Document:

EX-10.6

 Exhibit 10.6 

CYTOMX THERAPEUTICS, INC. 

EMPLOYEE STOCK PURCHASE PLAN 

1. Purpose. The purpose of this Plan is to provide Employees of the Company and Participating Subsidiaries with an opportunity
to purchase common stock of the Company through accumulated payroll deductions. It is the intention of the Company to have the Plan qualify as an “Employee Stock Purchase Plan” under Section 423 of the Code. The provisions of the
Plan, accordingly, shall be construed so as to extend and limit participation in a manner consistent with the requirements of that Section of the Code. 

2. Definitions. As used herein, the terms set forth below have the meanings assigned to them in this Section 2 and shall
include the plural as well as the singular. 
 “1933 Act” means the Securities Act of 1933, as amended. 

“1934 Act” means the Securities Exchange Act of 1934, as amended. 

“Board” means the Board of Directors of the Company. 

“Business Day” shall mean a day on which NASDAQ is open for trading. 

“Brokerage Account” means the account in which the Purchased Shares are held. 

“Code” means the Internal Revenue Code of 1986, as amended. 

“Committee” means the Compensation Committee of the Board, or the designee of the Compensation Committee. 

“Company” means CytomX Therapeutics, Inc., a Delaware corporation, or any successor thereto. 

“Compensation” means solely the base pay received by a Participant. Compensation does not include:
(1) commissions; (2) cash bonuses; (3) income related to stock option awards, stock grants and other equity incentive awards; (4) expense reimbursements; (5) relocation-related payments; (6) benefit plan payments
(including but not limited to short-term disability pay, long-term disability pay, maternity pay, military pay, tuition reimbursement and adoption assistance); (7) deceased pay; (8) income from non-cash and fringe benefits;
(9) severance payments; (10) overtime; or (11) other forms of compensation not specifically listed herein. 

“Employee” means any individual who is a common law employee of the Company or any other Participating Subsidiary. For
purposes of the Plan, the employment relationship shall be treated as continuing intact while the individual is on sick leave or other leave of absence approved by the Company or the Participating Subsidiary, as appropriate, and only to the extent
permitted under Section 423 of the Code. For purposes of the Plan, an individual who performs services for the Company or a Participating Subsidiary pursuant to an agreement (written or oral) that classifies such individual’s relationship
with the Company or a Participating Subsidiary as other than a common law employee shall not be considered an “employee” with respect to any period preceding the date on which a court or administrative agency issues a final determination
that such individual is an “employee.” 

 “Enrollment Date” means the first Business Day of each Offering Period.

 “Exercise Date” means the last Business Day of each Offering Period. 

“Fair Market Value” on or as of any date means the “NASDAQ Official Closing Price” (as defined on
www.nasdaq.com) (or such substantially similar successor price thereto) for a Share as reported on www.nasdaq.com (or a substantially similar successor website) on the relevant valuation date or, if no NASDAQ Official Closing Price is reported on
such date, on the preceding day on which a NASDAQ Official Closing Price was reported; or, if the Shares are no longer listed on NASDAQ, the closing price for Shares as reported on the official website for such other exchange on which the Shares are
listed. 
 “NASDAQ” means the Nasdaq Global Market. 

“Offering Period” means every six-month period beginning each January 1st, and July 1st or such other period
designated by the Committee; provided that in no event shall an Offering Period exceed twenty-seven (27) months. The first Offering Period under the Plan shall commence on July 1, 2016. 

“Option” means an option granted under this Plan that entitles a Participant to purchase Shares. 

“Participant” means an Employee who satisfies the requirements of Sections 3 and 5 of the Plan. 

“Participating Subsidiary” means each Subsidiary other than those that the Committee or the Board has excluded from
participation in the Plan. 
 “Plan” means this CytomX Therapeutics, Inc. Employee Stock Purchase Plan. 

“Purchase Account” means the account used to purchase Shares through the exercise of Options under the Plan. 

“Purchase Price” shall be eighty-five percent (85%) of the lesser of (i) the Fair Market Value of a Share on
the applicable Enrollment Date, or (ii) the Fair Market Value of a Share on the Exercise Date for such Offering Period; provided, however, that the Committee may determine a different per share Purchase Price provided that such per share
Purchase Price is communicated to Participants prior to the beginning of the Offering Period and provided that in no event shall such per share Purchase Price be less than the lesser of 85% of (i) the Fair Market Value of a Share on the
applicable Enrollment Date or (ii) the Fair Market Value of a Share on the Exercise Date. 
 “Purchased Shares”
means the full Shares issued or delivered pursuant to the exercise of Options under the Plan. 

  
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 “Shares” means the common stock, par value $0.00001 per share, of the
Company. 
 “Subsidiary” means an entity, domestic or foreign, of which not less than 50% of the voting equity is
held by the Company or a Subsidiary, whether or not such entity now exists or is hereafter organized or acquired by the Company or a Subsidiary; provided such entity is also a “subsidiary” within the meaning of Section 424 of the
Code. 
 “Termination Date” means the date on which a Participant terminates employment or on which the Participant
ceases to provide services to the Company or a Subsidiary as an employee, and specifically does not include any period following that date which the Participant may be eligible for or in receipt of other payments from the Company including in lieu
of notice or termination or severance pay or as wrongful dismissal damages. 
 3. Eligibility. 

(a) Only Employees of the Company or a Participating Subsidiary shall be eligible to be granted Options under the Plan and, in no event may a
Participant be granted an Option under the Plan following his or her Termination Date. 
 (b) Any provisions of the Plan to the contrary
notwithstanding, no Employee shall be granted an Option under the Plan if (i) immediately after the grant, such Employee (or any other person whose stock would be attributed to such Employee pursuant to Section 424(d) of the Code) would
own capital stock of the Company and/or hold outstanding Options or options to purchase stock possessing five percent (5%) or more of the total combined voting power or value of all classes of stock of the Company or of any of its Subsidiaries,
or (ii) such Option would permit his or her rights to purchase stock under all employee stock purchase plans (described in Section 423 of the Code) of the Company and its Subsidiaries to accrue at a rate that exceeds twenty-five thousand
dollars ($25,000) of the Fair Market Value of such stock (determined at the time each such Option is granted) for each calendar year in which such Option is outstanding at any time. No Participant may purchase more than 6,000 Shares during any
Offering Period. 
 4. Exercise of an Option. Options shall be exercised on behalf of Participants in the Plan every Exercise
Date, using payroll deductions that have accumulated in the Participants’ Purchase Accounts during the immediately preceding Offering Period or that have been retained from a prior Offering Period pursuant to Section 8 hereof. 

5. Participation. 

(a) An Employee shall be eligible to participate on the first Enrollment Date that occurs at least 90 days after such Employee’s first
date of employment with the Company or a Participating Subsidiary; provided, that such Employee properly completes and submits an election form by the deadline prescribed by the Company. 

(b) An Employee who does not become a Participant on the first Enrollment Date on which he or she is eligible may thereafter become a
Participant on any subsequent Enrollment Date by properly completing and submitting an election form by the deadline prescribed by the Company. 

  
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 (c) Payroll deductions for a Participant shall commence on the first payroll date following the
Enrollment Date and shall end on the last payroll date in the Offering Period to which such authorization is applicable, unless sooner terminated by the Participant as provided in Section 12 hereof. 

6. Payroll Deductions. 

(a) A Participant shall elect to have payroll deductions made during an Offering Period equal to no less than 1% of the Participant’s
Compensation up to a maximum of 15% (or such greater amount as the Committee establishes from time to time). The amount of such payroll deductions shall be in whole percentages (for example, 3%, 12%, 15%). All payroll deductions made by a
Participant shall be credited to his or her Purchase Account. A Participant may not make any additional payments into his or her Purchase Account. 

(b) A Participant may not increase or decrease the rate of payroll deductions during an Offering Period. A Participant may change his or her
payroll deduction percentage under subsection (a) above for any subsequent Offering Period by properly completing and submitting an election change form in accordance with the procedures prescribed by the Committee. The change in amount shall
be effective as of the first Enrollment Date following the date of filing of the election change form. 
 (c) Notwithstanding the foregoing,
to the extent necessary to comply with Section 423(b)(8) of the Code and Section 3(b) hereof, a Participant’s payroll deductions may be decreased to zero percent (0%) at any time during an Offering Period. Payroll deductions shall
recommence at the rate provided in such Participant’s election form at the beginning of the first Offering Period which is scheduled to end in the following calendar year, unless terminated by the Participant as provided in Section 12
hereof. 
 7. Grant of Option. On the applicable Enrollment Date, each Participant in an Offering Period shall be granted an
Option to purchase on the next following Exercise Date a number of full Shares determined by dividing such Participant’s payroll deductions accumulated prior to such Exercise Date and retained in the Participant’s Purchase Account as of
the Exercise Date by the applicable Purchase Price. 
 8. Exercise of Option. A Participant’s Option for the purchase of
Shares shall be exercised automatically on the Exercise Date, and the maximum number of Shares subject to the Option shall be purchased for such Participant at the applicable Purchase Price with the accumulated payroll deductions in his or her
Purchase Account. No fractional Shares shall be purchased; any payroll deductions accumulated in a Participant’s Purchase Account which are not sufficient to purchase a full Share shall be retained in the Purchase Account for the next
subsequent Offering Period, subject to earlier withdrawal by the Participant as provided in Section 12 hereof. All other payroll deductions accumulated in a Participant’s Purchase Account and not used to purchase Shares on an Exercise Date
shall be distributed to the Participant. During a Participant’s lifetime, a Participant’s Option is exercisable only by him or her. The Company shall satisfy the exercise of all Participants’ Options for the purchase of Shares through
(a) the issuance of authorized but unissued Shares, (b) the transfer of treasury Shares, (c) the purchase of Shares on behalf of the applicable Participants on the open market through an independent broker and/or (d) a
combination of the foregoing. 

