CytomX Therapeutics (CTMX) 10-Q8 May 242024 Q1 Quarterly reportFinancial data

Company Profile

Document and Entity Information

Document and Entity Information	3 Months Ended
Document and Entity Information	Mar. 31, 2024
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2024
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q1
Trading Symbol	CTMX
Entity Registrant Name	CytomX Therapeutics, Inc.
Entity Central Index Key	0001501989
Current Fiscal Year End Date	--03-31
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity File Number	001-37587
Entity Tax Identification Number	27-3521219
Entity Address, Address Line One	151 Oyster Point Blvd.
Entity Address, Address Line Two	Suite 400
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	515-3185
Entity Interactive Data Current	Yes
Title of 12(b) Security	Common Stock, $0.00001 par value per share
Security Exchange Name	NASDAQ
Entity Incorporation, State or Country Code	DE
Document Quarterly Report	true
Document Transition Report	false

CONDENSED BALANCE SHEETS

CONDENSED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023	[1]	Mar. 31, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 36,185	$ 17,171
Short-term investments	114,099	157,338
Accounts receivable	13,177	3,432
Prepaid expenses and other current assets	3,786	4,995
Total current assets	167,247	182,936
Property and equipment, net	3,567	3,958
Intangible assets, net	693	729
Goodwill	949	949
Restricted cash	917	917
Operating lease right-of-use asset	11,234	12,220
Other assets	80	83
Total assets	184,687	201,792
Current liabilities:
Accounts payable	1,964	1,458
Accrued liabilities	14,220	17,599
Operating lease liabilities - short term	4,724	4,589
Deferred revenue, current portion	123,628	132,267
Total current liabilities	144,536	155,913
Deferred revenue, net of current portion	59,743	80,048
Operating lease liabilities - long term	8,148	9,385
Other long-term liabilities	3,940	3,893
Total liabilities	216,367	249,239
Commitments and contingencies (Note 9)
Stockholders' deficit:
Convertible preferred stock	0	0
Common stock	1	1
Additional paid-in capital	677,986	675,905
Accumulated other comprehensive (loss) income	(10)	95
Accumulated deficit	(709,657)	(723,448)
Total stockholders' deficit	(31,680)	(47,447)		$ (86,637)	$ (85,751)
Total liabilities and stockholders' deficit	$ 184,687	$ 201,792

[1] The condensed balance sheet as of December 31, 2023 was derived from the audited financial statements included in the Company's Annual Report on Form 10-K for the year ended December 31, 2023.

CONDENSED STATEMENTS OF OPERATI

CONDENSED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Statement of Comprehensive Income [Abstract]
Revenues	$ 41,463	$ 23,499
Type of Revenue [Extensible List]	us-gaap:LicenseAndServiceMember	us-gaap:LicenseAndServiceMember
Operating expenses:
Research and development	$ 22,052	$ 21,175
General and administrative	7,754	7,977
Total operating expenses	29,806	29,152
Income (Loss) from operations	11,657	(5,653)
Interest income	2,194	2,327
Other (expense) income, net	(11)	15
Income (Loss) before income taxes	13,840	(3,311)
Provision for income taxes	49	0
Net Income (loss)	13,791	(3,311)
Other comprehensive income (loss):
Unrealized (loss) gain on investments, net of tax	(105)	16
Total comprehensive income (loss)	$ 13,686	$ (3,295)
Net income (loss) per share, Basic	$ 0.17	$ (0.05)
Net income (loss) per share, Diluted	$ 0.17	$ (0.05)
Shares used to compute net income (loss) per share, Basic	82,029,466	66,248,992
Shares used to compute net income (loss) per share, Diluted	82,630,020	66,248,992

CONDENSED STATEMENTS OF STOCKHO

CONDENSED STATEMENTS OF STOCKHOLDERS' DEFICIT - USD ($) $ in Thousands	Total		Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning balance at Dec. 31, 2022	$ (85,751)		$ 1	$ 637,117	$ 10	$ (722,879)
Beginning balance, shares at Dec. 31, 2022			66,228,046
Release of RSUs, shares			110,892
Stock-based compensation	2,409			2,409
Other comprehensive income (loss)	16				16
Net Income (Loss)	(3,311)					(3,311)
Ending balance at Mar. 31, 2023	(86,637)		$ 1	639,526	26	(726,190)
Ending balance, shares at Mar. 31, 2023			66,338,938
Beginning balance at Dec. 31, 2023	(47,447)	[1]	$ 1	675,905	95	(723,448)
Beginning balance, shares at Dec. 31, 2023			67,310,838
Exercise of stock options and release of RSUs	174			174
Exercise of stock options and release of RSUs, shares			826,797
Stock-based compensation	1,907			1,907
Other comprehensive income (loss)	(105)				(105)
Net Income (Loss)	13,791					13,791
Ending balance at Mar. 31, 2024	$ (31,680)		$ 1	$ 677,986	$ (10)	$ (709,657)
Ending balance, shares at Mar. 31, 2024			68,137,635

[1] The condensed balance sheet as of December 31, 2023 was derived from the audited financial statements included in the Company's Annual Report on Form 10-K for the year ended December 31, 2023.

CONDENSED STATEMENTS OF CASH FL

CONDENSED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
CONDENSED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	Mar. 31, 2024	Mar. 31, 2023
Cash flows from operating activities:
Net income (loss)	$ 13,791	$ (3,311)
Adjustments to reconcile net income (loss) to net cash (used in) provided by operating activities:
Amortization of intangible assets	36	36
Depreciation and amortization	431	559
Accretion of discounts on short-term investments	(1,866)	(1,535)
Stock-based compensation expense	1,907	2,409
Non-cash lease expense	986	901
Changes in operating assets and liabilities
Accounts receivable	(9,745)	34,896
Prepaid expenses and other assets	1,212	781
Accounts payable	581	(618)
Accrued liabilities and other long-term liabilities	(4,434)	(7,360)
Deferred revenue	(28,944)	(17,409)
Net cash (used in) provided by operating activities	(26,045)	9,349
Cash flows from investing activities:
Purchases of property and equipment	(115)	(48)
Purchases of short term investments	0	(146,594)
Maturities of short-term investments	45,000	0
Net cash provided by (used in) investing activities	44,885	(146,642)
Cash flows from financing activities:
Proceeds from exercise of stock options	174	0
Net cash provided by financing activities	174	0
Net increase (decrease) in cash, cash equivalents and restricted cash	19,014	(137,293)
Cash, cash equivalents and restricted cash, beginning of year	18,088	194,567
Cash, cash equivalents and restricted cash, end of year	$ 37,102	$ 57,274

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Thousands	3 Months Ended
Pay vs Performance Disclosure - USD ($) $ in Thousands	Mar. 31, 2024	Mar. 31, 2023
Pay vs Performance Disclosure
Net Income (Loss)	$ 13,791	$ (3,311)

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended
Insider Trading Arrangements	Mar. 31, 2024 shares
Trading Arrangements, by Individual
Material Terms of Trading Arrangement	On March 26, 2024 , Sean A. McCarthy , our Chief Executive Officer , terminated a Rule 10b5-1 trading arrangement intended to satisfy the affirmative defense of Rule 10b5-1(c) and originally adopted on June 01, 2023 , for the sale of up to 109,768 shares of the Company’s common stock until February 07, 2025 .
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false
Rule 10b51 Arrangement Modified Flag	false
Non-Rule 10b51 Arrangement Modified Flag	false
Sean A. McCarthy [Member]
Trading Arrangements, by Individual
Name	Sean A. McCarthy
Title	Chief Executive Officer
Adoption Date	June 01, 2023
Termination Date	March 26, 2024
Arrangement Duration	617 days
Aggregate Available	109,768
Trading Arrangemnt Expiration Date	February 07, 2025

Description of the Business

Description of the Business	3 Months Ended
Description of the Business	Mar. 31, 2024
Disclosure Text Block [Abstract]
Description of the Business	1. Descriptio n of the Business CytomX Therapeutics, Inc. (the “Company”) is a clinical-stage, oncology-focused biopharmaceutical company developing potent biologics designed to remain masked and inactive in healthy tissue and to be unmasked and preferentially activated in the tumor microenvironment. The Company aims to build a commercial enterprise to maximize its impact on the treatment of cancer. The Company is advancing potential first-in-class and best-in-class therapeutics created using its PROBODY® therapeutic technology platform that could meaningfully improve outcomes for cancer patients. Its proprietary and unique PROBODY technology platform is designed to enable “conditional activation” of antibody-based drugs in the tumor microenvironment across multiple therapeutic modalities. The Company is located in South San Francisco, California and was incorporated in the state of Delaware in September 2010.

