RAPT Therapeutics (RAPT) 10-Q 11 May 22 2022 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2022	May 06, 2022
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2022
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q1
Trading Symbol	RAPT
Entity Registrant Name	RAPT Therapeutics, Inc.
Entity Central Index Key	0001673772
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Current Reporting Status	Yes
Entity Shell Company	false
Entity File Number	001-38997
Entity Tax Identification Number	47-3313701
Entity Address, Address Line One	561 Eccles 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	489-9000
Entity Common Stock, Shares Outstanding		29,644,130
Entity Interactive Data Current	Yes
Title of 12(b) Security	Common Stock $0.0001 par value per share
Security Exchange Name	NASDAQ
Entity Incorporation, State or Country Code	DE
Document Quarterly Report	true
Document Transition Report	false

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 32,418	$ 24,027
Marketable securities	140,590	165,627
Prepaid expenses and other current assets	2,656	3,319
Total current assets	175,664	192,973
Property and equipment, net	2,629	2,741
Operating lease right-of-use assets	6,322
Other assets	2,933	2,922
Total assets	187,548	198,636
Current liabilities:
Accounts payable	1,936	1,999
Accrued expenses	8,276	6,326
Deferred revenue, current	645	1,016
Operating lease liabilities, current	1,481
Other current liabilities	22	254
Total current liabilities	12,360	9,595
Deferred rent, net of current portion		2,150
Deferred revenue, non-current	241	511
Operating lease liabilities, non-current	7,112
Total liabilities	19,713	12,256
Commitments
Stockholders' equity:
Preferred stock
Common stock	3	3
Additional paid-in capital	473,463	470,629
Accumulated other comprehensive loss	(1,117)	(206)
Accumulated deficit	(304,514)	(284,046)
Total stockholders' equity	167,835	186,380
Total liabilities and stockholders' equity	$ 187,548	$ 198,636

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Income Statement [Abstract]
Revenue	$ 641	$ 1,222
Operating expenses:
Research and development	16,670	13,771
General and administrative	4,748	4,012
Total operating expenses	21,418	17,783
Loss from operations	(20,777)	(16,561)
Other income, net	309	47
Net loss	(20,468)	(16,514)
Other comprehensive income (loss):
Foreign currency translation gain (loss)	(201)	38
Unrealized loss on marketable securities	(710)	(50)
Total comprehensive loss	$ (21,379)	$ (16,526)
Net loss per share, basic and diluted	$ (0.69)	$ (0.66)
Weighted average number of shares used in computing net loss per share, basic and diluted	29,572,467	24,844,946

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited) - USD ($) $ in Thousands	Total	At The Market	Common Stock	Common StockAt The Market	Additional Paid-In Capital	Additional Paid-In CapitalAt The Market	Accumulated Other Comprehensive Loss	Accumulated Deficit
Beginning balance at Dec. 31, 2020	$ 104,179		$ 2		$ 319,196		$ (177)	$ (214,842)
Beginning balance, shares at Dec. 31, 2020			24,773,361
Proceeds from issuance of common stock, net of issuance costs		$ 1,180				$ 1,180
Proceeds from issuance of common stock, net of issuance costs, shares				57,100
Issuances from employee stock plans	121				121
Issuances from employee stock plans, shares			31,620
Stock-based compensation	2,687				2,687
Foreign currency translation gain (loss)	38						38
Unrealized loss on marketable securities	(50)						(50)
Net loss	(16,514)							(16,514)
Ending balance at Mar. 31, 2021	91,641		$ 2		323,184		(189)	(231,356)
Ending balance, shares at Mar. 31, 2021			24,862,081
Beginning balance at Dec. 31, 2021	186,380		$ 3		470,629		(206)	(284,046)
Beginning balance, shares at Dec. 31, 2021			29,555,119
Issuances from employee stock plans	132				132
Issuances from employee stock plans, shares			37,640
Stock-based compensation	2,702				2,702
Foreign currency translation gain (loss)	(201)						(201)
Unrealized loss on marketable securities	(710)						(710)
Net loss	(20,468)							(20,468)
Ending balance at Mar. 31, 2022	$ 167,835		$ 3		$ 473,463		$ (1,117)	$ (304,514)
Ending balance, shares at Mar. 31, 2022			29,592,759

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Operating activities
Net loss	$ (20,468)	$ (16,514)
Adjustments to reconcile net loss to net cash used in operating activities:
Amortization of premium on marketable securities	341	218
Depreciation and amortization	261	280
Stock-based compensation expense	2,702	2,687
Gain (loss) on foreign currency translation	(201)	38
Non-cash operating lease expense	428	0
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	652	(112)
Accounts payable, accrued expenses and other current liabilities	1,891	362
Deferred revenue	(641)	(841)
Deferred rent	0	(28)
Operating lease liabilities	(543)	0
Net cash used in operating activities	(15,578)	(13,910)
Investing activities
Purchase of marketable securities	(6,055)	(15,734)
Proceeds from maturities of marketable securities	30,041	28,372
Purchase of property and equipment	(149)	(227)
Net cash provided by investing activities	23,837	12,411
Financing activities
Proceeds from issuance of common stock under employee stock plans	132	121
Net cash provided by financing activities	132	1,301
Net increase (decrease) in cash and cash equivalents	8,391	(198)
Cash and cash equivalents at beginning of period	24,027	24,918
Cash and cash equivalents at end of period	32,418	24,720
Supplemental disclosures of non-cash investing and financing information
Right-of-use asset obtained in exchange for lease obligation	(6,585)	0
At The Market
Financing activities
Proceeds from issuance of common stock, net of issuance costs	$ 0	$ 1,180

Organization

Organization	3 Months Ended
	Mar. 31, 2022
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Organization	1. Organization Description of the Business RAPT Therapeutics, Inc. (“RAPT” or the “Company”) is a clinical-stage, immunology-based biopharmaceutical company focused on discovering, developing and commercializing oral small molecule therapies for patients with significant unmet needs in inflammatory diseases and oncology. Utilizing its proprietary drug discovery and development engine, the Company develops highly selective small molecules that are designed to modulate the critical immune responses underlying these diseases. The Company is located in South San Francisco, California.

