Niclosamide reprograms macrophages and improves muscle integrity in Duchenne muscular dystrophy models.

Duchenne Muscular Dystrophy (DMD) is a severe X-linked disorder characterized by progressive degeneration of skeletal and cardiac muscles caused by mutations in the DMD gene encoding dystrophin, a protein essential for cytoskeletal integrity and muscle function. A truncated dystrophin leads to increased muscle susceptibility to contraction-induced damage, driving chronic inflammation and fibrosis. Although corticosteroids remain the standard of care, novel therapeutic strategies are urgently needed. Niclosamide, a long-established anthelmintic drug, has recently been repurposed in inflammatory and fibrotic conditions, including neuromuscular diseases. We investigated the effects of niclosamide in vitro using primary macrophages from mdx mice, human DMD myoblasts, and murine C2C12 myoblast cultures, and in vivo in a proof-of-concept study in mdx mice. In primary mdx macrophages, niclosamide reduced inflammation and reactive oxygen species production, while promoting an anti-inflammatory/pro-regenerative phenotype. In parallel, niclosamide enhanced the differentiation of human DMD myoblasts, and conditioned medium from niclosamide-treated macrophages significantly improved C2C12 myoblast differentiation. In treated mdx mice, niclosamide improved muscle resistance and reduced muscle damage, as indicated by decreased plasma creatine kinase levels and lower immunoglobulin infiltration. These effects were accompanied by modulation of key markers involved in muscle proliferation and differentiation, supporting a beneficial role of niclosamide in promoting muscle repair in dystrophic muscle. Overall, these findings indicate that niclosamide promotes an anti-inflammatory and pro-regenerative environment, enhancing myoblast differentiation and limiting muscle degeneration, supporting its potential role as a promising therapeutic candidate for Duchenne muscular dystrophy.