SecProbe.io

August 18, 2015

Via E -mail
Sean A. McCarthy, D.Phil.
President and Chief Executive Officer
CytomX Therapeutics, Inc.
343 Oyster Point Blvd., Suite 100
South San Francisco, CA 94080

Re: CytomX Therapeutics, Inc.
Draft Registration Statement on Form S -1
Submitted July 24, 2015
  CIK No. 1501989

Dear Mr.  McCarthy :

We have reviewed your draft registration statement  and have the following comments.  In
some of our comments, we may ask you to provide us with information so we may better
understand your disclosure.

Please respond to this letter by providing the requested information and either submitting
an amended draft registration statement or publicl y filing your registration statement on
EDGAR.  If you do not believe our comments apply to your facts and circumstances or do not
believe an amendment is appropriate, please tell us why in your response.

After reviewing the information you provide in r esponse to these  comments  and your
amended draft registration statement or filed registration statement,  we may have  additional
comments.
General
1. Please supplementally provide us with copies of all written communications, as defined
in Rule 405 under the  Securities Act, that you, or anyone authorized to do so on your
behalf, present to potential investors in reliance on Section 5(d) of the Securities Act,
whether or not they retain copies of the communications.
Special Note Regarding Forward -Looking Sta tements, page 48
2. We note your statement that the prospectus includes forward -looking statements under
the Securities Act of 1933 and the Securities Exchange Act of 1934.  Be advised that
Section 27A(b)(1)(C) of the Securities Act and Section 21E(b)(1)(C) o f the Securities
Exchange Act expressly state that the safe harbor for forward looking statements does not

Sean A. McCarthy, D.Phil.
CytomX Therapeutics, Inc.
August 18, 2015
Page 2

 apply to statements made by companies that are not reporting companies under section
13(a) or 15(d) of the Securities Exchange Act.  Please explain s upplementally or either:
 delete any references to the Private Securities Litigation Reform
Act; or
 make clear, each time you refer to the Litigation Reform Act, that the safe harbor
does not apply to your company
Use of Proceeds, page 51
3. We note the broad discretion to change the use of proceeds  in the futur e as discussed in
this section and the risk factor on page 44.  Please revise to cl early address  the relate d
contingencies and alternatives .  See Instruction 7 to Item 504 of Regulation S -K.
4. We note the disclosure that you may use a portion of the proceeds to make payments of
interest and principal on your outstanding loan with ATEL Ventures.  Please disclose the
amount that may be allocated to these payments.
Preclinical Proof of Concept,  page 86
5. Please tell us the basis for the graphs provided in this section comparing your probody
therapeutic with other available therapeutics .  It is unclear, for example, whether you
used internal or external data to generate the charts and if external please disclose in the
prospectus the source of such data.
In-Licenses, page 101
6. Please disclose the annual royalties that have been paid to date and the extension fees
paid pursuant to the UC agreement.
7. Please disclose the total number of employees.  See I tem 101(c)(xiii) of Regulation S -K.
Management, page 118
8. Please discuss the specific experience, qualifications, attributes or skills that led to the
conclusion that each of the directors individually should serve as a director, as required
by Item 401(e)( 1) of Regulation S -K.
9. Please disclose Dr. Huh’s business experience for the past 5 years.  Please also disclose
the period during which Mr. Goeltz was employed at Amgen.
Executive Compensation , page 127
10. Please discuss in greater detail the compensation arrangements for the directors in 2014.
We note that Dr. Huh and Mr. Gluck received more cash compensation than discussed in

Sean A. McCarthy, D.Phil.
CytomX Therapeutics, Inc.
August 18, 2015
Page 3

 this section.  In addition, once known, please revise to provide more detail reg arding the
directors’ compensation following the completion of this offering.
11. We note the elements of executive compensation outlined on page 128.  Please provide
an expanded analysis of how you determined the amount of each element to pay as
required by I tem 402(o) of Regulation S -K.  Your disclosure should address the specific
items of corporate performance that are taken into account in setting compensation
policies and making compensation decisions, such as the formula or criteria used in
determining th e non -equity incentive award, and the target research and finance and
financial goals set for the annual cash bonuses.
12. We note the reference to employment and severance and change in control agreements in
this section.  Please file these agreements as ex hibits.
Policies and Procedures for Related Party Transactions, page 133
13. Please disclose the amounts received from Pfizer pursuant to the collaboration agreement
for the periods required by Item 404(a) of Regulation S -K.
14. Please disclose the standards to be  applied pursuant to your policies and procedures as
required by Item 404(b)(1)(ii) of Regulation S -K.
Principal Stockholders, page 134
15. We note your disclosure in this section is provided as of June 30, 2015.  Please provide
this disclosure as of the most recent practicable date.
16. Please disclose the control person(s) for Cytomx Therapeutics Holdings LLC.  Also, if
Mr. Gluck is a control person then he would be deemed to beneficially own all of the
shares held by Cytomx  Therapeutics Holdings LLC, not just a portion.  Please revise or
advise.
Underwriting, page 149
17. On page 1 52 you indicate that “some  of the underwriters and their affiliates have engaged
in, and may in the future  engage in, investment banking and other commercial dealings”
with you or your affiliates.  Please revise to more fully describe these relationships , as
required by Item 508(a) of Regulation S -K.
Undertakings, page II -5
18. Please include the undertakings requ ired by Item s 512(a)(5)(ii) and (a)(6) of Regulation
S-K.

Sean A. McCarthy, D.Phil.
CytomX Therapeutics, Inc.
August 18, 2015
Page 4

 Please contact Ruairi Regan at (202) 551 -3269 or  Pamela Howell, Special Counsel, at
(202) 551 -3357 with any questions.

Sincerely,

 /s/ Pamela Howell
 for

 John Reynolds
Assistant Director
Office of Beverages,
Appa rel and Mining

cc:   Sam Zucker, Esq.
       Sidley Austin LLP