Overcoming Tumor Heterogeneity by Ex Vivo Arming of T Cells Using Multiple Bispecific Antibodies

초록

T cell immunotherapy has improved treatment outcomes for cancer patients with high-risk disease. However, the efficacy has been limited because of tumor heterogeneity and target antigen loss or down-regulation. To overcome tumor heterogeneity preventing treatment resistance or clonal escape, we explored the potential of multi-antigen targeting T cells ex vivo armed with multiple bispecific antibodies (multi-EATs).T cells were ex vivo armed with BsAbs built on the IgG-[L]-scFv platform, where an anti-CD3 (huOKT3) scFv was attached to the carboxyl end of both light chains of a tumor specific IgG. Multi-EATs generated by combining multiple BsAbs on the same T cells were compared among monospecific EATs (mono-EATs), pooled- or alternate-EATs (by combining mono-EATs), and TriAb-EATs [by combining specificities on the same antibody (TriAb)] using flow cytometry, in vitro cytotoxicity, cytokine release assays, and in vivo studies performed in BALB-Rag2-/-IL-2R-γc-KO (BRG) mice xenografted with cancer cell line (CDX) or patient-derived tumor (PDX). Multi-EATs retained target antigen specificity and anti-tumor potency both in vitro and in vivo without excessive cytokine release. Multi-EATs targeting GD2, HER2, CD33, PSMA, and STEAP1 demonstrated identical and robust anti-tumor efficacy compared with mono-EATs against individual tumor targets. Multi-EATs were more effective than pooled-EATs or TriAb-EATs and could overcome tumor heterogeneity and target antigen loss, while mono-EATs could ablate tumors in an exquisitely antigen-specific manner and were unable to control antigen-negative clones.