Phase II study of eribulin mesylate (E7389) in patients with metastatic castration-resistant prostate cancer stratified by prior taxane therapy

Treatment options remain limited for patients with castration-resistant prostate cancer (CRPC). We evaluated eribulin mesylate (E7389), a nontaxane halichondrin B analog microtubule inhibitor, in patients with metastatic CRPC with or without previous taxane exposure. Men with histologically proven CRPC, with or without prior taxane exposure, were enrolled in an open-label, single-arm phase II trial. Patients received eribulin mesylate 1.4 mg/m2 as a 2- to 5-min i.v. bolus infusion on days 1 and 8 of a 21-day cycle. The primary efficacy end point was prostate-specific antigen (PSA) response rate. In total, 108 patients were assessable for safety (50 were taxane-pretreated) and 105 for efficacy in the per-protocol population. The median age of patients was 71 years and median number of cycles was 4. PSA decreases of ≥50% were achieved in 22.4% and 8.5% of taxane-naive and taxane-pretreated patients, respectively. The most common grade 3/4 adverse event was neutropenia, seen in 22.4% of chemo-naive and 40% of taxane-pretreated men. Grade 3 peripheral neuropathy occurred in none of the taxane-naive patients and 6.0% of taxane-pretreated patients. Eribulin mesylate demonstrated activity and a relatively favorable toxicity profile in metastatic CRPC.