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2022
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles ( “ ” ’ The accompanying consolidated financial statements have been prepared in accordance with U.S. GAAP and include the consolidated accounts of the Company and its wholly-owned subsidiary, RAPT Therapeutics Australia Pty Ltd. All intercompany balances and transactions have been eliminated in consolidation. Revenue License and collaborative agreement revenue consists of license, milestone and royalty payments generated through agreements with strategic partners for the development and commercialization of certain product candidates. The terms of an agreement may include a non-refundable upfront fee, payments based upon achievement of milestones and royalties on net product sales. If a portion of the nonrefundable upfront fee or other payments received is allocated to continuing performance obligations under the terms of an agreement, such portion is recorded as deferred revenue and recognized as revenue when or as the underlying performance obligation is satisfied. The Company recognizes revenue when it transfers promised goods or services to customers or counterparties in an amount that reflects the consideration to which the Company expects to be entitled in exchange for those goods or services. In determining the appropriate amount of revenue to be recognized, the Company performs the following steps: (i) identification of the promised goods or services in the agreement; (ii) determination of whether the promised goods or services are performance obligations, including whether they are distinct in the context of the agreement; (iii) measurement of the transaction price, including any constraint on variable consideration; (iv) allocation of the transaction price to performance obligations based on estimated selling prices; and (v) recognition of revenue when or as the Company satisfies each performance obligation. Licenses: If a license to the Company’s intellectual property is determined to be distinct from the other performance obligations identified in an agreement, the Company will recognize revenue from the nonrefundable, upfront fee allocated to the license when the license is transferred to the licensee and the licensee is able to use and benefit from the license. If a license is bundled with other performance obligations, the Company utilizes judgment to assess the nature of the combined performance obligations to determine whether the combined performance obligations are satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. Milestone payments: If an agreement includes event-based or milestone payments, the Company evaluates whether the events or milestones are considered likely to be achieved and estimates the amount to be included in the transaction price using the most likely amount method. If it is unlikely that a significant revenue reversal would occur, the value of the associated event-based or milestone payments is included in the transaction price. Event-based or milestone payments that are not within the control of the Company are not included in the transaction price until they become likely to be achieved. Royalties: If an agreement includes sales-based royalties and the license is deemed to be the predominant item to which the royalties relate, the Company will recognize revenue at the later of (i) when the related sales occur or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied or partially satisfied. Stock-Based Compensation The Company measures stock-based compensation expense for all employee and non-employee stock-based awards based on their grant date fair value using the Black-Scholes option-pricing model. Subsequent to the adoption of ASU 2018-07, Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting The fair value of restricted stock awards granted after the Company’s initial public offering (“IPO”) is determined based on the stock price on the date of grant. The estimated fair value is amortized as compensation expense over the service period of the award. Stock-based compensation expense related to the Company’s employee stock purchase plan is recognized based on the fair value of each award estimated on the first day of the offering period using the Black‑Scholes option-pricing model and recorded as expense over the service period using the straight‑line method. Net Loss Per Share Basic net loss per share is computed by dividing the net loss by the weighted average number of common shares outstanding during the period, without consideration of potential dilutive securities. Diluted net loss per share is computed by dividing the net loss by the sum of the weighted average number of common shares outstanding during the period plus the number of potential dilutive securities outstanding during the period calculated in accordance with the treasury stock method. Diluted net loss per share is the same as basic net loss per share for all periods presented since the effect of including potential dilutive securities is anti-dilutive. Marketable Securities Marketable securities primarily consist of commercial paper, corporate bonds and U.S. government agency securities Leases At inception of a contract, the Company determines whether an arrangement is or contains a lease. For all leases, the Company determines the classification as either operating leases or financing leases. Operating leases are included in operating lease right-of-use (“ROU”) assets and operating lease liabilities in the Company’s Condensed Consolidated Balance Sheets. Lease recognition occurs at the commencement date and lease liability amounts are based on the present value of lease payments over the lease term. The lease term may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. The Company uses an implicit rate when readily available, or its incremental borrowing rate based on the information available at lease commencement date, in determining the present value of lease payments. ROU assets represent our right to use underlying assets for the lease term and operating lease liabilities represent our obligation to make lease payments under the lease. ROU assets also include any lease payments made prior to the commencement date and exclude lease incentives received. Operating lease expense is recognized on a straight-line basis over the lease term. Lease agreements with both lease and nonlease components are generally accounted for together as a single lease component . Recent Accounting Pronouncements From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (the “FASB”) or other standard setting bodies and adopted by the Company as of the specified effective date. Unless otherwise discussed, the impact of recently issued standards that are not yet effective will not have a material impact on the Company’s condensed consolidated financial statements upon adoption. Under the Jumpstart Our Business Startups Act of 2012, as amended (the “JOBS Act”), the Company meets the definition of an emerging growth company and has elected the extended transition period for complying with new or revised accounting standards pursuant to Section 107(b) of the JOBS Act. In June 2016, the FASB issued Accounting Standard Update (“ASU”) No. 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments Codification Improvements to Topic 326, Financial Instruments—Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments Financial Instruments—Credit Losses, Topic 326 Financial Instruments—Credit Losses (Topic 326), Derivatives and Hedging (Topic 815), and Leases (Topic 842): Effective Dates Codification Improvements to Topic 326, Financial Instruments—Credit Losses

