METABASIS THERAPEUTICS, INC. ANNOUNCES THAT DR. BILL FORBES HAS JOINED AS VICE PRESIDENT OF CLINICAL DEVELOPMENT AND REGULATORY AFFAIRS

SAN DIEGO, CA - August 7, 2002 -- Metabasis Therapeutics, Inc. today announced that Dr. Bill Forbes has joined the company to lead its clinical development efforts. Dr. Forbes will be responsible for all clinical development and regulatory activity surrounding Metabasis' growing pipeline of products for liver and liver-related disease. Metabasis currently has one product in the clinic with a second expected to enter this quarter and a third expected in the first quarter of 2003.

Dr. Forbes came to Metabasis from Otsuka America Pharmaceuticals, Inc. where he was Group Leader for development of therapeutic products and oversaw the development of eight new chemical entities in a variety of indications. Prior to Otsuka he worked as part of the clinical research team at Glaxo, Inc. Dr. Forbes received his Doctor of Pharmacy degree from Creighton University in Omaha, Nebraska and conducted post-doctoral work at Creighton Cardiac Center where he participated in over 25 pharmaceutical sponsored clinical research studies and served as an instructor at the School of Medicine.

Dr. Mark Erion, Executive Vice President of Research and Development at Metabasis said, "At Otsuka, Dr. Forbes was responsible for numerous clinical development programs involving evaluation of novel drugs in all phases of development. Most impressive was his ground-breaking efforts on a PDE-3 inhibitor for peripheral arterial disease (PAD) named Pletal (Cilostazol). He was given responsibility for this drug at the beginning of Phase 2 and took the drug all the way through NDA approval. Pletal received an expedited review by the FDA and was approved in 1999. Pletal represents only the second drug to reach the market for treating PAD. Dr. Forbes' experience in designing and implementing innovative clinical development programs will be put to good use at Metabasis."

Dr. Paul Laikind, Chairman, President and CEO of Metabasis stated, "Dr. Forbes is a welcome addition to our management team at a critical and exciting time for Metabasis. Our first two products, CS-917 (MB6322), a novel drug for the treatment of diabetes and Hepavir B, a HepDirect™ antiviral for treating Hepatitis B are making excellent progress with CS-917 in the clinic and Hepavir B expected to begin clinical trials this quarter. These two products are being developed with our partners, Sankyo Co., Ltd. and Ribapharm Inc., respectively. In contrast, we are developing our third product, MB7133, a HepDirect oncolytic for primary liver cancer, on our own. With Dr. Forbes' help and guidance we expect to file an IND for MB7133 this year and start clinical trials during the first quarter of 2003. At that point we will have three exciting, liver-related products at various stages of clinical development as well as other earlier stage products in the preclinical pipeline."

Metabasis Therapeutics, Inc. (http://www.mbasis.com) is a privately-held, biopharmaceutical company that develops proprietary products for the treatment of human disease with a current focus on liver or liver-related diseases. The Company employs various resources for discovering and perfecting new products, is a leader in the field of nucleoside/nucleotide chemistry and metabolism, and has proprietary expertise in liver biology and liver-specific drug delivery. Metabasis has discovered and developed a new class of drugs for treating diabetes that act to lower liver glucose production in diabetic patients. The first drug from this program is being developed in collaboration with Sankyo Co., Ltd. and is currently undergoing clinical testing. The Company has also developed the HepDirect™ Prodrug Technology that allows liver-specific delivery of new and existing drugs. Two drugs derived from the HepDirect Technology are in development, a drug for hepatitis B called Hepavir B and a drug for primary liver cancer called MB7133. Hepavir B is the subject of a partnership with Ribapharm, Inc. and is expected to begin clinical trials during the third quarter of 2002. The drug for primary liver cancer is expected to enter the clinic during the first quarter of 2003. The Company has approximately 75 employees and occupies state-of-the-art research facilities in San Diego, California.