AB0036 Il-20 targets local tissue inflammation as opposed to systemic inflammation

Background Interleukin-20 (IL-20) is a proinflammatory cytokine that has been implicated in the pathogenesis of autoimmune disease. In a Phase 2a clinical trial in rheumatoid arthritis, a monoclonal antibody neutralizing the activity of IL-20 (NNC0109-0012) reduced disease activity. The improvement was rapid, occurring within one week of receiving the first dose, and persisted for several weeks after the final dose. Anti-IL-20 was well tolerated and raised no safety concerns. Objectives In order to investigate potential effects of anti-IL-20 on the systemic immune response, we evaluated whether human peripheral immune cells are targets of IL-20. Methods Functional response to IL-20 requires expression of a heterodimeric receptor composed of IL-20R1 and IL-20R2 or IL-22R and IL-20R2. Following IL-20 stimulation, signalling proceeds through phosphorylation of STAT3 and subsequent translocation to the nucleus. Therefore, expression of IL-20R1, IL-20R2, and IL-22R was studied by a combination of flow cytometry, qPCR, and RNASeq. Furthermore, we evaluated the phosphorylation of STAT3 via flow cytometry and STAT3 translocation by high throughput microscopic imaging. Finally, functional responsiveness was detected via measurement of cell type-specific readouts, including proliferation, differentiation, and cytokine production in response to IL-20 treatment. RA patient whole blood and an extensive collection of immune cell subsets derived from healthy human blood and tonsil were analyzed, both directly after isolation and following ex vivo activation. Results Expression analysis of IL-20 receptor subunits demonstrates the presence of IL-20R2 in few immune cell types, but neither IL-20R1 nor IL-22R was detected. As co-expression of both the IL-20 receptor beta chain and one of the two alpha chains is required for a functional receptor, immune cells do not appear to be the primary mediators of IL-20 function. This was further supported by the lack of STAT3 signalling in IL-20 treated cells. Finally, other readouts of functional responsiveness, such as cytokine production, were not triggered by IL-20 in individual cell types or whole blood cultures. In contrast to non-immune cells (keratinocytes as an example) that respond to IL-20 through STAT3 signalling and contribute to inflammation, immune cell types appear to lack responsiveness to IL-20 overall. Conclusions Using a variety of methods, no evidence could be found in support of a role for IL-20 in systemic immune