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2022
Fair Value Disclosures [Abstract]
Fair Value Measurements	3. Fair Value Measurements Fair value accounting is applied for all financial assets and liabilities that are recognized or disclosed at fair value in the financial statements on a recurring basis. Financial instruments such as cash and cash equivalents, accounts payable and accrued liabilities approximate fair value due to their relatively short maturities. Assets and liabilities recorded at fair value on a recurring basis in the balance sheet are categorized based on the level of judgment associated with the inputs used to measure their fair values. Fair value is defined as the exchange price that would be received for an asset or an exit price that would be paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. The authoritative guidance on fair value measurements establishes a three-tier fair value hierarchy for disclosure of fair value measurements as follows: Level 1 — Level 2 — Level 3 — To date, the Company has not recorded any impairment charges on marketable securities due to other-than-temporary declines in market value. In determining whether a decline is other than temporary, the Company considers various factors, including the length of time and extent to which the market value has been less than amortized cost, the financial condition and near-term prospects of the issuer and the Company’s intent and ability to retain its investment in the issuer for a period of time sufficient to allow for any anticipated recovery in market value. The Company estimates the fair values of investments in corporate debt securities, commercial paper and U.S. government agency securities Cash equivalents and marketable securities, all of which are classified as available-for-sale securities and measured at fair value on a recurring basis, consisted of the following (in thousands): As of March 31, 2022 Fair Value Hierarchy Level Amortized Cost Unrealized Gains Unrealized Losses Fair Value Financial assets: Money market funds—classified as cash equivalents Level 1 $ 31,373 $ — $ — $ 31,373 Corporate debt Level 2 63,416 — (531 ) 62,885 Commercial paper Level 2 48,364 — — 48,364 U.S. government agency securities Level 2 29,755 — (414 ) 29,341 Total $ 172,908 $ — $ (945 ) $ 171,963 As of December 31, 2021 Fair Value Hierarchy Level Amortized Cost Unrealized Gains Unrealized Losses Fair Value Financial assets: Money market funds—classified as cash equivalents Level 1 $ 22,658 $ — $ — $ 22,658 Corporate debt Level 2 52,704 — (139 ) 52,565 Asset-backed securities Level 2 23,882 — (21 ) 23,861 Commercial paper Level 2 59,532 — — 59,532 U.S. government agency securities Level 2 29,744 — (75 ) 29,669 Total $ 188,520 $ — $ (235 ) $ 188,285 The Company does not intend to sell the securities that are in an unrealized loss position and the Company believes it is more likely than not that the investments will be held until recovery of the amortized cost bases. The Company has determined that the gross unrealized losses on marketable securities as of March 31, 2022 were temporary in nature. The following table presents the remaining contractual maturities of the Company’s marketable securities as of March 31, 2022 (in thousands): March 31, 2022 Due in less than one year $ 147,431 Due in more than one year 24,532 Total $ 171,963

Property and Equipment

Property and Equipment	3 Months Ended
	Mar. 31, 2022
Property Plant And Equipment [Abstract]
Property and Equipment	4. Property and Equipment Property and equipment consisted of the following (in thousands): March 31, December 31, 2022 2021 Laboratory equipment $ 6,399 $ 6,291 Leasehold improvements 3,295 3,295 Computer equipment 446 482 Furniture and fixtures 394 357 Total property and equipment 10,534 10,425 Less accumulated depreciation and amortization (7,905 ) (7,684 ) Property and equipment, net $ 2,629 $ 2,741 Depreciation and amortization expense was $0.3 million and $0.3 million for the three months ended March 31, 2022 and 2021, respectively.

Accrued Expenses

Accrued Expenses	3 Months Ended
	Mar. 31, 2022
Payables And Accruals [Abstract]
Accrued Expenses	5. Accrued Expenses Accrued expenses consisted of the following (in thousands): March 31, December 31, 2022 2021 Accrued research and development expenses $ 5,220 $ 2,205 Accrued compensation 2,359 3,652 Accrued professional and consulting services 580 415 Other 117 54 Total accrued expenses $ 8,276 $ 6,326

Leases

Leases	3 Months Ended
	Mar. 31, 2022
Leases [Abstract]
Leases	6. Leases The Company adopted ASU No. 2016-02, Leases (Topic 842) As a result of applying the modified retrospective approach to adopt the lease guidance, the following adjustments were made to accounts on the Condensed Consolidated Balance Sheet as of January 1, 2022 (in thousands): Balance Sheet December 31, 2021 Effect of adoption of ASC 842 January 1, 2022 Assets Operating lease right-of-use assets $ — $ 6,585 $ 6,585 Total assets $ — $ 6,585 $ 6,585 Liabilities Operating lease liabilities, current $ — $ 1,471 $ 1,471 Deferred rent (1) 2,386 (2,386 ) — Operating lease liabilities, non-current — 7,500 7,500 Total Lease Liabilities $ 2,386 $ 6,585 $ 8,971 (1) Included in other liabilities and deferred rent, net of current portion on the balance sheet. In May 2015, the Company entered into an operating lease for 30,376 square feet of laboratory and office facilities in South San Francisco, California, which expires in May 2022. In April 2018, the Company amended the lease agreement to include an additional 6,378 square feet of laboratory and office space increasing the total leased premises to 36,754 square feet. The lease amendment extended the lease term to November 2026 and contained scheduled rent increases over the lease term and an option for the Company to extend the lease for an additional five-year The Company does not have any financing lease agreements as of March 31, 2022. The following table summarizes maturities of operating lease liabilities as of March 31, 2022 (in thousands): 2022 (remaining nine months) $ 1,553 2023 2,109 2024 2,183 2025 2,259 2026 2,137 Thereafter — Total future undiscounted lease payments 10,241 Less: Imputed interest (1,648 ) Total Lease Liabilities $ 8,593 The following table summarizes the balance sheet classification of operating leases at March 31, 2022 (in thousands): Operating leases Operating lease right-of-use assets $ 6,322 Operating lease liabilities, current 1,481 Operating lease liabilities, non-current 7,112 Total operating lease liabilities $ 8,593 For the three months ended March 31, 2022, the Company incurred $0.4 million of lease expense included in operating expenses in the condensed consolidated statement of operations in relation to the operating lease. Variable lease expense was $0.1 million for the three months ended March 31, 2022. Rent expense was $0.6 million during the three months ended March 31, 2021. Cash paid for amounts included in the measurement of operating lease liabilities for the three months ended March 31, 2022 was $0.5 million and was included in net cash used in operating activities in the Company’s condensed consolidated statements of cash flows. As of March 31, 2022, the weighted-average remaining lease term and discount rate for the Company’s operating leases was 4.58 years and 8.0%, respectively.

