A phase 2 study of the insulin-like growth factor-1 receptor inhibitor MK-0646 in patients with metastatic, well-differentiated neuroendocrine tumors.

Background: Neuroendocrine tumor (NET) cell lines frequently express both insulin-like growth factor (IGF) ligand and the cognate IGF-1 receptor (IGF-1R) and, as such, potentially depend on the activation of IGF-1R and its downstream effectors for growth and survival. Preclinical studies suggest that somatostatin analogs and mammalian target of rapamycin (mTOR) inhibitors exhibit antitumor activity against NETs through inhibition of IGF-1-dependent signaling, suggesting that IGF-1R inhibition may be a promising therapeutic approach to NETs. Therefore, the authors of this report evaluated the safety and efficacy of MK-0646, a fully human monoclonal antibody (MoAb) that binds to the IGF-1R, as monotherapy in patients with metastatic, well-differentiated NETs.

Methods: A phase 2 study was performed in which patients received intravenous MK-0646 10 mg/kg once weekly over 1 hour. Archived pretreatment tumor tissue was obtained and genotyped for v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS), phosphatidylinositol-3-kinase, catalytic, alpha polypeptide (PIK3CA); and v-raf murine sarcoma viral oncogene homolog B1 (BRAF) mutations, and immunohistochemistry was performed to measure the expression IGF-1R.

Results: Twenty-five patients received treatment (40% women; median age, 61 years; age range, 37-83 years), including 15 patients with carcinoid tumors and 10 patients with pancreatic NETs. No partial or complete responses were observed. The median progression-free survival was 4.2 months in the pancreatic NET cohort (range, 0.7-6.7 months) and 2.7 months in the carcinoid cohort (range, 2-3 months). Serious adverse events that were potentially related to MK-0646 included grade 3/4 hyperglycemia in 8 of 25 patients (32%), grade 2 hypersensitivity reaction in 1 of 24 patients (4%), and grade 3 lipase elevation in 1 of 25 patients (4%).

Conclusions: Despite a compelling preclinical rationale, MK-0646 was inactive as a single agent in well-differentiated NETs. Further studies of MK-0646 as a monotherapy in unselected NETs are unwarranted.