0001746473-22-000010 | 10-K | XBRL Viewer

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Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Current assets
Cash and cash equivalents	$ 51,665	$ 50,882
Short-term investments	148,931	226,012
Accounts receivable	1,998	9,279
Tax credit receivable	83	83
Total prepaid expenses and other current assets	6,764	4,498
Total current assets	209,441	290,754
Property and equipment, net	4,606	4,321
Operating lease right-of-use assets	6,330	0
Other non-current assets	838	451
Total assets	221,215	295,526
Current liabilities
Accounts payable	2,971	2,023
Accrued liabilities	11,991	9,576
Lease liabilities, current	1,869	0
Total current liabilities	16,831	11,599
Lease liabilities, non-current	5,325	0
Other long-term liabilities	0	866
Total liabilities	22,156	12,465
Commitments and contingencies
Stockholders’ equity (deficit)
Common stock, $0.0001 par value; 300,000,000 shares authorized at December 31, 2021 and 2020; and 36,083,301 and 35,552,795 shares issued and outstanding at December 31, 2021 and 2020, respectively;	3	3
Additional paid-in capital	414,348	400,918
Accumulated deficit	(215,091)	(117,828)
Accumulated other comprehensive loss	(201)	(32)
Total stockholders’ equity	199,059	283,061
Total liabilities and stockholders’ equity	$ 221,215	$ 295,526

Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	300,000,000	300,000,000
Common stock, shares issued (in shares)	36,083,301	35,552,795
Common stock, shares outstanding (in shares)	36,083,301	35,552,795

Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Statement [Abstract]
Revenue	$ 7,572	$ 41,817	$ 57,052
Operating expenses:
Research and development	(77,549)	(66,193)	(47,353)
General and administrative	(27,558)	(17,269)	(10,930)
Total operating expenses	(105,107)	(83,462)	(58,283)
Loss from operations	(97,535)	(41,645)	(1,231)
Interest and other income (expense), net	272	112	600
Net loss	(97,263)	(41,533)	(631)
Accretion to redemption value and dividends on redeemable convertible preferred stock	0	0	(6,225)
Net loss attributable to common stockholders	$ (97,263)	$ (41,533)	$ (6,856)
Net loss per share, attributable to common stockholders:
Basic (in dollars per share)	$ (2.71)	$ (1.95)	$ (4.22)
Diluted (in dollars per share)	$ (2.71)	$ (1.95)	$ (4.22)
Shares used in computing net loss per share attributable to common stockholders:
Basic (in shares)	35,846,421	21,344,236	1,623,358
Diluted (in shares)	35,846,421	21,344,236	1,623,358
Comprehensive loss:
Net loss	$ (97,263)	$ (41,533)	$ (631)
Other comprehensive loss:
Net unrealized loss on short-term investments	(169)	(31)	(1)
Total other comprehensive loss	(169)	(31)	(1)
Comprehensive loss	$ (97,432)	$ (41,564)	$ (632)

Statements of Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Initial Public Offering	Private Placement	Common Stock	Common Stock Initial Public Offering	Common Stock Private Placement	Additional Paid-In Capital	Additional Paid-In Capital Initial Public Offering	Additional Paid-In Capital Private Placement	Accumulated Other Comprehensive Loss	Accumulated Deficit	Series A	Series B	Series C
Beginning balance (in shares) at Dec. 31, 2018												56,000,000	49,501,221	0
Beginning balance at Dec. 31, 2018												$ 61,516	$ 70,587	$ 0
Increase (Decrease) in Temporary Equity [Roll Forward]
Issuance of Series C redeemable preferred stock, net of issuance costs (in shares)														26,360,745
Issuance of Series C redeemable preferred stock, net of issuance costs														$ 47,947
Ending balance (in shares) at Dec. 31, 2019												56,000,000	49,501,221	26,360,745
Ending balance at Dec. 31, 2019												$ 62,468	$ 75,860	$ 47,947
Beginning balance (in shares) at Dec. 31, 2018				1,363,000
Beginning balance at Dec. 31, 2018	$ (71,469)			$ 1			$ 0			$ 0	$ (71,470)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Vesting of founders’ common stock and restricted stock awards (in shares)				440,964
Vesting of founders’ common stock and restricted stock awards	28						28
Option exercises (in shares)				42,060
Option exercises	174						174
Accretion to redemption value and cumulative dividends on redeemable convertible stock												$ 952	$ 5,273
Accretion to redemption value and cumulative dividends on redeemable convertible stock	(6,225)						(2,031)				(4,194)
Stock-based compensation expense	1,829						1,829
Net unrealized loss on short-term investments	(1)									(1)
Net loss	(631)										(631)
Ending balance (in shares) at Dec. 31, 2019				1,846,024
Ending balance at Dec. 31, 2019	(76,295)			$ 1			0			(1)	(76,295)
Increase (Decrease) in Temporary Equity [Roll Forward]
Issuance of Series C redeemable preferred stock, net of issuance costs (in shares)														28,527,313
Issuance of Series C redeemable preferred stock, net of issuance costs														$ 52,019
Conversion of Series A, B, C convertible preferred stock to common stock (in shares)												(56,000,000)	(49,501,221)	(54,888,058)
Conversion of Series A, B, C convertible preferred stock to common stock												$ (62,468)	$ (75,860)	$ (99,966)
Ending balance (in shares) at Dec. 31, 2020												0	0	0
Ending balance at Dec. 31, 2020												$ 0	$ 0	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon initial public offering/private placement (in shares)					10,350,000	625,000
Issuance of common stock upon initial public offering/private placement		$ 148,278	$ 10,000		$ 1			$ 148,277	$ 10,000
Conversion of Series A, B, C convertible preferred stock to common stock (in shares)				22,432,029
Conversion of Series A, B, C convertible preferred stock to common stock	238,294			$ 1			238,293				0
Vesting of founders’ common stock and restricted stock awards (in shares)				163,544
Vesting of founders’ common stock and restricted stock awards	11						11
Option exercises (in shares)				136,198
Option exercises	442						442
Stock-based compensation expense	3,895						3,895
Net unrealized loss on short-term investments	(31)									(31)
Net loss	$ (41,533)										(41,533)
Ending balance (in shares) at Dec. 31, 2020	35,552,795			35,552,795
Ending balance at Dec. 31, 2020	$ 283,061			$ 3			400,918			(32)	(117,828)
Ending balance (in shares) at Dec. 31, 2021												0	0	0
Ending balance at Dec. 31, 2021												$ 0	$ 0	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Vesting of restricted stock awards (in shares)				103,164
Vesting of restricted stock awards	9						9
Option exercises (in shares)				427,342
Option exercises	2,984						2,984
Stock-based compensation expense	10,437						10,437
Net unrealized loss on short-term investments	(169)									(169)
Net loss	$ (97,263)										(97,263)
Ending balance (in shares) at Dec. 31, 2021	36,083,301			36,083,301
Ending balance at Dec. 31, 2021	$ 199,059			$ 3			$ 414,348			$ (201)	$ (215,091)

Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
Statements of Cash Flows - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities:
Net loss	$ (97,263)	$ (41,533)	$ (631)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation expense	1,535	1,310	1,113
Stock-based compensation expense	10,437	3,895	1,829
Noncash lease expense	1,669	0	0
Other	1,262	266	0
Changes in operating assets and liabilities:
Tax credit receivable	0	250	167
Accounts receivable	7,281	(2,227)	(7,052)
Prepaid expenses and other current assets	(2,266)	(2,756)	(1,458)
Other non-current assets	70	(70)	232
Accounts payable	891	922	(1,255)
Accrued liabilities	2,695	2,689	4,255
Operating lease liabilities	(1,754)	0	0
Deferred rent and other long-term liabilities	0	(17)	50
Net cash used in operating activities	(75,443)	(37,271)	(2,750)
Cash flows from investing activities:
Purchase of short-term investments	(219,887)	(322,605)	(51,713)
Accretion on short-term investments	0	0	(254)
Maturity of short-term investments	295,539	113,271	35,000
Purchase of property and equipment	(1,953)	(1,532)	(964)
Net cash used in investing activities	73,699	(210,866)	(17,931)
Cash flows from financing activities:
Proceeds from issuance of common stock upon initial public offering, net of issuance costs	0	150,751	0
Proceeds from issuance of common stock upon completion of private placement	0	10,000	0
Proceeds from issuance of Series C preferred stock, net of issuance costs	0	52,019	47,947
Proceeds from issuances of common stock	2,984	442	174
Payment of deferred offering costs	(457)	0	(2,582)
Net cash provided by financing activities	2,527	213,212	45,539
Net increase (decrease) in cash and cash equivalents	783	(34,925)	24,858
Cash and cash equivalents at beginning of period	50,882	85,807	60,949
Cash and cash equivalents at end of period	51,665	50,882	85,807
Supplemental disclosures of noncash investing and financing activities:
Purchase of property and equipment in accounts payable and accrued liabilities	57	188	159
Reclassification of restricted stock awards from liabilities to common stock upon vesting	9	11	30
Accretion to redemption value and dividends on redeemable convertible preferred stock	0	0	6,225
Deferred offering costs in accounts payable and accrued liabilities	0	0	230
Net unrealized loss on short-term investments	$ (169)	$ (31)	$ (1)