Basis of Presentation and Summa

Basis of Presentation and Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2024
Accounting Policies [Abstract]
Basis of Presentation and Summary of Significant Accounting Policies	2. Basis of Presentation and Summary of Significant Accounting Policies Basis of Presentation The accompanying interim condensed financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and applicable rules and regulations of the U.S. Securities and Exchange Commission (“SEC”) regarding interim financial reporting. Unaudited Interim Financial Information The accompanying interim condensed financial statements and related disclosures are unaudited, have been prepared on the same basis as the annual financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary for a fair statement of the results of operations for the periods presented. The condensed results of operations for the three months ended March 31, 2024 are not necessarily indicative of the results to be expected for the full year or for any other future year or interim period. The accompanying condensed financial statements should be read in conjunction with the audited financial statements and the related notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2023 filed with the SEC. Use of Estimates The preparation of the financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent liabilities at the date of the financial statements and reported amounts of revenues and expenses during the reporting periods. Actual results could differ from those estimates. Cash, Cash Equivalents and Restricted Cash The Company considers all highly liquid investments purchased with original maturities of three months or less at the date of purchase to be cash equivalents. Restricted cash represents a standby letter of credit issued pursuant to an office lease. Revenue Recognition The Company’s revenues are primarily derived through its license, research, development and commercialization agreements. The terms of these types of agreements may include (i) licenses for the Company’s technology or programs, (ii) research and development services, and (iii) services or obligations in connection with participation in research or steering committees. Payments to the Company under these arrangements typically include one or more of the following: nonrefundable upfront and license fees, research funding, milestone and other contingent payments to the Company for the achievement of defined collaboration objectives and certain preclinical, clinical, regulatory and sales-based events, as well as royalties on sales of any commercialized products. The Company assesses whether the promises in its arrangements with customers are distinct performance obligations that should be accounted for separately. Judgment is required to determine whether the license to the Company’s intellectual property is distinct from the research and development services or participation on steering committees. The Company’s collaboration and license agreements may include contingent payments related to specified research, development and regulatory milestones. Such milestone payments are typically payable under the collaborations when the collaboration partner claims or selects a target, or initiates or advances a covered product candidate in preclinical or clinical development, upon submission for marketing approval of a covered product with regulatory authorities, or upon receipt of actual marketing approvals of a covered product or for additional indications. Milestone payments that are not within the control of the Company or the licensee, such as regulatory approvals, are not considered probable of being achieved until those approvals are received. At each reporting date, the Company re-evaluates whether the milestones are considered probable of being achieved and estimates the amount to be included in the transaction price by using the most likely amount method. If it is probable that a significant revenue reversal would not occur, the associated milestone value is included in the transaction price in such period of determination. The Company’s collaboration and license agreements may also include contingent payments related to sales-based milestones. Sales-based milestones are typically payable when annual sales of a covered product reach specified levels. Sales-based milestones are recognized at the later of when the associated performance obligation has been satisfied or when the sales occur. Unlike other contingency payments, such as regulatory milestones, sales-based milestones are not included in the transaction price based on estimates at the inception of the contract; instead, they are included when the sales or usage occur. Due to the early stage of the Company’s licensed technology, the license of such technology is typically combined with research and development services and steering committee participation as one performance obligation. Under the collaboration and license agreements, each collaboration target or program is generally considered to be a separate combined performance obligation. The transaction price in each arrangement is allocated to the identified performance obligations based on the relative standalone selling price (“SSP”) of each distinct performance obligation, which requires judgment. In instances where SSP is not directly observable, such as when a license or service is not sold separately, SSP is determined using information that may include market conditions and other observable inputs. Variable consideration is allocated to certain performance obligations if it is triggered by the Company’s efforts to satisfy or a specific outcome from satisfying these performance obligations. In the event that the Company receives non-cash consideration such as consideration in the form of a research license and research support services from the counterparty, the transaction price of a non-monetary exchange that has commercial substance is estimated based on the fair value of the non-cash consideration received, which may be determined through a valuation analysis. The Company recognizes revenue from upfront payments over the estimated period of performance under the agreement using an input method for the performance obligation. In applying the input method of revenue recognition, the Company uses actual full-time equivalent (FTE) hours incurred relative to estimated total FTE hours expected to be incurred for each combined performance obligation over the estimated research service period of each collaboration target. In certain cases, the Company’s performance creates an asset that does not have an alternative use to the customer and the Company has an enforceable right to payment at all times for performance completed to date. In these cases, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. Any consideration payable to the Company’s customers is treated as a reduction to the transaction price and revenue, unless the payment to the customer is in exchange for distinct good and services. Contract Balances Customer payments are recorded as deferred revenue upon receipt or when due and may require deferral of revenue recognition to a future period until the Company satisfies its performance obligations under these arrangements. Amounts payable to the Company are recorded as accounts receivable when the Company’s right to consideration is unconditional. Recently Issued Accounting Standards Not Yet Adopted In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures ("ASU 2023-09"), which enhances transparency in income tax disclosures. ASU 2023-09 require entities to disclose (1) specific categories in the rate reconciliation, (2) the income or loss from continuing operations before income tax expense or benefit (separated between domestic and foreign) and (3) income tax expense or benefit from continuing operations (separated by federal, state and foreign). ASU 2023-09 also requires entities to disclose their income tax payments to international, federal, state and local jurisdictions, among other changes. The amendments are set to be effective for fiscal years beginning after December 15, 2024, and are required to be applied on a prospective basis. The Company is evaluating the impact on our financial statements. Other accounting standards that have been issued or proposed by the FASB or other standards-setting bodies that do not require adoption until a future date are not expected to have a material impact on the Company’s consolidated financial statements upon adoption.

Net Income (Loss) Per Share

Net Income (Loss) Per Share	3 Months Ended
Net Income (Loss) Per Share	Mar. 31, 2024
Earnings Per Share [Abstract]
Net Income (Loss) Per Share	3. Net Income (Loss) Per Share Basic net income (loss) per share is calculated by dividing the net income (loss) by the weighted-average number of shares of common stock outstanding for the period. Diluted net income (loss) per share is calculated using the weighted-average number of common shares outstanding, plus potential dilutive common stock during the period. Diluted net loss per share is the same as basic net loss per share since the effect of the potentially dilutive securities is anti-dilutive. The pre-funded warrants are included in both the basic and diluted EPS calculation. The following table presents the calculation of basic and diluted net income (loss) per share: Three Months Ended March 31, 2024 2023 (in thousands, except share and per share data) Numerator: Net income (loss) $ 13,791 $ ( 3,311 ) Denominator: Basic Weighted-average common shares outstanding 67,606,389 66,248,992 Weighted-average pre-funded warrants 14,423,077 — Weighted-average common shares outstanding used to calculate basic net income (loss) per share 82,029,466 66,248,992 Diluted Weighted-average common shares outstanding used to calculate basic net income (loss) per share 82,029,466 66,248,992 Effect of potentially dilutive securities: Stock options, ESPP & RSUs 600,554 — Weighted-average common shares outstanding used to calculate diluted net income (loss) per share 82,630,020 66,248,992 Net income (loss) per share Basic $ 0.17 $ ( 0.05 ) Diluted $ 0.17 $ ( 0.05 ) The following weighted-average outstanding shares of potentially dilutive securities are excluded from the computation of diluted net income (loss) per share for the periods presented, because including them would have been anti-dilutive: Three Months Ended March 31, 2024 2023 Options and ESPP to purchase common stock 13,710,289 13,986,524 Common stock warrants 11,538,462 — RSUs 227,525 1,539,053 Total 25,476,276 15,525,577

Fair Value Measurements and Inv

Fair Value Measurements and Investments	3 Months Ended
Fair Value Measurements and Investments	Mar. 31, 2024
Fair Value Disclosures [Abstract]
Fair Value Measurements and Investments	4. Fair Value Measurements and Investments In accordance with Accounting Standards Codification (“ASC”) 820-10, Fair Value Measurements and Disclosures, the Company determines the fair value of financial and non-financial assets and liabilities using the fair value hierarchy, which establishes three levels of inputs that may be used to measure fair value, as follows: • Level I: Inputs which include quoted prices in active markets for identical assets and liabilities. • Level II: Inputs other than Level I that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; quoted prices 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 assets or liabilities. • Level III: Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. The carrying amounts of the Company’s financial instruments, including restricted cash, accounts receivable, accounts payable and accrued liabilities approximate fair value due to their relatively short maturities. The Company’s financial instruments consist of Level I assets which consist primarily of highly liquid money market funds, some of which are included in restricted cash and U.S. Treasury securities that are included in cash equivalents or short-term investments. The following tables set forth the fair value of the Company’s investments subject to fair value measurements on a recurring basis and the level of inputs used in such measurements: March 31, 2024 Valuation Amortized Gross Aggregate (in thousands) Assets Money market funds Level I $ 39,069 $ — $ 39,069 Restricted cash (money market funds) Level I 917 — 917 U.S. Treasury Securities Level II 114,109 ( 10 ) 114,099 Total $ 154,095 $ ( 10 ) $ 154,085 December 31, 2023 Valuation Amortized Gross Aggregate (in thousands) Assets Money market funds Level I $ 17,109 $ — $ 17,109 Restricted cash (money market funds) Level I 917 — $ 917 U.S. Treasury Securities Level II 157,243 95 $ 157,338 Total $ 175,269 $ 95 $ 175,364 As of March 31, 2024, the remaining contractual terms of those investments are less than a year.

Accrued Liabilities

Accrued Liabilities	3 Months Ended
Accrued Liabilities	Mar. 31, 2024
Accrued Liabilities, Current [Abstract]
Accrued Liabilities	5. Accrued Liabilities Accrued liabilities consisted of the following: March 31, December 31, 2024 2023 (in thousands) Research and clinical expenses $ 7,701 $ 8,435 Payroll and related expenses 4,855 8,160 Legal and professional expenses 1,209 690 Other accrued expenses 455 314 Total $ 14,220 $ 17,599

