Enzalutamide Gets FDA Nod for Late-Stage Prostate Cancer

Megan Brooks

Disclosures

August 31, 2012

August 31, 2012 — The US Food and Drug Administration (FDA) has approved enzalutamide (formerly known as MDV3100) to treat men with metastatic castration-resistant prostate cancer that has spread or recurred.

Developed by Astellas Pharma US Inc and Medivation Inc, the drug will be sold as Xtandi. It was reviewed under the FDA's priority review program, which provides for an expedited 6-month review for drugs that may offer major advances in treatment or that provide a treatment when no adequate therapy exists.

Xtandi, which was approved 3 months sooner than expected, is one of a new class of androgen inhibitors designed to interfere with the ability of testosterone to bind to prostate cancer cells.

According to the National Cancer Institute, an estimated 241,740 men will be diagnosed with prostate cancer and 28,170 will die from the disease in 2012.

"The need for additional treatment options for advanced prostate cancer continues to be important for patients," Richard Pazdur, MD, director of the Office of Hematology and Oncology Products in FDA's Center for Drug Evaluation and Research, said in a statement posted on the FDA Web site.

"Xtandi is the latest treatment for this disease to demonstrate its ability to extend a patient's life," Dr. Pazdur added.

Early End to Pivotal Trial

As reported by Medscape Medical News, in a study of nearly 1200 patients with metastatic castration-resistant prostate cancer previously treated with docetaxel-based chemotherapy, enzalutamide significantly prolonged median survival compared with placebo (18.4 vs 13.6 months; hazard ratio, 0.63; P < .0001).

The pivotal phase 3 trial, known as A Study Evaluating the Efficacy of the Investigational Drug MDV3100 (AFFIRM) was stopped early. The results were published online August 15 in the New England Journal of Medicine.

"This is an important new drug," Marc Garnick, MD, clinical professor of medicine at Harvard Medical School, with an oncology practice at Beth Israel Deaconess Medical Center, in Boston, Massachusetts, told Medscape Medical News on publication. "It will add greatly to the treatments that can be offered to our patients with advanced prostate cancer," he added. Dr. Garnick was not involved in the AFFIRM trial.

The FDA notes that the most common adverse effects observed with enzalutamide were "weakness or fatigue, back pain, diarrhea, joint pain, hot flush, tissue swelling, musculoskeletal pain, headache, upper respiratory infections, dizziness, spinal cord compression and cauda equina syndrome, muscular weakness, difficulty sleeping, lower respiratory infections, blood in urine, tingling sensation, anxiety, and high blood pressure."

In addition, seizures occurred in approximately 1% of those receiving enzalutamide. These patients stopped the drug. Patients with a history of seizure were excluded from the study, as were patients with an underlying brain injury with loss of consciousness, a temporary decrease in blood to the brain within the past 12 months, stroke, brain metastases, an abnormal connection of the arteries and veins in the brain, or patients taking medications that may lower the seizure threshold. "The safety of Xtandi is unknown in patients with these conditions," the FDA says.

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