  
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 9. Issuance of Stock. The Shares purchased by each Participant shall be issued in
book entry form and shall be considered to be issued and outstanding to such Participant’s credit as of the end of the last day of each Offering Period. The Committee may permit or require that shares be deposited directly in a Brokerage
Account with one or more brokers designated by the Committee or to one or more designated agents of the Company, and the Committee may use electronic or automated methods of share transfer. The Committee may require that Shares be retained with such
brokers or agents for a designated period of time and/or may establish other procedures to permit tracking of disqualifying dispositions of such Shares, and may also impose a transaction fee with respect to a sale of Shares issued to a
Participant’s credit and held by such a broker or agent. The Committee may permit Shares purchased under the Plan to participate in a dividend reinvestment plan or program maintained by the Company, and establish a default method for the
payment of dividends. 
 10. Approval by Stockholders. Notwithstanding the above, the Plan is expressly made subject to the
approval of the stockholders of the Company within 12 months before or after the date the Plan is adopted by the Board. Such stockholder approval shall be obtained in the manner and to the degree required under applicable federal and state law. If
the Plan is not so approved by the stockholders within 12 months before or after the date the Plan is adopted by the Board, this Plan shall not come into effect. 

11. Administration. 

(a) Powers and Duties of the Committee. The Plan shall be administered by the Committee. Subject to the provisions of the Plan,
Section 423 of the Code and the regulations thereunder, the Committee shall have the discretionary authority to determine the time and frequency of granting Options, the terms and conditions of the Options and the number of Shares subject to
each Option. The Committee shall also have the discretionary authority to do everything necessary and appropriate to administer the Plan, including, without limitation, interpreting the provisions of the Plan (but any such interpretation shall not
be inconsistent with the provisions of Section 423 of the Code). All actions, decisions and determinations of, and interpretations by the Committee with respect to the Plan shall be final and binding upon all Participants and upon their
executors, administrators, personal representatives, heirs and legatees. No member of the Board or the Committee shall be liable for any action, decision, determination or interpretation made in good faith with respect to the Plan or any Option
granted hereunder. The Plan shall be administered so as to ensure that all Participants have the same rights and privileges as are provided by Section 423(b)(5) of the Code. 

(b) Administrator. The Company, Board or the Committee may engage the services of a brokerage firm or financial institution (the
“Administrator”) to perform certain ministerial and procedural duties under the Plan including, but not limited to, mailing and receiving notices contemplated under the Plan, determining the number of Purchased Shares for each
Participant, maintaining or causing to be maintained the Purchase Account and the Brokerage Account, disbursing funds maintained in the Purchase Account or proceeds from the sale of Shares through the Brokerage Account, and filing with the
appropriate tax authorities proper tax returns and forms (including information returns) and providing to each Participant statements as required by law or regulation. 

  
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 (c) Indemnification. Each person who is or shall have been (a) a member of the Board,
(b) a member of the Committee, or (c) an officer or employee of the Company to whom authority was delegated in relation to this Plan, shall be indemnified and held harmless by the Company against and from any loss, cost, liability or
expense that may be imposed upon or reasonably incurred by him or her in connection with or resulting from any claim, action, suit or proceeding to which he or she may be a party or in which he or she may be involved by reason of any action taken or
failure to act under the Plan and against and from any and all amounts paid by him or her in settlement thereof, with the Company’s approval, or paid by him or her in satisfaction of any judgment in any such claim, action, suit or proceeding
against him or her; provided, however, that he or she shall give the Company an opportunity, at its own expense, to handle and defend the same before he or she undertakes to handle and defend it on his or her own behalf, unless such loss, cost,
liability or expense is a result of his or her own willful misconduct or except as expressly provided by statute. 
 The foregoing right of indemnification
shall not be exclusive of any other rights of indemnification to which such persons may be entitled under the Company’s certificate of incorporation or bylaws, any contract with the Company, as a matter of law, or otherwise, or of any power
that the Company may have to indemnify them or hold them harmless. 
 12. Withdrawal. A Participant may withdraw from the Plan
by properly completing and submitting to the Company a withdrawal form in accordance with the procedures prescribed by the Committee, which must be submitted prior to the date specified by the Committee before the last day of the applicable Offering
Period. Upon withdrawal, any payroll deductions credited to the Participant’s Purchase Account prior to the effective date of the Participant’s withdrawal from the Plan will be returned to the Participant. No further payroll deductions for
the purchase of Shares will be made during subsequent Offering Periods, unless the Participant properly completes and submits an election form, by the deadline prescribed by the Company. A Participant’s withdrawal from an offering will not have
any effect upon his or her eligibility to participate in the Plan or in any similar plan that may hereafter be adopted by the Company. 

13. Termination of Employment. On the Termination Date of a Participant for any reason prior to the applicable Exercise Date,
whether voluntary or involuntary, and including termination of employment due to retirement, death or as a result of liquidation, dissolution, sale, merger or a similar event affecting the Company or a Participating Subsidiary, the corresponding
payroll deductions credited to his or her Purchase Account will be returned to him or her or, in the case of the Participant’s death, to the person or persons entitled thereto under Section 16, and his or her Option will be automatically
terminated. 
 14. Interest. No interest shall accrue on the payroll deductions of a Participant in the Plan. 

15. Stock. 

  
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 (a) The stock subject to Options shall be common stock of the Company as traded on the NASDAQ or
on such other exchange as the Shares may be listed. 
 (b) Subject to adjustment upon changes in capitalization of the Company as provided
in Section 18 hereof, the maximum aggregate number of Shares which shall be made available under the Plan shall be 354,466 Shares, plus an annual increase to be added on the first day of each calendar year beginning with 2016, equal to the
lesser of (i) 675,000 Shares, (ii) one percent (1%) of the then-outstanding Shares on such date, or (iii) an amount determined by the Committee. If, on a given Exercise Date, the number of Shares with respect to which Options are
to be exercised exceeds the number of Shares then available under the Plan, the Committee shall make a pro rata allocation of the Shares remaining available for purchase in as uniform a manner as shall be practicable and as it shall determine to be
equitable. 
 (c) A Participant shall have no interest or voting right in Shares covered by his or her Option until such Option has been
exercised and the Participant has become a holder of record of Shares acquired pursuant to such exercise. 
 16. Designation of
Beneficiary. The Committee may permit Participants to designate beneficiaries to receive any Purchased Shares or payroll deductions, if any, in the Participant’s accounts under the Plan in the event of such Participant’s death.
Beneficiary designations shall be made in accordance with procedures prescribed by the Committee. If no properly designated beneficiary survives the Participant, the Purchased Shares and payroll deductions, if any, will be distributed to the
Participant’s estate. 
 17. Assignability of Options. Neither payroll deductions credited to a Participant’s
Purchase Account nor any rights with regard to the exercise of an Option or to receive Shares under the Plan may be assigned, transferred, pledged or otherwise disposed of in any way (other than by will, the laws of descent and distribution or as
provided in Section 16 hereof) by the Participant. Any such attempt at assignment, transfer, pledge or other disposition shall be without effect, except that the Company may treat such act as an election to withdraw from an Offering Period in
accordance with Section 12 hereof. 
 18. Adjustment of Number of Shares Subject to Options. 

(a) Adjustment. Subject to any required action by the stockholders of the Company, the maximum number of securities available for
purchase under the Plan, as well as the price per security and the number of securities covered by each Option under the Plan which has not yet been exercised shall be appropriately adjusted in the event of any stock split, reverse stock split,
stock dividend, combination or reclassification of the common stock of the Company, or any other increase or decrease in the number of Shares effected without receipt of consideration by the Company; provided, however, that conversion of any
convertible securities of the Company shall not be deemed to have been “effected without receipt of consideration.” Such adjustment shall be made by the Board or the Committee, whose determination in that respect shall be final, binding
and conclusive. If any such adjustment would result in a fractional security being available under the Plan, such fractional security shall be disregarded. Except as expressly provided herein, no issuance by the Company of shares of stock of any
class, or securities convertible into shares of stock of any class, shall affect, and no adjustment by reason thereof 

  
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shall be made with respect to, the number or price of Shares subject to an Option. The Options granted pursuant to the Plan shall not be adjusted in a manner that causes the Options to fail to
qualify as options issued pursuant to an “employee stock purchase plan” within the meaning of Section 423 of the Code. 
 (b)
Dissolution or Liquidation. In the event of the proposed dissolution or liquidation of the Company, the Offering Period then in progress will terminate immediately prior to the consummation of such proposed action, unless otherwise provided
by the Board, and the Board may either provide for the purchase of Shares as of the date on which such Offering Period terminates or return to each Participant the payroll deductions credited to such Participant’s Purchase Account. 

