RAPT Therapeutics (RAPT) 10-Q 11 Aug 23 2023 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2023	Aug. 03, 2023
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2023
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	Q2
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		34,358,152
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	Jun. 30, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 50,164	$ 38,946
Marketable securities	154,834	210,122
Prepaid expenses and other current assets	2,419	3,626
Total current assets	207,417	252,694
Property and equipment, net	2,963	2,539
Operating lease right-of-use assets	6,103	6,940
Other assets	4,273	4,036
Total assets	220,756	266,209
Current liabilities:
Accounts payable	2,690	3,365
Accrued expenses	10,295	8,656
Operating lease liabilities, current	2,333	2,171
Other current liabilities	96	32
Total current liabilities	15,414	14,224
Operating lease liabilities, non-current	5,665	6,819
Total liabilities	21,079	21,043
Commitments and contingencies
Stockholders' equity:
Preferred stock
Common stock	3	3
Additional paid-in capital	622,289	613,073
Accumulated other comprehensive loss	(180)	(26)
Accumulated deficit	(422,435)	(367,884)
Total stockholders' equity	199,677	245,166
Total liabilities and stockholders' equity	$ 220,756	$ 266,209

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Income Statement [Abstract]
Revenue	$ 0	$ 886	$ 0	$ 1,527
Operating expenses:
Research and development	21,642	14,359	47,216	31,029
General and administrative	6,722	5,436	12,710	10,184
Total operating expenses	28,364	19,795	59,926	41,213
Loss from operations	(28,364)	(18,909)	(59,926)	(39,686)
Other income (expense), net	3,084	(275)	5,375	34
Net loss	(25,280)	(19,184)	(54,551)	(39,652)
Other comprehensive income (loss):
Foreign currency translation gain (loss)	(655)	550	(655)	349
Unrealized gain (loss) on marketable securities	136	(178)	501	(888)
Total comprehensive loss	$ (25,799)	$ (18,812)	$ (54,705)	$ (40,191)
Net loss per share, basic	$ (0.66)	$ (0.62)	$ (1.42)	$ (1.31)
Net loss per share, diluted	$ (0.66)	$ (0.62)	$ (1.42)	$ (1.31)
Weighted average number of shares used in computing net loss per share, basic	38,328,741	31,140,323	38,304,758	30,356,515
Weighted average number of shares used in computing net loss per share, diluted	38,328,741	31,140,323	38,304,758	30,356,515

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
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 of common stock under employee stock plans	132		132
Issuances of common stock under employee stock plans, shares		37,640
Stock-based compensation	2,702		2,702
Foreign currency translation loss	(201)			(201)
Unrealized gain (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
Beginning balance at Dec. 31, 2021	186,380	$ 3	470,629	(206)	(284,046)
Beginning balance, shares at Dec. 31, 2021		29,555,119
Foreign currency translation loss	349
Unrealized gain (loss) on marketable securities	(888)
Net loss	(39,652)
Ending balance at Jun. 30, 2022	202,133	$ 3	526,573	(745)	(323,698)
Ending balance, shares at Jun. 30, 2022		29,649,457
Beginning balance at Mar. 31, 2022	167,835	$ 3	473,463	(1,117)	(304,514)
Beginning balance, shares at Mar. 31, 2022		29,592,759
Proceeds from sale of pre-funded warrants in private placement, net of issuance costs	49,784		49,784
Issuances of common stock under employee stock plans	654		654
Issuances of common stock under employee stock plans, shares		56,698
Stock-based compensation	2,672		2,672
Foreign currency translation loss	550			550
Unrealized gain (loss) on marketable securities	(178)			(178)
Net loss	(19,184)				(19,184)
Ending balance at Jun. 30, 2022	202,133	$ 3	526,573	(745)	(323,698)
Ending balance, shares at Jun. 30, 2022		29,649,457
Beginning balance at Dec. 31, 2022	245,166	$ 3	613,073	(26)	(367,884)
Beginning balance, shares at Dec. 31, 2022		34,254,314
Issuances of common stock under employee stock plans	116		116
Issuances of common stock under employee stock plans, shares		35,417
Stock-based compensation	4,094		4,094
Unrealized gain (loss) on marketable securities	365			365
Net loss	(29,271)				(29,271)
Ending balance at Mar. 31, 2023	220,470	$ 3	617,283	339	(397,155)
Ending balance, shares at Mar. 31, 2023		34,289,731
Beginning balance at Dec. 31, 2022	245,166	$ 3	613,073	(26)	(367,884)
Beginning balance, shares at Dec. 31, 2022		34,254,314
Foreign currency translation loss	(655)
Unrealized gain (loss) on marketable securities	501
Net loss	(54,551)
Ending balance at Jun. 30, 2023	199,677	$ 3	622,289	(180)	(422,435)
Ending balance, shares at Jun. 30, 2023		34,352,076
Beginning balance at Mar. 31, 2023	220,470	$ 3	617,283	339	(397,155)
Beginning balance, shares at Mar. 31, 2023		34,289,731
Issuances of common stock under employee stock plans	767		767
Issuances of common stock under employee stock plans, shares		62,345
Stock-based compensation	4,239		4,239
Foreign currency translation loss	(655)			(655)
Unrealized gain (loss) on marketable securities	136			136
Net loss	(25,280)				(25,280)
Ending balance at Jun. 30, 2023	$ 199,677	$ 3	$ 622,289	$ (180)	$ (422,435)
Ending balance, shares at Jun. 30, 2023		34,352,076

