September 23, 2008

Metabasis Therapeutics Announces Initiation of a Clinical Trial for MB07803, Its Novel Product Candidate for the Treatment of Type 2 Diabetes

Metabasis Therapeutics, Inc. (Nasdaq: MBRX) announced today that it has initiated a clinical trial to evaluate higher doses of MB07803 in patients. MB07803 is Metabasis' second-generation FBPase inhibitor product candidate for the treatment of type 2 diabetes. The trial is expected to enroll at least 40 patients.

A major milestone was achieved earlier this year with the completion of the Phase 2a, 28-day proof-of-concept trial for MB07803. This clinical trial provided promising results supporting the potential of MB07803 as an important new approach for treating patients with type 2 diabetes. MB07803 was shown to be safe and well tolerated at the doses tested in this trial and met its primary efficacy endpoint with results demonstrating a statistically and clinically significant reduction in fasting plasma glucose at day 28. In the current clinical trial, the Company is continuing to study higher doses of MB07803 so that the maximal efficacious dose can ultimately be determined.

"We were very encouraged by the results observed in the recently completed Phase 2a clinical trial," commented Dr. Mark Erion, executive vice president of research and development and chief scientific officer. "While we were pleased with the glucose lowering results observed at the highest dose tested, there exists a strong likelihood that even greater efficacy is possible based on our knowledge of the target. Consequently, given the promising safety profile even at the top dose, we decided to conduct a small clinical trial in patients to evaluate higher doses of MB07803. We expect to use the results of this trial to help select the dose range suitable for evaluation in future trials."

An oral presentation summarizing the results from the Phase 2a clinical trial for MB07803 will be given at the World Congress on Controversies to Consensus in Diabetes, Obesity and Hypertension to be held in Barcelona, Spain, October 30 - November 2, 2008. Dr. Alan J. Garber, a principal investigator in the Phase 2a clinical trial, will give the presentation. Dr. Garber is considered to be an expert in the field of diabetes and its complications and has been intimately involved in clinical research throughout his career, notably with metformin and more recently with Galvus, a DPP-IV inhibitor.

Dr. Paul Laikind, president and chief executive officer, said, "The safety and efficacy results we have seen thus far with MB07803 are encouraging and support our belief that a direct inhibitor of the pathway responsible for the over-production of glucose in patients suffering with diabetes could be an important new therapeutic approach. We have been especially interested in its potential use as an effective new alternative for the millions of patients who are unable to take the current first-line therapy, metformin. Alone or in combination with other diabetes therapies, we believe that MB07803 could eventually prove uniquely beneficial to this underserved population."

About Metabasis (

Metabasis is a biopharmaceutical company using its proprietary technologies, scientific expertise and unique capabilities for targeting the liver and liver pathways to develop novel therapies to treat metabolic and other diseases. The Company has established a broad pipeline of product candidates and advanced research programs targeting large markets with significant unmet needs. Metabasis' core area of focus is on the discovery and development of drug candidates to treat metabolic diseases such as hyperlipidemia and diabetes, among others. Although not a core focus of the Company, Metabasis has also discovered and developed drug candidates indicated for the treatment of liver diseases such as hepatitis and primary liver cancer, which it now intends to license or partner. All product candidates were developed internally using proprietary technologies.

Forward-Looking Statements:

Statements in this press release that are not strictly historical in nature constitute "forward-looking statements." Such statements include, but are not limited to, references to; the initiation, progress, completion and results of clinical trials for MB07803, as well as the potential use of, and market for, MB07803. 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 development for Metabasis' product candidates; the fact that positive results obtained during early development do not necessarily mean later development will succeed; difficulties or delays in development, testing, obtaining regulatory approval, producing and marketing Metabasis' product candidates; serious adverse side effects or inadequate efficacy of, or serious adverse events related to, Metabasis' product candidates or proprietary technologies; the risk that Metabasis will not be able to build more value or retain rights for direct commercialization of its product candidates; Metabasis' dependence on its licensees and collaborators for the development and registration of, as well as information relating to, certain of its product candidates; potential conflicts with collaborators that could delay or prevent the development or commercialization of Metabasis' product candidates; 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' Quarterly Report on Form 10-Q for the three months ended June 30, 2008 and in Metabasis' other filings with the Securities and Exchange Commission. All forward-looking statements are qualified in their entirety by this cautionary statement. Metabasis is providing this information as of the 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.