QuickLinks
 -- Click here to rapidly navigate through this document

 
 

Exhibit 4.1    
    


        COMMON STOCK  



	Number	 	 	 	Shares
	
SIRTRIS PHARMACEUTICALS, INC.
	
  INCORPORATED UNDER THE LAWS

OF THE STATE OF DELAWARE
	
 	
 	

 	
 	

CUSIP 82968A 105

SEE REVERSE SIDE FOR CERTAIN DEFINITIONS





THIS CERTIFIES THAT 


IS
THE OWNER OF 


FULLY-PAID AND NON-ASSESSABLE SHARES OF THE COMMON STOCK, PAR VALUE OF $0.001 PER SHARE OF SIRTRIS PHARMACEUTICALS, INC.
transferable on the books of the Company by the holder hereof, in person, or by duly authorized attorney upon surrender of this Certificate properly endorsed. The shares represented by this
Certificate are subject to the provisions of the certificate of incorporation and by-laws of the Company as from time to time amended or restated. This Certificate is not valid until
countersigned by the Transfer Agent and registered by the Registrar. 


Witness
the facsimile signatures of its duly authorized officers. 



	
 CHAIRMAN OR VICE CHAIRMAN

OR PRESIDENT OR VICE PRESIDENT	
 	

SECRETARY OR ASSISTANT SECRETARY

OR TREASURER OR ASSISTANT TREASURER
	
 Countersigned and Registered:	
 	

 
	
COMPUTERSHARE TRUST COMPANY, N.A.	
 	

 





	

By:	
 	

 	
 	

 
	 	 	
 Transfer Agent and Registrar

Authorized Signature	 	 
	










SIRTRIS PHARMACEUTICALS, INC.  


THE
RECORD HOLDER OF THIS CERTIFICATE MAY OBTAIN FROM THE SECRETARY OF THE COMPANY, UPON REQUEST AND WITHOUT CHARGE, A FULL STATEMENT OF THE DESIGNATION, RELATIVE RIGHTS, PREFERENCES AND LIMITATIONS
OF THE SHARES OF EACH CLASS AUTHORIZED TO BE ISSUED AND THE DESIGNATION, RELATIVE RIGHTS, PREFERENCES AND LIMITATIONS OF EACH SERIES OF PREFERRED SHARES AUTHORIZED TO BE ISSUED SO FAR AS THE SAME HAVE
BEEN FIXED AND THE AUTHORITY OF THE BOARD OF DIRECTORS TO DESIGNATE AND FIX THE RELATIVE RIGHTS, PREFERENCES AND LIMITATIONS OF OTHER SERIES. 


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

TEN ENT — as tenants by the entireties	 	UNIF GIFT MIN ACT —	 	 	 	 
	JT TEN — as joint tenants with right of survivorship and not as tenants in common	 	 	 	
 (Custodian)	Custodian	
 (Minor)





	 	 	Under Uniform Gifts 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, INCLUDING ZIP CODE OF ASSIGNEE)





	


	


	


	

	
 	

shares
	
 of the 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 Company with full power of substitution in the premises. 



	Dated	 	 	 	X	 
	 	 	
	 	 	

	
 	
 	

 	
 	

X	

 
	 	 	 	 	 	 	

	 	 	 	 	 	NOTICE: THE SIGNATURE ON THIS ASSIGNMENT MUST CORRESPOND EXACTLY WITH THE NAME WRITTEN UPON THE FACE OF THE CERTIFICATE.
	 Signature(s) Guaranteed:	 	 	 
	

 THE SIGNATURE(S) SHOULD BE GUARANTEED BY AN ELIGIBLE GUARANTOR INSTITUTION, AS DEFINED IN RULE 17AD-15 UNDER THE SECURITIES AND EXCHANGE ACT OF 1934, AS AMENDED	
 	

 	

 





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











QuickLinks



Exhibit 4.1