Phase I study of the anti-MET antibody onartuzumab in patients with solid tumors and MET-positive lung cancer.

Onartuzumab is a monovalent, humanized, monoclonal antibody that showed significant survival benefits in combination with erlotinib in MET-positive non-small-cell lung cancer (NSCLC) in pre-specified subgroup analyses of a randomized phase II study. We conducted a two-stage, open-label, multicenter, phase I study of onartuzumab in Japanese patients. Stage 1 investigated the safety, tolerability, pharmacokinetics (PK), and recommended dose of onartuzumab in patients with solid tumors, and Stage 2 determined the safety, tolerability, and PK of onartuzumab plus erlotinib in patients with MET-positive NSCLC. Nine patients received onartuzumab monotherapy (4, 15, or 30 mg/kg on Day 1 of each 21-day cycle) in Stage 1, and six patients received onartuzumab (15 mg/kg) plus erlotinib (150 mg/day) in Stage 2. There were no dose-limiting toxicities in either stage. Serious adverse events (AEs) occurred in one patient in Stage 1 (convulsion), and two patients in Stage 2 (once case each of diarrhea, vomiting, and pulmonary embolism), but there were no grade 4 AEs or AEs leading to death. Onartuzumab PKs were linear in the dose range of 4 to 30 mg/kg, and were not affected by co-administration with erlotinib. PK parameters of onartuzumab were similar to those reported in non-Japanese patients. A partial response was observed in a patient with MET immunohistochemistry 3+ NSCLC without MET gene amplification. Based on these results, the recommended dose of onartuzumab in Japanese patients with solid tumors is 15 mg/kg every 21 days. The combination of onartuzumab with erlotinib is feasible in Japanese patients with MET-positive lung cancer.