Subsequent Event	12 Months Ended
Dec. 31, 2025
Subsequent Events [Abstract]
Subsequent Event	18. Subsequent Event In March 2026, Astellas chose to not advance the remaining preclinical programs under the alliance, resulting in a termination of the collaboration effective in the second quarter of 2026. CytomX is currently assessing options to advance select targets previously covered under the Astellas collaboration as part of its ongoing research and development strategy.

The entire disclosure for significant events or transactions that occurred after the balance sheet date through the date the financial statements were issued or the date the financial statements were available to be issued. Examples include: the sale of a capital stock issue, purchase of a business, settlement of litigation, catastrophic loss, significant foreign exchange rate changes, loans to insiders or affiliates, and transactions not in the ordinary course of business.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 855
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org/855/tableOfContent

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 855
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483399/855-10-50-2

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