Maximizing GlyTR pan-cancer immunotherapy by enhancing target density

Abstract Bi-specific antibodies and chimeric antigen receptor T-cells are the most potent cancer immunotherapeutics in clinical use, yet most cancers remain poorly targetable. High-affinity antibodies required to maximize killing detect low antigen expression in normal tissue, risking ‘on-target, off-cancer’ toxicity. This compels identification of cancer-restricted cell surface protein antigens, which are rare. Tumor Associated Carbohydrate Antigens (TACAs) are the most abundant and widespread cancer antigens known, but are poorly targetable by antibodies. With funding from the Cancer Moonshot program, we developed Glycan-dependent T cell Recruiter (GlyTR) pan-cancer immunotherapeutics that utilize high-avidity ‘velcro-like’ lectin binding to kill cells with high but not low TACA-expression. GlyTR1 and GlyTR2 bind β1,6GlcNAc-branched N-glycans or multiple TACA’s (Tn, sialyl-Tn , LacDiNAc, GD2), respectively, and trigger target-density dependent T cell mediated pan-cancer killing with EC50’s as low as 10 femtomolar and effector: tumor (E:T) ratio = 1:140; yet lack toxicity in mice with human-like TACA expression. The GlyTR1 bi-specific protein is undergoing IND enabling studies at the NCI Experimental Therapeutics program for a Phase 1 basket trial in refractory solid cancer, and similar translation of the GlyTR2 CAR T cell is pending. However, GlyTR target density can vary between cancers from different individuals, limiting the number of patients that could maximally benefit from GlyTR therapy. Moreover, targeting a single GlyTR antigen risks tumor escape. Therefore, here we propose to maximize GlyTR target density/killing, increase the proportion of patients highly responsive to GlyTR therapy and reduce risk of tumor escape using two different approaches: 1) engaging more targets by combining GlyTR1 and GlyTR2 therapy and 2) metabolically increasing target density in cancer cells but not normal cells. As GlyTR therapeutics are in late-stage pre-clinical development for planned Phase 1 clinical trials, positive results from this proposal can be quickly translated into additional clinical studies.