Ownership Submission
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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(Print or Type Responses)
1. Name and Address of Reporting Person *
Canaan IX L.P.
   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 __X__ 10% Owner
_____ Officer (give title below) _____ Other (specify below)
(Last)
(First)
(Middle)
285 RIVERSIDE AVENUE, SUITE 250		 3. Date of Earliest Transaction (Month/Day/Year)
11/10/2016
(Street)

WESTPORT, CT 06880		 4. If Amendment, Date Original Filed(Month/Day/Year)
 6. Individual or Joint/Group Filing(Check Applicable Line)
___ Form filed by One Reporting Person
_X_ 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 11/10/2016   S   27,135 D $ 11.0702 (1) 3,903,516 I See Footnote (2)
Common Stock 11/11/2016   S   35,391 D $ 11.2023 (3) 3,868,125 I See Footnote (2)
Common Stock 11/14/2016   S   23,744 D $ 11.2052 (4) 3,844,381 I See Footnote (2)

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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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

Reporting Owners

Reporting Owner Name / Address Relationships
 Director  10% Owner  Officer  Other
Canaan IX L.P.
285 RIVERSIDE AVENUE, SUITE 250
WESTPORT, CT 06880		   X   X    
Canaan Partners IX LLC
285 RIVERSIDE AVENUE, SUITE 250
WESTPORT, CT 06880		   X   X    

Signatures

 Canaan IX L.P., By: Canaan Partners IX LLC, its general partner, By: /s/ Nancy Levenson, Attorney-in-Fact   11/14/2016
**Signature of Reporting Person Date
 Canaan Partners IX LLC, By: /s/ Nancy Levenson, Attorney-in-Fact   11/14/2016
**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 price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $11.00 - $11.24, inclusive. The reporting persons undertake to provide to the issuer, any security holder of the issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in footnote (1) of this Form 4.
(2) The shares are held directly by Canaan IX L.P. (the "Canaan Fund"). Canaan Partners IX LLC ("Canaan IX" and together with the Canaan Fund, the "Canaan Entities") is the sole general partner of the Canaan Fund, and each may be deemed to have sole voting, investment and dispositive power with respect to the shares held by the Canaan Fund. Timothy Shannon, a non-managing member of Canaan IX, serves as representative of the Canaan Entities on the issuer's board of directors. Canaan IX disclaims Section 16 beneficial ownership of the securities held by the Canaan Fund, except to the extent of its pecuniary interest therein, if any.
(3) The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $11.00 - $11.44, inclusive. The reporting persons undertake to provide to the issuer, any security holder of the issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in footnote (3) of this Form 4.
(4) The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $11.00 - $11.37, inclusive. The reporting persons undertake to provide to the issuer, any security holder of the issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in footnote (4) of this Form 4.
 
Remarks:
Exhibit 24 - Power of Attorney (incorporated by reference to the Power of Attorney filed as Exhibit 24 to the Form 4 filed by the Reporting Persons on October 12, 2016)

Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.

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