Cambridge, MA, December 6, 1999 - Therion Biologics Corporation today announced the appointment of Ronald J. Saldarini, Ph.D., to its Board of Directors. Dr. Saldarini, retired President, Wyeth-Lederle Vaccines and Pediatrics, brings to Therion over 30 years of experience in the pharmaceutical industry.

"We are fortunate to have attracted such a talented industry executive to our Board of Directors," said Dennis L. Panicali, Ph.D., President and Chief Executive Officer of Therion. "We have utilized our proprietary pox virus vector technology to develop and advance seven therapeutic cancer vaccine candidates and one AIDS vaccine candidate into multiple Phase I and II clinical studies. Ron's industry insight and his expertise in pharmaceutical and vaccine research, development and manufacturing will serve as a valuable resource as we advance our products into late-stage clinical trials."

Dr. Saldarini served as President of Wyeth-Lederle Vaccines and Pediatrics, a business unit of American Home Products Corporation (AHP), from 1995 until his retirement in 1999. At AHP, Dr. Saldarini was responsible for management of the Wyeth-Ayerst Laboratories Vaccines, U. S. Infant Nutritionals and Pediatric Pharmaceuticals business units. From 1969 until 1994, he held a variety of positions at American Cyanamid Company including President, Lederle-Praxis Biologicals Division. At American Cyanamid, Dr. Saldarini supervised the business operations and management of research and development activities for the Company's Lederle-Praxis division in the U.S. In addition, he managed the strategic direction of American Cyanamid's global vaccine and biological products business.

Dr. Saldarini has served as a member of several national committees, including the National Vaccine Advisory Committee and the National Advisory Commission on Childhood Vaccines. He is currently a member of the Boards of Trustees of the National Foundation of Infectious Diseases and the Infectious Disease Institute of New Jersey, the Board of Directors of the Institute for the Advanced Studies of Immunology and Aging, the Policy Board of the Albert B. Sabin Vaccine Foundation, and numerous other scientific councils and professional societies. Dr. Saldarini received his Ph.D. in physiology and biochemistry from the University of Kansas and completed an NIH postdoctoral fellowship at the Brain Research Institute of the UCLA School of Medicine.

Therion Biologics Corporation is engaged in the development of therapeutic vaccines for cancer and preventive vaccines for AIDS. Currently, Therion has seven products in Phase I and Phase II clinical development for the treatment of major cancers, including prostate, colorectal and breast cancer and melanoma. The Company also has a major corporate alliance with Pasteur M�rieux Connaught for the development of therapeutic colorectal cancer and melanoma vaccines. Therion is headquartered in Cambridge, Massachusetts.