Interim Phase II Results Support Efficacy of Abiraterone Acetate in Advanced Prostate Cancer Patients

Positive Phase II Data on Cougar Biotechnology's CB7630 Presented at Prostate Cancer Foundation Scientific Retreat

LOS ANGELES, Oct 17, 2008 (BUSINESS WIRE) -- Cougar Biotechnology, Inc. (CGRB) today announced that results from an ongoing Phase II clinical trial of Cougar's investigational drug CB7630 (abiraterone acetate) were presented today at the Prostate Cancer Foundation Scientific Retreat. The Prostate Cancer Foundation Scientific Retreat is currently taking place in Lake Tahoe, Nevada.

The clinical trial of CB7630 was conducted at the University of Texas M.D. Anderson Cancer Center in order to investigate associations between serum and microenvironment (bone marrow) androgen concentrations and response to CB7630. In the trial, CB7630 in combination with prednisone was administered orally, once daily, to patients with castration resistant prostate cancer (CRPC), who had progressive disease despite treatment with LHRH analogues and multiple other therapies. All of the 44 patients who were enrolled in the trial had radiological evidence of metastatic disease with bone metastases. Thirty-eight patients (86%) had at least 10 metastatic bone lesions, 7 patients (16%) had metastases in the liver and 14 patients (32%) had lymph node metastases. Twenty-five (57%) of the 44 patients had received prior treatment with ketoconazole and/or diethylstilbesterol and 38 patients (86%) had received prior treatment with chemotherapy, with 27 patients (61%) having received two or more prior chemotherapy regimens before entering the trial.

In her poster presentation entitled, "Identification of an androgen withdrawal responsive phenotype among patients with castrate resistant prostate cancer (CRPC) treated with abiraterone acetate, a selective CYP17 inhibitor (COU-AA-BMA)," Dr. Eleni Efstathiou from the University of Texas MD Anderson Cancer Center presented data on the 41 evaluable patients treated in the trial. Of the 41 evaluable patients, 21 patients (51%) experienced a confirmed decline in prostate specific antigen (PSA) levels of greater than 50% with a median duration of 6+ months. In addition, 5 patients (12%) experienced PSA declines of greater than 90%. Of the 41 evaluable patients, 24 (59%) experienced an improvement in performance status.
Of the 16 evaluable patients with bone metastases, after 6 months of treatment 4 patients (25%) showed an improvement in their bone scan and 11 patients (69%) showed a stable bone scan. Also, 5 of 5 patients with lymph node metastases showed stable disease after 6 months of treatment with CB7630 and 1 of 2 patients with liver metastases demonstrated a partial radiological response (as measured by the RECIST criteria).

Both serum and bone marrow testosterone levels were measured before and after treatment with CB7630. A decline in both serum and bone marrow testosterone levels to below detectable levels (<10ng/ml.

SOURCE: Cougar Biotechnology, Inc.