Organization and Description of Business	12 Months Ended
Organization and Description of Business	Dec. 31, 2021
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 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. Reverse Stock Split On May 22, 2020, the Company implemented a 1-for-7.15 reverse stock split of the Company’s common stock. Stockholders entitled to fractional shares as a result of the reverse stock split received a cash payment in lieu of receiving fractional shares. All share and per share data shown in the accompanying financial statements and related notes have been retroactively revised to reflect the reverse stock split. Shares of common stock underlying outstanding stock options and other equity instruments were proportionately reduced and the respective exercise prices, if applicable, were proportionately increased in accordance with the terms of the agreements governing such securities. Shares of common stock reserved for issuance upon the conversion of the Company’s convertible preferred stock were proportionately reduced and the respective conversion prices were proportionately increased. As of June 3, 2020, all outstanding preferred stock had been converted into common stock. Initial Public Offering In June 2020, the Company completed its initial public offering (the “IPO”), in which the Company issued and sold an aggregate of 10,350,000 shares of common stock, which consisted of 9,000,000 shares of common stock and 1,350,000 shares of common stock sold pursuant to the underwriters’ exercise of their option to purchase additional shares, at a public offering price of $16.00 per share. The aggregate net proceeds received by the Company from the offering were $148.3 million, net of underwriting discounts, commissions and offering expenses of $5.7 million. Upon the closing of the IPO, 160,389,279 shares of the Company’s outstanding convertible preferred stock were automatically converted to common stock on a 7.15:1 basis and the related carrying amount of $238.3 million was reclassified to common stock and additional paid-in capital within stockholders’ equity (deficit). Concurrent with the completion of the IPO, the Company also issued 625,000 shares of its common stock to Novartis Institutes for Biomedical Research, Inc. (“Novartis”), a strategic partner and existing stockholder of the Company, in a private placement at a price of $16.00 per share for proceeds of $10.0 million, which resulted in Novartis owning approximately 6.1% of the Company’s outstanding shares of common stock immediately after the IPO.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2021

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

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 and liabilities, 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, short-term investments, 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.

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, treasury bill and notes, 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, 2021, 2020 and 2019, 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. All long-lived assets are maintained in the United States of America.

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.

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, 2021 and 2020, 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 loss in the statements of operations and comprehensive loss. See Note 3 for further details.

Short-term investments are considered impaired when a decline in fair value is judged to be other-than-temporary. The Company consults with its investment managers and considers available quantitative and qualitative evidence in evaluating potential impairment of its short-term investments on a quarterly basis. If the cost of an individual investment exceeds its fair value, the Company evaluates, among other factors, general market conditions, the duration and extent to which the fair value is less than cost and its intent and ability to hold the investment. Once a decline in fair value is determined to be other-than-temporary, an impairment charge will be recorded to other expense, net, in the statements of operations and comprehensive loss and a new cost basis in the short-term investment will be established. As of December 31, 2021, the Company had not recorded any impairment related to other-than-temporary declines in the fair value of short-term investments.

The Company adopted Accounting Standards Update (“ASU”) 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (“ASU 2016-13”) as of January 1, 2021, which did not have a significant impact on its financial statements. For available-for-sale debt securities in unrealized loss positions, ASU 2016-13 requires the Company to record an allowance for credit losses using an expected loss model, which replaces the incurred loss model required under the previous guidance. A credit loss is 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.

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

Upon adoption of Accounting Standards Codification (“ASC”) Topic 842, Leases (“ASC 842”), 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, 2021, 2020 and 2019.

Redeemable Convertible Preferred Stock

All preferred stock was automatically converted into common stock upon the Company’s IPO in June 2020. Prior to this conversion, the Company classified redeemable convertible preferred stock outside of stockholders’ equity (deficit) because, upon the occurrence of certain change in control events that were outside the Company’s control, including liquidation, sale or transfer of the Company’s assets, holders of the redeemable convertible preferred stock could have caused redemption for cash. At any time on or after December 19, 2024, the holders of a majority of the outstanding redeemable convertible preferred stock could also have required the Company to redeem the redeemable convertible preferred stock by providing the Company a written notice requesting such redemption. The Company recognized changes in the redemption value immediately as they occurred, for example changes in fair value of preferred stock, and adjustments in the carrying amount of the redeemable convertible preferred stock to equal the redemption value at the end of each reporting period up through December 19, 2019, when the Company entered into the Series C Preferred Stock Purchase Agreement. See Note 9 for further details. In the absence of retained earnings these accretion charges were recorded against additional paid in capital, if any, and then to accumulated deficit. The Company analyzed all embedded derivatives and beneficial conversion features for its redeemable convertible preferred stock and concluded that none required bifurcation.

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 and shares that will be 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 Black-Scholes option-pricing model, used to estimate fair value of stock-based awards, 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.

Prior to our IPO, the fair value of our common stock has been determined using independent third-party valuations based on relevant valuation methodologies as outlined in the American Institute of Certified Public Accountants (AICPA) Practice Aid, “Valuation of Privately-Held-Company Equity Securities Issued as Compensation”. The Company also considered the amount of time between the independent third-party valuation dates and the grant dates and used interpolation of the fair value between the two valuation dates to estimate common stock fair value at each grant date. This determination included an evaluation of whether the subsequent valuation indicated that any significant change in valuation had occurred between the previous valuation and the grant date. Following our IPO, the Company uses our stock price traded on NASDAQ to determine its fair value.

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 (deficit) that result from transactions and economic events other than those with stockholders. The Company's comprehensive loss represents unrealized losses on short-term investments.

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.

Prior to the conversion of our preferred stock in our IPO, net loss or income per share attributable to common stockholders was calculated using the two-class method, which is based on an earnings allocation formula that determines net loss or income per share for the Company’s common stockholders and holders of participating securities. The holders of preferred stock were entitled to receive dividends prior and in preference to any declaration or payment of any dividend on the common stock. Under this method, net loss or income is increased or reduced by the amount of any dividends earned and accretion of redeemable convertible preferred stock to its redemption value, if any, during the period. The undistributed earnings are allocated to common stock and each series of redeemable convertible preferred stock to the extent that each preferred security may share in the earnings as if all of the earnings for the period had been distributed. Net loss or income attributable to common stockholders and participating preferred shares are allocated to each share on an as-converted basis as if all the earnings for the period had been distributed. The participating securities do not include a contractual obligation to share in losses of the Company and are not included in the calculation of net loss per share in the periods in which a net loss is recorded. Diluted net loss or income per share is computed using the more dilutive of (a) the two-class method or (b) the as-converted method. The Company allocated earnings first to redeemable convertible preferred shares stockholders based on dividend rights and then to common and preferred stockholders based on ownership interests. The weighted-average number of shares of common stock included in the computation of diluted net loss or income gives effect to all potentially dilutive common equivalent shares, including outstanding stock options and preferred 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, 2021, 2020 and 2019.

Recently Adopted Accounting Pronouncements

In February 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standard Update (“ASU”) No. 2016-2, Leases (“Topic 842”), which requires an entity to recognize assets and liabilities arising from a lease for both financing and operating leases. Subsequent to this, the FASB issued various amendments to ASC 842, which affected certain aspects of the previously issued guidance. One of the amendments included an additional transition option that allowed entities to apply the new standard on the adoption date and recognize a cumulative effect adjustment to the opening balance of retained earnings. These updates were effective for public companies for annual periods beginning after December 15, 2018, including interim periods therein. Because the Company lost its EGC status on December 31, 2021, the standard became effective for the Company for its annual period beginning January 1, 2021. Amounts prior to January 1, 2021 were not adjusted and continue to be reported in accordance with previous lease guidance, ASC Topic 840, Leases.

The Company adopted ASC 842 and all related amendments effective January 1, 2021 using the modified retrospective transition approach. The Company elected the package of practical expedients upon adoption, which permitted the Company to not reassess under the new standard the Company's prior conclusions about lease identification, lease classification and initial direct costs. In addition, the Company elected the short-term lease exception policy, permitting it to exclude the recognition requirements of this standard from leases with initial terms of 12 months or less.

The adoption of ASC 842 effective January 1, 2021 resulted in the recognition of operating lease ROU assets of $8.0 million and operating lease liabilities of $8.9 million in the Company’s balance sheet. In connection with the adoption, pre-existing liabilities for deferred rent and lease incentives totaling $0.9 million were reclassified as an offset to the operating lease ROU assets. The Company’s financial position and operating results for reporting periods prior to January 1, 2021 have not been adjusted and continue to be presented in accordance with the accounting standard in effect at that time. The adoption of ASC 842 did not have a material impact on the 2021 quarterly or annual results of operations or cash flows and had no impact on retained earnings.

In 2016, the FASB issued ASU 2016-13, which requires entities to record expected credit losses for certain financial instruments, including trade receivables, as an allowance that reflects the entity's current estimate of credit losses expected to be incurred. For available-for-sale debt securities in unrealized loss positions, ASU 2016-13 requires

allowances to be recorded instead of reducing the amortized cost of the investment. ASU 2016-13 became effective on January 1, 2021. The adoption of ASU 2016-13 did not have an impact on the Company’s financial statements.

Financial Instruments

12 Months Ended

Dec. 31, 2021

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 losses or income recognized in other comprehensive 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. The accounting guidance for fair value provides a framework for measuring fair value and requires certain disclosures about how fair value is determined. 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. The accounting guidance also 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 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 and include U.S. government agency securities, U.S. Treasury securities and corporate debt securities. 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 Level 3 assets or liabilities as of December 31, 2021 and 2020.

