Abstract 2918: In vivo delivery of CD3-directed CD19-CAR lentivectors leads to the generation of CAR T and NK-like (CAR-TaNK) cells capable of complete ablation of B cells in the blood, bone marrow, and tissue of NSG-SGM3 CD34+ humanized mice (2023)

Abstract Introduction: Direct in vivo delivery of lentiviral vectors (LV) to generate CD19 CAR+ cells without the need for ex vivo preparation represents a promising approach to transform autologous CAR therapy into an off-the-shelf treatment. In these studies, direct administration of a new LV encoding a CD19 CAR into humanized NOD SCID gamma (NSG) mice expressing human IL-3, GM-CSF, and SCF (NSG-SGM3) resulted in a dose-dependent elimination of B cells in the peripheral blood, peritoneal fluid, bone marrow, and tissue of treated mice. Methods: CD3-directed LV encoding a CD19 CAR with a novel synthetic driver element was manufactured utilizing a 25L clinical scale suspension-based process. NSG-SGM3 mice transplanted with human CD34+ cells from cord blood were injected with LV doses (1E6 IU, 1E7 IU, or 5E7 IU) intraperitoneally (IP) or 1E7 IU intravenously (IV). Quantification of CD19 CAR+ cells and CD20+ B cells in peripheral blood, peritoneal fluid, and bone marrow was assessed by flow cytometry. Additionally, immunohistochemical analysis was performed to evaluate the tissue-resident human B cells and for any other histopathological observations following test article administration. Results: All CD34+ humanized NSG-SGM3 mice were confirmed to exhibit efficient human hematopoietic engraftment by flow cytometry prior to test article administration (peripheral blood hCD45: 68.9% ± 4.93%; hCD19+ B cells: 53.7% ± 5.11%). Direct LV administration at the 1E7 IU and 5E7 IU doses demonstrated a dose-dependent reduction in circulating human B cells compared to the control and 1E6 IU dose (p &amp;lt; 0.05). The synthetic driver elements co-expressed with the CAR led to the formation of unique CD3+ CD8+ CD56+ T and NK-like (TaNK) CD19 CAR+ cells in circulation. The 1E7 IU IP dose demonstrated ablation of B cells (total cells/uL) in peripheral blood (control: 9.67 ± 3.72 vs. LV treated: 0.157 ± 0.117), intraperitoneal fluid (control: 0.322 ± 0.244 vs. LV treated: 0.038 ± 0.029), bone marrow (control: 9.16± 1.83 vs. LV treated: 0.734 ± 0.864), and splenic tissue. Both IP and IV routes of administration showed significant B cell depletion at the 1E7 IU dose. However, complete B cell elimination in splenic tissue was only observed at the 5E7 IU dose. Non-treated CD34+ humanized NSG-SGM3 mice exhibited hepatic portal inflammation and moderate graft-versus-host disease (GVHD) in the colon. Interestingly, mice treated with LV encoding CD19 CAR exhibited decreased inflammatory pathology, suggesting potential B cell involvement in the inflammatory response in this model. Conclusion: In this study, direct in vivo delivery of LV encoding CD19 CAR resulted in the generation of functionally active CD19 CAR TaNK cells capable of eliminating target B cells in peripheral blood, peritoneal fluid, bone marrow, and tissue. Citation Format: Frederic Vigant, Ani Kundu, Ramya Yarlagadda, Cody Gowan, Michael Betts, Jonathan Kato, Renata Soares, Alan Ponce, Lintao Liu, Junyi Zhang, Ewa Jaruga-Killeen, Michelle Andraza, Suraj Kachgal, Gregory Schreiber, Wei Zhang, Gregory Wade, Gregory I. Frost, Sid P. Kerkar. In vivo delivery of CD3-directed CD19-CAR lentivectors leads to the generation of CAR T and NK-like (CAR-TaNK) cells capable of complete ablation of B cells in the blood, bone marrow, and tissue of NSG-SGM3 CD34+ humanized mice [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2918.