Cougar Biotechnology Presents CB7630 Phase I Clinical Data at the 2005 Prostate Cancer Symposium.

LOS ANGELES -- Cougar Biotechnology, Inc., a privately held biotechnology company, announced today that Phase I clinical results on Cougar's investigational drug, CB7630 (abiraterone acetate) as a new therapeutic approach for patients with prostate cancer was presented at the 2005 Prostate Cancer Symposium in Orlando. The Prostate Cancer Symposium is a multidisciplinary symposium on prostate cancer co-sponsored by the American Society of Clinical Oncology, the Prostate Cancer Foundation, the American Society for Therapeutic Radiology and Oncology, and the Society of Urologic Oncology. In the United States, prostate cancer is the most diagnosed cancer in men and is the second leading cause of cancer death in men. According to the American Cancer Society, in 2005, approximately 232,090 new cases of prostate cancer are expected to be diagnosed and approximately 30,350 Americans are expected to die of the disease.

The Phase I trials of CB7630 were conducted at The Institute of Cancer Research, in the Cancer Research UK Centre for Cancer Therapeutics and at the Royal Marsden Hospital in the United Kingdom, the results were published in the British Journal of Cancer in June 2004. The poster presentation, entitled "Clinical and Endocrine Evaluation of Abiraterone Acetate (AA), A Rationally Designed Small Molecule Inhibitor Of Androgen Synthesis Targeting 17 alpha Hydroxylase (17OH)/17,20 Lyase, in Patients With Hormone Refractory Prostate Cancer" was presented by Dr. Johann S. de Bono, MD, FRCP, MSc, PhD, Senior Lecturer and Consultant, Institute of Cancer Research, Royal Marsden Hospital. The results from the first Phase I trial showed that a single dose of 500 mg of abiraterone acetate given to 6 castrate men achieved suppression of testosterone to less than 0.14 nM or by 75% when baseline testosterone levels were greater than 0.6 nM. In these patients, androstenedione levels were suppressed in parallel to testosterone levels. Single doses of 10, 30 and 100 mg of abiraterone acetate administered to castrate patients did not result in testosterone suppression. In the second Phase I trial, 3 non-castrate patients with baseline testosterone levels greater than 9 nM were dosed once daily for 12 days with 500 mg. Testosterone levels were suppressed to less than 2 nM but remained above 0.7 nM. A second 3-patient non-castrate cohort, treated with 800 mg daily for 12 days, demonstrated suppression of testosterone to less than 0.7 nM in two patients, with a nadir of 1.7 nM in the third patient. No symptoms or signs of hypoadrenalism were observed in keeping with the continued secretion of the active glucocorticoid corticosterone, as with congenital deficiency of 17 alpha hydroxylase. Overall, the drug was very well tolerated with minimal toxicity and pharmacokinetic data supported once daily dosing.

"These Phase I trial results suggest that CB7630 (abiraterone acetate) is a novel selective agent that could offer clinical benefit to patients with hormone refractory prostate cancer," said Dr. de Bono. "We are eager to begin the Phase I/II trial, the design of which is being finalized, to further investigate the safety and efficacy of this drug."

About Cougar Biotechnology

Cougar Biotechnology, Inc. is a Los Angeles-based private biotechnology company established to in-license and develop clinical stage drugs, with a specific focus on the field of oncology. Cougar's oncology portfolio includes CB7630, which has completed Phase I clinical trials in prostate cancer and CB3304 which is currently being tested in a Phase I trial in non-Hodgkin's lymphoma. Further information about Cougar Biotechnology can be found at www.cougarbiotechnology.com.

Notes:

The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust work in partnership to form Europe's largest comprehensive cancer centre.