(c) Merger or Asset Sale. In the event of a proposed sale of all or substantially all of the assets of the Company, or the merger of
the Company with or into another corporation, each outstanding Option shall be assumed or an equivalent option substituted by the successor corporation or a parent or subsidiary of the successor corporation, unless the Board determines, in the
exercise of its sole discretion, that in lieu of such assumption or substitution to either terminate all outstanding Options and return to each Participant the payroll deductions credited to such Participant’s Purchase Account or to provide for
the Offering Period in progress to end on a date prior to the consummation of such sale or merger. 
 19. Amendments or Termination of
the Plan. 
 (a) The Board or the Committee may at any time and for any reason amend, modify, suspend, discontinue or terminate the
Plan without notice; provided that no Participant’s existing rights in respect of existing Options are adversely affected thereby. To the extent necessary to comply with Section 423 of the Code (or any other applicable law, regulation or
stock exchange rule), the Company shall obtain stockholder approval in such a manner and to such a degree as required. 
 (b) Without
stockholder consent and without regard to whether any Participant rights may be considered to have been “adversely affected,” the Board or the Committee shall be entitled to change the Purchase Price, Offering Periods, limit or increase
the frequency and/or number of changes in the amount withheld during an Offering Period, establish the exchange ratio applicable to amounts withheld in a currency other than U.S. dollars, permit payroll withholding in an amount less than or greater
than the amount designated by a Participant in order to adjust for delays or mistakes in the Company’s processing of properly completed withholding elections, establish reasonable waiting and adjustment periods and/or accounting and crediting
procedures to ensure that amounts applied toward the purchase of Shares for each Participant properly correspond with amounts withheld from the Participant’s Compensation, and establish such other limitations or procedures as the Board or the
Committee determines in its sole discretion advisable which are consistent with the Plan; provided, however, that changes to (i) the Purchase Price, (ii) the Offering Period, (iii) the maximum percentage of Compensation that may be
deducted pursuant to Section 6(a) or (iv) the maximum number of Shares that may be purchased in an Offering Period, shall not be effective until communicated to Participants in a reasonable manner, with the determination of such reasonable
manner in the sole discretion of the Board or the Committee. 

  
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 20. No Other Obligations. The receipt of an Option pursuant to the Plan shall
impose no obligation upon the Participant to purchase any Shares covered by such Option. Nor shall the granting of an Option pursuant to the Plan constitute an agreement or an understanding, express or implied, on the part of the Company to employ
the Participant for any specified period. 
 21. Notices and Communication. Any notice or other form of communication which
the Company or a Participant may be required or permitted to give to the other shall be provided through such means as designated by the Committee, including but not limited to any paper or electronic method. 

22. Condition Upon Issuance of Shares. 

(a) Shares shall not be issued with respect to an Option unless the exercise of such Option and the issuance and delivery of such Shares
pursuant thereto shall comply with all applicable provisions of law, domestic or foreign, including, without limitation, the 1933 Act and the 1934 Act and the rules and regulations promulgated thereunder, and the requirements of any stock exchange
upon which the Shares may then be listed, and shall be further subject to the approval of counsel for the Company with respect to such compliance. 

(b) As a condition to the exercise of an Option, the Company may require the person exercising such Option to represent and warrant at the
time of any such exercise that the Shares are being purchased only for investment and without any present intention to sell or distribute such Shares if, in the opinion of counsel for the Company, such a representation is required by any of the
aforementioned applicable provisions of law. 
 23. General Compliance. The Plan will be administered and Options will be
exercised in compliance with the 1933 Act, the 1934 Act and all other applicable securities laws and Company policies, including without limitation, any insider trading policy of the Company. 

24. Term of the Plan. The Plan shall become effective upon the earlier to occur of its adoption by the Board or its approval by
the stockholders of the Company and shall continue in effect for a term of ten (10) years, unless earlier terminated pursuant to Section 19. 

25. Governing Law. The Plan and all Options granted hereunder shall be construed in accordance with and governed by the laws of
the State of Delaware without reference to choice of law principles and subject in all cases to the Code and the regulations thereunder. 

26. Non-U.S. Participants. To the extent permitted under Section 423 of the Code, without the amendment of the Plan, the
Company may provide for the participation in the Plan by Employees who are subject to the laws of foreign countries or jurisdictions on such terms and conditions different from those specified in the Plan as may in the judgment of the Company be
necessary or desirable to foster and promote achievement of the purposes of the Plan and, in furtherance of such purposes the Company may make such modifications, amendments, procedures, subplans and the like as may be necessary or advisable to
comply with provisions of laws of other countries or jurisdictions in which the Company or the Participating Subsidiaries operate or have employees. Each subplan shall constitute a separate “offering” under this Plan in accordance with
Treas. Reg. §1.423-2(a). 

  
 9EX-10.15

 Exhibit 10.15 
  

 
 SEPARATION AGREEMENT AND GENERAL RELEASE OF CLAIMS 

This Separation and Release Agreement (“Agreement”) is made this 30th day of
September, 2014 by and between Henry B. Lowman, Ph.D. (“Executive”) and CytomX Therapeutics, Inc. (“Company”). 

WHEREAS, Company and Executive will be separating their employment relationship, and Executive will transition from Chief Scientific Officer,
to Consultant Chief Scientific Officer, to a member of Company’s Scientific Advisory Board; 
 WHEREAS, Company has offered Executive
certain separation benefits in exchange for Executive’s commitments set forth in this agreement; 
 NOW THEREFORE, the parties agree as
follows: 
  

	 	1.	Your employment with CytomX Therapeutics, Inc. (“Company”) will terminate effective September 30, 2014 (“Termination Date”). You will be paid all accrued wages including any unused
and accrued vacation and benefits through the Termination Date in accordance with applicable law. Your health insurance benefits will terminate on September 30, 2014, unless extended pursuant to paragraph 3 below. You are not required to sign
this Separation Agreement and General Release of Claims (“Release Agreement”) to receive accrued wages and benefits. 

  

	 	2.	So long as you execute this Release Agreement and permit it to become effective, following the termination of your employment on September 30, 2014, Company agrees to engage you as the Consultant Chief Scientific
Officer (or such other consultant title as Company may deem appropriate in its sole discretion) from the business day after this Release Agreement becomes effective through December 31, 2014, and you hereby accept engagement by Company. During
this period, you will obtain direction from Company’s Chief Executive Officer or any other appointed employee of Company on projects as assigned, and be paid $25,008.33 per month to perform these services. In addition, your stock options with
Company and your restricted shares of common stock in Company (issued pursuant to your Restricted Stock Repurchase Agreement, signed on December 23, 2010), as outlined in Appendix A to this agreement, shall continue to vest as long as you serve
as the Consultant Chief Scientific Officer. Following the termination of your Scientific Advisory Board Consulting Agreement, you shall have 90 days to exercise your options. Your stock options shall otherwise continue to be governed by the terms of
the equity plans and award agreements under which they were granted. You agree to execute, and to comply with the terms and conditions of, the Consulting Agreement, which is attached as Exhibit A and incorporated by reference herein as if fully set
forth below. If you complete the full term of your engagement as the Consultant Chief Scientific Officer, from the day after this Release Agreement becomes effective through December 31, 2014, you shall be eligible to receive an annual cash
bonus, under the terms of your signed Offer of Employment, pro-rated to reflect the term of your employment during the year 2014, from January 1, 2014 through your Termination Date. In addition, Company agrees to appoint you to the Scientific

  

			
	  
 

	 	    OFFICE (650) 515-3185  |  FAX (650) 351-0353  | 
 343 Oyster Point Blvd., Suite 100  |  South San Francisco, CA 94080  |  www.cytomx.com

	 	
Advisory Board as of January 5, 2015, and you hereby accept that appointment. You agree to execute, and to comply with the terms and conditions of, the Scientific Advisory Board Consulting
Agreement, which is attached as Exhibit B and incorporated by reference herein as if fully set forth below. Company and you agree that section three of your December 23, 2010 Secured Promissory Note is hereby amended as follows

 “SECTION 3. PAYMENT OF PRINCIPAL AND INTEREST. Subject to prepayment under Section 5, below, and acceleration
under Section 6, below, the principal of and interest on this Note shall be due and payable in full on the earliest of (i) the Seventh Anniversary of the Issue Date, (ii) the sale or disposition of all or any portion of the Pledged
Shares, or (iii) the thirtieth day in which the Maker has not provided service to the Holder either as an employee or a consultant.” 

Your acceptance and non-revocation of this Release Agreement is a condition precedent to any of the Company’s obligations under this
paragraph. 
  

	 	3.	Company is offering you the opportunity to receive separation benefits to which you are not otherwise entitled by executing the general release of claims set forth in this Release Agreement. If you timely sign, date,
return this Release Agreement, and allow it to become effective, and so long as you are not in breach of your obligations under this Release Agreement, Company will provide you the following as the sole separation benefits (“Separation
Benefits”): If you make a timely election to continue health care coverage for you and, if applicable, your dependents, under the Consolidated Omnibus Budget Reconciliation Act (COBRA), you may submit for reimbursement to Company monthly
COBRA premiums you have actually paid for COBRA coverage through December 31, 2014. Thereafter, to the extent provided by the federal COBRA law or state insurance laws, and by Company’s current group health insurance policies, you will be
eligible to continue group health insurance benefits at your own expense subject to the limitations imposed by those policies and applicable law. On or after the Termination Date, you will be provided with a separate notice describing the rights and
obligations under the applicable state and/or federal insurance laws. 

  

	 	4.	You have twenty-one (21) days from today in which to consider this Release Agreement (the “Review Period”). You may not sign this Release Agreement before your Termination Date. You are advised to
consult an attorney regarding this Release Agreement. Once you sign this Release Agreement, return it to Sean McCarthy, 343 Oyster Point Blvd #100, South San Francisco, CA 94080. You may sign this Release Agreement any time after your Termination
Date and before the expiration of the Review Period, but should you do so, you waive what is remaining of the Review Period. 

  

	 	5.	You will have an additional seven (7) days after signing the Release Agreement to revoke your acceptance (the “Revocation Period”) by submitting a written statement of revocation to Sean McCarthy, 343 Oyster
Point Blvd #100, South San Francisco, CA 94080. If you do not timely revoke your acceptance during the Revocation Period, this Release Agreement will become final and effective. If you submit your signed Release Agreement or revocation by mail, your
mailing envelope must be postmarked no later than the submission deadline (unless that day is a Sunday or a holiday, in which event the period is extended to the following day there is mail service). Should you revoke this Release Agreement, then it
shall be null and void. This Release Agreement automatically becomes enforceable and effective on the eighth (8th) day after Company has received the Release Agreement signed by you, provided that there has been no timely revocation.

