Abstract CT069: Targeting EpCAM via CAR T-cells is an effective treatment for gastric cancer patients and subsequent toll-like receptor signaling activation in CD36+ monocyte underlies the resulting cytokine release syndrome

Abstract EpCAM is highly expressed in various cancer types of the gastrointestinal system and at metastatic sites. It serves as a promising prognostic marker and therapeutic target. We conducted a first-in-human, open-label, single-arm, multicenter, phase 1 clinical trial following the classical "3+3" dose escalation design. The endpoints of this clinical trial are to assess the safety, efficacy, and pharmacokinetic (PK)/pharmacodynamic (PD) profile of EpCAM CAR-T. The trial is still ongoing, and our interim analysis results revealed a favorable safety profile of EpCAM CAR-T. No treatment-related deaths were observed within the 4-week follow-up period after infusion. 2 (12.5%) patients in high dose group (3*106) experienced dose-limiting toxicity (DLT) and 8 (50%) patients experienced grade 1-3 CRS. EpCAM CAR-T showed promising efficacy in gastric cancer. In gastric cancer group, the overall response rate (ORR) and disease control rate (DCR) reached 20.0% and 90.0%, respectively. However, the efficacy of EpCAM CAR-T in treating colorectal cancer was suboptimal, with an objective response rate (ORR) of 0% and disease control rate (DCR) of 50%. In our study, we observed that patients in gastric cancer (GC) group who developed cytokine release syndrome (CRS) had a weak response to CAR-T cell therapy, which is consistent with previous observations in animal models. We employed single-cell RNA sequencing (scRNA-seq) to analyze peripheral blood mononuclear cells (PBMCs) from GC group patients receiving EpCAM CAR-T treatment to explore the potential antagonism between CRS and treatment efficacy. Our findings underscore the significant role of monocytes in the regulation of CRS and treatment response. Specifically, we identified an increased abundance of Toll-like receptor (TLR)-dependent CD36+ monocytes in non-responders experiencing CRS. In a mouse model, we demonstrated that blocking TLR signaling in monocytes attenuated CRS induced by EpCAM CAR-T cells. Conversely, CD16+ monocytes were enriched in responders, displaying upregulated antigen presentation pathways and enhanced tumor infiltration capacity. In vivo, experiments revealed that blocking the antigen presentation pathway or inhibiting tumor infiltration of CD16+ monocytes resulted in reduced anti-tumor response of EpCAM CAR-T cells. Our findings highlight the critical role of intrinsic monocyte subpopulations as determinants of CAR-T efficacy and CRS. These insights may provide valuable strategies for predicting and enhancing the safety and efficacy of CAR-T cell therapy for solid tumors. Citation Format: TIanhang Luo, Zhengmao Lu, Zhongen Wu, Yuxuan Dong, Yuanyuan Zhu, Mei Feng, Shenglin Mei, Weijia Fang, Di Zhu. Targeting EpCAM via CAR T-cells is an effective treatment for gastric cancer patients and subsequent toll-like receptor signaling activation in CD36+ monocyte underlies the resulting cytokine release syndrome [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT069.