Pharmacotherapeutic strategies to promote regulatory T cell function in autoimmunity

Autoimmune diseases arise when self-antigen-specific T and B cells escape central and peripheral mechanisms of tolerance. One such mechanism is control of autoreactivity by regulatory T cells (Tregs), which have an essential role in suppressing autoimmunity. Consequently, there is significant interest in developing ways to boost or restore the function of Tregs in order to prevent or treat autoimmunity, induce tolerance, and thus reduce the reliance on broadly immunosuppressive agents. Strategies include enhancing the numbers and/or function of Tregs directly in vivo or via adoptive cell therapy. Here, we review recent advances in our understanding of how pharmacologic approaches can be applied to enhance Treg function in vivo through repurposing of established drug therapies or application of new therapies. Specifically, we discuss the potential of Treg-promoting drugs, including interleukin-2 and its derivatives, and tumor necrosis factor receptor 2 agonists, as well as Treg-preserving tyrosine kinase 2 inhibitors. We discuss how co-stimulatory blockade with CTLA-4 immunoglobulin affects tolerogenic environments and consider whether lymphodepleting therapies, such as antithymocyte globulin and teplizumab, might be needed to condition the environment for better Treg-promoting effects. We focus on the potential application of Treg-promoting drugs in type 1 diabetes and draw on evidence from transplantation. With multiple pharmacotherapeutic strategies to optimize Tregs in vivo, there is significant promise for new approaches to effectively and durably induce autoimmune disease remission.