METABASIS THERAPEUTICS, INC. ANNOUNCES PRICING OF INITIAL PUBLIC OFFERING

SAN DIEGO, CA - June 16, 2004 -- Metabasis Therapeutics, Inc. (Nasdaq: MBRX) announced today the pricing of its initial public offering of 5,000,000 shares of its common stock at a price to the public of $7.00 per share. All of the shares are being offered by Metabasis. In addition, Metabasis has granted to the underwriters a 30-day option to purchase up to an additional 750,000 shares to cover over-allotments, if any. Metabasis' common stock will be listed on the Nasdaq National Market under the symbol "MBRX."

The managing underwriters for the offering are SG Cowen & Co., LLC, acting as the sole book-runner for the offering, Deutsche Bank Securities, acting as co-lead manager, and Thomas Weisel Partners LLC and Legg Mason Wood Walker, Incorporated, acting as co-managers.

The offering of these securities is made only by means of a prospectus, copies of which may be obtained from SG Cowen & Co., LLC, Prospectus Department, 1221 Avenue of the Americas, 6th Floor, New York, NY 10020 or through ADP by fax at (631) 254-7268.

A registration statement relating to these securities was declared effective by the Securities and Exchange Commission on June 15, 2004. This press release shall not constitute an offer to sell or a solicitation of an offer to buy, nor shall there be any sale of these securities in any state or jurisdiction in which such an offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such state or jurisdiction.

About Metabasis:

Metabasis Therapeutics, Inc. (www.mbasis.com) is a biopharmaceutical company focused on the discovery, development and commercialization of novel small molecule drugs principally to treat metabolic diseases linked to pathways in the liver and to treat liver diseases. The company has established a broad product pipeline targeting large markets with significant unmet medical needs. Metabasis currently has three internally discovered product candidates in clinical trials indicated for the treatment of type 2 diabetes, hepatitis B and primary liver cancer.