A first-in-human study of conatumumab in adult patients with advanced solid tumors

Purpose: To determine the safety, tolerability, pharmacokinetics, and maximum tolerated dose (MTD) of conatumumab, an investigational, fully human monoclonal agonist antibody against human Death Receptor 5, in patients with advanced solid tumors.

Experimental design: In the dose-escalation phase, patients received escalating intravenous doses of conatumumab (0.3, 1, 3, 10, or 20 mg/kg, 3-9 per cohort) every 2 weeks. In the dose-expansion phase, 10 patients with colorectal Cancer (CRC) and 7 with non-small cell lung Cancer (NSCLC) received 20 mg/kg of conatumumab every 2 weeks.

Results: Thirty-seven patients received 1 or more doses of conatumumab. Conatumumab seemed to be well tolerated; there were no dose-limiting toxicities. Of adverse events possibly related to treatment, only 3 patients (8%) had a grade 3 event (fatigue and/or elevated Lipase), and no anticonatumumab Antibodies were detected. An MTD was not reached. Conatumumab exhibited dose linear kinetics from 3 to 20 mg/kg, with a mean terminal half-life of 13 to 19 days. One patient with NSCLC (0.3 mg/kg) had a confirmed partial response (PR) at week 32 (38% reduction in tumor size), with further reduction (48%) by week 96; this patient remains on conatumumab after 4.2 years with a sustained PR. Fourteen patients had a best response of stable disease, 2 for 32 weeks or more. One patient with CRC (0.3 mg/kg) and stable disease for 24 weeks had a 24% reduction in tumor size by RECIST (Response Evaluation Criteria in Solid Tumors) and a 35% reduction in the sum of standardized uptake values of all lesions measured by [18F]fluorodeoxyglucose positron emission tomographic scan. Changes in tumor levels of activated Caspase-3 did not appear to be associated with tumor response.

Conclusions: Conatumumab can be administered safely up to the target dose of 20 mg/kg every 2 weeks.