P132 The preferential Pde4b inhibitor nerandomilast (BI 1015550) exhibits antifibrotic and anti-inflammatory effects in human in vitro SSc models

Abstract Background/Aims Systemic sclerosis (SSc) is a rare autoimmune disease characterised by fibrosis of the skin and other organs, and there is a significant unmet need for new treatments. Phosphodiesterase (PDE) 4 inhibition is associated with broad anti-inflammatory and antifibrotic effects. Nerandomilast is an oral preferential inhibitor of the PDE4B subtype and a potential treatment for idiopathic pulmonary fibrosis and progressive pulmonary fibrosis. In vitro studies have shown that nerandomilast exerts antifibrotic and anti-inflammatory effects by inhibiting myofibroblast transformation, lung fibroblast proliferation, and proinflammatory cytokine release from peripheral blood mononuclear cells (PBMCs). This suggests that nerandomilast could be beneficial in SSc by targeting both fibrosis and inflammation. The study investigated the effect of nerandomilast on the expression of fibrosis markers and the proliferation of normal and SSc patient dermal fibroblasts, as well as normal human keratinocytes. The effects of nerandomilast on proinflammatory mediator release from normal and SSc patient-derived PBMCs and normal macrophages, and IFN response gene expression of normal macrophages, were also investigated. Methods Normal human and SSc patient-derived dermal fibroblasts, and normal human keratinocytes, were treated with nerandomilast following cytokine stimulation. The effects of nerandomilast on cell proliferation were measured using a BrdU assay for normal fibroblasts and keratinocytes, and Ki-67 staining for IL-1β + bFGF-stimulated SSc patient-derived fibroblasts. The effects of nerandomilast on the expression of fibrosis markers IGFBP3, sICAM-1 and PAI-1, and on the extracellular matrix protein Col1α1, were characterised using ELISA. Antifibrotic effects of nerandomilast were determined with an in vitro fibrosis model (Scar-in-a-Jar) using SSc patient-derived fibroblasts exposed to TGF-β and PGE2. Effects of nerandomilast on secretion of TNF-α from LPS-stimulated normal human and SSc patient-derived PBMCs, and from normal human macrophages along with IL-6 secretion, were determined by ELISA. The expression of type 1 and 2 IFN markers from human macrophages was investigated by ELISA and qPCR. Results Nerandomilast reduced SSc dermal fibroblast proliferation and IGFBP3, sICAM-1 and PAI-1 expression. In a Scar-in-a-Jar assay, nerandomilast significantly decreased the levels of α-smooth muscle actin in fibroblasts. The effect of nerandomilast alone was greater compared with mycophenolate mofetil (MMF) alone, a commonly used treatment for SSc. When used in combination with MMF, nerandomilast exhibited similar or greater effects on proliferation and expression of fibrosis markers, except on soluble ICAM-1. Antiproliferative and antifibrotic effects of nerandomilast were also observed on normal fibroblasts. In addition, nerandomilast reduced Col1α1 expression in normal human keratinocytes and TNF-α secretion from PBMCs. Nerandomilast also suppressed TNF-α and IL-6 secretion from human macrophages and attenuated type 1 and 2 IFN responses. Conclusion Nerandomilast had significant antifibrotic and anti-inflammatory effects on cell types relevant to SSc in vitro, indicating that it could attenuate the underlying disease pathology in SSc. Disclosure D. Schniertshauer: Corporate appointments; Albstadt-Sigmaringen University of Applied Sciences (at time of study), Boehringer Ingelheim (current). Grants/research support; Boehringer Ingelheim (financial support for this study paid to his institution). D.L. Ebenezer: Corporate appointments; Boehringer Ingelheim. Shareholder/stock ownership; AbbVie, Bristol Myers Squib, Pfizer, Novo Nordisk. D. Schloesser: Corporate appointments; Boehringer Ingelheim. K. El Kasmi: Corporate appointments; Boehringer Ingelheim. C. Hesslinger: Corporate appointments; Boehringer Ingelheim. J. Bergemann: Consultancies; MSE Pharmaceuticals. Grants/research support; Boehringer Ingelheim.