Collaboration Agreements

Collaboration Agreements	3 Months Ended
	Mar. 31, 2022
Collaboration Agreements [Abstract]
Collaboration Agreements	7. Collaboration Agreements Collaboration and License Agreement with Hanmi In December 2019, the Company entered into a Collaboration and License Agreement (the “Hanmi Agreement”) with Hanmi Pharmaceutical Ltd. (“Hanmi”), pursuant to which the Company granted Hanmi an exclusive license to develop, manufacture and commercialize FLX475 and related compounds and products with respect to human cancers in the Republic of Korea, the Republic of China (Taiwan) and the People’s Republic of China, including the special administrative regions of Macau and Hong Kong (the “Hanmi Territory”), and certain sublicense In consideration of the rights granted under the Hanmi Agreement, the Company was entitled to $10.0 million in an upfront payment of $4.0 million and a near-term milestone payment of $6.0 million. The milestone payment was received in April 2020. Additionally, the Company will be eligible to receive contingent payments of up to $108.0 million upon the achievement of specified milestones, as well as double-digit royalties on future net sales of FLX475 in the Hanmi Territory. The transaction price as of March 31, 2022 was $10.4 million, consisting of the upfront fee of $4.0 million, the near-term milestone payment of $6.0 million and $0.4 million related to the supply of FLX475 to Hanmi. The Company recognizes revenue for the performance obligation by applying the cost-based input method over the estimated service period. The Company determined that this method most faithfully depicts the transfer of its performance obligations to Hanmi as it reflects the progress made towards providing Hanmi with the necessary know-how to continue developing FLX475 in the Hanmi Territory. For the three months ended March 31, 2022 and 2021, the Company recognized $0.6 million and $1.2 million, respectively, as revenue pursuant to the Hanmi Agreement. As of March 31, 2022 and December 31, 2021, deferred revenue related to the Hanmi Agreement was $0.9 million and $1.5 million, respectively. The deferred revenue is expected to be recognized over the estimated remaining period of the Company’s Phase 1/2 clinical trial of FLX475.

Common Stock

Common Stock	3 Months Ended
	Mar. 31, 2022
Equity [Abstract]
Common Stock	8. Common Stock As of March 31, 2022, the Company had reserved the following shares of common stock for future issuance: Options issued and outstanding under the 2019 Equity Incentive Plan and 2015 Stock Plan 2,764,372 Restricted stock units issued and outstanding under the 2019 Equity Incentive Plan 27,000 Options available for future grants under the 2019 Equity Incentive Plan 3,104,284 Shares reserved under the 2019 Employee Stock Purchase Plan 557,259 Total 6,452,915 As of March 31, 2022, there was up to $90.9 million available for future issuance of shares of common stock under the Controlled Equity Offering SM (the “ATM Sales Agreement”)

Stock-based Compensation

Stock-based Compensation	3 Months Ended
	Mar. 31, 2022
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-based Compensation	9. Stock-based Compensation Stock option activity under the 2019 Equity Incentive Plan (the “2019 Plan”) is set forth below for the three months ended March 31, 2022: Weighted Average Average Remaining Aggregate Number of Exercise Contractual Intrinsic Shares Price Per Term Value Outstanding Share (Years) (in thousands) Balances at December 31, 2021 2,024,681 $ 18.33 8.0 $ 38,417 Stock options authorized — Stock options granted 815,932 19.96 Stock options exercised (26,601 ) 7.83 Stock options forfeited (49,640 ) 23.90 Balances at March 31, 2022 2,764,372 $ 18.81 8.4 $ 14,075 As of March 31, 2022, 3,104,284 shares remained available for issuance under the 2019 Plan. Restricted stock unit (“RSU”) activity under the 2019 Plan is set forth below for the three months ended March 31, 2022: Weighted Average Number of Grant Date Shares Fair Value Outstanding Per Share Balances at December 31, 2021 40,500 $ 44.66 RSUs granted — — RSUs vested and settled (13,500 ) 44.66 RSUs forfeited — — Balances at March 31, 2022 27,000 $ 44.66 Stock-based compensation expense Total stock-based compensation expense recognized for options and RSUs granted to both employees and non-employees and for the employee stock purchase plan (“ESPP”) was as follows (in thousands): For the Three Months Ended March 31, 2022 2021 Research and development $ 1,179 $ 1,474 General and administrative 1,523 1,213 Total stock-based compensation expense $ 2,702 $ 2,687 As of March 31, 2022, unrecognized stock-based compensation expense related to outstanding unvested stock options and RSUs that are expected to vest was $24.5 million. This unrecognized stock-based compensation expense is expected to be recognized over 3.0 years. The Company recorded stock-based compensation expense related to the ESPP of $0.1

Net Loss Per Share

Net Loss Per Share	3 Months Ended
	Mar. 31, 2022
Earnings Per Share [Abstract]
Net Loss Per Share	10. Net Loss Per Share Net loss per share The following table sets forth the computation of the basic and diluted net loss per share for the three months ended March 31, 2022 and 2021 (in thousands, except share and per share data): Three Months Ended March 31, 2022 2021 Numerator: Net loss $ (20,468 ) $ (16,514 ) Denominator: Weighted-average shares used to compute net loss per share, basic and diluted 29,572,467 24,844,946 Net loss per share, basic and diluted $ (0.69 ) $ (0.66 ) Potential dilutive securities that were not included in the diluted per share calculations because they would be anti-dilutive were as follows: As of March 31, 2022 2021 Stock options issued and outstanding under the 2019 Equity Incentive Plan and 2015 Stock Plan 2,764,372 1,967,417 Estimated shares issuable under the 2019 ESPP 18,976 52,468 RSUs subject to future vesting 27,000 40,500 Total 2,810,348 2,060,385

