Amendment to Statement of Changes in Beneficial Ownership (Form 4/A)

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b). Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940

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(Print or Type Responses)

1. Name and Address of Reporting Person * McCarthy Sean A. 2. Issuer Name and Ticker or Trading Symbol CytomX Therapeutics, Inc. [CTMX] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) __X__ Director _____ 10% Owner __X__ Officer (give title below) _____ Other (specify below) CEO (Last) (First) (Middle) C/O CYTOMX THERAPEUTICS, INC., 5959 HORTON STREET, SUITE 300 3. Date of Earliest Transaction (Month/Day/Year) 11/06/2025 (Street) EMERYVILLE, CA 94608 4. If Amendment, Date Original Filed (Month/Day/Year) 11/10/2025 6. Individual or Joint/Group Filing (Check Applicable Line) _X_ Form filed by One Reporting Person ___ Form filed by More than One Reporting Person (City) (State) (Zip) Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned

1.Title of Security (Instr. 3) 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 11/06/2025 M(1) 101,793 A $1.59 1,191,477(4) D Common Stock 11/06/2025 S(2) 101,793 D $4.5377(3) 1,089,684(1)(4) D Common Stock 93,158 I See footnote(5)

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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)

1. Title of Derivative Security (Instr. 3)

2. Conversion or Exercise Price of Derivative Security

3. Transaction Date (Month/Day/Year)

3A. Deemed Execution Date, if any (Month/Day/Year)

4. Transaction Code (Instr. 8)

5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5)

6. Date Exercisable and Expiration Date (Month/Day/Year)

7. Title and Amount of Underlying Securities (Instr. 3 and 4)

8. Price of Derivative Security (Instr. 5)

9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)

10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4)

11. Nature of Indirect Beneficial Ownership (Instr. 4)

Code

V

(A)

(D)

Date Exercisable

Expiration Date

Title

Amount or Number of Shares

Stock Option (Right to Buy)

$1.59

11/06/2025

M(1)

101,793

(6)

08/09/2032

Common Stock

101,793

$ 0

348,207

D

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
McCarthy Sean A. C/O CYTOMX THERAPEUTICS, INC. 5959 HORTON STREET, SUITE 300 EMERYVILLE, CA 94608	X		CEO

Signatures

/s/ Christopher Ogden, as Attorney-in-Fact for Sean A. McCarthy		10/16/2026
**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 4(b)(v).
**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1)	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.
(2)	The transactions reported herein were effected pursuant to the Reporting Person's Rule 10b5-1 trading plan, adopted on August 27, 2024.
(3)	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.
(4)	Includes 488,750 restricted stock units.
(5)	Shares held by Sean A. McCarthy 2018 Trust, of which the Reporting Person is trustee.
(6)	This option is fully vested and exercisable.

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