POWER OF ATTORNEY
      I hereby constitute and appoint each of Manny Bougoulas and Edy Mahoney, 
signing singly, my true and lawful attorney-in-fact to:

(1) execute for and on my behalf, in my capacity as an officer and/or director 
of Genome Therapeutics Corporation (the "Company"), Forms 3, 4 and 5 in 
accordance with Section 16(a) of the Securities Exchange Act of 1934 and the 
rules thereunder;

(2) do and perform any and all acts for and on my behalf that may be necessary 
or desirable to complete and execute any such Form 3, 4 or 5 and timely file 
such form with the United States Securities and Exchange Commission and any 
stock exchange or similar authority; and

(3) take any other action of any type whatsoever in connection with the 
foregoing which, in the opinion of such attorney-in-fact, may be to my benefit, 
in my best interest, or that I am legally required to do, it being understood 
that the documents executed by such attorney-in-fact's discretion.

      I hereby grant to each such attorney-in-fact full power and authority to 
do and perform any and every act and thing whatsoever requisite, necessary, or 
proper to be done in the exercise of any of the rights and powers herein 
granted, as fully to all intents and purposes as I might or could do if 
personally present, with full power of substitution or revocation, hereby 
ratifying and confirming all that such attorney-in-fact, or such attorney-in-
fact's substitute or substitutes, shall lawfully do or cause to be done by 
virtue of this power of attorney and the rights and powers herein granted.  I 
acknowledge that the attorneys-in-fact, in serving in such capacity at my 
request, are not assuming, nor is the Company assuming, any of my 
responsibilities to comply with Section 16 of the Securities Exchange Act of 
1934.

        This Power of Attorney shall remain in full force and effect until I am no 
longer required to file Forms 3, 4 and 5 with respect to my holdings of and 
transactions in Company securities, unless I earlier revoke it in a signed 
writing delivered to the attorneys-in-fact.

        IN WITNESS WHEREOF, I have caused this Power of Attorney to be executed as 
of this 3rd day of February 2004.
                                                        /s/ Vernon R. Loucks 
                                                        __________________
                                                        Vernon R. Loucks
                                                Director, Genome Therapeutics Corp.