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2022
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles ( “ ” ’ The accompanying consolidated financial statements have been prepared in accordance with U.S. GAAP and include the consolidated accounts of the Company and its wholly-owned subsidiary, RAPT Therapeutics Australia Pty Ltd. All intercompany balances and transactions have been eliminated in consolidation.
Revenue	Revenue License and collaborative agreement revenue consists of license, milestone and royalty payments generated through agreements with strategic partners for the development and commercialization of certain product candidates. The terms of an agreement may include a non-refundable upfront fee, payments based upon achievement of milestones and royalties on net product sales. If a portion of the nonrefundable upfront fee or other payments received is allocated to continuing performance obligations under the terms of an agreement, such portion is recorded as deferred revenue and recognized as revenue when or as the underlying performance obligation is satisfied. The Company recognizes revenue when it transfers promised goods or services to customers or counterparties in an amount that reflects the consideration to which the Company expects to be entitled in exchange for those goods or services. In determining the appropriate amount of revenue to be recognized, the Company performs the following steps: (i) identification of the promised goods or services in the agreement; (ii) determination of whether the promised goods or services are performance obligations, including whether they are distinct in the context of the agreement; (iii) measurement of the transaction price, including any constraint on variable consideration; (iv) allocation of the transaction price to performance obligations based on estimated selling prices; and (v) recognition of revenue when or as the Company satisfies each performance obligation. Licenses: If a license to the Company’s intellectual property is determined to be distinct from the other performance obligations identified in an agreement, the Company will recognize revenue from the nonrefundable, upfront fee allocated to the license when the license is transferred to the licensee and the licensee is able to use and benefit from the license. If a license is bundled with other performance obligations, the Company utilizes judgment to assess the nature of the combined performance obligations to determine whether the combined performance obligations are satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. Milestone payments: If an agreement includes event-based or milestone payments, the Company evaluates whether the events or milestones are considered likely to be achieved and estimates the amount to be included in the transaction price using the most likely amount method. If it is unlikely that a significant revenue reversal would occur, the value of the associated event-based or milestone payments is included in the transaction price. Event-based or milestone payments that are not within the control of the Company are not included in the transaction price until they become likely to be achieved. Royalties: If an agreement includes sales-based royalties and the license is deemed to be the predominant item to which the royalties relate, the Company will recognize revenue at the later of (i) when the related sales occur or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied or partially satisfied.
Stock-Based Compensation	Stock-Based Compensation The Company measures stock-based compensation expense for all employee and non-employee stock-based awards based on their grant date fair value using the Black-Scholes option-pricing model. Subsequent to the adoption of ASU 2018-07, Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting The fair value of restricted stock awards granted after the Company’s initial public offering (“IPO”) is determined based on the stock price on the date of grant. The estimated fair value is amortized as compensation expense over the service period of the award. Stock-based compensation expense related to the Company’s employee stock purchase plan is recognized based on the fair value of each award estimated on the first day of the offering period using the Black‑Scholes option-pricing model and recorded as expense over the service period using the straight‑line method.
Net Loss Per Share	Net Loss Per Share Basic net loss per share is computed by dividing the net loss by the weighted average number of common shares outstanding during the period, without consideration of potential dilutive securities. Diluted net loss per share is computed by dividing the net loss by the sum of the weighted average number of common shares outstanding during the period plus the number of potential dilutive securities outstanding during the period calculated in accordance with the treasury stock method. Diluted net loss per share is the same as basic net loss per share for all periods presented since the effect of including potential dilutive securities is anti-dilutive.
Marketable Securities	Marketable Securities Marketable securities primarily consist of commercial paper, corporate bonds and U.S. government agency securities
Leases	Leases At inception of a contract, the Company determines whether an arrangement is or contains a lease. For all leases, the Company determines the classification as either operating leases or financing leases. Operating leases are included in operating lease right-of-use (“ROU”) assets and operating lease liabilities in the Company’s Condensed Consolidated Balance Sheets. Lease recognition occurs at the commencement date and lease liability amounts are based on the present value of lease payments over the lease term. The lease term may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. The Company uses an implicit rate when readily available, or its incremental borrowing rate based on the information available at lease commencement date, in determining the present value of lease payments. ROU assets represent our right to use underlying assets for the lease term and operating lease liabilities represent our obligation to make lease payments under the lease. ROU assets also include any lease payments made prior to the commencement date and exclude lease incentives received. Operating lease expense is recognized on a straight-line basis over the lease term. Lease agreements with both lease and nonlease components are generally accounted for together as a single lease component .
Recent Accounting Pronouncements	Recent Accounting Pronouncements From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (the “FASB”) or other standard setting bodies and adopted by the Company as of the specified effective date. Unless otherwise discussed, the impact of recently issued standards that are not yet effective will not have a material impact on the Company’s condensed consolidated financial statements upon adoption. Under the Jumpstart Our Business Startups Act of 2012, as amended (the “JOBS Act”), the Company meets the definition of an emerging growth company and has elected the extended transition period for complying with new or revised accounting standards pursuant to Section 107(b) of the JOBS Act. In June 2016, the FASB issued Accounting Standard Update (“ASU”) No. 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments Codification Improvements to Topic 326, Financial Instruments—Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments Financial Instruments—Credit Losses, Topic 326 Financial Instruments—Credit Losses (Topic 326), Derivatives and Hedging (Topic 815), and Leases (Topic 842): Effective Dates Codification Improvements to Topic 326, Financial Instruments—Credit Losses

