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-2Rβγ 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-2Rβγ 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 T(regs) 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.