Enzalutamide

BACKGROUND: ;An array of clinical issues remains to be resolved for castration-resistant prostate cancer (CRPC), including the sequence of drug use and drug cross-resistance. At present, no clear guidelines are available for the optimal sequence of use of novel agents like androgen-receptor axis-targeted (ARAT) agents, particularly enzalutamide, and abiraterone.;METHODS: ;This study retrospectively analyzed a total of 69 patients with CRPC treated with sequential therapy using enzalutamide followed by abiraterone or vice versa. The primary outcome measure was the comparative combined progression-free survival (PFS) comprising symptomatic and/or radiographic PFS. Patients were also compared for total prostate-specific antigen (PSA)-PFS, overall survival (OS), and PSA response. The predictors of combined PFS and OS were analyzed with a backward-stepwise multivariate Cox model.;RESULTS: ;Of the 69 patients, 46 received enzalutamide first, followed by abiraterone (E-A group), and 23 received abiraterone, followed by enzalutamide (A-E group). The two groups were not significantly different with regard to basic data, except for hemoglobin values. In a comparison with the E-A group, the A-E group was shown to be associated with better combined PFS in Kaplan-Meier analysis (P = 0.

BACKGROUND: ;Interactions between industry and prescribers have raised concerns regarding conflicts of interest. To the best of the authors' knowledge, quantitative data measuring these interactions have been limited until recently. In the current study, the authors sought to determine whether an association exists between industry payments and prescriber behavior with regard to abiraterone and enzalutamide.;METHODS: ;Two Centers for Medicare and Medicaid Services databases were combined to analyze oncologists and urologists who received industry payments and/or prescribed abiraterone and enzalutamide. Correlation analysis was constructed on prescription count and industry payments. Multivariable median regression examined predictors of change in prescription count per dollar of industry payment. Stratifying prescribers by quantile evaluated threshold effects on prescribers.;RESULTS: ;The number of prescriptions was similar between prescribers who did and those who did not receive industry payment for both drugs. The median industry payment amount to prescribers differed between prescribers and nonprescribers for abiraterone ($72 vs $56) and enzalutamide ($59 vs $31). Although no statistical association was found to exist between industry payment amount and prescription count for abiraterone prescribers, an association was found to exist for enzalutamide prescribers (rho = 0.

BACKGROUND: ;Both enzalutamide and abiraterone have demonstrated improved radiographic progression-free and overall survival for castration-resistant prostate cancer (CRPC) compared with placebo controls before docetaxel treatment in phase III studies. These oral agents target androgen and androgen receptor signaling and are thought to be less toxic than chemotherapy. Cross-resistance to these agents was recently reported because of their similar mechanism of action, and it is important to assess which agent is more effective to use initially for CRPC.;METHODS/DESIGN: ;The present study is a phase III, investigator-initiated, multicenter, head-to-head, randomized controlled trial investigating enzalutamide vs. abiraterone as a first-line treatment for CRPC patients. Patients will be randomly assigned to an enzalutamide or an abiraterone treatment group. The primary endpoint is the time to prostate-specific antigen progression. The target sample size is set at 100 patients per group (total, 200 patients). The study duration is 5 years, and the duration for recruitment is 2 years and 6 months.;DISCUSSION: ;Thus far, there have been no prospective head-to-head studies comparing enzalutamide and abiraterone.