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2022
Fair Value Disclosures [Abstract]
Schedule of Cash Equivalents and Marketable Securities Classified as Available-for-Sale Securities Measured at Fair Value on Recurring Basis	Cash equivalents and marketable securities, all of which are classified as available-for-sale securities and measured at fair value on a recurring basis, consisted of the following (in thousands): As of March 31, 2022 Fair Value Hierarchy Level Amortized Cost Unrealized Gains Unrealized Losses Fair Value Financial assets: Money market funds—classified as cash equivalents Level 1 $ 31,373 $ — $ — $ 31,373 Corporate debt Level 2 63,416 — (531 ) 62,885 Commercial paper Level 2 48,364 — — 48,364 U.S. government agency securities Level 2 29,755 — (414 ) 29,341 Total $ 172,908 $ — $ (945 ) $ 171,963 As of December 31, 2021 Fair Value Hierarchy Level Amortized Cost Unrealized Gains Unrealized Losses Fair Value Financial assets: Money market funds—classified as cash equivalents Level 1 $ 22,658 $ — $ — $ 22,658 Corporate debt Level 2 52,704 — (139 ) 52,565 Asset-backed securities Level 2 23,882 — (21 ) 23,861 Commercial paper Level 2 59,532 — — 59,532 U.S. government agency securities Level 2 29,744 — (75 ) 29,669 Total $ 188,520 $ — $ (235 ) $ 188,285
Schedule of Remaining Contractual Maturities of Marketable Securities	The following table presents the remaining contractual maturities of the Company’s marketable securities as of March 31, 2022 (in thousands): March 31, 2022 Due in less than one year $ 147,431 Due in more than one year 24,532 Total $ 171,963

Property and Equipment (Tables)

Property and Equipment (Tables)	3 Months Ended
	Mar. 31, 2022
Property Plant And Equipment [Abstract]
Schedule of Property and Equipment	Property and equipment consisted of the following (in thousands): March 31, December 31, 2022 2021 Laboratory equipment $ 6,399 $ 6,291 Leasehold improvements 3,295 3,295 Computer equipment 446 482 Furniture and fixtures 394 357 Total property and equipment 10,534 10,425 Less accumulated depreciation and amortization (7,905 ) (7,684 ) Property and equipment, net $ 2,629 $ 2,741

Accrued Expenses (Tables)

Accrued Expenses (Tables)	3 Months Ended
	Mar. 31, 2022
Payables And Accruals [Abstract]
Schedule of Accrued Expenses	Accrued expenses consisted of the following (in thousands): March 31, December 31, 2022 2021 Accrued research and development expenses $ 5,220 $ 2,205 Accrued compensation 2,359 3,652 Accrued professional and consulting services 580 415 Other 117 54 Total accrued expenses $ 8,276 $ 6,326

Leases (Tables)

Leases (Tables)	3 Months Ended
	Mar. 31, 2022
Leases [Abstract]
Summary of Balance Sheets Adjustments Related to Lease Accounting Standard Update	As a result of applying the modified retrospective approach to adopt the lease guidance, the following adjustments were made to accounts on the Condensed Consolidated Balance Sheet as of January 1, 2022 (in thousands): Balance Sheet December 31, 2021 Effect of adoption of ASC 842 January 1, 2022 Assets Operating lease right-of-use assets $ — $ 6,585 $ 6,585 Total assets $ — $ 6,585 $ 6,585 Liabilities Operating lease liabilities, current $ — $ 1,471 $ 1,471 Deferred rent (1) 2,386 (2,386 ) — Operating lease liabilities, non-current — 7,500 7,500 Total Lease Liabilities $ 2,386 $ 6,585 $ 8,971 (1) Included in other liabilities and deferred rent, net of current portion on the balance sheet.
Summary of Maturities of Lease Liabilities	The following table summarizes maturities of operating lease liabilities as of March 31, 2022 (in thousands): 2022 (remaining nine months) $ 1,553 2023 2,109 2024 2,183 2025 2,259 2026 2,137 Thereafter — Total future undiscounted lease payments 10,241 Less: Imputed interest (1,648 ) Total Lease Liabilities $ 8,593
Summary of Balance Sheet Classification of Leases	The following table summarizes the balance sheet classification of operating leases at March 31, 2022 (in thousands): Operating leases Operating lease right-of-use assets $ 6,322 Operating lease liabilities, current 1,481 Operating lease liabilities, non-current 7,112 Total operating lease liabilities $ 8,593

Common Stock (Tables)

Common Stock (Tables)	3 Months Ended
	Mar. 31, 2022
Equity [Abstract]
Summary of Reserved Shares of Common Stock for Future Issuance	As of March 31, 2022, the Company had reserved the following shares of common stock for future issuance: Options issued and outstanding under the 2019 Equity Incentive Plan and 2015 Stock Plan 2,764,372 Restricted stock units issued and outstanding under the 2019 Equity Incentive Plan 27,000 Options available for future grants under the 2019 Equity Incentive Plan 3,104,284 Shares reserved under the 2019 Employee Stock Purchase Plan 557,259 Total 6,452,915

Stock-based Compensation (Table

Stock-based Compensation (Tables)	3 Months Ended
	Mar. 31, 2022
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Stock Option Activity	Stock option activity under the 2019 Equity Incentive Plan (the “2019 Plan”) is set forth below for the three months ended March 31, 2022: Weighted Average Average Remaining Aggregate Number of Exercise Contractual Intrinsic Shares Price Per Term Value Outstanding Share (Years) (in thousands) Balances at December 31, 2021 2,024,681 $ 18.33 8.0 $ 38,417 Stock options authorized — Stock options granted 815,932 19.96 Stock options exercised (26,601 ) 7.83 Stock options forfeited (49,640 ) 23.90 Balances at March 31, 2022 2,764,372 $ 18.81 8.4 $ 14,075
Summary of RSU Activity	Restricted stock unit (“RSU”) activity under the 2019 Plan is set forth below for the three months ended March 31, 2022: Weighted Average Number of Grant Date Shares Fair Value Outstanding Per Share Balances at December 31, 2021 40,500 $ 44.66 RSUs granted — — RSUs vested and settled (13,500 ) 44.66 RSUs forfeited — — Balances at March 31, 2022 27,000 $ 44.66
Summary of Stock-based Compensation Expense	Total stock-based compensation expense recognized for options and RSUs granted to both employees and non-employees and for the employee stock purchase plan (“ESPP”) was as follows (in thousands): For the Three Months Ended March 31, 2022 2021 Research and development $ 1,179 $ 1,474 General and administrative 1,523 1,213 Total stock-based compensation expense $ 2,702 $ 2,687