The following tables show the Company’s cash and cash equivalents, Money Market Funds and short-term investments by significant investment category as of December 31, 2021 and 2020 (in thousands):


	As of December 31, 2021
	Adjusted Cost		Unrealized Gains		Unrealized Losses		Market Value
Level 1:
Money Market Funds	$	15,329	$	—	$	—	$	15,329
Level 2:
U.S. government agency securities included in short-term investments	5,003		—		—		5,003
Corporate debt securities included in cash and cash equivalents and short-term investments	163,626		1		(202)		163,425
Total financial assets	$	183,958	$	1	$	(202)	$	183,757


	As of December 31, 2020
	Adjusted Cost		Unrealized Gains		Unrealized Losses		Market Value
Level 1:
Money Market Funds	$	27,686	$	—	$	—	$	27,686
Level 2:
U.S. Treasury securities included in short-term investments	63,101		4		(1)		63,104
U.S. government agency securities included in short-term investments	54,183		10		—		54,193
Corporate debt securities included in cash and cash equivalents and short-term investments	118,759		1		(46)		118,714
Total financial assets	$	263,729	$	15	$	(47)	$	263,697

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, 2021:


	Adjusted Cost		Market Value
Mature in 1 year or less	$	114,076	$	113,974
Mature in 1 to 2 years	35,054		34,956
Total	$	149,130	$	148,930

There were no liabilities measured at fair value on a recurring basis as of December 31, 2021 and 2020. There have been no transfers between fair value measurement levels during the years ended December 31, 2021 and 2020. In addition, there were no assets or liabilities measured at fair value on a non-recurring basis as of December 31, 2021 and 2020.

As of December 31, 2021, the Company had not recorded any impairment related to other-than-temporary declines in the fair value of short-term investments.

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 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

Property and Equipment, net

12 Months Ended

Dec. 31, 2021

Property, Plant and Equipment [Abstract]

Property and Equipment, net

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


	December 31,
	2021		2020
Laboratory equipment	$	7,947	$	6,540
Leasehold improvements	1,618		947
Construction-in-progress	38		300
Computer equipment and software	22		22
Total property and equipment	9,625		7,809
Less: Accumulated depreciation	(5,019)		(3,488)
Total property and equipment, net	$	4,606	$	4,321

Depreciation expense during the years ended December 31, 2021, 2020 and 2019 was $1.5 million, $1.3 million, $1.1 million, respectively.

Prepaid expenses and other current assets

12 Months Ended

Dec. 31, 2021

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,
	2021		2020
Prepaid research and development	$	2,819	$	1,898
Prepaid insurance	2,585		1,459
Prepaid licenses	819		665
Interest receivable	385		386
Other	156		90
Total prepaid expenses and other current assets	$	6,764	$	4,498

Accrued Liabilities and Other Long-Term Liabilities

12 Months Ended

Dec. 31, 2021

Accrued Liabilities and Other Liabilities [Abstract]

Accrued Liabilities and Other Long-Term Liabilities

Accrued Liabilities

Accrued liabilities consisted of the following (in thousands):


	December 31,
	2021		2020
Accrued research and development expenses	$	5,868	$	3,274
Accrued compensation and benefits	5,216		4,542
Other accrued liabilities	907		1,675
Deferred rent	—		85
Total accrued liabilities	$	11,991	$	9,576

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

Other Long-Term Liabilities

Other long-term liabilities consisted of the following (in thousands):


	December 31,
	2021		2020
Deferred rent	$	—	$	581
Leasehold incentive obligation	—		283
Other liabilities — deposits	—		2
Total other long-term liabilities	$	—	$	866

Novartis Collaboration and License Agreement (the "Novartis Agreement")	12 Months Ended
	Dec. 31, 2021
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, for the development and commercialization of our preclinical product candidate, PLN-1474 and up to three additional integrin research targets. PLN-1474 is an internally discovered small molecule selective inhibitor of integrin αvβ1, currently being developed for the treatment of liver fibrosis associated with nonalcoholic steatohepatitis (“NASH”). Pursuant to the agreement, we received an upfront, non-refundable license fee of $50.0 million and were eligible to receive additional payments of $416.0 million contingent upon achievement of specified research, development, regulatory and commercial events and royalties on world-wide net sales thereafter. Additionally, Novartis agreed to fund up to $19.6 million associated with research and development services for PLN-1474 and up to $13.4 million for research and development services on the integrin research targets. We assessed the Novartis Agreement in accordance with ASC 606 and determined that Novartis is 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. We determined that the license to PLN-1474 was functional intellectual property and distinct as Novartis is capable to benefit from the license on its own or together with other resources that are readily available, and the research and development services we promise to deliver are not transformative in nature. Additionally, we concluded that the non-exclusive license rights to integrin research targets were not distinct in the context of the arrangement as the promised research and development services on integrin research targets were expected to significantly modify the license and Novartis could not benefit from the non-exclusive license without such services. Therefore, the non-exclusive license rights and research and development services on integrin research targets were considered a single performance obligation. We determined the transaction price of the PLN-1474 research and development services and integrin target research and development services was $20.0 million and $13.4 million, respectively, as of December 31, 2021, and the performance obligations associated with the aggregate unrecognized transaction price of $2.0 million would be satisfied in 2022. As of December 31, 2021, variable consideration associated with specified research and development milestones totaling $391 million have been constrained from the transaction prices but remain eligible for achievement. We are utilizing a cost-based input method to measure proportional performance and to calculate the corresponding amount of revenue to recognize. We believe this is the best measure of progress because other measures do not reflect how we transfer the performance obligation to our counterparty. In applying the cost-based input method of revenue recognition, we use actual costs incurred relative to budgeted costs to fulfill the performance obligation. These costs consist primarily of third-party contract costs and internal full-time equivalent effort. A cost-based input method of revenue recognition requires management to make estimates of costs to complete the performance obligations. The cumulative effect of revisions to estimated costs to complete the performance obligations will be recorded in the period in which changes are identified and amounts can be reasonably estimated. A significant change in these assumptions and estimates could have a material impact on the timing and amount of revenue recognized in future periods. During the year ended December 31, 2021, we recognized revenue of $7.6 million which consisted of revenue generated from research and development services. During the year ended December 31, 2020, we recognized revenue of $41.8 million, which consisted of $25.0 million from the achievement of the first patient dosing milestone of the Novartis agreement in the first quarter of 2020 and $16.8 million of revenue generated from research and development services performed during the year. During the year ended December 31, 2019, Company recognized revenue of $50.0 million related to the license fee and $7.1 million from research and development services. As of December 31, 2021 and 2020, there was a receivable of $2.0 million and $9.3 million, respectively, related to the Novartis Agreement. There were no contract assets or contract liabilities as of December 31, 2021 and 2020.

Regents of the University of California License Agreement (the “UC Agreement”)	12 Months Ended
	Dec. 31, 2021
License Agreements [Abstract]
Regents of the University of California License Agreement (the “UC Agreement”)	Regents of the University of California License Agreement (the “UC Agreement”) In 2015, we entered into the UC Agreement to obtain an exclusive, worldwide license relating to the use of certain patents and technology relating to αvß1 compound in fibrosis indications. Pursuant to the UC Agreement, we made a $2.4 million milestone payment upon the close of our IPO in June 2020. Subsequently, we determined the licensed technology was no longer relevant to the development of our product candidates and, therefore, we exercised our right to terminate the UC Agreement which became effective in the first quarter of 2021. No further obligations or financial commitments survive the termination.

Adimab Development and Option Agreement (the "Adimab Agreement")	12 Months Ended
	Dec. 31, 2021
Research and Development [Abstract]
Adimab Development and Option Agreement (the "Adimab Agreement")	Adimab Development and Option Agreement (the "Adimab Agreement")In 2018, we entered into a development and option agreement with Adimab, LLC (“Adimab”) for the discovery and optimization of proprietary antibodies as potential therapeutic product candidates. Under the Adimab Agreement, we will select biological targets against which Adimab will use its proprietary platform technology to research and develop antibody proteins using a mutually agreed upon research plan. We are required to pay Adimab an agreed upon rate for its full-time employees during the discovery period while Adimab performs research on each target under the applicable research plan. We have an exclusive option to obtain a worldwide, royalty-bearing, sublicensable license under Adimab platform patents and other Adimab technology to research, develop and commercialize up to 24 antibodies of our selection.During the years ended December 31, 2021, 2020 and 2019, we recognized research and development expenses associated with full-time employee costs of $28,000, $0.2 million and $0.2 million, respectively.

Redeemable Convertible Preferred Stock	12 Months Ended
Redeemable Convertible Preferred Stock	Dec. 31, 2021
Temporary Equity Disclosure [Abstract]
Redeemable Convertible Preferred Stock	Redeemable Convertible Preferred StockUnder the Company’s Amended and Restated Certificate of Incorporation (“Certificate of Incorporation”), the Company is authorized to issue two classes of shares: preferred 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 a result of the IPO in June 2020, all then outstanding convertible preferred stock was converted into shares of common stock. There are no outstanding shares of preferred stock as of December 31, 2021.

Common Stock

12 Months Ended

Dec. 31, 2021

Equity [Abstract]

Common Stock

As of December 31, 2021 and 2020, 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

After payment of the respective liquidation preferences to the holders of shares of Preferred Stock, 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,
	2021	2020
Outstanding stock option awards	3,620,180	2,993,855
Shares of common stock available for future grants under the 2020 Stock Option and Incentive Plan	4,234,213	3,644,459
Shares of common stock available for future issuance under the 2020 Employee Stock Purchase Plan	613,098	700,000
Total shares reserved for future issuance	8,467,491	7,338,314

- Definition

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

+ References

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+ Details

Stock-Based Compensation

12 Months Ended

Dec. 31, 2021

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 administrator of the 2020 Plan, which is the compensation committee of the Board of Directors of the Company.

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, 2021, the 2020 Plan had 4,234,213 shares of common stock available for future issuance.

