Contacts:
Christopher Taylor                                     Douglas MacDougall
Director of Investor Relations                         Vice President
Genome Therapeutics Corp.                              Feinstein Kean Healthcare
781.398.2466                                           617.577.8110

FOR IMMEDIATE RELEASE

              GENOME THERAPEUTICS CANCELS FOLLOW-ON PUBLIC OFFERING

WALTHAM, MASS., APRIL 13, 2000 -- Genome Therapeutics Corp. (Nasdaq: GENE)
announced that in light of recent market volatility and current market
conditions, the Company would not proceed with its proposed follow-on public
offering at this time. Genome Therapeutics will file an amendment to the
registration statement that it filed with the Securities and Exchange Commission
on March 16, 2000 to convert it to a shelf registration statement.

Genome Therapeutics (WWW.GENOMECORP.COM) is a leader in the commercialization of
genomics-based drug discovery. The Company's gene discovery strategy is to
identify and characterize human genes associated with major diseases and
elucidate microbial genes as novel drug targets against many serious infectious
organisms. Together with its strategic partners, including Schering-Plough,
AstraZeneca, Wyeth-Ayerst and bioMerieux, Genome Therapeutics is using genomic
information to develop a new generation of genomics-based pharmaceutical,
vaccine and diagnostic products.

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