WASHINGTON, D.C. and CAMBRIDGE, Mass. � December 22, 2004 � Researchers led by John L. Marshall, M.D. of Georgetown University published the results of a Phase I study demonstrating the safety and anti-tumor activity of Therion Biologics� CEA-TRICOM� therapeutic cancer vaccine in the Journal of Clinical Oncology.

The Phase I study evaluated multiple dosing regimens of the CEA-TRICOM� vaccines in 58 patients with advanced CEA-expressing tumors. Investigators found that disease stabilization was achieved for at least four months in 40 percent of the study participants, and for more than six months in 24 percent of the participants. One patient with small cell lung cancer achieved a complete response, with no evidence of cancer after several months of vaccination. Side effects were primarily skin reactions at the site of vaccination and temporary flu-like symptoms after each vaccination.

Therion�s lead therapeutic vaccine targeting CEA expressing tumors is PANVAC-VF, which has the potential to extend survival in patients with pancreatic cancer by activating the proliferation of an array of cytotoxic T cells necessary to selectively target and destroy tumors. PANVAC-VF is in a Phase III clinical trial for the treatment of metastatic pancreatic cancer in patients who have previously received gemcitabine. Therion obtained an agreement from the U.S. Food and Drug Administration (FDA) in May 2004 to conduct the study under a Special Protocol Assessment (SPA).

�These results support the general safety of Therion�s approach to cancer vaccine therapy and the ability of the CEA-TRICOM� vaccines to mount significant specific immune responses,� said John Marshall, M.D., Associate Professor of Medicine at Georgetown University. Dr. Marshall was Lead Investigator of this Phase I study and is currently the Lead Investigator in the Phase III PANVAC-VF study at the Lombardi Cancer Center in Washington, DC. �Furthermore, the study provided an early indication that the CEA-TRICOM� vaccine may slow the progression of disease in patients with advanced cancers and underscores the benefit that such therapeutic vaccines may provide in the fight against cancer.�

�This study was an important part of the body of data that enabled us to optimize PANVAC-VF, now in a Phase III pivotal trial,� said Mark Leuchtenberger, President and Chief Executive Officer of Therion. �Assuming results are positive, we expect to submit a BLA in 2006.�

The details of the Phase I study titled, �A Phase I Study of Sequential Vaccinations With Fowlpox-CEA(6D)-TRICOM (B7-1/ICAM-1/LFA-3) Alone and Sequentially With Vaccinia-CEA(6D)-TRICOM, With and Without GM-CSF, in Patients With CEA-expressing Carcinomas," can be found in the December 21, 2004 online publication of the Journal of Clinical Oncology. Dr. Marshall was lead author of the paper with contributions from researchers at the Laboratory of Tumor Immunology and Biology at the National Cancer Institute�s Center for Cancer Research, and Therion Biologics Corporation.

About PANVAC-VF
PANVAC-VF specifically targets cancer cells expressing two proteins (or antigens), carcinoembryonic antigen (CEA) and mucin-1 (MUC-1), found on over 90 percent of pancreatic tumor cells. Therion�s vaccines are administered via subcutaneous injection in a �prime-boost� fashion, employing vaccinia as the priming vector, followed by sequential doses with a fowlpox vector. The vaccines also incorporate TRICOM�, Therion�s proprietary triad of costimulatory molecules (B7.1, ICAM-1 and LFA-3), designed to enhance and sustain a targeted immune response against tumor cells.

About Therion Biologics Corporation
Therion Biologics Corporation develops therapeutic vaccines that aim to extend and improve the lives of cancer patients. The company has two lead product candidates: PANVAC-VF, currently in a Phase III clinical trial for pancreatic cancer, and PROSTVAC�-VF currently in a Phase II clinical trial for prostate cancer. The company is applying its technology to develop its vaccine pipeline, including treatments for breast cancer, lung cancer, and the prevention of AIDS. For more information, please visit www.therion.com.

Therion Contact:
Titus Plattel
Sr. Director, Marketing
Therion Biologics
617.475.7312

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