BACKGROUND: Systemic therapy options are limited for metastatic castration-resistant prostate cancer (CRPC) patients who progress following docetaxel (Taxotere). This phase II trial evaluated sunitinib malate in patients with progressing metastatic CRPC following prior docetaxel. PATIENTS AND METHODS: Patients with metastatic CRPC progressing following one to two chemotherapy regimens including docetaxel were included. The primary end point was progression-free survival (PFS) per radiographic and clinical evaluations. Oral sunitinib was administered 50 mg/day 4-weeks on followed by 2-weeks off per cycle up to a maximum of eight cycles or until clinical progression or intolerable toxicity. RESULTS: Thirty-six patients with a median age of 69.5 years were accrued. The median PFS was 19.4 weeks with a 12-week PFS of 75.8%. Four patients (12.1%) had a > or =50% prostate-specific antigen (PSA) decline and seven (21.2%) had a > or =30% PSA decline. Two of 18 patients (11.1%) with measurable disease demonstrated 30% declines by RECIST and eight (44.4%) displayed some shrinkage. A decline in pain score > or =2 points occurred in 13.6% of 22 assessable patients. Drug discontinuation due to toxic effects occurred in 52.8% of patients. CONCLUSION: Sunitinib malate demonstrated promising activity in metastatic CRPC progressing after prior docetaxel.