Abstract 1332: Allogeneic CD19-directed CAR-iNKT cells and their phenotypic subsets for the treatment of CD19+ hematological malignancies

Abstract Invariant Natural Killer T (iNKT) cells are a unique subset of innate lymphocytes, constituting 1% of human T cells. iNKT cells express a semi-invariant TCR (iTCR) recognizing glycolipids presented by the monomorphic, MHC-like molecule CD1d. Previous studies indicate that due to distinctive TCR constitution and antigen recognition properties, iNKT cells do not induce acute graft-versus-host disease. Based on the CD4 and CD8 expression, mature human iNKT cells can be classified into CD4+CD8-, CD4-CD8- 99% purity from healthy donors' peripheral blood and were transduced with a CD19 CAR-encoding 3rd generation lentivirus. After expansion, the CAR19-iNKT cells were cryopreserved and later analyzed post-thawing. Differential expression of CD27 and PD1 was noted in CAR+CD4+ and CAR+CD4- iNKT cells compared to other markers. For functional profiling, CAR+CD4+ iNKT cells were positively selected, and 24h cytotoxicity assays were performed using several tumor cell lines including SEM, Ramos and C1R-CD1d (+/- α-GalCer). The CAR+CD4- iNKT cells exhibited superior cytotoxicity to multiple tumor cell lines compared to that of CAR+CD4+ iNKT cells from two donors. However, both subsets lysed α-GalCer pulsed C1R-CD1d cells in a comparable manner indicating the potential of these subsets to recognize antigen through the iTCR. Subsequently, we assessed the proliferation ability of the CAR+CD4+ and CAR+CD4- subsets by exposing the cells to three rounds of stimulation, 24h apart, using SEM (CD19+CD1d-) or K562 (CD19-CD1d-) tumor cells with or without IL-15. Proliferation was assessed seven days following the first stimulation. The CAR+CD4+ subset of CAR19-iNKT cells demonstrated faster proliferation than CAR+CD4- cells in the presence of IL-15 after repeated exposure to tumor cells. Ongoing RNA seq analysis of CAR+CD4+/CAR+CD4- cells will further elucidate differences between these subsets. The outcomes of these studies have shown encouraging results, indicating the potential benefit of having diverse subsets among CAR19-iNKT cells for treating CD19+ cancers. The therapeutic potential of CAR+CD4+ iNKT cell subset could be enhanced to match that of CAR+CD4- subset with the use of α-GalCer. In summary, inclusion of both CD4+ and CD4- iNKT cells is critical for the functionality of allogeneic CAR-iNKT cell therapy. Extensive characterization is crucial for clinical translation, but additional research, including preclinical and clinical trials, is essential to determine the safety and effectiveness of CAR19-iNKT cell therapy in real-world applications. Citation Format: Kanagaraju Ponnusamy, Simon Poon, Nicole van der Weerden, Robson Dossa, Michael J. Baker, Mini Bharathan, Anastasios Karadimitris. Allogeneic CD19-directed CAR-iNKT cells and their phenotypic subsets for the treatment of CD19+ hematological malignancies 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 (6Suppl): Abstract nr 1332.