	 	6.	In order to receive the Separation Benefits provided pursuant to paragraph 3, you must have previously returned all of Company’s property in your possession, except that you may use Company’s laptop computer
following the Termination Date until such time as Company requests that you return the laptop computer, or the end of your consulting period under the Consulting Agreement, whichever occurs sooner. You agree that immediately after you have ceased
providing any services to Company (or earlier if so requested by the Company), you will return to Company all property that belongs to Company, including without limitation, Company’s laptop computer, copies of documents that belong to Company
and files stored on your computer(s) that contain information belonging to Company. 

  

	 	7.	The following are the terms of the general release of claims that you accept as part of this Release Agreement: 

(a) In consideration of the Separation Benefits that you are receiving as provided in paragraph 3 above, and on behalf of
yourself and your heirs, executors, administrators, successors, and assigns, you hereby waive, release, and hold harmless Company, its respective parents, subsidiaries, divisions, units, related companies, each and every past and present member,
shareholder, investor, associate, affiliate, predecessor, successor and related entities, and all of their current or former agents, officers, directors, partners, representatives, attorneys, contractors, insurance companies, administrators,
successors, assigns, current and former employees, plan administrators, insurers, and any other persons acting by, through, under, or in concert with any of the persons or entities listed in this subsection, and each of them (“Released
Parties”), from any and all claims, rights, debts, liabilities, demands, causes of action, obligations, and damages, known or unknown, suspected or unsuspected, arising as of or prior to the date of your signature to this Release Agreement,
under federal, state, local, or common law (the “Released Claims”), including but not limited to claims in any way related to your employment with the Released Parties, or the termination of your employment. The laws under which the
Released Claims may arise include, but are not limited to, the Civil Rights Act of 1866, Title VII of the Civil Rights Act of 1964, the Civil Rights Act of 1991, the Employee Retirement Income Security Act of 1974, the Americans with Disabilities
Act, as amended, the Worker Adjustment and Retraining Notification Act, the Age Discrimination in Employment Act, as amended, the Older Workers Benefit Protection Act, the California Labor Code, the California Business and Professions Code, all
California Wage Orders, the California Fair Employment and Housing Act, the California Family Rights Act, and/or the laws prohibiting discrimination, harassment, and/or retaliation in any state in which you are employed, and any and all federal,
state, and local employment laws, as well as any and all common law tort or contract theories under state federal or local laws. The Released Claims also include claims of discrimination or retaliation on the basis of workers’ compensation
status, but do not include workers’ compensation claims. Nothing in this Release Agreement shall be construed to affect the Equal Employment Opportunity Commission’s (the “Commission”) or any state agency’s
independent right and responsibility to enforce the law, nor does this Release Agreement affect your right to file a charge or participate in an investigation or proceeding conducted by either the Commission or any such state agency, although this
Release Agreement does bar any claim that you might have to receive monetary damages in connection with any Commission or state agency proceeding concerning matters covered by this Release Agreement. Execution of this Release Agreement does not bar
any claim that arises hereafter, including (without limitation) a claim for breach of this Release Agreement, any claim to indemnity under section 2802 of the California Labor Code, or any other claim that by law may not be released. 

 (b) You acknowledge that you have been advised by legal counsel that you are by
this Release Agreement waiving claims pursuant to California Civil Code Section 1542 or the laws of other states similar hereto, and you expressly waive such rights as quoted below: 

A GENERAL RELEASE DOES NOT EXTEND TO CLAIMS WHICH THE CREDITOR DOES NOT KNOW OR SUSPECT TO EXIST IN HIS/HER FAVOR AT THE TIME OF EXECUTING THE
RELEASE, WHICH IF KNOWN BY HIM OR HER MUST HAVE MATERIALLY AFFECTED HIS OR HER SETTLEMENT WITH THE DEBTOR. 
 You hereby expressly waive any
rights you may have under any other statute or common law principles of similar effect. 
 (c) You acknowledge and
understand that the release of claims under the Age Discrimination in Employment Act (“ADEA”), 29 U.S.C. Section 621-634, is subject to special waiver protections under 29 U.S.C. Section 626(f). In accordance with that
section, you specifically agree that you are knowingly and voluntarily releasing and waiving any rights or claims of discrimination under the ADEA. In particular you acknowledge that you understand that: 

 

	 	(i)	you are not waiving any claims for age discrimination under the ADEA that may arise after the date you sign this Release Agreement and you are not waiving vested benefits, if any; 

 

	 	(ii)	you are waiving rights or claims for age discrimination under the ADEA in exchange for payment described in paragraph 3 above, which is in addition to anything of value to which you are already entitled;

  

	 	(iii)	you are advised to consult with and have had an opportunity to consult with an attorney before signing this Release Agreement. 

  

	 	8.	You acknowledge and agree that (a) you possess secret, confidential, or proprietary information or trade secrets concerning the operations, future plans, or business methods of Company and (b) you signed as a
condition of your employment with the Company, and that you continue to be bound by, the Nondisclosure and Assignment of Inventions agreement, entered into by and between Company and you as of September 2, 2010, which survives your separation
from Company, and which obligates you to keep confidential all proprietary information of Company. You agree that the Company would be severely damaged if you used or disclosed this information. 

 

	 	9.	You agree that payment of the Separation Benefits described in paragraph 3 is a benefit that Company is not required to provide to you apart from the provisions of this Release Agreement. 

 

	 	10.	 Without in any way limiting your obligations set forth in the Nondisclosure and Assignment of Inventions Agreement, the Consulting Agreement, the
Scientific Advisory Board Consulting Agreement, the December 23, 2010 Restricted Stock Repurchase Agreement, and the December 23, 2010 Secured Promissory Note, this Release Agreement sets forth the entire agreement between you and Company
regarding its subject matter and supersedes all 

	 	
other written or oral promises or representations about its subject matter. This Release Agreement may not be modified except by a writing signed by both you and an officer of Company. You
understand and agree that this Release Agreement shall not be construed at any time or for any purpose as an admission of any liability or wrongdoing by Company. 

  

	 	11.	You agree that the terms of this Release Agreement are a private matter that will not be divulged to others except to your attorneys, tax, financial, or outplacement advisors, or immediate family members, who in turn
shall not divulge its contents. If you breach this confidentiality clause, Company shall be entitled to recover appropriate and provable damages in a competent legal forum. 

 

	 	12.	This Release Agreement shall be governed by the statutes and common law of the State of California. 

  

	 	13.	If any provision of this Release Agreement or the application thereof to any person, place, or circumstance shall be held by a court of competent jurisdiction to be invalid, unenforceable or void, the remainder of this
Release Agreement and such provision as applied to other person, places, and circumstances shall remain in full force and effect. 

  

	 	14.	You agree not to disparage the Release Parties in any manner likely to be harmful to Company or to any Released Party’s business or personal reputation. 

 

	 	15.	You warrant that you have not filed any lawsuits or administrative claims against any Released Party prior to signing this Release Agreement. 

 

	 	16.	This Release Agreement shall bind the heirs, personal representatives, successors, assigns, executors and administrators of each party, and inure to the benefit of each party, its heirs, successors and assigns.

 BY SIGNING BELOW, YOU ACKNOWLEDGE THAT YOU HAVE READ THIS RELEASE AGREEMENT, UNDERSTAND ITS TERMS AND EFFECT, AND AGREE
TO IT VOLUNTARILY. 
  

											
		 	ACCEPTED AND AGREED TO:	 		 	
						
		 	Date:	 	 9/30/2014
	 		 	Signature:	 	 /s/ Henry B. Lowman

						
		 		 		 		 	Print Name:	 	 Henry Lowman

 Appendix A 

 CytomX Therapeutics, Inc. 

Shareholder Report 
 As of
09/30/2014 
 Holder Name Contains Lowman 

SSN/Tax ID = Excluded 
  

																																			
	 Holder Details
	 	 Class of
Stock
	 	Certificate
No.	 	No. of
Shares	 	 	Effective
Date	 	 	 Issue Reason
	 	Issue Price
per Share	 	 	Shares
Vested	 	 	Vesting
Name	 	Vesting
Start Date	 	 	Date Fully
Vested	 	Legend	 	 Notes

	 Lowman, Henry B.
	 	COMMON	 	CS-32-1	 	 	4,167	  	 	 	12/23/10	  	 	NSO Exercise	 	$	0.0180	  	 	 	0	  	 		 	 	02/05/10	  	 		 		 	
		 	COMMON	 	CS-32-2	 	 	12,644	  	 	 	12/23/10	  	 	NSO Exercise	 	$	0.0180	  	 	 	0	  	 		 	 	02/05/10	  	 		 		 	
		 	COMMON	 	CS-32-3	 	 	4,002,479	  	 	 	12/23/10	  	 	ISO Exercise	 	$	0.0180	  	 	 	0	  	 		 	 	09/22/10	  	 		 		 	
		 	COMMON	 	CS-60	 	 	8,333	  	 	 	06/20/13	  	 	NSO Exercise	 	$	0.0180	  	 	 	0	  	 		 	 	02/05/10	  	 		 		 	Option exercised on 6/20/2013 but stock certificate not prepared until 4/1/2014.
		 	COMMON	 	CS-61	 	 	25,286	  	 	 	06/20/13	  	 	NSO Exercise	 	$	0.0180	  	 	 	0	  	 		 	 	02/05/10	  	 		 		 	Option exercised on 6/20/2013 but stock certificate not prepared until 4/1/2014.
		 	COMMON	 	CS-62	 	 	2,001,239	  	 	 	06/20/13	  	 	ISO Exercise	 	$	0.0180	  	 	 	0	  	 		 	 	05/03/11	  	 		 		 	Option exercised on 6/20/2013 but stock certificate not prepared until 4/1/2014.
		 	COMMON	 	CS-63	 	 	833,850	  	 	 	06/20/13	  	 	ISO Exercise	 	$	0.0180	  	 	 	0	  	 		 	 	09/14/11	  	 		 		 	Option exercised on 6/20/2013 but stock certificate not prepared until 4/1/2014.
		 		 		 	  
