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Document and Entity Information - shares	6 Months Ended
Document and Entity Information - shares	Jun. 30, 2020	Aug. 07, 2020
Cover [Abstract]
Amendment Flag	false
Document Type	10-Q
Document Period End Date	Jun. 30, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2
Entity Registrant Name	PLIANT THERAPEUTICS, INC.
Entity Central Index Key	0001746473
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		35,444,025
Entity Shell Company	false
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Trading Symbol	PLRX
Title of 12(b) Security	Common Stock, par value $0.0001 per share
Security Exchange Name	NASDAQ
Entity File Number	001-39303
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	47-4272481
Entity Address, Address Line One	260 Littlefield Avenue
Entity Address, City or Town	South San Francisco
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94080
City Area Code	650
Local Phone Number	481-6770
Document Quarterly Report	true
Document Transition Report	false

Condensed Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Current assets
Cash and cash equivalents	$ 178,461	$ 85,807
Short-term investments	134,007	16,966
Accounts receivable	3,599	7,052
Tax credit receivable	83	333
Prepaid expenses and other current assets	8,173	1,742
Total current assets	324,323	111,900
Property and equipment, net	4,029	4,079
Other non-current assets	451	3,085
Total assets	328,803	119,064
Current liabilities
Accounts payable	2,483	1,250
Accrued liabilities (Note 5)	9,553	6,922
Total current liabilities	12,036	8,172
Other long-term liabilities (Note 5)	951	912
Total liabilities	12,987	9,084
Commitments and Contingencies (Note 13)
Stockholders’ equity (deficit)
Common stock, $0.0001 par value; 300,000,000 and 181,000,000 shares authorized at June 30, 2020 and December 31, 2019; and 35,427,199 and 1,846,024 shares issued and outstanding at June 30, 2020 and December 31, 2019, respectively;	3	1
Additional paid-in capital	398,110
Accumulated deficit	(82,267)	(76,295)
Accumulated other comprehensive loss	(30)	(1)
Total stockholders’ equity (deficit)	315,816	(76,295)
Total liabilities, redeemable convertible preferred stock and stockholders’ equity (deficit)	$ 328,803	119,064
Series A Redeemable Convertible Preferred Stock
Current liabilities
Redeemable convertible preferred stock value		62,468
Series B Redeemable Convertible Preferred Stock
Current liabilities
Redeemable convertible preferred stock value		75,860
Series C Redeemable Convertible Preferred Stock
Current liabilities
Redeemable convertible preferred stock value		$ 47,947

Condensed Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Preferred stock, par value	$ 0.0001		$ 0.0001
Preferred stock, shares authorized	10,000,000		0
Preferred stock, shares issued	0		0
Preferred stock, shares outstanding	0		0
Common stock, par value	$ 0.0001		$ 0.0001
Common stock, shares authorized	300,000,000		181,000,000
Common stock, shares issued	35,427,199		1,846,024
Common stock, shares outstanding	35,427,199		1,846,024
Series A Redeemable Convertible Preferred Stock
Preferred stock, par value	$ 0.0001		$ 0.0001
Preferred stock, shares authorized	0		56,000,000
Preferred stock, shares issued	0		56,000,000
Preferred stock, shares outstanding	0	56,000,000	56,000,000	56,000,000	56,000,000	56,000,000
Preferred stock. aggregate liquidation preference	$ 0		$ 62,468
Series B Redeemable Convertible Preferred Stock
Preferred stock, par value	$ 0.0001		$ 0.0001
Preferred stock, shares authorized	0		49,501,221
Preferred stock, shares issued	0		49,501,221
Preferred stock, shares outstanding	0	49,501,221	49,501,221	49,501,221	49,501,221	49,501,221
Preferred stock. aggregate liquidation preference	$ 0		$ 75,860
Series C Redeemable Convertible Preferred Stock
Preferred stock, par value	$ 0.0001		$ 0.0001
Preferred stock, shares authorized	0		44,000,000
Preferred stock, shares issued	0		26,360,745
Preferred stock, shares outstanding	0	54,888,058	26,360,745
Preferred stock. aggregate liquidation preference	$ 0		$ 47,947

Condensed Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Statement [Abstract]
Revenue — related party	$ 3,600		$ 32,538
Operating expenses:
Research and development	(17,536)	$ (13,098)	(31,455)	$ (24,847)
General and administrative	(3,040)	(2,643)	(7,051)	(5,244)
Total operating expenses	(20,576)	(15,741)	(38,506)	(30,091)
Loss from operations	(16,976)	(15,741)	(5,968)	(30,091)
Interest income	111	240	320	553
Other expense, net	(136)	(21)	(324)	(7)
Net loss	(17,001)	(15,522)	(5,972)	(29,545)
Accretion to redemption value and cumulative dividends on redeemable convertible preferred stock		(1,359)		(2,703)
Net loss attributable to common stockholders	$ (17,001)	$ (16,881)	$ (5,972)	$ (32,248)
Net loss per share, attributable to common stockholders:
Basic	$ (1.39)	$ (10.82)	$ (0.85)	$ (21.70)
Diluted	$ (1.39)	$ (10.82)	$ (0.85)	$ (21.70)
Shares used in computing net loss per share attributable to common stockholders:
Basic	12,253,943	1,559,942	7,062,780	1,486,109
Diluted	12,253,943	1,559,942	7,062,780	1,486,109
Comprehensive loss:
Net loss	$ (17,001)	$ (15,522)	$ (5,972)	$ (29,545)
Net unrealized (loss) gain on short-term investments	(89)	8	(29)	11
Total other comprehensive (loss) income	(89)	8	(29)	11
Comprehensive loss	$ (17,090)	$ (15,514)	$ (6,001)	$ (29,534)

Condensed Statements of Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Initial Public Offering	Private Placement	Series A Redeemable Convertible Preferred Stock	Series B Redeemable Convertible Preferred Stock	Series C Redeemable Convertible Preferred Stock	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 Gain (Loss)	Accumulated Deficit
Beginning balance at Dec. 31, 2018	$ (71,469)						$ 1							$ (71,470)
Beginning balance, shares at Dec. 31, 2018				56,000,000	49,501,221
Beginning balance at Dec. 31, 2018				$ 61,516	$ 70,587
Beginning balance, shares at Dec. 31, 2018							1,363,000
Vesting of founders’ common stock and restricted stock awards	8									$ 8
Vesting of founders’ common stock and restricted stock awards, shares							126,057
Accretion to redemption value and cumulative dividends on redeemable convertible preferred stock					$ 1,344
Accretion to redemption value and cumulative dividends on redeemable convertible preferred stock	(1,344)									(320)				(1,024)
Stock-based compensation expense	312									312
Net unrealized gain (loss) on short-term investments	3												$ 3
Net income (loss)	(14,023)													(14,023)
Ending balance at Mar. 31, 2019	(86,513)						$ 1						3	(86,517)
Ending balance, shares at Mar. 31, 2019				56,000,000	49,501,221
Ending balance at Mar. 31, 2019				$ 61,516	$ 71,931
Ending balance, shares at Mar. 31, 2019							1,489,057
Beginning balance at Dec. 31, 2018	(71,469)						$ 1							(71,470)
Beginning balance, shares at Dec. 31, 2018				56,000,000	49,501,221
Beginning balance at Dec. 31, 2018				$ 61,516	$ 70,587
Beginning balance, shares at Dec. 31, 2018							1,363,000
Net unrealized gain (loss) on short-term investments	11
Net income (loss)	(29,545)
Ending balance at Jun. 30, 2019	(102,739)						$ 1						11	(102,751)
Ending balance, shares at Jun. 30, 2019				56,000,000	49,501,221
Ending balance at Jun. 30, 2019				$ 61,516	$ 73,290
Ending balance, shares at Jun. 30, 2019							1,650,360
Beginning balance at Mar. 31, 2019	(86,513)						$ 1						3	(86,517)
Beginning balance, shares at Mar. 31, 2019				56,000,000	49,501,221
Beginning balance at Mar. 31, 2019				$ 61,516	$ 71,931
Beginning balance, shares at Mar. 31, 2019							1,489,057
Vesting of founders’ common stock and restricted stock awards	9									9
Vesting of founders’ common stock and restricted stock awards, shares							139,363
Option exercises	132									132
Option exercises, shares							21,940
Accretion to redemption value and cumulative dividends on redeemable convertible preferred stock					$ 1,359
Accretion to redemption value and cumulative dividends on redeemable convertible preferred stock	(1,359)									(647)				(712)
Stock-based compensation expense	506									506
Net unrealized gain (loss) on short-term investments	8												8
Net income (loss)	(15,522)													(15,522)
Ending balance at Jun. 30, 2019	(102,739)						$ 1						11	(102,751)
Ending balance, shares at Jun. 30, 2019				56,000,000	49,501,221
Ending balance at Jun. 30, 2019				$ 61,516	$ 73,290
Ending balance, shares at Jun. 30, 2019							1,650,360
Beginning balance at Dec. 31, 2019	$ (76,295)						$ 1						(1)	(76,295)
Beginning balance, shares at Dec. 31, 2019	0			56,000,000	49,501,221	26,360,745
Beginning balance at Dec. 31, 2019				$ 62,468	$ 75,860	$ 47,947
Beginning balance, shares at Dec. 31, 2019	1,846,024						1,846,024
Issuance of Series C redeemable preferred stock, shares						28,527,313
Issuance of Series C redeemable preferred stock						$ 52,038
Vesting of founders’ common stock and restricted stock awards	$ 4									4
Vesting of founders’ common stock and restricted stock awards, shares							52,093
Option exercises	26									26
Option exercises, shares							8,252
Stock-based compensation expense	425									425
Net unrealized gain (loss) on short-term investments	60												60
Net income (loss)	11,029													11,029
Ending balance at Mar. 31, 2020	(64,751)						$ 1			455			59	(65,266)
Ending balance, shares at Mar. 31, 2020				56,000,000	49,501,221	54,888,058
Ending balance at Mar. 31, 2020				$ 62,468	$ 75,860	$ 99,985
Ending balance, shares at Mar. 31, 2020							1,906,349
Beginning balance at Dec. 31, 2019	$ (76,295)						$ 1						(1)	(76,295)
Beginning balance, shares at Dec. 31, 2019	0			56,000,000	49,501,221	26,360,745
Beginning balance at Dec. 31, 2019				$ 62,468	$ 75,860	$ 47,947
Beginning balance, shares at Dec. 31, 2019	1,846,024						1,846,024
Net unrealized gain (loss) on short-term investments	$ (29)
Net income (loss)	(5,972)
Ending balance at Jun. 30, 2020	$ 315,816						$ 3			398,110			(30)	(82,267)
Ending balance, shares at Jun. 30, 2020	0			0	0	0
Ending balance, shares at Jun. 30, 2020	35,427,199						35,427,199
Beginning balance at Mar. 31, 2020	$ (64,751)						$ 1			455			59	(65,266)
Beginning balance, shares at Mar. 31, 2020				56,000,000	49,501,221	54,888,058
Beginning balance at Mar. 31, 2020				$ 62,468	$ 75,860	$ 99,985
Beginning balance, shares at Mar. 31, 2020							1,906,349
Issuance of common/preferred stock		$ 148,400	$ 10,000					$ 1			$ 148,399	$ 10,000
Issuance of common/preferred stock, shares								10,350,000	625,000
Vesting of founders’ common stock and restricted stock awards	1									1
Vesting of founders’ common stock and restricted stock awards, shares							40,102
Option exercises	177									177
Option exercises, shares							73,719
Conversion of Series A, B, Cconvertible preferred stock tocommon stock	238,293						$ 1			238,292
Conversion of Series A, B, C convertible preferred stock to common stock, 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)	$ (99,985)
Conversion of Series A, B, C convertible preferred stock to common stock, shares							22,432,029
Stock-based compensation expense	786									786
Net unrealized gain (loss) on short-term investments	(89)												(89)
Net income (loss)	(17,001)													(17,001)
Ending balance at Jun. 30, 2020	$ 315,816						$ 3			$ 398,110			$ (30)	$ (82,267)
Ending balance, shares at Jun. 30, 2020	0			0	0	0
Ending balance, shares at Jun. 30, 2020	35,427,199						35,427,199

Condensed Statements of Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical) $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($)
Series C Redeemable Convertible Preferred Stock
Redeemable preferred stock issuance costs	$ 167

Condensed Statements of Cash Flows - USD ($)	6 Months Ended
Condensed Statements of Cash Flows - USD ($)	Jun. 30, 2020	Jun. 30, 2019
Cash flows from operating activities
Net loss	$ (5,972,000)	$ (29,545,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation expense	633,000	536,000
Stock-based compensation expense	1,211,000	818,000
Changes in operating assets and liabilities:
Tax credit receivable	250,000	42,000
Accounts receivable	3,453,000
Prepaid expenses and other current assets	(6,431,000)	(196,000)
Other non-current assets	(70,000)
Accounts payable	675,000	1,815,000
Accrued liabilities	1,249,000	1,871,000
Other long-term liabilities	8,000	41,000
Net cash used in operating activities	(4,994,000)	(24,618,000)
Cash flows from investing activities
Purchase of short-term investments	(141,035,000)	(32,762,000)
Maturity of short-term investments	23,997,000	11,171,000
Accretion of short-term investments	(32,000)	(174,000)
Purchase of property and equipment	(622,000)	(732,000)
Net cash used in investing activities	(117,692,000)	(22,497,000)
Cash flows from financing activities
Proceeds from issuance of common stock upon initial public offering, net of issuance costs	153,119,000
Proceeds from issuance of common stock upon completion of private placement	10,000,000
Proceeds from exercise of stock options	202,000
Proceeds from issuance of restricted common stock		132,000
Payment of deferred offering costs		(1,030,000)
Net cash provided by/(used) in financing activities	215,340,000	(898,000)
Net increase/(decrease) in cash and cash equivalents	92,654,000	(48,013,000)
Cash and cash equivalents at beginning of period	85,807,000	60,949,000
Cash and cash equivalents at end of period	178,461,000	12,936,000
Supplemental disclosures of noncash investing and financing activities:
Purchase of property and equipment in accounts payable and accrued liabilities	121,000	30,000
Reclassification of restricted stock awards from liabilities to common stock upon vesting	5,000	17,000
Accretion to redemption value and cumulative dividends on redeemable convertible preferred stock		2,703,000
Deferred offering costs in accounts payable and accrued liabilities	2,245,000	1,347,000
Net unrealized (loss) gain on short-term investments	(29,000)	$ 11,000
Series C Preferred Stock [Member]
Cash flows from financing activities
Proceeds from issuance of Series C preferred stock, net of issuance costs	$ 52,019,000

Organization and Description of Business

6 Months Ended

Jun. 30, 2020

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Organization and Description of Business

1. Organization and Description of Business

Pliant Therapeutics, Inc. (the “Company”) 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-ß. 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 will receive 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 Preferred Stock were proportionately reduced and the respective conversion prices were proportionately increased. As of June 30, 2020, all outstanding preferred stock have been converted into common stock.