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Operating activities
Net loss	$ (54,551)	$ (39,652)
Adjustments to reconcile net loss to net cash used in operating activities:
(Accretion of discounts) amortization of premium on marketable securities	(2,948)	507
Depreciation and amortization	568	535
Stock-based compensation expense	8,333	5,374
Gain (loss) on foreign currency translation	(655)	349
Non-cash operating lease expense	1,168	854
Changes in operating assets and liabilities:
Prepaid expenses and other assets	970	562
Accounts payable, accrued expenses and other current liabilities	1,028	3,300
Deferred revenue	0	(1,527)
Operating lease liabilities	(1,323)	(1,075)
Net cash used in operating activities	(47,410)	(30,773)
Investing activities
Purchase of marketable securities	(73,951)	(72,241)
Proceeds from maturities of marketable securities	132,688	86,335
Purchase of property and equipment	(992)	(715)
Net cash provided by investing activities	57,745	13,379
Financing activities
Proceeds from equity offerings, net of issuance costs		49,784
Proceeds from issuance of common stock under employee stock plans	883	786
Net cash provided by financing activities	883	50,570
Net increase in cash and cash equivalents	11,218	33,176
Cash and cash equivalents at beginning of period	38,946	24,027
Cash and cash equivalents at end of period	50,164	57,203
Supplemental disclosures of non-cash investing and financing information
Right-of-use asset obtained in exchange for lease obligation	$ 0	$ (6,585)

Organization

Organization	6 Months Ended
	Jun. 30, 2023
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 therapeutics 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	6 Months Ended
	Jun. 30, 2023
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 (“U.S. GAAP”) for interim financial information and pursuant to Article 10 of Regulation S‑X of the Securities Act of 1933, as amended (the “Securities Act”). Accordingly, they do not include all of the information and notes required by U.S. GAAP for complete financial statements. These unaudited condensed consolidated financial statements include only normal and recurring adjustments that the Company believes are necessary to fairly state the Company’s financial position and the results of its operations and cash flows. Interim-period results are not necessarily indicative of results of operations or cash flows for a full year or any subsequent interim period. The condensed consolidated balance sheet at December 31, 2022 has been derived from the audited financial statements at that date but does not include all disclosures required by U.S. GAAP for complete financial statements. Because all of the disclosures required by U.S. GAAP for complete financial statements are not included herein, these unaudited condensed consolidated financial statements and the notes accompanying them should be read in conjunction with the Company’s audited consolidated financial statements included in its Annual Report on Form 10-K for the year ended December 31, 2022 filed on March 14, 2023 with the Securities and Exchange Commission (“SEC”). The accompanying condensed 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., which was established in 2018 and deregistered during the quarter ended June 30, 2023. All intercompany balances and transactions have been eliminated in consolidation. Revenue License and collaborative agreements 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 of cumulative revenue recognized 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 are 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 when (i) the related sales occur or (ii) 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 determines employee, nonemployee and director stock-based compensation expense for all stock-based awards based on their grant date fair value using the Black-Scholes option-pricing model. For stock-based awards with service conditions only, stock-based compensation expense is recognized over the requisite service period using the straight-line method. Forfeitures are recognized as they occur. The fair value of restricted stock awards granted 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. 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 common 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 since the effect of potentially dilutive securities is anti-dilutive. Marketable Securities Marketable securities primarily consist of commercial paper, corporate debt securities and U.S. government agency securities. The Company has classified its marketable securities as available-for-sale and may sell these securities prior to their stated maturities. The Company views these marketable securities as available to support current operations and classifies marketable securities with maturities beyond 12 months as current assets. The Company’s marketable securities are carried at estimated fair value, which is derived from independent pricing sources based on quoted prices in active markets for similar securities. Unrealized gains and losses are reported as a component of accumulated other comprehensive income (loss). The amortized cost of marketable securities is adjusted for amortization of premiums and accretion of discounts to maturity, which is included in other income, net on the condensed consolidated statements of operations. All of the Company's available-for-sale investments are subject to a periodic impairment review. For each available-for-sale investment whose fair value is below its amortized cost, the Company determines if the impairment is a result of a credit-related loss or other factors using both quantitative and qualitative 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. If the impairment is a result of a credit-related loss, the Company recognizes an allowance for credit losses. If the impairment is not a result of a credit loss, the Company recognizes the loss in other comprehensive loss. 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 . Accounting Pronouncements Recently Adopted 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. 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 . ASU 2016-13 amended the guidance on reporting credit losses for assets held at amortized cost basis and available-for-sale debt securities. For available-for-sale debt securities, credit losses will be presented as an allowance rather than as a write-down. In November 2019, the FASB issued ASU No. 2019-10, Financial Instruments—Credit Losses (Topic 326), Derivatives and Hedging (Topic 815), and Leases (Topic 842): Effective Dates and ASU No. 2019-11, Codification Improvements to Topic 326, Financial Instruments—Credit Losses , which defers the effective date of ASU 2016-13 for smaller report companies. ASU 2016-13 is effective for the Company’s fiscal year beginning January 1, 2023 . The adoption of ASU 2016-13 did not have a material impact on the Company's condensed consolidated financial statements and related disclosures.