	  
	 	 				 		 				 	  
	  
	 	 		 				 		 		 	
		 	 Subtotal
	 		 	 	6,887,998	  	 	 	[10.97%]	  	 		 				 	 	0	  	 		 				 		 		 	
		 		 		 	  
	  
	 	 	  
	  
	 	 		 				 	  
	  
	 	 		 				 		 		 	
	 Total Outstanding Shares of COMMON
	 	 	6,887,998	  	 				 		 				 	 	0	  	 		 				 		 		 	
	 GRAND TOTAL
	 	 	6,887,998	  	 				 		 				 	 	0	  	 		 				 		 		 	
	 Total
No. of
Shareholders
	 	1	 		 				 				 		 				 				 		 				 		 		 	
													
	 Legends Key
	 		 		 				 				 		 				 				 		 				 		 		 	

 CytomX Therapeutics, Inc. 

Personnel Summary 
 As of
09/30/2014 
 Holder Name Contains lowman 

SSN/Tax ID = Excluded 
  

																																																									
	 Holder
Details
	 	Plan
Name/
Grant
Type	 	Grant
No.	 	 	Grant
Date	 	 	No. of
Shares
Granted	 	 	Exercise
Price
per
Share	 	 	Vesting
Start
Date/Key	 	Early
Exercise	 	 	Shares
Vested	 	 	Shares
Unvested	 	 	Shares
Exercised	 	 	Shares
Subject to
Repurchase	 	 	Shares
Canceled	 	 	Shares
Outstanding	 	 	Shares
Outstanding
Exercisable	 	 	Date Fully
Vested	 
	 Lowman, Henry B.
	 		 				 				 				 				 		 				 				 				 				 				 				 				 				 			
		 	2010
SIP
ISO	 	 	10-039	  	 	 	12/02/2010	  	 	 	4,002,479	  	 	$	0.0180	  	 	09/22/2010
A	 	 	Y	  	 	 	4,002,479	  	 	 	0	  	 	 	4,002,479	  	 	 	0	  	 	 	0	  	 	 	0	  	 	 	0	  	 	 	09/22/2014	  
		 	2010
SIP
ISO	 	 	10-055	  	 	 	05/03/2011	  	 	 	4,002,479	  	 	$	0.0180	  	 	05/03/2011
A	 	 	N	  	 	 	3,335,399	  	 	 	667,080	  	 	 	2,001,239	  	 	 	0	  	 	 	0	  	 	 	2,001,240	  	 	 	1,334,160	  	 	 	05/03/2015	  
		 	2010
SIP
ISO	 	 	10-060	  	 	 	09/21/2011	  	 	 	2,001,240	  	 	$	0.0180	  	 	09/14/2011
A	 	 	N	  	 	 	1,500,930	  	 	 	500,310	  	 	 	833,850	  	 	 	0	  	 	 	0	  	 	 	1,167,390	  	 	 	667,080	  	 	 	09/14/2014	  
		 	2010
SIP
NSO	 	 	10-024	  	 	 	09/22/2010	  	 	 	45,517	  	 	$	0.0180	  	 	02/05/2010
C*	 	 	N	  	 	 	45,517	  	 	 	0	  	 	 	37,930	  	 	 	0	  	 	 	0	  	 	 	7,587	  	 	 	7,587	  	 	 	02/05/2013	  
		 	2010
SIP
NSO	 	 	10-023	  	 	 	09/22/2010	  	 	 	15,000	  	 	$	0.0180	  	 	02/05/2010
C*	 	 	N	  	 	 	15,000	  	 	 	0	  	 	 	12,500	  	 	 	0	  	 	 	0	  	 	 	2,500	  	 	 	2,500	  	 	 	02/05/2013	  
		 	2010
SIP
ISO	 	 	10-080	  	 	 	02/26/2013	  	 	 	5,172,210	  	 	$	0.0150	  	 	02/26/2013
G	 	 	N	  	 	 	2,155,087	  	 	 	3,017,123	  	 	 	0	  	 	 	0	  	 	 	0	  	 	 	5,172,210	  	 	 	2,155,087	  	 	 	01/31/2017	  
											
	 Total No. of Options
	   
	 	 	15,238,925	  	 				 		 				 				 				 				 				 				 			
		 		 				 				 				 				 		 				 	  
	  
	 	 	  
	  
	 	 	  
	  
	 	 	  
	  
	 	 	  
	  
	 	 	  
	  
	 	 	  
	  
	 	 			
	 Total No. of SPRs
	   
	 	 	0	  	 				 		 				 	 	11,054,412	  	 	 	4,184,513	  	 	 	6,887,998	  	 	 	0	  	 	 	0	  	 	 	8,350,927	  	 	 	4,166,414	  	 			
		 		 				 				 	  
	  
	 	 				 		 				 				 				 				 				 				 				 				 			
	 Subtotal
	   
	 	 	15,238,925	  	 				 		 				 				 				 				 				 				 				 				 			
		 		 				 				 	  
	  
	 	 				 		 				 	  
	  
	 	 	  
	  
	 	 	  
	  
	 	 	  
	  
	 	 	  
	  
	 	 	  
	  
	 	 	  
	  
	 	 			
	 GRAND TOTAL
	   
	 	 	15,238,925	  	 				 		 				 	 	11,054,412	  	 	 	4,184,513	  	 	 	6,887,998	  	 	 	0	  	 	 	0	  	 	 	8,350,927	  	 	 	4,166,414	  	 			
	 Total No. of
Optionholders:
	 		 				 				 				 				 		 				 				 				 				 				 				 				 				 			

  

			
	Vesting Schedule Key
	 A
	  	25% @ 1yr, 1/48th monthly (2010 SIP)
	 C*
	  	Customized
	 G
	  	1/48th per month on last day (2011 SIP)

 Footnote(s): 
 The Exercise
Price(s) Per Share in this report have been rounded to 4 decimal places for display purposes, although the actual price may be up to 15 decimal places as indicated on the individual security screen. 

 EXHIBIT A 

 CONSULTING AGREEMENT 

This Consulting Agreement (“Agreement”) is entered into as of October 1, 2014 by and between CytomX Therapeutics, Inc., a Delaware
corporation (the “Company”) and Henry Lowman, Ph.D., an individual (“Consultant”). The Company desires to retain Consultant as an independent contractor to perform consulting services for the Company, and Consultant
is willing to perform such services, based upon the terms described below. In consideration of the mutual promises contained herein, the parties agree as follows: 

I. Services and Compensation. Consultant agrees to perform for the Company the services described in Exhibit A (the
“Services”), and the Company agrees to pay Consultant the compensation described in Exhibit A for Consultant’s performance of the Services. 

II. Confidentiality. 
 A.
Definition. “Confidential Information” means any and all trade secrets, knowledge, data and other information owned, held or known by the Company or any entity that now or hereafter is directly or indirectly controlled by, or
in control of, or commonly controlled with the Company (an “Affiliate”) and relating to products, potential products, contracts, and specifications, processes, know-how, designs, formulas, data, inventions, customer lists, business
plans, marketing plans and strategies, pricing strategies and other subject matter pertaining to any research, business or planned or contemplated business of the Company, any Affiliate of the Company or any customer of the Company or other party
that heretofore has or hereafter may contract with the Company for the performance of services or delivery of products. Confidential information shall include such information as is currently owned, held or known by the Company, and such other
information as the Company may develop or receive in the future through the Consultant’s efforts or otherwise. 
 B. Nonuse and
Nondisclosure. Consultant will not, during or subsequent to the term of this Agreement, (i) use the Confidential Information for any purpose whatsoever other than the performance of the Services on behalf of the Company or
(ii) disclose the Confidential Information to any third party. Consultant agrees that all Confidential Information will remain the sole property of the Company. Consultant also agrees to take all reasonable precautions to prevent any
unauthorized disclosure of such Confidential Information, including, but not limited to, having each of Consultant’s employees and contractors, if any, with access to any Confidential Information. Without the Company’s prior written
approval, Consultant will not directly or indirectly disclose to anyone the existence of this Agreement or the fact that Consultant has this arrangement with the Company. Consultant acknowledges that it possesses secret, confidential, or proprietary
information or trade secrets concerning the operations, future plans, or business methods of Company and that Consultant signed the Nondisclosure and Assignment of Inventions Agreement on September 2, 2010 which survives Consultant’s
separation from Company, and which obligates Consultant to keep confidential all proprietary information of Company. Consultant agrees that Company would be severely damaged if Consultant used of disclosed Confidential Information. 

 C. Former Client Confidential Information. Consultant agrees that Consultant will not,
during the term of this Agreement, improperly use or disclose any proprietary information or trade secrets of any former or current employer of Consultant or other person or entity with which Consultant has an agreement or duty to keep in confidence
information acquired by Consultant, if any. Consultant also agrees that Consultant will not bring onto the Company’s premises any unpublished document or proprietary information belonging to any such employer, person or entity unless consented
to in writing by such employer, person or entity. 
 D. Third Party Confidential Information. Consultant recognizes that the Company
has received and in the future will receive from third parties their confidential or proprietary information subject to a duty on the Company’s part to maintain the confidentiality of such information and to use it only for certain limited
purposes. Consultant agrees that, during the term of this Agreement and thereafter, Consultant owes the Company and such third parties a duty to hold all such confidential or proprietary information in the strictest confidence and not to disclose it
to any person, firm or corporation or to use it except as necessary in carrying out the Services for the Company consistent with the Company’s agreement with such third party. 

E. Return of Materials. Upon the termination of this Agreement, or upon Company’s earlier request, Consultant will deliver to the
Company all of the Company’s property, including but not limited to all electronically stored information and passwords to access such property, or Confidential Information that Consultant may have in Consultant’s possession or control.

