A phase II randomized study of cixutumumab (IMC-A12: CIX) or ramucirumab (IMC-1121B: RAM) plus mitoxantrone (M) and prednisone (P) in patients (pts) with metastatic castrate-resistant prostate cancer (mCRPC) following disease progression (PD) on docetaxel (DCT) therapy.

97 Background: Vascular endothelial growth factor (VEGF)-mediated angiogenesis and insulin-like growth factor (IGF-IR)-mediated signaling contribute to mCRPC growth. CIX and RAM are fully human IgG1 human monoclonal antibodies targeting IGF-IR and VEGF receptor-2 (VEGFR-2) respectively. We investigated the safety and efficacy of CIX or RAM in combination with M + P in mCRPC pts with PD on DCT. METHODS: Eligible pts had mCRPC and PD during/within 120 days of DCT, ECOG PS 0-2, PSA ≥ 2 ng/mL, and adequate organ function. All pts received M 12 mg/m(2) IV every 3 weeks (w) + P 5 mg PO BID for up to 12 cycles and were randomized to either CIX 6 mg/kg or RAM 6 mg/kg IV q w. Tumor assessments were after the first 3 cycles and then q6w. Primary endpoint was composite progression-free survival (cPFS: either RECIST PD, bone scan PD or new skeletal events). Other endpoints included safety, response and overall survival (OS). Sample size was based on a targeted 50% increase in median (mdn) cPFS from 2.6 months (m) to 3.9 m. RESULTS: 132 pts were treated; 66 each to CIX or RAM. Mdn age and baseline PSA was 65 yr and 129 ng/mL for pts treated with CIX and 68 yr and 111 ng/mL for RAM. Involvement of sites other than bone was CIX: 79% and RAM: 70%. The most frequent Grade ≥3 related adverse events for CIX/M/P: fatigue 17%, leukopenia 12%, and neutropenia 8%, and for RAM/M/P: leukopenia 8%, neutropenia 8% and hypertension 8%. Left ventricular dysfunction/CHF: 12% for CIX (0% G3) and 23% for RAM (8% G3). Mdn number of Rx cycles were 5 for CIX and 6 for RAM. Mdn follow-up was 22.7 m for CIX and 21.8 m for RAM. PSA response was 18.4% (8.8-32% 95% CI) on CIX and 22.0% (11.5-36% 95% CI) on RAM. Mdn cPFS and OS were 4.1 m (3.0-5.6 m 95% CI) and 10.8 m (6.5-13.0 m 95% CI) for CIX and 6.7 m (4.5-8.3 m 95% CI) and 13.0 m (9.5-16.0 m 95% CI) for RAM. CONCLUSIONS: CIX/M/P and RAM/M/P were reasonably tolerated and achieved the primary endpoint. Preliminary cPFS and OS of RAM/M/P appear encouraging; sustained disease control was observed in pts on both rx arms. Correlation of serum markers of IGF and VEGF activity with clinical endpoints is planned.

Duke Scholars

Author Andrew John Armstrong Medicine, Medical Oncology