
	2023		2022		2021
Operating lease costs	$	2,771	$	2,501	$	2,300
Other variable costs	766		721		949
Total expense	$	3,537	$	3,222	$	3,249

Novartis Collaboration and License Agreement (the "Novartis Agreement") - Narrative (Details)	12 Months Ended
	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2019 researchTarget
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Accounts receivable	$ 0	$ 1,983,000
Novartis Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Contract assets	0	0
Contract liabilities	0	0
Novartis Agreement \| Novartis
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenues	1,600,000	9,700,000	$ 7,600,000
Accounts receivable	$ 0	2,000,000
Novartis Agreement \| Novartis \| Integrin Research Target Program
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenues		$ 4,000,000
Novartis Agreement \| Maximum \| Novartis
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of Integrin research targets \| researchTarget				3

Insider Trading Arrangements	3 Months Ended	12 Months Ended
Insider Trading Arrangements	Dec. 31, 2023 shares	Dec. 31, 2023 shares
Trading Arrangements, by Individual
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false
Mike Ouimette [Member]
Trading Arrangements, by Individual
Material Terms of Trading Arrangement		On October 4, 2023, Mike Ouimette, our General Counsel, entered into a trading plan, or the Ouimette 10b5-1 Sales Plan, intended to satisfy the affirmative defense of Rule 10b5-1(c) under the Exchange Act. Under the Ouimette 10b5-1 Sales Plan, an aggregate of 57,074 shares of the Company’s common stock and up to 33% of the net shares Mr. Ouimette may receive from the vesting of certain outstanding RSU and PSU awards from time to time between January 16, 2024 and July 1, 2024 (the “Ouimette Authorized Shares”) may be sold. Due to vesting conditions of the awards and the number of shares withheld for taxes, to be determined only on the vesting date and market conditions, the number of shares actually sold under the Ouimette 10b5-1 Sales Plan may be less than the maximum number of shares that can be sold. The Ouimette 10b5-1 Sales Plan, which was entered into during an open trading window under the Company’s insider trading policy, will be in effect until the earlier of (1) December 31, 2024, or (2) the date on which all Ouimette Authorized Shares have been sold under the Ouimette 10b5-1 Sales Plan.
Name	Mike Ouimette
Title	General Counsel
Rule 10b5-1 Arrangement Adopted	true
Adoption Date	October 4, 2023
Arrangement Duration	454 days
Aggregate Available	57,074	57,074
Eric Lefebvre [Member]
Trading Arrangements, by Individual
Material Terms of Trading Arrangement		On December 7, 2023, Eric Lefebvre, our Chief Medical Officer, entered into a trading plan, or the Lefebvre 10b5-1 Sales Plan, intended to satisfy the affirmative defense of Rule 10b5-1(c) under the Exchange Act. Under the Lefebvre 10b5-1 Sales Plan, an aggregate of 111,781 shares of the Company’s common stock may be sold (such aggregate amount, which may be reduced by any shares sold prior pursuant to a prior trading plan adopted by Dr. Lefebvre on December 13, 2022 and prior to initiation of sales pursuant to the Lefebvre 10b5-1 Sales Plan, the “Lefebvre Authorized Shares”). The Lefebvre 10b5-1 Sales Plan, which was entered into during an open trading window under the Company’s insider trading policy, will be in effect until the earlier of (1) March 7, 2025, or (2) the date on which all Lefebvre Authorized Shares have been sold under the Lefebvre 10b5-1 Sales Plan.
Name		Eric Lefebvre
Title		Chief Medical Officer
Rule 10b5-1 Arrangement Adopted		true
Adoption Date		December 7, 2023
Arrangement Duration	456 days
Aggregate Available	111,781	111,781
Bernard Coulie [Member]
Trading Arrangements, by Individual
Material Terms of Trading Arrangement		On December 13, 2023, Bernard Coulie, our Chief Executive Officer, entered into a trading plan, or the Coulie 10b5-1 Sales Plan, intended to satisfy the affirmative defense of Rule 10b5-1(c) under the Exchange Act. Under the Coulie 10b5-1 Sales Plan, an aggregate of 80,000 shares of the Company’s common stock may be sold. The Coulie 10b5-1 Sales Plan, which was entered into during an open trading window under the Company’s insider trading policy, will be in effect until the earlier of (1) December 31, 2024, or (2) the date on which the maximum number of shares of the Company’s common stock have been sold under the Coulie 10b5-1 Sales Plan.
Name	Bernard Coulie
Title	Chief Executive Officer
Rule 10b5-1 Arrangement Adopted	true
Adoption Date	December 13, 2023
Arrangement Duration	384 days
Aggregate Available	80,000	80,000

Debt - Narrative (Details) - USD ($)	1 Months Ended	12 Months Ended
Debt - Narrative (Details) - USD ($)	Oct. 31, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	May 31, 2022
Debt Instrument [Line Items]
Proceeds from term loan		$ 0	$ 10,000,000	$ 0
Interest expense		$ 1,267,000	791,000	$ 0
Loan Agreement \| Term Loan Facility
Debt Instrument [Line Items]
Term loan facility	$ 100,000,000
Proceeds from term loan	$ 10,000,000
Effective interest rate for the term loan		12.69%
Interest expense		$ 1,300,000	$ 800,000
Loan Agreement \| Term Loan Facility \| Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate
Debt Instrument [Line Items]
Loan agreement interest rate	8.50%
Loan Agreement \| Term Loan Facility \| Debt Draw, Tranche Two
Debt Instrument [Line Items]
Amount undrawn					$ 65,000,000

Defined Contribution Plan (Details) - USD ($) $ in Millions	12 Months Ended
Defined Contribution Plan (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Retirement Benefits [Abstract]
Payment made under defined contribution plan	$ 1.0	$ 0.8	$ 0.6

Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2023

Fair Value Disclosures [Abstract]

Summary of Cash and Cash Equivalents, Money Market Funds and Short-term Investments by Significant Investment Category

The following tables show the Company’s cash and cash equivalents and short-term investments by significant investment category as of December 31, 2023 and 2022 (in thousands):


		As of December 31, 2023								As of December 31, 2022
		Adjusted Cost		Unrealized Gains		Unrealized Losses		Market Value		Adjusted Cost		Unrealized Gains		Unrealized Losses		Market Value
Money Market Funds	Level 1	$	57,241	$	—	$	—	$	57,241	$	28,312	$	—	$	—	$	28,312
U.S. Treasury securities	Level 2	27,250		46		(8)		27,288		4,446		—		(5)		4,441
U.S. Government Agency Securities	Level 2	133,655		563		(132)		134,086		28,746		—		(111)		28,635
Corporate debt securities	Level 2	269,761		213		(337)		269,637		266,267		45		(1,887)		264,425
Total financial assets		$	487,907	$	822	$	(477)	$	488,252	$	327,771	$	45	$	(2,003)	$	325,813


	As of December 31, 2023								As of December 31, 2022
Classified as:	Adjusted Cost		Unrealized Gains		Unrealized Losses		Market Value		Adjusted Cost		Unrealized Gains		Unrealized Losses		Market Value
Cash equivalents	$	57,241	$	—	$	—	$	57,241	$	28,312	$	—	$	—	$	28,312
Short-term investments	430,666		822		(477)		431,011		299,459		45		(2,003)		297,501
Total	$	487,907	$	822	$	(477)	$	488,252	$	327,771	$	45	$	(2,003)	$	325,813

Summery of Remaining Contractual Maturities of Company’s Short-term Investments

The following summarizes the remaining contractual maturities of the Company’s short-term investments as of December 31, 2023:


	Adjusted Cost		Market Value
Mature in 1 year or less	$	316,700	$	316,366
Mature in 1 to 2 years	113,966		114,645
Total	$	430,666	$	431,011

Stock-Based Compensation - Summary of Outstanding PSUs Associated with the TSR goal (Details) - Performance-Based Restricted Stock Units, TSR Goal - $ / shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Outstanding and unvested, beginning balance (in shares)	354,532
Granted (in shares)		354,532
Vested (in shares)		0
Forfeited (in shares)	(25,782)
Outstanding and unvested, ending balance (in shares)	328,750	354,532
Weighted Average Grant Date Fair Value
Weighted-Average Grant Date fair value, Outstanding and unvested, beginning balance (USD per share)	$ 29.15
Weighted-Average Grant Date fair value, Issued (USD per share)		29.15
Weighted-Average Grant Date fair value, Vested (USD per share)		0
Weighted-Average Grant Date fair value, forfeited (USD per share)		29.15
Weighted-Average Grant Date fair value, Outstanding and unvested, ending balance (USD per share)	$ 29.15	$ 29.15

Debt (Tables)

12 Months Ended

Dec. 31, 2023

Debt Disclosure [Abstract]

Summary of Maturities of Long-Term Debt

Future maturities of debt as of December 31, 2023 are as follows (in thousands):


	As of December 31, 2023
2026	$	5,455
2027	4,545
Thereafter	—
Total	10,000
Less: unamortized debt issuance costs	(106)
Accretion of final payment	160
Total	$	10,054

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2023

Accounting Policies [Abstract]

Basis of Presentation

The accompanying financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”). Certain prior year reported amounts have been reclassified to conform with the current period presentation.