Initial Public Offering

On June 3, 2019, the Company’s registration statement on Form S-1 was declared effective by the United States Securities and Exchange Commission (“SEC”), for its initial public offering (“IPO”) of its common stock. The Company’s shares of common stock started trading on the Nasdaq Select Global Market on June 3, 2020 and the transaction closed on June 5, 2020. In connection with the IPO, the Company sold an aggregate of 10,350,000 shares of common stock, which included 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 $148.4 million, net of underwriting discounts, commissions and offering expenses of $5.6 million, of which $2.6 million were paid in 2019 and $0.9 million paid in the current year. 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 (“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 (Note 6).

Summary of Significant Accounting Policies

6 Months Ended

Jun. 30, 2020

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2. 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”).

The accompanying condensed balance sheet as of June 30, 2020, condensed statements of operations and comprehensive (loss) income, condensed statements of cash flows, and the condensed statements of convertible preferred shares and shareholders’ (deficit) equity for the three and six months ended June 30, 2020 and 2019, are unaudited. The balance sheet as of December 31, 2019 was derived from audited financial statements as of and for the year ended December 31, 2019. The unaudited interim condensed financial statements have been prepared on the same basis as the audited annual financial statements as of and for the year ended December 31, 2019, and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary for the fair statement of the Company’s financial position as of June 30, 2020, and the results of its operations and its cash flows for the three and six months ended June 30, 2020 and 2019. The financial data and other information disclosed in these notes related to the three and six months ended June 30, 2020 and 2019, are also unaudited.

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 as of and during the reporting period. The Company bases its estimates and assumptions on historical experience when available and on various factors that it believes to be reasonable under the circumstances. Significant estimates and assumptions reflected in these financial statements include, but are not limited to, useful lives assigned to property and equipment, the fair values of common and redeemable convertible preferred stock, stock-based compensation expense, accruals for research and development costs, income taxes and uncertain tax positions. The Company assesses estimates on an ongoing basis; however, actual results could materially differ from those estimates.

Revenue Recognition

The Company accounts for its total revenue under Accounting Standards Update or ASU, ASU 2014-09, Topic 606 Revenue from Contracts with Customers (“Topic 606”), which was adopted by the Company using the full retrospective transition method. ASU 2014-09 provides a single, comprehensive revenue recognition model for all contracts with customers. This standard contains principles for the determination of the measurement of revenue and the timing of when such revenue is recognized. Revenue recognition will reflect the transfer of goods or services to customers at an amount that is expected to be earned in exchange for those goods or services. Subsequently, the FASB has issued the following guidance to amend ASU 2014-09: ASU No. 2015-14, Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date; ASU No. 2016-08, Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations (Reporting Revenue Gross versus Net); ASU No. 2016-10, Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing; ASU No. 2016-12, Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients; and ASU No. 2016-20, Technical Corrections and Improvements to Topic 606, which clarifies narrow aspects of Topic 606 or corrects unintended application of the guidance. The Company adopted ASU No. 2015-14, ASU No. 2016-08, ASU No. 2016-10, ASU No. 2016-12, and ASU No. 2016-20 with ASU No. 2014-09, which are referred to collectively as the “Topic 606”.

The FASB issued ASU No. 2018-18, “Collaborative Arrangements (Topic 808)” issued in November 2018. The Company assessed and concluded that they are not under Topic 808 and as the Novartis Agreement is not considered a collaboration under its provisions.

To date all revenue has been generated from the Company’s Collaboration and License Agreement with Novartis (the “Novartis Agreement”).

The Company’s revenue is generated solely from the Novartis Agreement. The Company’s licensing agreement includes upfront signing fees, cost reimbursements, research and development services, milestone payments and royalties on future licensee’s product sales. The Company has both fixed and variable consideration. Non-refundable upfront fees are considered fixed, while funding of research and development activities and milestone payments are identified as variable consideration. 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. A contract asset is 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). Receivables cannot be netted against contract liabilities and are presented separately from contract assets. Contract assets and contract liabilities are netted at the contract level and are then aggregated and presented separately each reporting period.

In determining the appropriate amount of revenue to be recognized as the Company fulfills its obligations under its agreements, the Company performs the following steps: (i) identification of the contract with a customer; (ii) identification of the performance obligations in the contract; (iii) determination of the transaction price; (iv) allocation of the transaction price to the performance obligations in the contract; and (v) recognition of revenue when (or as) we satisfy each performance obligation.

A performance obligation is a promise in a contract to transfer a distinct good or service to the customer. The Company’s performance obligations include providing the worldwide license rights to compound PLN-1474, provide research and development services for PLN-1474 through Phase 1 of its development and provide research and development services on initial candidate targets, which services are combined with a non-exclusive license to the initial candidate targets. The Company concluded that the worldwide license was distinct because the customer can benefit from the license on its own or together with other resources that are readily available, and the research and development services are not transformative in nature. The Company concluded the research and development services on initial candidate targets were not distinct from a non-exclusive license for the initial candidate targets, primarily as a result of (i) Pliant being unable to benefit on its own or together with other resources that are readily available as the license and (ii) the research and development services, including manufacturing in support of such services, were expected to significantly modify the initial license. Therefore, the promised goods and services were considered a single performance obligation. Significant management judgment is required in the identification of performance obligations and to determine the level of effort required under an arrangement and the period over which the Company expects to complete our performance obligations under the arrangement. If the Company cannot reasonably estimate when the performance obligations either are completed or become inconsequential, then revenue recognition is deferred until the Company can reasonably make such estimates. The Company estimates the transaction price and records revenue in the amount for which it is probable that a significant reversal of cumulative revenue recognized will not occur. At the end of each subsequent reporting period, we re-evaluate the estimated variable consideration included in the transaction price and any related constraint, and if necessary, adjusts its estimate of the overall transaction price. Revenue is then recognized over the remaining estimated period of performance using the cumulative catch-up method. The estimated period of performance and project costs are reviewed quarterly and adjusted, as needed, to reflect the Company’s current assumptions regarding the timing of our deliverables.

As part of the accounting for these arrangements, the Company must develop assumptions that require judgment to determine the stand-alone selling price of each performance obligation identified in the contract. The Company has never sold the performance obligations separately; therefore, an observable stand-alone selling price does not exist. Accordingly, the Company estimates a stand-alone selling price through maximizing the use of observable inputs such as market data, project cost estimates, and targeted margins. The Company determined that each of the performance obligations is priced and delivered at the stand-alone selling price. Therefore, no reallocations are needed since there is no material right and the license and services are provided at the stand-alone selling price.

During the three and six months ended June 30, 2020, the entirety of the Company’s revenue—related party is related to the Collaboration and License Agreement with Novartis. The Company did not have any prior revenue agreements and did not recognize revenue during the three and six months ended June 30, 2019. Receivables from collaborations are typically unsecured and are concentrated in the biopharmaceutical industry. Accordingly, the Company may be exposed to credit risk generally associated with biopharmaceutical companies or specific to the Novartis Agreement. An allowance on the receivables will be recorded if circumstances indicate collection is doubtful for a particular receivables balance. To date, the Company has not experienced any losses related to these receivables.

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 and government notes. 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. 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 three and six months ended June 30, 2020, Novartis accounted for 100% of the Company’s revenue—related party 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 and United States (“U.S.”) government agency securities and are stated at fair value.

Short-Term Investments

The Company’s short-term investments consist of U.S. Treasury securities and U.S. government agency securities with remaining maturities beyond three months at the date of purchase and one year or less from the balance sheet date. As of June 30, 2020 and December 31, 2019, all of the Company’s short-term investments were classified as available-for-sale and were carried at fair market value. The unrealized losses on the Company’s available-for-sale securities are recorded in “other comprehensive income and losses” (“OCI”) in the statements of operations and comprehensive (loss) income. 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) income and a new cost basis in the short-term investment will be established. As of June 30, 2020, the Company had not recorded any impairment related to other-than-temporary declines in the fair value of short-term investments.

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) income. Repairs and maintenance are expensed as incurred.

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 three and six months ended June 30, 2020 and 2019.

Redeemable Convertible Preferred Stock

The Company classified redeemable convertible preferred stock outside of stockholders’ deficit because, upon the occurrence of certain change in control events that are outside the Company’s control, including liquidation, sale or transfer of the Company’s assets, holders of the redeemable convertible preferred stock can cause 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 require 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 occur, for example changes in fair value of preferred stock, and adjusts 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 are 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 requires bifurcation. All preferred stock was automatically converted into common stock upon the Company’s IPO in June 2020.

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 product 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. The Company estimates these expenses based on discussions with internal management personnel and external service providers as to the progress or stage of completion of services and the contracted fees to be paid for such services. 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 over the time when 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.

Tax Credit Receivable

The Company was eligible for federal and California research and development credits for its research and development activities performed within the United States and California, respectively. The credits are generally available to offset federal and California income tax liabilities. Starting in the fourth quarter of 2019, the Company was no longer eligible for federal and California research development credits as it generated revenue during the year. The Company, however, is still eligible for future federal research and development credits for its research and development activities performed within the United States and California.

Stock-Based Compensation

The Company’s stock-based equity awards include restricted stock awards and stock options that are granted to employees and consultants and accounted at fair value on the award grant date. Stock-based compensation expense is recognized over the awards’ vesting period on a straight-line basis and recorded as either research and development or general and administrative expenses in the statements of operations and comprehensive (loss) income 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 based on the weighted-average vesting term of the awards and the contract period, or simplified method.

•

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, we will continue to apply this process 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. After our IPO, we will use our stock price traded on NASAQ to determine its fair value.

Deferred Offering Costs

Deferred offering costs, consisting of direct legal, accounting, filing and other fees directly related to the Company’s IPO were capitalized and reclassified to additional paid in capital upon completion of the IPO. The Company deferred $2.7 million as of December 31, 2019, which is recorded as other non-current assets in the Balance Sheets.

Leases and Rent Expense

The Company records rent expense on a straight-line basis over the life of the lease. In cases where there is a free rent period or future fixed rent escalations, the Company records a deferred rent liability. Additionally, the receipt of any lease incentives is recorded as a deferred rent liability which is amortized over the lease term as a reduction of rent expense. Building improvements made with the lease incentives or tenant allowances are capitalized as leasehold improvements and included in property and equipment, net in the Balance Sheets.

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. 740-10, Accounting for Uncertainty in 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) Income

Comprehensive (loss) income includes net (loss) income as well as other changes in stockholders’ deficit that result from transactions and economic events other than those with stockholders. For the three and six months ended June 30, 2020, the Company had a $89,000 and a $29,000 net unrealized loss on short-term investments, respectively. For the three and six months ended June 30, 2019, the Company had a $8,000 and a $11,000 net unrealized gain on short-term investments, respectively.

Net (Loss) Income Per Share

Basic net (loss) income per share is computed by dividing net (loss) income attributed to common stockholders by the weighted-average number of shares of common stock outstanding during the period. Diluted net (loss) income 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) income per share attributable to common stockholders is calculated using the two-class method, which is based on an earnings allocation formula that determines net (loss) income per share for the Company’s common stockholders and holders of participating securities. The holders of preferred stock are 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) 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) 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) income per share in the periods in which a net loss is recorded.

Diluted net (loss) income per share is computed using the more dilutive of (a) the two-class method or (b) the as-converted method. The Company allocates 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) 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 income per share if their effect is antidilutive. In periods in which the Company reports a net loss income attributable to common stockholders, diluted net loss income per share attributable to common stockholders is generally the same as basic net loss income 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 for the three and six months ended June 30, 2020 and 2019.

Recently Issued Accounting Pronouncements

In February 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standard Update (“ASU”) No. 2016-02, Leases (“Topic 842”), which requires an entity to recognize assets and liabilities arising from a lease for both financing and operating leases. For public entities, ASU No. 2016-02 is effective for fiscal years beginning after December 15, 2018. The ASU will also require new qualitative and quantitative disclosures to help investors and other financial statement users better understand the amount, timing, and uncertainty of cash flows arising from leases. As a result of the Company having elected the extended transition period for complying with new or revised accounting standards pursuant to Section 107(b) of the JOBS Act, ASU No. 2016-02 is effective for the Company in the fiscal years beginning after December 15, 2022, with early adoption permitted. The Company is currently in the process of evaluating the impact of the adoption of ASU No. 2016-02 on the Company’s financial statements.

In December 2019, the FASB issued Accounting Standards Update 2019-12 (“ASU 2019-12”), Income Taxes (topic 740): Simplifying the Accounting for Income Taxes. The amendments in ASU 2019-12 simplify the accounting for income taxes by removing certain exceptions to the general principles in Topic 740. The amendments also improve consistent application of and simplify GAAP for other areas of Topic 740 by clarifying and amending existing guidance. ASU 2019-12 removes the exception for intraperiod tax allocations when there is a loss from continuing operations and income or a gain from other items (other comprehensive income). ASU 2019-12 is effective beginning on January 1, 2021. Early adoption of the amendments is permitted. The Company has early adopted the new standard effective January 1, 2020, and its adoption did not have a material impact on our condensed financial statements.

Financial Instruments

6 Months Ended

Jun. 30, 2020

Fair Value Disclosures [Abstract]

Financial Instruments

3. Financial Instruments

The Company’s short-term investments in U.S. Treasury and U.S. government agency securities have been classified and accounted for as available-for-sale. The Company classifies its U.S. Treasury and U.S. government agency securities as Level 2 based on each instrument’s underlying contractual maturity date. Unrealized gains and losses on U.S. Treasury and U.S. government agency securities classified as available-for-sale are recognized in other comprehensive (loss) income.

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 and U.S. government agency 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 and U.S. Treasury 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.

