Systemic sclerosis (SSc) is a complex and heterogeneous condition characterized by progressive fibrosis in multiple organs. Recent studies implicate plasminogen activator inhibitor 1 (PAI-1) in the pathogenesis of SSc, and PAI-1 is considered as a potential target for therapy. Here, using single-cell and spatial RNA-seq analysis of skin biopsies from 18 healthy individuals and 22 SSc patients, we found elevated PAI-1 co-localizing to myofibroblasts with enriched extracellular matrix-associated biological processes. Treatment of SSc dermal fibroblasts with the small molecule PAI-1 inhibitor MDI-2517 reduced the expression of the profibrotic markers COL1A1 and ACTA2 . To investigate the therapeutic potential of MDI-2517, we evaluated its efficacy in reducing fibrosis in a preclinical model of SSc. Treatment of mice with MDI-2517 significantly reduced both skin and lung fibrosis and was superior to treatment with either pirfenidone or mycophenolate mofetil. Additionally, MDI-2517 attenuated weight loss and significantly reduced the expression of key profibrotic markers. Compared to tiplaxtinin, another PAI-1 inhibitor previously shown to be effective in a model of SSc, MDI-2517 was found to have superior efficacy at a 10-fold lower dose. These findings highlight the role of PAI-1 in the pathogenesis of SSc, and the potential of MDI-2517 for the treatment of SSc.
Su et al. (2026) studied this question.