Use of Estimates

The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, and expenses as well as the disclosure of contingent assets and liabilities in the financial statements and accompanying notes. On an ongoing basis, management evaluates its estimates, including those related to revenue recognition, accruals for research and development costs, fair value of assets, stock-based compensation, income taxes and uncertain tax positions. Management bases its estimates on historical experience and on various other market-specific and relevant assumptions that management believes to be reasonable under the circumstances, however, actual results may differ from those estimates.

Revenue Recognition

The Company accounts for revenues in accordance with Accounting Standards Codification Topic 606, Revenue from Contracts with Customers (Topic 606). To determine revenue recognition for arrangements that fall within the scope of ASC 606, we perform the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) we satisfy a performance obligation. We only apply the five-step model to contracts when it is probable that we will collect the consideration we are entitled to in exchange for the goods or services we transfer to the customer.

At contract inception, we assess the goods or services promised within each contract, determine those that are performance obligations, and assess whether each promised good or service is distinct. We then recognize as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied. To date, our revenues have been generated solely from the Collaboration and License Agreement with Novartis (the “Novartis Agreement”). The Novartis Agreement includes licenses of intellectual property, cost reimbursements, research and development services, upfront signing fees, milestone payments and royalties on future licensee’s product sales.

As part of accounting for this arrangement, we must apply judgment to determine whether the performance obligations are distinct, and develop assumptions in determining the stand-alone selling price for each distinct performance obligation identified in the contract. To determine the stand-alone selling price, we rely on assumptions which may include

forecasted revenues, development timelines, reimbursement rates for personnel costs, discount rates and probabilities of technical and regulatory success.

Licenses of Intellectual Property

If the license to our intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, we recognize revenues from non-refundable, up-front fees allocated to the license when the license is transferred to the licensee and the licensee is able to use and benefit from the license. For licenses that are bundled with other promises, we utilize judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenues. We evaluate the measure of progress each reporting period and, if necessary, adjust the measure of performance and related revenue recognition.

Milestone Payments

At the inception of an arrangement that includes development milestone payments, we evaluate whether the milestones are considered probable of being reached and estimate the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant revenue reversal would not occur, the associated milestone value is included in the transaction price. The transaction price is then allocated to each performance obligation on a relative stand-alone selling price basis, for which we recognize revenue as or when the performance obligations under the contract are satisfied. At the end of each reporting period, we re-evaluate the probability of achievement of such development milestones and any related constraint and, if necessary, adjust our estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect collaboration and license revenue in the period of adjustment.

Research and development services

Amounts related to research and development services are recognized as the related services or activities are performed, in accordance with the contract terms. The cost associated with full-time equivalent researchers is estimated each period and billable to Novartis based at specified full-time equivalent rates.

Royalties

The sales-based royalties, including milestone payments based on the level of sales, are considered to be predominately related to the license included in the arrangement, and we will recognize revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). To date, we have not recognized any royalty revenue from the Novartis Agreement.

We recognize contract assets when we have a right to consideration in exchange for goods or services that the Company has transferred to a customer when that right is conditional on something other than the passage of time. A receivable will be recorded on the balance sheet when the Company has unconditional rights to consideration (i.e., only the passage of time is required before payment becomes due). A contract liability is an obligation to transfer goods or services for which the Company has received consideration, or for which an amount of consideration is due from the customer. Receivables cannot be netted against contract liabilities and would be presented separately from contract assets. Contract assets and contract liabilities are netted at the contract level.

Fair Value Measurements

The Company defines fair value as the price that would be received from selling an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. When determining the fair value measurements for assets and liabilities which are required to be recorded at fair value, the Company considers the principal or most advantageous market in which to transact and the market-based risk. Fair value accounting is applied for all financial assets and liabilities and non-financial assets and liabilities that are recognized or disclosed at fair value in the financial statements on a recurring basis. The carrying amount of the Company’s financial instruments, including cash and cash equivalents, tax credit receivable, accounts receivable, prepaid expenses and other current assets, accounts payable and accrued liabilities approximate fair value due to their short-term maturities.

•Level 1—Inputs are unadjusted, quoted prices in active markets for identical assets or liabilities at the measurement date;

•Level 3—Unobservable inputs that are significant to the measurement of the fair value of the assets or liabilities that are supported by little or no market data.

Concentration of Credit Risk and Other Risks and Uncertainties Policy

Concentration of Credit Risk and Other Risks and Uncertainties

Financial instruments that potentially subject the Company to a concentration of credit risk consist of cash and cash equivalents, short-term investments and accounts receivable. The Company invests in money market funds, U.S. Treasury securities, government notes and corporate debt securities. The Company limits its credit risk associated with its cash and cash equivalents by placing them with banks and institutions it believes are highly credit worthy and in highly rated investments. However, the Company had deposits in excess of the Federal Deposit Insurance Corporation (“FDIC”)

insured limit of $250,000. The Company performs credit evaluations of its customer, and the risk with respect to accounts receivable is further mitigated by the short duration of customer payment terms, generally within 60 days, and the pedigree of the customer base. During the years ended December 31, 2023, 2022 and 2021, Novartis accounted for 100% of the Company’s revenue and accounts receivable.

The Company’s future results of operations involve several other risks and uncertainties. Factors that could affect the Company’s future operating results and cause actual results to vary materially from expectations include, but are not limited to, uncertainty of results of clinical trials and reaching milestones, uncertainty of regulatory approval of the Company’s product candidates, uncertainty of market acceptance of the Company’s product candidates, competition from substitute products, including those that may be developed or marketed by larger companies, securing and protecting intellectual property, strategic relationships and dependence on key individuals and sole source suppliers.

The Company’s product candidates require approvals from the U.S. Food and Drug Administration (“FDA”) and comparable foreign regulatory agencies prior to commercial sales in their respective jurisdictions. There can be no assurance that any product candidates will receive the necessary approvals. If the Company was denied approval, approval was delayed or the Company was unable to maintain approval for any product candidate, it could have a materially adverse impact on the Company.

Segments

The Company operates and manages its business as one reportable and operating segment, which is the business of developing and commercializing novel therapies for fibrotic diseases. The Company’s chief executive officer, who is the chief operating decision maker, reviews financial information on an aggregate basis for allocating and evaluating financial performance. The single operating segment constitutes all of the Company activity, the chief operating decision maker regularly reviews the entity-wide operating results and performance. All long-lived assets are maintained in the United States of America.

Cash and Cash Equivalents, Restricted Cash

Cash and Cash Equivalents

The Company considers all highly liquid investments purchased with original maturities of three months or less from the purchase date to be cash equivalents. Cash equivalents consist primarily of amounts invested in Money Market Funds, United States (“U.S.”) treasury securities, U.S. government agency securities and corporate debt securities and are stated at fair value.

Restricted Cash

Our restricted cash balance of $1.4 million as of December 31, 2023 represented cash required to be held as collateral by a financial institution to guarantee lease payments due to our landlord at Oyster Point Blvd, South San Francisco, California (the "Oyster Point Lease").

