Functional avidity of anti-B7H3 CAR-T constructs predicts antigen density thresholds for triggering effector function
Marta Barisa, Henrike Muller, Elisa Zappa, Rivani Shah, Juliane L. Buhl, Benjamin Draper, Courtney Himsworth, Chantelle Bowers, Sophie Munnings-Tomes, Marilena Nicolaidou, Sonia Morlando, Kathleen Birley, Clara Leboreiro-Babe, Alice Vitali, Laura Privitera, Kyle O’Sullivan, Ailsa Greppi, Magdalena Buschhaus, Mario Barrera Román, Sam de Blank, Femke van den Ham, Brenna R. van ‘t Veld, Gabrielle M. Ferry, Jonathan Fisher, Debarati Shome, Reza Nadafi, Israr-ul H. Ansari, Rogier M. Reijmers, Stefano Giuliani, Paul M. Sondel, Laura Donovan, Louis Chesler, Jan J. Molenaar, Jarno Drost, Anne C. Rios, Kerry Chester, Judith Wienke, John Anderson
Abstract
Chimeric Antigen receptor T cell (CAR-T) treatments for solid cancers have been compromised by limited expansion and survival in the tumor microenvironment following interaction with antigen-expressing target cells. Using B7H3 as a model antigen with broad clinical applicability, we evaluate the relationship between the antibody/antigen affinity of three clinical candidate binders and the three following characteristics: cellular avidity, duration of sustained cytotoxicity in tumoroid re-stimulation assays, and in vivo anti-tumoral responses. Next, BEHAV3D video microscopy is used to assess CAR-T cell interaction with tumor cells at single cell resolution. These data are consistent with a threshold avidity of CAR-T / tumor cell interaction and target cell B7H3 expression level, where enhanced functionality is characterized by longer cumulative CD8+ CAR-T / tumor target interaction times, CAR-T cell expansion and sustained tumor control. Lower checkpoint receptor expression does not correlate with enhanced anti-tumor function. These results provide further insights into design of anti-B7H3 CAR-T cells for antigen-dim cell targeting, and avoidance of antigen-dim tumor relapse. CAR-T cells have been found to be less effective as treatment for solid tumours. Here the authors, utilising B7H3 as an antigen, consider how changes in B7H3 binders lead to functional changes of CAR-T cells and differences in tumour outcomes in humanised mouse tumour models.