 III. Ownership. 
 A.
Assignment. Consultant agrees that all copyrightable material, notes, records, drawings, designs, inventions, improvements, developments, discoveries and trade secrets conceived, discovered, developed or reduced to practice by Consultant,
solely or in collaboration with others, during the term of this Agreement that relate in any manner to the business of the Company that Consultant may be directed to undertake, investigate or experiment with or that Consultant may become associated
with in work, investigation or experimentation in the Company’s line of business in performing the Services under this Agreement (collectively, “Inventions”), are the sole property of the Company. Consultant also agrees to
assign (or cause to be assigned) and hereby assigns fully to the Company all Inventions and any copyrights, patents or other intellectual property rights relating to all Inventions. 

B. Further Assurances. Consultant agrees to assist Company, or its designee, at the Company’s expense, in every proper way to
secure the Company’s rights in Inventions and any copyrights, patents or other intellectual property rights relating to all Inventions in any and all countries, including the disclosure to the Company of all pertinent information and data with
respect to all Inventions, the execution of all applications, specifications, oaths, assignments and all other instruments that the Company may deem necessary in order to apply for and obtain such rights and in order to assign and convey to the
Company, its successors, assigns and nominees 

 
the sole and exclusive right, title and interest in and to all Inventions, and any copyrights, patents or other intellectual property rights relating to all Inventions. Consultant also agrees
that Consultant’s obligation to execute or cause to be executed any such instrument or papers shall continue after the termination of this Agreement. 

C. Pre-Existing Materials. Subject to Section 3.A, Consultant agrees that if, in the course of performing the Services,
Consultant incorporates into any Invention developed under this Agreement any pre-existing invention, improvement, development, concept, discovery or other proprietary information owned by Consultant or in which Consultant has an interest,
(i) Consultant will inform Company, in writing before incorporating such invention, improvement, development, concept, discovery or other proprietary information into any Invention, and (ii) the Company is hereby granted a nonexclusive,
royalty-free, perpetual, irrevocable, worldwide license to make, have made, modify, use and sell such item as part of or in connection with such Invention. Consultant will not incorporate any invention, improvement, development, concept, discovery
or other proprietary information owned by any third party into any Invention without Company’s prior written permission. 
 D.
Attorney-in-Fact. Consultant agrees that, if the Company is unable because of Consultant’s unavailability, dissolution, mental or physical incapacity, or for any other reason, to secure Consultant’s signature for the purpose of
applying for or pursuing any application for any United States or foreign patents or copyright registrations covering the Inventions assigned to the Company in Section 3.A, then Consultant hereby irrevocably designates and appoints the
Company and its duly authorized officers and agents as Consultant’s agent and attorney-in-fact, to act for and on Consultant’s behalf to execute and file any such applications and to do all other lawfully permitted acts to further the
prosecution and issuance of patents, copyright registrations with the same legal force and effect as if executed by Consultant. 
 IV.
Conflicting Obligations. 
 A. Conflicts. Consultant certifies that Consultant has no outstanding agreement or obligation that
is in conflict with any of the provisions of this Agreement or that would preclude Consultant from complying with the provisions of this Agreement. Consultant will not enter into any such conflicting agreement during the term of this Agreement.
Consultant’s violation of this Section 4.A will be considered a material breach under Section 6. 
 B.
Substantially Similar Designs. In view of Consultant’s access to the Company’s trade secrets and proprietary know-how, Consultant agrees that Consultant will not, without Company’s prior written approval, design identical or
substantially similar designs as those developed under this Agreement for any third party during the term of this Agreement and for a period of 24 months after the termination of this Agreement. Consultant acknowledges that the obligations in this
Section 4 are ancillary to Consultant’s nondisclosure obligations under Section 2. 

 V. Reports. 

Consultant also agrees that Consultant will, from time to time during the term of this Agreement or any extension thereof, keep the Company
advised as to Consultant’s progress in performing the Services under this Agreement. Consultant further agrees that Consultant will, as requested by the Company, prepare written reports with respect to such progress. The Company and Consultant
agree that the time required to prepare such written reports will be considered time devoted to the performance of the Services. 
 VI. Term
and Termination. 
 A. Term. The term of this Agreement will begin on October 1, 2014 and will continue until December 31,
2014. 
 B. Survival. Upon the termination of this Agreement on December 31, 2014, all rights and duties of the Company and
Consultant toward each other shall cease except: 
 1. The Company will pay, within 30 days after December 31, 2014, all amounts owing
to Consultant for Services completed and accepted by the Company prior to the termination date and related expenses, if any, submitted in accordance with the Company’s policies and in accordance with the provisions of Section 1 of this
Agreement; and 
 2. Section 2 (Confidentiality), Section 3 (Ownership), Section 4 (Conflicting Obligations), Section 7
(Independent Contractor; Benefits), Section 8 (Indemnification), Section 9 (Nonsolicitation) and Section 10 (Arbitration and Equitable Relief) will survive termination of this Agreement. 

VII. Independent Contractor; Benefits. 

A. Independent Contractor. It is the express intention of the Company and Consultant that Consultant performs the Services as an
independent contractor to the Company. Nothing in this Agreement shall in any way be construed to constitute Consultant as an agent, employee or representative of the Company. Without limiting the generality of the foregoing, Consultant is not
authorized to bind the Company to any liability or obligation or to represent that Consultant has any such authority. Consultant agrees to furnish (or reimburse the Company for) all tools and materials necessary to accomplish this Agreement and
shall incur all expenses associated with performance, except as expressly provided in Exhibit A. Consultant acknowledges and agrees that Consultant is obligated to report as income all compensation received by Consultant pursuant to this
Agreement. Consultant agrees to and acknowledges the obligation to pay all self-employment and other taxes on such income. 
 B.
Benefits. The Company and Consultant agree that Consultant will receive no Company-sponsored benefits from the Company, other than as specified by the Separation and Release Agreement (i.e., if Consultant timely elects to continue health care
coverage under COBRA and submits for reimbursement to the Company monthly COBRA premiums actually paid through December 31, 2014). If Consultant is reclassified by a state or federal agency or court as Company’s employee, Consultant will
become a reclassified employee and will receive 

 
no benefits from the Company, except those mandated by state or federal law, even if by the terms of the Company’s benefit plans or programs of the Company in effect at the time of such
reclassification, Consultant would otherwise be eligible for such benefits. 
 VIII. Indemnification. Consultant agrees to
indemnify and hold harmless the Company and its directors, officers and employees from and against all taxes, losses, damages, liabilities, costs and expenses, including attorneys’ fees and other legal expenses, arising directly or indirectly
from or in connection with (i) any negligent, reckless or intentionally wrongful act of Consultant or Consultant’s assistants, employees or agents, (ii) a determination by a court or agency that the Consultant is not an independent
contractor, (iii) any breach by the Consultant or Consultant’s assistants, employees or agents of any of the covenants contained in this Agreement, (iv) any failure of Consultant to perform the Services in accordance with all
applicable laws, rules and regulations, or (v) any violation or claimed violation of a third party’s rights resulting in whole or in part from the Company’s use of the work product of Consultant under this Agreement. 

IX. Nonsolicitation. From the date of this Agreement until 12 months after the termination of this Agreement (the
“Restricted Period”), Consultant will not, without the Company’s prior written consent, directly or indirectly, solicit, hire or encourage any employee or contractor of the Company or its affiliates to terminate employment
with, or cease providing services to, the Company or its affiliates. During the Restricted Period, Consultant will not, whether for Consultant’s own account or for the account of any other person, firm, corporation or other business
organization, intentionally interfere with any person who is or during the period of Consultant’s engagement by the Company was a partner, supplier, customer or client of the Company or its affiliates. 

X. Arbitration and Equitable Relief. 

A. Arbitration. The Consultant and the Company agree that if any dispute arises regarding this agreement or the terms and conditions of
the consultancy with the Company, and that dispute is not resolved within ten (10) days of the date on which either party delivers to the other party a written notice invoking the arbitration provisions of this paragraph, then to the extent
permitted by applicable law, such dispute shall be resolved by final and binding arbitration in San Francisco, California, pursuant to the Federal Arbitration Act, 9 U.S.C. §§ 1-14, or if that Act is held to be inapplicable for any reason,
the California Arbitration Act, California Civil Procedure Code §§ 1280 et seq. The arbitration shall be conducted through JAMS before a single neutral arbitrator, in accordance with the JAMS employment arbitration rules then in
effect. The JAMS rules may be found and reviewed at http://www.jamsadr.com/rules-employment-arbitration. The decision of the arbitrator shall be final and binding on the parties, and judgment thereon may be entered in a court of competent
jurisdiction. The parties acknowledge and agree that they are each waiving their rights to a jury trial in favor of having their disputes resolved by final and binding arbitration. The disputes that the parties agree to submit to final
and binding arbitration include but are not limited to any statutory claims under any state or federal law, including, but not limited to, 

 
claims under Title VII of the Civil Rights Act of 1964, the Americans with Disabilities Act of 1990, the Age Discrimination in Employment Act of 1967, the Older Workers Benefit Protection Act,
the California Fair Employment and Housing Act, the California Business and Professions Code and the California Labor Code, as well as any common law claims of harassment, discrimination, wrongful termination, retaliation, fraud, negligent
misrepresentation, breach of contract and any statutory or common law claims for unpaid wages, commissions, bonus or other compensation. Notwithstanding anything to contrary herein, either party may seek a temporary restraining order, preliminary
injunction or other provisional injunctive or declaratory relief in any court of competent jurisdiction at any time to ensure that the relief sought in arbitration is not rendered ineffectual by any interim harm. 