Short-Term Investments

The Company’s short-term investments consist of U.S. Treasury securities, U.S. government agency securities and corporate debt securities with remaining maturities beyond three months at the date of purchase. The Company has classified and accounted for its short-term investments as available-for-sale securities as the Company may sell these securities at any time even prior to maturity and such investments represent cash available for current operations. As a result, short-term investments may include securities with maturities beyond twelve months that are classified within current assets in the Balance Sheets. As of December 31, 2023 and 2022, all of the Company’s short-term investments were classified as available-for-sale and were carried at fair market value with unrealized losses recorded in other comprehensive gain (loss) in the statements of operations and comprehensive loss. See Note 3 for further details.

The Company records an allowance for credit losses using an expected loss model. Credit losses are limited to the amount by which the amortized cost of an investment exceeds its fair value. A previously recognized credit loss may be decreased in subsequent periods if the Company’s estimate of fair value for the investment increases. To determine whether to record a credit loss, the Company considers issuer specific credit ratings and historical losses as well as current economic conditions and its expectations for future economic conditions. The Company has not recorded any credit losses during the three years ended December 31, 2023, 2022 and 2021.

Interest and other income(expense)

Interest and other income (expense) includes interest income from our short-term investment portfolio.

Property and Equipment, Net

Property and equipment are recorded at cost net of accumulated depreciation and amortization. Property and equipment are depreciated using the straight-line method over the estimated useful lives of the assets. The useful lives of property and equipment are as follows:


Laboratory equipment			5 years
Computer equipment and software			3 years
Leasehold improvements			Shorter of remaining lease term or estimated useful life

Upon retirement or sale of the assets, the cost and related accumulated depreciation and amortization are removed from the balance sheets and the resulting gain or loss is recorded to the statements of operations and comprehensive loss. Repairs and maintenance are expensed as incurred.

Leases

The Company determines if an arrangement contains a lease at the inception of the contract and a records right-of-use (“ROU”) asset and lease liability on the balance sheet at lease commencement based on the present value of remaining lease payments over the lease term. The Company only considers payments that are fixed and determinable at the time of commencement.

For leases with an initial term greater than 12 months, lease liabilities are recognized based on the present value of the future minimum lease payments discounted by the Company’s estimated incremental borrowing rate. The Company measures ROU assets based on the corresponding lease liability adjusted for (i) payments made to the lessor at or before the commencement date, (ii) initial direct costs incurred and (iii) tenant incentives under the lease. The Company’s lease terms may include options to extend or terminate the lease when it is reasonably certain that it will exercise that option. Lease expense for minimum lease payments is recognized on a straight-line basis over the lease term.

The Company calculates the present value of future minimum lease payments using its estimated incremental borrowing rate when the discount rate implicit in the lease is not known. The incremental borrowing rate is the rate of interest that a lessee would have to pay to borrow on a collateralized basis over a similar term at an amount equal to the lease payments in a similar economic environment. In determining its incremental borrowing rate, the Company gives consideration to its credit risk, term of the lease, total lease payments and an analysis of peer companies with profiles similar to its own.

The Company has elected the short-term lease practical expedient to exclude leases with a term less than 12 months from its ROU assets and lease liabilities. The Company records rent expense for short-term leases in its statements of operations on a straight-line basis over the lease term and records variable lease payments as incurred. The Company has also elected to not separate lease and non-lease components and, as a result, accounts for any lease and non-lease components as a single lease component.

Impairment of Long-Lived Assets

Long-lived assets are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to future net cash flows expected to be generated by the asset. If the carrying amount of an asset exceeds its estimated future cash flows, an impairment charge is recognized by the amount by which the carrying amount of the asset exceeds the fair value of the asset. There was no impairment of long-lived assets during the years ended December 31, 2023, 2022 and 2021.

Research and Development Expenses

Research and development costs are expensed as incurred. Research and development expenses consist primarily of personnel costs for the Company’s research and development employees. Also included are non-personnel costs such as fees paid to consultants and third parties for preclinical and clinical studies, research and development services, laboratory supplies and equipment maintenance costs, license costs, contract manufacturing costs and allocations of facility related costs. The Company estimates preclinical and clinical studies and research expenses based on the services performed, pursuant to contracts with research institutions that conduct and manage preclinical and clinical studies and research services on its behalf. We estimate the amount of work completed through review of detailed budgets and timelines included in our contracts and agreements, and update these estimates with information obtained from third-party service providers and internal personnel on a quarterly basis. If the actual timing of the performance of services or the level of effort varies from the original estimates, the Company will adjust the accrual accordingly. Payments made to third parties

under these arrangements in advance of the performance of the related services are recorded as prepaid expenses and are expensed as services are rendered.

Payments associated with licensing agreements to acquire exclusive licenses to develop, use, manufacture and commercialize products that have not reached technological feasibility and do not have alternate commercial use are expensed as incurred.

Stock-Based Compensation

The Company’s stock-based equity awards include restricted stock awards, stock options, restricted stock units ("RSUs") and performance-based restricted stock units ("PSUs"), issued under the Company's 2020 Stock Option and Incentive Plan (the “2020 Plan”), 2022 Inducement Plan ("Inducement Plan") and shares issued under the Company’s 2020 Employee Stock Purchase Plan (“ESPP”). Stock-based compensation for awards that are granted to employees is accounted at fair value on the award grant date and the expense is recognized over the period the employee is required to provide service in exchange for the award, which is generally on a straight-line basis over the vesting period of the award. The expense is recorded in either research and development or general and administrative expenses in the statements of operations and comprehensive loss based on the function to which the related services are provided. Forfeitures are accounted for as they occur.

The Company utilizes the Monte Carlo simulation model with significant inputs including volatility and closing price of stock on grant for estimating the fair value of equity awards with market-based vesting conditions and uses the closing price of common stock on the date of grant for PSUs and RSUs with a performance or service-based vesting condition.

The Black-Scholes option-pricing model, used to estimate fair value of stock options with service-based vesting conditions, requires the use of the following assumptions:

•Expected term—The expected term represents the period that the stock-based awards are expected to be outstanding. The expected term for the Company’s stock options was calculated utilizing the simplified method, which represents the average of the weighted-average vesting term and the contract period of the awards. The expected term for the ESPP is the offering period.

•Expected volatility—Prior to the Company being public, the Company did not have any trading history for its common stock, the expected volatility was estimated based on the average historical volatilities of common stock of comparable publicly traded entities over a period equal to the expected term of the stock option grants. The comparable companies were chosen based on their size, stage in the life cycle or area of specialty. As the Company went public in June 2020, the Company will continue to apply this process for stock options and ESPP awards until enough historical information regarding the volatility of its stock price becomes available.

•Risk-free interest rate—The risk-free interest rate is based on the U.S. Treasury yield in effect at the time of grant for zero-coupon U.S. Treasury notes with maturities approximately equal to the expected term of the awards.

•Expected dividend—The Company has never paid dividends on the common stock and has no plans to pay dividends on the common stock. Therefore, the Company used an expected dividend yield of zero.

Income Taxes

The Company provides for income taxes under the asset and liability method. Current income tax expense or benefit represents the amount of income taxes expected to be payable or refundable for the current year. Deferred income tax assets and liabilities are determined based on differences between the financial statement reporting and tax basis of assets and liabilities and net operating loss and credit carryforwards and are measured using the enacted tax rates and laws that will be in effect when such items are expected to reverse. Deferred income tax assets are reduced, as necessary, by a valuation allowance when management determines it is more likely than not that some or all the tax benefits will not be realized.

The Company accounts for uncertain tax positions in accordance with ASC No. 740, Income Taxes. The Company assesses all material positions taken in any income tax return, including all significant uncertain positions, in all tax years that are still subject to assessment or challenge by relevant taxing authorities. Assessing an uncertain tax position begins with the initial determination of the position’s sustainability and is measured at the largest amount of benefit that is greater than fifty percent likely of being realized upon ultimate settlement. As of each balance sheet date, unresolved uncertain tax positions must be reassessed, and the Company will determine whether (i) the factors underlying the sustainability assertion have changed and (ii) the amount of the recognized tax benefit is still appropriate. The recognition and

measurement of tax benefits requires significant judgment. Judgments concerning the recognition and measurement of a tax benefit might change as new information becomes available.

The Company includes any penalties and interest expense related to income taxes as a component of income tax expense, as necessary.

