Antibody-Drug Conjugates (ADCs) as Adaptors for Universal CAR T cells 2259384

Abstract

Abstract Introduction Antibody—drug conjugates (ADCs) and chimeric antigen receptor (CAR) T cells are powerful cancer therapeutics, but each faces limitations. ADCs often fail to yield durable responses due to drug payload resistance or poor internalization. CAR T cells are often thwarted by challenges including immune suppression and poor persistence. To overcome these challenges, we developed a universal CAR T cell platform in which ADCs act as antigen-targeting “adaptors” that direct CAR T cell activity. In this system CAR T cells are co-administered with one or more ADCs. Instead of the CAR directly binding to a tumor antigen, ADCs bind to antigens, thus activating CAR signaling in addition to drug payload delivery. Methods We used our previously generated SNAP-CAR, a universal CAR that covalently binds to antibodies with a benzylguanine (BG) tag. We generated ADC adaptors by conjugating BG to several FDA-approved ADCs targeting HER2 and FOLR1. In parallel, we designed a novel universal anti-DM1/DM4 CAR that directly binds DM1 and DM4 drug payloads. Primary human CAR T cells were co-incubated with antigen-positive or -negative tumor cells and various adaptors, followed by flow cytometric assessment of T cell activation, target cell lysis, and bystander killing. Results SNAP-CAR T cells with ADC—BG adaptors showed strong, adaptor dose-dependent T cell activation and tumor lysis, outperforming unconjugated ADCs or BG-labeled antibodies. Additionally, these adaptors enabled bystander killing of antigen-negative tumor cells. Anti-DM1/DM4 CAR T cells were similarly effective showing dose-responsive activities induced by ADCs and in a HER2+ human tumor xenograft mouse models. Excitingly, both approaches were capable of potent killing of DM1/DM4-resistant cells, demonstrating their ability to overcome drug resistance limiting ADC therapies. Conclusion ADC-directed universal CAR T cells represent a highly modular approach that synergizes cytotoxic drug activity with immune function to overcome therapeutic resistance. Funding Source conditional R01 and the Gap Fund and Supported by the University of Pittsburgh Commercialization Gap Fund Topic Categories Tumor Immunology: Checkpoints, Prevention, and Treatment (TIPT)