Phase I study of amatuximab, a novel monoclonal antibody to mesothelin, in Japanese patients with advanced solid tumors

Amatuximab is a chimeric monoclonal antibody that targets mesothelin, which is expressed in virtually all mesotheliomas and pancreatic adenocarcinomas. The objective of this study was to determine the dose-limiting toxicity and the maximum tolerated dose. Patients with mesothelioma, pancreatic adenocarcinoma or other mesothelin-positive solid tumors were eligible for this study. Amatuximab was administered weekly as an intravenous infusion in 4-week cycles at progressively increasing doses ranging from 50 to 200 mg/m2. Seventeen patients received amatuximab. Two dose-limiting toxicities were observed: one at 50 mg/m2 and one at 200 mg/m2; the maximum tolerated dose of this study was determined to be 200 mg/m2. Of the 17 patients, 13 patients (76.5 %) experienced treatment-related adverse events. The most common adverse events were grade 1 fatigue (29.4 %) and pyrexia (23.5 %). The maximum serum concentration and area under the concentration curve values increased in an almost dose-proportional manner. Three patients had stable disease. Amatuximab was generally well tolerated at doses up to 200 mg/m2. The pharmacokinetic profile of amatuximab in the Japanese population was similar to that seen in the United States population (Clinical Trials.gov Identifier: NCT01018784).