Collaboration and License Agree

Collaboration and License Agreements	3 Months Ended
Collaboration and License Agreements	Mar. 31, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Collaboration and License Agreements	6. Collaboration and License Agreements The following table summarizes the revenue by collaboration partner: Three Months Ended 2024 2023 (in thousands) AbbVie $ — $ 3,988 Amgen 1,279 1,776 Astellas 15,452 8,705 Bristol Myers Squibb 19,634 7,725 Regeneron 2,393 581 Moderna 2,705 724 Total revenue $ 41,463 $ 23,499 AbbVie Ireland Unlimited Company In April 2016, the Company and AbbVie entered into two agreements, a CD71 Co-Development and Licensing Agreement (the “CD71 Agreement”) and a Discovery Collaboration and Licensing Agreement (as amended and restated in June 2019, the “Discovery Agreement” and together with the CD71 Agreement the “AbbVie Agreements”). Under the terms of the CD71 Agreement, the Company and AbbVie were co-developing a conditionally activated antibody-drug conjugate (“ADC”), CX-2029, against CD71, with the Company being responsible for preclinical and early clinical development. AbbVie was to be responsible for later development and commercialization, with global late-stage development costs shared between the two companies. Under the CD71 Agreement, t he Company has received in aggregate $ 100.0 million in upfront and milestone payments. AbbVie had entered into a license agreement with Seattle Genetics, Inc. (“SGEN”) to license certain intellectual property rights pursuant to which the Company was required to pay SGEN sublicense fees for certain milestone achievements and an annual maintenance fee. These sublicense fees were treated as reductions to the transaction price and combined with the performance obligation to which they relate. In March 2023, the Company announced that it would evaluate the potential next steps for CX-2029 following the decision from AbbVie, to not advance CX-2029 into additional clinical studies. As a result of AbbVie’s decision, the 2016 CD71 License and Collaboration Agreement was terminated in May 2023 and the Company re-acquired full rights to CX-2029. The Company has completed the performance obligation under the CD71 Agreement as of March 31, 2023, and recognized the related remaining deferred revenue of $ 4.0 million in the first quarter of 2023. In December 2022, the research on the two discovery targets under the Discovery Agreement concluded with no plans to advance the discovery targets into clinical studies or to pursue new programs. The Discovery Agreement was also terminated and all target rights have reverted back to CytomX. In August 2023, the Company entered into a Transition Agreement (the “Transition Agreement”) with AbbVie Global Enterprises Ltd. ("AbbVie Global", an affiliate entity of AbbVie), pursuant to which the Company regained exclusive worldwide rights to develop CX-2029, a CD71-targeting conditionally activated antibody drug conjugate. The Transition Agreement supersedes the CD71 Agreement that was terminated in May 2023, and grants certain intellectual property rights from AbbVie Global to enable the continued development of CX-2029 by the Company for all human and nonhuman diagnostic, prophylactic, and therapeutic uses. Pursuant to the Transition Agreement, AbbVie Global is eligible to receive tiered sales royalties for CX-2029 ranging from the low-to-mid single digit percentages. In the fourth quarter of 2023, the Company decided to not to make any further substantial investments in the CX-2029 program in the near-term but continues to view CD71 as a target of strategic interest, including novel next-generation strategies. Amgen, Inc. On September 29, 2017, the Company and Amgen, Inc. (“Amgen”) entered into a Collaboration and License Agreement (the “Amgen Agreement”). Pursuant to the Amgen Agreement, the Company received an upfront payment of $ 40.0 million in October 2017. Concurrent with the Amgen Agreement, the Company and Amgen entered into a Share Purchase Agreement pursuant to which Amgen purchased 1,156,069 shares of the Company’s common stock at a price of $ 17.30 per share for total proceeds of $ 20.0 million. In October 2021, CytomX and Amgen executed an amendment to the Amgen Agreement primarily to (1) extend the target selection date for Amgen to select its additional targets for research and development, and (2) reduce the total number of milestone events and increase the total amount of milestone payments for EGFR Products. In each of May 2023 and March 2024, CytomX and Amgen executed an amendment to the Amgen Agreement to extend the target selection period for Amgen to select its additional targets for research and development as further discussed below. Under the terms of the Amgen Agreement, as amended, the Company and Amgen will co-develop a conditionally activated T-cell engagers (“TCEs”) targeting epidermal growth factor receptor (the “EGFR Products”). The Company is responsible for early-stage development of EGFR Products and Amgen will be responsible for late-stage development and commercialization of EGFR Products. Following early-stage development, the Company will have the right to elect to participate financially in the global co-development of EGFR Products with Amgen, during which the Company would bear a certain percentage of the worldwide development costs for EGFR Products and Amgen would bear the rest of such costs (the “EGFR Co-Development Option”). If the Company exercises its EGFR Co-Development Option, the Company will share in somewhat less than 50 % of the profit and losses from sales of such EGFR Products in the U.S., subject to certain caps, offsets, and deferrals. If the Company chooses not to exercise its EGFR Co-Development Option, the Company will not bear any costs of later stage development. The Company is also eligible to receive up to $ 460.0 million in development, regulatory, and commercial milestone payments for EGFR Products, and royalties in the low-double-digit to mid-teen percentage of worldwide commercial sales, provided that if the Company exercises its EGFR Co-Development option, it shall receive a profit and loss split of sales in the United States and royalties in the low-double-digit to mid-teen percentage of commercial sales outside of the United States. In January 2022, the IND for the EGFR product (CX-904) was allowed to proceed by the U.S. Food and Drug Administration (“FDA”). Amgen also has the right to select a total of up to three targets, including the two additional targets discussed below. The Company and Amgen collaborate in the research and development of conditionally activated T-cell engaging bispecifics therapies directed against such targets. Amgen has selected one such target (the “Amgen Other Product”). If Amgen exercises its option within a specified period of time, it can select two such additional targets (the “Amgen Option Products” and, together with the Amgen Other Product, the “Amgen Products”). Except with respect to preclinical activities to be conducted by CytomX, Amgen will be responsible, at its expense, for the development, manufacture, and commercialization of all Amgen Products. If Amgen exercises all of its options and advances all three of the Amgen Products, CytomX is eligible to receive up to $ 950.0 million in upfront, development, regulatory, and commercial milestones and tiered high single-digit to low-teen percentage royalties. The Company concluded that, at the inception of the agreement and subsequent amendments, Amgen’s option to select the two additional targets is not a material right and does not represent a performance obligation of the agreement. At the initiation of the collaboration, CytomX had the option to select from programs specified in the Amgen Agreement, an existing preclinical stage TCE product from the Amgen preclinical pipeline. In March 2018, CytomX selected the program and this program is currently in preclinical development. CytomX is responsible, at its expense, for converting this program to a conditionally activated TCE product, and thereafter, will be responsible for development, manufacturing, and commercialization of the product (“CytomX Product”). Amgen is eligible to receive up to $ 203.0 million in development, regulatory, and commercial milestone payments for the CytomX Product, and tiered mid-single digit to low double-digit percentage royalties. As of March 31, 2024 and December 31, 2023, deferred revenue related to the EGFR Products performance obligation was $ 11.5 million and $ 12.8 million, respectively. Deferred revenue related to the Amgen Other Products performance obligation was immaterial as of March 31, 2024 and December 31, 2023. Astellas Pharma Inc. The Company and Astellas Pharma, Inc. (“Astellas”) entered into a Collaboration and License Agreement (the “Astellas Agreement”) on March 23, 2020, the effective date, to collaborate on preclinical research activities to discover and develop certain antibody compounds for the treatment of cancer using the Company’s PROBODY therapeutic technology. Under the terms of the Astellas Agreement, the Company granted Astellas an exclusive, worldwide right to develop and commercialize PROBODY therapeutics for up to four collaboration targets including one initial target and three additional targets (“Additional Targets”). In addition, Astellas had the right to expand the number of Additional Targets from three up to five (the “Expansion Option”) before the third anniversary of the effective date. Furthermore, for a specified number of targets, at a pre-specified time prior to the initiation of the first pivotal study of a product against such target, the Company may elect to participate in certain development costs and share in the profits generated in the United States with respect to such product (“Cost Share Option”). The Cost Share Option, if exercised, will also provide the option for the Company to co-commercialize such product in the United States. The Company does not consider the Cost Share Option as a performance obligation at the inception of the agreement as participation is at the Company’s discretion. Pursuant to the Astellas Agreement, the consideration from Astellas is comprised of an upfront fee of $ 80.0 million and contingent payments for development, regulatory and sales milestones of up to an aggregate of approximately $ 1.6 billion. The Company is also entitled to tiered royalties from high-single digit to mid-teen percentage royalties from potential future sales. Astellas is responsible for all preclinical research costs incurred by either party as set forth in the preclinical research plan and the Company will receive research and development service fees based on a prescribed full-time employee ("FTE") rate. In January 2023, the Company announced that it achieved a clinical candidate milestone under the Astellas Agreement which triggered a $ 5.0 million milestone payment to the Company. The $ 5.0 million milestone payment was fully recognized in the first quarter of 2023 as the Company had completed its related performance obligation of the collaboration target which resulted in the clinical candidate nomination for further development. In March 2024, the Company announced that it achieved the good laboratory practices ("GLPs") toxicology milestone for this candidate which triggered a $ 5.0 million milestone payment to the Company. The $ 5.0 million milestone payment was fully recognized in the first quarter of 2024 as the Company had completed its related performance obligation of the collaboration target. Also, in March 2024, the Company announced that it achieved a clinical candidate milestone for a second collaboration target under the Astellas Agreement which triggered an additional $ 5.0 million milestone payment to the Company. The $ 5.0 million milestone payment was fully recognized in the first quarter of 2024 as the Company had completed its related performance obligation of the collaboration target which resulted in the clinical candidate nomination for further development. As of March 31, 2024 and December 31, 2023, deferred revenue relating to the Astellas Agreement was $ 27.6 million and $ 31.0 million, respectively. The amount due from Astellas under the Astellas Agreement wa s $ 12.1 million as of March 31, 2024 which included the $ 10.0 million of milestone payments earned in March 2024, and $ 2.2 million