FDA approves Abiraterone for Late-Stage Prostate Cancer

After an expedited six-month review, abiratone acetate (tradename Zytiga) has been approved by the FDA for the treatment of castration-resistant prostate cancer.

The approval comes ahead of its June 20, 2011 regulatory date due to the significant increase in overall survival shown by arbiraterone treatment. In a Phase III study, patients who received abiratone in combination with prednisone had a median overall survival of 14.8 months, compared to 10.9 for patients in the placebo group. Treatment with abiratone also resulted in a 35% reduction in the risk of death.

“While 3.9 months may not seem like much, in the history of prostate cancer, only 4 drugs have ever shown a survival benefit” said abiraterone investigator, Johann de Bono, MD., putting into perspective the apparent modest increase in survival.

The results of the trial were found by an independent panel to be so successful that it was considered unethical to keep the placebo patients without the drug. The study was stopped earlier than planned and placebo patients were crossed over to abiraterone treatment.

Abiraterone inhibits the enzyme CYP17A1 which is found in testicular, adrenal and prostate tumor tissues. The enzyme plays an important role in the production of testosterone which has been found to stimulate prostate tumor growth. Abiraterone works by ”[ultimately blocking] the cancer cell from making its own hormones” said Johann de Bono, resulting in tumor shrinkage.

Abiratone also seems promising in the treatment of breast cancer. A Phase I/II clinical trial evaluating the effectiveness of abiratone in late-state breast cancer patients is underway in the U.K.

Sources: MedScape; April 28, 2011, FDA Press Release,  Investor’s Business Daily; September 24, 2010, ESMO 2010 interview by Oncology Tube: Johann de Bono, MD, GEN; September 10, 2010.

Author: Karla Robleto, Ph.D.

Add comment May 5th, 2011