Abstract 586: Orthogonal IL-2/IL-2RB signaling in adoptively transferred T cells controls tumor growth without the need for lymphodepletion in a B16 tumor model
Authors: Kochel Christina , Sun Meng , Ratti Navneet , Vivona Sandro , Ramadass Mahalaksmi , Semana Marie , Bauer Michele , Ali Mohammed , Emmerich Jan , Kastelein Rob , Lupardus Patrick J. , Aspuria Paul-Joseph , Oft Martin 
Published: June 2022

Abstract
Multiple adoptive T-cell therapy modalities (ACT) have delivered promising clinical responses in cancer patients. However, challenges including poor T cell effector function, lack of proliferation, and limited persistence have prevented ACTs from reaching their full curative potential. In addition, ACTs typically require lymphodepletion to aid cell engraftment. Lymphodepletion has been shown to improve persistence and efficacy of ACTs by elevating T-cell common gamma-chain cytokines like IL-7 and IL-15. However, lymphodepletion regimens have been identified as a risk factor for cytokine release syndrome (CRS) and infectious complications from opportunistic pathogens. IL-2, another common gamma-chain cytokine, is a potent stimulator of T cells, making it an attractive cytokine to support ACT and potentially bypass the need for lymphodepletion. However, therapeutic use of IL-2 is limited by systemic toxicity due its promiscuous activation of immune cells.
To facilitate selective delivery of an IL-2 signal to engineered T cells and avoid signaling in bystander T cells and NK cells, we developed a mouse orthogonal receptor/ligand system consisting of a mutated IL-2 Receptor Beta (moRβ) and a pegylated, IL-2 mutein (moIL-2) that does not significantly activate the wild type IL-2β receptor but does activate moRβ. T cells from pmel-1 T cell receptor-transgenic mice, recognizing gp100 on B16 melanoma cells were transduced with moRβ (orthoPmel). A highly active moIL-2 was continuously dosed for four weeks in mice. Thy1.1+ orthoPmel T cells were tracked by FACS and IHC systemically and in the tumor.
During orthoPmel manufacturing, moIL-2 specifically enriched orthoPmel compared to mouse WT IL-2. OrthoPmel in combination with moIL-2 controlled tumor growth in lymphoreplete mice bearing established B16 tumors while neither component alone inhibited tumor growth. moIL-2 significantly expanded orthoPmel systemically and intratumorally, with orthoPmel ultimately accounting for greater than 80% or 40% of all peripheral and intratumoral T cells, respectively. Systemic orthoPmel maintained a consistent central memory and effector memory mix throughout the four-week moIL-2 treatment course. moIL-2 also induced the expression of activation markers, CD25 and Granzyme B, in intratumoral orthoPmel.
These findings validate than an orthogonal IL-2/IL-2Rβ platform can enhance efficacy of ACTs without peripheral expansion or activation of NK cells or non-tumor specific T cells and the toxicities typically associated with high dose IL-2 therapy. Importantly, these results demonstrate the potential of this platform overcome the requirement of lymphodepletion in adoptive cell therapies.
Citation Format: Christina Kochel, Meng Sun, Navneet Ratti, Sandro Vivona, Mahalaksmi Ramadass, Marie Semana, Michele Bauer, Mohammed Ali, Jan Emmerich, Rob Kastelein, Patrick J. Lupardus, Paul-Joseph Aspuria, Martin Oft. Orthogonal IL-2/IL-2RB signaling in adoptively transferred T cells controls tumor growth without the need for lymphodepletion in a B16 tumor model [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 586.