Exhibit 4.3


 


[FACE
OF CERTIFICATE]


 


[LOGO]


INCORPORATED
UNDER THE LAWS OF THE STATE OF DELAWARE


 


	
  NUMBER

  	
  SHARES

  	
   

  
	
  PP

  	
   

  	
   

  
	
   

  	
   

  	
   

  
	
  COMMON STOCK

  	
   

  	
   

  
	
  PAR VALUE $.01 PER SHARE

  	
  SEE
  REVERSE FOR CERTAIN DEFINITIONS

  	
   

  
	
   

  	
   

  	
   

  
	
  This Certifies That

  	
  CUSIP
  739421 40 2

  	
   

  



 


 


is
the owner of


 


FULLY
PAID AND NONASSESSABLE SHARES OF THE COMMON STOCK OF


PRAECIS
PHARMACEUTICALS INCORPORATED


 


(hereinafter
called the “Corporation”) transferable on the books of the Corporation by said
owner in person or by duly authorized attorney, upon surrender of this
certificate properly endorsed. The Corporation will 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 or series thereof and the qualifications, limitations or
restrictions of such preferences and/or rights. This certificate and the shares
represented hereby are issued and shall be held subject to all the provisions
of the Certificate of Incorporation and all amendments thereto, copies of which
are on file at the office of the Transfer Agent, and the holder hereof, by
acceptance of this certificate, consents to and agrees to be bound by all of
said provisions. This certificate is not valid unless countersigned and
registered by the Transfer Agent and Registrar.


 


Witness, the facsimile seal of
the Corporation and by facsimile the signatures of its duly authorized
officers.


 


Dated:


 


	
  /s/ Kevin F. McLaughlin

  	
   

  	
  /s/ Edward C. English

  	
   

  
	
  PRESIDENT

  	
  TREASURER

  
	
   

  	
   

  
	
  [SEAL]

  



 


Countersigned and Registered:


AMERICAN STOCK TRANSFER & TRUST
COMPANY


(NEW YORK, NEW YORK)


Transfer Agent and Registrar


By:


Authorized Signature


 





















 


[REVERSE
OF CERTIFICATE]


 


PRAECIS
PHARMACEUTICALS INCORPORATED


 


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


JT TEN - as joint tenants with right of
survivorship and not as tenants in common


 


UNIF GIFT MIN ACT -         
(Cust)         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 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 in the premises.


 


Dated


 


 


NOTICE:


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


 


	
  SIGNATURE(S) GUARANTEED:

  	
   

  	
   

  
	
  THE SIGNATURE(S) MUST 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.

  



 


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


 


This certificate also evidences and
entitles the holder hereof to certain Rights as set forth in the Rights
Agreement between PRAECIS PHARMACEUTICALS INCORPORATED (the “Company”) and the
Rights Agent thereunder (the “Rights Agreement”), the terms of which are hereby
incorporated herein by reference and a copy of which is on file at the
principal 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, as in effect on
the date of mailing, without charge, promptly after receipt of a written
request therefor. Under certain circumstances set forth in the Rights
Agreement, Rights issued to, or held by, any Person who is, was or becomes an
Acquiring Person or any Affiliate or Associate thereof (as such terms are
defined in the Rights Agreement), whether currently held by or on behalf of
such Person or by any subsequent holder, may become null and void.