Comprehensive Loss

Comprehensive loss includes net loss as well as other changes in stockholders' equity that result from transactions and economic events other than those with stockholders. The Company's comprehensive gain (loss) represents unrealized losses on short-term investments.

Interest and other income (expense)

Short-Term Investments

Interest and other income(expense)

Interest and other income (expense) includes interest income from our short-term investment portfolio.

Net Loss Per Share

Basic net loss per share is computed by dividing net loss attributed to common stockholders by the weighted-average number of shares of common stock outstanding during the period. Diluted net loss per share is computed using the weighted-average number of shares of common stock outstanding during the period and, if dilutive, the weighted-average number of potential shares of common stock.

Common stock equivalent shares are excluded from the computation of diluted net loss or income per share if their effect is antidilutive. In periods in which the Company reports a net loss attributable to common stockholders, diluted net loss per share attributable to common stockholders is generally the same as basic net loss per share attributable to common stockholders since dilutive common shares are not assumed to have been issued if their effect is antidilutive. The Company reported a net loss attributable to common stockholders during the years ended December 31, 2023, 2022 and 2021.

Recently Adopted Accounting Pronouncements

In November 2023, the FASB issued ASU No. 2023-07, Segment Reporting (Topic 280), or Topic 280, which improve reportable segment disclosure requirements, primarily through enhanced disclosures about significant segment expenses. We adopted the provisions of Topic 280 and the adoption did not have a material impact to our financial statements.

Recently Announced Accounting Pronouncements

In October 2023, the Financial Accounting Standards Board ("FASB") issued ASU 2023-06 "Disclosure Improvements - Codification Amendments in Response to the SEC's Disclosure Update and Simplification Initiative", which amends the disclosure or presentation requirements related to various subtopics in the FASB Accounting Standard Codification (the "Codification"). This ASU will become effective on the date the SEC removes the applicable disclosure from Regulation S-X or Regulation S-K, with early adoption prohibited. If by June 30, 2027, the SEC has not removed the applicable requirement from Regulation S-X or Regulation S-K, the pending content of the related amendment will be removed from the Codification and will not be become effective for any entity. The Company expects the new guidance will have an immaterial impact on its financial statements, and intends to adopt the guidance when it becomes effective.

In December 2023, the FASB issued ASU 2023-09 "Income Taxes (Topic 740): Improvements to Income Tax Disclosures", which expands disclosures in an entity’s income tax rate reconciliation table and regarding cash taxes paid both in the U.S. and foreign jurisdictions. The guidance is effective for the Company beginning in the fourth quarter of fiscal year 2026. The Company expects the new guidance will have an immaterial impact on its financial statements, and intends to adopt the guidance prospectively when it becomes effective in the fourth quarter of fiscal year 2026.

Related Party Transactions	12 Months Ended
Related Party Transactions	Dec. 31, 2023
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions In June 2022 and 2021, the Company granted 15,000 and 26,572 stock options with a grant date fair value of $0.1 million and $0.5 million to partners of Third Rock Ventures who were also serving as non-employee directors on the Company's Board of Directors. Both of the non-employee directors resigned from the Company's Board of Directors in 2022. The shares of common stock subject to these options vest have all vested. The stock-based compensation expense related to these options was immaterial during the years ended December 31, 2022, and 2021. There were no related party transactions during the year ended December 31, 2023.

- Definition

The entire disclosure for related party transactions. Examples of related party transactions include transactions between (a) a parent company and its subsidiary; (b) subsidiaries of a common parent; (c) and entity and its principal owners; and (d) affiliates.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480990/946-20-50-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
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-Name Accounting Standards Codification
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
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-Paragraph 2
-Subparagraph (c)
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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-Subparagraph (e)
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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-Paragraph 1
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Reference 10: http://www.xbrl.org/2003/role/disclosureRef
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Reference 11: http://www.xbrl.org/2003/role/disclosureRef
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Reference 12: http://www.xbrl.org/2003/role/disclosureRef
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Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
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-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483326/850-10-50-1

+ Details

Net Loss Per Share Attributable to Common Stockholders

12 Months Ended

Dec. 31, 2023

Earnings Per Share [Abstract]

Net Loss Per Share Attributable to Common Stockholders

The following common share equivalents were excluded from the computation of diluted net loss per share attributable to common stockholders for the periods presented, because including them would have been antidilutive:


	Year Ended December 31,
	2023	2022	2021
Options to purchase common stock	6,953,487	5,569,567	3,620,180
Restricted stock units	874,748	507,925	—
Performance-based restricted stock units*	328,750	354,532	—
Unvested restricted shares	—	—	21,841
Total	8,156,985	6,432,024	3,642,021
*PSUs outstanding based on target level of achievement of 100%.

Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive (Loss) Gain	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2020		35,552,795
Beginning balance at Dec. 31, 2020	$ 283,061	$ 3	$ 400,918	$ (32)	$ (117,828)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under benefit plans (in shares)		427,342
Issuance of common stock under benefit plans	2,984		2,984
Vesting of restricted stock awards (in shares)		103,164
Vesting of restricted stock awards	9		9
Stock-based compensation expense	10,437		10,437
Net unrealized (loss) gain on short-term investments	(169)			(169)
Net loss	(97,263)				(97,263)
Ending balance (in shares) at Dec. 31, 2021		36,083,301
Ending balance at Dec. 31, 2021	199,059	$ 3	414,348	(201)	(215,091)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued in a public offering, net of offering expenses (in shares)		12,432,432
Common stock issued in a public offering, net of offering expenses	215,401	$ 2	215,399
Issuance of common stock under benefit plans (in shares)		403,680
Issuance of common stock under benefit plans	1,360		1,360
Vesting of restricted stock awards (in shares)		21,841
Vesting of restricted stock awards	2		2
Stock-based compensation expense	22,598		22,598
Net unrealized (loss) gain on short-term investments	(1,757)			(1,757)
Net loss	$ (123,321)				(123,321)
Ending balance (in shares) at Dec. 31, 2022	48,941,254	48,941,254
Ending balance at Dec. 31, 2022	$ 313,342	$ 5	653,707	(1,958)	(338,412)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued in a public offering, net of offering expenses (in shares)		9,583,334
Common stock issued in a public offering, net of offering expenses	269,782	$ 1	269,781
Issuance of common stock under benefit plans (in shares)		1,396,414
Issuance of common stock under benefit plans	5,002		5,002
Stock-based compensation expense	44,483		44,483
Net unrealized (loss) gain on short-term investments	2,303			2,303
Net loss	$ (161,336)				(161,336)
Ending balance (in shares) at Dec. 31, 2023	59,921,002	59,921,002
Ending balance at Dec. 31, 2023	$ 473,576	$ 6	$ 972,973	$ 345	$ (499,748)

Income Taxes - Summary of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Deferred tax assets:
Net operating losses	$ 78,452	$ 65,689
Research and development credits	29,559	19,688
Accrued expenses	2,211	387
Other	1,350	1,706
Capitalized research and development	34,769	13,900
Lease liability	369	1,638
Stock based compensation	8,291	5,073
Total deferred tax assets	155,001	108,081
Deferred tax liabilities:
Fixed asset basis	(123)	(258)
Prepaid expenses	(598)	(630)
Right of use asset	(339)	(1,509)
Total deferred tax liabilities	(1,060)	(2,397)
Valuation allowance	153,941	105,684	$ 67,684
Net deferred taxes	$ 0	$ 0

Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Current assets
Cash and cash equivalents	$ 63,234	$ 33,685
Short-term investments	431,011	297,502
Accounts receivable	0	1,983
Tax credit receivable	0	83
Prepaid expenses and other current assets (Note 5)	11,257	7,058
Total current assets	505,502	340,311
Property and equipment, net	3,567	4,486
Operating lease right-of-use assets	1,211	5,422
Restricted cash	1,482	0
Other non-current assets	392	394
Total assets	512,154	350,613
Current liabilities
Accounts payable	4,531	1,580
Accrued research and development	12,456	11,218
Accrued liabilities (Note 6)	10,219	8,658
Lease liabilities, current	1,318	2,457
Total current liabilities	28,524	23,913
Lease liabilities, non-current	0	3,429
Long-term debt (Note 7)	10,054	9,929
Total liabilities	38,578	37,271
Commitments and Contingencies (Note 13)
Stockholders’ equity
Preferred stock, $0.0001 par value 10,000,000 shares authorized at December 31, 2023 and 2022, none issued or outstanding at December 31, 2023 and 2022	0	0
Common stock, $0.0001 par value; 300,000,000 shares authorized at December 31, 2023 and 2022; and 59,921,002 and 48,941,254 shares issued and outstanding at December 31, 2023 and December 31, 2022, respectively;	6	5
Additional paid-in capital	972,973	653,707
Accumulated deficit	(499,748)	(338,412)
Accumulated other comprehensive gain (loss)	345	(1,958)
Total stockholders’ equity	473,576	313,342
Total liabilities and stockholders’ equity	$ 512,154	$ 350,613

