Abstract LB341: Clinical validation and mechanistic insights of ThisCART: A novel allogeneic platform enhancing CAR-T signaling via intracellular TCRαβ/CD3 retention

Abstract

Abstract Background: Current allogeneic CAR-T cell therapies face challenges with post-infusion expansion and efficacy. In response, we developed ThisCART, a non-genetic editing, allogeneic platform that significantly enhances CAR-T cell expansion and efficacy. This is achieved through a novel approach of intracellular retention of membrane proteins, reducing surface expression of TCRαβ/CD3 complexes and HLA-I molecules. Our lead product, ThisCART19, has demonstrated superior efficacy compared to conventional AutoCART19 in preclinical and early clinical studies for B-ALL. Methods: In the clinical trial NCT04384393, we assessed the safety and efficacy of ThisCART19 in patients with B-cell malignancies. Post-lymphodepletion, participants received infusions of ThisCART19 and AutoCART19, both personalized from the patient's own T cells, in equal proportions. Safety and efficacy were the primary endpoints, evaluated on Day 28 post-infusion and throughout extended follow-up. Mechanistic insights were gained through comprehensive multi-omics studies, including RNAseq, whole-cell proteomics, and phosphoproteomics. Results: ThisCART19 showed enhanced expansion and an improved safety profile in vivo. As of 01 January 2024, Two patients diagnosed as relapse/refractory acute B cell leukemia (R/R B-ALL) were enrolled in the clinical trial. Pt1 is a 55yo male with Ph-positive B-ALL (36% blasts) who relapsed after multiagent chemotherapy and TKIs. Pt2 is a 16yo male with CNS leukemia (78.5% blasts) after multiagent chemotherapy. No DLTs or ICANS were observed. Pt1 experienced Grade 1 CRS that resolved without treatment, and Pt2 experienced Grade 2 CRS that resolved after tocilizumab and corticosteroids. Complete remission with MRD-negative status was achieved by Day 28. Pharmacodynamic analysis indicated a significant expansion of CAR-T cells, predominantly in the CAR+TCR- subset, highlighting autonomous CAR signaling enhancement. Multi-omics analysis identified upregulation in JAK-STAT, PI3K-Akt, and NFKB pathways, suggesting improved cell proliferation, survival, anti-apoptotic activity, and effector function. This molecular profiling provides a mechanistic understanding of ThisCART19A's therapeutic efficacy. Conclusion: The ThisCART platform marks a transformative advancement in allogeneic CAR-T cell therapy. By enhancing CAR signaling autonomously through a unique intracellular retention of TCRαβ/CD3 complexes, ThisCART has shown promising safety and efficacy in early clinical trials. Its potential in reshaping the treatment landscape for hematological and autoimmune disorders positions ThisCART as a crucial development in cellular therapeutics. Citation Format: Jun Li, Lei Xue, Sujun Li, Ling He, Kaichun Liu, Rong Jin, Tao Wang, Yinhang Zhang, Shanshan Chen, Yulian Gao, Dan Liu, Liyun Yang, Xingbing Wang. Clinical validation and mechanistic insights of ThisCART: A novel allogeneic platform enhancing CAR-T signaling via intracellular TCRαβ/CD3 retention [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 LB341.