B. Voluntary Nature of Agreement. Consultant acknowledges and agrees that Consultant is executing this Agreement voluntarily and
without any duress or undue influence by the Company or anyone else. Consultant further acknowledges and agrees that Consultant has carefully read this Agreement and has asked any questions needed to understand the terms, consequences and binding
effect of this Agreement and fully understand it, including that Consultant is waiving its right to a jury trial. Finally, Consultant agrees that Consultant has been provided an opportunity to seek the advice of an attorney of its choice before
signing this Agreement. 
 XI. Miscellaneous. 

A. Governing Law. This Agreement shall be governed by and construed in accordance with California law. 

B. Assignability. Except as otherwise provided in this Agreement, Consultant may not sell, assign or delegate any rights or obligations
under this Agreement. 
 C. Entire Agreement. This Agreement constitutes the entire agreement between the parties with respect to the
subject matter of this Agreement and supersedes all prior written and oral agreements between the parties regarding the subject matter of this Agreement. 

D. Headings. Headings are used in this Agreement for reference only and shall not be considered when interpreting this Agreement. 

 E. Notices. Any notice or other communication required or permitted by this Agreement to
be given to a party shall be in writing and shall be deemed given if delivered personally or by commercial messenger or courier service, or mailed by U.S. registered or certified mail (return receipt requested), or sent via facsimile (with receipt
of confirmation of complete transmission) to the party at the party’s address or facsimile number written below or at such other address or facsimile number as the party may have previously specified by like notice. If by mail, delivery shall
be deemed effective 3 business days after mailing in accordance with this Section 11.E. 
 (1) If to the Company, to: 

CytomX Therapeutics, Inc. 

Attention: Sean McCarthy 

343 Oyster Point Blvd. #100 

South San Francisco, CA 94080 

With a copy to: 

Sidley Austin LLP 

Attention: Sam Zucker 

1001 Page Mill Road, Building 1 

Palo Alto, CA 94304 

(2) If to Consultant, to the address for notice on the signature page to this Agreement or, if no such address is provided, to the last
address of Consultant provided by Consultant to the Company. 
 F. Attorneys’ Fees. In any court action at law or equity that is
brought by one of the parties to this Agreement to enforce or interpret the provisions of this Agreement, the prevailing party will be entitled to reasonable attorneys’ fees, in addition to any other relief to which that party may be entitled.

 G. Severability. If any provision of this Agreement is found to be illegal or unenforceable, the other provisions shall remain
effective and enforceable to the greatest extent permitted by law. 

 IN WITNESS WHEREOF, the parties hereto have executed this Consulting Agreement as of the date
first written above. 
  

									
	CONSULTANT	 		 	CytomX Therapeutics, Inc.
					
	By:	 	 /s/ Henry B. Lowman, Ph.D.
	 		 	By:	 	 /s/ Sean McCarthy

					
	Name:	 	 Henry Lowman
	 		 	Name:	 	 Sean McCarthy

					
	Title:	 	 Consulting Chief Scientific Officer
	 		 	Title:	 	 CEO

				
	Address for Notice:	 		 		 	
				
	 PO Box 2556
	 		 		 	
				
	 400 San Juan Ave.
	 		 		 	
				
	 El Granada, CA 94018-2556
	 		 		 	

 EXHIBIT A 

Services and Compensation 
  

	 	1.	Contact. Consultant’s principal Company contact: 

 Sean McCarthy, Chief Executive
Officer 
  

	 	2.	Services. The Services shall include, but are not limited to, the following: duties related to the transition of work. 

  

	 	3.	Date Services to Begin. October 1, 2014 

  

	 	4.	Date Services to End. December 31, 2014 

  

	 	5.	Compensation. 

  

	 	a)	The Company will pay Consultant $25,008.33 per month during the term of this Agreement. 

  

	 	b)	The Company will reimburse Consultant for all reasonable expenses incurred by Consultant in performing the Services pursuant to this Agreement, if Consultant receives written consent from an authorized agent of the
Company prior to incurring such expenses and submits receipts for such expenses to the Company in accordance with Company policy. 

  

	 	c)	At the end of the term of this Consulting Agreement, Consultant shall submit to the Company a written invoice for Services and expenses, and such statement shall be subject to the approval of the contact person listed
above or other designated agent of the Company. 

 EXHIBIT B 

 SCIENTIFIC ADVISORY BOARD CONSULTING AGREEMENT 

THIS CONSULTING AGREEMENT (the “Agreement”) is made and
entered into by and between CYTOMX THERAPEUTICS, INC., a Delaware corporation, with an address at 343 Oyster Point Blvd., Suite 100, South San Francisco, CA 94080-1913, (“Company”)
and Henry B. Lowman, Ph.D. at 400 San Juan Ave., P.O. Box 2556, El Granada, CA 94018-2556 (“Consultant”), effective as of January 5, 2015. 

RECITALS 

WHEREAS, Consultant has skills and knowledge in the Company’s field of endeavor and thus is well
suited to advise the Company; and 
 WHEREAS, the Company desires that Consultant advise and consult
with the Company in Consultant’s area of expertise and on the terms and conditions set forth herein; 
 NOW
THEREFORE, in consideration of the mutual obligations specified in this Agreement, the parties agree to the following: 

1. CONSULTING SERVICES. Consultant shall provide consulting services to the Company
generally in the specialized field identified in Exhibit A (such field, the “Field”, and such services the “Services”). The specific nature and amount of the consulting services to be performed by Consultant hereunder within the
Field shall be as described generally in Exhibit A and in accordance with the Company’s more specific instructions. Exhibit A lists Consultant’s main contact person for the Services, and this person will be the primary source of
Company’s more specific instructions regarding the Services. Consultant will perform the Services in strict accordance with Exhibit A and the Company’s other direction, using Consultant’s highest degree of professional skill and
expertise. 
 Consultant shall render the Services at such times and in such quantities as are set forth in Exhibit A. Consultant shall
perform the Services at the Company’s principal place of business, another Company location, or at other places set forth in Exhibit A. Consultant also agrees to perform a reasonable amount of informal consultation with the Company over the
telephone or otherwise. 
 If Consultant is not a natural person, then Consultant shall perform the Services hereunder by the activities of
its personnel listed in Exhibit A. Each person performing the Services hereunder must agree in writing before beginning work on the Services to be legally bound to the terms of this Agreement as applicable to her or him, including Sections 4, 5, 6
and 7. (If Consultant is not a natural person and requests a form of agreement to aid in its compliance with this paragraph, Company will gladly provide one.) 

2. COMPENSATION. Company shall compensate Consultant in accordance with Exhibit A for Services actually
provided by Consultant in accordance with this Agreement. 
 3. AMENDMENTS TO EXHIBIT A.
Exhibit A sets forth the specifics of the Field, the Services, the location of the Services and compensation for the Services as of the Effective Date. Exhibit A may only be amended by a writing signed by an authorized representative of each party
(in the case of the Company, a person having a seniority level of Vice President or higher). 
 4. INDEPENDENT
CONTRACTOR STATUS. It is understood and agreed that Consultant is an independent contractor, is not an agent or employee of the Company, and is not authorized to act on behalf of the Company.
Consultant agrees not to hold himself or herself out as, or give any person any 

 
reason to believe that he or she is an employee, agent, joint venturer or partner of the Company. Consultant will not be eligible for any employee benefits, nor will the Company make deductions
from any amounts payable to Consultant for taxes or insurance (except to the extent the Company is required by law to do so). All payroll and employment taxes, insurance, and benefits shall be the sole responsibility of Consultant. Consultant
retains the right to provide services for others during the term of this Agreement and is not required to devote his or her services exclusively for the Company. This Section applies equally to Consultant’s personnel performing hereunder. 

5. NO SOLICITATION. During the term of this Agreement and for three (3) years after
its termination, Consultant (and its personnel performing hereunder) will not personally or through others recruit, solicit or induce any employee of the Company to terminate his or her employment with the Company. 

6. MAINTAINING CONFIDENTIAL INFORMATION. 

6.1 Company Information. During the term of this Agreement and in the course of Consultant’s performance hereunder, Consultant may
receive or otherwise be exposed to confidential and proprietary information relating to the Company’s technology, know-how, data, inventions, developments, plans, business practices, and strategies, and those of the Company’s collaborators
and business associates. Such confidential and proprietary information of the Company (collectively referred to as “Information”) may include but not be limited to: (i) information supplied to Consultant with the legend
“Confidential” or equivalent; (ii) the Company’s marketing and customer support strategies, financial information (including sales, costs, profits and pricing methods), internal organization, employee information, customer lists
and business plans; (iii) the Company’s technology, including, but not limited to, discoveries, inventions, research and development efforts, manufacturing processes, assays, data (including without limitation preclinical, clinical and
manufacturing data), software, trade secrets, processes, compounds, product, candidates, products, samples, media and/or cell lines (and procedures and formulations for producing any such samples, media and/or cell lines), vectors, viruses, assays,
plasmids, formulas, methods, protocols, clinical trial designs and product know-how and show-how; (iv) all derivatives, improvements, additions, modifications, and enhancements to any of the above, including any such information or material
created or developed by Consultant under this Agreement; (v) information of third parties as to which the Company has an obligation of confidentiality; and (vi) information regarding the Consulting Inventions (defined in Section 7.1).

 Consultant acknowledges the confidential and secret character of the Information and agrees that the Information (with the exception of
information in category (v)) is the sole, exclusive and extremely valuable property of the Company. Accordingly, Consultant shall not reproduce any of the Information without the applicable prior written consent of the Company, use the Information
except in the performance of this Agreement, nor disclose all or any part of the Information in any form to any third party, either during or after the term of this Agreement. Upon termination of this Agreement for any reason, including expiration
of term, Consultant agrees to cease using and to return to the Company all whole and partial copies of the Information. 
 Consultant shall
not remove from the premises of Company or otherwise transfer to any third party any materials to which Company provides Consultant access, unless Consultant has express advance written consent from Company. 