Income Taxes

12 Months Ended

Dec. 31, 2023

Income Tax Disclosure [Abstract]

Income Taxes

The Company had a pre-tax U.S. book loss of $161.3 million, $123.3 million, and $97.3 million, for the years ended December 31, 2023, 2022 and 2021, respectively. During the years ended December 31, 2023, 2022 and 2021, the Company did not record an income tax provision. The Company will continue to maintain a 100% valuation allowance on total deferred tax assets. The Company believes it is more likely than not that the related deferred tax assets will not be realized.

A reconciliation of the U.S. federal statutory income tax rate to the Company’s effective income tax rate is as follows:


	Year Ended December 31,
	2023		2022		2021
Income tax computed at federal statutory rate	21.0	%	21.0	%	21.0	%
State taxes, net of federal tax benefit	6.7	%	7.3	%	7.7	%
General business credit—federal	5.3	%	3.6	%	5.3	%
Stock-based compensation	0.9	%	(1.0)	%	(0.7)	%
Other permanent differences	0.1	%	(0.4)	%	(0.1)	%
Section 162(m)	(3.8)	%	—	%	—	%
Change in valuation allowance	(30.2)	%	(30.5)	%	(33.2)	%
Effective income tax rate	—	%	—	%	—	%

Net deferred tax assets and liabilities consisted of the following (in thousands):


	December 31,
	2023		2022
Deferred tax assets:
Net operating losses	$	78,452	$	65,689
Research and development credits	29,559		19,688
Accrued expenses	2,211		387
Other	1,350		1,706
Capitalized research and development	34,769		13,900
Lease liability	369		1,638
Stock based compensation	8,291		5,073
Total deferred tax assets	155,001		108,081
Deferred tax liabilities:
Fixed asset basis	(123)		(258)
Prepaid expenses	(598)		(630)
Right of use asset	(339)		(1,509)
Total deferred tax liabilities	(1,060)		(2,397)
Valuation allowance	153,941		105,684
Net deferred taxes	$	—	$	—

Net operating losses and tax credit carryforwards were as follows (in thousands):


	December 31, 2023		Expiration Year
Net operating losses, federal (starting from January 1, 2018)	$	212,005	Does not expire
Net operating losses, federal (before January 1, 2018)	$	29,486	2035-2037
Net operating losses, state	$	397,559	2035-2043
Tax credits, federal	$	31,512	2036-2043
Tax credits, state	$	7,145	Does not expire

Utilization of the net operating loss carryforwards and research credit carryforwards may be subject to an annual limitation due to the ownership percentage change limitations provided by the Internal Revenue Code (“IRC”) and similar state provisions. Annual limitations may result in the expiration of the net operating losses and tax credit carryforwards before they are utilized. The Company performed a IRC Section 382 analysis through December 31, 2023 and does not expect any previous ownership changes to result in a limitation that will reduce the total amount of net operating loss and tax credit carryforwards disclosed that can be utilized. Subsequent ownership changes may affect the limitation in future years.

During the years ended December 31, 2023 and 2022, the Company recorded a full valuation allowance on federal and state deferred balances since management does not forecast the Company to be in a profitable position in the near

future. Changes in the valuation allowance for deferred tax assets during the years ended December 31, 2023 and 2022 related primarily to the increases in net operating loss carryforwards and research and development tax credit carryforwards and were as follows (in thousands):


	Year Ended December 31,
	2023		2022
Valuation allowance at the beginning of the year	$	105,684	$	67,684
Increases recorded to income tax provision	48,257		38,000
Valuation allowance at the end of the year	$	153,941	$	105,684

The Company’s U.S. federal and state income tax returns are generally subject to tax examinations for the tax years ended December 31, 2018 through December 31, 2023. There are currently no pending income tax examinations. To the extent the Company has tax attribute carryforwards, the tax years in which the attribute was generated may still be adjusted upon examination by the Internal Revenue Service and state tax authorities to the extent utilized in a future period.

The entire amount of the unrecognized tax benefits would not impact the Company’s effective tax rate if recognized. The Company's accounting policy is to include interest and penalties as a component of tax expense. During the years ended December 31, 2023 and 2022, the Company did not recognize accrued interest and penalties related to unrecognized tax benefits. The Company does not anticipate that the amount of existing unrecognized tax benefits will significantly increase or decrease during the next 12 months.

A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in thousands):


	Year Ended December 31,
	2023		2022
January 1	$	5,196	$	3,505
Additions based on tax positions related to current year	2,475		1,547
Additions for tax positions of prior year	303		144
December 31	$	7,974	$	5,196

Effective January 1, 2022, we are subject to mandatory capitalization of Section 174 research and development expenditures. The capitalized expenses are subject to amortization over five and fifteen years for expenses incurred within the U.S. and outside of U.S., respectively.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480990/946-20-50-13

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
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-Name Accounting Standards Codification
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-Paragraph 1
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-Name Accounting Standards Codification
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-URI https://asc.fasb.org//740/tableOfContent

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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-Topic 740
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-Name Accounting Standards Codification
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Reference 10: http://www.xbrl.org/2003/role/disclosureRef
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-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482603/740-30-50-2

+ Details

Novartis Collaboration and License Agreement (the "Novartis Agreement")	12 Months Ended
	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Novartis Collaboration and License Agreement (the "Novartis Agreement")	Novartis Collaboration and License Agreement (the "Novartis Agreement") In 2019, we entered into the Novartis Agreement with Novartis Institutes for BioMedical Research, Inc. (“Novartis”) for the development and commercialization of our preclinical product candidate, PLN-1474, and up to three additional integrin research targets. We assessed the Novartis Agreement in accordance with ASC 606 and determined that Novartis was a customer and identified the following performance obligations: (1) to provide worldwide license rights to PLN-1474, (2) to provide research and development services for PLN-1474, (3) to provide non-exclusive license rights to integrin research targets, and (4) to provide research and development services on integrin research targets. On February 17, 2023, Novartis exercised their right to terminate the Novartis Agreement as part of their new strategy focusing on a limited number of therapeutic areas. The termination took effect on April 18, 2023, and effective upon the termination, all rights and licenses granted to Novartis under the Novartis Agreement, including PLN-1474, the related investigational new drug (“IND”), and the validated research target, reverted back to us. The payment obligations of Novartis with respect to future milestones, royalties and research and development funding were also terminated. Revenues associated with the Novartis Agreement for the years ended December 31, 2023, 2022 and 2021, were $1.6 million, $9.7 million and $7.6 million, respectively, which consisted of revenue generated from research and development services and a $4.0 million contingent payment received in 2022 associated with the integrin research target program. As of December 31, 2023 and 2022, there was a receivable of nil and $2.0 million, respectively, related to the Novartis Agreement. There were no contract assets or contract liabilities as of December 31, 2023 and 2022.

Audit Information	12 Months Ended
Audit Information	Dec. 31, 2023
Auditor Information [Abstract]
Auditor Firm ID	34
Auditor Name	Deloitte & Touche LLP
Auditor Location	San Francisco, California

Income Taxes - Summary of Changes in Valuation Allowance for Deferred Tax Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Deferred Tax Assets, Valuation Allowance [Roll Forward]
Valuation allowance at the beginning of the year	$ 105,684	$ 67,684
Increases recorded to income tax provision	48,257	38,000
Valuation allowance at the end of the year	$ 153,941	$ 105,684

Debt - Summary of Maturities of Long-Term Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Debt Disclosure [Abstract]
2026	$ 5,455
2027	4,545
Thereafter	0
Total	10,000
Less: unamortized debt issuance costs	(106)
Accretion of final payment	160
Total	$ 10,054	$ 9,929

- Definition

Amount, after deduction of unamortized premium (discount) and debt issuance cost, of long-term debt. Excludes lease obligation.

