Simultaneous targeting of IL-10 and PD-(L)1 pathways with a bispecific anti-PD-L1/IL-10-trap antibody enhances T cell responses.

Immune checkpoint inhibitors (ICIs) demonstrate clinical benefits with durable responses but only in a subset of patients with cancer. Understanding the mechanisms that limit T cell-mediated cytotoxicity of tumor cells and developing new therapies are both needed to overcome such limitations. Interleukin-10 (IL-10) is a cytokine with known pro- and anti-tumor roles. Here, we demonstrate that the nature of IL-10 activity depends on its concentration: very high exogenous IL-10 concentrations induce IFNγ production by T cells, while concentrations similar to those found in the serum of patients with cancer suppress T cell activity. To test if simultaneously trapping IL-10 while blocking PD-L1 could overcome these suppressive effects, which are hypothesized to limit the activity of anti-PD-L1 or drive adaptive resistance, we developed an anti-PD-L1/IL-10-trap antibody comprising a Fab paratope directed against programmed death ligand 1 (PD-L1) fused to a VHH domain targeting IL-10, which acts as an IL-10 "trap." We found that treatment with anti-PD-L1/IL-10-trap protects T cells from suppressive IL-10 and drives superior activation compared to anti-PD-L1 or IL-10-trap alone. Furthermore, anti-PD-L1/IL-10-trap shifted macrophage polarization toward a more mature and activated phenotype and enhanced CD8