Phase III, randomized, placebo-controlled study of docetaxel in combination with zibotentan in patients with metastatic castration-resistant prostate cancer

Purpose: As part of the ENTHUSE (Endothelin A Use) program, the efficacy and safety of zibotentan (ZD4054), an oral specific endothelin A receptor antagonist, has been investigated in combination with docetaxel in patients with metastatic castration-resistant prostate cancer (CRPC). Patients and Methods: In this randomized, double-blind, placebo-controlled, phase III study, patients received intravenous docetaxel 75 mg/m² on day 1 of 21-day cycles plus oral zibotentan 10 mg or placebo once daily. The primary end point was overall survival (OS). Secondary end points included time to pain and prostate-specific antigen (PSA) progression, pain and PSA response, progression-free survival, health-related quality of life, and safety. Results: A total of 1,052 patients received study treatment (docetaxel-zibotentan, n 524; docetaxel-placebo, n 528). At the time of data cutoff, there had been 277 and 280 deaths, respectively. There was no difference in OS for patients receiving docetaxel-zibotentan compared with those receiving docetaxel-placebo (hazard ratio, 1.00; 95% CI, 0.84 to 1.18; P .963). No significant differences were observed on secondary end points, including time to pain progression (median 9.3 v 10.0 months, respectively) or pain response (odds ratio, 0.84; 95% CI, 0.61 to 1.16; P .283). The median time to death was 20.0 and 19.2 months for the zibotentan and placebo groups, respectively. The most commonly reported adverse events in zibotentan-treated patients were peripheral edema (52.7%), diarrhea (35.4%), alopecia (33.9%), and nausea (33.3%). Conclusion: Docetaxel plus zibotentan 10 mg/d did not result in a significant improvement in OS compared with docetaxel plus placebo in patients with metastatic CRPC.