Engineered IL-10 Variants Elicit Potent Immunomodulatory Effects at Low Ligand Doses.

An IL-10 variant with higher affinity for a receptor subunit remains effective at low concentrations. Building a better IL-10 The cytokine IL-10 suppresses inflammation and enhances the cytolytic activity of T cells. However, exogenously administered IL-10 has not been therapeutically successful, likely because of low bioavailability in the target tissue. IL-10 binds to a heterodimeric receptor composed of IL-10Rα subunits (to which it binds with high affinity) and IL-10Rβ subunits (to which it binds with lower affinity). Gorby et al. engineered an IL-10 variant with higher affinity for IL-10Rβ than that of wild-type IL-10. At low concentrations, this variant more potently triggered changes in gene expression in monocytes and CD8+ T cells that would be expected to suppress inflammation. CAR T cells cultured with this variant were more effective at killing acute myeloid leukemic cells. Thus, IL-10 therapy may become clinically feasible using variants with enhanced affinity for IL-10Rβ. Interleukin-10 (IL-10) is a dimeric cytokine with both immunosuppressive and immunostimulatory activities; however, IL-10–based therapies have shown only marginal clinical benefits. Here, we explored whether the stability of the IL-10 receptor complex contributes to the immunomodulatory potency of IL-10. We generated an IL-10 mutant with enhanced affinity for its IL-10Rβ receptor using yeast surface display. Compared to the wild-type cytokine, the affinity-enhanced IL-10 variants recruited IL-10Rβ more efficiently into active cell surface signaling complexes and triggered greater STAT1 and STAT3 activation in human monocytes and CD8+ T cells. These effects, in turn, led to more robust induction of IL-10–mediated gene expression programs at low ligand concentrations in both human cell subsets. IL-10–regulated genes are involved in monocyte energy homeostasis, migration, and trafficking and in CD8+ T cell exhaustion. At nonsaturating doses, IL-10 did not induce key components of its gene expression program, which may explain its lack of efficacy in clinical settings. Our engineered IL-10 variant showed a more robust bioactivity profile than that of wild-type IL-10 at low doses in monocytes and CD8+ T cells. Moreover, CAR-modified T cells expanded with the engineered IL-10 variant displayed superior cytolytic activity than those expanded with wild-type IL-10. Our study provides insights into how IL-10 receptor complex stability fine-tunes IL-10 biology and opens new opportunities to revitalize failed IL-10 therapies.