Cambridge, MA, June 28, 1999 - Therion Biologics Corporation announced today that it has completed a $10.5 million equity financing. Proceeds will be used to accelerate development of its seven therapeutic cancer vaccines currently in Phase I and Phase II clinical trials and to advance additional vaccines into human testing.

New investors included lead investor Sofinov, a subsidiary of the Caisse de d�p�t et placement du Qu�bec in Montreal; Pacific Horizon Ventures of Seattle, Washington; and BioVentures Investors of Worcester, Massachusetts. Also participating were the Company's major existing shareholders: SR One Limited, H&Q; Healthcare Investors, H&Q; Life Science Investors, Loeb Investors, Venture Capital Fund of America, Northwood Ventures, New York Life Insurance Company, Singapore Bio-Innovations and Sidney R. Knafel. Hambrecht & Quist LLC acted as Therion's financial advisor and placement agent for the financing. In conjunction with the financing, Trudie Resch, Manager of Sofinov, was appointed to Therion's Board of Directors.

"Cancer vaccines have emerged as one of the most promising new areas of cancer therapy. Therion has established itself as a leader in this field," said Denis Dionne, President of Sofinov. "Therion has built a rich product pipeline and demonstrated an ability to rapidly and cost-effectively move new products into the clinic. This investment in Therion is part of Sofinov's strategy to fund innovative and cutting-edge biotechnology and information technology companies."

"The success of this financing reflects the notable clinical and commercial progress we have made over the last 18 months," said Dennis L. Panicali, Ph.D., President and Chief Executive Officer of Therion. "Our first two products, for prostate and colorectal cancer, entered Phase II clinical studies, we expanded our Phase I programs with additional protocols, and we entered our first corporate alliance, with Pasteur M�rieux Connaught. We are poised to enter the clinic with a number of new vaccines in the coming months."

Therion's approach is based on combining live recombinant pox virus vectors with tumor-specific antigens, co-stimulatory molecules, and immune-modulating proteins, the molecular components necessary to stimulate a potent and specific immune response against cancer cells. Therion has developed these proprietary immunotherapy products as part of two Cooperative Research and Development Agreements (CRADAs) with leading researchers at the National Cancer Institute (NCI). In addition, the Company is developing preventive vaccines for AIDS in a program supported by the National Institute of Allergy and Infectious Disease (NIAID).

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 and colorectal 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.