Options under the 2020 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 estimated 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.

Restricted Common Stock Awards

The Company granted restricted stock awards under the 2015 Plan. The purchase price of the restricted common stock awards was the estimated fair value as determined by the Company's Board of Directors at the issuance date. The shares vest from one to four years and vesting could be accelerated upon a change in control. A holder of an award may pay a total purchase price or a part of the purchase price for granted shares at any time during the vesting periods. Upon termination of employment, the Company has the right to repurchase any unvested restricted shares. The repurchase price for unvested shares of common stock will be the lower of (i) the fair market value on the date of repurchase or (ii) their original purchase price. During the vesting term, holders of restricted stock awards are deemed to be common stock shareholders and have dividends and voting rights.

The Company accounted for restricted stock awards as early exercised options and recognized a liability in other liabilities when cash was received for the purchase of shares of restricted stock. As shares of restricted stock vested, the Company reclassified the liability to common stock and additional paid in capital. As of December 31, 2021 and 2020, the Company recorded a liability included in accrued expenses and other liabilities of $2,000 and $10,000, respectively.

There were no grants of restricted stock awards during the years ended December 31, 2021 and 2020.

The following table summarizes restricted stock activity during the year ended December 31, 2021:


	Number of Shares	Weighted- Average Grant Date fair value
Outstanding and unvested, as of December 31, 2020	126,522	$	1.85
Issued	—	$	—
Vested	(103,164)	$	1.78
Repurchases	(1,517)	$	2.12
Outstanding and unvested, as of December 31, 2021	21,841	$	2.16

The aggregate fair value of restricted stock awards vested during the years ended December 31, 2021 and 2020 was $0.2 million each year. Total intrinsic value of outstanding unvested restricted stock awards as of December 31, 2021 and 2020 was $0.3 million and $2.9 million, respectively.

Incentive Stock Options and Nonqualified Stock Options

Stock options issued under either the 2015 Plan or the 2020 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,
	2021			2020			2019
Expected volatility	74.83%	-	76.31%	72.10%	-	77.50%	74.80%	-	82.53%
Risk-free interest rate	0.61 %	-	1.39 %	0.27 %	-	0.82 %	1.43%	-	2.59%
Expected dividend	—			—			—
Expected term (in years)	5.44	-	6.08	5.26	-	6.75	5	-	6.08
Underlying common stock fair value	15.2	-	38.23	6.22	-	28.79	5.15	-	7.08

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
Outstanding as of December 31, 2020	2,993,855	$	8.18	8.84	$	43,890
Granted	1,520,391	$	26.03
Exercised	(336,340)	$	5.21
Forfeited	(557,726)	$	16.4
Outstanding as of December 31, 2021	3,620,180	$	14.56	8.25	$	16,735
Exercisable as of December 31, 2021	1,368,543	$	9.76	7.66	$	9,426
Vested and expected to vest as of December 31, 2021	3,620,180	$	14.56	7.66	$	16,735

Aggregate intrinsic value represents the difference between the fair value of the underlying common stock and the exercise price as of December 31, 2021 and 2020. The weighted-average grant date fair value of options granted during years ended December 31, 2021 and 2020 was $16.94 per share and $7.27 per share, respectively.

2020 Employee Stock Purchase Plan

In June 2020, the Company adopted the Company's 2020 Employee Stock Purchase Plan (the "2020 ESPP"). The Company reserved 700,000 shares of common stock for future issuance under the plan. The 2020 ESPP provides that the

number of shares reserved and available for issuance will automatically increase on January 1 of each calendar year, beginning January 1, 2021, by the least of (i) 1.0% of the total number of shares of common stock outstanding on December 31 of the preceding calendar year, (ii) 700,000 shares or (iii) such lesser amount as determined by the administrator of the 2020 ESPP, which is the compensation committee of the Board of Directors of the Company.

Under the 2020 ESPP, eligible employees may purchase shares of our common stock through payroll deductions that cannot exceed 15% of each 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 of the offering period or 85% of the fair market value at the end of the purchase period, subject to tax limitations on the total value of the purchase. The 2020 ESPP is considered a compensatory plan, and the Company recorded $0.5 million, $0.5 million and nil in stock-based compensation expense for year ended December 31, 2021, 2020 and 2019. As of December 31, 2021, 86,902 shares of common stock were issued under the 2020 ESPP. The Company used Black-Scholes option pricing model to estimate stock-based compensation expense for the 2020 ESPP with the following assumptions:


	Year Ended December 31,
	2021	2020	2019
Risk-free interest rate	0.06% - 0.07%	0.11%	—
Expected term of options (in years)	0.50	0.58	—
Expected stock price volatility	67.16% - 89.51%	83.72%	—
Expected dividends	—	—	—

Stock-Based Compensation Expense

The following table presents the classification of stock-based compensation expense during the years ended December 31, 2021 and 2020 (in thousands):


	Year Ended December 31,
	2021		2020		2019
Research and development expenses	$	3,928	$	1,719	$	584
General and administrative expenses	6,509		2,176		1,245
Total stock-based compensation expense	$	10,437	$	3,895	$	1,829

As of December 31, 2021, there was $37,000 of unrecognized compensation costs that is expected to be recognized over the weighted-average periods of 0.38 years related to restricted stock awards. As of December 31, 2021, there was $24.2 million of unrecognized compensation costs that is expected to be recognized over the weighted-average periods of 2.5 years related to stock options.

Income Taxes

12 Months Ended

Dec. 31, 2021

Income Tax Disclosure [Abstract]

Income Taxes

Income TaxesThe Company had a pre-tax U.S. book loss of $97.3 million, $41.5 million, and $0.6 million for the years ended December 31, 2021, 2020 and 2019 respectively. During the years ended December 31, 2021, 2020 and 2019, 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,
	2021		2020		2019
Income tax computed at federal statutory rate	21.0	%	21.0	%	21.0	%
State taxes, net of federal tax benefit	7.7	%	7.4	%	2.7	%
General business credit—federal	5.3	%	5.3	%	295.9	%
Stock-based compensation	(0.7)	%	(1.0)	%	(50.0)	%
Other permanent differences	(0.1)	%	(0.1)	%	(2.4)	%
Change in valuation allowance	(33.2)	%	(32.6)	%	(267.7)	%
Effective income tax rate	0.0	%	—	%	(0.5)	%

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


	December 31,
	2021		2020
Deferred tax assets:
Net operating losses	$	51,554	$	27,047
Research and development credits	13,989		7,617
Accrued expenses	292		291
Other	775		474
Deferred rent	—		266
Lease liability	2,000		—
Stock based compensation	1,816		428
Total deferred tax assets	70,426		36,123
Deferred tax liabilities:
Fixed asset basis	$	(61)	$	(124)
Prepaid expenses	(921)		(558)
Right of use asset	(1,760)		—
Total deferred tax liabilities	(2,742)		(682)
Valuation allowance	67,684		35,441
Net deferred taxes	$	—	$	—

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


	December 31, 2021		Expiration Year
Net operating losses, federal (starting from January 1, 2018)	$	155,231	Does not expire
Net operating losses, federal (before January 1, 2018)	$	29,486	2035-2037
Net operating losses, state	$	182,964	2035-2041
Tax credits, federal	$	14,094	2036-2041
Tax credits, state	$	4,069	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, 2021 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, 2021 and 2020, 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, 2021 and 2020 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,
	2021		2020
Valuation allowance at the beginning of the year	$	35,441	$	21,929
Increases recorded to income tax provision	32,243		13,512
Valuation allowance at the end of the year	$	67,684	$	35,441

The Company’s U.S. federal and state income tax returns are generally subject to tax examinations for the tax years ended December 31, 2017 through December 31, 2021. 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, 2021, 2020 and 2019, 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,
	2021		2020		2019
January 1	$	2,007	$	1,355	$	855
Additions based on tax positions related to current year	1,081		513		570
Additions (reductions) for tax positions of prior year	417		139		(70)
December 31	$	3,505	$	2,007	$	1,355

On March 27, 2020, the Coronavirus Aid, Relief, and Economic Security Act (the "Cares Act") was enacted. The CARES Act changed net loss carryforward and back provisions and the business interest expenses limitation. The Company has evaluated the impact of the CARES Act and determined that none of the changes would result in a material cash benefit to the Company.

- 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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
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-Section 50
-Paragraph 21
-URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32857-109319

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 11.C)
-URI http://asc.fasb.org/extlink&oid=122134291&loc=d3e330215-122817

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 17
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32809-109319

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 6.I.5.Q1)
-URI http://asc.fasb.org/extlink&oid=122134291&loc=d3e330036-122817

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 14
-URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32705-109319

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 270
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6424409&loc=d3e44925-109338

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-URI http://asc.fasb.org/topic&trid=2144680

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6424122&loc=d3e41874-109331

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h)(2))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

+ Details

Commitments and Contingencies	12 Months Ended
Commitments and Contingencies	Dec. 31, 2021
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. License and Collaboration Agreements Potential payments related to the Company’s license and research agreements, including milestone and royalty payments, are detailed in Notes 6 and 7. 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.

Leases

12 Months Ended

Dec. 31, 2021

Leases [Abstract]

Leases

On January 1, 2021, the Company adopted ASC 842 and the following disclosures as of and for the year ended December 31, 2021 are presented under ASC 842.

