Pathology-Targeted EP4 Agonism Reverses Fibrosis in a Rat Model of DMD

Duchenne muscular dystrophy (DMD) presents a critical therapeutic gap in adolescent patients, where extensive fibro-fatty muscle replacement and depletion of the regenerative niche render existing interventions insufficient. Prostaglandin E2 signaling through the EP4 receptor stimulates bone and muscle regeneration and repair, but systemic off-target effects have limited the clinical translation of EP4 agonism in diseases such as DMD. We therefore evaluated irodanoprost (IROD), a bone-targeted prodrug of an EP4-selective agonist, in a DMD rat model, comparing early- and late-intervention cohorts. In adolescent rats, 8 weeks of treatment reduced body weight deficit by 41.4% and restored hindlimb muscle mass and maximum tetanic force to wild-type levels. IROD dose-dependently inhibited fibro-adipogenic progenitor differentiation into -SMA myofibroblasts, facilitating active resolution of established fibrosis below pre-treatment baseline. This was accompanied by re-activation of a synchronized regenerative program marked by clustered eMHC fibers, restoring the total myofiber pool to wild-type levels. A strong linear correlation between intramuscular fat reduction and fibrosis resolution suggests that MRI-based fat imaging may serve as a non-invasive surrogate for monitoring anti-fibrotic efficacy. The efficacy of IROD is likely aided by the fact that while it selectively distributes to bone in healthy animals, we observed markedly enhanced accumulation of the drug in dystrophic muscle. These findings establish IROD as a pathology-targeted approach capable of resolving the fibro-fatty niche and restoring regenerative capacity in advanced DMD. SummaryPathology-targeted EP4 agonism resolves established fibrosis and restores myofiber regeneration in a rat model of adolescent Duchenne dystrophy. Graphic abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=104 SRC="FIGDIR/small/728674v1_ufig1.gif" ALT="Figure 1"> View larger version (28K): org.highwire.dtl.DTLVardef@20447dorg.highwire.dtl.DTLVardef@70929dorg.highwire.dtl.DTLVardef@a99628org.highwire.dtl.DTLVardef@1c158f4_HPS_FORMAT_FIGEXP M_FIG C_FIG