X0609 4/A 2025-11-06 2025-11-10 0001501989 CytomX Therapeutics, Inc. CTMX 0001654058 McCarthy Sean A. false C/O CYTOMX THERAPEUTICS, INC. 5959 HORTON STREET, SUITE 300 EMERYVILLE CA 94608 true true false false CEO true Common Stock 2025-11-06 4 M false 101793 1.59 A 1191477 D Common Stock 2025-11-06 4 S false 101793 4.5377 D 1089684 D Common Stock 93158 I See footnote Stock Option (Right to Buy) 1.59 2025-11-06 4 M false 101793 0 D 2032-08-09 Common Stock 101793 348207 D This Form 4/A restates in its entirety the original Form 4 filed on 11/10/2025 (the "Original Form 4") to report an inadvertently omitted exercise that was part of a same-day exercise-and-sale transaction; the sale was timely reported in the Original Form 4. Due to the omission, the Original Form 4 understated the Reporting Person's direct holdings following the reported transactions by 101,793 shares, and this understatement carried forward into Column 5 of Table I of the Reporting Person's Forms 4 filed on 2/4/2026 and 3/19/2026 (the "Subsequent Reports"). The direct holdings reported in Column 5 of Table I of this Form 4/A have been corrected. The Subsequent Reports are not being amended; the direct holdings amounts reported therein should each be read as increased by 101,793 shares. The transactions reported herein were effected pursuant to the Reporting Person's Rule 10b5-1 trading plan, adopted on August 27, 2024. This transaction was executed in multiple trades at prices ranging from $4.50 to $4.62, inclusive. The price reported above reflects the weighted average sale price. The Reporting Person undertakes to provide upon request by the staff of the Securities and Exchange Commission, the Issuer, or a security holder of the Issuer, full information regarding the number of shares sold at each separate sale price. Includes 488,750 restricted stock units. Shares held by Sean A. McCarthy 2018 Trust, of which the Reporting Person is trustee. This option is fully vested and exercisable. /s/ Christopher Ogden, as Attorney-in-Fact for Sean A. McCarthy 2026-10-16