+ References + Details

Stock-Based Compensation - Incentive Stock Options and Nonqualified Stock Options - Narrative (Details) - 2015 Equity and 2020 Incentive Plan - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	4 years
Expiration period from date of grant	10 years
Incentive Stock Options and Nonqualified Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost	$ 46,400
Unrecognized compensation expense, weighted average period	2 years 6 months
Intrinsic value of time-based stock options exercised	$ 11,400	$ 2,000	$ 6,900
Grant date fair value of stock option (USD per share)	$ 27.22	$ 7.82	$ 16,940,000

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

+ Details

Leases - Summary of Operating and Variable Lease Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Leases [Abstract]
Operating lease costs	$ 2,771	$ 2,501	$ 2,300
Other variable costs	766	721	949
Total expense	$ 3,537	$ 3,222	$ 3,249

Property and Equipment, net - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 1,841	$ 1,823	$ 1,535

Prepaid Expenses and Other Current Assets

12 Months Ended

Dec. 31, 2023

Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]

Prepaid Expenses and Other Current Assets

Prepaid expenses and other current assets consisted of the following (in thousands):


	December 31,
	2023		2022
Prepaid research and development	$	3,403	$	3,421
Prepaid insurance	1,131		1,427
Prepaid licenses	2,454		959
Interest receivable	2,997		1,078
Other	1,272		173
Total prepaid expenses and other current assets	$	11,257	$	7,058

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2023

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

Basis of Presentation

Use of Estimates

Revenue Recognition

forecasted revenues, development timelines, reimbursement rates for personnel costs, discount rates and probabilities of technical and regulatory success.

Licenses of Intellectual Property

Milestone Payments

Research and development services

Royalties

Fair Value Measurements

Concentration of Credit Risk and Other Risks and Uncertainties

Segments

Cash and Cash Equivalents

Restricted Cash

Short-Term Investments

Property and Equipment, Net


Laboratory equipment			5 years
Computer equipment and software			3 years
Leasehold improvements			Shorter of remaining lease term or estimated useful life

Leases

Impairment of Long-Lived Assets

Research and Development Expenses

under these arrangements in advance of the performance of the related services are recorded as prepaid expenses and are expensed as services are rendered.

Stock-Based Compensation

The Black-Scholes option-pricing model, used to estimate fair value of stock options with service-based vesting conditions, requires the use of the following assumptions:

•Expected dividend—The Company has never paid dividends on the common stock and has no plans to pay dividends on the common stock. Therefore, the Company used an expected dividend yield of zero.

Income Taxes

measurement of tax benefits requires significant judgment. Judgments concerning the recognition and measurement of a tax benefit might change as new information becomes available.

The Company includes any penalties and interest expense related to income taxes as a component of income tax expense, as necessary.

Comprehensive Loss

Interest and other income(expense)

Interest and other income (expense) includes interest income from our short-term investment portfolio.

Net Loss Per Share

Recently Adopted Accounting Pronouncements

Recently Announced Accounting Pronouncements

Leases - Summary of Weighted-average Remaining Lease Terms and Discount Rates (Details)	Dec. 31, 2023	Dec. 31, 2022
Leases [Abstract]
Weighted-average remaining lease term (in years)	7 months 6 days	2 years 3 months 18 days
Weighted-average discount rate	13.60%	8.20%

Leases

12 Months Ended

Dec. 31, 2023

Leases [Abstract]

Leases

New Lease

On September 28, 2023, the Company entered into a lease agreement for a premise consisting of approximately 100,904 square feet located at Oyster Point Blvd, South San Francisco, California (the "Oyster Point Lease"), which the Company intends to use as laboratory and office space. The lease term of approximately seven years will start upon the Landlord’s substantial completion of tenant improvements, and may be extended for a period of eight years at then prevailing market rates for a comparable property. Future lease payments are approximately $43.7 million and are expected to start in the third quarter of 2024. Additionally, the Company is required to provide a letter of credit to the Landlord in the amount of $1.4 million in connection with the Oyster Point Lease. The Company has not recognized a right-of-use asset ("ROU") or aggregate lease liability as of December 31, 2023 for this lease as the Company did not control the underlying assets at any time during the year ended December 31, 2023.

Existing leases

In conjunction with the Oyster Point Lease, we modified the lease term of our existing lease to end upon the start date of the Oyster Point Lease. As a result of this modification, we reduced our lease liability and our right-of-use asset by $1.8 million as of December 31, 2023. Additionally, we paid a refundable security deposit of approximately $0.4 million at inception of the lease term which has been reclassified from other non-current assets to other current assets in the balance sheet of December 31, 2023.

Operating lease ROU assets and liabilities on our balance sheets represent the present value of our remaining lease payments over the remaining lease terms. We use our incremental borrowing rate to calculate the present value of our lease payments, as the implicit rates in our leases are not readily determinable. Operating lease liabilities are based on the net present value of the remaining lease payments over the remaining lease term. In determining the present value of lease payments, the Company used its incremental borrowing rate based on the information available at the date of adoption of Topic 842 or the date of lease modification.

The undiscounted future non-cancellable lease payments of the Company's operating lease liability as of December 31, 2023 were as follows (in thousands):


Year ending December 31:	Operating Leases
2024	$	1,382
Total undiscounted lease payments	1,382
Less: Present value discount	(64)
Total current operating lease liabilities	1,318
Total non-current operating lease liabilities	$	—

The weighted-average remaining lease terms and discount rates related to the Company's operating leases were as follows:


	As of December 31,
	2023		2022
Weighted-average remaining lease term (in years)	0.6		2.3
Weighted-average discount rate	13.60	%	8.2	%

Variable lease costs comprise primarily of the Company's proportionate share of operating expenses, property taxes, and insurance. Short-term lease expense and variable lease payments recorded in operating expenses were immaterial for the years ended December 31, 2023, 2022 and 2021. Lease expenses for the years ended December 31, 2023, 2022 and 2021 are as follows (in thousands)


	As of December 31,
	2023		2022		2021
Operating lease costs	$	2,771	$	2,501	$	2,300
Other variable costs	766		721		949
Total expense	$	3,537	$	3,222	$	3,249

Financial Instruments - Summary of Remaining Contractual Maturities of Company's Short-term Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	$ 487,907	$ 327,771
Market Value	488,252	325,813
Short-term investments
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	430,666	299,459
Market Value	$ 431,011	$ 297,501
Investment, Type [Extensible Enumeration]	Short-term investments
Mature in 1 year or less \| Short-term investments
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	$ 316,700
Market Value	316,366
Mature in 1 to 2 years \| Short-term investments
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	113,966
Market Value	$ 114,645

- Definition

Indicates type of investment. Includes, but is not limited to, common stock, preferred stock, convertible security, fixed income security, government security, option purchased, warrant, loan participation and assignment, commercial paper, bankers' acceptance, certificates of deposit, short-term security, repurchase agreement, and other investment company.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 210
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480524/946-210-50-6

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 210
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (b)(1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480524/946-210-50-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 320
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.12-12A(Column A)(Footnote 2))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480032/946-320-S99-2

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 320
-Name Accounting Standards Codification
-Section S99
-Paragraph 6
-Subparagraph (SX 210.12-14(Column A)(Footnote 2))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480032/946-320-S99-6

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 320
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-12(Column A)(Footnote 2)(i))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480032/946-320-S99-1

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 320
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-12(Column C)(Footnote 5))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480032/946-320-S99-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 320
-Name Accounting Standards Codification
-Section S99
-Paragraph 3
-Subparagraph (SX 210.12-12B(Column A)(Footnote 1)(a))
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-URI https://asc.fasb.org//1943274/2147480032/946-320-S99-3

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 320
-Name Accounting Standards Codification
-Section S99
-Paragraph 3
-Subparagraph (SX 210.12-12B(Column C)(Footnote 2))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480032/946-320-S99-3

