Evaluation of Common Gamma Chain Cytokine Signaling Blockade with REGN7257, an Interleukin 2 Receptor Gamma (IL2RG) Monoclonal Antibody, on Immune Cell Populations in Monkey and Human

The common γ chain cytokine receptor (γc; IL2RG) family of cytokines includes interleukin 2 (IL2), IL4, IL7, IL9, IL15, and IL21. This set of cytokines exhibits broad pleiotropic actions on both the innate and adaptive immune system with each cytokine sharing the IL2RG chain as part of its signaling receptor complex. Mutations in the IL2RG gene result in X-linked severe combined immunodeficiency (XSCID) in humans, whereby patients present with dramatically diminished numbers of T-cells and NK-cells, and dysfunctional B-cells. Given the crucial role for γc cytokines in the development and function of lymphocytes, modulating their activities may offer therapeutic potential in a range of immune-mediated diseases. To understand the effects of γc cytokine blockade on immune cells including T-cell subsets, we utilized REGN7257, a fully human IL2RG monoclonal antibody that inhibits γc cytokine-induced signaling, and tested its ability to suppress immune cell populations and their functions in cynomolgus monkey and human.

Mixed lymphocyte reaction assays were performed to look at the impact of γc cytokine signaling blockade on activation/proliferation of human T-cells. To further analyze the contribution of γc cytokines to T-cell differentiation and function, we performed in vitro transcriptomic studies on human peripheral blood mononuclear cells stimulated with anti-CD3/CD28 beads. In addition, we assessed the effects of γc cytokine signaling blockade on both human T-cell and NK-cell effector functions in target cell killing assays. Finally, we evaluated the effects of γc cytokine signaling blockade with REGN7257 on immune cell populations and their activation/proliferation status in cynomolgus monkeys by flow cytometry.

γc cytokine signaling blockade with REGN7257 demonstrated potent inhibition of allogeneic responses in mixed human lymphocyte reaction assays, by preventing T-cell activation and proliferation. Two-tailed gene set enrichment analysis identified 4 distinct patterns of significantly enriched gene sets that were impacted by γc cytokine signaling upon CD3/CD28-induced activation of human T-cells: gene sets involved in inflammatory responses, differentiation and proliferation, activation and immune responses, as well as those related to adhesion and migration. These signatures were blocked with REGN7257 treatment. In addition, REGN7257 potently blocked activation (i.e. IFNG production) and cytotoxic activity of both human T-cells and NK-cells in in vitro target cell killing assays. Finally, the impact of γc cytokine signaling blockade on lymphocyte populations in vivo were investigated in cynomolgus monkeys in a single dose pharmacokinetic/pharmacodynamic study and a repeat-dose toxicology study. Inhibition of γc cytokine signaling with REGN7257 in cynomolgus monkeys reduced circulating T-cells and NK-cells, without impacting B-cells, granulocytes, platelets or red blood cells. γc cytokine signaling blockade led to a reduction in both peripheral CD4⁺ and CD8⁺ T-cell counts with effector memory T-cells being the most impacted T-cell population studied. Similarly to that observed in human T-cell MLR assays, both activated and proliferating T-cells were reduced in monkeys dosed with REGN7257.

Taken together, these pharmacological observations highlight the major role for γc cytokine signaling in maintenance of lymphocyte populations (i.e. NK-cells and T-cells), but not other immune cell populations, such as granulocytes, platelets and red blood cells. Furthermore, our data highlight the importance of γc cytokines in driving functions of cynomolgus monkeys and human effector NK and T-cells, opening a potential new route for the management of immune-mediated diseases.

Le Floch-Ramondou:Regeneron: Current Employment, Current equity holder in private company, Current holder of stock options in a privately-held company. Nagashima:Regeneron: Current Employment, Current equity holder in private company, Current holder of stock options in a privately-held company. Gayvert:Regeneron: Current Employment, Current equity holder in private company, Current holder of stock options in a privately-held company. Pan:Regeneron: Current Employment, Current equity holder in private company, Current holder of stock options in a privately-held company. Korgaonkar:Regeneron: Current Employment, Current equity holder in private company, Current holder of stock options in a privately-held company. Shakil:Regeneron: Current Employment, Current equity holder in private company, Current holder of stock options in a privately-held company. Ullman:Regeneron: Current Employment, Current equity holder in private company, Current holder of stock options in a privately-held company. Norton:Regeneron: Current Employment, Current equity holder in private company, Current holder of stock options in a privately-held company. Perlee:Regeneron: Current Employment, Current equity holder in private company, Current holder of stock options in a privately-held company. Murphy:Regeneron: Current Employment, Current equity holder in private company, Current holder of stock options in a privately-held company. Sleeman:Regeneron: Current Employment, Current equity holder in private company, Current holder of stock options in a privately-held company. Orengo:Regeneron: Current Employment, Current equity holder in private company, Current holder of stock options in a privately-held company.