as of December 31, 2023. Bristol Myers Squibb Company On May 23, 2014, the Company and Bristol Myers Squibb Company (“Bristol Myers Squibb”) entered into a Collaboration and License Agreement (the “BMS Agreement”) to discover and develop compounds for use in human therapeutics aimed at multiple immuno-oncology targets using the Company’s PROBODY therapeutic technology. The effective date of the BMS Agreement was July 7, 2014. Under the terms of the BMS Agreement, the Company granted Bristol Myers Squibb exclusive worldwide rights to develop and commercialize PROBODY therapeutics for up to four oncology targets. Bristol Myers Squibb had additional rights to substitute up to two collaboration targets within three years of the effective date of the BMS Agreement. These rights expired in May 2017. Each collaboration target had a two-year research term and the two additional targets had to be nominated by Bristol Myers Squibb within five years of the effective date of the BMS Agreement. The research term for each collaboration target could be extended in one year increments up to three times. Pursuant to the BMS Agreement, the financial consideration from Bristol Myers Squibb was comprised of an upfront payment of $ 50.0 million and estimated research and development service fees, and the Company was initially entitled to receive contingent payments of up to $ 25.0 million for additional targets and contingent payments for development, regulatory and sales milestones. In addition, the Company was entitled to royalty payments in the mid-single digits to low double-digit percentages from potential future sales. On March 17, 2017, the Company and Bristol Myers Squibb amended the BMS agreement and entered into Amendment Number 1 to Extend Collaboration and License Agreement (“Amendment 1”). Amendment 1 granted Bristol Myers Squibb exclusive worldwide rights to develop and commercialize PROBODY therapeutics for up to eight additional targets. The effective date of Amendment 1 was April 25, 2017 (“Amendment Effective Date”). Under the terms of Amendment 1, the Company continued to have obligations to Bristol Myers Squibb to discover and conduct preclinical development of PROBODY therapeutics against any targets they chose to select during the research period under the terms of Amendment 1. Pursuant to Amendment 1, the financial consideration from Bristol Myers Squibb was comprised of an upfront payment of $ 200.0 million, estimated research and development service fees, and contingent payments for development, regulatory and sales milestones for the eight targets. The Company was also entitled to tiered mid-single to low double-digit percentage royalties from potential future sales. Amendment 1 did not change the term of Bristol Myers Squibb’s royalty obligation under the BMS Agreement. Bristol Myers Squibb’s royalty obligation continues on a licensed-product by licensed-product basis until the later of (i) the expiration of the last claim of the licensed patents covering the licensed products in the country, (ii) the twelfth anniversary of the first commercial sale of a licensed product in a country, or (iii) the expiration of any applicable regulatory, pediatric, orphan drug or data exclusivity with respect to such product. The initial transaction price for the BMS Agreement and Amendment 1, collectively, was $ 304.7 million consisting of the upfront fees of $ 250.0 million, target selection fees for the third and fourth targets of $ 25.0 million, estimated research and development service fees of $ 17.7 million and milestone payments received up to January 1, 2018, of $ 12.0 million. The Company determined that the remaining potential milestone payments were probable of significant revenue reversal as their achievement was highly dependent on factors outside the Company’s control. Therefore, these payments were fully constrained and were not included in the transaction price upon the adoption of ASC 606 on January 1, 2018. The initial transaction price for the combined obligation for each collaboration target is recognized using an input measure. In February 2021, the Company and Bristol Myers Squibb amended the BMS agreement and entered into Amendment Number 2 to amend the Collaboration and License Agreement (“Amendment 2”), as previously amended by Amendment 1. Subsequent to Amendment 2, in addition to Bristol Myers Squibb’s ongoing development of the CTLA-4 program, Bristol Myers Squibb also had the exclusive worldwide rights to develop and commercialize PROBODY therapeutics for up to five oncology targets. Under the terms of Amendment 2, the period for target selection was extended and in 2022, all remaining targets were selected. The Company will continue to collaborate with Bristol Myers Squibb to discover and conduct preclinical development of PROBODY therapeutics against targets selected by Bristol Myers Squibb over the estimated research period, which is projected to end in April 2025. Pursuant to Amendment 2, the Company was eligible to receive contingent payments for development, regulatory and sales milestones. It is also entitled to tiered mid-single to low double-digit percentage of royalties from potential future sales. The Company accounted for Amendment 2 as a modification and reallocated the remaining unrecognized transaction price to the remaining performance obligations. In October 2022, the Company and Bristol Myers Squibb amended the BMS Agreement and entered into Amendment Number 3 (“Amendment 3”), as previously amended by Amendment 1 and Amendment 2, to clarify the rights and restrictions of certain new proprietary antibodies that the parties exchanged. There were no substantive changes to each party's performance obligations. In March 2024, following a Bristol Myers Squibb corporate portfolio prioritization process, Bristol Myers Squibb notified CytomX that it does not intend to continue the development of BMS-986288 beyond the current Phase 2 study and terminated its collaboration license on the CTLA-4 target under the collaboration. As of March 31, 2024, the Company is eligible to receive approximately $ 1.8 billion in contingent payments for development, regulatory and sales milestones for the ongoing collaboration programs. The Company reevaluated the remaining potential milestone payments and determined that significant revenue reversal was probable as the achievement of such milestones was highly dependent on factors outside the Company’s control. As a result, these payments continued to be fully constrained and were not included in the transaction price as of March 31, 2024. As of March 31, 2024 and December 31, 2023, deferred revenue relating to the BMS Agreement was $ 100.3 million and $ 119.9 million, respectively. ModernaTX, Inc. The Company and ModernaTX, Inc. (“Moderna”) entered into a Collaboration and License Agreement (the “Moderna Agreement”) on December 30, 2022, the effective date, to collaborate on discovery and preclinical research and development activities to create investigational messenger RNA (mRNA) based conditionally activated therapies using the Company’s PROBODY therapeutic technology. Moderna is solely responsible for the development (preclinical and clinical), manufacturing, and commercialization of any products under the Moderna Agreement. Under the terms of the Moderna Agreement, the Company granted Moderna an exclusive, worldwide right to develop and commercialize PROBODY therapeutics for the collaboration programs. In exchange, the Company received an upfront payment of $ 35.0 million in January 2023, including $ 5.0 million of prepaid research and development service fees. The Company will continue to receive research and development service fees according to the preclinical research work plans based on a prescribed FTE rate and is eligible to receive up to approximately $ 1.2 billion in future development, regulatory, and commercial milestone payments. The Company is also eligible to receive tiered royalties from high-single digit to low-teen percentage rates of annual global net sales of any products that are commercialized under the Moderna Agreement. The Moderna Agreement also provided Moderna with an option to participate in an equity financing by CytomX at market price, subject to certain terms, conditions and regulatory requirements. As of March 31, 2024 and December 31, 2023, deferred revenue relating to the Moderna Agreement was $ 21.5 million and $ 24.2 million, respectively. Regeneron Pharmaceuticals, Inc. The Company and Regeneron Pharmaceuticals Inc. (“Regeneron”) entered into a Collaboration and License Agreement (the “Regeneron Agreement”) on November 16, 2022, to collaborate on creation of conditionally-activated investigational bispecific cancer therapies utilizing the Company’s PROBODY® therapeutic platform and Regeneron’s Veloci-Bi® bispecific antibody development platform. The Company and Regeneron will collaborate on preclinical research and discovery activities for initially agreed upon collaboration programs (“Collaboration Program”) with an option to expand additional Collaboration Programs (“Additional Collaboration Program Option”). Under the Collaboration and License Agreement, the Company granted Regeneron an exclusive, worldwide, royalty-bearing license under certain Company intellectual property to develop, manufacture, commercialize and otherwise exploit licensed products (“Licensed Products”) for all human and non-human diagnostic, prophylactic and therapeutic uses in oncology. Regeneron is responsible for funding the cost of preclinical research and discovery activities of both parties for all Licensed Products and for funding the cost of development, manufacturing and commercialization of all Licensed Products worldwide. Pursuant to the Regeneron Agreement, the consideration from Regeneron is comprised of an upfront fee of $ 30.0 million, contingent payments for development and regulatory milestones and commercial milestone payments of up to an aggregate of approximately $ 0.8 billion. If Regeneron exercises its Additional Collaboration Program Option, the Company would be eligible to receive additional upfront and milestone payments aggregating up to approximately $ 1.2 billion. The Company is also entitled to tiered royalties from high-single digit to low-teen percentage royalties from potential future sales. In addition, the Company will receive research and development service fees based on a prescribed FTE rate. As of March 31, 2024 and December 31, 2023, deferred revenue relating to the Regeneron Agreement was $ 22.5 million and $ 24.4 million, respectively. The amount due from Regeneron under the Regeneron Agreement was $ 1.0 million and $ 1.1 million as of March 31, 2024 and December 31, 2023, respectively. Contract Liabilities The following table presents changes in the Company’s total contract liabilities during the three months ended March 31, 2024 and 2023: Deferred Revenue (in thousands) December 31, 2023 $ 212,315 Additions 2,266 Revenue recognized ( 31,210 ) March 31, 2024 $ 183,371 December 31, 2022 $ 301,326 Additions 869 Revenue recognized ( 18,278 ) March 31, 2023 $ 283,917 The Company expects that the $ 183.4 million of deferred revenue related to the following contracts as of March 31, 2024 will be recognized as revenue based on actual FTE effort and estimated program progress as set forth below. However, the timing of revenue recognition could differ from the estimates depending on facts and circumstances impacting the various contracts, including progress of research and development, resources assigned to the contracts by the Company or its collaboration partners or other factors outside of the Company’s control. • The $ 11.5 million of deferred revenue related to the Amgen EGFR Products is expected to be recognized until 2026 . • The $ 27.6 million of deferred revenue related to the Astellas Agreement is expected to be recognized until 2026 . • The $ 100.3 million of deferred revenue related to the BMS Agreement is expected to be recognized through the second quarter of 2025 . • The $ 21.5 million of deferred revenue related to the Moderna Agreement, together with research and development service fees, is expected to be recognized until 2027 . • The $ 22.5 million of deferred revenue related to the Regeneron Agreement, together with research and development service fees, is expected to be recognized until 2026 .

