A phase II study of sorafenib in combination with bicalutamide in patients with chemotherapy-naive castration resistant prostate cancer

Summary Purpose The objective of this trial was to evaluate the clinical effects of sorafenib, a multi-targeted kinase inhibitor, in combination with androgen receptor blockade in patients with castration-resistant prostate cancer. Methods This was a multicenter, two-stage, phase 2 trial. Eligible patients had rising PSA, minimal symptoms and were chemotherapy-naïve. Sorafenib 400 mg twice daily was administered with bicalutamide 50 mg once daily on a 28-day cycle. The primary endpoint was PSA response (≥50% decline) or stable disease ≥6 months. Results 39 patients were enrolled including eight without clinical evidence of metastases. Eighteen (47%) patients have had either a PSA response or stable disease ≥6 months. PSA declines of ≥50% occurred in 12 (32%) of 38 assessable patients, including seven of 27 patients (26%) with prior anti-androgen use. Median time to treatment failure was 5.5 months (95%CI = 4.8.1–8.3). Grade ≥3 adverse events included fatigue, skin rash, and hand-foot syndrome. Conclusions PSA declines and stable disease were observed with a combination of sorafenib and bicalutamide including in patients previously progressing on bicalutamide. Strategies to combine multi-targeted kinase inhibitors with hormonal therapies warrant further study in patients with CRPC.