Premedication and Chemotherapy Agents do not Impair Imgatuzumab (GA201)-Mediated Antibody-Dependent Cellular Cytotoxicity and Combination Therapies Enhance Efficacy

Purpose: Imgatuzumab (GA201) is a novel anti-EGFR mAb that is glycoengineered for enhanced antibody-dependent cellular cytotoxicity (ADCC). Future treatment schedules for imgatuzumab will likely involve the use of potentially immunosuppressive drugs, such as premedication therapies, to mitigate infusion reactions characteristic of mAb therapy and chemotherapy combination partners. Because of the strong immunologic component of mode of action of imgatuzumab, it is important to understand whether these drugs influence imgatuzumab-mediated ADCC and impact efficacy. Experimental Design: We performed a series of ADCC assays using human peripheral blood mononuclear cells that were first preincubated in physiologically relevant concentrations of commonly used premedication drugs and cancer chemotherapies. The ability of common chemotherapy agents to enhance the efficacy of imgatuzumab in vivo was then examined using orthotopic xenograft models of human cancer. Results: A majority of premedication and chemotherapy drugs investigated had no significant effect on the ADCC activity of imgatuzumab in vitro. Furthermore, enhanced in vivo efficacy was seen with imgatuzumab combination regimens compared with single-agent imgatuzumab, single-agent chemotherapy, or cetuximab combinations. Conclusions: These data indicate that medications currently coadministered with anti-EGFR therapies are unlikely to diminish the ADCC capabilities of imgatuzumab. Further studies using syngeneic models with functional adaptive T-cell responses are now required to fully understand how chemotherapy agents will influence a long-term response to imgatuzumab therapy. Thus, this study and future ones can provide a framework for designing imgatuzumab combination regimens with enhanced efficacy for investigation in phase II trials. (C) 2015 AACR.