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2023
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 (at least annually). Financial instruments include cash and cash equivalents, marketable securities, accounts payable and accrued expenses that 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 upon 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—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 estimates the fair values of investments in corporate debt securities, commercial paper and U.S. government agency securities using valuations obtained from third-party pricing services. The pricing services utilize industry standard valuation models, including both income and market-based approaches, for which all significant inputs are observable, either directly or indirectly, to estimate fair value. These inputs include reported trades of and broker/dealer quotes on the same or similar securities, issuer credit spreads, benchmark securities, prepayment/default projections based on historical data and other observable inputs. 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 June 30, 2023 Fair Value Amortized Unrealized Unrealized Fair Financial assets: Money market funds Level 1 $ 50,106 $ — $ — $ 50,106 Corporate debt Level 2 32,299 — ( 89 ) 32,210 Commercial paper Level 2 47,834 — — 47,834 U.S. government agency securities Level 2 74,881 3 ( 94 ) 74,790 Subtotal 205,120 3 ( 183 ) 204,940 Less: Cash equivalents ( 50,106 ) — — ( 50,106 ) Marketable securities $ 155,014 $ 3 $ ( 183 ) $ 154,834 As of December 31, 2022 Fair Value Amortized Unrealized Unrealized Fair Financial assets: Money market funds Level 1 $ 38,658 $ — $ — $ 38,658 Corporate debt Level 2 71,149 30 ( 284 ) 70,895 Asset-backed securities Level 2 105 — ( 1 ) 104 Commercial paper Level 2 71,328 — — 71,328 U.S. government agency securities Level 2 68,221 15 ( 441 ) 67,795 Subtotal 249,461 45 ( 726 ) 248,780 Less: Cash equivalents ( 38,658 ) — — ( 38,658 ) Marketable securities $ 210,803 $ 45 $ ( 726 ) $ 210,122 As of June 30, 2023, the unrealized losses on the Company’s securities that were in an unrealized loss position were caused by interest rate changes and were not attributable to credit losses. 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 did no t record an allowance for credit losses or other impairment charges related to its marketable securities as of June 30, 2023. The following table presents the remaining contractual maturities of the Company’s marketable securities as of June 30, 2023 (in thousands): June 30, 2023 Maturing in one year or less $ 151,859 Maturing after one year through five years 2,975 Total $ 154,834

Property and Equipment

Property and Equipment	6 Months Ended
	Jun. 30, 2023
Property, Plant and Equipment [Abstract]
Property and Equipment	4. Property and Equipment Property and equipment consisted of the following (in thousands): June 30, December 31, 2023 2022 Laboratory equipment $ 7,398 $ 6,558 Leasehold improvements 3,295 3,295 Computer equipment 617 578 Furniture and fixtures 394 357 Total property and equipment 11,704 10,788 Less accumulated depreciation and amortization ( 8,741 ) ( 8,249 ) Property and equipment, net $ 2,963 $ 2,539 Depreciation and amortization expense was $ 0.3 million and $ 0.2 million for the three months ended June 30, 2023 and 2022 , and $ 0.6 million and $ 0.5 million for the six months ended June 30, 2023 and 2022 , respectively.

Accrued Expenses

Accrued Expenses	6 Months Ended
	Jun. 30, 2023
Payables and Accruals [Abstract]
Accrued Expenses	5. Accrued Expenses Accrued expenses consisted of the following (in thousands): June 30, December 31, 2023 2022 Accrued research and development expenses $ 5,659 $ 3,473 Accrued compensation 3,971 4,618 Accrued professional and consulting services 480 327 Other 185 238 Total accrued expenses $ 10,295 $ 8,656

Leases

Leases	6 Months Ended
	Jun. 30, 2023
Leases [Abstract]
Leases	6. Leases 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. 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 term. In November 2022, the Company entered into an operating lease for 13,232 square feet of office facilities in South San Francisco, California, which expires in July 2025 . The lease agreement contained an option to extend the lease for an additional six-month term. The Company does not have any financing lease agreements as of June 30, 2023. The following table summarizes maturities of operating lease liabilities as of June 30, 2023 (in thousands): 2023 (remaining six months) $ 1,385 2024 2,855 2025 2,662 2026 2,137 Thereafter — Total future undiscounted lease payments 9,039 Less: Imputed interest ( 1,041 ) Total Lease Liabilities $ 7,998 The following table summarizes the balance sheet classification of operating leases at June 30, 2023 (in thousands): Operating leases Operating lease right-of-use assets $ 6,103 Operating lease liabilities, current 2,333 Operating lease liabilities, non-current 5,665 Total operating lease liabilities $ 7,998 For the three and six months ended June 30, 2023 , the Company incurred $ 0.6 million and $ 1.2 million, respectively, of lease expense included in operating expenses in the condensed consolidated statement of operations in relation to the operating leases. Variable lease expense was insignificant for the three and six months ended June 30, 2023 . Rent expense was $ 0.7 million and $ 1.4 million during the three and six months ended June 30, 2023, respectively. Cash paid for amounts included in the measurement of operating lease liabilities for the six months ended June 30, 2023, was $ 1.3 mill ion and was included in net cash used in operating activities in the Company’s condensed consolidated statements of cash flows. As of June 30, 2023 , the weighted-average remaining lease term and discount rate for the Company’s operating leases was 3.2 years and 8.23 %, respectively.