The following tables show the Company’s cash and cash equivalents, Money Market Funds and short-term investments by significant investment category as of June 30, 2020 and December 31, 2019 (in thousands):

	As of June 30, 2020
	Adjusted Cost		Unrealized Gains		Unrealized Losses			Market Value
Level 1:
Money Market Funds	$	126,191	$	—	$	—		$	126,191
Level 2:
U.S. Treasury securities included in short-term investments		85,706		4		(13	)		85,697
U.S. government agency securities included in cash and cash equivalents and short-term investments		62,051		2		(23	)		62,030
Total financial assets	$	273,948	$	6	$	(36	)	$	273,918

	As of December 31, 2019
	Adjusted Cost		Unrealized Gains		Unrealized Losses			Market Value
Level 1:
Money Market Funds	$	16,366	$	—	$	—		$	16,366
Level 2:
U.S. Treasury securities included in short-term investments		2,998		—		—			2,998
U.S. government agency securities included in short-term investments		34,204		1		(2	)		34,203
Total financial assets	$	53,568	$	1	$	(2	)	$	53,567

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.

There were no liabilities measured at fair value on a recurring basis as of June 30, 20202 and December 31, 2019. There have been no transfers between fair value measurement levels during the six months ended June 30, 2020 and 2019. In addition, there were no assets or liabilities measured at fair value on a non-recurring basis as of June 30, 2020 and December 31, 2019.

As of June 30, 2020, the Company had not recorded any impairment related to other-than-temporary declines in the fair value of short-term investments. 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.

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

- 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

6 Months Ended

Jun. 30, 2020

Property Plant And Equipment [Abstract]

Property and Equipment, net

4. Property and Equipment, net

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

	As of June 30, 2020			As of December 31, 2019
Computer equipment and software	$	22		$	22
Laboratory equipment		6,078			5,580
Leasehold improvements		701			657
Construction-in-progress		49			8
Total property and equipment, gross		6,850			6,267
Less: Accumulated depreciation		(2,821	)		(2,188	)
Total property and equipment, net	$	4,029		$	4,079

Depreciation expense for the three months ended June 30, 2020 and 2019 was $0.3 million and $0.2 million, respectively. Depreciation expense for the six months ended June 30, 2020 and 2019 was $0.6 million and $0.5 million, respectively.

Accrued Liabilities and Other Long-Term Liabilities

6 Months Ended

Jun. 30, 2020

Accrued Liabilities And Other Liabilities [Abstract]

Accrued Liabilities and Other Long-Term Liabilities

5. Accrued Liabilities and Other Long-Term Liabilities

Accrued Liabilities

Accrued liabilities consisted of the following (in thousands):

	As of June 30, 2020		As of December 31, 2019
Accrued compensation and benefits	$	2,003	$	2,971
Accrued research and development expenses		5,373		2,624
Other accrued liabilities		2,147		1,263
Deferred rent		30		64
Total accrued liabilities	$	9,553	$	6,922

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):

	As of June 30, 2020		As of December 31, 2019
Deferred rent	$	540	$	458
Leasehold incentive obligation		404		444
Other liabilities — deposits		7		10
Total other long-term liabilities	$	951	$	912

Novartis Agreement

6 Months Ended

Jun. 30, 2020

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Novartis Agreement

6. Novartis Agreement

In October 2019, the Company entered into a Collaboration and License Agreement with Novartis (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 α_vß₁, currently being developed for the treatment of liver fibrosis associated with nonalcoholic steatohepatitis (“NASH”). In accordance with the Novartis Agreement, on December 7, 2019, Novartis paid to Pliant an upfront non-refundable license fee of $50.0 million for the worldwide exclusive license to PLN-1474.

Novartis will fund the Company’s research and development services for PLN-1474 through Phase 1 after which Novartis will assume responsibility for all future development, manufacturing and commercialization costs of PLN-1474. Novartis will also fund the research and development services associated with integrin research targets as outlined in the Novartis Agreement. The Company is scheduled to receive up to $19.6 million in funding for PLN-1474 development services through Phase 1 of its development, which is expected to go through 2020. The Company is initially obligated to perform research and development services on the integrin research targets for sixty days, and Novartis has the option to terminate the services with 60 days notification. Novartis has the option to continue the research and development services through 2022. If any of the targets achieves target validation and are deemed a research target, Novartis holds the rights to exercise its license options to obtain an exclusive license for those deemed research targets on a research target-by-research target basis by paying an option exercise fee for each target (up to three in total), including all license compounds that are the subject of the applicable research program. Novartis will also pay the Company a certain specified target validation fee of $4.0 million for each candidate target that achieves target validation and is deemed a research target, for up to three candidate targets. Upon exercise of an option, Novartis will be responsible for global clinical development and commercialization of each licensed research target.

Under the Novartis Agreement, the Company is eligible for developmental, regulatory and commercial milestone payments related to PLN-1474 and the integrin research targets of up to $416.0 million if defined development and commercialization milestones are achieved and tiered royalties ranging from the mid-single digits to low teens on product sales upon commercialization.

Upon execution of the Novartis Agreement, Pliant also entered into a Financing Side Letter with Novartis (the “Financing Side Letter”), whereby Novartis committed to provide up to $30.0 million in equity financing of which $20.0 million was satisfied by the issuance of 10,928,962 shares of Series C Redeemable Convertible Preferred Stock on December 19, 2019 and the remaining $10.0 million was satisfied by the issuance of shares of common stock through a concurrent private placement with the Company’s IPO. The Company determined that Novartis Agreement and the Financing Side Letter are separate agreements, they were not entered into for single commercial objective, the consideration in each agreement are tied to separate and different types of performance obligations and they are not considered a single performance obligation. The Series C Redeemable Preferred Stock was issued to Novartis at fair value of $1.83 per share in conjunction with its issuance to other investors at the same price. In addition, the contingent issuance of shares upon an Initial Public Offering would also be at fair value. Further, Novartis became a related party to the Company following its purchase of 10.9 million shares of our Series C Redeemable Convertible Stock on December 19, 2019, representing holdings of 6.1% and 7.4% of our outstanding shares of common stock on a fully diluted basis as of June 30, 2020 and December 31, 2019, respectively. See Notes 9 and 14 to these financial statements for additional information.

The Company evaluated the Novartis Agreement under the revenue standard Topic 606 and concluded that Novartis is a customer. The Company identified the following performance obligations at the inception of the contract.

•

Provide Novartis worldwide license rights to PLN-1474.

•

Provide research and development services for PLN-1474 through Phase 1 of its development.

•

Provide non-exclusive license rights to integrin research targets and research and development services on integrin research targets, together as a single performance obligation.

The Company determined the transaction price at inception of the Novartis Agreement is the $69.6 million consisting of the license fee of $50.0 million and research and development funding of $19.6 million payment to be allocated to the various performance obligations. The Novartis Agreement includes variable consideration for the funding of research and development services and potential future milestones and royalties that were contingent on future success factors for development programs. The Company used the “most likely” method to determine the variable consideration. None of the regulatory or development milestones were included in the transaction price. The Company will re-evaluate the transaction price in each reporting period as uncertain events are resolved or other changes in circumstances occur.

The Company considered the license to PLN-1474 as functional intellectual property, as when control of the license was transferred to Novartis at the inception of the Novartis Agreement, Novartis had the right to access its technology and it was functional. The Company determined the $50.0 million was the standalone selling price PLN-1474 license and was recognized as revenue when control of the license transferred to Novartis, which was at or near inception of the Novartis Agreement.

The Company estimated the standalone selling price of each research program based on internal and external costs to perform the research plus a reasonable profit margin. The total estimated cost of the research and development services reflects the nature of the services to be performed and the Company’s best estimate of the length of time required to perform the services. The Company selected an input method of costs incurred to measure progress toward complete satisfaction of its performance obligation to provide research and development services as such method faithfully depicts the Company’s performance in transferring control of the research and development service to Novartis. Changes in estimates of total internal and external costs expected to be incurred are recognized in the period of change as a cumulative catch-up adjustment. There have been no changes to the Company’s estimates to date.

During the three and six months ended June 30, 2020, the Company recognized revenue—related party of $3.6 million and $32.5 million, respectively. Revenue-related party for the three months ended June 30, 2020 consists of $3.6 million generated from research and development services performed during the period. Revenue-related party for the six months ended June 30, 2020, consists of $25.0 million of revenue from the achievement of the first patient dosing milestone of the Novartis agreement in the first quarter of 2020 and $7.5 million of revenue generated from research and development services performed during the six months ended June 30, 2020. The Company recognized no revenue during the three and six months ended June 30, 2019.

As of June 30,2020 and December 31, 2019, there is a receivable of $3.6 million and $7.1 million, respectively, related to the Novartis Agreement. There were no contract assets or contract liabilities as of June 30, 2020 and December 31, 2019.

License Agreements

6 Months Ended

Jun. 30, 2020

License Agreements [Abstract]

License Agreements

7. License Agreements

UC Regents

In August 2015, the Company entered into an exclusive, worldwide license agreement (the “UC Agreement”) with the Regents of the University of California (the “UC Regents”) relating to the use of certain patents and technology relating to α_vß₁ compound in fibrosis indications. Pursuant to the UC Agreement, the Company is obligated to (i) make a non-refundable upfront license fee payment of $0.4 million and annual license maintenance fee payments of $10,000 per year beginning on the first anniversary of the UC Agreement escalating to $25,000 per year thereafter (ii) make royalty payments to the UC Regents of 3% of net sales of a therapeutic licensed product or 1% of net sales of a method of use licensed product, subject to an annual minimum of $1.0 million, (iii) make milestone payments up to an aggregate of $18.2 million to the UC Regents upon the occurrence of certain events, (iv) make a milestone payment based on the number of outstanding shares and a price per share as defined in the UC Agreement within 30 days of the closing of an IPO or change of control, and (v) reimburse the UC Regents for prosecution and maintenance expenses of the licensed patents without limitation. As a result of the IPO on June 3, 2020, the Company made a $2.4 million milestone payment to the UC Regents. The Company will expense any payments for milestones to research and development expenses prior to receiving FDA approval for any of its product candidates. These costs will be capitalized when FDA approval is obtained for any products being selected for commercialization and amortized over the remaining life of the patent. If the Company sublicenses its rights under the UC Agreement, it is obligated to pay the UC Regents a percentage of the total gross proceeds received in consideration of the grant of the sublicense, which total amount would be first reduced by the aggregate amount of certain research and development related expense incurred by the Company.

The UC Agreement can be terminated at any time upon the material breach of contract terms by either party to the agreement. The Company has the right to terminate the agreement at any time upon providing written notice to the UC Regents. Unless terminated early, the UC Agreement will remain in effect from the effective date until the later of (i) the expiration or abandonment of the patent rights licensed under the UC Agreement, or (ii) ten years from the date of the first commercial sale of the first licensed product under the agreement.

Research Agreement

6 Months Ended

Jun. 30, 2020

Research And Development [Abstract]

Research Agreement

8. Research Agreement

Adimab Development and Option Agreement

In October 2018, the Company and Adimab LLC (“Adimab”) entered into a development and option agreement (the “Adimab Agreement”) for the discovery and optimization of proprietary antibodies as potential therapeutic product candidates. Under the Adimab Agreement, the Company 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.

Upon the Company’s selection of a target, the Company and Adimab will initiate a research plan and the discovery term begins. During the discovery term, Adimab will grant the Company a non-exclusive, non-sublicensable license under its technology with respect to the target, to research, design and preclinically develop and use antibodies that were modified or derived using Adimab technology, solely to evaluate such antibodies, perform the Company’s responsibilities under the research plan and use such antibodies for certain diagnostic purposes. The Company will also grant to Adimab a non-exclusive, non-sublicensable and non-transferable license with respect to the target under the Company’s technology that covers or relates to such target, solely to perform its responsibilities under the research plan during the discovery period. The Company is required to pay Adimab at 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.

Adimab granted the Company 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 twenty-four antibodies selected by the Company (the “Program Antibodies”) against specific biological targets (the “Commercialization Option”). Upon the exercise of a Commercialization Option, and payment of the applicable option fee to Adimab, Adimab will assign the patents that cover the Program Antibodies to Company. The Company will be required to use commercially reasonable efforts to develop, seek market approval of, and commercialize at least one antibody against the target covered by the Commercialization Option in specified markets upon the exercise of a Commercialization Option.

Pursuant to the Adimab Agreement, the Company is obligated to (i) make a nonrefundable upfront license fee payment for access to Adimab’s technology; (ii) pay Adimab at an agreed upon rate for each full-time employee (“FTE”) during the research period; (iii) make additional payments upon the Company making other research related elections; (iv) pay up to a dollar amount in the low double digit millions for the achievement of certain research and development milestones for each research target program which can vary by target type; (v) make royalty payments to Adimab on Company net sales of its products covered under the Adimab Agreement, subject to varying royalty payments on certain product types. Currently, no product types have been selected by the Company.

During the three and six months ended June 30, 2020, the Company recognized research and development expenses under the Adimab Agreement of $37,000 related to FTE costs.

During the three and six months ended June 30, 2019, the Company recognized research and development expense under the Adimab Agreement of $0.2 million and $0.3 million, related to the FTE costs.

Redeemable Convertible Preferred Stock

6 Months Ended

Jun. 30, 2020

Temporary Equity Disclosure [Abstract]

Redeemable Convertible Preferred Stock

9. Redeemable Convertible Preferred Stock

Under 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. As a result of the IPO in June 2020, in which all convertible preferred stock was converted into common shares of the Company, there was no outstanding redeemable convertible preferred stock as of June 30, 2020. The following is a summary of the Company’s redeemable convertible preferred stock as of December 31, 2019 (in thousands except share amounts):

	Preferred Shares Authorized		Shares Issued and Outstanding		Redemption Value/ Liquidation Preference		Carrying Value
Series A		56,000,000		56,000,000	$	62,468	$	62,468
Series B		49,501,221		49,501,221		75,860		75,860
Series C		44,000,000		26,360,745		47,947		47,947
		149,501,221		131,861,966	$	186,275	$	186,275

Series A Preferred

In August 2015, the Company entered into a Series A Preferred Stock Purchase Agreement (the “Series A Purchase Agreement”) pursuant to which it agreed to sell, and the purchasers agreed to purchase up to $45.0 million of Series A Redeemable Convertible Preferred Stock (“Series A Preferred”) in three anticipated tranches based on the achievement of defined performance milestones. The Series A Preferred stockholders may not assign the rights to purchase shares of Series A Preferred at any future milestone closing tranches separately without a transfer of already purchased shares. The Company determined that these future tranche obligations did not meet the definition of a freestanding financial instrument because, while separately exercisable, they were not legally detachable. Further, the Company determined that the embedded future tranche obligation did not require bifurcation for accounting purposes as it was clearly and closely related to the economic characteristics and risks of the Series A Preferred and would not meet the definition of a derivative on a standalone basis.

