New selective androgen receptor modulator TEI-SARM2 improves muscle function in a Duchenne muscular dystrophy rat model

Duchenne muscular dystrophy (DMD) is a severe muscle wasting disease caused by a genetic mutation in the Dmd gene. Dystrophin mutant mice (mdx) have traditionally been used for DMD research as a disease model in the preclinical stage; however, mdx mice exhibit only very mild phenotypes to partially mimic muscle degeneration and regeneration. To overcome this limitation in preclinical studies, DMD mutant rats (DMD rats) generated by CRISPR/Cas were used as a DMD model to exhibit age-dependent progressive muscle degeneration and pathophysiological features similar to DMD patients and more severe than those displayed by mdx mice. TEI-SARM2 is a non-steroidal, orally available selective androgen receptor modulator (SARM) developed as a pharmaceutical candidate for the treatment of muscle wasting diseases based on its potent anabolic activity on skeletal muscle mass. In this study, long-term treatment of daily oral administration of TEI-SARM2 to DMD rats significantly improved muscle function (endurance and strength) assessed by grip and tetanic force measurements. TEI-SARM2 did not increase the muscle weight of hindlimbs in male DMD rats; moreover, long-term, weekly oral administration for 24 weeks improved muscle function with reduced side effects on the prostate and testes weight. Histological analysis showed that TEI-SARM2 significantly reduced adipose tissue infiltration in DMD muscle. In female DMD rats, both daily and weekly TEI-SARM2 treatment showed anabolic effects and enhanced muscle strength and endurance. Taken together, these results indicate that TEI-SARM2 has non-anabolic and anabolic effects that improve dystrophic muscle dysfunction and can be a supportive therapeutic option for DMD.