In February 2018, the Company entered into a non-cancelable lease agreement (the “Lease”) for premises consisting of approximately 32,974 square feet located in South San Francisco, California (the “Premises”). The Company moved into the Premises in July 2018. The Premises is being used for the Company’s corporate headquarters and principal operating facility. The term of the Lease is eighty-four months, which commenced on July 1, 2018. Base rent was abated for the first two months of the lease term and thereafter is $0.2 million per month during the first year of the lease term, with specified annual increases thereafter. The Company paid a refundable security deposit of approximately $0.4 million, which is included in other non-current assets in the Balance Sheets at December 31, 2021 and 2020. The Company has the right to extend the lease term by seven years upon written notice not more than twelve months nor less than nine months prior to the expiration of the original lease term, with monthly payments equal to the “fair rental value” as defined in the Lease. The exercise of lease renewal options is at the sole discretion of the Company and is not included in the ROU asset and lease liability as it is not reasonably certain of exercise. This lease does not contain material variable rent payments, residual value guarantees, covenants, or other restrictions.

For the year ended December 31, 2021, the Company recognized expenses associated with the operating leases of $2.3 million. Additionally, the Company incurred variable lease costs of $0.9 million which is comprised 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 year ended December 31, 2021. Cash paid for amounts included in the measurement of operating lease liabilities was $2.4 million.

Maturities of the Company's operating lease liability as of December 31, 2021 were as follows:


Year ending December 31:	Operating Lease
2022	$	2,360
2023	2,295
2024	2,365
2025	1,202
2026	—
Total lease payments	$	8,222
Less: Present value discount	1,028
Total operating lease liabilities	$	7,194

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


	As of December 31, 2021
Weighted-average remaining lease term (in years)	3.40
Weighted-average discount rate	7.90	%

Total rent expense under ASC 840 was $2.5 million during each of the years ending December 31, 2020 and 2019.

Future minimum lease payments under the Lease as of December 31, 2021 were as follows (in thousands):


Year ending December 31:	Operating Lease
2022	$	2,098
2023	2,171
2024	2,247
2025	1,144
Total lease payments	$	7,660

Related Party Transactions	12 Months Ended
Related Party Transactions	Dec. 31, 2021
Related Party Transactions [Abstract]
Related Party Transactions	Related Party TransactionsIn 2019, certain employees of Third Rock Ventures, a stockholder of the Company, provided consulting services to the Company. Commencing January 2020, Third Rock Ventures ceased providing management consulting services to the Company. The Company recorded no consulting expenses for consulting services provided by Third Rock Ventures during the years ended December 31, 2021 and 2020. The Company recorded Third Rock Ventures consulting expenses to general and administrative expense of $36,000 during the year ended December 31, 2019.In June 2021, the Company granted 26,572 stock options with a grant date fair value of $0.5 million to partners of Third Rock Ventures who are also serving as non-employee directors on the Company's Board of Directors. The shares of common stock subject to these options vest 25% on the first day of each calendar quarter for three quarters with the final vest date being the earlier of (i) the one-year anniversary of the grant date or (ii) the next Annual Meeting of Stockholders. In March 2020, the Company granted 26,573 stock options with a grant date fair value of $0.1 million to a partner at Third Rock Ventures, who is also serving as a non-employee director on the Company’s Board of Directors. The common shares subject to these options vest 1/12th on the last day of each calendar quarter over a three-year period and commenced vesting upon our IPO. In order to vest at each calendar quarter end date, the shareholder must be providing continuous service to the Company through such vesting date. The stock-based compensation expense related to these options was immaterial during the years ended December 31, 2021.

Defined Contribution Plan	12 Months Ended
Defined Contribution Plan	Dec. 31, 2021
Retirement Benefits [Abstract]
Defined Contribution Plan	Defined Contribution PlanThe 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 $0.6 million, $0.4 million and $0.2 million during the years ended December 31, 2021, 2020 and 2019, respectively.

Net Loss Per Share Attributable to Common Stockholders

12 Months Ended

Dec. 31, 2021

Earnings Per Share [Abstract]

Net Loss Per Share Attributable to Common Stockholders

The following outstanding shares of potentially dilutive securities 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,
	2021	2020	2019
Redeemable convertible preferred stock (on an as-converted basis)	—	—	18,442,233
Options to purchase common stock	3,620,180	2,993,855	1,337,501
Restricted stock awards granted and not purchased	—	4,195	4,195
Unvested restricted shares	21,841	126,522	302,211
Total	3,642,021	3,124,572	20,086,140

A reconciliation of the numerator and denominator used in the calculation of the basic and diluted net loss per share attributable to common stockholders is as follows (in thousands, except share and per share amounts):


	Year Ended December 31,
	2021		2020		2019
Net loss per share:
Numerator
Net loss	$	(97,263)	$	(41,533)	$	(631)
Less: accretion to redemption value and dividends on redeemable convertible preferred shares	—		—		(6,225)
Net loss attributable to common stockholders	$	(97,263)	$	(41,533)	$	(6,856)
Denominator
Weighted-average common shares outstanding used to calculate net loss per share attributable to common stockholders:
Basic	35,846,421		21,344,236		1,623,358
Diluted	35,846,421		21,344,236		1,623,358
Net loss per share attributable to common stockholders:
Basic	$	(2.71)	$	(1.95)	$	(4.22)
Diluted	$	(2.71)	$	(1.95)	$	(4.22)

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2021

Accounting Policies [Abstract]

Basis of Presentation

Use of Estimates

Revenue Recognition

Licenses of Intellectual Property

Milestone Payments

Research and development services

Royalties:

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

Concentration of Credit Risk and Other Risks and Uncertainties Policy

Concentration of Credit Risk and Other Risks and Uncertainties

Segments

Cash and Cash Equivalents

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 and Rent Expense

Leases

Impairment of Long-Lived Assets

Redeemable Convertible Preferred Stock

Research and Development Expenses

Stock-Based Compensation

The Black-Scholes option-pricing model, used to estimate fair value of stock-based awards, 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

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

Comprehensive Loss

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

Net Loss Per Share

Recently Issued Accounting Pronouncements

Recently Adopted Accounting Pronouncements

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2021

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

Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2021

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, Money Market Funds and short-term investments by significant investment category as of December 31, 2021 and 2020 (in thousands):


	As of December 31, 2021
	Adjusted Cost		Unrealized Gains		Unrealized Losses		Market Value
Level 1:
Money Market Funds	$	15,329	$	—	$	—	$	15,329
Level 2:
U.S. government agency securities included in short-term investments	5,003		—		—		5,003
Corporate debt securities included in cash and cash equivalents and short-term investments	163,626		1		(202)		163,425
Total financial assets	$	183,958	$	1	$	(202)	$	183,757


	As of December 31, 2020
	Adjusted Cost		Unrealized Gains		Unrealized Losses		Market Value
Level 1:
Money Market Funds	$	27,686	$	—	$	—	$	27,686
Level 2:
U.S. Treasury securities included in short-term investments	63,101		4		(1)		63,104
U.S. government agency securities included in short-term investments	54,183		10		—		54,193
Corporate debt securities included in cash and cash equivalents and short-term investments	118,759		1		(46)		118,714
Total financial assets	$	263,729	$	15	$	(47)	$	263,697

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, 2021:


	Adjusted Cost		Market Value
Mature in 1 year or less	$	114,076	$	113,974
Mature in 1 to 2 years	35,054		34,956
Total	$	149,130	$	148,930

Property and Equipment, net (Tables)

12 Months Ended

Dec. 31, 2021

Property, Plant and Equipment [Abstract]

Schedule of Property and Equipment, Net

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


	December 31,
	2021		2020
Laboratory equipment	$	7,947	$	6,540
Leasehold improvements	1,618		947
Construction-in-progress	38		300
Computer equipment and software	22		22
Total property and equipment	9,625		7,809
Less: Accumulated depreciation	(5,019)		(3,488)
Total property and equipment, net	$	4,606	$	4,321

Prepaid expenses and other current assets (Tables)

12 Months Ended

Dec. 31, 2021

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

Schedule of Prepaid Expenses and Other Current Assets

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


	December 31,
	2021		2020
Prepaid research and development	$	2,819	$	1,898
Prepaid insurance	2,585		1,459
Prepaid licenses	819		665
Interest receivable	385		386
Other	156		90
Total prepaid expenses and other current assets	$	6,764	$	4,498

Accrued Liabilities and Other Long-Term Liabilities (Tables)

12 Months Ended

Dec. 31, 2021

Accrued Liabilities and Other Liabilities [Abstract]

Schedule of Accrued Liabilities

Accrued liabilities consisted of the following (in thousands):


	December 31,
	2021		2020
Accrued research and development expenses	$	5,868	$	3,274
Accrued compensation and benefits	5,216		4,542
Other accrued liabilities	907		1,675
Deferred rent	—		85
Total accrued liabilities	$	11,991	$	9,576

Summary of Other Long-Term Liabilities

Other long-term liabilities consisted of the following (in thousands):


	December 31,
	2021		2020
Deferred rent	$	—	$	581
Leasehold incentive obligation	—		283
Other liabilities — deposits	—		2
Total other long-term liabilities	$	—	$	866

Common Stock (Tables)

12 Months Ended

Dec. 31, 2021

Equity [Abstract]

Schedule of Shares Reserved for Future Issuance

Shares reserved for future issuance


	December 31,
	2021	2020
Outstanding stock option awards	3,620,180	2,993,855
Shares of common stock available for future grants under the 2020 Stock Option and Incentive Plan	4,234,213	3,644,459
Shares of common stock available for future issuance under the 2020 Employee Stock Purchase Plan	613,098	700,000
Total shares reserved for future issuance	8,467,491	7,338,314

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2021

Share-based Payment Arrangement [Abstract]

Summary of Restricted Stock Activity

The following table summarizes restricted stock activity during the year ended December 31, 2021:


