Enhancing CAR T Cell Efficacy By Modulating PI3K Signaling Via a Synthetic CD28 Rheostat

作者：Sanam Shahid, Winson Cai, Erin R. Burns, Jasmine S. Um, Serena Mathew, Sydney Souness, Sarah Yoo, Bingyi Chen, T Fujino, Renier J. Brentjens, Anthony F. Daniyan · 发表于：Blood · 年份：2024 · DOI：10.1182/blood-2024-209964 · 被引用次数：6 · 研究领域：CAR-T cell therapy research、Monoclonal and Polyclonal Antibodies Research、Chronic Lymphocytic Leukemia Research

Introduction: CD28 is a costimulatory protein incorporated into two FDA-approved second-generation CD19-directed CAR T cell products and utilized extensively preclinically. Within CAR T cells, CD28 induces complex signaling including activation of the PI3K/AKT/mTOR pathway, with ingrained signaling redundancies. Although PI3K signaling enhances proliferation, excessive growth signals may lead to T cell exhaustion and terminal differentiation, correlating with suboptimal clinical responses. Importantly, PI3K and AKT inhibitors have been used to modulate CAR T cell signaling, enriching memory-like and reducing highly differentiated T cells, leading to a more potent cellular product. We aimed to attenuate CD28 signaling redundancies through the development of a “synthetic rheostat” that tempers PI3K/AKT/mTOR pathway signaling. Methods:We mutated CD28 to reduce PI3K signaling and assessed the function of this mutant (referred to as SAVVY) compared to a native CD28 in second-generation CD19-targeting CAR T cells against NALM6, a B cell acute lymphoblastic leukemia (B-ALL) cell line. CD19-targeting CAR T cells were produced by gammaretroviral transduction of peripheral blood-derived primary T cells. In vitro, we evaluated CAR T cell proliferation, target lysis, CAR recycling, T cell mitochondrial mass/function, T cell immunophenotype (memory/exhaustion), and T cell cytokine secretion. In vivo, we evaluated tumor control and overall survival in cell-line derived xenograft murine mod...