A long-lived IL-2 mutein that selectively activates and expands regulatory T cells as a therapy for autoimmune disease

Susceptibility to multiple autoimmune diseases is associated with common gene polymorphisms influencing IL-2 signaling and T-reg function, making T-reg-specific expansion by IL-2 a compelling therapeutic approach to treatment. As an in vivo IL-2 half-life enhancer we used a non-targeted, effector-function-silent human IgG1 as a fusion protein. An IL-2 mutein (N88D) with reduced binding to the intermediate affinity IL-2R beta gamma receptor was engineered with a stoichiometry of two IL-2N88D molecules per IgG, i.e. IgG-(IL-2N88D)(2). The reduced affinity of IgG-(IL-2N88D)(2) for the IL-2R beta gamma receptor resulted in a T-reg-selective molecule in human whole blood pSTAT5 assays. Treatment of cynomolgus monkeys with single low doses of IgG-(IL-2N88D)(2) induced sustained preferential activation of Tress accompanied by a corresponding 10-14-fold increase in CD4(+) and CD8(+)CD25(+) FOXP3(+) T-regs; conditions that had no effect on CD4(+) or CD8(+) memory effector T cells. The expanded cynomolgus T-regs had demethylated FOXP3 and CTLA4 epigenetic signatures characteristic of functionally suppressive cells. Humanized mice had similar selective in vivo responses; IgG-(IL-2N88D)(2) increased T-regs while wild-type IgG-IL-2 increased NK cells in addition to T-regs. The expanded human T-regs had demethylated FOXP3 and CTLA4 signatures and were immunosuppressive. These results describe a next-generation immunotherapy using a long-lived and T-reg-selective IL-2 that activates and expands functional T-regs in vivo. Patients should benefit from restored immune homeostasis in a personalized fashion to the extent that their autoimmune disease condition dictates opening up the possibility for remissions and cures.