Under the Series A Purchase Agreement, as part of the initial closing, the Company issued 6.5 million shares of Series A Preferred at $1.00 per share in exchange for cash proceeds of $6.4 million and the conversion of convertible promissory notes in the amount of $0.1 million representing outstanding principal and accrued interest.

In April 2016, the Company issued 5.0 million shares of Series A Preferred at $1.00 per share in exchange for cash proceeds of $5.0 million in an additional closing of the first tranche. The final closing of the first tranche occurred in September of 2016, when the Company issued 5.0 million additional shares of Series A Preferred at $1.00 per share in exchange for cash proceeds of $5.0 million.

In February 2017, the Company issued 8.0 million shares of Series A Preferred at $1.00 per share in exchange for cash proceeds of $8.0 million in a closing of the second tranche.

In July 2017, the Company issued 12.0 million shares of Series A Preferred at $1.00 per share in exchange for cash proceeds of $12.0 million in an initial closing of the third tranche.

In January 2018, the Company issued 8.5 million shares of Series A Preferred at $1.00 per share in exchange for cash proceeds of $8.5 million in an additional closing of the third tranche.

In March 2018, based on the amendment to the Series A Purchase Agreement, the Company issued 11.0 million additional shares of Series A Preferred at $1.00 per share in exchange for cash proceeds of $11.0 million in the final closing of the third tranche.

Series B Preferred

In July 2018, the Company entered into a Series B Preferred Stock Purchase Agreement (the “Series B Purchase Agreement”) in which it agreed to sell, and the purchasers agreed to purchase, up to $70.0 million of Series B Redeemable Convertible Preferred Stock (“Series B Preferred”). Under the Series B Purchase Agreement, the Company initially issued 45.1 million shares of Series B Preferred at $1.3767 per share in exchange for cash proceeds of approximately $62.1 million.

In November 2018, the Company issued 4.4 million additional shares of Series B Preferred at $1.3767 per share in exchange for cash proceeds of approximately $6.0 million.

Series C Preferred

In December 2019, the Company entered into a Series C Preferred Stock Purchase Agreement (the “Series C Purchase Agreement”) in which it agreed to sell, and the purchasers agreed to purchase, up to $80.5 million of Series C Redeemable Convertible Preferred Stock (“Series C Preferred”). Under the Series C Purchase Agreement, the Company initially issued 26.4 million shares of Series C Preferred at $1.83 per share in exchange for aggregate cash proceeds of $48.2 million. Novartis purchased 10.9 million shares of this allotment of Series C Preferred at $1.83 per share for cash proceeds of $20.0 million. Novartis became a related party following its purchase of 10.9 million shares of our Series C Preferred. Novartis holdings represent of 6.1% and 7.4% of our outstanding shares of common stock on a fully diluted basis as of June 30, 2020 and December 31, 2019, respectively. See Note 14 for additional information.

In February 2020, the Company issued an additional 28.5 million additional shares of Series C Preferred at $1.83 per share in exchange for gross cash proceeds of $52.2 million and incurred $0.2 of issuance costs.

The Series A Preferred, Series B Preferred and Series C Preferred (collectively, the “Preferred Stock”) have the following rights and privileges:

Voting

Each holder of shares of Preferred Stock is entitled to the number of votes equal to the number of shares of common stock into which such shares could be converted and has voting rights and powers equal to the voting rights and powers of the common stock, and except as provided by law or by other provisions of the Company’s Certificate of Incorporation, as amended, shall vote together with the common stock as a single class on an as-converted basis on all matters as to which holders of common stock have the right to vote.

The holders of Series A Preferred, voting separately as a single class, are entitled to elect two members of the Company’s board of directors. At any time when at least 12.5 million shares of Series B Preferred are outstanding, the holders of Series B Preferred are entitled to elect one member of the Company’s board of directors. The holders of shares of common stock, voting separately as a single class, are entitled to elect one member of the Company’s board of directors. All remaining members of the Company’s board of directors are elected by the holders of the common stock and Preferred Stock voting together as a single class.

Conversion

Shares of the Preferred Stock are convertible at any time at the option of the holder into such number of shares as is determined by dividing the original issuance price by the conversion price in effect at the time. The conversion price is the original issuance price for each series of Preferred Stock, as adjusted for the 1-for-7.15 reverse stock split of the Common Stock. Following such adjustment, the per-share conversion price was $7.15 for Series A Preferred, $9.843405 for Series B Preferred and $13.0845 for Series C Preferred, subject to certain adjustments.

All outstanding shares of Preferred Stock converted to shares of common stock upon the completion of the Company’s IPO.

Dividends

The holders of Series A Preferred were originally entitled to receive cumulative dividends from their respective dates of issuance at the rate of 8.0% on their original issue price. In July 2018, in conjunction with the execution of the Series B Purchase Agreement, the Series A Preferred accreted dividends were cancelled.

Under the Series B Purchase Agreement, the holders of both shares of Series A and Series B Preferred are entitled to receive cumulative dividends commencing on July 10, 2018, the issuance date of Series B Preferred, at an annual rate of 8.0% on their original issuance price. The Series A Preferred and Series B Preferred dividends accrue from day-to-day, whether declared or not, and are payable only when and if declared by the Company’s board of directors. As such, the Company recorded accretion charges to adjust the carrying values of the Series A Preferred and Series B Preferred to their redemption values up until the date the Series C Purchase Agreement was executed. In December 2019, in conjunction with the execution of the Series C Purchase agreement, the Series A preferred and Series B preferred accreted dividends were cancelled.

Under the Series C Purchase Agreement, the holders of Series A, Series B and Series C Preferred are entitled to receive non-cumulative dividends commencing on December 19, 2019 at an annual rate of 8.0% on their original issuance price. The Series A, Series B and Series C Preferred dividends accrue from day-to-day, whether declared or not, and are payable only when and if declared by the Company’s board of directors. Since inception, the Company has never declared or paid any dividends.

Liquidation Preferences

The holders of all shares of preferred stock are entitled to receive dividends prior and in preference to any declaration or payment of any dividend on the common stock.

Upon liquidation, dissolution, or winding up of the Company or a deemed liquidation event as defined in the Company’s Certificate of Incorporation, the holders of shares of Series C and Series B Preferred Stock will receive, on a pari passu basis, a per share amount equal to the Series C purchase price of $1.83 (plus any declared but unpaid dividends) and equal to the original Series B purchase of $1.3767 (plus any declared but unpaid dividends), collectively (the “Series C and Series B Liquidation Preference”) or such amount per share as would have been payable had all shares of Series C and Series B had been converted into common stock immediately prior to such liquidation event. The payment of Series C and Series B Liquidation Preference is to be made before any payment made to the holders of Series A Preferred Stock and Common Stock. Thereafter, the Series A Preferred holders are entitled to receive their liquidation preference before any distributions are made to common stockholders, a per share amount equal to $1.00 (plus any declared but unpaid dividends) (the “Series A Liquidation Preference”) or such amount per share as would have been payable had all shares of Series A had been converted into common stock immediately prior to such liquidation event. After payments of the full liquidation preferences of the Series C and Series B Liquidation Preference and the Series A Liquidation Preference described above, any remaining assets of the Company shall be distributed to the holders of the common stock in proportion to the number of shares of common stock that they hold.

Redemption

The Series A Preferred were redeemable at any time on or after five years from August 19, 2015, the original issuance date of the 6.5 million shares of Series A Preferred, upon receipt of a written notice from the holders of a majority of the shares of Series A Preferred. The initial redemption price was the greater of (i) the Series A Preferred original issuance price per share, plus any accrued and unpaid dividends, whether or not declared by the board of directors, and (ii) the fair market value of Series A Preferred as mutually agreed upon by the Company and the holders of a majority of the shares of Series A Preferred then outstanding.

In July 2018, in conjunction with the execution of the Series B Preferred Purchase Agreement, the Series A Preferred redemption provision was amended as follows:

All outstanding shares of Preferred Stock shall be redeemed by the Company at a price equal to the original issuance price per share, plus any accrued and unpaid dividends, whether or not declared, together with any other dividends declared but unpaid in three annual installments commencing not more than sixty (60) days after receipt by the Company at any time on or after five years from the Series B Preferred original issuance date, July 10, 2018, a written notice from the holders of a majority of the shares of Preferred Stock.

The Company accounted for the changes in Series A Preferred redemption provision as a modification as there was no significant difference in Series A Preferred fair value before and after the modification.

In December 2019, in conjunction with the execution of the Series C Preferred Purchase Agreement, the Series A Preferred and Series B Preferred redemption provisions were modified as follows:

All outstanding shares of Preferred Stock shall be redeemed by the Company at a price equal to the original issuance price per share, plus any dividends declared but unpaid, in three annual installments commencing not more than sixty (60) days after receipt by the Company at any time on or after five years from the Series C Preferred original issuance date, December 19, 2019, a written notice from the holders of a majority of the shares of Preferred Stock.

The Company accounted for the changes in Series A Preferred redemption and Series B Preferred redemption provisions as a modification as there was no significant difference in Series A Preferred and Series B Preferred fair values before and after the modification.

Common Stock

6 Months Ended

Jun. 30, 2020

Equity [Abstract]

Common Stock

10. Common Stock

The voting, dividend, and liquidation rights of the holders of the common stock are subject to and qualified by the rights, powers, and preferences of the holders of the Preferred Stock. As of June 30, 2020 and December 31, 2019, the Company had 300,000,000 and 181,000,000 authorized shares of common stock, respectively, 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

	As of June 30, 2020		As of December 31, 2019
Conversion of redeemable convertible preferred stock		—		18,442,233
Exercises of outstanding stock option awards		2,529,999		1,337,501
Shares of common stock available for future grants under the 2015 Equity Incentive Plan, as amended		—		567,110
Shares of common stock available for future grants under the 2020 Equity Incentive Plan		4,200,000		—
Shares of common stock available for future issuance under the 2020 ESPP		700,000		—
Total shares reserved for future issuance		7,429,999		20,346,844

Founders’ Common Stock Awards

During 2015, the Company’s board of directors granted common stock awards to the Company’s founders in exchange for services provided to the Company. The purchase price of the common stock awards was the estimated fair value at the issuance date. The shares vest from one to four years and vesting could be accelerated upon a change in control. The vesting of certain performance-based grants of restricted stock awards were contingent upon the filing of an Investigational New Drug Application by the Company with the FDA.

If the holder of founders’ common stock award terminates their relationship with the Company during the vesting period, the Company may repurchase any unvested restricted common stock held by these individuals at their original purchase price. During the vesting term, holders of founders’ common stock awards are deemed to be common stockholders and have dividend and voting rights. The Company issued 745,244 shares of founders’ common stock during 2015. No founders’ common stock awards were granted in subsequent years. Total compensation expense was $25,000 for these founders’ common stock awards, which are recorded to operating expenses in the statements of operations over their respective vesting period. As of June 30, 2020 and December 31, 2019, all shares of founders’ common stock awards were fully vested.

Equity Incentive Plans and Stock-Based Compensation

6 Months Ended

Jun. 30, 2020

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Equity Incentive Plans and Stock-Based Compensation

11. Equity Incentive Plans and Stock-Based Compensation

In May 2020, the board of directors adopted the 2020 Stock Options and Incentive Plan, (the “2020 Plan”), which 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 for the purchase of up to 4.2 million shares of the Company’s common stock. In addition, to the extent that awards outstanding under the 2020 Plan or the 2015 Plan are cancelled, forfeited or held back upon exercise or settlement of an award to satisfy the exercise price or tax withholding, reacquired by the registrant prior to vesting, satisfied without any issuance of stock, expire or are otherwise terminated (other than by exercise) subsequent to May 2020, the shares of common stock reserved for issuance pursuant to such awards will become available for issuance as shares of common stock under the 2020 Plan. The 2020 Plan provides that an additional number of shares will automatically be added to the shares authorized for issuance under the 2020 Plan 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. As of June 30, 2020, all 4.2 million shares remained available for issuance under the Plan.

Options under the 2020 Plan may be granted for periods of up to 10 years and at prices no less than 100.0% of the estimated fair value of the shares on the date of grant as determined by the board of directors, provided, however, that the exercise price of an incentive stock option granted to a 10.0% shareholder shall not be less than 110.0% 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

In August 2015, the board of directors adopted the 2015 Equity Incentive Plan, as amended (the “2015 Plan”), which provides 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 for the purchase of up to 1.5 million shares of the Company’s common stock. In July 2018, the 2015 Plan was amended to increase the number of shares reserved thereunder by 1.0 million shares. In January 2019, the Company’s board of directors and stockholders voted to increase the number of shares reserved for issuance under the 2015 Equity Incentive Plan by 0.4 million shares. In March 2020, the Company’s board of directors and stockholders voted to increase the number of shares reserved for issuance under the 2015 Plan by 1.4 million shares. In May 2020, the board of directors voted to adopt the 2020 Plan and not to issue any further grants under the 2015 Plan. As of June 30, 2020, 2.5 million shares remain available for issuance only upon the exercise of outstanding stock options under the 2015 Plan.

Prior to the adoption of the 2020 Plan, options under the 2015 Plan may be granted for periods of up to 10 years and at prices no less than 100.0% of the estimated fair value of the shares on the date of grant as determined by the board of directors, provided, however, that the exercise price of an incentive stock option granted to a 10.0% shareholder shall not be less than 110.0% 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 Plan. The purchase price of the restricted common stock awards was the estimated fair value as determined by the 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 a common stock shareholder 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 June 30, 2020 and December 31, 2019, the Company recorded a liability included in accrued expenses and other liabilities of $16,000 and $22,000, respectively.

There have been no grants of restricted stock awards granted for the six months ended June 30, 2020 and 2019.

