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Xtandi (Enzalutamide) Gets New Indication for Men With Metastatic Castration-Resistant Prostate Cancer

Treatment now approved for chemotherapy-naïve patients

The FDA has approved a new indication for the use of Xtandi (enzalutamide, Medivation/Astellas Pharma) capsules to treat patients with metastatic castration-resistant prostate cancer (CRPC). The new approved use follows a priority review of the product’s supplemental new drug application, which was based on results from the phase III PREVAIL trial.

The FDA initially approved Xtandi, an oral, once-daily androgen receptor inhibitor, in August 2012 for use in patients with metastatic CRPC who had received treatment with docetaxel (chemotherapy). The new indication approves Xtandi for use in men with metastatic CRPC who have not received chemotherapy.

Metastatic CRPC is defined as cancer that has spread beyond the prostate gland and has progressed despite treatment to lower testosterone (i.e., with gonadotropin-releasing hormone [GnRH] therapy or with removal of the testes).

In the PREVAIL trial, men receiving Xtandi and GnRH therapy showed a statistically significant improvement in both overall survival and the time to radiographic progression or death compared with men receiving placebo and GnRH therapy.

Xtandi significantly reduced the risk of radiographic progression or death by 83% compared with placebo (hazard ratio [HR] = 0.17; P < 0.0001). Moreover, the drug significantly reduced the risk of death by 29% compared with placebo (HR = 0.71; P < 0.0001). Treatment with Xtandi also delayed the time to initiation of chemotherapy and the time to a skeletal-related event.

Seizure occurred in 0.9% of patients treated with Xtandi who had received docetaxel and in 0.1% of patients who were chemotherapy-naïve.

The most common adverse reactions that occurred more commonly in Xtandi-treated patients than in those given placebo in two randomized clinical trials (PREVAIL and AFFIRM) included asthenia/fatigue, back pain, decreased appetite, constipation, arthralgia, diarrhea, hot flush, upper respiratory tract infection, peripheral edema, dyspnea, musculoskeletal pain, decreased weight, headache, hypertension, and dizziness/vertigo.

Enzalutamide is an androgen receptor inhibitor that acts on three different steps in the androgen receptor signaling pathway.

Source: Astellas Pharma US; September 10, 2014.

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