	Number of Shares	Weighted- Average Grant Date fair value
Outstanding and unvested, as of December 31, 2020	126,522	$	1.85
Issued	—	$	—
Vested	(103,164)	$	1.78
Repurchases	(1,517)	$	2.12
Outstanding and unvested, as of December 31, 2021	21,841	$	2.16

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,
	2021			2020			2019
Expected volatility	74.83%	-	76.31%	72.10%	-	77.50%	74.80%	-	82.53%
Risk-free interest rate	0.61 %	-	1.39 %	0.27 %	-	0.82 %	1.43%	-	2.59%
Expected dividend	—			—			—
Expected term (in years)	5.44	-	6.08	5.26	-	6.75	5	-	6.08
Underlying common stock fair value	15.2	-	38.23	6.22	-	28.79	5.15	-	7.08

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
Outstanding as of December 31, 2020	2,993,855	$	8.18	8.84	$	43,890
Granted	1,520,391	$	26.03
Exercised	(336,340)	$	5.21
Forfeited	(557,726)	$	16.4
Outstanding as of December 31, 2021	3,620,180	$	14.56	8.25	$	16,735
Exercisable as of December 31, 2021	1,368,543	$	9.76	7.66	$	9,426
Vested and expected to vest as of December 31, 2021	3,620,180	$	14.56	7.66	$	16,735

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

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


	Year Ended December 31,
	2021	2020	2019
Risk-free interest rate	0.06% - 0.07%	0.11%	—
Expected term of options (in years)	0.50	0.58	—
Expected stock price volatility	67.16% - 89.51%	83.72%	—
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, 2021 and 2020 (in thousands):


	Year Ended December 31,
	2021		2020		2019
Research and development expenses	$	3,928	$	1,719	$	584
General and administrative expenses	6,509		2,176		1,245
Total stock-based compensation expense	$	10,437	$	3,895	$	1,829

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2021

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,
	2021		2020		2019
Income tax computed at federal statutory rate	21.0	%	21.0	%	21.0	%
State taxes, net of federal tax benefit	7.7	%	7.4	%	2.7	%
General business credit—federal	5.3	%	5.3	%	295.9	%
Stock-based compensation	(0.7)	%	(1.0)	%	(50.0)	%
Other permanent differences	(0.1)	%	(0.1)	%	(2.4)	%
Change in valuation allowance	(33.2)	%	(32.6)	%	(267.7)	%
Effective income tax rate	0.0	%	—	%	(0.5)	%

Summary of Deferred Tax Assets and Liabilities

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


	December 31,
	2021		2020
Deferred tax assets:
Net operating losses	$	51,554	$	27,047
Research and development credits	13,989		7,617
Accrued expenses	292		291
Other	775		474
Deferred rent	—		266
Lease liability	2,000		—
Stock based compensation	1,816		428
Total deferred tax assets	70,426		36,123
Deferred tax liabilities:
Fixed asset basis	$	(61)	$	(124)
Prepaid expenses	(921)		(558)
Right of use asset	(1,760)		—
Total deferred tax liabilities	(2,742)		(682)
Valuation allowance	67,684		35,441
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, 2021		Expiration Year
Net operating losses, federal (starting from January 1, 2018)	$	155,231	Does not expire
Net operating losses, federal (before January 1, 2018)	$	29,486	2035-2037
Net operating losses, state	$	182,964	2035-2041
Tax credits, federal	$	14,094	2036-2041
Tax credits, state	$	4,069	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, 2021 and 2020 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,
	2021		2020
Valuation allowance at the beginning of the year	$	35,441	$	21,929
Increases recorded to income tax provision	32,243		13,512
Valuation allowance at the end of the year	$	67,684	$	35,441

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,
	2021		2020		2019
January 1	$	2,007	$	1,355	$	855
Additions based on tax positions related to current year	1,081		513		570
Additions (reductions) for tax positions of prior year	417		139		(70)
December 31	$	3,505	$	2,007	$	1,355

Leases (Tables)

12 Months Ended

Dec. 31, 2021

Leases [Abstract]

Schedule of Operating Lease Liability

Maturities of the Company's operating lease liability as of December 31, 2021 were as follows:


Year ending December 31:	Operating Lease
2022	$	2,360
2023	2,295
2024	2,365
2025	1,202
2026	—
Total lease payments	$	8,222
Less: Present value discount	1,028
Total operating lease liabilities	$	7,194

Schedule 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, 2021
Weighted-average remaining lease term (in years)	3.40
Weighted-average discount rate	7.90	%

Schedule of Future Minimum Lease Payments

Future minimum lease payments under the Lease as of December 31, 2021 were as follows (in thousands):


Year ending December 31:	Operating Lease
2022	$	2,098
2023	2,171
2024	2,247
2025	1,144
Total lease payments	$	7,660

Net Loss Per Share Attributable to Common Stockholders (Tables)

12 Months Ended

Dec. 31, 2021

Earnings Per Share [Abstract]

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


	Year Ended December 31,
	2021	2020	2019
Redeemable convertible preferred stock (on an as-converted basis)	—	—	18,442,233
Options to purchase common stock	3,620,180	2,993,855	1,337,501
Restricted stock awards granted and not purchased	—	4,195	4,195
Unvested restricted shares	21,841	126,522	302,211
Total	3,642,021	3,124,572	20,086,140

Reconciliation of Numerator and Denominator Used in Calculation of Basic and Diluted Net Loss Per Share


	Year Ended December 31,
	2021		2020		2019
Net loss per share:
Numerator
Net loss	$	(97,263)	$	(41,533)	$	(631)
Less: accretion to redemption value and dividends on redeemable convertible preferred shares	—		—		(6,225)
Net loss attributable to common stockholders	$	(97,263)	$	(41,533)	$	(6,856)
Denominator
Weighted-average common shares outstanding used to calculate net loss per share attributable to common stockholders:
Basic	35,846,421		21,344,236		1,623,358
Diluted	35,846,421		21,344,236		1,623,358
Net loss per share attributable to common stockholders:
Basic	$	(2.71)	$	(1.95)	$	(4.22)
Diluted	$	(2.71)	$	(1.95)	$	(4.22)

Organization and Description of Business - Additional Information (Detail) $ / shares in Units, $ in Millions		1 Months Ended
	May 22, 2020	Jun. 30, 2020 USD ($) $ / shares shares	Dec. 31, 2021 shares	Dec. 31, 2020 shares
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reverse stock split, conversion ratio	0.13986014
Common stock, shares issued (in shares)			36,083,301	35,552,795
Initial Public Offering
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reverse stock split, conversion ratio		7.15
Initial public offering, shares issued (in shares)		10,350,000
Share price of shares issued in initial public offering (in dollars per share) \| $ / shares		$ 16.00
Proceeds from the initial public offering \| $		$ 148.3
Underwriting discounts, commissions and offering expenses \| $		$ 5.7
Convertible preferred stock converted into common shares		160,389,279
Reclassification of convertible preferred stock into additional paid in capital upon initial public offering \| $		$ 238.3
Initial Public Offering \| Underwriters
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Initial public offering, shares issued (in shares)		1,350,000
Initial Public Offering \| Common Stock
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Initial public offering, shares issued (in shares)		9,000,000
Private Placement
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Common stock, shares issued (in shares)		625,000
Share price \| $ / shares		$ 16.00
Proceeds from issuance of common stock \| $		$ 10.0
Private Placement \| Pliant Therapeutics, Inc.
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Percentage of noncontrolling ownership		6.10%

Summary of Significant Accounting Policies - Additional Information (Details)	12 Months Ended
	Dec. 31, 2021 USD ($) segment	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Jan. 01, 2021 USD ($)
Accounting Policies [Line Items]
Percentage of revenue contributed by related party	100.00%	100.00%	100.00%
Number of operating segments \| segment	1
Number of reportable segments \| segment	1
Debt instrument remaining maturity period at date of purchase	3 months
Impairment of long-lived assets	$ 0	$ 0	$ 0
Expected dividends	0.00%	0.00%	0.00%
Operating lease right-of-use assets	$ 6,330,000	$ 0
Total operating lease liabilities	$ 7,194,000
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.
Accounting Standards Update 2016-02
Accounting Policies [Line Items]
Operating lease right-of-use assets				$ 8,000,000
Total operating lease liabilities				8,900,000
Deferred rent and lease incentives				$ 900,000

Summary of Significant Accounting Policies - Summary of Useful Lives of Property and Equipment (Details)	12 Months Ended
	Dec. 31, 2021
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

Financial Instruments - Summary of Cash and Cash Equivalents, Money Market Funds and Short-term Investments by Significant Investment Category (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	$ 183,958	$ 263,729
Unrealized Gains	1	15
Unrealized Losses	(202)	(47)
Market Value	183,757	263,697
Level 1 \| Money Market Funds
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	15,329	27,686
Unrealized Gains	0	0
Unrealized Losses	0	0
Market Value	15,329	27,686
Level 2 \| Corporate debt securities included in cash and cash equivalents and short-term investments
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	163,626	118,759
Unrealized Gains	1	1
Unrealized Losses	(202)	(46)
Market Value	163,425	118,714
Level 2 \| U.S. Treasury securities included in short-term investments
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost		63,101
Unrealized Gains		4
Unrealized Losses		(1)
Market Value		63,104
Level 2 \| U.S. government agency securities included in short-term investments
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	5,003	54,183
Unrealized Gains	0	10
Unrealized Losses	0	0
Market Value	$ 5,003	$ 54,193