The following table summarizes restricted stock activity during the six months ended June 30, 2020:

	Number of Shares			Weighted- Average Grant Date fair value
Outstanding and unvested, as of December 31, 2019		302,211		$	1.51
Issued		—		$	—
Vested		(92,199	)	$	1.19
Repurchases		(12,121	)	$	1.22
Outstanding and unvested, as of June 30, 2020		197,891		$	1.70

The following table summarizes restricted stock activity during the six months ended June 30, 2019:

	Number of Shares			Weighted- Average Grant Date fair value
Outstanding and unvested, as of December 31, 2018		703,188		$	1.22
Issued		—		$	—
Vested		(225,551	)	$	1.01
Exercised		363		$	2.15
Repurchases		(3,671	)	$	2.15
Outstanding and unvested, as of June 30, 2019		474,329		$	1.22

Restricted stock awards of 4,195 shares with a weighted-average grant date fair value of $0.08 per share, were not purchased by the award holders as of June 30, 2020. As these shares of the restricted common stock awards were not issued, they are not included in the table above.

The aggregate fair value of restricted stock awards vested during the six months ended June 30, 2020 and 2019 was $109,000 and $219,000, respectively. Total intrinsic value of outstanding unvested restricted stock awards as of June 30, 2020 and December 31, 2019 was $6.4 million and $3.3 million, respectively.

Incentive Stock Options and Nonqualified Stock Options

Stock options issued under the 2015 Plan and to be issued under the 2020 Plan generally vest over a four-year period 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:

	Three Months Ended June 30,				Six Months Ended June 30,
	2020		2019		2020		2019
Expected volatility		—	79.37% - 82.15%		72.10% - 77.50%		78.50% - 82.55%
Risk-free interest rate		—	1.81% - 2.30%		0.52% - 0.82%		1.81% - 2.59%
Expected dividend		—		—		—		—
Expected term (in years)		—	5.81 - 6.08		5.38 - 6.75		5.00 - 6.08
Underlying common stock fair value		—		6.22		6.22		5.15

There have been no stock options granted under the 2015 Plan or the 2020 Plan during the three months ended June 30, 2020.

A summary of option activity under the 2015 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, 2019		1,337,501		$	3.22		9.18	$	5,157
Granted		1,275,202		$	6.22
Exercised		(81,996	)	$	2.47
Forfeited		(708	)	$	2.08
Outstanding as of June 30, 2020		2,529,999		$	4.76		9.22	$	70,079
Exercisable as of June 30, 2020		459,864		$	3.39		8.79	$	13,367
Vested and expected to vest as of June 30, 2020		2,529,999		$	4.76		9.22	$	70,079

	Number of Options			Weighted- Average Exercise Price per Share		Weighted- Average Remaining Contractual Term (in Years)		Aggregate Intrinsic Value
Outstanding as of December 31, 2018		113,174		$	2.08		9.77	$	348
Granted		1,166,398		$	2.86
Exercised		(21,940	)	$	6.01
Forfeited		(2,010	)	$	2.08
Outstanding as of June 30, 2019		1,255,622		$	2.79		9.60	$	5,341
Exercisable as of June 30, 2019		97,942		$	2.79		9.55	$	379
Vested and expected to vest as of June 30, 2019		1,255,622		$	2.79		9.60	$	5,431

Aggregate intrinsic value represents the difference between the fair value of the underlying common stock and the exercise price as of June 30, 2020 and December 31, 2019. The weighted-average grant date fair value of options granted during the six months ended June 30, 2020 and 2019, was $4.29 per share and $4.29 per share, respectively.

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 only commence vesting upon the effectiveness of an IPO by the Company, provided that the IPO must occur no later than December 31, 2021. Lastly, in order to vest at each calendar quarter end date, the shareholder must be providing continuous service to the Company through such vesting date. On December 31, 2021, this option will be cancelled if it has not commenced vesting. The stock-based compensation expense related to these options was immaterial during the three and six months ended June 30, 2020. See Note 14 for additional information.

Stock-Based Compensation Expense

The following table presents the components and classification of stock-based compensation expense for the Company’s stock-based awards for the three and six months ended June 30, 2020 and 2019 (in thousands):

	Three Months Ended June 30,				Six Months Ended June 30,
	2020		2019		2020		2019
Restricted stock awards and founders’ common stock awards	$	51	$	68	$	109	$	144
Stock options		735		438		1,102	674
Total stock-based compensation expense	$	786	$	506	$	1,211	$	818
Research and development expenses	$	287	$	136	$	451	$	225
General and administrative expenses	$	499	$	370	$	760	$	593

As of June 30, 2020, there was $0.3 million of unrecognized compensation costs that is expected to be recognized over the weighted-average periods of 1.7 years related to restricted stock awards. As of June 30, 2020, there was $8.3 million of unrecognized compensation costs that is expected to be recognized over the weighted-average periods of 2.78 years related to stock options.

As of June 30, 2019, there was $0.6 million of unrecognized compensation costs that is expected to be recognized over the weighted-average periods of 2.62 years related to restricted stock awards. As of June 30, 2019, there was $4.7 million of unrecognized compensation costs that is expected to be recognized over the weighted-average periods of 3.54 years related to stock options.

2020 Employee Stock Purchase Plan

In June 2020, the Company adopted 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 (1) 1.0% of the total number of shares of common stock outstanding on December 31 of the preceding calendar year, (2) 700,000 shares or (3) such lesser amount as determined by the administrator of the 2020 ESPP, which is the compensation committee of the board of directors.

Under the 2020 ESPP, eligible employees are granted options to 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. The 2020 ESPP is considered a compensatory plan, and the Company has not recorded any stock-based compensation expense for the three and six months ended June 30, 2020, as there have not been any grants under the ESPP plan. As of June 30, 2020, no shares of common stock were issued under the 2020 ESPP.

Income Taxes

6 Months Ended

Jun. 30, 2020

Income Tax Disclosure [Abstract]

Income Taxes

12. Income Taxes

For the three and six months ended June 30, 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 asset will not be realized. As a result, the Company’s effective tax rate will remain at 0.00% because no items that are either estimated or discrete items would impact the tax provision.

On March 27, 2020, the Coronavirus Aid, Relief and Economic Security (“CARES”) Act was enacted and signed into law and GAAP requires recognition of the tax effects of new legislation during the reporting period that includes the enactment date. The CARES Act, includes changes to the tax provisions that benefits business entities, and makes certain technical corrections to the 2017 Tax Cuts and Jobs Act. The tax relief measures for businesses include a five-year net operating loss carryback, suspension of annual deduction limitation of 80% of taxable income from net operating losses generated in a tax year beginning after December 31, 2017 through December 31, 2020, changes the deductibility of interest, acceleration of alternative minimum tax credit refunds, payroll tax relief, and a technical correction to allow accelerated deductions for qualified improvement property. The CARES Act also provides other non-tax benefits to assist those impacted by the pandemic. The Company evaluated the impact of the CARES Act and determined that its adoption did not have a material impact to the income tax provision for the three and six months ended June 30, 2020.

- 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 + Details

Commitments and Contingencies

6 Months Ended

Jun. 30, 2020

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

13. Commitments and Contingencies

Purchase Commitments

The Company has contractual arrangements with research and development organizations and suppliers; however, these contracts are generally cancelable 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.

Leases

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 June 30, 2020 and December 31, 2019. 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.

During the three months ended June 30, 2020 and 2019, rent expense, including common area maintenance expense, was $0.6 million. For the six months ended June 30, 2020 and 2019 rent expense was $1.3 million.

Future minimum lease payments under the Lease as of June 30, 2020 were as follows (in thousands):

Year ending December 31:	Operating Lease
2020 (remainder of the year)	$	996
2021		2,027
2022		2,098
2023		2,171
2024 and beyond		3,390
Total	$	10,682

Legal Proceedings

The Company, from time to time, may be party to litigation arising in the ordinary course of business. The Company was not subject to any material legal proceedings as of June 30, 2020 and December 31, 2019, and, to the best of its knowledge, no material legal proceedings are currently pending or threatened.

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.

Related Party Transactions

6 Months Ended

Jun. 30, 2020

Related Party Transactions

14. Related Party Transactions

In 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 three and six months ended June 30, 2020. The Company recorded Third Rock Ventures consulting expenses to general and administrative expense of $14,000 and $26,000, respectively for the three and six months ended June 30, 2019.

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. Lastly, in order to vest at each calendar quarter end date, the shareholder must be providing continuous service to the Company through such vesting date. See Note 11 for additional information.

From time to time, the Company makes charitable contributions to the University of California, San Francisco Foundation (the “UCSF Foundation”), which are directed to support research performed in the laboratories of two of the Company’s scientific founders. The Company made charitable contributions to the UCSF Foundation in the amount of nil and $0.7 million during the three and six months ended June 30, 2020, respectively. The Company made charitable contributions to the UCSF Foundation in the amount of $0.4 million and $0.4 million during the three and six months ended June 30, 2019, respectively.

In October 2019, the Company entered into the Novartis Agreement with Novartis covering the development and commercialization of Pliant’s preclinical product candidate, PLN-1474 and up to three additional targets. Upon execution of the Agreement, Pliant also entered into a financing side letter with Novartis, whereby Novartis committed to provide up to $30.0 million in equity financing of which $20.0 million was provided for preferred shares as a part of a Series C equity offering and the remaining $10.0 million was completed in a private placement for common shares upon the Company’s IPO. As of June 30, 2020 and December 31, 2019, Novartis owns approximately 6.1% and 7.4 % of our outstanding shares of common stock on a fully diluted basis. See Notes 6 and Note 9 for additional information.

Defined Contribution Plan

6 Months Ended

Jun. 30, 2020

Compensation And Retirement Disclosure [Abstract]

Defined Contribution Plan

15. Defined Contribution Plan

The Company sponsors a defined contribution plan under Section 401(k) of the Internal Revenue Code covering substantially all full-time U.S. employees. Employee contributions are voluntary and are determined on an individual basis subject to the maximum allowable under federal tax regulations. The Company made contributions to the plan of $0.1 million and $0.1 million for the three months ended June 30, 2020 and 2019, respectively, and $0.2 million and $0.1 million for the six months ended June 30, 2020 and 2019, respectively.

Net Loss Per Share Attributable to Common Stockholders

6 Months Ended

Jun. 30, 2020

Earnings Per Share [Abstract]

Net Loss Per Share Attributable to Common Stockholders

16. 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:

	Six Months Ended June 30,
	2020		2019
Redeemable convertible preferred stock (on an as-converted basis)		—		14,755,415
Options to purchase common stock		2,529,999		1,259,905
Restricted stock awards granted and not purchased		4,195		4,195
Unvested restricted shares		197,891		474,329
Unvested shares of founders’ common stock		—		6,806
Total		2,732,085		16,500,650

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):

	Three Months Ended June 30,						Six Months Ended June 30,
	2020			2019			2020			2019
Net loss per share:
Numerator
Net loss	$	(17,001	)	$	(15,522	)	$	(5,972	)	$	(29,545	)
Add: accretion to redemption value and cumulative dividends on redeemable convertible preferred shares		—			(1,359	)		—			(2,703	)
Net loss attributable to common stockholders	$	(17,001	)	$	(16,881	)	$	(5,972	)	$	(32,248	)
Denominator
Weighted-average common shares outstanding used to calculate net loss per share attributable to common stockholders:
Basic		12,253,943			1,559,942			7,062,780			1,486,109
Diluted		12,253,943			1,559,942			7,062,780			1,486,109
Net loss per share attributable to common stockholders:
Basic	$	(1.39	)	$	(10.82	)	$	(0.85	)	$	(21.70	)
Diluted	$	(1.39	)	$	(10.82	)	$	(0.85	)	$	(21.70	)

Subsequent Events

6 Months Ended

Jun. 30, 2020

Subsequent Events [Abstract]

Subsequent Events

17. Subsequent Events

The Company has evaluated subsequent events for financial statement purposes occurring through August 10, 2020, the date these financial statements were issued.

Summary of Significant Accounting Policies (Policies)

6 Months Ended

Jun. 30, 2020

Accounting Policies [Abstract]

Basis of Presentation

The accompanying financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”).

Use of Estimates

Revenue Recognition

To date all revenue has been generated from the Company’s Collaboration and License Agreement with Novartis (the “Novartis Agreement”).

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

Impairment of Long-Lived Assets

Redeemable Convertible Preferred Stock

Research and Development Expenses

Tax Credit Receivable

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.

