Synergistic activity of IL-2 mutein with tolerogenic ImmTOR nanoparticles leads to massive expansion of antigen-specific Tregs and protection against autoimmune disease

Low dose IL-2 therapy and IL-2 molecules engineered to be selective for the high affinity IL-2 receptor have been shown to expand Tregs in vivo, and, in the case of low dose IL-2 therapy, has demonstrated promising therapeutic benefit in autoimmune diseases. One of the potential limitations of IL-2 therapy is the nonselective expansion of pre-existing Treg populations rather than induction of antigen-specific Tregs, as well as potential activation of effector cells. We have recently developed biodegradable nanoparticles encapsulating rapamycin, called ImmTOR, to induce selective immune tolerance to co-administered antigens, such as immunogenic biologic drugs. Unlike Treg-selective IL-2 therapy, ImmTOR alone does not increase total Treg numbers. However, here we demonstrate that the combination of ImmTOR and an engineered Treg-selective IL-2 variant (termed IL-2 mutein) increases the number and durability of total Tregs, as well as inducing a profound synergistic increase in antigen-specific Treg when combined with a target antigen. We demonstrate that the combination of ImmTOR and an IL-2 mutein leads to durable inhibition of antibody responses to co-administered AAV gene therapy capsid, even at sub-optimal doses of ImmTOR, and provides protection in autoimmune models of type 1 diabetes and primary biliary cholangitis. ImmTOR also showed the potential to increase the therapeutic window of engineered IL-2 molecules by mitigating effector T cell expansion typically observed at higher doses of IL-2 and preventing exacerbation of disease in a model of graft-versus-host-disease. At the same time, engineered IL-2 molecules showed potential for dose-sparing of ImmTOR. Overall, these results establish that the combination of ImmTOR and an IL-2 mutein show synergistic benefit on both safety and efficacy to provide durable antigen-specific immune tolerance to mitigate drug immunogenicity and to treat autoimmune diseases. ### Competing Interest Statement T.K.K., M.F., A.M., G.R., C.R., T.C., N.N., N.L., L.D., F.F. P.G.T., S.S.L., and P.O.I. are employees and shareholders of Selecta Biosciences, a company developing ImmTOR and ImmTOR-IL. Selecta Biosciences have filed a patent application on the combination of ImmTOR with engineered Treg-selective IL-2 and have licensed F5111 IC from Johns Hopkins University and the University of California San Francisco. D.VD. and J.B.S. are inventors of a patent application on F5111 IC.