Cambridge, MA, and New York, NY, September 16, 1998 - Therion Biologics Corporation has acquired from the Ludwig Institute for Cancer Research rights to NY-ESO-1, a novel antigen expressed in a number of major tumor types such as breast, bladder and lung cancer, the organizations announced today. Therion has exclusively optioned the ESO-1 gene for use in the Company's proprietary pox virus vectors to create immunotherapeutic products for a broad range of malignancies.

"This collaboration provides a pathway to rapidly evaluate the potential benefits of ESO-1 immunotherapy in cancer patients," said Lloyd Old, M.D., Director of the Ludwig Institute for Cancer Research. "ESO-1 is recognized by the cellular and humoral immune systems of cancer patients, and cytotoxic T-cells that lyse ESO-1 expressing cancer cells have been isolated. Therion's pox virus vectors will enable delivery of ESO-1 in a way that we believe should strengthen the patient's immune reactivity to this antigen."

"ESO-1 is an important addition to Therion's technology platform, a system that enables us to test multiple product candidates in the clinic in order to develop therapeutic vaccines targeted against a variety of cancers, including breast, prostate and ovarian cancers. We are giving this promising antigen priority, and plan to evaluate vaccines based on ESO-1 both alone and in combination with other antigens and immune-modulating proteins," said Dennis L. Panicali, Ph.D., President and Chief Executive Officer of Therion. "This collaboration with the Ludwig Institute also expands our outstanding network of academic and clinical alliances, partnerships that include leading researchers at the National Cancer Institute and NIH-affiliated hospitals." Dr. Panicali noted that Therion currently has six cancer vaccines in Phase I or Phase I/II clinical trials, and is collaborating with Pasteur M�rieux Connaught to advance the development of products to treat colorectal and lung cancer and melanoma.

ESO-1 is a member of a rapidly growing family of cancer antigens, referred to as cancer-testis (CT) antigens because their expression in normal tissue is restricted to testes. Other members of the CT family of antigens are MAGE, SSX, and SCP-1. CT antigens represent some of the most attractive targets identified to date for cancer vaccine development because of their specificity and their expression by a broad range of different tumor types.

Under terms of the collaboration, Therion will develop live recombinant pox virus vectors that incorporate the ESO-1 gene, producing therapeutic vaccines designed to elicit specific immune responses for cancer immunotherapy. The first clinical trials of ESO-1 will be conducted by researchers at the Ludwig Institute, and are expected to begin in late 1999 or early 2000.

The Ludwig Institute for Cancer Research, consisting of ten distinct Branches in seven countries, conducts basic and clinical research focused on many areas of cancer discovery. Laboratory and clinical scientists with expertise in the fields of genetics, virology, immunology, growth factors and cytokines and cell biology work in close collaboration to maximize innovative discoveries that are relevant to understanding the etiology and control of cancer.

Therion Biologics Corporation is engaged in the development of therapeutic vaccines for cancer and preventive vaccines for AIDS. Therion is headquartered in Cambridge, Massachusetts.