Deferred Offering Costs

Leases and Rent Expense

Income Taxes

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

Comprehensive Gain

Comprehensive (Loss) Income

Net (Loss) Income Per Share

Recently Issued Accounting Pronouncements

Summary of Significant Accounting Policies (Tables)

6 Months Ended

Jun. 30, 2020

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)

6 Months Ended

Jun. 30, 2020

Fair Value Disclosures [Abstract]

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

	As of June 30, 2020
	Adjusted Cost		Unrealized Gains		Unrealized Losses			Market Value
Level 1:
Money Market Funds	$	126,191	$	—	$	—		$	126,191
Level 2:
U.S. Treasury securities included in short-term investments		85,706		4		(13	)		85,697
U.S. government agency securities included in cash and cash equivalents and short-term investments		62,051		2		(23	)		62,030
Total financial assets	$	273,948	$	6	$	(36	)	$	273,918

	As of December 31, 2019
	Adjusted Cost		Unrealized Gains		Unrealized Losses			Market Value
Level 1:
Money Market Funds	$	16,366	$	—	$	—		$	16,366
Level 2:
U.S. Treasury securities included in short-term investments		2,998		—		—			2,998
U.S. government agency securities included in short-term investments		34,204		1		(2	)		34,203
Total financial assets	$	53,568	$	1	$	(2	)	$	53,567

Property and Equipment, net (Tables)

6 Months Ended

Jun. 30, 2020

Property Plant And Equipment [Abstract]

Schedule of Property and Equipment

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

	As of June 30, 2020			As of December 31, 2019
Computer equipment and software	$	22		$	22
Laboratory equipment		6,078			5,580
Leasehold improvements		701			657
Construction-in-progress		49			8
Total property and equipment, gross		6,850			6,267
Less: Accumulated depreciation		(2,821	)		(2,188	)
Total property and equipment, net	$	4,029		$	4,079

Accrued Liabilities and Other Long-Term Liabilities (Tables)

6 Months Ended

Jun. 30, 2020

Accrued Liabilities And Other Liabilities [Abstract]

Schedule of Accrued Liabilities

Accrued liabilities consisted of the following (in thousands):

	As of June 30, 2020		As of December 31, 2019
Accrued compensation and benefits	$	2,003	$	2,971
Accrued research and development expenses		5,373		2,624
Other accrued liabilities		2,147		1,263
Deferred rent		30		64
Total accrued liabilities	$	9,553	$	6,922

Summary of Other Long-Term Liabilities

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

	As of June 30, 2020		As of December 31, 2019
Deferred rent	$	540	$	458
Leasehold incentive obligation		404		444
Other liabilities — deposits		7		10
Total other long-term liabilities	$	951	$	912

Redeemable Convertible Preferred Stock (Tables)

6 Months Ended

Jun. 30, 2020

Temporary Equity Disclosure [Abstract]

Summary of Redeemable Convertible Preferred Stock

The following is a summary of the Company’s redeemable convertible preferred stock as of December 31, 2019 (in thousands except share amounts):

	Preferred Shares Authorized		Shares Issued and Outstanding		Redemption Value/ Liquidation Preference		Carrying Value
Series A		56,000,000		56,000,000	$	62,468	$	62,468
Series B		49,501,221		49,501,221		75,860		75,860
Series C		44,000,000		26,360,745		47,947		47,947
		149,501,221		131,861,966	$	186,275	$	186,275

Common Stock (Tables)

6 Months Ended

Jun. 30, 2020

Equity [Abstract]

Schedule of Shares Reserved for Future Issuance

Shares reserved for future issuance

	As of June 30, 2020		As of December 31, 2019
Conversion of redeemable convertible preferred stock		—		18,442,233
Exercises of outstanding stock option awards		2,529,999		1,337,501
Shares of common stock available for future grants under the 2015 Equity Incentive Plan, as amended		—		567,110
Shares of common stock available for future grants under the 2020 Equity Incentive Plan		4,200,000		—
Shares of common stock available for future issuance under the 2020 ESPP		700,000		—
Total shares reserved for future issuance		7,429,999		20,346,844

Equity Incentive Plans and Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2020

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Restricted Stock Activity

The following table summarizes restricted stock activity during the six months ended June 30, 2020:

	Number of Shares			Weighted- Average Grant Date fair value
Outstanding and unvested, as of December 31, 2019		302,211		$	1.51
Issued		—		$	—
Vested		(92,199	)	$	1.19
Repurchases		(12,121	)	$	1.22
Outstanding and unvested, as of June 30, 2020		197,891		$	1.70

The following table summarizes restricted stock activity during the six months ended June 30, 2019:

	Number of Shares			Weighted- Average Grant Date fair value
Outstanding and unvested, as of December 31, 2018		703,188		$	1.22
Issued		—		$	—
Vested		(225,551	)	$	1.01
Exercised		363		$	2.15
Repurchases		(3,671	)	$	2.15
Outstanding and unvested, as of June 30, 2019		474,329		$	1.22

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:

	Three Months Ended June 30,				Six Months Ended June 30,
	2020		2019		2020		2019
Expected volatility		—	79.37% - 82.15%		72.10% - 77.50%		78.50% - 82.55%
Risk-free interest rate		—	1.81% - 2.30%		0.52% - 0.82%		1.81% - 2.59%
Expected dividend		—		—		—		—
Expected term (in years)		—	5.81 - 6.08		5.38 - 6.75		5.00 - 6.08
Underlying common stock fair value		—		6.22		6.22		5.15

Summary of Option Activity Under the 2015 Plan

A summary of option activity under the 2015 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, 2019		1,337,501		$	3.22		9.18	$	5,157
Granted		1,275,202		$	6.22
Exercised		(81,996	)	$	2.47
Forfeited		(708	)	$	2.08
Outstanding as of June 30, 2020		2,529,999		$	4.76		9.22	$	70,079
Exercisable as of June 30, 2020		459,864		$	3.39		8.79	$	13,367
Vested and expected to vest as of June 30, 2020		2,529,999		$	4.76		9.22	$	70,079

	Number of Options			Weighted- Average Exercise Price per Share		Weighted- Average Remaining Contractual Term (in Years)		Aggregate Intrinsic Value
Outstanding as of December 31, 2018		113,174		$	2.08		9.77	$	348
Granted		1,166,398		$	2.86
Exercised		(21,940	)	$	6.01
Forfeited		(2,010	)	$	2.08
Outstanding as of June 30, 2019		1,255,622		$	2.79		9.60	$	5,341
Exercisable as of June 30, 2019		97,942		$	2.79		9.55	$	379
Vested and expected to vest as of June 30, 2019		1,255,622		$	2.79		9.60	$	5,431

Summary of Components and Classification of Stock-based Compensation Expense for Stock-based Awards

	Three Months Ended June 30,				Six Months Ended June 30,
	2020		2019		2020		2019
Restricted stock awards and founders’ common stock awards	$	51	$	68	$	109	$	144
Stock options		735		438		1,102	674
Total stock-based compensation expense	$	786	$	506	$	1,211	$	818
Research and development expenses	$	287	$	136	$	451	$	225
General and administrative expenses	$	499	$	370	$	760	$	593

Commitments and Contingencies (Tables)

6 Months Ended

Jun. 30, 2020

Commitments And Contingencies Disclosure [Abstract]

Schedule of Future Minimum Lease Payments

Future minimum lease payments under the Lease as of June 30, 2020 were as follows (in thousands):

Year ending December 31:	Operating Lease
2020 (remainder of the year)	$	996
2021		2,027
2022		2,098
2023		2,171
2024 and beyond		3,390
Total	$	10,682

Net Loss Per Share Attributable to Common Stockholders (Tables)

6 Months Ended

Jun. 30, 2020

Earnings Per Share [Abstract]

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

	Six Months Ended June 30,
	2020		2019
Redeemable convertible preferred stock (on an as-converted basis)		—		14,755,415
Options to purchase common stock		2,529,999		1,259,905
Restricted stock awards granted and not purchased		4,195		4,195
Unvested restricted shares		197,891		474,329
Unvested shares of founders’ common stock		—		6,806
Total		2,732,085		16,500,650

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

	Three Months Ended June 30,						Six Months Ended June 30,
	2020			2019			2020			2019
Net loss per share:
Numerator
Net loss	$	(17,001	)	$	(15,522	)	$	(5,972	)	$	(29,545	)
Add: accretion to redemption value and cumulative dividends on redeemable convertible preferred shares		—			(1,359	)		—			(2,703	)
Net loss attributable to common stockholders	$	(17,001	)	$	(16,881	)	$	(5,972	)	$	(32,248	)
Denominator
Weighted-average common shares outstanding used to calculate net loss per share attributable to common stockholders:
Basic		12,253,943			1,559,942			7,062,780			1,486,109
Diluted		12,253,943			1,559,942			7,062,780			1,486,109
Net loss per share attributable to common stockholders:
Basic	$	(1.39	)	$	(10.82	)	$	(0.85	)	$	(21.70	)
Diluted	$	(1.39	)	$	(10.82	)	$	(0.85	)	$	(21.70	)

Organization and Description of Business - Additional Information (Detail) $ / shares in Units, $ in Thousands			6 Months Ended		12 Months Ended
	Jun. 05, 2020 USD ($) $ / shares shares	May 22, 2020	Jun. 30, 2020 USD ($) shares	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($) shares
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Reverse stock split, description			1-for-7.15
Reverse stock split, conversion ratio		0.13986014	0.1399
Common stock, shares issued			35,427,199		1,846,024
Proceeds from issuance of common stock \| $				$ 132
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	10,350,000
Share price of shares issued in initial public offering \| $ / shares	$ 16.00
Proceeds from the initial public offering \| $	$ 148,400
Underwriting discounts, commissions and offering expenses \| $	$ 5,600		$ 900		$ 2,600
Convertible preferred stock converted into common shares	160,389,279
Reclassification of convertible preferred stock into additional paid in capital upon initial public offering \| $	$ 238,300
Initial Public Offering \| Underwriters
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Initial public offering, shares issued	1,350,000
Initial Public Offering \| Common Stock
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Initial public offering, shares issued	9,000,000
Private Placement \| Novartis
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Common stock, shares issued	625,000
Share price \| $ / shares	$ 16.00
Proceeds from issuance of common stock \| $	$ 10,000
Private Placement \| Pliant Therapeutics, Inc. \| Novartis
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Percentage of noncontrolling ownership	6.10%

Summary of Significant Accounting Policies - Additional Information (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) Segment	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Accounting Policies [Line Items]
Revenue recognized		$ 0		$ 0
Number of reportable segments \| Segment			1
Number of operating segments \| Segment			1
Debt instrument remaining maturity period at date of purchase			3 months
Debt instrument remaining maturity period from balance sheet date			one year or less
Impairment of long-lived assets	$ 0	0	$ 0	0
Expected dividend yield			0.00%
Deferred offering costs					$ 2,700,000
Net unrealized (loss) gain on short-term investments	$ (89,000)	$ 8,000	$ (29,000)	$ 11,000
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.
Percentage of revenue contributed by related party	100.00%		100.00%
Novartis Agreement \| Maximum
Accounting Policies [Line Items]
Customer payment terms			60 days

Summary of Significant Accounting Policies - Summary of Useful Lives of Property and Equipment (Details)	6 Months Ended
	Jun. 30, 2020
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
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property, plant and equipment, estimated useful lives	Shorter of remaining lease term or estimated useful life

Financial Instruments - Summary of Cash and Cash Equivalents, Money Market Funds and Short-term Investments by Significant Investment Category (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Schedule Of Available For Sale Securities [Line Items]
Adjusted Cost	$ 273,948	$ 53,568
Unrealized Gains	6	1
Unrealized Losses	(36)	(2)
Market Value	273,918	53,567
Level 1 \| Money Market Funds
Schedule Of Available For Sale Securities [Line Items]
Adjusted Cost	126,191	16,366
Market Value	126,191	16,366
Level 2 \| U.S. Treasury Securities Included in Short-term Investments
Schedule Of Available For Sale Securities [Line Items]
Adjusted Cost	85,706	2,998
Unrealized Gains	4
Unrealized Losses	(13)
Market Value	85,697	2,998
Level 2 \| U.S. Government Agency Securities Included in Cash and Cash equivalents and Short-term Investments
Schedule Of Available For Sale Securities [Line Items]
Adjusted Cost	62,051	34,204
Unrealized Gains	2	1
Unrealized Losses	(23)	(2)
Market Value	$ 62,030	$ 34,203

Financial Instruments - Additional Information (Details) - USD ($)	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Liabilities measured at fair value	$ 0		$ 0
Transfers of assets between Level 1 and Level 2	0	$ 0
Transfers of assets between Level 2 and Level 1	0	0
Transfers of liabilities between Level 1 and Level 2	0	0
Transfers of liabilities between Level 2 to Level 1	0	0
Transfer out of Level 3 measurement	0	0
Transfer in to Level 3 measurement	0	$ 0
Fair Value Measurements, Non-recurring Basis
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Liabilities measured at fair value	0		0
Assets measured at fair value	$ 0		$ 0

Property and Equipment, net - Schedule of Property and Equipment (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Property Plant And Equipment [Line Items]
Total property and equipment, gross	$ 6,850	$ 6,267
Less: Accumulated depreciation	(2,821)	(2,188)
Total property and equipment, net	4,029	4,079
Computer Equipment and Software
Property Plant And Equipment [Line Items]
Total property and equipment, gross	22	22
Laboratory Equipment
Property Plant And Equipment [Line Items]
Total property and equipment, gross	6,078	5,580
Leasehold Improvements
Property Plant And Equipment [Line Items]
Total property and equipment, gross	701	657
Construction in Progress
Property Plant And Equipment [Line Items]
Total property and equipment, gross	$ 49	$ 8

Property and Equipment, net - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Property Plant And Equipment [Abstract]
Depreciation expense	$ 300	$ 200	$ 633	$ 536

Accrued Liabilities and Other Long-Term Liabilities - Summary of Accrued Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Accrued Liabilities And Other Liabilities [Abstract]
Accrued compensation and benefits	$ 2,003	$ 2,971
Accrued research and development expenses	5,373	2,624
Other accrued liabilities	2,147	1,263
Deferred rent	30	64
Total accrued liabilities	$ 9,553	$ 6,922

Accrued Liabilities and Other Long-Term Liabilities - Summary of Other Long-Term Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Accrued Liabilities And Other Liabilities [Abstract]
Deferred rent	$ 540	$ 458
Leasehold incentive obligation	404	444
Other liabilities — deposits	7	10
Total other long-term liabilities	$ 951	$ 912

Novartis Agreement - Additional Information (Details)			1 Months Ended	3 Months Ended			6 Months Ended
Novartis Agreement - Additional Information (Details)	Dec. 19, 2019 USD ($) shares	Dec. 07, 2019 USD ($)	Oct. 31, 2019 USD ($) Research $ / shares	Jun. 30, 2020 USD ($) shares	Mar. 31, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) shares	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($) shares
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Preferred stock, shares issued \| shares				0			0		0
Series C Redeemable Convertible Preferred Stock
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Preferred stock, shares issued \| shares				0			0		26,360,745
Novartis \| Novartis Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Proceeds from upfront non-refundable license fee		$ 50,000,000
Collaboration and license agreement, description							The Company is initially obligated to perform research and development services on the integrin research targets for sixty days, and Novartis has the option to terminate the services with 60 days notification.
Collaboration and license agreement, target validation fee			$ 4,000,000
Committed to provide equity financing			30,000,000
Percentage of outstanding shares of common stock on fully diluted basis				6.10%			6.10%		7.40%
Transaction price of Novartis agreement			69,600,000
Selling price of license			50,000,000
Revenue recognized from related party				$ 3,600,000		$ 0	$ 32,500,000	$ 0
Receivable from related party transactions				3,600,000			3,600,000		$ 7,100,000
Contract assets				0			0		0
Contract liabilities				0			0		$ 0
Novartis \| Novartis Agreement \| Achievement of First Patient Dosing Milestone
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue recognized from related party					$ 25,000,000
Novartis \| Novartis Agreement \| License Fee
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Transaction price of Novartis agreement			50,000,000
Novartis \| Novartis Agreement \| Research and Development
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Transaction price of Novartis agreement			19,600,000
Revenue recognized from related party				$ 3,600,000			$ 7,500,000
Novartis \| Novartis Agreement \| Initial Public Offering
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Committed to provide equity financing			10,000,000
Novartis \| Novartis Agreement \| Series C Redeemable Convertible Preferred Stock
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Committed to provide equity financing	$ 20,000,000		$ 20,000,000
Preferred stock, shares issued \| shares	10,928,962
Redeemable convertible preferred stock issued at fair value per share \| $ / shares			$ 1.83
Purchase of redeemable convertible preferred stock	$ 10,900,000
Novartis \| Novartis Agreement \| Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of Integrin research targets \| Research			3
Receivable from development services			$ 19,600,000
Collaboration and license agreement, integrin research targets amount			416,000,000
Committed to provide equity financing			$ 30,000,000