License Agreement

License Agreement	3 Months Ended
License Agreement	Mar. 31, 2024
Research and Development [Abstract]
License Agreement	7. License Agreement UCSB Agreement In August 2010, the Company entered into an exclusive, worldwide license agreement with University of California, Santa Barbara (“UCSB”), relating to the use of certain patents and technology relating to its core technology, including its therapeutic antibodies, and to certain patent rights the Company co-owns with UCSB covering PROBODY antibodies and other pro-proteins (the “UCSB Agreement”). Pursuant to the UCSB Agreement, the Company is obligated to (i) make royalty payments to UCSB on net sales of its products covered under the agreement, subject to annual minimum amounts, (ii) make milestone payments to UCSB upon the occurrence of certain events, (iii) make a milestone payment to UCSB upon occurrence of an IPO or change of control, and (iv) reimburse UCSB for prosecution and maintenance of the licensed patents. As part of the UCSB Agreement, the Company has annual minimum royalty obligations of $ 0.2 million under the terms of certain exclusive licensed patent rights. In April 2019, the Company entered into Amendment No.3 to the UCSB Agreement to adjust and clarify certain sublicense terms (“Amendment No.3”). Under the terms of Amendment No.3, the Company and UCSB agreed to modify the determination of sublicense revenues payable by the Company to UCSB on certain existing collaboration agreements and on collaboration agreements executed subsequent to Amendment No.3. In exchange, the Company agreed to make an upfront payment of $ 1.0 million as well as additional annual license maintenance fees of $ 0.8 million through 2031 . In March 2024, the Company incurred $ 0.6 million of sublicense fees triggered by achieving the GLP toxicology studies milestone for the first clinical candidate which was nominated by Astellas in 2023, as well as by achieving the clinical candidate nomination milestone for a second collaboration target under the Astellas Agreement. For the three months ended March 31, 2024 and 2023, the Company incurred sublicense expenses of $ 1.6 million and $ 1.1 million, respectively, under the provisions of the UCSB Agreement. ImmunoGen (acquired by AbbVie in 2024) In December 2019, the Company entered into a License Agreement (the “ImmunoGen 2019 License”) with ImmunoGen, Inc. to obtain an exclusive license with respect to epithelial cell adhesion molecule (“EPCAM”). Under the ImmunoGen 2019 License, ImmunoGen agreed to transfer its know-how, patents, intellectual property rights, and technology transfer materials and information related to its EpCAM program. The license gives the Company the sole ability to develop, manufacture, use and commercialize any licensed product that incorporates, is comprised of, or otherwise derived from PROBODY technology that targets EpCAM in any human therapeutic field on a worldwide basis. In April 2024, the Company incurred a $ 5.0 million milestone payable to ImmunoGen with respect to achieving the milestone of dosing the first patient for CX-2051 under the ImmunoGen 2019 License Agreement.

Stock-Based Compensation

Stock-Based Compensation	3 Months Ended
Stock-Based Compensation	Mar. 31, 2024
Share-Based Payment Arrangement [Abstract]
Stock-Based Compensation	8. Stock-Based Compensation Stock Options Activities for the Company’s stock option plans for the three months ended March 31, 2024 were as follows: Options Outstanding Number of Weighted- Balance at December 31, 2023 12,949,612 $ 7.16 Options granted 1,780,000 1.68 Options exercised ( 119,874 ) 1.57 Option forfeited/expired ( 303,341 ) 11.03 Balance at March 31, 2024 14,306,397 $ 6.44 The Company recorded $ 1.4 million and $ 1.9 million of stock-based compensation expense related to the stock option plans for the three months ended March 31, 2024 and 2023, respectively. Time-based RSUs ("TRSU") Activities for the Company’s TRSUs for the three months ended March 31, 2024 were as follows: Number of Weighted Average Grant Date Fair Value Per Share Balance at December 31, 2023 1,400,529 $ 2.40 RSU's awarded 1,117,333 1.62 RSU's vested ( 706,923 ) 2.14 RSU's cancelled ( 28,139 ) 1.76 Balance at March 31, 2024 1,782,800 $ 2.02 The Company recorded $ 0.4 million and $ 0.4 million of stock-based compensation expense related to the TRSUs for the three months end March 31, 2024 and 2023, respectively. Performance-based RSUs ("PSUs") 2022 PSU In August 2022, the Company granted 250,000 PSUs to executive employees with an aggregated grant date fair value of approximately $ 0.4 million. Vesting for 50% of the PSUs granted was set to occur upon attaining certain specific milestones by December 2023 (“2022-Tranche 1”), and the remaining 50% are set to vest upon attaining certain specific milestones by December 2024 (“2022-Tranche 2”). In December 2023, the Company determined that the performance conditions for 2022-Tranche 1 was satisfied and the award was vested in December 2023. As a result, the Company recorded $ 55,000 and the remaining $ 128,000 c ompensation cost for the 2022-Tranche 1 award for the year ended December 31, 2022 and 2023, respectively. As of March 31, 2024 and December 31, 2023, the Company determined that it is probable that the performance conditions for the 2022-Tranche 2 will be satisfied and recorded $ 19,000 and $ 106,000 compensation cost for the award for the three months ended March 31, 2024 and for the fiscal year 2023, respectively. 2023 PSU In February 2023, the Company granted 760,000 PSUs to executive employees with an aggregated grant date fair value of approximately $ 1.9 million. Vesting for 50% of the PSUs granted will occur upon attaining certain specific milestones by December 2024 (“2023-Tranche 1”), and the remaining 50% will vest upon attaining certain specific milestones by December 2025 (“2023-Tranche 2”). The Company determined that it is not probable that the performance conditions will be satisfied for each of these tranches and hence no compensation cost was recorded for these awards through March 31, 2024. 2024 PSU In January 2024, the Company granted 810,000 PSUs to executive employees with an aggregated grant date fair value of approximately $ 1.3 million. Vesting for 50% of the PSUs granted will occur upon attaining certain specific milestones by December 2025 (“2024-Tranche 1”), and the remaining 50% will vest upon attaining certain specific milestones by December 2026 (“2024-Tranche 2”). The Company determined that it is not probable that the performance conditions will be satisfied for each of these tranches and hence no compensation cost was recorded for these awards through March 31, 2024. Activities for the Company’s PSUs for the three months ended March 31, 2024, were as follows: Number of Weighted Average Grant Date Fair Value Per Share Balance at December 31, 2023 875,000 $ 2.41 PSU's awarded 810,000 1.66 Balance at March 31, 2024 1,685,000 $ 2.05 Stock-based Compensation Total stock-based compensation recorded was as follows: Three Months Ended March 31, 2024 2023 (in thousands) Research and development $ 707 $ 961 General and administrative 1,200 1,448 Total stock-based compensation expense $ 1,907 $ 2,409

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
Commitments and Contingencies	Mar. 31, 2024
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	9. Commitments and Contingencies Legal Proceedings On March 4, 2020 , Vytacera Bio, LLC filed a patent infringement lawsuit against the Company in the U.S. District Court for the District of Delaware. The lawsuit alleges that the Company's use, offers to sell, and/or sales of the PROBODY® technology platform for basic research applications constitutes infringement. The complaint seeks unspecified monetary damages. In September 2022, the Company filed a motion to dismiss the case and the Court granted the parties’ stipulation to stay all pending case deadlines until that motion is finally resolved. On October 30, 2023, Magistrate Judge Burke issued a Report & Recommendation that recommended granting Company’s motion to dismiss all counts of the complaint. In January 2024, the case was transferred to a new Judge and the case will remain stayed pending a ruling by the trial judge on the Magistrate’s Report & Recommendation. The Company believes that the lawsuit is without merit and intends to vigorously defend itself. The Company does not believe a loss is probable and has no t recorded any amount as a contingent liability for claims associated with this lawsuit as of March 31, 2024.

Income Taxes

Income Taxes	3 Months Ended
Income Taxes	Mar. 31, 2024
Income Tax Disclosure [Abstract]
Income Taxes	10. Income Taxes The Company maintains a full valuation allowance against its net deferred tax assets due to the Company’s history of losses through December 31, 2023 . The Company files income taxes in the U.S. federal jurisdiction, the state of California and various other U.S. states. The state of California contested the Company’s tax position on revenue apportionment for upfront and milestone payments resulting from the Company’s collaboration and licensing agreements for the years 2017 and 2018. In September 2023, the Company received Notice of Proposed Assessment (“NOPA”) from the Franchise Tax Board. The Company recorded an uncertain tax position of $ 3.9 million in long term liabilities for the proposed tax assessment, penalties and interest through March 31, 2024 . Of the unrecognized tax benefits as of March 31, 2024, approximately $ 3.9 million would affect the Company’s effective tax rate if recognized. In addition, utilization of carryforward attributes and indirect federal tax effects of the assessment would result in a reduction in deferred tax assets of $ 5.1 million. The Company filed a protest to contest the proposed assessment in November 2023. Due to the ongoing n ature of the examination and discussions with the state of California, the Company is unable to estimate a date by which this matter will be resolved.

Subsequent Event

Subsequent Event	3 Months Ended
Subsequent Event	Mar. 31, 2024
Subsequent Events [Abstract]
Subsequent Event	11. Subsequent Event In February 2020, the Company entered into the Open Market Sale Agreement (the “Sales Agreement”) with Jefferies LLC (“Jefferies”), to sell its common stock, at par value $ 0.00001 per share, with aggregate gross sales proceeds of up to $ 75,000,000 , from time to time upon the Company’s request, through an at the market offering under which Jefferies will act as sales agent. Pursuant to the Sales Agreement, Jefferies as the sales agent will receive a commission of 3.0 % of the gross sales price for shares of common stock sold under the Sales Agreement. In April 2024, under the Sales Agreement, the Company sold 2,270,608 shares at an average price of $ 2.20 per share and received net proceeds of approximately $ 4.8 million after deducting the 3.0 % sales commission and related issuance cost. In June 2023, the Company entered into an agreement with BVF Partners L.P. (“BVF”) for a private placement and received an aggregate net proceeds of approximately $ 29.7 million in July 2023, after deducting issuance costs of approximately $ 0.3 million. In the private placement, CytomX issued pre-funded warrants to BVF to purchase up to 14,423,077 shares of common stock, accompanying Tranche 1 warrants to purchase up to 5,769,231 shares of common stock and accompanying Tranche 2 warrants to purchase up to 5,769,231 shares of common stock, at a combined price of $ 2.08 per share. On May 1, 2024, BVF exercised its right to purchase 7.5 million shares of common stock at an exercise price of $ 0.00001 per share.

