E4206: AMG 706 and Octreotide in Patients with Low-Grade Neuroendocrine Tumors

Background. Neuroendocrine tumors (NETs) are rare malignancies of the gastrointestinal (GI) tract that are highly vascularized and overexpress vascular-endothelial growth factor (VEGF). Sunitinib has demonstrated efficacy in the pancreatic subset of NET. This study explored the activity of another oral VEGF inhibitor, AMG 706 or motesanib, a multikinase inhibitor that targets receptor tyrosine kinases, including VEGFR1, VEGFR2, VEGFR3, KIT, RET, and PDGFR (IC50s52, 3, 6, 8, 59, and 84 nM, respectively). Methods. This was a single-arm, first-line, phase II study run through the Eastern Cooperative Oncology Group. Patients with low-grade NET (as defined by central confirmation of Ki-67 of 0%-2%) were administered a flat dose of 125 mg per day orally combined with octreotide long acting-repeatable (LAR) for patients who had been on a stable dose. The primary objective was to determine the 4-month progression-free survival (PFS). Results. Forty-four patients were evaluated per protocol. The 4month PFS was 78.5%. The partial response rate was 13.6% (6/44), stable disease was 54.5% (24/44), 9.1% (4/44) had progressive disease, and 10/44 were not evaluable for response. Common toxicities included fatigue, hypertension, nausea, and headache, and most were grade 1-2. Median PFS was 8.7 months, and overall survival was 27.5 months. Conclusion. Motesanib (AMG 706) demonstrated a 4-month PFS that met the per-protocol definition of efficacy. Fatigue and hypertension were the most common toxicities, and few grade 3-4 toxicities were encountered. The progression-free survival of 8.7 months in all NETs merits further study.