Abstract 1791: Next generation UltraCAR-T® cells with intrinsic checkpoint inhibition and overnight manufacturing overcome suppressive tumor microenvironment leading to sustained antitumor activity (2023)

Abstract The UltraCAR-T® platform, with decentralized overnight manufacturing, has shifted the autologous CAR-T manufacturing paradigm. This disruptive approach has been validated in clinical and pre-clinical studies for both hematologic and solid tumors. UltraCAR-T cells, manufactured using an overnight process with minimal ex vivo manipulation of autologous T cells. UltraCAR-T cells are engineered to co-express CAR, membrane bound IL-15, and kill switch genes using non-viral gene transfer via high-throughput UltraPorator™ system. Multigenic design and overnight manufacturing renders UltraCAR-T cells with enhanced in vivo expansion and persistence for durable antitumor activity. Chronic antigen stimulation from the tumor can lead to CAR T having an exhausted phenotype contributing to treatment failures. Next generation UltraCAR-T cells also incorporate a novel cell intrinsic blockade of PD-1, superseding the need for combination therapy with checkpoint inhibitors and mitigate classic T cell exhaustion that occurs from chronic stimulation, thereby expanding the therapeutic window for efficacy. Using mesothelin (MSLN) as an exemplar from the CAR-target library, we developed a robust in vitro and in vivo model of continuous tumor antigen exposure to evaluate antitumor activity of the UltraCAR-T cells. MSLN UltraCAR-T cells were generated with and without intrinsic PD-1 blockade. In vitro, UltraCAR-T cells with intrinsic PD-1 blockade demonstrated enhanced inflammatory cytokine expression and cytotoxicity at low effector:target ratios. In long-term co-culture assays with recurring challenge of MSLN+ PD-L1+ tumor cells every 2-3 days, UltraCAR-T cells with intrinsic PD-1 blockade showed sustained potent cytotoxicity which was superior to CAR-T cells lacking PD-1 blockade and in combination with αPD-1 antibody. Intrinsic PD-1 blockade markedly enhanced polyfunctionality of UltraCAR-T cells in the presence of MSLN+ PD-L1+ tumor. In xenograft solid tumor model, a single administration of MSLN UltraCAR-T cells manufactured using UltraPorator demonstrated significant antitumor efficacy. Blood analysis showed sustained downregulation of PD-1, robust antigen specific expansion and durable persistence with central memory/stem-cell memory as the dominant phenotype of UltraCAR-T in vivo. Rechallenging the mice, who became tumor-free after a single UltraCAR-T infusion, with tumor for a second time to simulate tumor relapse led to the significant reduction in tumor burden without additional UltraCAR-T treatment. Collectively, these pre-clinical data highlight the improved efficacy of intrinsic PD-1 blockade in next generation UltraCAR-T cells using non-viral gene delivery and an established rapid, decentralized manufacturing process. Citation Format: Giorgio Zenere, Carol Poortman, Afreen Sayed, Devi Gunasekera, Cheryl Bolinger, Pooja Chauhan, Jacques Plummer, Shamim Ahmad, Rutul R. Shah, Helen Sabzevari, Douglas E. Brough, Tim Chan. Next generation UltraCAR-T® cells with intrinsic checkpoint inhibition and overnight manufacturing overcome suppressive tumor microenvironment leading to sustained antitumor activity [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 1791.