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The U.S. Food and Drug Administration has approved a new indication for the use of Xtandi (enzalutamide) capsules to treat patients with metastatic castration-resistant prostate cancer (CRPC) who have not received prior chemotherapy. Xtandi had previously been approved for use in patients with metastatic CRPC who had received docetaxel (OT 9/25/14 issue).

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The drug, which is marketed by Astellas Pharma and Medivation, was approved after being granted priority review by the FDA, which shortens the time to complete a drug's review and aims to deliver a decision on marketing approval designation for drugs that may offer major advances in treatment or provide a treatment where no adequate therapy exists within six months under the Prescription Drug User Fee Act (PDUFA).


Approval of the new indication for Xtandi is based on results of the randomized, double-blind, multinational, Phase III PREVAIL trial of 1,717 men with metastatic CRPC who had not received previous chemotherapy. Treatment with Xtandi reduced the risk of death by 29 percent compared with placebo; and reduced the risk of progression of disease or death by 83 percent compared with placebo.


Treatment with Xtandi was also found to delay the time to initiation of chemotherapy, as well as time to a skeletal-related events.


"In the PREVAIL trial, the median time to initiating chemotherapy was delayed by 17 months with enzalutamide treatment as compared to placebo, so the result is a meaningful period of time during which men have their disease controlled without the need for chemotherapy," the co-principal investigator for the study Tomasz M. Beer, MD, FACP, Deputy Director of the Knight Cancer Institute and Professor of Medicine at Oregon Health & Science University, said in a news release.


A serious side effect reported with use of the drug was seizure, which occurred in 0.1 percent of patients who had not received chemotherapy. The most common adverse reactions occurring in patients treated with Xtandi were: asthenia/fatigue, back pain, decreased appetite, constipation, arthralgia, diarrhea, hot flush, upper respiratory tract infection, peripheral adema, dyspnea, musculoskeletal pain, weight loss, headache, hypertension, and dizziness/vertigo.