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The Food and Drug Administration (FDA) today approved the New Drug Application (NDA) that permits marketing of Plenaxis (abarelix), a drug for advanced prostate cancer for patients who have no alternative therapy. The drug, indicated for the treatment of the symptoms of men with advanced prostate cancer who cannot take other hormone therapies and who have refused surgical castration, will be marketed under a voluntary risk management program (RMP) agreed to and administered by the sponsor that will restrict the use of Plenaxis to patients with advanced prostate cancer, who have no alternative therapy, because of an increased risk of serious, and potentially life-threatening, allergic reactions associated with its use. About 5-10% of men with prostate cancer have the type of advanced, symptomatic disease that would make them candidates for Plenaxis.
Plenaxis is a type of medicine (called a gonadotropin-releasing hormone (GnRH) antagonist) that lowers the male hormone testosterone, which is a key factor involved in most prostate cancer growth. The effectiveness of Plenaxis in lowering testosterone production in men with advanced, symptomatic prostate cancer was demonstrated in a study of 81 men. The study showed that such patients could avoid surgical castration by undergoing at least 12 weeks of treatment. Some of the men also experienced other benefits from the use of this product, including decreased pain and relief from urinary problems. However, three of the 81 patients in the clinical trial experienced serious allergic reactions, one of which included loss of consciousness.
The FDA and the manufacturer have agreed that marketing of Plenaxis should be restricted to those patients with advanced, symptomatic prostate cancer and who do not have other treatment options because of this increased risk of serious, and potentially life-threatening, allergic reactions. Because of the risk of low blood pressure and fainting as part of the allergic reaction to Plenaxis, patients who receive the drug are to be monitored for at least 30 minutes after receiving a dose of the drug in their health care provider's office setting. Moreover, the manufacturer will not be distributing the drug through retail pharmacies; rather, the drug will be distributed directly to physicians and hospital pharmacies enrolled in the Plenaxis RMP.
Plenaxis is administered as an injection into the muscles of the buttocks every two weeks for the first month of therapy, followed by once every four weeks thereafter. Because the drug may stop working in certain patients, doctors should perform blood tests about every two months to make sure Plenaxis is working by keeping the level of testosterone low.
The most common side effects seen in the clinical trial were hot flashes, sleep disturbances, pain, including back pain, breast enlargement or pain, and constipation.
The Plenaxis RMP that the drug's manufacturer will be implementing is designed to help ensure that patients and physicians are fully informed of the risks and benefits of Plenaxis before using it. The RMP emphasizes the need for doctors, patients and hospital pharmacists to work together to maximize the benefit of Plenaxis and minimize the risk.
As part of the program, the sponsor will only be distributing Plenaxis to physicians who attest to certain qualifications and are enrolled in Praecis' Plenaxis PLUS (Plenaxis User Safety) Program. In addition the company is establishing educational programs for physicians, patients, and hospital pharmacists about the risks and benefits of Plenaxis. Patients will be asked to read and sign a patient information leaflet before receiving the drug. The company will also establish a system that collects and reports adverse events to FDA. Enrolled physicians should also report serious adverse events to Praecis at 1-866-753-6294 or to FDA's MedWatch Program at 1-800-FDA-1088. Finally, the company will also be conducting studies an assessments of the risk management program, including an assessment of the prescribing and actual use of Plenaxis.
Plenaxis is marketed by Praecis Pharmaceuticals Inc., Waltham, Mass.
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