Abiraterone, an experimental drug that inhibits the production of male hormones such as testosterone by both the testes and the adrenal glands, has shown promise in the treatment of hormone refractory prostate cancer. These results were presented at the Prostate Cancer Foundation Scientific Retreat.
Current treatment options for prostate cancer include watchful waiting, surgery, chemotherapy, radiation, or hormonal therapy. Hormonal therapy is designed to block testosterone from stimulating the growth of hormone-dependent types of prostate cancer. Some hormonal therapies (such as surgical removal of the testes or use of medications such as leuteinizing hormone releasing hormone [LHRH] analogues) inhibit production of testosterone by the testes. Other therapies, such as the antiandrogen drugs, block the activity of testosterone.
Some prostate cancers become resistant to standard hormonal therapy and require a different treatment approach; this condition is known as hormone refractory prostate cancer. Because hormone refractory prostate cancer can be difficult to treat, new agents and treatment approaches continue to be evaluated.
Abiraterone is an experimental drug that is taken orally. It blocks the production of androgens (male hormones such as testosterone) not only by the testes, but also by the adrenal glands.
To evaluate the safety and effectiveness of abiraterone in the treatment of men with hormone refractory prostate cancer, researchers have conducted two Phase II clinical trials.
The first trial enrolled men who had not received chemotherapy, and who had developed progressive prostate cancer in spite of LHRH analogues and other hormonal therapies. All the men had metastatic cancer.
- Among the 44 patients with PSA information, 27 (61%) experienced a more than 50% decline in PSA level.
- Among the 21 patients with information about tumor response, 12 (57%) experienced a partial reduction in detectable cancer.
The second trial enrolled men who had experienced cancer progression after both androgen deprivation therapy and docetaxel-based chemotherapy.
- Among the 28 patients who have been in the study for longer than three months, 14 (50%) experienced a more than 50% decline in PSA level.
- Among the 18 patients with information about tumor response, four (22%) experienced a partial reduction in detectable cancer.
These results suggest that abiraterone is active against advanced, hormone-refractory prostate cancer. A Phase III clinical trial of abiraterone is being planned.
Reference: Cougar Biotechnology. News Release. Cougar Biotechnology presents positive CB7630 Phase II data at Prostate Cancer Foundation Scientific Retreat. October 12, 2007. Available at: http://www.cougarbiotechnology.com/pr101207.html (Accessed October 17, 2007).