Exhibit 10.3

FIRST AMENDMENT

TO MASTER SERVICES AGREEMENT

THIS FIRST AMENDMENT (First Amendment), effective as of the last date written below (the Amendment
Effective Date), is to the Master Services Agreement between Sunesis Pharmaceuticals, Inc. (Sunesis) and Aptuit, Inc. (as assignee of Quintiles, Inc., hereinafter referred to as Aptuit) dated August 26, 2004 (the
Agreement). Unless otherwise defined below, all capitalized terms herein shall have the same meaning as set forth in the Agreement.

WHEREAS, the parties hereto desire to modify the Agreement to provide the terms and conditions upon which Sunesis may continue to engage Aptuit from time-to-time to provide services in support of
Sunesis development chemistry projects.

THEREFORE, in consideration of the promises and mutual
covenants contained in this First Amendment, the parties hereto agree to the terms and conditions set forth below.



| | 1. | All mention of Quintiles, Inc. in the Agreement shall be replaced with Aptuit, Inc.
| | -- | -----------------------------------------------------------------------------------



| | 2. | Section 3.0 of the Agreement shall be deleted and replaced in its entirety with:
| | -- | --------------------------------------------------------------------------------

Term. This Agreement shall commence as of August 26, 2004 and shall continue through December 31, 2011,
unless otherwise earlier terminated by either party in accordance with Section 15.0 below.



| | 3. | The addresses set forth under Section 19.0 of the Agreement shall be modified to read as follows:
| | -- | -------------------------------------------------------------------------------------------------



|                                                                                               |  |                                                                                                                                          
|---------------------------------------------------------------------------------------------- |  | -----------------------------------------------------------------------------------------------------------------------------------------
|If to Aptuit: Aptuit,
Inc. Contract Negotiations 10245
Hickman Mills Dr. Kansas City, MO 64137 |  | If to Sponsor: Sunesis
Pharmaceuticals, Inc. 395 Oyster Point Boulevard, Suite 400 South San Francisco, CA 94080 Attn:    General
Counsel

Except as otherwise stated in this First Amendment, all other terms and conditions
of the Agreement shall remain in full force and effect.

IN WITNESS WHEREOF, the parties hereto have caused
this First Amendment to be executed on the dates set forth below.



|                              |  |  |  |              |  |  |  | 
|----------------------------- |  |  |  | ------------ |  |  |  | 
|SUNESIS PHARMACEUTICALS, INC. |  |  |  | APTUIT, INC.

|    |  |                       |  |  |  |     |  |                 
|--- |  | --------------------- |  |  |  | --- |  | ----------------
|    |  |                       |  | 
|By: |  | /s/ Steven B. Ketchum |  |  |  | By: |  | /s/ Karen Rhyner

|            |  |                   |  |  |  |             |  |             
|----------- |  | ----------------- |  |  |  | ----------- |  | ------------
|Print Name: |  | Steven B. Ketchum |  |  |  | Print Name: |  | Karen Rhyner

|       |  |             |  |  |  |        |  |                
|------ |  | ----------- |  |  |  | ------ |  | ---------------
|Title: |  | Sr. VP, R&D |  |  |  | Title: |  | Senior Director

|             |  |                |  |  |  |              |  |              
|------------ |  | -------------- |  |  |  | ------------ |  | -------------
|Date Signed: |  | August 1, 2008 |  |  |  | Date Signed: |  | 18, July 2008