PD-1 and TIGIT downregulation distinctly affect the effector and early memory phenotypes of CD19-targeting CAR T cells.

CD19-targeting chimeric antigen receptor (CAR) T cells have become an important therapeutic option for patients with relapsed and refractory B cell malignancies. However, a significant portion of patients still do not benefit from the therapy owing to various resistance mechanisms, including high expression of multiple inhibitory immune checkpoint receptors. Here, we report a lentiviral two-in-one CAR T approach in which two checkpoint receptors are downregulated simultaneously by a dual short hairpin RNA cassette integrated into a CAR vector. Using this system, we evaluated CD19-targeting CAR T cells in the context of four different checkpoint combinations-PD-1/TIM-3, PD-1/LAG-3, PD-1/CTLA-4, and PD-1/TIGIT-and found that CAR T cells with PD-1/TIGIT downregulation uniquely exerted synergistic antitumor effects. Importantly, functional and phenotypic analyses suggested that downregulation of PD-1 enhances short-term effector function, whereas downregulation of TIGIT is primarily responsible for maintaining a less differentiated/exhausted state, providing a potential mechanism for the observed synergy. The PD-1/TIGIT-downregulated CAR T cells generated from diffuse large B cell lymphoma patient-derived T cells also showed robust antitumor activity and significantly improved persistence in vivo. The efficacy and safety of PD-1/TIGIT-downregulated CD19-targeting CAR T cells are currently being evaluated in adult patients with relapsed or refractory large B cell lymphoma (ClinicalTrials.gov: NCT04836507).

Redirection of CAR-T Cell Cytotoxicity Using Metabolic Glycan Labeling with Unnatural Sugars.

T cells expressing chimeric antigen receptors (CAR-T cells) have shown unprecedented clinical responses against hematological malignancies. However, some patients relapse after CAR-T cell therapy due to antigen-negative escape variants. Additionally, CAR-T cell therapies showed limited clinical efficacy in solid tumors with high antigen heterogeneity. To overcome this, we metabolically labeled the glycans on cancer cells to redirect CAR-T cell cytotoxicity regardless of the endogenous antigen expression status of the cancer cells. We found that modifying cancer cells with N-azidoacetylmannosamine and bicyclo[6.1.0]non-4-yne-fluorescein isothiocyanate can elicit selective and durable cytotoxicity of anti-FITC CAR-T cells. Furthermore, we demonstrated that dinitrophenyl-conjugated sialic acid (Sia-DNP) generated DNP-modified glycans on cancer cells in situ that could be effectively targeted by anti-DNP CAR-T cells to eradicate established tumors in xenograft models. Our study illustrates that metabolic glycan labeling using unnatural sugars can be combined with CAR-T cell therapy to provide novel cancer immunotherapy for solid tumors that lack viable target antigens.