Th146 - Type-2 Functionality in Sustaining CAR T Cell Longevity Linked to 8-Year Leukemia Remission

Bing Feng – École Polytechnique Fédérale de Lausanne; Susan McClory – Children’s Hospital of Philadelphia; Caroline Diorio – Children’s Hospital of Philadelphia; Beatriz Oliveira – Cleveland Clinic; Bo Tao – Yale University; Li Tang – École Polytechnique Fédérale de Lausanne; J. Joseph Melenhorst – Cleveland Clinic; Carl June – University of Pennsylvania; Stephan Grupp – Children’s Hospital of Philadelphia; Rong Fan – Yale University

Abstract Text: Despite a high response rate in chimeric antigen receptor (CAR) T therapy for acute lymphocytic leukemia (ALL), ~50% of patients relapse within the first year, representing an urgent question to address in the next stage of cellular immunotherapy. To investigate the molecular determinants of ultra-long CAR T persistence, we obtained single-cell multi-omics sequencing data from >1 million pre-infusion CAR T cells from 82 pediatric ALL patients enrolled in the first two CAR T ALL clinical trials and 6 healthy donors. Our analysis revealed a notable role of type-1 function, which was highly represented but showed no discernible correlation with CAR T persistence. Surprisingly, we identified that elevated type-2 functionality in CAR T infusion products was significantly associated with patients maintaining a median B-cell aplasia duration of 8.4 years. Ligand-receptor interaction analysis uncovered that type-2 cytokines regulated terminal effector cells showing dysfunctional signatures. In vitro functional studies showed that adding IL-4 during CAR-specific activation alleviates CAR T cell dysfunction and enhances functional fitness. Serial proteomic profiling of post-infusion sera from patients revealed a higher level of circulating type-2 cytokines in 5-year or 8-year relapse-free responders. In a leukemic mouse model, type-2 high CAR T cell products demonstrated superior expansion and antitumor activity particularly upon leukemia rechallenge. Additionally, the restoration of antitumor efficacy in type-2 low CAR T cells was attainable by augmenting their type-2 functionality. Our findings underscores an unexpected role of type-2 functionality in maintaining a balanced homeostatic state within the entire CAR T population associated with ultra-long-term complete remission.