Zytiga Fights Treatment-Resistant Prostate Cancer
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Reviewed By Laura J. Martin, MD
April 28, 2011 -- The FDA has approved the Johnson & Johnson pill Zytiga for use in combination with the steroid prednisone to treat a certain type of late-stage prostate cancer in men who have already been treated with chemotherapy.
The medication is to be used to treat patients with metastatic, castration-resistant prostate cancer.
In men with prostate cancer, the male sex hormone testosterone stimulates the tumor to grow.
The FDA says in a statement that drugs or surgery are used to reduce testosterone production or block the effects of testosterone, but that prostate cancer sometimes continues to grow, even when testosterone levels are low. Men with such cancers are said to have castration-resistant prostate cancer.
What Zytiga Does
Zytiga (abiraterone acetate) targets a protein called CYP17A1, which the FDA says plays a key role in the production of testosterone.
The agency says the drug works by decreasing the production of testosterone that stimulates cancer cells to keep growing.
The application for approval of the pill, made by the Johnson & Johnson unit Centocor Ortho Biotech, was considered under the FDA's priority review process. The FDA says that process provides for an expedited six-month review for drugs that are believed to offer major advances in treatment or which provide a treatment when no adequate therapy exists.
Zytiga Prolongs Life
"Zytiga prolonged the lives of men with late-stage prostate cancer who had received prior treatments and had few available therapeutic options," Richard Pazdur, MD, director of the FDA's Office of Oncology Drug Products, says in the agency's news release.
The FDA says the drug's safety and effectiveness were established in a clinical study involving 1,195 patients with late-stage castration-resistant prostate cancer who had received treatment with docetaxel chemotherapy.
Patients in the study received either Zytiga once daily in combination with prednisone two times per day, or a placebo twice daily in combination with prednisone.
Patients who received the Zytiga and prednisone combo had a median overall survival of 14.8 months, compared to 10.9 months for those in the group taking the placebo-prednisone combination.
Commonly reported side effects of Zytiga included joint swelling or discomfort, low levels of potassium in the blood, fluid retention, usually in the legs and feet, muscle discomfort, hot flashes, diarrhea, and urinary tract infection.
Centocor, based in Horsham, Pa., says in a statement that the FDA's approval of Zytiga represents a step forward in the treatment of metastatic prostate cancer.
"As a clinician, I believe the efficacy and safety profile of abiraterone acetate, as well as its oral, once-daily formulation, will help address the important need for additional therapeutic choices for men living with this serious disease," Howard Scher, MD, of Memorial Sloan-Kettering Cancer Center in New York, says in the company's news release.
Johann S. de Bono, MD, PhD, MSc, FRCP, of the Royal Marsden NHS Foundation Trust in London, says in the company's statement that the approval of the drug marks "an exciting time for men with prostate cancer."
The drug's approval also was praised in the company's statement by Wendy L. Poage, MHA, president of the Colorado-based Prostate Conditions Education Council.
Prostate cancer forms in tissues of the prostate, a gland in the male reproductive system below the bladder, and usually occurs in older men, according to the National Cancer Institute (NCI). The NCI says 217,730 new cases of the disease were reported in 2010 and 32,050 men died of prostate cancer.
SOURCES: News release, FDA.News release, Centocor Ortho biotech.Fact Sheet, National Cancer Institute.
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