SAR-444245, an engineered not-alpha IL-2 leveraging synthetic biology, modulates critical components of the immune system for durable anti-tumoral activity

Anti-tumoral immunity requires coordination of diverse responses leading to durable tumor clearance. Immunotherapy leverages specific mechanisms of the immune system to improve effector cell-mediated attack of tumors. We engineered SAR-444245 [SAR'245, formerly known as THOR-707] as a not-alpha interleukin-2 (IL-2) designed for increased half-life and selective targeting of CD8+ T and natural killer (NK) cells while reducing targeting of immune-suppressive CD4+ regulatory T cells (Tregs). The anti-tumoral efficacy of SAR'245 was investigated using the syngeneic CT-26 mouse model characterized by high infiltration with Tregs and responsiveness to programmed cell-death protein-1 (PD-1) checkpoint inhibitory antibodies. We evaluated SAR'245 pharmacokinetics and peripheral and intra-tumoral pharmacodynamics employing cytometry, histochemistry, RNAseq and secreted cytokine readouts, and in vivo efficacy as single-agent and in combination with an anti-mouse PD-1 antibody. In CT-26 tumor-bearing mice, SAR'245 administration induced peripheral expansion of CD8+ T and NK cells, including T cell memory subpopulations, without significant Treg expansion. SAR'245 stimulated anti-tumor activity that was enhanced in combination with an anti-PD-1 checkpoint inhibitory antibody, promoting both long-term survival and rejection of tumor cells on re-challenge. This agent elevated lymphocytic infiltration of tumors and T cell clonal diversity, eliciting multiple intra-tumoral gene signatures reporting on enhanced effector cell activity and persistence in the tumor microenvironment. Overall, we demonstrate that the IL-2 not-alpha agent SAR'245 induces immune responses that promote infiltration of CD8+ T and NK cells with enhanced effector function, leading to durable antitumoral response. These findings suggest SAR'245 potential for the treatment of solid tumors, particularly in combination with inhibitors of PD-1.