Financial Instruments - Summery of Remaining Contractual Maturities of Company's Short-term Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	$ 183,958	$ 263,729
Market Value	183,757	$ 263,697
Short Term Investments
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	149,130
Market Value	148,930
Short Term Investments \| Mature in 1 year or less
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	114,076
Market Value	113,974
Short Term Investments \| Mature in 1 to 2 years
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	35,054
Market Value	$ 34,956

Financial Instruments - Additional Information (Details) - USD ($)	Dec. 31, 2021	Dec. 31, 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Transfers of assets between Level 1 and Level 2	$ 0	$ 0
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

Property and Equipment, net - Schedule of Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 9,625	$ 7,809
Less: Accumulated depreciation	(5,019)	(3,488)
Total property and equipment, net	4,606	4,321
Laboratory equipment
Property, Plant and Equipment [Line Items]
Total property and equipment	7,947	6,540
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total property and equipment	1,618	947
Construction-in-progress
Property, Plant and Equipment [Line Items]
Total property and equipment	38	300
Computer equipment and software
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 22	$ 22

Property and Equipment, net - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 1,535	$ 1,310	$ 1,113

Prepaid expenses and other current assets (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid research and development	$ 2,819	$ 1,898
Prepaid insurance	2,585	1,459
Prepaid licenses	819	665
Interest receivable	385	386
Other	156	90
Total prepaid expenses and other current assets	$ 6,764	$ 4,498

Accrued Liabilities and Other Long-Term Liabilities - Summary of Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Accrued Liabilities and Other Liabilities [Abstract]
Accrued research and development expenses	$ 5,868	$ 3,274
Accrued compensation and benefits	5,216	4,542
Other accrued liabilities	907	1,675
Deferred rent	0	85
Total accrued liabilities	$ 11,991	$ 9,576

Accrued Liabilities and Other Long-Term Liabilities - Summary of Other Long-Term Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Accrued Liabilities and Other Liabilities [Abstract]
Deferred rent	$ 0	$ 581
Leasehold incentive obligation	0	283
Other liabilities — deposits	0	2
Total other long-term liabilities	$ 0	$ 866

Novartis Collaboration and License Agreement (the "Novartis Agreement") - Additional Information (Details) - Novartis	3 Months Ended	12 Months Ended
	Mar. 31, 2020 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($) research
Novartis Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Proceeds from upfront non-refundable license fee				$ 50,000,000
Revenue recognized from related party		$ 2,000,000	$ 41,800,000
Receivable from related party transactions		2,000,000	9,300,000
Contract assets		0	0
Contract liabilities		0	0
Novartis Agreement \| Achievement of First Patient Dosing Milestone
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenue recognized from related party		391,000,000	$ 25,000,000
Novartis Agreement \| Research and Development
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenue recognized from related party	$ 16,800,000	7,600,000		7,100,000
Novartis Agreement \| License Fee
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenue recognized from related party				$ 50,000,000
Novartis Agreement \| Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of Integrin research targets \| research				3
Collaboration and license agreement, integrin research targets amount				$ 416,000,000
Novartis Agreement RD For PLN-1474
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Transaction price of Novartis agreement		20,000,000		19,600,000
Novartis Agreement RD For Integrin Research Targets \| Research and Development
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Transaction price of Novartis agreement		$ 13,400,000		$ 13,400,000

Regents of the University of California License Agreement (the “UC Agreement”) - Additional Information (Details) $ in Millions	1 Months Ended
	Jun. 30, 2020 USD ($)
License Agreements \| UC Regents
License Agreements [Line Items]
Milestone and annual royalty paid	$ 2.4

Adimab Development and Option Agreement (the "Adimab Agreement") - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research and development expense	$ 77,549	$ 66,193	$ 47,353
FTE costs \| Adimab Agreement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research and development expense	$ 28	$ 200	$ 200

Redeemable Convertible Preferred Stock - Additional Information (Details)	Dec. 31, 2021 shares
Redeemable Convertible Preferred Stock
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares outstanding (in shares)	0

Common Stock - Additional Information (Details)	12 Months Ended
Common Stock - Additional Information (Details)	Dec. 31, 2021 vote $ / shares shares	Dec. 31, 2020 $ / shares shares
Equity [Abstract]
Common stock, shares authorized (in shares) \| shares	300,000,000	300,000,000
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, voting rights \| vote	1
Dividends paid	$ 0

Common Stock - Schedule of Shares Reserved for Future Issuance (Details) - shares	Dec. 31, 2021	Dec. 31, 2020
Class of Stock [Line Items]
Total shares reserved for future issuance (in shares)	8,467,491	7,338,314
2020 Equity Incentive Plan
Class of Stock [Line Items]
Total shares reserved for future issuance (in shares)	4,234,213	3,644,459
Shares of common stock available for future issuance under the 2020 Employee Stock Purchase Plan
Class of Stock [Line Items]
Total shares reserved for future issuance (in shares)	613,098	700,000
Outstanding stock option awards
Class of Stock [Line Items]
Total shares reserved for future issuance (in shares)	3,620,180	2,993,855

Stock-Based Compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	May 31, 2020	Dec. 31, 2021	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total shares reserved for future issuance (in shares)		8,467,491	7,338,314
Incentive Stock Options and Nonqualified Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant date fair value of stock option (in dollars per share)		$ 16.94	$ 7.27
Restricted Stock Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost		$ 37
Unrecognized compensation expense, weighted average period		4 months 17 days
Outstanding stock option awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total shares reserved for future issuance (in shares)		3,620,180	2,993,855
Unrecognized compensation expense, weighted average period		2 years 6 months
Unrecognized compensation cost		$ 24,200
2020 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock shares outstanding percentage	5.00%
Total shares reserved for future issuance (in shares)		4,234,213	3,644,459
Exercise price as a percentage of estimated grant date fair value of shares	10.00%
Expiration period from date of grant	5 years
2020 Equity 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%
Restricted Common Stock Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares granted (in shares)		0
Aggregate fair value of restricted stock awards vested		$ 200	$ 200
Total intrinsic value of outstanding unvested restricted stock awards		300	2,900
Restricted Common Stock Awards \| Accrued Expenses and Other Liabilities
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Accrued expenses and other liabilities		$ 2	$ 10
Restricted Common Stock Awards \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	4 years
Restricted Common Stock Awards \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	1 year
2015 Equity and 2020 Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration period from date of grant		10 years
Vesting period		4 years

Stock-Based Compensation - Summary of Restricted Stock Activity (Details) - Restricted Common Stock Awards	12 Months Ended
	Dec. 31, 2021 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Outstanding and unvested, beginning balance (in shares) \| shares	126,522
Number of shares granted during period (in shares) \| shares	0
Number of Shares, Vested (in shares) \| shares	(103,164)
Number of Shares, Repurchases (in shares) \| shares	(1,517)
Number of Shares, Outstanding and unvested, ending balance (in shares) \| shares	21,841
Weighted-Average Grant Date fair value, Outstanding and unvested, beginning balance (in dollars per share) \| $ / shares	$ 1.85
Weighted-Average Grant Date fair value, Issued (in dollars per share) \| $ / shares	0
Weighted-Average Grant Date fair value, Vested (in dollars per share) \| $ / shares	1.78
Weighted-Average Grant Date fair value, Repurchases (in dollars per share) \| $ / shares	2.12
Weighted-Average Grant Date fair value, Outstanding and unvested, ending balance (in dollars per share) \| $ / shares	$ 2.16

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, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividends	0.00%	0.00%	0.00%
Incentive Stock Options and Nonqualified Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility, minimum	74.83%	72.10%	74.80%
Expected volatility, maximum	76.31%	77.50%	82.53%
Risk-free interest rate, minimum	0.61%	0.27%	1.43%
Risk-free interest rate, maximum	1.39%	0.82%	2.59%
Incentive Stock Options and Nonqualified Stock Options \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	5 years 5 months 8 days	5 years 3 months 3 days	5 years
Underlying common stock fair value	$ 15.2	$ 6.22	$ 5.15
Incentive Stock Options and Nonqualified Stock Options \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	6 years 29 days	6 years 9 months	6 years 29 days
Underlying common stock fair value	$ 38.23	$ 28.79	$ 7.08
Shares of common stock available for future issuance under the 2020 Employee Stock Purchase 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 months	6 months 29 days	0 years

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, 2021	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Options, Outstanding, Beginning balance (in shares)	2,993,855
Options granted (in shares)	1,520,391
Number of Options, Exercised (in shares)	(336,340)
Number of Options, Forfeited (in shares)	(557,726)
Number of Options, Outstanding, Ending balance (in shares)	3,620,180	2,993,855
Number of Options, Exercisable (in shares)	1,368,543
Number of Options, Vested and expected to vest (in shares)	3,620,180
Weighted- Average Exercise Price per Share, Outstanding, Beginning balance (in dollars per share)	$ 8.18
Weighted- Average Exercise Price per Share, Granted (in dollars per share)	26.03
Weighted- Average Exercise Price per Share, Exercised (in dollars per share)	5.21
Weighted- Average Exercise Price per Share, Forfeited (in dollars per share)	16.4
Weighted- Average Exercise Price per Share, Outstanding, Ending balance (in dollars per share)	14.56	$ 8.18
Weighted- Average Exercise Price per Share, Exercisable (in dollars per share)	9.76
Weighted- Average Exercise Price per Share, Vested and expected to vest (in dollars per share)	$ 14.56
Weighted- Average Remaining Contractual Term (in Years), Outstanding	8 years 3 months	8 years 10 months 2 days
Weighted- Average Remaining Contractual Term (in Years), Exercisable	7 years 7 months 28 days
Weighted- Average Remaining Contractual Term (in Years), Vested and expected to vest	7 years 7 months 28 days
Aggregate Intrinsic Value, Outstanding balance	$ 16,735	$ 43,890
Aggregate Intrinsic Value, Exercisable	9,426
Aggregate Intrinsic Value, Vested and expected to vest	$ 16,735