Basis of Presentation and Sum_2

Basis of Presentation and Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2024
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying interim condensed financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and applicable rules and regulations of the U.S. Securities and Exchange Commission (“SEC”) regarding interim financial reporting.
Unaudited Interim Financial Information	Unaudited Interim Financial Information The accompanying interim condensed financial statements and related disclosures are unaudited, have been prepared on the same basis as the annual financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary for a fair statement of the results of operations for the periods presented. The condensed results of operations for the three months ended March 31, 2024 are not necessarily indicative of the results to be expected for the full year or for any other future year or interim period. The accompanying condensed financial statements should be read in conjunction with the audited financial statements and the related notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2023 filed with the SEC.
Use of Estimates	Use of Estimates The preparation of the financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent liabilities at the date of the financial statements and reported amounts of revenues and expenses during the reporting periods. Actual results could differ from those estimates.
Cash, Cash Equivalents and Restricted Cash	Cash, Cash Equivalents and Restricted Cash The Company considers all highly liquid investments purchased with original maturities of three months or less at the date of purchase to be cash equivalents. Restricted cash represents a standby letter of credit issued pursuant to an office lease.
Revenue Recognition	Revenue Recognition The Company’s revenues are primarily derived through its license, research, development and commercialization agreements. The terms of these types of agreements may include (i) licenses for the Company’s technology or programs, (ii) research and development services, and (iii) services or obligations in connection with participation in research or steering committees. Payments to the Company under these arrangements typically include one or more of the following: nonrefundable upfront and license fees, research funding, milestone and other contingent payments to the Company for the achievement of defined collaboration objectives and certain preclinical, clinical, regulatory and sales-based events, as well as royalties on sales of any commercialized products. The Company assesses whether the promises in its arrangements with customers are distinct performance obligations that should be accounted for separately. Judgment is required to determine whether the license to the Company’s intellectual property is distinct from the research and development services or participation on steering committees. The Company’s collaboration and license agreements may include contingent payments related to specified research, development and regulatory milestones. Such milestone payments are typically payable under the collaborations when the collaboration partner claims or selects a target, or initiates or advances a covered product candidate in preclinical or clinical development, upon submission for marketing approval of a covered product with regulatory authorities, or upon receipt of actual marketing approvals of a covered product or for additional indications. Milestone payments that are not within the control of the Company or the licensee, such as regulatory approvals, are not considered probable of being achieved until those approvals are received. At each reporting date, the Company re-evaluates whether the milestones are considered probable of being achieved and estimates the amount to be included in the transaction price by using the most likely amount method. If it is probable that a significant revenue reversal would not occur, the associated milestone value is included in the transaction price in such period of determination. The Company’s collaboration and license agreements may also include contingent payments related to sales-based milestones. Sales-based milestones are typically payable when annual sales of a covered product reach specified levels. Sales-based milestones are recognized at the later of when the associated performance obligation has been satisfied or when the sales occur. Unlike other contingency payments, such as regulatory milestones, sales-based milestones are not included in the transaction price based on estimates at the inception of the contract; instead, they are included when the sales or usage occur. Due to the early stage of the Company’s licensed technology, the license of such technology is typically combined with research and development services and steering committee participation as one performance obligation. Under the collaboration and license agreements, each collaboration target or program is generally considered to be a separate combined performance obligation. The transaction price in each arrangement is allocated to the identified performance obligations based on the relative standalone selling price (“SSP”) of each distinct performance obligation, which requires judgment. In instances where SSP is not directly observable, such as when a license or service is not sold separately, SSP is determined using information that may include market conditions and other observable inputs. Variable consideration is allocated to certain performance obligations if it is triggered by the Company’s efforts to satisfy or a specific outcome from satisfying these performance obligations. In the event that the Company receives non-cash consideration such as consideration in the form of a research license and research support services from the counterparty, the transaction price of a non-monetary exchange that has commercial substance is estimated based on the fair value of the non-cash consideration received, which may be determined through a valuation analysis. The Company recognizes revenue from upfront payments over the estimated period of performance under the agreement using an input method for the performance obligation. In applying the input method of revenue recognition, the Company uses actual full-time equivalent (FTE) hours incurred relative to estimated total FTE hours expected to be incurred for each combined performance obligation over the estimated research service period of each collaboration target. In certain cases, the Company’s performance creates an asset that does not have an alternative use to the customer and the Company has an enforceable right to payment at all times for performance completed to date. In these cases, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. Any consideration payable to the Company’s customers is treated as a reduction to the transaction price and revenue, unless the payment to the customer is in exchange for distinct good and services.
Contract Balances	Contract Balances Customer payments are recorded as deferred revenue upon receipt or when due and may require deferral of revenue recognition to a future period until the Company satisfies its performance obligations under these arrangements. Amounts payable to the Company are recorded as accounts receivable when the Company’s right to consideration is unconditional.
Recently Issued Accounting Standards Not Yet Adopted	Recently Issued Accounting Standards Not Yet Adopted In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures ("ASU 2023-09"), which enhances transparency in income tax disclosures. ASU 2023-09 require entities to disclose (1) specific categories in the rate reconciliation, (2) the income or loss from continuing operations before income tax expense or benefit (separated between domestic and foreign) and (3) income tax expense or benefit from continuing operations (separated by federal, state and foreign). ASU 2023-09 also requires entities to disclose their income tax payments to international, federal, state and local jurisdictions, among other changes. The amendments are set to be effective for fiscal years beginning after December 15, 2024, and are required to be applied on a prospective basis. The Company is evaluating the impact on our financial statements. Other accounting standards that have been issued or proposed by the FASB or other standards-setting bodies that do not require adoption until a future date are not expected to have a material impact on the Company’s consolidated financial statements upon adoption.

Net Income (Loss) Per Share (Ta

Net Income (Loss) Per Share (Tables)	3 Months Ended
Net Income (Loss) Per Share (Tables)	Mar. 31, 2024
Earnings Per Share [Abstract]
Summary of Calculation of Basic and Diluted Net Income (Loss) Per Share	The following table presents the calculation of basic and diluted net income (loss) per share: Three Months Ended March 31, 2024 2023 (in thousands, except share and per share data) Numerator: Net income (loss) $ 13,791 $ ( 3,311 ) Denominator: Basic Weighted-average common shares outstanding 67,606,389 66,248,992 Weighted-average pre-funded warrants 14,423,077 — Weighted-average common shares outstanding used to calculate basic net income (loss) per share 82,029,466 66,248,992 Diluted Weighted-average common shares outstanding used to calculate basic net income (loss) per share 82,029,466 66,248,992 Effect of potentially dilutive securities: Stock options, ESPP & RSUs 600,554 — Weighted-average common shares outstanding used to calculate diluted net income (loss) per share 82,630,020 66,248,992 Net income (loss) per share Basic $ 0.17 $ ( 0.05 ) Diluted $ 0.17 $ ( 0.05 )
Summary of Potentially Dilutive Securities Excluded from Computation of Diluted Net Income (Loss) Per Share	The following weighted-average outstanding shares of potentially dilutive securities are excluded from the computation of diluted net income (loss) per share for the periods presented, because including them would have been anti-dilutive: Three Months Ended March 31, 2024 2023 Options and ESPP to purchase common stock 13,710,289 13,986,524 Common stock warrants 11,538,462 — RSUs 227,525 1,539,053 Total 25,476,276 15,525,577

Fair Value Measurements and I_2

Fair Value Measurements and Investments (Tables)	3 Months Ended
Fair Value Measurements and Investments (Tables)	Mar. 31, 2024
Fair Value Disclosures [Abstract]
Schedule of Investments Subject to Fair Value Measurements on a Recurring Basis	The following tables set forth the fair value of the Company’s investments subject to fair value measurements on a recurring basis and the level of inputs used in such measurements: March 31, 2024 Valuation Amortized Gross Aggregate (in thousands) Assets Money market funds Level I $ 39,069 $ — $ 39,069 Restricted cash (money market funds) Level I 917 — 917 U.S. Treasury Securities Level II 114,109 ( 10 ) 114,099 Total $ 154,095 $ ( 10 ) $ 154,085 December 31, 2023 Valuation Amortized Gross Aggregate (in thousands) Assets Money market funds Level I $ 17,109 $ — $ 17,109 Restricted cash (money market funds) Level I 917 — $ 917 U.S. Treasury Securities Level II 157,243 95 $ 157,338 Total $ 175,269 $ 95 $ 175,364

Accrued Liabilities (Tables)

Accrued Liabilities (Tables)	3 Months Ended
Accrued Liabilities (Tables)	Mar. 31, 2024
Accrued Liabilities, Current [Abstract]
Schedule of Accrued Liabilities	Accrued liabilities consisted of the following: March 31, December 31, 2024 2023 (in thousands) Research and clinical expenses $ 7,701 $ 8,435 Payroll and related expenses 4,855 8,160 Legal and professional expenses 1,209 690 Other accrued expenses 455 314 Total $ 14,220 $ 17,599

