FDA approves enzalutamide for chemo-naive metastatic prostate cancer

Enzalutamide, an androgen receptor blocker, has been approved by the Food and Drug Administration to treat men with metastatic castration-resistant prostate cancer who have not received chemotherapy, manufacturer Medivation announced Sept. 10.

The drug, which is marketed under the brand name Xtandi, received FDA approval in August 2012 as a second-line treatment for metastatic castration-resistant prostate cancer (MCRPC) in men previously receiving docetaxel.

Approval was based on the results of the PREVAIL phase III trial. Interim results of the trial were presented earlier this year at the Genitourinary Cancers Symposium sponsored by the American Society of Clinical Oncology (ASCO).

A same-day announcement by ASCO noted that the "pre-specified interim analysis for OS [overall survival] demonstrated a statistically significant improvement in patients who received enzalutamide," with a median overall survival of 32.4 months vs. 30.2 months in the placebo arm. "The OS improvement was supported by a statistically significant prolongation of [radiographic progression-free survival] in patients who received" the once-daily dose of 160 mg of enzalutamide, compared with placebo.

Additionally, the median time to initiation of cytotoxic chemotherapy was 28 months in the enzalutamide arm, compared with 10.8 months in the placebo arm.

The most common side effects in 10% or more of patients receiving enzalutamide from this trial and the randomized trial used for its initial approval were asthenia/fatigue, back pain, decreased appetite, constipation, arthralgia, diarrhea, hot flush, upper respiratory tract infection, peripheral edema, dyspnea, musculoskeletal pain, weight loss, headache, hypertension, and dizziness/vertigo.

According to its prescribing information, enzalutamide is being recommended at the 160-mg dose, taken orally with or without food.

gtwachtman@frontlinemedcom.com