Kharfan-Dabaja, M. A. | Search bioRxiv

bioRxiv2026

A Standalone PD-1 Chimeric Switch Receptor T-Cell Platform Expands the Therapeutic Window of PD-L1 Targeting in Solid Tumors

Programmed death-ligand 1 (PD-L1) is a promising therapeutic target owing to its broad expression on tumor cells and immunosuppressive myeloid cells within the tumor microenvironment (TME), providing an opportunity to target both cellular compartments. However, physiological PD-L1 expression in normal tissues poses a substantial risk of on-target/off-tumor toxicity, limiting the therapeutic window and clinical translation of PD-L1-targeted cellular therapies. Here, we developed a standalone programmed death-1 (PD-1) chimeric switch receptor (CSR) T-cell platform designed to preserve the therapeutic advantages of PD-L1 targeting while improving tumor-normal discrimination. Iterative receptor engineering, with antitumor activity and normal-cell reactivity evaluated as parallel selection criteria, identified two lead PD-1 CSR T-cell candidates. Compared with our previously developed antibody-based PD-L1 CAR T cells, the lead candidates retained potent PD-L1-specific cytotoxicity against tumor cells while exhibiting markedly reduced cytotoxicity against primary human small airway epithelial cells, astrocytes, renal epithelial cells, hepatocytes, and cardiomyocytes. They also efficiently eliminated PD-L1-positive immunosuppressive myeloid cells and mediated dual-compartment targeting of tumor and myeloid cells in three-dimensional (3D) multicellular tumor organoids. In vivo, both candidates suppressed tumor growth and prolonged survival in orthotopic breast cancer and patient-derived glioblastoma models after systemic and intracranial administration, respectively. Collectively, these findings establish PD-1 CSR T cells as a standalone therapeutic platform that expands the therapeutic window of PD-L1-targeted cellular therapy by preserving dual-compartment targeting of tumor and immunosuppressive myeloid cells while reducing normal-cell reactivity, providing a foundation for further clinical translation across solid tumors.

molecular biology↗

bioRxiv2024

Advancing CAR T-Cell Therapy: Simultaneously Attack Tumor and Immunosuppressive Cells in the Tumor Microenvironment

Chimeric antigen receptor (CAR) T-cell therapy has encountered limited success in solid tumors. The lack of dependable antigens and the immunosuppressive tumor microenvironment (TME) are major challenges. Within the TME, tumor cells along with immunosuppressive cells employ an immune-evasion mechanism that upregulates programmed death ligand 1 (PD-L1) to deactivate effector T cells; this makes PD-L1 a reliable, universal target for solid tumors. We developed a novel PD-L1 CAR (MC9999) using our humanized anti-PD-L1 monoclonal antibody, designed to simultaneously target tumor and immunosuppressive cells. The antigen-specific antitumor effects of MC9999 CAR T-cells were observed consistently across four solid tumor models: breast cancer, lung cancer, melanoma, and glioblastoma multiforme (GBM). Notably, intravenous administration of MC9999 CAR T-cells eradicated intracranially established LN229 GBM tumors, suggesting penetration of the blood-brain barrier. The proof-of-concept data demonstrate the cytolytic effect of MC9999 CAR T-cells against immunosuppressive cells, including microglia HMC3 cells and M2 macrophages. Furthermore, MC9999 CAR T-cells elicited cytotoxicity against primary tumor-associated macrophages within GBM tumors. The concept of targeting both tumor and immunosuppressive cells with MC9999 was further validated using CAR T-cells derived from cancer patients. These findings establish MC9999 as a foundation for the development of effective CAR T-cell therapies against solid tumors.

cancer biology↗