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Phase II results demonstrate efficacy of abiraterone acetate plus prednisone for castration-resistant prostate cancer

At ASCO 2009 Cougar Biotechnology announced results from ongoing Phase II clinical trials of investigational drug CB7630 (abiraterone acetate). The data were released today in three poster presentations. These presentations are further detailed below:

Preliminary results of a phase II multicenter study of chemotherapy-naïve castration-resistant prostate cancer (CRPC) patients not exposed to ketoconazole, treated with abiraterone acetate plus prednisone (COU-AA-002)

A Phase II clinical trial of CB7630 (COU-AA-002) is being conducted by The Prostate Cancer Clinical Trials Consortium, a national clinical research group sponsored by the Department of Defense, with Dr. Charles J. Ryan, Associate Professor of Clinical Medicine at the University of California, San Francisco Comprehensive Cancer Center, as the principal investigator. In this Phase II trial, CB7630 in combination with prednisone is administered once daily to chemotherapy-naïve, ketoconazole-naïve patients with castration-resistant prostate cancer (CRPC), who had progressive disease despite treatment with LHRH analogues and other hormonal therapies.

In his poster discussion presentation, Dr. Ryan presented data on the 33 evaluable patients treated in the trial. After 12 weeks of treatment, 26 patients (79%) experienced a decline in prostate specific antigen (PSA) levels of greater than 30%, 24 (73%) experienced a PSA decline of greater than 50% and 10 (30%) experienced PSA declines of greater than 90%. For the 33 evaluable patients, the median time to PSA progression was 337 days (48 weeks).

Of the 33 evaluable patients, treatment with CB7630 plus prednisone resulted in radiologic disease control in 28 patients (85%) with partial responses in 9 patients (27%) and stable disease in 19 patients (58%).


A multicenter phase II study of abiraterone acetate (AA) demonstrates anti-tumour activity in docetaxel pre-treated castration-resistant prostate cancer (CRPC) patients (COU-AA-003)

The COU-AA-003 Phase II trial of CB7630 in patients with advanced prostate cancer who have failed docetaxel-based chemotherapy was conducted at numerous locations in the United States and United Kingdom. In the trial, CB7630 is administered orally, once daily, to patients with CRPC who have failed treatment with androgen deprivation therapy and failed treatment with first-line docetaxel-based chemotherapy.

Dr. Allison Reid from The Institute of Cancer Research and The Royal Marsden Hospital in the United Kingdom presented data on the 47 patients enrolled in this Phase II trial. CB7630 was well tolerated with only minimal toxicity in this post-docetaxel population. After 12 weeks of treatment, of the 47 patients treated, 24 patients (51%) experienced a decline in PSA of greater than 30%, with 19 patients (40%) demonstrating a decline in PSA levels of greater than 50%, and 6 patients (13%) demonstrating a decline in PSA levels of greater than 90%. Of the 47 evaluable patients with measurable tumour lesions, radiologic disease control was observed in 31 of the 47 patients (66%) with 6 patients (13%) experiencing confirmed partial radiological responses and 25 patients (53%) experiencing stable disease. The median time to PSA progression for the 47 patients in the trial was estimated to be 169 days (24 weeks).


Phase II multicenter study of abiraterone acetate (AA) plus prednisone therapy in docetaxel treated castration-resistant prostate cancer (CRPC) patients: impact of prior ketoconazole (COU-AA-004)

During his poster discussion presentation, Dr. Daniel Danila from Memorial Sloan-Kettering Cancer Center presented data from the ongoing Phase II trial of CB7630 in combination with prednisone in patients with advanced prostate cancer who have failed androgen deprivation and docetaxel-based chemotherapy (COU-AA-004).

The COU-AA-004 Phase II trial is being conducted at numerous locations in the United States and United Kingdom. In the trial, CB7630 in combination with prednisone is administered orally, once daily, to patients with CRPC who have failed treatment with androgen deprivation therapy and have failed treatment with first-line docetaxel-based chemotherapy. To date, a total of 58 patients have been enrolled in the trial at 8 different centers.
Of the 58 patients, 13 patients (22%) had visceral disease, 26 patients (45%) had bone and soft tissue metastases, 11 patients (19%) had bone metastases only and 8 patients (14%) had soft tissue metastases only. Additionally, 27 patients (47%) had been previously treated with ketoconazole, a drug that is currently used off-label as a secondary hormonal therapy.

The combination of CB7630 plus prednisone was well tolerated with only minimal toxicity in this post-docetaxel population. After 12 weeks of treatment, 20 patients (34%) experienced a confirmed decline in PSA levels of greater than 50%. Of the 31 patients who had not received prior treatment with ketoconazole, 13 patients (42%) experienced a confirmed decline in PSA levels of greater than 50%. Furthermore, of the 27 patients who had been previously treated with ketoconazole, 7 patients (26%) experienced a confirmed decline in PSA levels of greater than 50%.

Of the 18 evaluable patients with measurable tumour lesions, 3 patients (17%) experienced confirmed partial radiological responses (as measured by the RECIST criteria) and 11 patients (61%) experienced ongoing stable disease. For the 31 patients who had not received prior treatment with ketoconazole, the median time to PSA progression was estimated to be 198 days (28 weeks). Furthermore, for the 27 patients who had been previously treated with ketoconazole, the median time to PSA progression was estimated to be 99 days (14 weeks).
Alan H. Auerbach, Chief Executive Officer and President of Cougar Biotechnology, said, "We are pleased to present data from these clinical trials at the ASCO Annual Meeting. CB7630 continues to show strong evidence of antitumour activity in patients with chemotherapy-naïve disease as well as in patients with chemotherapy-refractory disease. These populations not only represent significant unmet medical needs in prostate cancer but also are representative of the patient populations being studied in our ongoing Phase III trials (COU-AA-301 and COU-AA-302). "

Arturo Molina, M.D., M.S., FACP, Chief Medical Officer and Executive Vice President of Clinical Research and Development of Cougar, added, "We are pleased to present the multi-center results of these Phase II studies, which continue to support the potential roles of CB7630 both as a second-line hormonal therapy for patients with advanced prostate cancer who fail first-line hormonal treatment and as a second-line therapy for patients with advanced prostate cancer who fail docetaxel-based chemotherapy. These patient groups continue to represent patient populations that are underserved with current treatments



Source: Cougar Biotech

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