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ASCO Meeting Features New Data on Prostate Cancer Drug Xtandi (Enzalutamide)

Treatment approved in 2012 for metastatic castration-resistant disease (Feb. 13)

According to a recent announcement, new clinical data for Xtandi (enzalutamide, Medivation, Inc./Astellas Pharma), an oral androgen receptor inhibitor, will be presented at the American Society of Clinical Oncology (ASCO) 2013 Genitourinary Cancers Symposium in Orlando, Florida. The new findings include the following:

A phase II study assessed the efficacy and safety of enzalutamide monotherapy (160 mg) in 67 patients who had never received hormone therapy and who presented with normal testosterone levels (230 ng/dL or greater). Ninety-three percent of study participants experienced a decrease of 80% or more in prostate-specific antigen (PSA) levels at week 25. The median change in PSA was –99.6% (range: –100% to –86.5%). Serum testosterone increased by a mean of 114% at week 25 compared with baseline. The most common treatment-emergent adverse events (AEs) were mostly grade 1 or 2 in severity and included gynecomastia (36%), fatigue (34%), nipple pain (19%), and hot flush (18%).

A post hoc analysis of the AFFIRM trial — a randomized, multinational, placebo-controlled phase III study in patients with metastatic castration-resistant prostate cancer (mCRPC) who had previously received docetaxel — showed that concomitant corticosteroid use was associated with reduced overall survival (median of 12.8 months in the corticosteroid group vs. median not met in the no-corticosteroid group) and higher rates of grade-3 or -4 AEs (63.3% in the corticosteroid group vs. 34.4% in the no-corticosteroid group) in this population.

An analysis of the patients enrolled in the AFFIRM study showed that a greater percentage of patients treated with enzalutamide reported improvements in health-related quality of life (HRQoL) compared with those given placebo (42.2% vs. 14.5%, respectively; P < 0.001). Both the enzalutamide and placebo groups reported deterioration of HRQoL at some point during the study. However, compared with patients receiving placebo, patients treated with enzalutamide had a significantly prolonged time to deterioration of HRQoL.

A post hoc analysis of the AFFIRM study showed that outcomes in elderly (aged 75 years or more) and younger (aged less than 75 years) patients with post-docetaxel mCRPC treated with enzalutamide were comparable and significantly improved compared with outcomes in patients given placebo. Safety and tolerability findings were comparable between the two age groups.

In another post hoc analysis of AFFIRM data, 35% of patients remained on enzalutamide for 12 months or more, and 22% remained on therapy for 18 months or more.

Xtandi (enzalutamide) is an oral, once-daily androgen receptor inhibitor. The drug was approved by the FDA in August 2012 for the treatment of mCRPC in patients who have previously received docetaxel chemotherapy.

Source: Medivation, Inc.; February 13, 2013.

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