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 320
-Name Accounting Standards Codification
-Section S99
-Paragraph 6
-Subparagraph (SX 210.12-14(Column F)(Footnote 7))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480032/946-320-S99-6

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 320
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.12-12A(Column C)(Footnote 4))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480032/946-320-S99-2

+ Details

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-2

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
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-Section 50
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
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-Paragraph 2
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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Reference 10: http://www.xbrl.org/2003/role/disclosureRef
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Reference 11: http://www.xbrl.org/2003/role/disclosureRef
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Reference 12: http://www.xbrl.org/2003/role/disclosureRef
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-Section 50
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-3

+ Details

Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid research and development	$ 3,403	$ 3,421
Prepaid insurance	1,131	1,427
Prepaid licenses	2,454	959
Interest receivable	2,997	1,078
Other	1,272	173
Total prepaid expenses and other current assets	$ 11,257	$ 7,058

Income Taxes - Summary of Reconciliation of Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
January 1	$ 5,196	$ 3,505
Additions based on tax positions related to current year	2,475	1,547
Additions for tax positions of prior year	303	144
December 31	$ 7,974	$ 5,196

Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
Statements of Cash Flows - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Cash flows from operating activities
Net loss	$ (161,336)	$ (123,321)	$ (97,263)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation expense	1,841	1,823	1,535
Stock-based compensation expense	44,483	22,598	10,437
Non-cash operating lease expense	2,390	1,858	1,669
(Accretion) amortization on short-term investments and debt	(4,990)	(1,806)	1,262
Changes in operating assets and liabilities:
Accounts receivable	1,983	15	7,281
Prepaid expenses and other current assets	(3,735)	(294)	(2,266)
Other non-current assets	0	201	70
Accounts payable	2,969	(1,351)	891
Accrued liabilities	2,781	7,904	2,695
Operating lease liabilities	(2,747)	(2,258)	(1,754)
Net cash used in operating activities	(116,361)	(94,631)	(75,443)
Cash flows from investing activities
Purchase of short-term investments	(583,069)	(325,716)	(219,887)
Maturity of short-term investments	456,978	177,272	295,539
Purchase of property and equipment	(921)	(1,760)	(1,953)
Net cash (used in) provided by investing activities	(127,012)	(150,204)	73,699
Cash flows from financing activities
Proceeds from sale of common stock in a public offering	270,251	216,201	0
Proceeds from issuances of common stock under benefit plans	5,001	1,360	2,984
Payment of offering costs	(847)	(557)	(457)
Payment of debt issuance costs	0	(150)	0
Proceeds from term loan	0	10,000	0
Net cash provided by financing activities	274,405	226,854	2,527
Net increase (decrease) in cash and cash equivalents	31,032	(17,981)	783
Cash and cash equivalents at beginning of period	64,716	33,684	51,665
Cash, cash equivalents and restricted cash at end of period	33,684	51,665	50,882
Supplemental disclosures of cash flow information:
Cash paid for interest	1,149	615	0
Reconciliation of cash, cash equivalents, and restricted cash reported in the balance sheets
Cash and cash equivalents	63,234	33,684	51,665
Restricted cash	1,482	0	0
Total cash, cash equivalents, and restricted cash shown in the statements of cash flows	64,716	33,684	51,665
Supplemental disclosures of noncash investing and financing activities:
Net unrealized gain(loss) on short-term investments	2,303	(1,757)	(169)
Purchase of property and equipment in accounts payable	0	0	57
Reclassification of restricted stock awards from liabilities to common stock upon vesting	0	2	9
Supplemental disclosures of cash flow information related to leases:
Cash paid for operating lease liabilities in operating cash flows	3,846	2,657	2,400
Right-of-use assets obtained in exchange for new operating lease liabilities	0	950	0
Decrease in right-of -use assets and liabilities from lease modifications	$ 1,821	$ 0	$ 0

Prepaid Expenses and Other Current Assets (Tables)

12 Months Ended

Dec. 31, 2023

Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]

Summary of Prepaid Expenses and Other Current Assets

Prepaid expenses and other current assets consisted of the following (in thousands):


	December 31,
	2023		2022
Prepaid research and development	$	3,403	$	3,421
Prepaid insurance	1,131		1,427
Prepaid licenses	2,454		959
Interest receivable	2,997		1,078
Other	1,272		173
Total prepaid expenses and other current assets	$	11,257	$	7,058

Stock-Based Compensation - Restricted Stock Units and Performance-Based Restricted Stock Units - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	5 Months Ended	12 Months Ended
	Jul. 31, 2022	Jul. 31, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based payment arrangement, expense			$ 44,483	$ 22,598	$ 10,437
Performance-based restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	2 years
Remaining PSU vested (in shares)		531,792		177,266
Share-based payment arrangement, expense		$ 7,300	12,021	$ 7,390	$ 0
Unrecognized compensation cost			$ 2,600
Unrecognized compensation expense, weighted average period			6 months 14 days
Weighted-Average Grant Date fair value, Vested (USD per share)				$ 17.57
Performance-based restricted stock units \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rights, percentage	0.00%
Performance-based restricted stock units \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rights, percentage	200.00%

Stock-Based Compensation - Summary of Option Activity Under the 2015 Plan and 2020 Plan (Details) - 2015 Equity and 2020 Incentive Plan - Incentive Stock Options and Nonqualified Stock Options - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding [Roll Forward]
Outstanding, beginning balance (in shares)	5,569,567
Granted (in shares)	2,158,764
Exercised (in shares)	(534,706)
Forfeited (in shares)	(240,138)
Outstanding, ending balance (in shares)	6,953,487	5,569,567
Number of options, exercisable (in shares)	3,515,801
Number of options, vested and expected to vest (in shares)	6,953,487
Weighted- Average Exercise Price per Share
Outstanding, beginning balance (USD per share)	$ 13.34
Granted (USD per share)	27.22
Exercised (USD per share)	6.91
Forfeited (USD per share)	18.81
Outstanding, ending balance (USD per share)	17.95	$ 13.34
Weighted- average exercise price per share, exercisable (USD per share)	15.03
Weighted- average exercise price per share, vested and expected to vest (USD per share)	$ 17.95
Weighted- average remaining contractual term (in years), outstanding	7 years 8 months 12 days	7 years 11 months 15 days
Weighted- average remaining contractual term (in years), exercisable	6 years 8 months 26 days
Weighted- average remaining contractual term (in years), vested and expected to vest	7 years 8 months 12 days
Aggregate intrinsic value, outstanding balance	$ 32,646	$ 43,696
Aggregate intrinsic value, exercisable	23,184
Aggregate intrinsic value, vested and expected to vest	$ 32,646

Commitments and Contingencies	12 Months Ended
Commitments and Contingencies	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Purchase Commitments The Company has contractual arrangements with research and development organizations and suppliers; however, these contracts are generally cancellable on 30 days’ notice and the obligations under these contracts are largely based on services performed. Legal Proceedings From time to time, the Company may become involved in legal proceedings arising from the ordinary course of business. The Company record a liability for such matters when it is probable that future losses will be incurred and that such losses can be reasonably estimated. Significant judgment by us is required to determine both probability and the estimated amount. Management is currently not aware of any legal matters that could have a material adverse effect on our financial position, results of operations or cash flows. Indemnification In the ordinary course of business, the Company enters into agreements that may include indemnification provisions. Pursuant to such agreements, the Company may indemnify, hold harmless and defend an indemnified party for losses suffered or incurred by the indemnified party. Some of the provisions will limit losses to those arising from third party actions. In some cases, the indemnification will continue after the termination of the agreement. The maximum potential amount of future payments the Company could be required to make under these provisions is not determinable. The Company has never incurred material costs to defend lawsuits or settle claims related to these indemnification provisions. The Company has also entered into indemnification agreements with its directors and officers that may require the Company to indemnify its directors and officers against liabilities that may arise by reason of their status or service as directors or officers to the fullest extent permitted by Delaware corporate law. The Company currently has directors’ and officers’ insurance.

