METABASIS THERAPEUTICS, INC. ANNOUNCES THAT DR. DAVID HERZIG HAS JOINED AS A MEMBER OF THE BOARD

SAN DIEGO, CA December 7, 1999 -- Metabasis Therapeutics, Inc. today announced that David Herzig, Ph.D. has joined the company's Board of Directors, effective immediately. Dr. Herzig recently retired from Parke-Davis Pharmaceutical Research, a division of the Warner-Lambert Company, where he was Vice President, Drug Development and Scientific Development. As Vice President he had responsibility for acquisition, development and registration of the diabetes drug Rezulin (Troglitazone) which was successfully launched in 1997. Dr. Herzig worked in the Scientific Development department at Parke Davis for over twenty years. He was responsible for identification, evaluation and acquisition of external technology and drugs from both large pharmaceutical and biotechnology companies. Before joining Warner-Lambert Research Institute in 1968, Dr. Herzig conducted research at the New York University School of Medicine and at the National Institutes of Health.

Dr. Paul Laikind, Chairman, President and CEO of Metabasis stated, "Dr. Herzig is a welcome addition to our Board. His many years of drug development experience and his recent work with the successful diabetes drug Rezulin will have a very positive impact on our near-term development efforts. We are developing an exciting, new diabetes drug that targets liver glucose production. This drug is expected to enter the clinic next year. In addition, David's long experience with licensing and strategic partnering and the many contacts he has made over the years will help Metabasis form new strategic alliances that will allow us to accelerate development of our products and further build our business. We are currently seeking partners for our new platform technology for targeting drugs to the liver, I am sure with David's help, we will accelerate that process"

Metabasis Therapeutics, Inc. is a privately held, biopharmaceutical company that develops proprietary products for the treatment of human disease with a focus on diseases that involve the liver. The Company is a leader in the field of nucleoside/nucleotide metabolism and chemistry and has proprietary expertise in liver biology and organ-specific drug delivery. Metabasis, in collaboration with Sankyo, is developing novel drugs to treat Type II diabetes that act by lowering liver glucose production. Metabasis has also developed a platform technology that allows liver-specific delivery of new and existing drugs. Metabasis' patent portfolio includes over 21 issued patents in its fields of study. The Company occupies state-of-the-art research facilities in San Diego, California.