Collaboration Agreements

Collaboration Agreements	6 Months Ended
	Jun. 30, 2023
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 rights. In consideration of such rights, under the Hanmi Agreement, the Company was entitled to $ 10.0 million, which consisted of an upfront payment of $ 4.0 million and a development milestone payment of $ 6.0 million that were received in December 2019 and April 2020, respectively. Additionally, the Company is 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 June 30, 2023 , 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 develop FLX475 in the Hanmi Territory. The Company did no t recognize revenue for the three and six months ended June 30, 2023 , and recognized $ 0.9 million and $ 1.5 million for the three and six months ended June 30, 2022, respectively, as revenue pursuant to the Hanmi Agreement. As of June 30, 2023 , there was no remaining deferred revenue related to the Hanmi Agreement, as the performance obligation of providing Hanmi with the necessary know-how to develop FLX475 in the Hanmi Territory was substantially complete as of the second quarter of 2022.

Common Stock

Common Stock	6 Months Ended
	Jun. 30, 2023
Equity [Abstract]
Common Stock	8. Common Stock As of June 30, 2023, the Company had reserved the following shares of common stock for future issuance: Options issued and outstanding under the 2019 Equity Incentive Plan and 4,079,046 Restricted stock units issued and outstanding under the 2019 Equity 13,500 Shares available for future grants under the 2019 Equity Incentive Plan 3,072,899 Pre-funded warrants issued and outstanding 4,000,000 Shares reserved under the 2019 Employee Stock Purchase Plan 445,780 Total 11,611,225 As of June 30, 2023 , there was up to $ 85.7 million available for future issuance of shares of common stock under the Controlled Equity Offering SM Sales Agreement with Cantor Fitzgerald & Co. and Stifel, Nicolaus & Company, Incorporated (the “ATM Sales Agreement”). No shares were sold under the ATM Sales Agreement during the three and six months ended June 30, 2023 .

Stock-Based Compensation

Stock-Based Compensation	6 Months Ended
	Jun. 30, 2023
Share-Based Payment Arrangement [Abstract]
Stock-based Compensation	9. Stock-Based Compensatio n Stock option activity under the 2019 Equity Incentive Plan (the “2019 Plan”) is set forth below for the six months ended June 30, 2023: Weighted Average Average Remaining Aggregate Number of Exercise Contractual Intrinsic Shares Price Per Term Value Outstanding Share (Years) (in thousands) Balances at December 31, 2022 2,993,280 $ 18.95 7.9 $ 9,425 Stock options granted 1,126,708 26.22 Stock options exercised ( 31,849 ) 9.50 Stock options forfeited ( 9,093 ) 21.78 Balances at June 30, 2023 4,079,046 $ 21.02 8.0 $ 7,956 As of June 30, 2023 , 3,072,899 shares remained available for issuance under the 2019 Plan. Restricted stock unit (“RSU”) activity under the 2019 Plan is set forth below for the six months ended June 30, 2023: Weighted Average Number of Grant Date Shares Fair Value Outstanding Per Share Balances at December 31, 2022 27,000 $ 44.66 RSUs granted — — RSUs vested and settled ( 13,500 ) 44.66 RSUs forfeited — — Balances at June 30, 2023 13,500 $ 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 2019 Employee Stock Purchase Plan (the “2019 ESPP”) was as follows (in thousands): For the Three Months Ended June 30, For the Six Months 2023 2022 2023 2022 Research and development $ 2,015 $ 1,269 $ 3,975 $ 2,448 General and administrative 2,224 1,403 4,358 2,926 Total stock-based compensation expense $ 4,239 $ 2,672 $ 8,333 $ 5,374 As of June 30, 2023 , unrecognized stock-based compensation expense related to outstanding unvested stock options and RSUs that are expected to vest was $ 36.6 million. This unrecognized stock-based compensation expense is expected to be recognized over 2.9 years. The Company recorded stock-based compensation expense related to the 2019 ESPP of $ 0.3 million and $ 0.6 million for the three and six months ended June 30, 2023 , respectively, and $ 0.2 million and $ 0.3 million for the three and six months ended June 30, 2022 , respectively.

Net Loss Per Share

Net Loss Per Share	6 Months Ended
	Jun. 30, 2023
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 and six months ended June 30, 2023 and 2022 (in thousands, except share and per share data): Three Months Ended Six Months Ended 2023 2022 2023 2022 Numerator: Net loss $ ( 25,280 ) $ ( 19,184 ) $ ( 54,551 ) $ ( 39,652 ) Denominator: Weighted-average shares used to compute net loss per share, basic and diluted 38,328,741 31,140,323 38,304,758 30,356,515 Net loss per share, basic and diluted $ ( 0.66 ) $ ( 0.62 ) $ ( 1.42 ) $ ( 1.31 ) For the three and six months ended June 30, 2023 and 2022 , 4,000,000 pre-funded warrants to purchase the Company’s shares of common stock, issued in the May 2022 private placement financing, were included on a weighted average basis in the basic and diluted net loss per share calculation. As of June 30, 2023, all the pre-funded warrants issued in the private placement financing were outstanding. Potential dilutive securities that were not included in the diluted per share calculations because they would be anti-dilutive were as follows: As of June 30, 2023 2022 Stock options issued and outstanding under the 2019 Equity Incentive Plan and 2015 Stock Plan 4,079,046 2,907,596 Estimated shares issuable under the 2019 ESPP 11,801 7,946 RSUs subject to future vesting 13,500 27,000 Total 4,104,347 2,942,542

