FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

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, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person * GLUCK FREDERICK W   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 _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) 743 SAN YSIDRO ROAD 3. Date of Earliest Transaction (Month/Day/Year) 08/09/2016 (Street) SANTA BARBARA, CA 91308 4. If Amendment, Date Original Filed(Month/Day/Year) 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 08/09/2016   M   31,767 A $ 1.1339 179,558 D   Common Stock 08/09/2016   M   16,612 A $ 0.945 196,170 D   Common Stock 08/09/2016   M   27,606 A $ 1.4489 223,776 D   Common Stock 08/09/2016   M   17,139 A $ 1.5749 240,915 D   Common Stock               331,643 I By Frederick W. Gluck 1997 Family Trust dtd July 28, 1997 (1) Common Stock               22,111 I By Richlin Partners, LLC (2) Common Stock               3,200 I By spouse

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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)

$ 1.1339

08/09/2016

M

31,767

(3)

03/23/2021

Common Stock

31,767

$ 0

0

D

Stock Option (right to buy)

$ 0.945

08/09/2016

M

16,612

(3)

02/25/2023

Common Stock

16,612

$ 0

0

D

Stock Option (right to buy)

$ 1.4489

08/09/2016

M

27,606

(3)

05/23/2024

Common Stock

27,606

$ 0

0

D

Stock Option (right to buy)

$ 1.5749

08/09/2016

M

17,139

(3)

02/08/2025

Common Stock

17,139

$ 0

0

D

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
GLUCK FREDERICK W 743 SAN YSIDRO ROAD SANTA BARBARA, CA 91308	X

Signatures

/s/ Cynthia J. Ladd, as Attorney-in-Fact for Frederick W. Gluck		08/11/2016
**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)	The Reporting Person is a trustee of Frederick W. Gluck 1997 Family Trust dtd July 28, 1997.
(2)	Richlin Partners, LLC is an entity owned of record by the spouse of the Reporting Person.
(3)	100% of the shares subject to the option are fully vested and exercisable.

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