P53 Guselkumab binding to CD64+ IL-23–producing myeloid cells enhances potency for neutralizing IL-23 signalling

Abstract IL-23 is implicated in the pathogenesis of psoriasis (PsO), and myeloid cells expressing FcγRI (CD64) are the primary source of IL-23 in lesional PsO skin tissue. The incidence and prevalence of psoriatic arthritis increases with PsO severity, and joint disease activity is positively correlated with frequency of peripheral CD64+ monocytes. We evaluated: CD64 and IL-23 expression in PsO patient skin biopsies; binding of anti-IL-23p19 subunit IgG1 monoclonal antibodies (mAbs) guselkumab [(GUS) fully human, native Fc-region] and risankizumab [(RZB) humanized, mutated Fc-region] to CD64; and functional consequences of CD64 binding by anti-IL-23p19 subunit mAbs in in vitro assays. CD64, IL-23p19 and IL-23p40 subunits mRNA transcripts were analysed from bulk and single-cell RNAseq datasets. Binding of mAbs to IFNγ-primed human monocytes and IL-23–secreting inflammatory monocytes, and capture of endogenously secreted IL-23, were evaluated by flow cytometry. Internalization of IL-23 and GUS/RZB within CD64+ macrophages was assessed with live-cell confocal imaging. GUS and RZB potency for inhibiting IL-23 was determined in a co-culture of THP-1 cells (CD64+ monocyte cell line activated to produce IL-23) and an IL-23 reporter cell line (measuring biologically active IL-23). IL-23p19 mRNA transcript expression in the co-culture was measured by qPCR. Expression of CD64, IL-23p19, and IL-23p40 mRNA transcripts was increased in lesional vs. non-lesional PsO skin, as were the abundance of myeloid cell types co-expressing CD64/IL-23p19 mRNA transcripts. In in vitro assays, GUS (not RZB) demonstrated Fc-mediated binding to CD64 on IFNγ-primed monocytes. Moreover, CD64-bound GUS simultaneously captured IL-23 secreted from the same cells. GUS (not RZB) bound to the CD64+ macrophages and mediated IL-23 internalization to low pH intracellular compartments. GUS and RZB equipotently inhibited signalling by IL-23 present in THP-1-conditioned medium. However, in a co-culture of IL-23–producing THP-1 cells with an IL-23–responsive reporter cell line, GUS demonstrated enhanced potency vs. RZB for inhibiting IL-23 signalling. GUS did not alter IL-23p19 mRNA transcript expression in the co-culture. These findings were consistent with previous observations of CD64+ myeloid cells as a key source of IL-23 in lesional PsO skin tissue. GUS binding to CD64 on IL-23-producing cells likely contributed to the enhanced potency of GUS vs. RZB in inhibiting IL-23 signalling in the co-culture assay. These in-vitro data support a hypothesis for optimal localization of GUS in inflamed tissues, where CD64+ IL-23-producing myeloid cells are increased and in proximity to IL-23-responsive lymphoid cells, enhancing GUS neutralization of IL-23 at its source of production.