Collaboration and License Agr_2

Collaboration and License Agreements (Tables)	3 Months Ended
Collaboration and License Agreements (Tables)	Mar. 31, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Revenue by Collaboration Partners	The following table summarizes the revenue by collaboration partner: Three Months Ended 2024 2023 (in thousands) AbbVie $ — $ 3,988 Amgen 1,279 1,776 Astellas 15,452 8,705 Bristol Myers Squibb 19,634 7,725 Regeneron 2,393 581 Moderna 2,705 724 Total revenue $ 41,463 $ 23,499
Summary of Contract Liabilities	The following table presents changes in the Company’s total contract liabilities during the three months ended March 31, 2024 and 2023: Deferred Revenue (in thousands) December 31, 2023 $ 212,315 Additions 2,266 Revenue recognized ( 31,210 ) March 31, 2024 $ 183,371 December 31, 2022 $ 301,326 Additions 869 Revenue recognized ( 18,278 ) March 31, 2023 $ 283,917

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	3 Months Ended
Stock-Based Compensation (Tables)	Mar. 31, 2024
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Schedule of Activities Under Company's Stock Option Plans	Activities for the Company’s stock option plans for the three months ended March 31, 2024 were as follows: Options Outstanding Number of Weighted- Balance at December 31, 2023 12,949,612 $ 7.16 Options granted 1,780,000 1.68 Options exercised ( 119,874 ) 1.57 Option forfeited/expired ( 303,341 ) 11.03 Balance at March 31, 2024 14,306,397 $ 6.44
Total Stock-based Compensation Recognized	Total stock-based compensation recorded was as follows: Three Months Ended March 31, 2024 2023 (in thousands) Research and development $ 707 $ 961 General and administrative 1,200 1,448 Total stock-based compensation expense $ 1,907 $ 2,409
Time based RSUs
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Schedule of Company's TRSU Activities	Activities for the Company’s TRSUs for the three months ended March 31, 2024 were as follows: Number of Weighted Average Grant Date Fair Value Per Share Balance at December 31, 2023 1,400,529 $ 2.40 RSU's awarded 1,117,333 1.62 RSU's vested ( 706,923 ) 2.14 RSU's cancelled ( 28,139 ) 1.76 Balance at March 31, 2024 1,782,800 $ 2.02
Performance based RSUs
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Schedule of Activities for Company's PSUs	Activities for the Company’s PSUs for the three months ended March 31, 2024, were as follows: Number of Weighted Average Grant Date Fair Value Per Share Balance at December 31, 2023 875,000 $ 2.41 PSU's awarded 810,000 1.66 Balance at March 31, 2024 1,685,000 $ 2.05

Net Income (Loss) Per Share - S

Net Income (Loss) Per Share - Summary of Calculation of Basic and Diluted Net Income (Loss) Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Numerator:
Net Income (Loss)	$ 13,791	$ (3,311)
Basic
Weighted-average common shares outstanding	67,606,389	66,248,992
Weighted-average pre-funded warrants	14,423,077
Weighted Average Number of Shares Outstanding, Basic, Total	82,029,466	66,248,992
Effect of potentially dilutive securities:
Stock options, ESPP & RSUs	600,554
Weighted-average common shares, diluted	82,630,020	66,248,992
Net income (loss) per share
Basic	$ 0.17	$ (0.05)
Diluted	$ 0.17	$ (0.05)

Net Income (Loss) Per Share -_2

Net Income (Loss) Per Share - Summary of Potentially Dilutive Securities Excluded from Computation of Diluted Net Loss Per Share (Details) - shares	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	25,476,276	15,525,577
RSUs
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	227,525	1,539,053
Options and ESPP to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	13,710,289	13,986,524
Common stock warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	11,538,462	0

Fair Value Measurements and I_3

Fair Value Measurements and Investments - Schedule of Investments Subject to Fair Value Measurements on a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents	$ 36,185	$ 17,171	[1]
Aggregate Fair Value	154,085	175,364
Gross Unrealized Holding Gains		95
Investments, Gross Unrealized Losses	(10)
Amortized Cost	154,095	175,269
Level I \| Money market funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents	39,069	17,109
Level I \| Restricted cash (money market funds)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Restricted cash	917	917
Level II \| U.S. Treasury Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments, Amortized Cost	114,109	157,243
Investments, Gross Unrealized Gains		95
Investments, Gross Unrealized Losses	(10)
Investments, Aggregate Fair Value	$ 114,099	$ 157,338

[1] The condensed balance sheet as of December 31, 2023 was derived from the audited financial statements included in the Company's Annual Report on Form 10-K for the year ended December 31, 2023.

Accrued Liabilities - Summary o

Accrued Liabilities - Summary of Accrued Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Accrued Liabilities, Current [Abstract]
Research and clinical expenses	$ 7,701	$ 8,435
Payroll and related expenses	4,855	8,160
Legal and professional expenses	1,209	690
Other accrued expenses	455	314
Total	$ 14,220	$ 17,599	[1]

[1] The condensed balance sheet as of December 31, 2023 was derived from the audited financial statements included in the Company's Annual Report on Form 10-K for the year ended December 31, 2023.

Collaboration and License Agr_3

Collaboration and License Agreements - Schedule of Revenue by Collaboration Partners (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue	$ 41,463	$ 23,499
AbbVie
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue	0	3,988
Amgen
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue	1,279	1,776
Astellas
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue	15,452	8,705
Bristol Myers Squibb
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue	19,634	7,725
Regeneron
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue	2,393	581
Moderna
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue	$ 2,705	$ 724

Collaboration and License Agr_4

Collaboration and License Agreements - AbbVie Ireland Unlimited Company - Additional Information (Details) $ in Thousands	1 Months Ended
	Apr. 30, 2016 USD ($) Agreement	Mar. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)	Mar. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue		$ 183,371	$ 212,315	$ 283,917	$ 301,326
AbbVie Ireland Unlimited Company \| Collaborative Arrangement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of collaboration agreements \| Agreement	2
AbbVie Ireland Unlimited Company \| CD71 Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payments received	$ 100,000
Deferred revenue				$ 4,000

Collaboration and License Agr_5

Collaboration and License Agreements - Amgen, Inc - Additional Information (Details) $ / shares in Units, $ in Thousands		1 Months Ended
	Sep. 29, 2017 USD ($) Target	Oct. 31, 2017 USD ($) $ / shares shares	Mar. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)	Mar. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue			$ 183,371	$ 212,315	$ 283,917	$ 301,326
Amgen Inc \| EGFR Products
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue			11,500
Collaboration and License Agreement \| Amgen Inc
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment received		$ 40,000
Common stock, shares issuable under agreement \| shares		1,156,069
Common stock, shares issuable under agreement, price per share \| $ / shares		$ 17.3
Common stock, value of shares issued in connection with agreement		$ 20,000
Number of targets selected \| Target	1
Number of additional collaboration target \| Target	2
Collaboration and License Agreement \| Amgen Inc \| Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contingent payments payable	$ 203,000
Collaboration and License Agreement \| Amgen Inc \| EGFR Products
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue			$ 11,500	$ 12,800
Collaboration and License Agreement \| Amgen Inc \| EGFR Products \| Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contingent milestone payments receivable	$ 460,000
Percentage share of profit and losses	50%
Collaboration and License Agreement \| Amgen Inc \| Amgen Products \| Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contingent milestone payments receivable	$ 950,000
Number of targets \| Target	3

Collaboration and License Agr_6

Collaboration and License Agreements - Astellas Pharma Inc - Additional Information (Details) $ in Thousands		1 Months Ended	3 Months Ended
	Mar. 23, 2020 USD ($) Target	Jan. 31, 2023 USD ($)	Mar. 31, 2024 USD ($)	Mar. 31, 2023 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue			$ 183,371	$ 283,917	$ 212,315	$ 301,326
Astellas Pharma Inc.
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue			27,600
Collaboration and License Agreement \| Astellas Pharma Inc.
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of targets selected \| Target	1
Number of additional collaboration target \| Target	3
Upfront payment received	$ 80,000
Milestone payments received		$ 5,000	5,000	$ 5,000
Additional milestone payment received			5,000
Deferred revenue			27,600		31,000
Amount due from customer			12,100		$ 2,200
Milestone payment			$ 10,000
Collaboration and License Agreement \| Astellas Pharma Inc. \| Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of targets \| Target	4
Right to expand the number of additional collaboration target \| Target	5
Contingent milestone payments receivable	$ 1,600,000
Collaboration and License Agreement \| Astellas Pharma Inc. \| Minimum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Right to expand the number of additional collaboration target \| Target	3

Collaboration and License Agr_7

Collaboration and License Agreements - Bristol-Myers Squibb Company - Additional Information (Details) $ in Thousands			1 Months Ended	3 Months Ended
	Apr. 25, 2017 USD ($) Target	Jul. 07, 2014 USD ($) Term Target	Jan. 31, 2018 USD ($)	Mar. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)	Mar. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Mar. 17, 2017 Target
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue				$ 183,371	$ 212,315	$ 283,917	$ 301,326
Bristol Myers Squibb
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue				$ 100,300
Collaboration and License Agreement \| Maximum \| Bristol Myers Squibb
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of additional collaboration target \| Target								8
Collaborative Arrangement \| Bristol Myers Squibb
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration target research term		2 years
Number of additional collaboration target \| Target		2
Research terms				Each collaboration target had a two-year research term and the two additional targets had to be nominated by Bristol Myers Squibb within five years of the effective date of the BMS Agreement. The research term for each collaboration target could be extended in one year increments up to three times.
Extension of research term for each collaboration target		1 year
Upfront payment received	$ 200,000	$ 50,000
Contingent milestone payments receivable				$ 1,800,000
Number of research targets selected \| Target	8
Total transaction price		304,700
Upfront fee received		250,000
Research and development service fees		17,700
Milestone payment received			$ 12,000
Deferred revenue				$ 100,300	$ 119,900
Collaborative Arrangement \| Bristol Myers Squibb \| Third And Fourth Target
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Target selection fee		$ 25,000
Collaborative Arrangement \| Maximum \| Bristol Myers Squibb
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of oncology target \| Target		4
Number of collaboration target \| Target		2
Period of nomination of additional target from effective date		5 years
Times of increments for extended collaboration target research time \| Term		3
Collaborative Arrangement \| Maximum \| Bristol Myers Squibb \| Each Of Two Additional Targets
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contingent milestone payments receivable		$ 25,000

