METABASIS THERAPEUTICS, INC. ANNOUNCES THAT DR. SCOTT HECKER HAS JOINED AS EXECUTIVE DIRECTOR OF CHEMISTRY

SAN DIEGO, CA - October 7, 2003 -- Metabasis Therapeutics, Inc. today announced that Scott Hecker, Ph.D. has joined the company as Executive Director of Chemistry. Dr. Hecker will be responsible for both medicinal chemistry and chemical development. Prior to joining Metabasis, Dr. Hecker was Vice President of Chemistry for Essential Therapeutics, Inc. (formerly known as Microcide Pharmaceuticals, Inc.). Dr. Hecker comes to Metabasis with extensive drug discovery experience obtained from his nine years at Essential Therapeutics and eight years at Pfizer. Dr. Hecker received his Ph.D. from University of California, Berkeley in 1985.

Dr. Mark Erion, Executive Vice President of Research and Development at Metabasis said, "Dr. Hecker is an important addition to our R&D team. His experience will be valuable in our efforts to find novel drugs for treating liver diseases and metabolic diseases linked to pathways in the liver. Chemistry continues to be an important component of Metabasis' R&D efforts and therefore the addition of Dr. Hecker is expected to help us meet our company goal of recommending one new compound per year for pre-clinical development."

Metabasis Therapeutics, Inc. (www.mbasis.com) is a privately held, biopharmaceutical company that develops proprietary products principally for the treatment of liver and liver-related metabolic diseases. Metabasis has expertise in the fields of nucleoside/nucleotide chemistry and metabolism, liver biology and liver-specific drug delivery. Metabasis has discovered and developed a new class of drug candidates for treating diabetes that act to lower liver glucose production in diabetic patients. The first drug candidate from this program, CS-917, is being developed in collaboration with Sankyo Co., Ltd. and is currently undergoing clinical testing. Metabasis has also developed its HepDirect technology that allows liver-specific delivery of new and existing drugs. Two novel drug candidates derived from the HepDirect technology are in clinical testing: a drug for hepatitis B called Hepavir B, developed in collaboration with Ribapharm, Inc., and a drug for primary liver cancer called MB7133, to which Metabasis retains exclusive rights.