Onyvax Granted Broad European Patent For Prostate Cancer Vaccines

London, UK – 14 September, 2005: Onyvax Limited, the biotechnology company developing novel cancer therapies, today announced that it has been issued a broad patent (European Patent No. 1,137,422) that includes specific composition of matter claims relating to the Company's proprietary prostate cancer vaccine program. The patent covers all combinations of three prostate cell lines including those used in Onyvax-P, the company’s lead product. Onyvax-P is designed to stimulate the immune system to fight prostate cancer, and this patent significantly strengthens the Company’s intellectual property position.

The reason cancer is such a difficult condition to treat is largely due to the diversity of the disease. Tumors in different patients express different genes and antigens, and even cancer cells within the same patient are highly variable. Furthermore, it is known that the gene expression of tumor cells changes over time as the cancer progresses. Most tumor therapies target one specific mutation or mechanism and may eliminate the majority of tumor cells. However, the remaining cells that do not express the target are resistant to therapy and continue to grow. As Onyvax’s Cell Vaccines are formulated from three different prostate cell lines, each representing a different stage of the disease, they contain the full range of tumor antigens expressed by the disease. As a result, very broad immune responses are generated that are selective for the tumor type and therefore the risk of the disease becoming resistant to the therapy is significantly reduced.

Dr. Anthony Walker, CEO of Onyvax Ltd, said: "We are pleased to have been issued this broad patent which strengthens the intellectual property position around our Cell Vaccine technologies. The ownership of particular cell lines will remain the cornerstone of our proprietary position, but this patent provides additional protection and enhances our competitive stance going forward”.

In the major pharmaceutical markets, over 500,000 men are diagnosed with prostate cancer per year and about 160,000 die of the disease annually. According to the American Cancer Society, prostate cancer is the most common cancer among men in the US, with an estimated 220,900 new cases diagnosed each year. It is the second leading cause of cancer death in American men, with about 28,900 deaths per year, exceeded only by lung cancer.

For further information, please contact:

Onyvax
Dr Anthony Walker / Robert Johnson
+44 (0)208 682 9494

Financial Dynamics
Julia Philips / Lucy Briggs
+44 (0)20 7831 3113

Notes to Editors:

Onyvax Ltd is a biotechnology company developing novel cancer therapies that harness the selective power of the immune system to seek and destroy tumour cells.

Founded in 1998, Onyvax is developing products that use the power of the immune system to treat of prostate and other cancers. Onyvax’s lead products are based on combinations of inactivated cell lines that induce immune responses to a broad spectrum of tumour targets. Onyvax-P, a Cell Vaccine for prostate cancer, is due to enter Phase IIb/III clinical trials in 2005. For each cancer type, Onyvax generates banks of proprietary cell lines representative of different stages of the disease. The vaccines are manufactured in bulk under standardized conditions. The Phase II trial for Onyvax-P was conducted by the Department of Oncology at St George’s Hospital Medical School, London, UK.

Onyvax is committed to the commercialisation of new therapies that significantly prolong survival while maintaining a high quality of life for cancer patients. The Company is based in London and has collaborations with leading institutions in Europe and the US. Further information on Onyvax can be found at www.onyvax.com