Cambridge, MA, July 31, 1997 - Therion Biologics Corporation announced today that Francis P. Tally, M.D., Vice President of Drug Development and Medical Affairs at Cubist Pharmaceuticals, has been appointed to its Board of Directors. Dr. Tally brings to Therion more than 24 years of experience in academia and the pharmaceutical industry. He becomes the fifth member of Therion's Board.

"Dr. Tally's breadth of pharmaceutical expertise, which spans clinical development and drug discovery, will augment the current strengths of our Board," said Dennis L. Panicali, Ph.D., President and Chief Executive Officer of Therion Biologics. "His guidance will be particularly valuable as we advance the development of our therapeutic cancer vaccines and our preventive AIDS vaccines."

Prior to joining Cubist, Dr. Tally served at Lederle Laboratories of American Cyanamid/American Home Products as Executive Director of Infectious Disease, Molecular Biology and Natural Products Research. At Lederle, Dr. Tally was responsible for worldwide clinical studies for piperacillin/tazobactam (Zosyn�), directed discovery research in infectious disease, and was responsible for developing two new classes of antibiotics. Previously, he was Senior Pathologist and Senior Physician at New England Medical Center, and Associate Professor of Pathology and Medicine at Tufts University School of Medicine. Dr. Tally received his A.B. in Biology from Providence College, and his M.D. from George Washington University School of Medicine.

Therion Biologics Corporation is engaged in the development of immunotherapeutic products and vaccines for the treatment of major cancers and the prevention of AIDS. Therion is headquartered in Cambridge, Massachusetts.