Stock-Based Compensation - Summary of Black-Scholes Option Pricing Model to Estimate Stock-based Compensation Expense for Stock Option Awards (Details) - $ / shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividends	0.00%
Incentive Stock Options and Nonqualified Stock Options \| 2015 Equity and 2020 Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility, minimum	80.97%	73.78%	74.83%
Expected volatility, maximum	83.28%	80.64%	76.31%
Risk-free interest rate, minimum	3.42%	1.64%	0.61%
Risk-free interest rate, maximum	4.68%	4.16%	1.39%
Incentive Stock Options and Nonqualified Stock Options \| Minimum \| 2015 Equity and 2020 Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividends	0.00%	0.00%	0.00%
Expected term (in years)	5 years 3 months 21 days	5 years 3 months 29 days	5 years 5 months 8 days
Underlying common stock fair value (USD per share)	$ 15.25	$ 4.92	$ 15.20
Incentive Stock Options and Nonqualified Stock Options \| Maximum \| 2015 Equity and 2020 Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividends	0.00%	0.00%	0.00%
Expected term (in years)	6 years 29 days	6 years 29 days	6 years 29 days
Underlying common stock fair value (USD per share)	$ 34.65	$ 24.23	$ 38.23

Net Loss Per Share Attributable to Common Stockholders (Tables)

12 Months Ended

Dec. 31, 2023

Earnings Per Share [Abstract]

Summary of Potentially Dilutive Securities Excluded from Computation of Diluted Net Loss Per Share


	Year Ended December 31,
	2023	2022	2021
Options to purchase common stock	6,953,487	5,569,567	3,620,180
Restricted stock units	874,748	507,925	—
Performance-based restricted stock units*	328,750	354,532	—
Unvested restricted shares	—	—	21,841
Total	8,156,985	6,432,024	3,642,021
*PSUs outstanding based on target level of achievement of 100%.

Stock-Based Compensation - Summary of TSR PSU Valuation Assumptions (Details) - Performance-Based Restricted Stock Units, TSR Goal	12 Months Ended
	Dec. 31, 2023 $ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Valuation date share price (USD per share)	$ 17.57
Expected term (in years)	1 year 11 months 1 day
Volatility	70.62%
Correlation coefficient	0.3508
Average peer group volatility	79.69%
Average peer group correlation coefficient	0.4397
Risk free interest rate	2.84%

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

+ Details

Income Taxes -Narrative (Details)	12 Months Ended
Income Taxes -Narrative (Details)	Dec. 31, 2023 USD ($) taxExamination	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Income Tax Disclosure [Abstract]
Pre-tax U.S. book loss	$ (161,336,000)	$ (123,300,000)	$ (97,300,000)
Income tax provision	$ 0	0	$ 0
Valuation allowance as a percentage on total deferred tax assets	100.00%
Number of income tax examinations pending \| taxExamination	0
Unrecognized tax benefits, income tax penalties and interest expense	$ 0	$ 0

- Definition

Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References + Details

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2023

Income Tax Disclosure [Abstract]

Summary of Reconciliation of U.S. Federal Statutory Income Tax Rate to Company’s Effective Income Tax Rate

A reconciliation of the U.S. federal statutory income tax rate to the Company’s effective income tax rate is as follows:


	Year Ended December 31,
	2023		2022		2021
Income tax computed at federal statutory rate	21.0	%	21.0	%	21.0	%
State taxes, net of federal tax benefit	6.7	%	7.3	%	7.7	%
General business credit—federal	5.3	%	3.6	%	5.3	%
Stock-based compensation	0.9	%	(1.0)	%	(0.7)	%
Other permanent differences	0.1	%	(0.4)	%	(0.1)	%
Section 162(m)	(3.8)	%	—	%	—	%
Change in valuation allowance	(30.2)	%	(30.5)	%	(33.2)	%
Effective income tax rate	—	%	—	%	—	%

Summary of Deferred Tax Assets and Liabilities

Net deferred tax assets and liabilities consisted of the following (in thousands):


	December 31,
	2023		2022
Deferred tax assets:
Net operating losses	$	78,452	$	65,689
Research and development credits	29,559		19,688
Accrued expenses	2,211		387
Other	1,350		1,706
Capitalized research and development	34,769		13,900
Lease liability	369		1,638
Stock based compensation	8,291		5,073
Total deferred tax assets	155,001		108,081
Deferred tax liabilities:
Fixed asset basis	(123)		(258)
Prepaid expenses	(598)		(630)
Right of use asset	(339)		(1,509)
Total deferred tax liabilities	(1,060)		(2,397)
Valuation allowance	153,941		105,684
Net deferred taxes	$	—	$	—

Summary of Net Operating Losses and Tax Credit Carryforwards

Net operating losses and tax credit carryforwards were as follows (in thousands):


	December 31, 2023		Expiration Year
Net operating losses, federal (starting from January 1, 2018)	$	212,005	Does not expire
Net operating losses, federal (before January 1, 2018)	$	29,486	2035-2037
Net operating losses, state	$	397,559	2035-2043
Tax credits, federal	$	31,512	2036-2043
Tax credits, state	$	7,145	Does not expire

Summary of Changes in Valuation Allowance for Deferred Tax Assets

Changes in the valuation allowance for deferred tax assets during the years ended December 31, 2023 and 2022 related primarily to the increases in net operating loss carryforwards and research and development tax credit carryforwards and were as follows (in thousands):


	Year Ended December 31,
	2023		2022
Valuation allowance at the beginning of the year	$	105,684	$	67,684
Increases recorded to income tax provision	48,257		38,000
Valuation allowance at the end of the year	$	153,941	$	105,684

Summary of Reconciliation of Unrecognized Tax Benefits

A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in thousands):


	Year Ended December 31,
	2023		2022
January 1	$	5,196	$	3,505
Additions based on tax positions related to current year	2,475		1,547
Additions for tax positions of prior year	303		144
December 31	$	7,974	$	5,196

Income Taxes - Summary of Net Operating Losses and Tax Credit Carry Forwards (Details) $ in Thousands	Dec. 31, 2023 USD ($)
Federal
Operating Loss Carryforwards [Line Items]
Tax credits	$ 31,512
Federal \| Starting from January 1, 2018
Operating Loss Carryforwards [Line Items]
Net operating losses	212,005
Federal \| Before January 1, 2018
Operating Loss Carryforwards [Line Items]
Net operating losses	29,486
State
Operating Loss Carryforwards [Line Items]
Net operating losses	397,559
Tax credits	$ 7,145

Leases - Summary of Operating Lease Liability (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Operating Leases, After Adoption of 842:
2024	$ 1,382
Total undiscounted lease payments	1,382
Less: Present value discount	(64)
Total current operating lease liabilities	1,318	$ 2,457
Total non-current operating lease liabilities	$ 0	$ 3,429

Common Stock - Narrative (Details)	12 Months Ended
Common Stock - Narrative (Details)	Dec. 31, 2023 research $ / shares shares	Dec. 31, 2022 $ / shares shares
Equity [Abstract]
Common stock, shares authorized (in shares) \| shares	300,000,000	300,000,000
Common stock, par value (USD per share)	$ 0.0001	$ 0.0001
Common stock, voting rights \| research	1
Dividends declared (USD per share)	$ 0
Dividends paid (USD per share)	$ 0

Common Stock (Tables)

12 Months Ended

Dec. 31, 2023

Equity [Abstract]

Summary of Shares Reserved for Future Issuance

Shares reserved for future issuance


	December 31,
	2023	2022
Outstanding stock option awards	6,953,487	5,569,567
Vesting of RSUs	874,748	507,925
Vesting of PSUs*	328,752	531,796
Shares of common stock available for future grants under the 2020 Stock Option and Incentive Plan	2,882,239	2,937,769
Shares of common stock available for future issuance under the 2020 ESPP	805,756	888,184
Shares of common stock available for future issuance under the 2022 Inducement Plan	700,000	1,000,000
Total shares reserved for future issuance	12,544,982	11,435,241
*PSUs granted and outstanding based on target level of achievement of 100%.

Property and Equipment, net - Summary of Property and Equipment Net (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 12,249	$ 11,327
Less: Accumulated depreciation	(8,682)	(6,841)
Total property and equipment, net	3,567	4,486
Laboratory equipment
Property, Plant and Equipment [Line Items]
Total property and equipment	10,410	9,581
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total property and equipment	1,663	1,650
Construction-in-progress
Property, Plant and Equipment [Line Items]
Total property and equipment	52	66
Computer equipment and software
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 124	$ 30