Abstract 3997: PARP inhibitors plus anlotinib as bridging therapy for TGFβ-insensitive CAR-T cell therapy targeting MSLN and CD19 in advanced ovarian cancer

Abstract

Abstract Background: The efficacy of chimeric antigen receptor (CAR) T cell therapy remains modest for the treatment of solid tumors due to restricted T cell infiltration and immunosuppressive tumor microenvironment (TME). Leveraging the window of opportunity between leukapheresis and infusion using bridging therapy might improve TME and potentiate CAR-T cell therapy. Here, we assessed the potential of poly (ADP-ribose) polymerase (PARP) inhibitors plus anlotinib as bridging therapy for CAR-T cells with resistance to TGFβ and capability of rapid expansion by bait-and-switch strategy of dual-targeting mesothelin (MSLN) and CD19 in preclinical models of advanced ovarian cancer. Methods: Immunocompetent mice bearing ID8 tumors were treated with niraparib (21 days) plus anlotinib (14 days) and euthanized at different timepoints (0, 7, or 14 days since discontinuation) to quantify tumor-infiltrating T cells and profile T cell functions. CAR-T cells transfected with dominant-negative TGFβRII dual-targeting MSLN and CD19 were produced by IASO Biotherapeutics. NSG mice bearing MSLN-positive cell- or patient-derived xenografts (CDX or PDX) of ovarian cancer received CAR-T cells alone or after bridging therapy (niraparib plus anlotinib followed by a wash-out period of 7 days). Tumor volume was balanced before CAR-T cell infusion. Replication-deficient NALM6 cells pre-treated with mitomycin C were injected to provide CD19 antigen. A PET scan that visualized granzyme B release was used to track CAR-T cells and assess immune-mediated tumor killing. Results: Niraparib combined with anlotinib increased tumor-infiltrating T cells without impairing T cell functionality. The effects of promoting T cell infiltration remained significant at 14 days after discontinuation, which might associate with lasting activation of cGAS-STING pathway and secretion of downstream chemokines (CXCL10 and CCL5), and normalized tumor vasculature featured by better perfusion and reduced leakage. The engineered CAR-T cells could resist TGFβ and displayed improved proliferation, cytotoxicity, cytokine release, and in vivo antitumor activities upon CD19 stimulation. Importantly, bridging therapy significantly increased CAR-T cell infiltration, curbed tumor growth, and prolonged survival in mice bearing SKOV3 CDX, HRD-negative PDX, and another multidrug-resistant PDX. PET imaging showed that bridging therapy increased tumor-infiltrating CAR-T cells and boosted tumor-killing capability. Conclusions: PARP inhibitors plus anlotinib as bridging therapy facilitated CAR-T cell infiltration and enhanced antitumor activities in multiple preclinical models of advanced ovarian cancer, and an early phase I trial (NCT05141253) is ongoing to evaluate PARP inhibitors plus anlotinib as bridging therapy for CAR-T cell therapy in patients with refractory MSLN-positive ovarian cancer. Citation Format: Huayi Li, Minghua Xiang, Jiahao Liu, Wei Mu, Li Zhu, Xuejiao Zhao, Gordon B. Mills, Qinglei Gao, Yong Fang. PARP inhibitors plus anlotinib as bridging therapy for TGFβ-insensitive CAR-T cell therapy targeting MSLN and CD19 in advanced ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3997.