Exhibit 4.2

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SUNESIS PHARMACEUTICALS, INC.

The Corporation shall furnish without charge to each stockholder who so requests a statement of the powers, designations, preferences and
relative, participating, optional or other special rights of each class of stock of the Corporation or series thereof and the qualifications, limitations or restrictions of such preferences and/or rights. Such requests shall be made to the
Corporations Secretary at the principal office of the Corporation.

The following abbreviations, when used in the
inscription on the face of this certificate, shall be construed as though they were written out in full according to applicable laws or regulations:



|               |  |                                            |  |  |  |                     |  |                                       
|-------------- |  | ------------------------------------------ |  |  |  | ------------------- |  | --------------------------------------
|TEN COM       |  | as tenants in common                       |  |  |  | UNIF GIFT MIN ACT  |  | __________ Custodian __________       
|TEN ENT       |  | as tenants by the entireties               |  |  |  |                     |  | (Cust)
                        (Minor)
|JT TEN        |  | as joint tenants with right of             |  |  |  |                     |  | under Uniform Gifts to Minors         
|               |  | survivorship and not as tenants Act common |  |  |  |                     |  | Act ___________________________       
|               |  |                                            |  |  |  | UNIF TRF MIN ACT   |  | _______ Custodian (until Age ______   
|               |  |                                            |  |  |  |                     |  | (Cust)                                
|               |  |                                            |  |  |  |                     |  | __________ under Uniform Transfers    
|               |  |                                            |  |  |  |                     |  | (Minor)                               
|               |  |                                            |  |  |  |                     |  | to Minors Act ___________________     
|               |  |                                            |  |  |  |                     |  | (State)                               

Additional
abbreviations may also be used though not in the above list.

FOR VALUE
RECEIVED, hereby sell, assign and transfer unto



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|PLEASE INSERT SOCIAL SECURITY OR OTHER IDENTIFYING NUMBER OF ASSIGNEE |  |  |  | 
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(PLEASE PRINT OR TYPEWRITE NAME AND ADDRESS. INCLUDING ZIP CODE, OF ASSIGNEE)









Shares

of the common stock represented by the within Certificate, and do
hereby irrevocably constitute and appoint

Attorney

to transfer the said stock on the books of the within named
Corporation with full power of substitution in the premises.

Dated __________________________________



XXNOTICE

THE SIGNATURE (S) TO THIS ASSIGNMENT MUST CORRESPOND WITH THE NAME(S) AS WRITTEN UPON THE FACE OF THE CERTIFICATE IN EVERY PARTICULAR, WITHOUT ALTERATION OR ENLARGEMENT OR ANY
CHANGE WHATEVER


Signature(s) Guaranteed

By _________________________________________________________

THE SIGNATURE(s) SHOULD BE
GUARANTEED BY AN ELIGIBLE GUARANTOR

INSTITUTION BANKS. STOCKBROKERS, SAVINGS AND LOAN ASSOCIATIONS

AND CREDIT UNIONS WITH MEMBERSHIP IN AN APPROVED SIGNATURE

GUARANTEE MEDALLION PROGRAM, PURSUANT TO S.E.C. RULE I7Ad-15