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2023
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 (“U.S. GAAP”) for interim financial information and pursuant to Article 10 of Regulation S‑X of the Securities Act of 1933, as amended (the “Securities Act”). Accordingly, they do not include all of the information and notes required by U.S. GAAP for complete financial statements. These unaudited condensed consolidated financial statements include only normal and recurring adjustments that the Company believes are necessary to fairly state the Company’s financial position and the results of its operations and cash flows. Interim-period results are not necessarily indicative of results of operations or cash flows for a full year or any subsequent interim period. The condensed consolidated balance sheet at December 31, 2022 has been derived from the audited financial statements at that date but does not include all disclosures required by U.S. GAAP for complete financial statements. Because all of the disclosures required by U.S. GAAP for complete financial statements are not included herein, these unaudited condensed consolidated financial statements and the notes accompanying them should be read in conjunction with the Company’s audited consolidated financial statements included in its Annual Report on Form 10-K for the year ended December 31, 2022 filed on March 14, 2023 with the Securities and Exchange Commission (“SEC”). The accompanying condensed 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., which was established in 2018 and deregistered during the quarter ended June 30, 2023. All intercompany balances and transactions have been eliminated in consolidation.
Revenue	Revenue License and collaborative agreements 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 of cumulative revenue recognized 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 are 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 when (i) the related sales occur or (ii) 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 determines employee, nonemployee and director stock-based compensation expense for all stock-based awards based on their grant date fair value using the Black-Scholes option-pricing model. For stock-based awards with service conditions only, stock-based compensation expense is recognized over the requisite service period using the straight-line method. Forfeitures are recognized as they occur. The fair value of restricted stock awards granted 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.
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 common 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 since the effect of potentially dilutive securities is anti-dilutive.
Marketable Securities	Marketable Securities Marketable securities primarily consist of commercial paper, corporate debt securities and U.S. government agency securities. The Company has classified its marketable securities as available-for-sale and may sell these securities prior to their stated maturities. The Company views these marketable securities as available to support current operations and classifies marketable securities with maturities beyond 12 months as current assets. The Company’s marketable securities are carried at estimated fair value, which is derived from independent pricing sources based on quoted prices in active markets for similar securities. Unrealized gains and losses are reported as a component of accumulated other comprehensive income (loss). The amortized cost of marketable securities is adjusted for amortization of premiums and accretion of discounts to maturity, which is included in other income, net on the condensed consolidated statements of operations. All of the Company's available-for-sale investments are subject to a periodic impairment review. For each available-for-sale investment whose fair value is below its amortized cost, the Company determines if the impairment is a result of a credit-related loss or other factors using both quantitative and qualitative 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. If the impairment is a result of a credit-related loss, the Company recognizes an allowance for credit losses. If the impairment is not a result of a credit loss, the Company recognizes the loss in other comprehensive loss.
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 .
Accounting Pronouncements Recently Adopted	Accounting Pronouncements Recently Adopted 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. 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 . ASU 2016-13 amended the guidance on reporting credit losses for assets held at amortized cost basis and available-for-sale debt securities. For available-for-sale debt securities, credit losses will be presented as an allowance rather than as a write-down. In November 2019, the FASB issued ASU No. 2019-10, Financial Instruments—Credit Losses (Topic 326), Derivatives and Hedging (Topic 815), and Leases (Topic 842): Effective Dates and ASU No. 2019-11, Codification Improvements to Topic 326, Financial Instruments—Credit Losses , which defers the effective date of ASU 2016-13 for smaller report companies. ASU 2016-13 is effective for the Company’s fiscal year beginning January 1, 2023 . The adoption of ASU 2016-13 did not have a material impact on the Company's condensed consolidated financial statements and related disclosures.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2023
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 June 30, 2023 Fair Value Amortized Unrealized Unrealized Fair Financial assets: Money market funds Level 1 $ 50,106 $ — $ — $ 50,106 Corporate debt Level 2 32,299 — ( 89 ) 32,210 Commercial paper Level 2 47,834 — — 47,834 U.S. government agency securities Level 2 74,881 3 ( 94 ) 74,790 Subtotal 205,120 3 ( 183 ) 204,940 Less: Cash equivalents ( 50,106 ) — — ( 50,106 ) Marketable securities $ 155,014 $ 3 $ ( 183 ) $ 154,834 As of December 31, 2022 Fair Value Amortized Unrealized Unrealized Fair Financial assets: Money market funds Level 1 $ 38,658 $ — $ — $ 38,658 Corporate debt Level 2 71,149 30 ( 284 ) 70,895 Asset-backed securities Level 2 105 — ( 1 ) 104 Commercial paper Level 2 71,328 — — 71,328 U.S. government agency securities Level 2 68,221 15 ( 441 ) 67,795 Subtotal 249,461 45 ( 726 ) 248,780 Less: Cash equivalents ( 38,658 ) — — ( 38,658 ) Marketable securities $ 210,803 $ 45 $ ( 726 ) $ 210,122
Schedule of Remaining Contractual Maturities of Marketable Securities	The following table presents the remaining contractual maturities of the Company’s marketable securities as of June 30, 2023 (in thousands): June 30, 2023 Maturing in one year or less $ 151,859 Maturing after one year through five years 2,975 Total $ 154,834

