Abstract 2070: Differentiating PD-1+TCF-1+ stem-like resource CD8 T cells towards a distinct effector Tcell population with enhanced anti-tumor potential by delivering an engineered IL-2 variant to PD-1 via cis-targeting
Authors: Karagianni Maria , Varypataki Eleni Maria , Nicolini Valeria , Münz Christian , Umana Pablo , Klein Christian , Deak Laura Codarri 
Published: June 2022

Abstract
PD1-IL2v is a novel immunocytokine constituted by a high affinity bivalent blocking PD-1 antibody and a heterodimeric silent Fc-part fused to a monomeric IL-2 variant (IL2v). In contrast to wildtype IL2, IL2v does not bind to CD25 (IL2Ra) and, therefore, the preferential targeting of T regulatory cells (Tregs) and endothelial cells through CD25 is abolished. The PD-1 antibody, having ca. 50-fold higher affinity than IL2v, dictates the preferential cis-delivery of IL2v to PD-1 positive T cells, such as antigen-experienced tumor-reactive T cells. In addition, due to the reduced expression levels of PD-1 on Tregs compared to CD8 and conventional T cells, PD1-IL2v preferentially binds to the latter in vitro and ex vivo, rescuing them from Treg-mediated suppression. To assess the effects of the cis-delivery of IL2v to PD-1+ T cells in vivo, we applied subcutaneous B16F10-OVA and Panc02-H7-Fluc tumor models in syngeneic mice. PD1-IL2v lead to significantly improved survival of the B16F10-OVA tumor bearing and tumor regression in the Panc02-H7-Fluc tumor bearing mice. The OVA-specific CD8 T cells expressed the highest amount of PD-1 in the tumor microenvironment, and PD1-IL2v not only increased the total number of CD8 tumor infiltrating lymphocytes (TILs), but, more importantly, it expanded the OVA-specific T cells. The recently discovered PD-1+ TCF1+ stem-like or resource T cells responsible for the proliferative burst following anti-PD-1 therapy, correlate with clinical responses and better prognosis. However, stem-like T cells ultimately differentiate into terminally exhausted T cells resulting in relapses and tumor growth. Here, we show that PD1-IL2v targets OVA-specific stem-like T cells, and leads to their expansion and differentiation into a unique population of effector CD8 T cells, so-called “fresh and better effectors”. These cells have a distinct phenotypic and molecular signature in addition to diverse TCR clonality in comparison to the terminally exhausted CD8 TILs generated by anti-PD1 therapy alone or in combination with a non-cis targeted FAP-IL2v immunocytokine. Thus, PD1-IL2v is a differentiated immune cell-targeted IL2v, which promotes an effective and long-term anti-tumor immune-response by delivering IL-2v to PD-1+ tumor-specific T cells, like stem-like T cells, and by generating a distinct effector T cell population.
Citation Format: Maria Karagianni, Eleni Maria Varypataki, Valeria Nicolini, Christian Münz, Pablo Umana, Christian Klein, Laura Codarri Deak. Differentiating PD-1+TCF-1+ stem-like resource CD8 T cells towards a distinct effector Tcell population with enhanced anti-tumor potential by delivering an engineered IL-2 variant to PD-1 via cis-targeting [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 2070.