The lack of dystrophin in DMD muscle leads to myofiber damage and degeneration, the impact of which is partially mitigated during early disease stages by robust myofiber regeneration. Subsequently, adolescent boys with DMD exhibit physical deterioration and loss of ambulation that coincides with near-total failure of myofiber regeneration after age 9-10 (Cardone et al, 2023), indicating a need for therapies that stimulate myoregeneration. Prostaglandins promote regeneration of rodent and human muscle via the EP4 receptor, but this pathway’s therapeutic potential has been limited by systemic tolerability issues. We addressed this via the tissue-targeted prodrug irodanoprost (MES1022), comprising a selective EP4 agonist (EP4a) reversibly conjugated to a moiety that targets calcium-rich tissues (e.g., bone and damaged myofibers). Irodanoprost was tested in dystrophin-lacking “DMD rats” with severe and progressive muscular dystrophy characterized by impaired myoregeneration, weight loss, deficits in muscle mass, myofiber size, myofiber number, and muscle strength, and increased muscle fibrosis and fat (Sugihara et al, 2020). Seven-month-old male DMD rats received 8 once-weekly s.c. injections of irodanoprost (1 or 3 mg/kg) or vehicle; wild-type (WT) controls received vehicle. Irodanoprost reversed body weight loss within 1 week, with progressive weight gain thereafter, while DMD-Veh controls continued losing weight. Tibialis anterior (TA) weight increased with irodanoprost versus DMD-Veh and WT-Veh, with increases in myofiber number and average myofiber size yielding a 2-fold increase in contractile tissue vs DMD-Veh (also p<0.01 vs WT-Veh). TA muscle fibrosis (picrosirius red) and fat (perilipin) were reduced, regenerating (centronucleated) myofibers were increased, and degenerating (IgG+) TA myofibers were similar with irodanoprost vs DMD-Veh. Ex vivo contractility of the extensor digitorum longus muscle showed greater tetanus force and stiffness with irodanoprost vs DMD-Veh. Irodanoprost 3 mg/kg also reversed relative cardiomegaly vs DMD-Veh. These results indicate therapeutic potential for irodanoprost in DMD, particularly older boys with impaired myoregeneration.