6.2 Employer Information. Consultant agrees that she, he or it will not, during her or his engagement with the Company, improperly use
or disclose any proprietary information or trade secrets of her or his former or current employers or companies with which she or he has or has had a consulting or other relationship, if any, and that she or he will not bring onto the premises of
the Company any 

 
unpublished documents or any property belonging to her or his former or concurrent employers or companies (or that of Consultant’s personnel performing hereunder) unless consented to in
writing by said employers or companies, other than Background Technology in accordance with Section 7 .3. 
 6.3 Third Party
Information. Consultant recognizes that the Company has received and in the future will receive from third patties their confidential or proprietary information subject to a duty on the Company’s part to maintain the confidentiality of such
information and, in some cases, to use it only for certain limited purposes. Consultant agrees that he, she or it owes the Company and such third parties, both during the term of her or his engagement and thereafter, a duty to hold all such
confidential or proprietary information in the strictest confidence and not to disclose it to any person, firm or corporation (except in a manner that is consistent with the Company’s agreement with the third patty) or use it for the benefit of
anyone other than the Company or such third party (consistent with the Company’s agreement with the third patty). 
 7.
INVENTIONS. 
 7.1 Disclosure of Inventions. Consultant shall promptly and fully disclose to the
Company any and all ideas, improvements, inventions, know-how, techniques and works of authorship learned, conceived or developed by Consultant pursuant to her, his or its performance of the Services for the Company and/or using the Information
(whether such use of Information occurs during or after the term of this Agreement (and without implying any right to use the Information outside of performing the Services)) (all of the foregoing, together with all intellectual property rights
therein (including without limitation patent applications and patents), the “Consulting Inventions”). All inventions by Consultant during the term of the Services or within one (1) year thereafter and having utility in the
field of protease-activated biologics shall be presumed to have been made using the Information unless Consultant is able to show conclusively that they were not. Consultant shall keep and maintain adequate and current records (in the form of
notes, sketches, drawings, laboratory notebooks or any other form that may be required by the Company) of all work performed relating to the Services, including all proprietary information developed relating thereto. Such records shall be available
to and remain the sole property of the Company at all times. 
 7.2 Inventions Assigned to the Company. Consultant agrees that any
and all Consulting Inventions shall be the sole and exclusive property of the Company. Accordingly, Consultant hereby assigns to the Company all her, his or its right, title and interest in and to the Consulting Inventions, and agrees to execute and
deliver (during and after the term of this Agreement and for no additional consideration) all documents and take all reasonable, lawful actions to assist the Company to evidence or record such assignment or perfect, defend or enforce the Consulting
Inventions. Consultant shall do so both during and after the term of this Agreement, for no additional consideration beyond the payments from Company to Consultant for the Services during the term of this Agreement. Further, if Company is unable,
after making reasonable inquiry, to obtain Consultant’s signature on any such documents, Consultant hereby appoints Company as Consultant’s attorney-in-fact to execute and deliver such documents. Consultant explicitly. acknowledges and
agrees that all works of authorship contained in the Consulting Inventions are “works for hire” under the copyright laws of the United States, and that the Company shall own the copyright in all such works of authorship. 

7.3 Background Technology. Consultant shall specifically describe and identify in Exhibit B any and all technology (including without
limitation information, materials and patent rights) that (i) Consultant may use in performing the Services; (ii) is owned by Consultant free of encumbrances or licensed to Consultant with the right to sublicense the Company; and
(iii) is in existence prior to the Effective Date (the “Background Technology”). Consultant hereby grants to Company a non-exclusive, royalty-free and worldwide right to use and sublicense the use of any Background Technology
for the purpose of developing and marketing Company products and programs, but not for the purpose of marketing the Background Technology separately from these products and programs. 

 7.4 Obligation to Keep the Company Informed. During the term of this Agreement, and for
one (1) year after its termination for any reason, Consultant will promptly disclose to the Company fully and in writing all patent applications filed by her, him or it, or on her, his or its behalf. 

7.5 Personnel. If Consultant is not a natural person, then its personnel performing hereunder must agree in writing to all of
Section 7. 
 8. TERMINATION. The Company may terminate this Agreement at any time with or without
cause by giving Consultant thirty (30) days written notice unless Exhibit A provides otherwise. Consultant may likewise terminate this Agreement with thirty (30) days written notice. If this Agreement terminates, Consultant shall cease
work immediately after giving or receiving such notice or termination, unless otherwise advised by the Company, shall return to the Company all Information, Consulting Inventions, and other materials belonging to the Company, and shall notify the
Company of costs incurred up to the termination date. Sections 6- 14 of this Agreement shall survive any termination of this Agreement. Unless earlier terminated as provided herein, this Agreement shall expire one year after the Effective Date. 

9. COMPLIANCE WITH APPLICABLE LAWS. Consultant warrants that
all material supplied and work performed under this Agreement complies with or will comply with all applicable United States and foreign taws and regulations. 

10. ASSIGNMENT; BENEFIT. This Agreement is for the personal services of Consultant (or one
or more of its personnel) and may not be assigned by her, him or it. Consultant may not delegate any of his, her or its duties under this Agreement nor shall it be assignable by Consultant by operation of law, without the prior written consent of
the Company. This Agreement may be assigned at any time by the Company in its discretion, provided that Consultant would not be required to perform personal services for any entity not (a) affiliated with the Company or (b) that has
merged with or acquired all or substantially all of its assets to which the Services relate. The parties’ rights and obligations under this Agreement will bind and inure to the benefit of their respective successors, heirs, executors, and
administrators and permitted assigns. 
 11. LEGAL AND EQUITABLE
REMEDIES. Consultant hereby acknowledges and agrees that if Consultant breaches this Agreement, including, without limitation, by the actual or threatened disclosure of Information or Consulting Inventions without
the prior express written consent of the Company, the Company will suffer an irreparable injury, such that no remedy at law will afford it adequate protection against, or appropriate compensation for, such injury. Accordingly, Consultant hereby
agrees that the Company shall be entitled to specific performance of Consultant’s obligations under this Agreement, as welt as such further relief as may be granted by a court of competent jurisdiction. 

12. GOVERNING LAW; SEVERABILITY. This
Agreement shall be governed by and construed according to the laws of California, without giving effect to its conflict of laws rules. If any provision of this Agreement is found by a court of competent jurisdiction to be unenforceable, that
provision shall be severed and the remainder of this Agreement shall continue in full force and effect. Any disputes arising under this Agreement shall be resolved by trial to a judge as the finder of fact seated in a court of competent subject
matter jurisdiction in San Mateo County, California. Each party hereby consents to, and waives any defenses that party may have to or conflicting with, the personal jurisdiction and venue of all such courts or relating to trial to a judge (including
without limitation the defense of forum non conveniens). 

 13. COMPLETE UNDERSTANDING;
MODIFICATION. This Agreement constitutes the final, exclusive and complete understanding and agreement of the Company and Consultant with respect to the subject matter hereof. There are no other understandings,
agreements, representations or warranties between the parties with respect to that subject matter other than those set forth in this Agreement. Any waiver, modification or amendment of any provision of this Agreement shall be effective only if in
writing and signed by a Company officer. 
 14. NOTICES. Any notices required or permitted hereunder
shall be given to the appropriate party at the address specified below or at such other address as the party shall specify in writing. Such notice shall be deemed given upon personal delivery to the appropriate address or sent by certified or
registered mail, three days after the date of mailing. Either party may update its notice address by written notice to the other party. 
  

			
	If to the Company:	  	If to the Consultant:
		
	CYTOMX THERAPEUTICS, INC.	  	Henry B. Lowman, Ph.D.
	343 Oyster Point Blvd., Suite 100	  	400 San Juan Ave., P.O. Box 2556
	South San Francisco, CA 94080-1913	  	El Granada, CA 94018-2556

 IN WITNESS WHEREOF, the parties hereto have executed this
Agreement as of the date first set forth above. 
  

									
	CYTOMX THERAPEUTICS, INC.	 		  	CONSULTANT
					
	SIGNED	 	 /s/ Sean McCarthy
	 		  	SIGNED	 	 /s/ Henry B. Lowman, Ph.D.

	TO HAVE EFFECT AS OF THE EFFECTIVE DATE (RETROACTIVELY, IF
SIGNED LATER THAN THE EFFECTIVE DATE).	 		  	TO HAVE EFFECT AS OF THE EFFECTIVE DATE (RETROACTIVELY, IF
SIGNED LATER THAN THE EFFECTIVE DATE).

 EXHIBIT A 

FIELD, WORK PLAN, COMPENSATION 

Field: Protease Activated Biologics 
 Work Plan: 

Main contact for Consultant will be Sean McCarthy, CEO, until and unless the Company notifies Consultant in writing of a different main contact. 

Compensation: 
 Consultant will receive an option grant of
1,000,000 shares of common stock of the Company. Monthly vesting of this grant begins January 5, 2015 and is subject to the company’s standard 4-year term. 

Consultant will receive annual payments of $10,000 which will be payable as $2500 per quarter. This is intended to cover Scientific Advisory Board (SAB) and
Translational Advisory Board (TAB) meetings and other ad hoc discussions. 
 The Company shall reimburse consultant for reasonable out of pocket expenses
incurred during performance of the Services. 
 Any additional expenses incurred by Consultant that are charged to CytomX require Company’s advance
notice and written consent. 
 Consultant will invoice Company for such amounts no sooner than completion of the applicable task or event, and such invoices
shall be payable within fifteen (15) days after receipt by Company. 

 EXHIBIT B 

BACKGROUND TECHNOLOGY 

If no Background Technology then include the following: 
  

					
	“No background technology.	 	 /s/ HB
	  	initials Consultant
		 	  
	  	initials Company

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