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	3 Months Ended
	Mar. 31, 2022
Earnings Per Share [Abstract]
Computation of Basic and Diluted Net Loss per Share	The following table sets forth the computation of the basic and diluted net loss per share for the three months ended March 31, 2022 and 2021 (in thousands, except share and per share data): Three Months Ended March 31, 2022 2021 Numerator: Net loss $ (20,468 ) $ (16,514 ) Denominator: Weighted-average shares used to compute net loss per share, basic and diluted 29,572,467 24,844,946 Net loss per share, basic and diluted $ (0.69 ) $ (0.66 )
Potential Dilutive Securities not Included in Diluted per Share Calculations	Potential dilutive securities that were not included in the diluted per share calculations because they would be anti-dilutive were as follows: As of March 31, 2022 2021 Stock options issued and outstanding under the 2019 Equity Incentive Plan and 2015 Stock Plan 2,764,372 1,967,417 Estimated shares issuable under the 2019 ESPP 18,976 52,468 RSUs subject to future vesting 27,000 40,500 Total 2,810,348 2,060,385

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Cash Equivalents and Marketable Securities Classified as Available-for-Sale Securities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 172,908	$ 188,520
Unrealized Losses	(945)	(235)
Fair Value	171,963	188,285
Level 1 | Money Market Funds | Cash Equivalents
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	31,373	22,658
Fair Value	31,373	22,658
Level 2 | Corporate Debt
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	63,416	52,704
Unrealized Losses	(531)	(139)
Fair Value	62,885	52,565
Level 2 | Asset-backed Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost		23,882
Unrealized Losses		(21)
Fair Value		23,861
Level 2 | Commercial Paper
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	48,364	59,532
Fair Value	48,364	59,532
Level 2 | U.S. Government Agency Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	29,755	29,744
Unrealized Losses	(414)	(75)
Fair Value	$ 29,341	$ 29,669

Fair Value Measurements - Sch_2

Fair Value Measurements - Schedule of Remaining Contractual Maturities of Marketable Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Investments Debt And Equity Securities [Abstract]
Due in less than one year	$ 147,431
Due in more than one year	24,532
Total	$ 171,963	$ 188,285

Property and Equipment - Schedu

Property and Equipment - Schedule of Property and Equipment (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Property Plant And Equipment [Line Items]
Total property and equipment	$ 10,534	$ 10,425
Less accumulated depreciation and amortization	(7,905)	(7,684)
Property and equipment, net	2,629	2,741
Laboratory Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	6,399	6,291
Leasehold Improvements
Property Plant And Equipment [Line Items]
Total property and equipment	3,295	3,295
Computer Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	446	482
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Total property and equipment	$ 394	$ 357

Property and Equipment - Additi

Property and Equipment - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Property Plant And Equipment [Abstract]
Depreciation and amortization expense	$ 261	$ 280

Accrued Expenses - Schedule of

Accrued Expenses - Schedule of Accrued Expenses (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Payables And Accruals [Abstract]
Accrued research and development expenses	$ 5,220	$ 2,205
Accrued compensation	2,359	3,652
Accrued professional and consulting services	580	415
Other	117	54
Total accrued expenses	$ 8,276	$ 6,326

Leases - Summary of Balance She

Leases - Summary of Balance Sheets Adjustments Related to Lease Accounting Standard Update (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Jan. 01, 2022	Dec. 31, 2021
Lessee Lease Description [Line Items]
Operating lease right-of-use assets	$ 6,322
Total assets	187,548		$ 198,636
Operating lease liabilities, current	1,481
Operating lease liabilities, non-current	7,112
Total liabilities	$ 19,713		12,256
ASC 842
Lessee Lease Description [Line Items]
Operating lease right-of-use assets		$ 6,585
Total assets		6,585
Operating lease liabilities, current		1,471
Operating lease liabilities, non-current		7,500
Total liabilities		8,971
ASC 842 | Previously Reported
Lessee Lease Description [Line Items]
Deferred rent (1)			2,386
Total liabilities			$ 2,386
ASC 842 | Effect of adoption of ASC 842
Lessee Lease Description [Line Items]
Operating lease right-of-use assets		6,585
Total assets		6,585
Operating lease liabilities, current		1,471
Deferred rent (1)		(2,386)
Operating lease liabilities, non-current		7,500
Total liabilities		$ 6,585

Leases - Additional Information

Leases - Additional Information (Details) $ in Millions	1 Months Ended		3 Months Ended
	Apr. 30, 2018ft²	May 31, 2015ft²	Mar. 31, 2022USD ($)	Mar. 31, 2021USD ($)
Lessee Lease Description [Line Items]
Lease expiration period		2022-05
Additional laboratory and office facilities under lease | ft²	6,378
Increased of leased premises | ft²	36,754
Lessee operating lease extended lease term	2026-11
Lease existence of option to extend		true
Lessee operating lease option to extend		5 years
Lease expense | $			$ 0.4	$ 0.6
Variable lease expense | $			0.1
Cash paid for operating lease liabilities | $			$ 0.5
Operating lease, weighted average remaining lease term			4 years 6 months 29 days
Operating lease, weighted average discount rate, percent			8.00%
South San Francisco and California
Lessee Lease Description [Line Items]
Laboratory and office facilities under lease | ft²		30,376

