Seralutinib decreases endotrophin (PRO-C6) production, a mediator of fibrosis and inflammation, in an in vitro model of pulmonary fibrosis

Introduction: Pulmonary hypertension (PH) is characterized by progressive vascular remodeling, contributed in part by extracellular matrix (ECM) deposition. In the phase 2 TORREY study (NCT04456998) treatment with seralutinib, an inhaled tyrosine kinase inhibitor, was associated with a reduction of ECM components in the plasma, such as COL6A3, highlighting its anti-fibrotic effect. A cleavage product of COL6A3, endotrophin (PRO-C6), derived from activated fibroblast has been shown to promote fibrosis and inflammation, which in turn propagates further tissue remodeling in diseases associated with cardiac and hepatic fibrosis. This study aims to investigate the effect of seralutinib on production of PRO-C6 in pulmonary fibrosis. Methods: Primary healthy lung fibroblasts (NHLFs) were cultured using the Scar-in-a-jar model and exposed to a pro-fibrotic cytokine cocktail (FC) for 12 days. FC, seralutinib (10-1000 nM), and treatment controls were administered on days 0, 4, and 8. On day 12, cell culture supernatants were collected to quantify NordicPRO-C6™ levels. Results: Stimulating NHLFs with the FC increased PRO-C6 by 2.3-fold at day 12 compared to unstimulated cells. By day 12, seralutinib treatment reduced PRO-C6 levels in a concentration-dependent manner (1.3- to 2.3-fold), with 1000 nM seralutinib reducing PRO-C6 levels to those observed in unstimulated cells. Conclusion: Seralutinib decreased PRO-C6 production in an in vitro model of pulmonary fibrosis providing a compelling rationale to further investigate its potential as a surrogate biomarker of pulmonary fibrosis and its role in the pathophysiology of vascular remodeling in PH.