Abstract
BACKGROUND: Atrasentan, an oral endothelin receptor A antagonist, demonstrated phase 1 activity in patients with renal cell carcinoma (RCC). A phase 2 study was undertaken in patients with measurable or bone-only metastatic RCC in the pre-VEGF/TKI era. METHODS AND MATERIALS: Patients were stratified by disease status and prior immunotherapy. Eligible patients had no prior chemotherapy, 0 to 1 prior immunotherapies, and an Eastern Cooperative Oncology Group performance status of 0 to 2. Patients received atrasentan 10 mg per day until progression. The primary end point was progression-free (PF) rate at 6 months. Rates of 25% among patients treated with prior immunotherapy and 45% among patients with no prior immunotherapy were considered promising. A 2-stage design was used for cohorts without prior immunotherapy. RESULTS: From 2003 to 2005, 98 patients were registered. Median treatment duration was 9.9 weeks (range, 0.3-107 weeks). Toxicities were mild; 71% of patients reported no grade 3 or higher treatment-related events. Grade 4 events included neutropenia (n = 3), dyspnea (n = 2), thrombosis (n = 1), and arrhythmia (n = 1). Two grade 5 events (dyspnea and constitutional) were possibly treatment related. Six-month PF rates (90% confidence interval) were 14% (6-25), 0% (0-39), 8% (1-23), and 22% (8-44), respectively, for patients with prior immunotherapy/measurable disease (n = 44), prior immunotherapy/bone metastases (n = 6), no prior immunotherapy/measurable disease (n = 25), and no prior immunotherapy/bone metastases (n = 18). Median PF survival was 2.3 months (95% confidence interval, 2.0-3.5 months). CONCLUSION: Although well tolerated, atrasentan did not yield 6-month PF rates supporting its use as first-line monotherapy in patients with advanced RCC.