Leases - Summary of Maturities

Leases - Summary of Maturities of Lease Liabilities (Details) $ in Thousands	Mar. 31, 2022USD ($)
Leases [Abstract]
2022 (remaining nine months)	$ 1,553
2023	2,109
2024	2,183
2025	2,259
2026	2,137
Total future undiscounted lease payments	10,241
Less: Imputed interest	(1,648)
Total Lease Liabilities	$ 8,593

Leases - Summary of Balance S_2

Leases - Summary of Balance Sheet Classification of Leases (Details) $ in Thousands	Mar. 31, 2022USD ($)
Leases [Abstract]
Operating lease right-of-use assets	$ 6,322
Operating lease liabilities, current	1,481
Operating lease liabilities, non-current	7,112
Total operating lease liabilities	$ 8,593

Collaboration Agreements - Addi

Collaboration Agreements - Additional Information (Details) - USD ($)	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021	Apr. 30, 2020	Dec. 31, 2019
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue recognized	$ 641,000	$ 1,222,000
Collaboration and License Agreement | Hanmi Pharmaceutical Co., LTD
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront and near-term milestone payment	10,400,000				$ 10,000,000
Upfront fee	4,000,000				4,000,000
Milestone payment	6,000,000			$ 6,000,000
Milestone payment related to supply	400,000
Revenue recognized	600,000	$ 1,200,000
Deferred revenue	$ 900,000		$ 1,500,000
Collaboration and License Agreement | Hanmi Pharmaceutical Co., LTD | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contingent payments upon achievement of specified milestones					$ 108,000,000

Common Stock - Summary of Reser

Common Stock - Summary of Reserved Shares of Common Stock for Future Issuance (Detail)	Mar. 31, 2022shares
Class Of Stock [Line Items]
Total shares reserved	6,452,915
2019 Equity Incentive Plan and 2015 Stock Plan | Options Issued and Outstanding
Class Of Stock [Line Items]
Total shares reserved	2,764,372
2019 Equity Incentive Plan | Restricted Stock Units Issued and Outstanding
Class Of Stock [Line Items]
Total shares reserved	27,000
2019 Equity Incentive Plan | Options Available for Future Grants
Class Of Stock [Line Items]
Total shares reserved	3,104,284
2019 Employee Stock Purchase Plan
Class Of Stock [Line Items]
Total shares reserved	557,259

Common Stock - Additional Infor

Common Stock - Additional Information (Details) $ in Millions	Mar. 31, 2022USD ($)
ATM Sales Agreement
Class Of Stock [Line Items]
Common stock available for future issuance value	$ 90.9

Stock-based Compensation - Summ

Stock-based Compensation - Summary of Stock Option Activity (Details) - 2019 Plan - Share-based Payment Arrangement, Option - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Shares Outstanding, Beginning Balance	2,024,681
Number of Shares Outstanding, Stock options granted	815,932
Number of Shares Outstanding, Stock options exercised	(26,601)
Number of Shares Outstanding, Stock options forfeited	(49,640)
Number of Shares Outstanding, Ending Balance	2,764,372	2,024,681
Weighted Average Exercise Price Per Share, Beginning Balance	$ 18.33
Weighted Average Exercise Price Per Share, Stock options granted	19.96
Weighted Average Exercise Price Per Share, Stock options exercised	7.83
Weighted Average Exercise Price Per Share, Stock options forfeited	23.90
Weighted Average Exercise Price Per Share, Ending Balance	$ 18.81	$ 18.33
Average Remaining Contractual Term (Years), Balance	8 years 4 months 24 days	8 years
Aggregate Intrinsic Value	$ 14,075	$ 38,417

Stock-based Compensation - Addi

Stock-based Compensation - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized stock-based compensation cost related to outstanding unvested stock options that are expected to vest	$ 24,500
Unrecognized stock-based compensation cost, expected period to be recognized	3 years
Stock-based compensation expense	$ 2,702	$ 2,687
2019 ESPP
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 100	$ 800
2019 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares remained available for issuance	3,104,284

Stock-based Compensation - Su_2

Stock-based Compensation - Summary of RSU Activity (Details) - 2019 Plan - Restricted Stock Unit ("RSU")	3 Months Ended
	Mar. 31, 2022$ / sharesshares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Shares Outstanding, Beginning Balance | shares	40,500
Number of Shares Outstanding, RSUs vested and settled | shares	(13,500)
Number of Shares Outstanding, Ending Balance | shares	27,000
Weighted Average Grant Date Fair Value Per Share, Beginning Balance | $ / shares	$ 44.66
Weighted Average Grant Date Fair Value Per Share, RSUs vested and settled | $ / shares	44.66
Weighted Average Grant Date Fair Value Per Share, Ending Balance | $ / shares	$ 44.66

Stock-based Compensation - Su_3

Stock-based Compensation - Summary of Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 2,702	$ 2,687
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	1,179	1,474
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 1,523	$ 1,213

Net Loss Per Share - Computatio

Net Loss Per Share - Computation of Basic and Diluted Net Loss per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Numerator:
Net loss	$ (20,468)	$ (16,514)
Denominator:
Weighted-average shares used to compute net loss per share, basic and diluted	29,572,467	24,844,946
Net loss per share, basic and diluted	$ (0.69)	$ (0.66)

Net Loss Per Share - Potential

Net Loss Per Share - Potential Dilutive Securities not Included in Diluted per Share Calculations (Details) - shares	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potential dilutive securities	2,810,348	2,060,385
Stock Options Issued And Outstanding Equity Incentive Plan And Under 2019 Equity Incentive Plan And 2015 Stock Plan
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potential dilutive securities	2,764,372	1,967,417
Estimated Shares Issuable Under Employee Stock Purchase Plan
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potential dilutive securities	18,976	52,468
RSUs Subject to Future Vesting
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potential dilutive securities	27,000	40,500