Stock-Based Compensation - 2020 Employee Stock Purchase Plan - Additional Information (Details) - USD ($)	1 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total shares reserved for future issuance (in shares)		8,467,491	7,338,314
Stock-based compensation expense		$ 10,437,000	$ 3,895,000	$ 1,829,000
Shares of common stock available for future issuance under the 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
Common stock shares outstanding percentage	1.00%
Employee stock purchase plan, description	The 2020 ESPP provides that the number of shares reserved and available for issuance will automatically increase on January 1 of each calendar year, beginning January 1, 2021, by the least of (i) 1.0% of the total number of shares of common stock outstanding on December 31 of the preceding calendar year, (ii) 700,000 shares or (iii) such lesser amount as determined by the administrator of the 2020 ESPP, which is the compensation committee of the Board of Directors of the Company.
Percentage of payroll deductions			15.00%
Employee stock purchase plan offering period	6 months
Common stock fair market value percentage	85.00%
Stock-based compensation expense		$ 500,000	$ 500,000	$ 0
Number of common stock issued (in shares)		86,902

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, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividends	0.00%	0.00%	0.00%
Shares of common stock available for future issuance under the 2020 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate		0.11%	0.00%
Expected term of options (in years)	6 months	6 months 29 days	0 years
Expected stock price volatility		83.72%	0.00%
Expected dividends	0.00%	0.00%	0.00%
Shares of common stock available for future issuance under the 2020 Employee Stock Purchase Plan \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	0.06%
Expected stock price volatility	67.16%
Shares of common stock available for future issuance under the 2020 Employee Stock Purchase Plan \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	0.07%
Expected stock price volatility	89.51%

Stock-Based Compensation - Summary of Classification of Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 10,437	$ 3,895	$ 1,829
Research and development expenses
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	3,928	1,719	584
General and administrative expenses
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 6,509	$ 2,176	$ 1,245

Income Taxes - Additional Information (Details)	12 Months Ended
Income Taxes - Additional Information (Details)	Dec. 31, 2021 USD ($) taxExamination	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Income Tax Disclosure [Abstract]
Pre-tax U.S. book loss	$ (97,300,000)	$ 41,500,000	$ 600,000
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	$ 0

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, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Income tax computed at federal statutory rate	21.00%	21.00%	21.00%
State taxes, net of federal tax benefit	7.70%	7.40%	2.70%
General business credit—federal	5.30%	5.30%	295.90%
Stock-based compensation	(0.70%)	(1.00%)	(50.00%)
Other permanent differences	(0.10%)	(0.10%)	(2.40%)
Change in valuation allowance	(33.20%)	(32.60%)	(267.70%)
Effective income tax rate	0.00%	0.00%	(0.50%)

Income Taxes - Summary of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Net operating losses	$ 51,554	$ 27,047
Research and development credits	13,989	7,617
Accrued expenses	292	291
Other	775	474
Deferred rent	0	266
Lease liability	2,000	0
Stock based compensation	1,816	428
Total deferred tax assets	70,426	36,123
Deferred tax liabilities:
Fixed asset basis	(61)	(124)
Prepaid expenses	(921)	(558)
Right of use asset	(1,760)	0
Total deferred tax liabilities	(2,742)	(682)
Valuation allowance	67,684	35,441	$ 21,929
Net deferred taxes	$ 0	$ 0

Income Taxes - Summary of Net Operating Losses and Tax Credit Carry Forwards (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2021 USD ($)
Federal
Operating Loss Carryforwards [Line Items]
Tax credits	$ 14,094
Federal \| Starting from January 1, 2018
Operating Loss Carryforwards [Line Items]
Net operating losses	155,231
Federal \| Before January 1, 2018
Operating Loss Carryforwards [Line Items]
Net operating losses	$ 29,486
Federal \| Earliest Tax Year
Operating Loss Carryforwards [Line Items]
Net operating losses, Expiration year	2035
Federal \| Latest Tax Year
Operating Loss Carryforwards [Line Items]
Net operating losses, Expiration year	2037
State
Operating Loss Carryforwards [Line Items]
Net operating losses	$ 182,964
Tax credits	$ 4,069
State \| Earliest Tax Year
Operating Loss Carryforwards [Line Items]
Net operating losses, Expiration year	2035
Tax credits Expiration year	2036
State \| Latest Tax Year
Operating Loss Carryforwards [Line Items]
Net operating losses, Expiration year	2041
Tax credits Expiration year	2041

Income Taxes - Summary of Changes in Valuation Allowance for Deferred Tax Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Valuation Allowance [Abstract]
Valuation allowance at the beginning of the year	$ 35,441	$ 21,929
Increases recorded to income tax provision	32,243	13,512
Valuation allowance at the end of the year	$ 67,684	$ 35,441

Income Taxes - Summary of Reconciliation of Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense [Abstract]
January 1	$ 2,007	$ 1,355	$ 855
Additions based on tax positions related to current year	1,081	513	570
Additions (reductions) for tax positions of prior year	417	139	(70)
December 31	$ 3,505	$ 2,007	$ 1,355

Commitments and Contingencies - Additional Information (Details)	12 Months Ended
	Dec. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Contractual arrangements cancellation period	30 days

Leases - Additional information (Details) $ in Thousands	1 Months Ended	12 Months Ended
Leases - Additional information (Details) $ in Thousands	Feb. 28, 2018 USD ($) ft²	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Lessee, Lease, Description [Line Items]
Period of base rent abatement	2 months
Base rent abated amount	$ 200
Lease costs		$ 2,300
Variable lease payments		900
Operating leases, rent expense			$ 2,500	$ 2,500
Operating lease payments		$ 2,400
California
Lessee, Lease, Description [Line Items]
Leased premises under non cancelable operating lease \| ft²	32,974
Lease term	84 months
Lease term extension period		7 years
California \| Minimum
Lessee, Lease, Description [Line Items]
Lease term extension notice period	12 months
California \| Maximum
Lessee, Lease, Description [Line Items]
Lease term extension notice period	9 months
California \| Other Non-current Assets
Lessee, Lease, Description [Line Items]
Refundable security deposit		$ 400	$ 400

Leases - Schedule of Operating Lease Liability (Details) $ in Thousands	Dec. 31, 2021 USD ($)
Operating Leases, After Adoption of 842:
2022	$ 2,360
2023	2,295
2024	2,365
2025	1,202
2026	0
Total lease payments	8,222
Less: Present value discount	1,028
Total operating lease liabilities	$ 7,194

Leases - Weighted-average Remaining Lease Terms and Discount Rates (Details)	Dec. 31, 2021
Leases [Abstract]
Weighted-average remaining lease term (in years)	3 years 4 months 24 days
Weighted-average discount rate	7.90%

Leases - Future Minimum Lease Payments (Details) - California $ in Thousands	Dec. 31, 2021 USD ($)
Lessee, Lease, Description [Line Items]
2022	$ 2,098
2023	2,171
2024	2,247
2025	1,144
Total lease payments	$ 7,660

Related Party Transactions - Additional Information (Details) - USD ($)	1 Months Ended		12 Months Ended
	Jun. 30, 2021	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020
Outstanding stock option awards
Related Party Transaction [Line Items]
Options granted (in shares)	26,572
Grant date fair value of stock option	$ 500,000
Vesting rights, percent	25.00%
Third Rock Ventures \| Non-employee Director \| Outstanding stock option awards
Related Party Transaction [Line Items]
Options granted (in shares)		26,573
Grant date fair value of stock option		$ 100,000
Vesting rights			The common shares subject to these options vest 1/12th on the last day of each calendar quarter over a three-year period and commenced vesting upon our IPO.
Vesting period			3 years
General and administrative expenses \| Third Rock Ventures
Related Party Transaction [Line Items]
Consulting service expenses			$ 0	$ 36,000

Defined Contribution Plan - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Retirement Benefits [Abstract]
Payment made under defined contribution plan	$ 0.6	$ 0.4	$ 0.2
Defined Contribution Plan, Plan Name [Extensible List]	us-gaap:RetirementPlanNameOtherMember	us-gaap:RetirementPlanNameOtherMember

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, 2021	Dec. 31, 2020	Dec. 31, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	3,642,021	3,124,572	20,086,140
Options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	3,620,180	2,993,855	1,337,501
Restricted stock awards granted and not purchased
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	0	4,195	4,195
Unvested restricted shares
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	21,841	126,522	302,211
Redeemable convertible preferred stock (on an as-converted basis)
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	0	0	18,442,233

Net Loss Per Share Attributable to Common Stockholders - Reconciliation of Numerator and Denominator Used in Calculation of Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Numerator
Net loss	$ (97,263)	$ (41,533)	$ (631)
Less: accretion to redemption value and dividends on redeemable convertible preferred shares	0	0	(6,225)
Net loss attributable to common stockholders	$ (97,263)	$ (41,533)	$ (6,856)
Weighted-average common shares outstanding used to calculate net loss per share attributable to common stockholders:
Basic (in shares)	35,846,421	21,344,236	1,623,358
Diluted (in shares)	35,846,421	21,344,236	1,623,358
Net loss per share, attributable to common stockholders:
Basic (in dollars per share)	$ (2.71)	$ (1.95)	$ (4.22)
Diluted (in dollars per share)	$ (2.71)	$ (1.95)	$ (4.22)