Onyvax Completes Enrolment in
Phase II Clinical Trial in Prostate Cancer

London, UK, 14th April 2003 – Onyvax Ltd, a leading vaccine therapy company, today announced it has completed patient recruitment in its Phase IIa clinical trial in prostate cancer. The study with Onyvax-P was initiated in January 2002 and targets a total of 48 evaluable patients.

Onyvax P is a therapeutic prostate cancer vaccine designed to elicit a powerful and specific immune response against prostate cancer cells without the severe side effects often associated with conventional cancer therapies. Study participants receive the vaccine therapy for a period of 12 months and are followed for a further 12-month period.

Earlier results with an Onyvax prostate cancer vaccine demonstrated safety and good tolerability with no major side effects reported. The trial also showed the vaccine was capable of producing an immune response against cancer cells, with patients experiencing an increase in cytokine production, antibody response and evidence of T-cell proliferation.

Onyvax-P consists of three cell lines that are representative of different stages of the disease and targets a broad range of prostate cancer associated antigens. The cells have been irradiated so they cannot grow or divide.

“Cancer clinical trials can be extremely difficult to enrol due to the often strict eligibility requirements, and we are pleased to announce this milestone in our Phase IIa Onyvax-P study,” said Anthony Walker, CEO of Onyvax.

Onyvax will be presenting preliminary data from the current study at the annual meeting of the American Association of Immunologists in Denver, May 6th-10th. The Company will also be speaking at Advances in Designing Cancer Vaccines in Boston on 24th April 2003.

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 per 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. In the UK, some 21,000 men are diagnosed with prostate cancer per year and about 9,500 die of the disease annually. If detected early enough, prostate cancer can be treated effectively by surgery or radiotherapy while hormone therapy can control later stages of the disease. However, no treatment is currently available for patients who have failed hormone therapy, and median survival time for these patients is approximately 13 months.