Property and Equipment (Tables)

Property and Equipment (Tables)	6 Months Ended
	Jun. 30, 2023
Property, Plant and Equipment [Abstract]
Schedule of Property and Equipment	Property and equipment consisted of the following (in thousands): June 30, December 31, 2023 2022 Laboratory equipment $ 7,398 $ 6,558 Leasehold improvements 3,295 3,295 Computer equipment 617 578 Furniture and fixtures 394 357 Total property and equipment 11,704 10,788 Less accumulated depreciation and amortization ( 8,741 ) ( 8,249 ) Property and equipment, net $ 2,963 $ 2,539

Accrued Expenses (Tables)

Accrued Expenses (Tables)	6 Months Ended
	Jun. 30, 2023
Payables and Accruals [Abstract]
Schedule of Accrued Expenses	Accrued expenses consisted of the following (in thousands): June 30, December 31, 2023 2022 Accrued research and development expenses $ 5,659 $ 3,473 Accrued compensation 3,971 4,618 Accrued professional and consulting services 480 327 Other 185 238 Total accrued expenses $ 10,295 $ 8,656

Leases (Tables)

Leases (Tables)	6 Months Ended
	Jun. 30, 2023
Leases [Abstract]
Summary of Maturities of Lease Liabilities	The following table summarizes maturities of operating lease liabilities as of June 30, 2023 (in thousands): 2023 (remaining six months) $ 1,385 2024 2,855 2025 2,662 2026 2,137 Thereafter — Total future undiscounted lease payments 9,039 Less: Imputed interest ( 1,041 ) Total Lease Liabilities $ 7,998
Summary of Balance Sheet Classification of Leases	The following table summarizes the balance sheet classification of operating leases at June 30, 2023 (in thousands): Operating leases Operating lease right-of-use assets $ 6,103 Operating lease liabilities, current 2,333 Operating lease liabilities, non-current 5,665 Total operating lease liabilities $ 7,998

Common Stock (Tables)

Common Stock (Tables)	6 Months Ended
	Jun. 30, 2023
Equity [Abstract]
Summary of Reserved Shares of Common Stock for Future Issuance	As of June 30, 2023, the Company had reserved the following shares of common stock for future issuance: Options issued and outstanding under the 2019 Equity Incentive Plan and 4,079,046 Restricted stock units issued and outstanding under the 2019 Equity 13,500 Shares available for future grants under the 2019 Equity Incentive Plan 3,072,899 Pre-funded warrants issued and outstanding 4,000,000 Shares reserved under the 2019 Employee Stock Purchase Plan 445,780 Total 11,611,225

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	6 Months Ended
	Jun. 30, 2023
Share-Based Payment Arrangement [Abstract]
Summary of Stock Option Activity	Stock option activity under the 2019 Equity Incentive Plan (the “2019 Plan”) is set forth below for the six months ended June 30, 2023: Weighted Average Average Remaining Aggregate Number of Exercise Contractual Intrinsic Shares Price Per Term Value Outstanding Share (Years) (in thousands) Balances at December 31, 2022 2,993,280 $ 18.95 7.9 $ 9,425 Stock options granted 1,126,708 26.22 Stock options exercised ( 31,849 ) 9.50 Stock options forfeited ( 9,093 ) 21.78 Balances at June 30, 2023 4,079,046 $ 21.02 8.0 $ 7,956
Summary of RSU Activity	Restricted stock unit (“RSU”) activity under the 2019 Plan is set forth below for the six months ended June 30, 2023: Weighted Average Number of Grant Date Shares Fair Value Outstanding Per Share Balances at December 31, 2022 27,000 $ 44.66 RSUs granted — — RSUs vested and settled ( 13,500 ) 44.66 RSUs forfeited — — Balances at June 30, 2023 13,500 $ 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 2019 Employee Stock Purchase Plan (the “2019 ESPP”) was as follows (in thousands): For the Three Months Ended June 30, For the Six Months 2023 2022 2023 2022 Research and development $ 2,015 $ 1,269 $ 3,975 $ 2,448 General and administrative 2,224 1,403 4,358 2,926 Total stock-based compensation expense $ 4,239 $ 2,672 $ 8,333 $ 5,374

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	6 Months Ended
	Jun. 30, 2023
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 and six months ended June 30, 2023 and 2022 (in thousands, except share and per share data): Three Months Ended Six Months Ended 2023 2022 2023 2022 Numerator: Net loss $ ( 25,280 ) $ ( 19,184 ) $ ( 54,551 ) $ ( 39,652 ) Denominator: Weighted-average shares used to compute net loss per share, basic and diluted 38,328,741 31,140,323 38,304,758 30,356,515 Net loss per share, basic and diluted $ ( 0.66 ) $ ( 0.62 ) $ ( 1.42 ) $ ( 1.31 )
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 June 30, 2023 2022 Stock options issued and outstanding under the 2019 Equity Incentive Plan and 2015 Stock Plan 4,079,046 2,907,596 Estimated shares issuable under the 2019 ESPP 11,801 7,946 RSUs subject to future vesting 13,500 27,000 Total 4,104,347 2,942,542

