Cougar Biotechnology Announces Presentation of Positive CB7630 Clinical Data at AUA Annual Meeting

Interim Phase II Results Confirm Efficacy of CB7630 in Chemotherapy Naïve Castration Resistant Prostate Cancer Patients

Los Angeles, CA, May 21, 2007 - Cougar Biotechnology, Inc. (OTCBB: CGRB) today announced that positive Phase I and Phase II data on the Company's prostate cancer drug candidate CB7630 (abiraterone acetate) was presented at the American Urological Association (AUA) Annual Meeting, which is currently taking place in Anaheim, California. The data was presented by Dr. Timothy A. Yap from the Cancer Research UK Centre for Cancer Therapeutics at The Institute of Cancer Research in an oral presentation entitled, "Abiraterone acetate, an inhibitor of androgen synthesis, has significant antitumor activity in castration resistant prostate cancer."

The Phase I/II trial of CB7630 was conducted at The Institute of Cancer Research and at The Royal Marsden NHS Foundation Trust in the United Kingdom. In the trial, CB7630 was administered orally, once daily, to chemotherapy-naïve patients with castration refractory prostate cancer (CRPC), who had progressive disease despite treatment with LHRH analogues and multiple other hormonal therapies, including antiandrogens, diethylstilboestrol and dexamethasone. To date a total of 38 patients have been treated in the Phase I/II trial, including 15 patients treated in the Phase I portion of the trial and 23 patients treated in the Phase II portion of the trial. In his presentation, Dr. Yap reported that in the 38 patients treated in this trial, CB7630 was well tolerated at doses as high as 2000 mg/day with minimal toxicity. Moreover, no dose limiting toxicity has been observed in the trial to date.

In the 30 patients who were evaluable in the Phase I/II trial, 18 patients (60%) experienced a confirmed decline in prostate specific antigen (PSA) levels of greater than 50%, with 10 of the 30 patients (33%) experiencing PSA declines of greater than 90%. Six additional patients (20%) experienced a decline in PSA that was less than 50%. Of the 20 evaluable patients with measurable tumor lesions, treatment with CB7630 resulted in partial radiological responses (as measured by the RECIST criteria) in 11 patients (55%), with 7 patients demonstrating ongoing stable disease and 3 patients experienced regressing bone disease. Individual patients treated with CB7630 also experienced improvement in pain and a reduction in opioid use.

Currently 19 (63%) of the 30 patients in the Phase I/II trial remain on study and are continuing to be treated with CB7630. Of the 15 patients in the Phase I portion of the trial, 9 patients (60%) are still receiving treatment with CB7630, with the average patient having received the drug for over 9.2 months and with 4 patients having received the drug for over 12 months.

Dr. Arie S. Belldegrun, M.D., FACS, Vice Chairman of the Board of Directors of Cougar Biotechnology, said, "The clinical data on abiraterone continues to demonstrate strong evidence of the antitumor activity of the drug in CRPC patients. CB7630 has the potential to be used by both urologists who treat patients with second line hormonal therapies and by medical oncologists who treat patients in the second line chemotherapy setting; therefore, we are pleased to be able to present, for the first time, the clinical data on abiraterone to the urology community." Alan H. Auerbach, Chief Executive Officer and President of Cougar Biotechnology, added, "We are pleased to be able to present the clinical data from this CB7630 trial at AUA. We look forward to continuing to provide updates on these ongoing trials at future cancer conferences and greatly look forward to the continued development of CB7630 in both the second line hormone therapy and second line chemotherapy settings."

About Cougar Biotechnology

Cougar Biotechnology, Inc. is a Los Angeles-based 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, a targeted inhibitor of the 17-alpha hydroxylase/c17,20 lyase enzyme, which is currently being tested in Phase II clinical trials in prostate cancer; CB3304, an inhibitor of microtubule dynamics, which is currently in a Phase I trial in hematological malignancies and CB1089, an analog of vitamin D, which has been clinically tested in a number of solid tumor types.

Further information about Cougar Biotechnology can be found at www.cougarbiotechnology.com.