AUTHOR=Shabaneh Tamer B. , Moffett Howell F. , Stull Sylvia M. , Derezes Thomas , Tait Leah J. , Park Spencer , Riddell Stan R. , Lajoie Marc J. TITLE=Safety switch optimization enhances antibody-mediated elimination of CAR T cells JOURNAL=Frontiers in Molecular Medicine VOLUME=2 YEAR=2022 URL=https://www.frontiersin.org/journals/molecular-medicine/articles/10.3389/fmmed.2022.1026474 DOI=10.3389/fmmed.2022.1026474 ISSN=2674-0095 ABSTRACT=

Activation of a conditional safety switch has the potential to reverse serious toxicities arising from the administration of engineered cellular therapies, including chimeric antigen receptor (CAR) T cells. The functionally inert, non-immunogenic cell surface marker derived from human epidermal growth factor receptor (EGFRt) is a promising safety switch that has been used in multiple clinical constructs and can be targeted by cetuximab, a clinically available monoclonal antibody. However, this approach requires high and persistent cell surface expression of EGFRt to ensure that antibody-mediated depletion of engineered cells is rapid and complete. Here we show that incorporating a short juxtamembrane sequence into the EGFRt polypeptide enhances its expression on the surface of T cells and their susceptibility to antibody-dependent cellular cytotoxicity (ADCC). Incorporating this optimized variant (EGFRopt) into bicistronic and tricistronic CAR designs results in more rapid in vivo elimination of CAR T cells and robust termination of their effector activity compared to EGFRt. These studies establish EGFRopt as a superior safety switch for the development of next-generation cell-based therapeutics.