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Additional Information (Details)	6 Months Ended
	Jun. 30, 2023
Accounting Policies [Abstract]
Change in accounting principle, accounting standards update, adopted	true
Change in accounting principle, accounting standards update, adoption date	Jan. 01, 2023
Change in accounting principle, accounting standards update, immaterial effect	true
Accounting Standards Update [Extensible Enumeration]	us-gaap:AccountingStandardsUpdate201613Member

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	Jun. 30, 2023	Dec. 31, 2022
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 205,120	$ 249,461
Unrealized Gains	3	45
Unrealized Losses	(183)	(726)
Fair Value	204,940	248,780
Less: Cash equivalents	(50,106)	(38,658)
Marketable securities, Amortized Cost	155,014	210,803
Marketable securities, Unrealized Gains	3	45
Marketable securities, Unrealized Losses	(183)	(726)
Marketable securities, Fair Value	154,834	210,122
Level 1 | Money Market Funds
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	50,106	38,658
Fair Value	50,106	38,658
Level 2 | Corporate Debt
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	32,299	71,149
Unrealized Gains		30
Unrealized Losses	(89)	(284)
Fair Value	32,210	70,895
Level 2 | Asset-backed Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost		105
Unrealized Losses		(1)
Fair Value		104
Level 2 | Commercial Paper
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	47,834	71,328
Fair Value	47,834	71,328
Level 2 | U.S. Government Agency Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	74,881	68,221
Unrealized Gains	3	15
Unrealized Losses	(94)	(441)
Fair Value	$ 74,790	$ 67,795

Fair Value Measurements - Sch_2

Fair Value Measurements - Schedule of Remaining Contractual Maturities of Marketable Securities (Details) $ in Thousands	Jun. 30, 2023 USD ($)
Investments, Debt and Equity Securities [Abstract]
Maturing in one year or less	$ 151,859
Maturing after one year through five years	2,975
Total	$ 154,834

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Details)	6 Months Ended
	Jun. 30, 2023 USD ($)
Fair Value Disclosures [Abstract]
Marketable securities impairment loss	$ 0

Property and Equipment - Schedu

Property and Equipment - Schedule of Property and Equipment (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Property Plant And Equipment [Line Items]
Total property and equipment	$ 11,704	$ 10,788
Less accumulated depreciation and amortization	(8,741)	(8,249)
Property and equipment, net	2,963	2,539
Laboratory Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	7,398	6,558
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	617	578
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		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Property, Plant and Equipment [Abstract]
Depreciation and amortization expense	$ 300	$ 200	$ 568	$ 535

Accrued Expenses - Schedule of

Accrued Expenses - Schedule of Accrued Expenses (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Payables and Accruals [Abstract]
Accrued research and development expenses	$ 5,659	$ 3,473
Accrued compensation	3,971	4,618
Accrued professional and consulting services	480	327
Other	185	238
Total accrued expenses	$ 10,295	$ 8,656

Leases - Summary of Balance She

Leases - Summary of Balance Sheets Adjustments Related to Lease Accounting Standard Update (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Lessee Lease Description [Line Items]
Operating lease right-of-use assets	$ 6,103	$ 6,940
Total assets	220,756	266,209
Operating lease liabilities, current	2,333	2,171
Operating lease liabilities, non-current	5,665	6,819
Total liabilities	$ 21,079	$ 21,043

Leases - Additional Information

Leases - Additional Information (Details) $ in Millions		1 Months Ended		3 Months Ended	6 Months Ended
	Nov. 30, 2022 ft²	Apr. 30, 2018 ft²	May 31, 2015 ft²	Jun. 30, 2023 USD ($)	Jun. 30, 2023 USD ($)
Lessee Lease Description [Line Items]
Lease expiration period	2025-07
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	6 months		5 years
Lease expense | $				$ 0.6	$ 1.2
Rent expense | $				$ 0.7	1.4
Cash paid for operating lease liabilities | $					$ 1.3
Operating lease, weighted average remaining lease term				3 years 2 months 12 days	3 years 2 months 12 days
Operating lease, weighted average discount rate, percent				8.23%	8.23%
South San Francisco and California
Lessee Lease Description [Line Items]
Laboratory and office facilities under lease | ft²	13,232		30,376

Leases - Summary of Maturities

Leases - Summary of Maturities of Lease Liabilities (Details) $ in Thousands	Jun. 30, 2023 USD ($)
Leases [Abstract]
2023 (remaining six months)	$ 1,385
2024	2,855
2025	2,662
2026	2,137
Total future undiscounted lease payments	9,039
Less: Imputed interest	(1,041)
Total Lease Liabilities	$ 7,998

Leases - Summary of Balance S_2

Leases - Summary of Balance Sheet Classification of Leases (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Leases [Abstract]
Operating lease right-of-use assets	$ 6,103	$ 6,940
Operating lease liabilities, current	2,333	2,171
Operating lease liabilities, non-current	5,665	$ 6,819
Total operating lease liabilities	$ 7,998

