Abstract 2824: Engineered human IL-2/IL-2Rb orthogonal pairs selectively enhance anti-GPC3 CAR T cells to drive complete responses in solid epithelial tumor models
Authors: Aspuria Paul-Joseph , Semana Marie , Vivona Sandro , Ramadass Mahalaksmi , Ratti Navneet , Riener Romina , Bauer Michele , Ali Mohammed , Rokkam Deepti , Kastelein Rob A. , Lupardus Patrick J. , Oft Martin 
Published: June 2022

Abstract
CAR T cell therapy has demonstrated clinical efficacy against hematological malignancies. However, prominent barriers including poor T cell effector function, lack of proliferation, and limited CAR T cell persistence have prevented CAR T cell therapies from reaching their full curative potential, especially in solid tumors. Interleukin-2 (IL-2) is a potent stimulator of T cell proliferation, survival, and cytotoxic function, thereby making it an attractive cytokine to support CAR T cell therapy. However, therapeutic use of IL-2 is limited by systemic toxicity due its promiscuous activation of undesired immune cell populations, including non-tumor reactive T cells and NK cells.
To facilitate selective ex vivo and in vivo expansion of engineered T cells we have developed a human orthogonal (ortho) ligand/receptor system consisting of a IL-2 mutein (STK-009) that does not significantly stimulate cells expressing wild type IL-2 receptor and a mutated IL-2 Receptor Beta (orthoIL-2Rβ) that responds to STK-009 but not wild type IL-2. This system enables in vivo IL-2 signaling in engineered cells that express the orthoIL-2Rβ while avoiding stimulation of native T cells and NK cells. Previously, we demonstrated the ability of the STK-009/orthoIL-2Rβ receptor pair to selectively enhance the anti-tumor efficacy of orthoIL-2Rβ (hoRb) expressing CD19 CAR T cells (SYNCAR-001) in preclinical lymphoma mouse models. We also demonstrated that STK-009 is selective for the orthoIL-2Rβ expressing cells and therefore in a non-human primate model does not stimulate native T or NK cells.
Here, we demonstrate the ability of the STK-009/hoRb system to enhance the anti-tumor activity and persistence of anti-glypican 3 (GPC3) CAR T cells. GPC3 overexpression is associated with various malignancies such as hepatocellular carcinoma (HCC), pediatric sarcomas, and non small cell lung carcinoma (NSCLC). Clinical trials of GPC3 CAR T therapy are ongoing, but early data suggests a need to boost CAR T cell function and persistence to achieve significant clinical responses. We incorporated the hoRb downstream of an anti-GPC3_28z CAR via a T2A cleavage peptide (SYNCAR-002). In vivo, STK-009 administration enhanced the anti-tumor efficacy of SYNCAR-002 in highly aggressive subcutaneous and intraperitoneal HCC models. STK-009 treatment resulted in significant expansion of SYNCAR-002 and drove infiltration of SYNCAR-002 into tumors. STK-009 treatment also induced intratumoral granzyme B+ and IFN-γ+ production by SYNCAR-002 indicating activation of effector T cell function.
These findings validate that the orthogonal IL-2 platform has the potential to improve the efficacy and durability of CAR T therapy for solid tumor targets such as GPC3 by selectively expanding CAR-T cells in vivo, driving CAR-T cells into the tumor, and activating CAR-T cells in the tumor microenvironment.
Citation Format: Paul-Joseph Aspuria, Marie Semana, Sandro Vivona, Mahalaksmi Ramadass, Navneet Ratti, Romina Riener, Michele Bauer, Mohammed Ali, Deepti Rokkam, Rob A. Kastelein, Patrick J. Lupardus, Martin Oft. Engineered human IL-2/IL-2Rb orthogonal pairs selectively enhance anti-GPC3 CAR T cells to drive complete responses in solid epithelial tumor models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2824.