Engineered IL-10 variants elicit potent immuno-modulatory activities at therapeutic low ligand doses

Interleukin-10 is a dimeric cytokine with potent anti-inflammatory and anti-cancer activities. Despite its immune-regulatory potential, IL-10-based therapies have shown only marginal benefits in the clinic. Here we have explored whether the stability of the IL-10-receptor complex contributes to IL-10 immuno-modulatory potency. For that, we have generated an IL-10 mutant with greatly enhanced affinity for its IL-10Rβ receptor via yeast surface display. The affinity enhanced IL-10 variants formed surface active complexes more efficiently than the wild-type cytokine and triggered more potent STAT1 and STAT3 activation in human monocytes and CD8 T cells. This in turn led to more robust induction of IL-10-mediated gene expression programs at a wide range of ligand concentrations in both human cell subsets. IL-10 regulated genes involved in monocyte energy homeostasis, migration and trafficking, and genes involved in CD8 T cell exhaustion. Interestingly, at non-saturating doses, IL-10 lost key components of its gene-expression program, which may explain its lack of efficacy in a clinical set up. Remarkably, our engineered IL-10 variant exhibited a more robust bioactivity profile than IL-10 wt at all the doses tested in monocytes and CD8 T cells. Our study provides unique insights into how IL-10-receptor complex stability contributes to fine-tune IL-10 biology, and open new opportunities to revitalize failed IL-10 therapies. Human monocytes and CD8 T cells were stimulated under 7 conditions each; control (unstimualted), WTD50 nM, WTD 0.1 nM, R5A11D 50 nM, R5A11D 0.1 nM, WTM 50 nM, R5A11M 50 nM. Each condition has three biolocial replicates (human donors)