Exhibit 4.2



|                                                     |  |              |  |                                                                                                                                     |  |       |  |  |  |                      |  | 
|---------------------------------------------------- |  | ------------ |  | ----------------------------------------------------------------------------------------------------------------------------------- |  | ----- |  |  |  | -------------------- |  | 
|                                                     |  | COMMON STOCK |  |                                                                                                                                     |  |       |  |  |  | COMMON STOCK         |  | 
|                                                     |  | Number ---   |  |                                                                                                                                     |  | CERUS |  |  |  | Shares ***0***       |  | 
|                                                     |  |             
|INCORPORATED UNDER THE LAWS
OF THE STATE OF DELAWARE |  |              |  | SEE REVERSE FOR CERTAIN DEFINITIONS AND A STATEMENT AS TO THE POWERS, DESIGNATIONS, PREFERENCES, RESTRICTIONS, AND RIGHTS OF SHARES
|                                                     |  |              |  |                                                                                                                                     |  |      
|                                                     |  |              |  |                                                                                                                                     |  |       |  |  |  | CUSIP  157085  10  1 |  | 



|                       |  |  |  |          |  | 
|---------------------- |  |  |  | -------- |  | 
|THIS CERTIFIES THAT    |  |  |  | SPECIMEN |  | 
|                       |  |  | 
|                       |  |  |  |          |  | 
|IS THE RECORD OWNER OF |  |  |  | ZERO     |  | 

FULLY PAID AND NON-ASSESSABLE SHARES OF COMMON SHARES, $0.001 PAR VALUE OF

----------------------CERUS CORPORATION----------------------

transferable on the books of the Corporation by the registered holder hereof in person or by duly authorized attorney upon surrender of this certificate properly endorsed. This certificate is not valid
unless countersigned by the Transfer Agent and registered by the Registrar.

In Witness Whereof the Corporation has caused this certificate to
be signed in facsimile by it authorized officers and its facsimile seal to be affixed.



|                 |  |  |  |                   |  |  |  |                        
|---------------- |  |  |  | ----------------- |  |  |  | -----------------------
|Dated            |  |  |  |                   |  |  |  |                        
|                 |  |  |  |                  
|/s/ Lori L. Roll |  |  |  | CERUS CORPORATION |  |  |  | /s/ Claes Glassell     
|Secretary        |  |  |  |                   |  |  |  | President and          
|                 |  |  |  | CORPORATE SEAL    |  |  |  | Chief Executive Officer
|                 |  |  |  |                   |  |  |  |                        



| |  |                                                      |  |                      |  | 
| |  | ---------------------------------------------------- |  | -------------------- |  | 
| |  | COUNTERSIGNED AND REGISTERED: WELLS FARGO BANK, N.A.
| | 
| |  | TRANSFER AGENT AND REGISTRAR,                       
| | 
| |  | VOID                                                
| |  | By                                                   |  |                      |  | 
| |  |                                                      |  | AUTHORIZED SIGNATURE |  | 



---

CERUS CORPORATION

The Corporation is authorized to issued Common Stock and Preferred Stock. The Board of Directors of the Company has the authority to fix the
number of shares and the designations of Preferred Stock and to determine or amend the preferences, privileges, and restrictions granted to or imposed upon any unissued shares of Preferred Stock.

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 so far as the same shall have been fixed, and
of the authority of the Board of Directors to designate and fix any preferences, rights and limitations of any wholly unissued series. 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:

|                                                                        |  |                                |  |                                            |  |                                          |  |         |  |        
|----------------------------------------------------------------------- |  | ------------------------------ |  | ------------------------------------------ |  | ---------------------------------------- |  | ------- |  | -------
|                                                                        |  |                                |  | UNIF GIFT MIN ACT 
 Custodian            
|TEN COM                                                                 |  | as tenants in common           |  |                                            |  | (Cust)                          
(Minor)
|                                                                        |  |                               
|TEN ENT                                                                 |  | as tenants by entireties       |  | under Uniform Gifts to Minors Act         
|                                                                        |  |                                |  |                                            |  |                                          |  |         |  | (State)
|JT TEN                                                                  |  | as joint tenants with right of |  | UNIF TRF MIN ACT   Custodian (until age )
|                                                                        |  | survivorship and not as        |  | (Cust)                                    
|                                                                        |  | tenants in common              |  | 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

PLEASE INSERT SOCIAL SECURITY OR OTHER

IDENTIFYING NUMBER OF ASSIGNEE



| |  | 
| |  | 
| | 
| |  | 









(PLEASE PRINT OR TYPEWRITE NAME AND ADDRESS OF ASSIGNEE)











| |  |       
| |  | ------
| |  | Shares



|                                                                                                             |  | 
|------------------------------------------------------------------------------------------------------------ |  | 
|of the capital 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.

Dated:



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| |  | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |  | 
| |  | X                                                                                                                                                                                                      |  | 
| |  |                                                                                                                                                                                                       
| |  | X                                                                                                                                                                                                      |  | 
| |  | NOTICE: THE SIGNATURE 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 WHATSOEVER.





|                        |  |                                                                                                                                                                                                                                                         
|----------------------- |  | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
|SIGNATURE(S) GUARANTEED |  |                                                                                                                                                                                                                                                         
|                        |  | 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 17Ad-15.



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|This certificate also evidences and entitles the holder hereof to certain rights as set forth
in a Rights Agreement between Cerus Corporation (the Company) and Wells Fargo Bank, N.A. (as successor to Wells Fargo Bank Minnesota, N.A., formerly known as Norwest Bank Minnesota, N.A.) as Rights Agent (the Rights Agent),
dated as of November 3, 1999 and amended as of August 6, 2001, as further amended from time to time (the Rights Agreement), the terms of which are herby incorporated herein by reference and a copy of which is on file at the
principal executive offices of the Company. Under certain circumstances, as set forth in the Rights Agreement, such Rights will be evidenced by separate certificates and will no longer be evidenced by this certificate. The Company will mail to the
holder of this certificate a copy of the Rights Agreement without charge after receipt of a written request therefor. As described in the Rights Agreement, Rights issued to any person who becomes an Acquiring Person or an Affiliate or Associate
thereof (as defined in the Rights Agreement) and certain related persons, whether currently held by or on behalf of such Person or by any subsequent holder, shall become null and void.

KEEP THIS CERTIFICATE IN A SAFE PLACE. IF IT IS LOST, STOLEN, OR DESTROYED, THE
CORPORATION MAY REQUIRE A BOND OF INDEMNITY AS A CONDITION TO THE ISSUANCE OF A REPLACEMENT CERTIFICATE