Collaboration Agreements - Addi

Collaboration Agreements - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Apr. 30, 2020	Dec. 31, 2019
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue recognized	$ 0	$ 886,000	$ 0	$ 1,527,000
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		10,400,000			$ 10,000,000
Upfront fee	4,000,000		4,000,000			4,000,000
Development milestone payment					$ 6,000,000
Milestone payment	6,000,000		6,000,000
Milestone payment related to supply	400,000		400,000
Revenue recognized	0	$ 900,000	0	$ 1,500,000
Deferred revenue	$ 0		$ 0
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)	Jun. 30, 2023 shares
Class Of Stock [Line Items]
Total shares reserved	11,611,225
Pre-funded warrants issued and outstanding
Class Of Stock [Line Items]
Total shares reserved	4,000,000
2019 Equity Incentive Plan and 2015 Stock Plan | Options Issued and Outstanding
Class Of Stock [Line Items]
Total shares reserved	4,079,046
2019 Equity Incentive Plan | Restricted Stock Units Issued and Outstanding
Class Of Stock [Line Items]
Total shares reserved	13,500
2019 Equity Incentive Plan | Shares Available for Future Grants
Class Of Stock [Line Items]
Total shares reserved	3,072,899
2019 Employee Stock Purchase Plan
Class Of Stock [Line Items]
Total shares reserved	445,780

Common Stock - Additional Infor

Common Stock - Additional Information (Details)	3 Months Ended	6 Months Ended
	Jun. 30, 2023 shares	Jun. 30, 2023 shares
Class Of Stock [Line Items]
Total shares reserved	11,611,225	11,611,225
Sales Agreement | ATM Sales Agreement
Class Of Stock [Line Items]
Shares issued during period	0	0
Maximum | Sales Agreement | ATM Sales Agreement
Class Of Stock [Line Items]
Total shares reserved	85,700,000	85,700,000

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	6 Months Ended	12 Months Ended
	Jun. 30, 2023	Dec. 31, 2022
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Shares Outstanding, Beginning Balance	2,993,280
Number of Shares Outstanding, Stock options granted	1,126,708
Number of Shares Outstanding, Stock options exercised	(31,849)
Number of Shares Outstanding, Stock options forfeited	(9,093)
Number of Shares Outstanding, Ending Balance	4,079,046	2,993,280
Weighted Average Exercise Price Per Share, Beginning Balance	$ 18.95
Weighted Average Exercise Price Per Share, Stock options granted	26.22
Weighted Average Exercise Price Per Share, Stock options exercised	9.50
Weighted Average Exercise Price Per Share, Stock options forfeited	21.78
Weighted Average Exercise Price Per Share, Ending Balance	$ 21.02	$ 18.95
Average Remaining Contractual Term (Years), Balance	8 years	7 years 10 months 24 days
Aggregate Intrinsic Value	$ 7,956	$ 9,425

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
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	$ 36,600		$ 36,600
Unrecognized stock-based compensation cost, expected period to be recognized			2 years 10 months 24 days
Stock-based compensation expense	4,239	$ 2,672	$ 8,333	$ 5,374
2019 ESPP
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 300	$ 200	$ 600	$ 300
2019 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares remained available for issuance	3,072,899		3,072,899

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summary of RSU Activity (Details) - 2019 Plan - Restricted Stock Unit ("RSU")	6 Months Ended
	Jun. 30, 2023 $ / shares shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Shares Outstanding, Beginning Balance | shares	27,000
Number of Shares Outstanding, RSUs vested and settled | shares	(13,500)
Number of Shares Outstanding, Ending Balance | shares	13,500
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		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 4,239	$ 2,672	$ 8,333	$ 5,374
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	2,015	1,269	3,975	2,448
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 2,224	$ 1,403	$ 4,358	$ 2,926

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				6 Months Ended
	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2022	Mar. 31, 2022	Jun. 30, 2023	Jun. 30, 2022
Numerator:
Net loss	$ (25,280)	$ (29,271)	$ (19,184)	$ (20,468)	$ (54,551)	$ (39,652)
Denominator:
Weighted-average shares used to compute net loss per share, basic	38,328,741		31,140,323		38,304,758	30,356,515
Weighted-average shares used to compute net loss per share, diluted	38,328,741		31,140,323		38,304,758	30,356,515
Net loss per share, basic	$ (0.66)		$ (0.62)		$ (1.42)	$ (1.31)
Net loss per share, diluted	$ (0.66)		$ (0.62)		$ (1.42)	$ (1.31)

Net Loss Per Share - Additional

Net Loss Per Share - Additional Information (Details) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Earnings Per Share [Abstract]
Pre-funded warrants to purchase common stock	4,000,000	4,000,000	4,000,000	4,000,000

Net Loss Per Share - Potential

Net Loss Per Share - Potential Dilutive Securities not Included in Diluted per Share Calculations (Details) - shares	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potential dilutive securities	4,104,347	2,942,542
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	4,079,046	2,907,596
Estimated Shares Issuable Under Employee Stock Purchase Plan
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potential dilutive securities	11,801	7,946
RSUs Subject to Future Vesting
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potential dilutive securities	13,500	27,000