Abstract 10: Non-viral engineered T cell therapy specific for the hotspot mutation p53 R175H that integrates signal 1 (TCR), signal 2 (co-stimulation) and signal 3 (cytokine) and co-opts FasL-dependent apoptosis to achieve a coordinated antitumor CD4/8 T cell response
Authors: Narayan Santosh , Gareau Ken , Gupta Ankit , Ferrell Josh , Rouillard Nicholas , Warner Tyler , Liang Jinsheng , Shen Luhua , Tetrault Tanya , Francis Joshua , He Xingyue , Browne Patrick J. , Lamothe Rebecca , Storlie Meghan D. , Cost Gregory J. , Schmitt Thomas M. , Greenberg Philip D. , Chandran Smita S. , Hallet Damien , Gormally Michael , Klebanoff Chistopher A. , Shapiro Gary , Nguyen Kim , Vincent Loïc 
Published: March 2024

Abstract
Adoptive T cell therapy (ACT) has demonstrated antitumor efficacy in patients with solid cancers but requires further optimization to become a reproducibly effective treatment. T cell receptor (TCR)-engineered T cells recognize peptides derived from intracellular and surface proteins presented in the context of MHC class I. Targeting mutated oncogenic drivers addresses many of the major obstacles of this modality, in that the antigenic epitope is: 1) tumor-specific, 2) essential for tumor survival, and 3) derived from a stably expressed protein. However, the immune-suppressive tumor microenvironment makes further optimization of engineered T cells necessary to bring long-term clinical benefit to patients. For an optimal anti-tumor response, T cells require three signals: TCR, co-stimulation, and cytokine signaling. The tumor suppressor TP53 is the most frequently mutated gene across human cancers, with a highly recurrent arginine to histidine hotspot alteration in codon 175 leading to novel tumor-dependent functions. Here we report the use of a novel CRISPR-Cas nuclease system to knock-in a six-parameter multi-cistronic cassette into the TRAC locus with high efficiency. We employed several strategies to maximize the potency and durability of a TCR-T cell product targeting the p53 R175H oncogenic driver, including: 1) A high-affinity TCR (α and β chains) specific for the p53 R175H mutation presented by HLA-A*02:01 permits the recognition of tumor cells expressing even low levels of the epitope (Signal 1), 2) Inclusion of the CD8αβ co-receptor drives stimulation of CD4+ T cells with the MHC class I restricted TCR, allowing for a physiologic coordinated immune response required for maximal efficacy, 3) A FAS-41BB switch receptor acts as a dominant negative to the FASL-inducing apoptotic signal in the tumor microenvironment and drives stimulation and persistence of the T cell product via 41BB co-stimulatory signaling (Signal 2), 4) A chimeric cytokine receptor (constitutive Interleukin Receptor) promotes expansion and survival while avoiding immunologic exhaustion (Signal 3). Together, these strategies deliver the three signals required for maximal T cell function: antigen-driven activation, co-stimulation, and growth/survival-promoting cytokine signaling. The non-viral TRAC-knocked-in T cells demonstrate robust and specific cytotoxicity against endogenously expressing HLA-A*02:01 and p53 R175H cell lines in vitro and effective anti-tumor activity in vivo while maintaining a favorable preclinical safety profile. These data support the planned clinical development of a novel non-viral TRAC-knocked-in T cell therapy for the treatment of p53 R175H-mutant solid tumors.
Citation Format: Santosh Narayan, Ken Gareau, Ankit Gupta, Josh Ferrell, Nicholas Rouillard, Tyler Warner, Jinsheng Liang, Luhua Shen, Tanya Tetrault, Joshua Francis, Xingyue He, Patrick J. Browne, Rebecca Lamothe, Meghan D. Storlie, Gregory J. Cost, Thomas M. Schmitt, Philip D. Greenberg, Smita S. Chandran, Damien Hallet, Michael Gormally, Chistopher A. Klebanoff, Gary Shapiro, Kim Nguyen, Loïc Vincent. Non-viral engineered T cell therapy specific for the hotspot mutation p53 R175H that integrates signal 1 (TCR), signal 2 (co-stimulation) and signal 3 (cytokine) and co-opts FasL-dependent apoptosis to achieve a coordinated antitumor CD4/8 T cell response [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(6_Suppl):Abstract nr 10.