License Agreements - Additional Information (Details) - License Agreements - UC Regents - USD ($)	1 Months Ended	6 Months Ended
	Aug. 31, 2015	Jun. 30, 2020
License Agreements [Line Items]
Payment of non-refundable upfront license fee	$ 400,000
Payment of annual license maintenance fee	10,000
Payment of annual license maintenance fee after first year	$ 25,000
Percentage of royalty payments on net sales of licensed product	3.00%
Percentage of royalty payments on net sales of method use licensed product	1.00%
Annual minimum royalty payment on net sales	$ 1,000,000
Aggregate contingency payment on certain events milestones	$ 18,200,000
Milestone and annual royalty paid		$ 2,400,000

Research Agreement - Additional Information (Details) - USD ($)	1 Months Ended	3 Months Ended		6 Months Ended
	Oct. 31, 2018	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Research And Development Arrangement Contract To Perform For Others [Line Items]
Research and development expense		$ 17,536,000	$ 13,098,000	$ 31,455,000	$ 24,847,000
Adimab Agreement
Research And Development Arrangement Contract To Perform For Others [Line Items]
Development and option agreement date	2018-10
Research and development expense		$ 37,000	$ 200,000	$ 37,000	$ 300,000

Redeemable Convertible Preferred Stock - Additional Information (Details)				1 Months Ended											6 Months Ended
	May 22, 2020	Dec. 19, 2019	Jul. 10, 2018	Feb. 29, 2020 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares	Nov. 30, 2018 USD ($) $ / shares shares	Jul. 31, 2018 USD ($) $ / shares shares	Mar. 31, 2018 USD ($) $ / shares shares	Jan. 31, 2018 USD ($) $ / shares shares	Jul. 31, 2017 USD ($) $ / shares shares	Feb. 28, 2017 USD ($) $ / shares shares	Sep. 30, 2016 USD ($) $ / shares shares	Apr. 30, 2016 USD ($) $ / shares shares	Aug. 31, 2015 USD ($) Tranche $ / shares shares	Jun. 30, 2020 Member $ / shares shares	Mar. 31, 2020 shares	Jun. 30, 2019 shares	Mar. 31, 2019 shares	Dec. 31, 2018 shares
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares outstanding					0										0
Redeemable convertible preferred stock, shares issued					0										0
Redeemable convertible preferred stock, par value \| $ / shares					$ 0.0001										$ 0.0001
Redeemable convertible preferred stock, shares authorized					0										10,000,000
Preferred stock, voting rights description															Each holder of shares of Preferred Stock is entitled to the number of votes equal to the number of shares of common stock into which such shares could be converted and has voting rights and powers equal to the voting rights and powers of the common stock, and except as provided by law or by other provisions of the Company’s Certificate of Incorporation, as amended, shall vote together with the common stock as a single class on an as-converted basis on all matters as to which holders of common stock have the right to vote.
Convertible preferred stock, terms of conversion															Shares of the Preferred Stock are convertible at any time at the option of the holder into such number of shares as is determined by dividing the original issuance price by the conversion price in effect at the time.
Reverse stock split, conversion ratio	0.13986014														0.1399
Series B Preferred Stock Purchase Agreement
Temporary Equity [Line Items]
Preferred stock redemption terms															All outstanding shares of Preferred Stock shall be redeemed by the Company at a price equal to the original issuance price per share, plus any accrued and unpaid dividends, whether or not declared, together with any other dividends declared but unpaid in three annual installments commencing not more than sixty (60) days after receipt by the Company at any time on or after five years from the Series B Preferred original issuance date, July 10, 2018, a written notice from the holders of a majority of the shares of Preferred Stock.
Series C Preferred Stock Purchase Agreement
Temporary Equity [Line Items]
Preferred stock redemption terms															All outstanding shares of Preferred Stock shall be redeemed by the Company at a price equal to the original issuance price per share, plus any dividends declared but unpaid, in three annual installments commencing not more than sixty (60) days after receipt by the Company at any time on or after five years from the Series C Preferred original issuance date, December 19, 2019, a written notice from the holders of a majority of the shares of Preferred Stock.
Redeemable Convertible Preferred Stock
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares outstanding															0
Series A Preferred Stock
Temporary Equity [Line Items]
Preferred stock dividend rate														8.00%
Preferred stock shares redemption														6,500,000
Series A Preferred Stock \| Series A Preferred Stock Purchase Agreement
Temporary Equity [Line Items]
Number of tranches \| Tranche														3
Redeemable convertible preferred stock, shares issued														6,500,000
Redeemable convertible preferred stock, par value \| $ / shares														$ 1.00
Cash proceeds from preferred stock \| $														$ 6,400,000
Outstanding principal and accrued interest \| $														100,000
Series A Preferred Stock \| Series A Preferred Stock Purchase Agreement \| First Tranche
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares issued												5,000,000	5,000,000
Redeemable convertible preferred stock, par value \| $ / shares												$ 1.00	$ 1.00
Cash proceeds from preferred stock \| $												$ 5,000,000	$ 5,000,000
Series A Preferred Stock \| Series A Preferred Stock Purchase Agreement \| Second Tranche
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares issued											8,000,000
Redeemable convertible preferred stock, par value \| $ / shares											$ 1.00
Cash proceeds from preferred stock \| $											$ 8,000,000
Series A Preferred Stock \| Series A Preferred Stock Purchase Agreement \| Third Tranche
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares issued								11,000,000	8,500,000	12,000,000
Redeemable convertible preferred stock, par value \| $ / shares								$ 1.00	$ 1.00	$ 1.00
Cash proceeds from preferred stock \| $								$ 11,000,000	$ 8,500,000	$ 12,000,000
Series A Preferred Stock \| Maximum \| Series A Preferred Stock Purchase Agreement
Temporary Equity [Line Items]
Preferred stock, purchase amount \| $														$ 45,000,000
Series B Redeemable Convertible Preferred Stock
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares outstanding					49,501,221										0	49,501,221	49,501,221	49,501,221	49,501,221
Redeemable convertible preferred stock, shares issued					49,501,221										0
Redeemable convertible preferred stock, par value \| $ / shares					$ 0.0001										$ 0.0001
Redeemable convertible preferred stock, shares authorized					49,501,221										0
Number of members of board of directors \| Member															1
Preferred stock conversion price per share \| $ / shares															$ 9.843405
Preferred stock liquidation price per share \| $ / shares															$ 1.3767
Series B Redeemable Convertible Preferred Stock \| Series B Preferred Stock Purchase Agreement
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares issued						4,400,000	45,100,000
Redeemable convertible preferred stock, par value \| $ / shares						$ 1.3767	$ 1.3767
Cash proceeds from preferred stock \| $						$ 6,000,000	$ 62,100,000
Series B Redeemable Convertible Preferred Stock \| Maximum \| Series B Preferred Stock Purchase Agreement
Temporary Equity [Line Items]
Preferred stock, purchase amount \| $							$ 70,000,000
Series B Redeemable Convertible Preferred Stock \| Minimum [Member]
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares outstanding															12,500,000
Series C Preferred Stock [Member] \| Series C Preferred Stock Purchase Agreement
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares issued				28,500,000	26,400,000
Redeemable convertible preferred stock, par value \| $ / shares				$ 1.83	$ 1.83
Cash proceeds from preferred stock \| $				$ 52,200,000	$ 48,200,000
Preferred stock, shares issuance costs \| $				$ 200,000
Series C Preferred Stock [Member] \| Series C Preferred Stock Purchase Agreement \| Novartis
Temporary Equity [Line Items]
Redeemable convertible preferred stock, par value \| $ / shares					$ 1.83
Cash proceeds from preferred stock \| $					$ 20,000,000
Redeemable convertible preferred stock, shares authorized					10,900,000
Percentage of outstanding shares of common stock on fully diluted basis					7.40%										6.10%
Series C Preferred Stock [Member] \| Maximum \| Series C Preferred Stock Purchase Agreement
Temporary Equity [Line Items]
Preferred stock, purchase amount \| $					$ 80,500,000
Series A Redeemable Convertible Preferred Stock
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares outstanding					56,000,000										0	56,000,000	56,000,000	56,000,000	56,000,000
Redeemable convertible preferred stock, shares issued					56,000,000										0
Redeemable convertible preferred stock, par value \| $ / shares					$ 0.0001										$ 0.0001
Redeemable convertible preferred stock, shares authorized					56,000,000										0
Number of members of board of directors \| Member															2
Preferred stock conversion price per share \| $ / shares															$ 7.15
Preferred stock liquidation price per share \| $ / shares															$ 1.00
Common Stock
Temporary Equity [Line Items]
Number of members of board of directors \| Member															1
Series C Redeemable Convertible Preferred Stock
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares outstanding					26,360,745										0	54,888,058
Redeemable convertible preferred stock, shares issued					26,360,745										0
Redeemable convertible preferred stock, par value \| $ / shares					$ 0.0001										$ 0.0001
Redeemable convertible preferred stock, shares authorized					44,000,000										0
Preferred stock conversion price per share \| $ / shares															$ 13.0845
Preferred stock liquidation price per share \| $ / shares															$ 1.83
Series A and Series B Preferred \| Series B Preferred Stock Purchase Agreement
Temporary Equity [Line Items]
Preferred stock dividend rate			8.00%
Series A, Series B and Series C Preferred \| Series C Preferred Stock Purchase Agreement
Temporary Equity [Line Items]
Preferred stock dividend rate		8.00%

Redeemable Convertible Preferred Stock - Summary of Redeemable Convertible Preferred Stock (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares authorized	10,000,000		0
Redeemable convertible preferred stock, shares issued	0		0
Redeemable convertible preferred stock, shares outstanding	0		0
Series A Redeemable Convertible Preferred Stock
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares authorized	0		56,000,000
Redeemable convertible preferred stock, shares issued	0		56,000,000
Redeemable convertible preferred stock, shares outstanding	0	56,000,000	56,000,000	56,000,000	56,000,000	56,000,000
Redeemable convertible preferred stock. aggregate liquidation preference	$ 0		$ 62,468
Redeemable convertible preferred stock value		$ 62,468	$ 62,468	$ 61,516	$ 61,516	$ 61,516
Series B Redeemable Convertible Preferred Stock
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares authorized	0		49,501,221
Redeemable convertible preferred stock, shares issued	0		49,501,221
Redeemable convertible preferred stock, shares outstanding	0	49,501,221	49,501,221	49,501,221	49,501,221	49,501,221
Redeemable convertible preferred stock. aggregate liquidation preference	$ 0		$ 75,860
Redeemable convertible preferred stock value		$ 75,860	$ 75,860	$ 73,290	$ 71,931	$ 70,587
Series C Redeemable Convertible Preferred Stock
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares authorized	0		44,000,000
Redeemable convertible preferred stock, shares issued	0		26,360,745
Redeemable convertible preferred stock, shares outstanding	0	54,888,058	26,360,745
Redeemable convertible preferred stock. aggregate liquidation preference	$ 0		$ 47,947
Redeemable convertible preferred stock value		$ 99,985	$ 47,947
Amended and Restated Certificate of Incorporation
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares authorized			149,501,221
Redeemable convertible preferred stock, shares issued			131,861,966
Redeemable convertible preferred stock, shares outstanding			131,861,966
Redeemable convertible preferred stock. aggregate liquidation preference			$ 186,275
Redeemable convertible preferred stock value			$ 186,275
Amended and Restated Certificate of Incorporation \| Series A Redeemable Convertible Preferred Stock
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares authorized			56,000,000
Redeemable convertible preferred stock, shares issued			56,000,000
Redeemable convertible preferred stock, shares outstanding			56,000,000
Redeemable convertible preferred stock. aggregate liquidation preference			$ 62,468
Redeemable convertible preferred stock value			$ 62,468
Amended and Restated Certificate of Incorporation \| Series B Redeemable Convertible Preferred Stock
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares authorized			49,501,221
Redeemable convertible preferred stock, shares issued			49,501,221
Redeemable convertible preferred stock, shares outstanding			49,501,221
Redeemable convertible preferred stock. aggregate liquidation preference			$ 75,860
Redeemable convertible preferred stock value			$ 75,860
Amended and Restated Certificate of Incorporation \| Series C Redeemable Convertible Preferred Stock
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares authorized			44,000,000
Redeemable convertible preferred stock, shares issued			26,360,745
Redeemable convertible preferred stock, shares outstanding			26,360,745
Redeemable convertible preferred stock. aggregate liquidation preference			$ 47,947
Redeemable convertible preferred stock value			$ 47,947

Common Stock - Additional Information (Details) - USD ($)	1 Months Ended	6 Months Ended	48 Months Ended	61 Months Ended
	Dec. 31, 2015	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2020
Class Of Stock [Line Items]
Common stock, shares authorized		300,000,000	181,000,000	300,000,000
Common stock, par value		$ 0.0001	$ 0.0001	$ 0.0001
Common stock, voting rights		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 declared				0
Dividends paid				$ 0
Founders Common Stock Awards
Class Of Stock [Line Items]
Number of shares granted during period	745,244		0
Total compensation expense	$ 25,000
Minimum [Member] \| Founders Common Stock Awards
Class Of Stock [Line Items]
Vesting period		1 year
Maximum \| Founders Common Stock Awards
Class Of Stock [Line Items]
Vesting period		4 years

