CLDN18.2-CAR-T (Integral Molecular)

Chimeric antigen receptor (CAR)-T cell therapy has achieved remarkable success in hematologic malignancies but faces significant limitations in gastrointestinal tumors due to the immunosuppressive tumor microenvironment (TME). Indoleamine 2,3-dioxygenase 1 (IDO1), a key enzyme in the TME, suppresses T cell efficacy by catalyzing tryptophan degradation to kynurenine (Kyn), leading to T cell exhaustion and reduced cytotoxicity. This study investigates the role of IDO1 inhibition in overcoming metabolic suppression by kynurenine and enhancing Claudin18.2 (CLDN18.2) CAR-T cell therapy in gastric and pancreatic adenocarcinoma models.

We evaluated the impact of genetic knockdown and pharmacological inhibition of IDO1 (using epacadostat) on CAR-T cell functionality, including cytokine production and exhaustion marker expression. The effects of fludarabine and cyclophosphamide preconditioning on IDO1 expression, CAR-T cell infiltration, and antitumor activity was also examined. In vivo tumor models of gastric and pancreatic adenocarcinomas were used to assess the efficacy of combining IDO1 inhibition with CLDN18.2-CAR-T therapy.

IDO1 inhibition significantly enhanced CAR-T cell function by increasing cytokine production, reducing exhaustion markers by decreasing TOX expression and improving tumor cell lysis. Preconditioning with fludarabine and cyclophosphamide further suppressed IDO1 expression in the TME, facilitating enhanced CAR-T cell infiltration. In vivo studies demonstrated that combining IDO1 inhibition with CAR-T therapy led to robust tumor growth suppression and prolonged survival in gastric and pancreatic tumor models.

Targeting IDO1 represents a promising strategy to overcome immunosuppressive barriers in gastrointestinal cancers, improving the efficacy of CLDN18.2-CAR-T therapy. These findings highlight the potential for integrating IDO1 inhibition into CAR-T treatment regimens to address resistance in treatment-refractory cancers.

Pancreatic ductal adenocarcinoma (PDAC) is one of the most poorly prognostic digestive tract malignancies. CLDN18.2 CAR-T therapy has recently shown promising clinical effects in PDAC. Radiotherapy, a traditional treatment, can induce systemic immune activation and abscopal effects. However, the synergistic effect and mechanism of their combination in PDAC treatment remain poorly understood. In this study, we developed a CLDN18.2-specific CAR-T and applied it to unilateral and bilateral mouse tumor models. Our results demonstrated that this synergy therapy not only improved tumor-killing effects in unilateral tumor-bearing mice but also induced regression in both local and distant tumors in bilateral tumor models. Mechanistically, early radiation-induced apoptosis promoted the proliferation of CD8 + T cells, while increased chemokine CCL2 levels from localized and distant tumor sites facilitated CAR-T and endogenous T cell infiltration, leading to systemic tumor suppression. This study proposes a promising approach for treating metastatic pancreatic cancer by combining radiotherapy and CAR-T therapy, elucidating the mechanism of CAR-T cell-enhanced radiotherapy effects ex vivo, and highlighting a novel strategy for combating metastatic pancreatic cancer.