Collaboration and License Agr_8

Collaboration and License Agreements - ModernaTX, Inc - Additional Information (Details) - USD ($) $ in Thousands	1 Months Ended
	Jan. 31, 2023	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023	Dec. 31, 2022
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Deferred revenue		$ 183,371	$ 212,315	$ 283,917	$ 301,326
ModernaTX, Inc
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Deferred revenue		21,500
ModernaTX, Inc \| Collaboration and License Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront payment received	$ 35,000
Up front consideration pre paid research and development service fees	5,000
Deferred revenue		$ 21,500	$ 24,200
ModernaTX, Inc \| Collaboration and License Agreement \| Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Contingent milestone payments receivable	$ 1,200,000

Collaboration and License Agr_9

Collaboration and License Agreements - Regeneron Pharmaceuticals, Inc - Additional Information (Details) - USD ($) $ in Thousands	Nov. 16, 2022	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023	Dec. 31, 2022
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Deferred revenue		$ 183,371	$ 212,315	$ 283,917	$ 301,326
Regeneron Pharmaceuticals, Inc
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Deferred revenue		22,500
Collaborative Arrangement \| Regeneron Pharmaceuticals, Inc
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront payment received	$ 30,000
Collaboration and License Agreement \| Regeneron Pharmaceuticals, Inc
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Deferred revenue		22,500	24,400
Amount due from customer		$ 1,000	$ 1,100
Collaboration and License Agreement \| Regeneron Pharmaceuticals, Inc \| Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Contingent milestone payments receivable	800,000
Collaboration and License Agreement \| Regeneron Pharmaceuticals, Inc \| Maximum \| Additional Contingent Payments
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Contingent milestone payments receivable	$ 1,200,000

Collaboration and License Ag_10

Collaboration and License Agreements - Summary of Contract Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Revenue from Contract with Customer [Abstract]
Beginning Balance	$ 212,315	$ 301,326
Additions	2,266	869
Revenue recognized	(31,210)	(18,278)
Ending Balance	$ 183,371	$ 283,917

Collaboration and License Ag_11

Collaboration and License Agreements - Contract Liabilities - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023	Dec. 31, 2022
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue	$ 183,371	$ 212,315	$ 283,917	$ 301,326
Amgen Inc \| EGFR Products
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue	$ 11,500
Deferred Revenue Recognition Maturity Year	2026
Astellas Pharma Inc.
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue	$ 27,600
Deferred Revenue Recognition Maturity Year	2026
Bristol Myers Squibb
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue	$ 100,300
Deferred Revenue Recognition Maturity Year	2025
ModernaTX, Inc
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue	$ 21,500
Deferred Revenue Recognition Maturity Year	2027
Regeneron Pharmaceuticals, Inc
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue	$ 22,500
Deferred Revenue Recognition Maturity Year	2026

License Agreement - Additional

License Agreement - Additional Information (Details) - USD ($) $ in Millions	1 Months Ended		3 Months Ended
	Apr. 30, 2024	Apr. 30, 2019	Mar. 31, 2024	Mar. 31, 2023	Aug. 31, 2010
License Agreement [Line Items]
Annual minimum royalty obligations					$ 0.2
Astellas Pharma Inc. \| Collaboration and License Agreement
License Agreement [Line Items]
Sublicense fees			$ 0.6
Immuno Gen Inc \| Subsequent Event
License Agreement [Line Items]
Milestone payable	$ 5
UCSB
License Agreement [Line Items]
Payment of upfront fees		$ 1
Annual license maintenance fees		$ 0.8
License payment term		2031
Sublicense fees			$ 1.6	$ 1.1

Stock-Based Compensation - Sche

Stock-Based Compensation - Schedule of Activities Under Company's Stock Option Plans (Details)	3 Months Ended
	Mar. 31, 2024 $ / shares shares
Number of Options
Balance,beginning of the period \| shares	12,949,612
Options granted \| shares	1,780,000
Options exercised \| shares	(119,874)
Option forfeited/expired \| shares	(303,341)
Balance, end of the period \| shares	14,306,397
Options Outstanding, Weighted-Average Exercise Price Per Share
Balances, beginning of the period \| $ / shares	$ 7.16
Options granted \| $ / shares	1.68
Options exercised \| $ / shares	1.57
Option forfeited/expired \| $ / shares	11.03
Balances, end of the period \| $ / shares	$ 6.44

Stock-Based Compensation - Sc_2

Stock-Based Compensation - Schedule of Company's TRSU Activities (Details) - Time based RSUs	3 Months Ended
	Mar. 31, 2024 $ / shares shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Balance at December 31, 2023 \| shares	1,400,529
Units awarded \| shares	1,117,333
Units vested \| shares	(706,923)
units cancelled \| shares	(28,139)
Balance at March 31, 2024 \| shares	1,782,800
Balance at December 31, 2023 \| $ / shares	$ 2.4
Units Awarded \| $ / shares	1.62
Units vested \| $ / shares	2.14
Units cancelled \| $ / shares	1.76
Balance at March 31, 2024 \| $ / shares	$ 2.02

Stock-Based Compensation - Sc_3

Stock-Based Compensation - Schedule of Activities for Company's PSUs (Details) - Performance based RSUs - $ / shares	1 Months Ended		3 Months Ended
	Feb. 28, 2023	Aug. 31, 2022	Mar. 31, 2024
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Balance at December 31, 2023			875,000
Units awarded	760,000	250,000	810,000
Balance at March 31, 2024			1,685,000
Balance at December 31, 2023			$ 2.41
Units Awarded			1.66
Balance at March 31, 2024			$ 2.05

Stock-Based Compensation - Tota

Stock-Based Compensation - Total Stock-based Compensation Recognized (Details) - Stock Compensation Plan - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 1,907	$ 2,409
Research and development
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	707	961
General and administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 1,200	$ 1,448

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) - USD ($) $ in Thousands	1 Months Ended			3 Months Ended		12 Months Ended
	Jan. 31, 2024	Feb. 28, 2023	Aug. 31, 2022	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023	Dec. 31, 2022
Time based RSUs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense				$ 400	$ 400
Granted				1,117,333
Performance based RSUs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense							$ 55,000
Granted		760,000	250,000	810,000
PSU's Awarded, Grant date fair value		$ 1,900	$ 400
2024 Performance based RSU
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Granted	810,000
PSU's Awarded, Grant date fair value		$ 1,300
Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense				$ 1,400	$ 1,900
Share Based Compensation Award Tranche Two \| Performance based RSUs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting rights, description		Vesting for 50% of the PSUs granted will occur upon attaining certain specific milestones by December 2024 (“2023-Tranche 1”), and the remaining 50% will vest upon attaining certain specific milestones by December 2025 (“2023-Tranche 2”).	Vesting for 50% of the PSUs granted was set to occur upon attaining certain specific milestones by December 2023 (“2022-Tranche 1”), and the remaining 50% are set to vest upon attaining certain specific milestones by December 2024 (“2022-Tranche 2”).
Share Based Compensation Award Tranche Two \| 2024 Performance based RSU
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting rights, description		Vesting for 50% of the PSUs granted will occur upon attaining certain specific milestones by December 2025 (“2024-Tranche 1”), and the remaining 50% will vest upon attaining certain specific milestones by December 2026 (“2024-Tranche 2”).
Tranche One \| Performance based RSUs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense						$ 128,000
Tranche Two \| Performance based RSUs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense				$ 19,000		$ 106,000

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) - Patent Infringement Lawsuit - USD ($)		3 Months Ended
	Mar. 04, 2020	Mar. 31, 2024
Loss Contingencies [Line Items]
Lawsuit filed date	March 4, 2020
Name of plaintiff		Vytacera Bio, LLC
Loss contingency claim amount		$ 0

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2023	Mar. 31, 2024
Income Tax Disclosure [Abstract]
Unrecognized tax benefits,income tax penalties and interest expense		$ 3.9
Unrecognized tax benefits would affect company's effective tax rate			$ 3.9
Deferred tax asset, net change in total valuation allowance increase during period	$ 5.1

Subsequent Event - Additional I

Subsequent Event - Additional Information (Details) - USD ($)		1 Months Ended
	May 01, 2024	Apr. 30, 2024	Jul. 31, 2023	Feb. 29, 2020
Jefferies LLC
Subsequent Event [Line Items]
Common stock, par value				$ 0.00001
Percentage of sales commission				3%
Jefferies LLC \| Subsequent Event
Subsequent Event [Line Items]
Issuance of common stock in follow-on offering, net of issuance costs, shares		2,270,608
Average price		$ 2.2
Proceeds from issuance of common stock, net of issuance costs		$ 4,800,000
Percentage of sales commission and issuance cost		3%
Jefferies LLC \| Maximum
Subsequent Event [Line Items]
Proceeds from issuance of common stock, net of issuance costs				$ 75,000,000
BVF Partners \| Private Placement
Subsequent Event [Line Items]
Gross proceeds from issuance of private placement			$ 29,700,000
Issuance cost			$ 300,000
Price per share			$ 2.08
BVF Partners \| Private Placement \| Pre Funded Warrant
Subsequent Event [Line Items]
Number of shares issued upon warrants			14,423,077
BVF Partners \| Private Placement \| Tranche one Warrant
Subsequent Event [Line Items]
Number of shares issued upon warrants			5,769,231
BVF Partners \| Private Placement \| Tranche Two Warrant
Subsequent Event [Line Items]
Number of shares issued upon warrants			5,769,231
BVF Partners \| Subsequent Event
Subsequent Event [Line Items]
Stock exercised	7,500,000
Exercise price of warrants	$ 0.00001