Common Stock - Schedule of Shares Reserved for Future Issuance (Details) - shares	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Jan. 31, 2019	Jul. 31, 2018
Class Of Stock [Line Items]
Total shares reserved for future issuance	7,429,999		20,346,844
Redeemable Convertible Preferred Stock
Class Of Stock [Line Items]
Total shares reserved for future issuance			18,442,233
Exercises of Outstanding Stock Option Awards
Class Of Stock [Line Items]
Total shares reserved for future issuance	2,529,999		1,337,501
Shares of Common Stock Available for Future Grants under the 2015 Equity Incentive Plan, as Amended
Class Of Stock [Line Items]
Total shares reserved for future issuance		1,400,000	567,110	400,000	1,000,000
Shares of Common Stock Available for Future Grants under the 2020 Equity Incentive Plan
Class Of Stock [Line Items]
Total shares reserved for future issuance	4,200,000
Shares of Common Stock Available for Future Issuance under the 2020 ESPP
Class Of Stock [Line Items]
Total shares reserved for future issuance	700,000

Equity Incentive Plans and Stock-Based Compensation - Additional Information (Details) - USD ($)	1 Months Ended	6 Months Ended
	May 31, 2020	Jun. 30, 2020	Jun. 30, 2019	Mar. 31, 2020	Dec. 31, 2019	Jan. 31, 2019	Jul. 31, 2018	Aug. 31, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total shares reserved for future issuance		7,429,999			20,346,844
Two Thousand And Twenty Stock Options And 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		4,200,000
Exercise price as a percentage of estimated grant date fair value of shares		10.00%
Expiration period from date of grant		5 years
2015 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total shares reserved for future issuance				1,400,000	567,110	400,000	1,000,000
Exercise price as a percentage of estimated grant date fair value of shares		10.00%
Expiration period from date of grant		5 years
Number of remaining shares reserved for issuance		2,500,000
Restricted Common Stock Awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting rights		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.
Number of shares granted		0	0
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		$ 16,000			$ 22,000
Maximum \| Two Thousand And Twenty Stock Options And Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options under plan may be granted for periods		10 years
Percentage of estimated fair value of shares on date of grant		100.00%
Exercise price as a percentage of estimated grant date fair value of shares		110.00%
Maximum \| 2015 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options under plan may be granted for periods		10 years
Percentage of estimated fair value of shares on date of grant		100.00%
Exercise price as a percentage of estimated grant date fair value of shares		110.00%
Maximum \| Restricted Common Stock Awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period		4 years
Minimum [Member] \| Restricted Common Stock Awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period		1 year
Common Stock \| Maximum \| Two Thousand And Twenty Stock Options And Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares authorized for future grant	4,200,000
Common Stock \| Maximum \| 2015 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares authorized for future grant								1,500,000

Equity Incentive Plans and Stock-Based Compensation - Summary of Restricted Stock Activity (Details) - Restricted Common Stock Awards - $ / shares	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Shares, Outstanding and unvested, beginning balance	302,211	703,188
Number of shares granted during period	0	0
Number of Shares, Vested	(92,199)	(225,551)
Number of Shares, Exercised		363
Number of Shares, Repurchases	(12,121)	(3,671)
Number of Shares, Outstanding and unvested, ending balance	197,891	474,329
Weighted-Average Grant Date fair value, Outstanding and unvested, beginning balance	$ 1.51	$ 1.22
Weighted-Average Grant Date fair value, Vested	1.19	1.01
Weighted-Average Grant Date fair value, Exercised		2.15
Weighted-Average Grant Date fair value, Repurchases	1.22	2.15
Weighted-Average Grant Date fair value, Outstanding and unvested, ending balance	$ 1.70	$ 1.22

Equity Incentive Plans and Stock-Based Compensation - Restricted Common Stock Awards - Additional Information (Details) - USD ($)	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares, not purchased	4,195
Weighted-average grant date fair value, not purchased	$ 0.08
Restricted Stock Awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Aggregate fair value of restricted stock awards vested	$ 109,000	$ 219,000
Total intrinsic value of outstanding unvested restricted stock awards	$ 6,400,000		$ 3,300,000

Equity Incentive Plans and Stock-Based Compensation - Incentive Stock Options and Nonqualified Stock Options - Additional Information (Details) - Incentive Stock Options and Nonqualified Stock Options - $ / shares	1 Months Ended	3 Months Ended	6 Months Ended
	Mar. 31, 2020	Jun. 30, 2020	Jun. 30, 2020	Jun. 30, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Grant date fair value of stock option			$ 4.29	$ 4.29
Non-employee Director \| Third Rock Ventures
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option, vesting period	3 years
Option granted	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 only commence vesting upon the effectiveness of an IPO by the Company, provided that the IPO must occur no later than December 31, 2021.
2015 Equity and 2015 Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option, vesting period			4 years
Stock option, expiration period			10 years
Option granted		0

Equity Incentive Plans and Stock-Based Compensation - Summary of Black-Scholes Option Pricing Model to Estimate Stock-based Compensation Expense for Stock Option Awards (Details) - $ / shares	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected dividend yield		0.00%
Incentive Stock Options and Nonqualified Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected volatility, minimum	79.37%	72.10%	78.50%
Expected volatility, maximum	82.15%	77.50%	82.55%
Risk-free interest rate, minimum	1.81%	0.52%	1.81%
Risk-free interest rate, maximum	2.30%	0.82%	2.59%
Underlying common stock fair value	$ 6.22	$ 6.22	$ 5.15
Incentive Stock Options and Nonqualified Stock Options \| Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	5 years 9 months 21 days	5 years 4 months 17 days	5 years
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

Equity Incentive Plans and Stock-Based Compensation - Summary of Option Activity Under the 2015 Plan (Details) - 2015 Equity Incentive Plan - Incentive Stock Options and Nonqualified Stock Options - USD ($)	6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Options, Outstanding, Beginning balance	1,337,501	113,174	113,174
Number of Options, Granted	1,275,202	1,166,398
Number of Options, Exercised	(81,996)	(21,940)
Number of Options, Forfeited	(708)	(2,010)
Number of Options, Outstanding, Ending balance	2,529,999	1,255,622	1,337,501	113,174
Number of Options, Exercisable	459,864	97,942
Number of Options, Vested and expected to vest	2,529,999	1,255,622
Weighted- Average Exercise Price per Share, Outstanding, Beginning balance	$ 3.22	$ 2.08	$ 2.08
Weighted- Average Exercise Price per Share, Granted	6.22	2.86
Weighted- Average Exercise Price per Share, Exercised	2.47	6.01
Weighted- Average Exercise Price per Share, Forfeited	2.08	2.08
Weighted- Average Exercise Price per Share, Outstanding, Ending balance	4.76	2.79	$ 3.22	$ 2.08
Weighted- Average Exercise Price per Share, Exercisable	3.39	2.79
Weighted- Average Exercise Price per Share, Vested and expected to vest	$ 4.76	$ 2.79
Weighted- Average Remaining Contractual Term (in Years), Outstanding	9 years 2 months 19 days	9 years 7 months 6 days	9 years 2 months 4 days	9 years 9 months 7 days
Weighted- Average Remaining Contractual Term (in Years), Exercisable	8 years 9 months 14 days	9 years 6 months 18 days
Weighted- Average Remaining Contractual Term (in Years), Vested and expected to vest	9 years 2 months 19 days	9 years 7 months 6 days
Aggregate Intrinsic Value, Outstanding balance	$ 70,079	$ 5,341	$ 5,157	$ 348
Aggregate Intrinsic Value, Exercisable	13,367	379
Aggregate Intrinsic Value, Vested and expected to vest	$ 70,079	$ 5,431

Equity Incentive Plans and Stock-Based Compensation - Summary of Components and Classification of Stock-based Compensation Expense for Stock-based Awards (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	$ 786	$ 506	$ 1,211	$ 818
Restricted Stock Awards and Founders' Common Stock Awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	51	68	109	144
Exercises of Outstanding Stock Option Awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	735	438	1,102	674
Research and Development Expenses
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	287	136	451	225
General and Administrative Expenses
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	$ 499	$ 370	$ 760	$ 593

Equity Incentive Plans and Stock-Based Compensation - Stock-Based Compensation Expense - Additional Information (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Restricted Stock Awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation cost	$ 0.3	$ 0.6
Unrecognized compensation expense, weighted average period	1 year 8 months 12 days	2 years 7 months 13 days
Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation expense, weighted average period	2 years 9 months 10 days	3 years 6 months 14 days
Unrecognized compensation cost	$ 8.3	$ 4.7

Equity Incentive Plans and Stock-Based Compensation - 2020 Employee Stock Purchase Plan - Additional Information (Details) - USD ($)	1 Months Ended	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total shares reserved for future issuance	7,429,999	7,429,999		7,429,999		20,346,844
Stock-based compensation expense		$ 786,000	$ 506,000	$ 1,211,000	$ 818,000
Shares of Common Stock Available for Future Issuance under the 2020 ESPP
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total shares reserved for future issuance	700,000	700,000		700,000
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 (1) 1.0% of the total number of shares of common stock outstanding on December 31 of the preceding calendar year, (2) 700,000 shares or (3) such lesser amount as determined by the administrator of the 2020 ESPP, which is the compensation committee of the board of directors.
Common stock shares outstanding percentage	1.00%
Percentage of payroll deductions	15.00%	15.00%		15.00%
Employee stock purchase plan offering period				6 months
Stock-based compensation expense		$ 0		$ 0
Common stock fair market value percentage				85.00%
Number of common stock issued				0

Income Taxes - Additional Information (Details) - USD ($)		3 Months Ended		6 Months Ended
	Mar. 27, 2020	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Tax Disclosure [Abstract]
Income tax provision		$ 0	$ 0	$ 0	$ 0
Valuation allowance as a percentage on total deferred tax assets		100.00%		100.00%
Effective tax rate				0.00%
Tax relief period for net operating loss carryback	5 years
Suspension of annual deduction limitation of taxable income from net operating losses	80.00%

- Definition

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

+ References + Details

Commitments and Contingencies - Additional Information (Details) $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended
	Feb. 28, 2018 USD ($) ft²	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Loss Contingencies [Line Items]
Contractual arrangements cancellation period				30 days
Rent expenses and common area maintenance charges		$ 0.6	$ 0.6
Rent expense				$ 1.3	$ 1.3
California
Loss Contingencies [Line Items]
Leased premises under non cancelable operating lease \| ft²	32,974
Lease term	84 months
Operating lease description				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.
Base rent abated amount	$ 0.2
Lease term extension period		7 years		7 years
California \| Minimum [Member]
Loss Contingencies [Line Items]
Lease term extension notice period				9 months
California \| Maximum
Loss Contingencies [Line Items]
Lease term extension notice period				12 months
California \| Other Non-current Assets
Loss Contingencies [Line Items]
Refundable security deposit		$ 0.4		$ 0.4		$ 0.4

Commitments and Contingencies - Schedule of Future Minimum Payments (Details) $ in Thousands	Jun. 30, 2020 USD ($)
Leases [Abstract]
2020 (remainder of the year)	$ 996
2021	2,027
2022	2,098
2023	2,171
2024 and beyond	3,390
Total	$ 10,682

Related Party Transactions - Additional Information (Details)	1 Months Ended		3 Months Ended		6 Months Ended
	Mar. 31, 2020 USD ($) shares	Oct. 31, 2019 USD ($) Research	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Dec. 31, 2019	Dec. 19, 2019 USD ($)
Novartis \| Novartis Agreement
Related Party Transaction [Line Items]
Charitable contribution		$ 69,600,000
Committed to provide equity financing		$ 30,000,000
Percentage of outstanding equity on fully diluted basis			6.10%		6.10%		7.40%
Maximum \| Novartis \| Novartis Agreement
Related Party Transaction [Line Items]
Number of Integrin research targets \| Research		3
Committed to provide equity financing		$ 30,000,000
IPO \| Novartis \| Novartis Agreement
Related Party Transaction [Line Items]
Committed to provide equity financing		10,000,000
Series C Redeemable Convertible Preferred Stock \| Novartis \| Novartis Agreement
Related Party Transaction [Line Items]
Committed to provide equity financing		$ 20,000,000						$ 20,000,000
Third Rock Ventures
Related Party Transaction [Line Items]
Consulting service expenses			$ 0		$ 0
Third Rock Ventures \| Non-employee Director \| Stock Options
Related Party Transaction [Line Items]
Option granted \| 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
Third Rock Ventures \| General and Administrative Expenses
Related Party Transaction [Line Items]
Consulting service expenses				$ 14,000		$ 26,000
UCSF Foundation
Related Party Transaction [Line Items]
Charitable contribution			$ 0	$ 400,000	$ 700,000	$ 400,000

Defined Contribution Plan - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Compensation And Retirement Disclosure [Abstract]
Payment made under defined contribution plan	$ 0.1	$ 0.1	$ 0.2	$ 0.1
Defined Contribution Plan, Plan Name [Extensible List]	plrx:FourZeroOneKPlanMember	plrx:FourZeroOneKPlanMember	plrx:FourZeroOneKPlanMember	plrx:FourZeroOneKPlanMember

Net Loss Per Share Attributable to Common Stockholders - Summary of Potentially Dilutive Securities Excluded from Computation of Diluted Net Loss Per Share (Details) - shares	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities excluded from computation of diluted net loss per share	2,732,085	16,500,650
Redeemable Convertible Preferred Stock (on an As-converted Basis)
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities excluded from computation of diluted net loss per share		14,755,415
Exercises of Outstanding Stock Option Awards
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities excluded from computation of diluted net loss per share	2,529,999	1,259,905
Restricted Stock Awards Granted and Not Purchased
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities excluded from computation of diluted net loss per share	4,195	4,195
Unvested Restricted Shares
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities excluded from computation of diluted net loss per share	197,891	474,329
Unvested Shares of Founders' Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities excluded from computation of diluted net loss per share		6,806

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	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Numerator
Net loss	$ (17,001)	$ 11,029	$ (15,522)	$ (14,023)	$ (5,972)	$ (29,545)
Add: accretion to redemption value and cumulative dividends on redeemable convertible preferred shares			(1,359)			(2,703)
Net loss attributable to common stockholders	$ (17,001)		$ (16,881)		$ (5,972)	$ (32,248)
Weighted-average common shares outstanding used to calculate net loss per share attributable to common stockholders:
Basic	12,253,943		1,559,942		7,062,780	1,486,109
Diluted	12,253,943		1,559,942		7,062,780	1,486,109
Net loss per share, attributable to common stockholders:
Basic	$ (1.39)		$ (10.82)		$ (0.85)	$ (21.70)
Diluted	$ (1.39)		$ (10.82)		$ (0.85)	$ (21.70)