Exhibit 4.3


 


AMENDMENT TO RIGHTS AGREEMENT


 


1.                                       General Background.  In
accordance with Section 27 of the Rights Agreement between Fleet Bank, N.A. f/k/a BankBoston, N.A. 
(the “Rights Agent”) and Cubist Pharmaceuticals, Inc.
(the “Company”) dated July 21, 1999 
(the “Agreement”), the Rights Agent and the Company desire to amend the
Agreement to appoint EquiServe Trust Company, N.A.


 


2.                                       Effectiveness.  This
Amendment shall be effective as of March 20, 2002 (the “Amendment”) and
all defined terms and definitions in the Agreement shall be the same in the
Amendment except as specifically revised by the Amendment.


 


3.                                       Revision.   The section in
the Agreement entitled “Change of Rights Agent” is hereby deleted in its
entirety and replaced with the following:


 


Change
of Rights Agent.  The
Rights Agent or any successor Rights Agent may resign and be discharged from
its duties under this Agreement upon 30 days’ notice in writing mailed to the
Company and to each transfer agent of the Common Shares or Preferred shares in
accordance with Section 27 hereof and to the holders of the Rights
Certificates by first-class mail.  The
Company may remove the Rights Agent or any successor Rights Agent upon 30 days’
notice in writing mailed to the Rights Agent or successor Rights Agent, as the
case may be, and to each transfer agent of the Common Shares or Preferred
Shares bin accordance with Section 27 hereof, and to the holders of the
Rights Certificates by first-class mail. 
If the Rights Agent shall resign or be removed or shall otherwise become
incapable of acting, the Company shall appoint a successor to the Rights
Agent.  If the Company shall fail to make
such appointment within a period of 30 days after giving notice of such removal
or after it has been notified in writing of such resignation or incapacity by
the resigning or incapacitated Rights Agent or by the holder of a Rights
Certificate (who shall, with such notice, submit such holder’s Rights
Certificate for inspection by the Company), then the registered holder of any Rights
Certificate may apply to any court of competent jurisdiction for the
appointment of a new Rights Agent.  Any
successor Rights Agent, whether appointed by the Company or by such a court,
shall be an entity organized and doing business under the laws of the United
States, in good standing, which is authorized under such laws to exercise
corporate trust or stock transfer powers and is subject to supervision or
examination by federal or state authority and which has individually or
combined with an affiliate at the time of its appointment as Rights Agent a
combined capital and surplus of at least $100 million dollars.  After appointment, the successor 


 





















 


Rights
Agent shall be vested with the same powers, rights, duties and responsibilities
as if it had been originally named as Rights Agent without further act or deed;
but the predecessor Rights Agent shall deliver and transfer to the successor
Rights Agent any property at the time held by it hereunder, and execute and
deliver any further assurance, conveyance, act or deed necessary for the
purpose.  Not later than the effective
date of any such appointment the Company shall file notice thereof in writing
with the predecessor Rights Agent and each transfer agent of the Common Shares
or Preferred Shares, and mail a notice thereof in writing to the registered
holders of the Rights Certificates. 
Failure to give any notice provided for in this Section 22,
however, or any defect therein, shall not affect the legality or validity of
the resignation or removal of the Rights Agent or the appointment of the
successor Rights Agent, as the case may be.


 


4.                                       Except
as amended hereby, the Agreement and all schedules or exhibits thereto shall
remain in full force and effect.


 


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IN
WITNESS WHEREOF, the parties hereto have caused this
Amendment to be executed in their names and on their behalf by and through
their duly authorized officers, as of this 20th day of March, 2002.


 


	
  Cubist Pharmaceuticals, Inc.

  	
  Fleet Bank, N.A. f/k/a
  Bank Boston, N.A.

  
	
   

  	
   

  	
   

  	
   

  
	
   

  	
   

  	
   

  	
   

  
	
  /s/ Christopher
  D.T. Guiffre

  	
   

  	
    /s/  Carol Mulvey-Eori

  	
   

  
	
  By: Christopher
  D.T. Guiffre

  	
  By:

  	
  Carol
  Mulvey-Eori

  	
   

  
	
  Title:

  	
  SVP, General
  Counsel

  and Secretary

  	
   

  	
  Title:  Managing Director,

  Client Administraton

  
	
   

  	
   

  	
   

  	
   

  
	
   

  	
   

  	
   

  	
   

  
	
   

  	
  EquiServe
  Trust Company N.A.

  
	
   

  	
   

  
	
   

  	
   

  
	
   

  	
    /s/  Carol Mulvey-Eori

  	
   

  
	
   

  	
  By:

  	
  Carol
  Mulvey-Eori

  
	
   

  	
  Title:

  	
  Managing
  Director
 Client Administration