METABASIS TO HOST CONFERENCE CALL AND LIVE WEBCAST TO DISCUSS SECOND QUARTER 2004 FINANCIAL RESULTS

SAN DIEGO, CA -July 27, 2004 - Metabasis Therapeutics (NASDAQ: MBRX), announced today the Company will host a conference call and live webcast on Thursday, August 12, 2004 at 4:30 p.m. Eastern (1:30 p.m. Pacific) to discuss financial results for the second quarter ended June 30, 2004. President and CEO of Metabasis, Dr. Paul Laikind will also provide an update on the Company's progress.

The conference call may be accessed by dialing 800-299-9630 for domestic callers and 617-786-2904 for international callers. Please specify to the operator that you would like to join the "Metabasis Second Quarter Financial Results Conference Call." The conference call will be webcast live on Metabasis' website at http://www.mbasis.com, under the Investor section, and will be archived there for 30 days following the call. Please connect to Metabasis' website several minutes prior to the start of the conference call to ensure adequate time for any software download that may be necessary.

About Metabasis
Metabasis Therapeutics, Inc. 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 has three internally discovered, novel product candidates in clinical development: CS-917, remofovir and MB07133, indicated for the treatment of type 2 diabetes, hepatitis B and primary liver cancer, respectively. All three products are being studied in patients and preliminary evidence of efficacy has been demonstrated with CS-917 and remofovir. Metabasis has developed several proprietary technologies for use in discovering and optimizing drugs, including the NuMimetic(TM) technology and the HepDirect technology. The NuMimetic technology was used to discover CS-917, a first-in-class gluconeogenesis inhibitor, and was also used to identify MB07803, a 2nd generation gluconeogenesis inhibitor that is expected to enter the clinic in 2005 for the treatment of type 2 diabetes. The HepDirect technology, a liver-targeted prodrug technology, was used to develop remofovir and MB07133 and is also being used in a partnership with Merck to discover new treatments for hepatitis C. Metabasis is continuing to identify and develop new product candidates using its proprietary technologies and know-how.

Forward-Looking Statement
Statements in this press release that are not strictly historical in nature constitute "forward-looking statements." Such statements include, but are not limited to, statements about Metabasis' product candidates, proprietary technologies and research programs. Such forward-looking statements involve known and unknown risks, uncertainties and other factors which may cause Metabasis' actual results to be materially different from historical results or from any results expressed or implied by such forward-looking statements. These factors include, but are not limited to, risks and uncertainties related to the progress and timing of clinical trials for Metabasis' product candidates; difficulties or delays in development, testing, obtaining regulatory approval, producing and marketing Metabasis' product candidates; adverse side effects or inadequate therapeutic efficacy of Metabasis' product candidates or proprietary technologies; Metabasis' dependence on collaborative partners; the scope and validity of intellectual property protection for Metabasis' product candidates, proprietary technologies and their uses; competition from other pharmaceutical or biotechnology companies; Metabasis' ability to obtain additional financing to support its operations; and other factors discussed in the "Risk Factors" section of Metabasis' prospectus filed with the Securities and Exchange Commission pursuant to Rule 424(b)(4) of the Securities Act on June 16, 2004. All forward-looking statements are qualified in their entirety by this cautionary statement. Metabasis is providing this information as of this date of this release and does not undertake any obligation to update any forward-looking statements contained in this release as a result of new information, future events or otherwise.