LB: Preclinical Efficacy of ENTR-601-51 for the Treatment of Exon 51 Skip-Amenable Duchenne Muscular Dystrophy (DMD)

Topic:

Pre-Clinical Research

Poster Number: 489 LBT

Author(s):

Michael St. Andre, PhD, Entrada Therapeutics, Nick Long, PhD, Entrada Therapeutics, Xiang Li, PhD, Entrada Therapeutics, Mahasweta Girgenrath, PhD, Entrada Therapeutics, Mary Lou Beermann, BS, Entrada Therapeutics, Jia Qi Cheng-Zhang, PhD, Entrada Therapeutics, Mohanraj Dhanabal, PhD, Entrada Therapeutics, Haoming Liu, PhD, Entrada Therapeutics, Christopher M. Brennan, PhD, Entrada Therapeutics, Pauline Tan, PhD, Entrada Therapeutics, Yongchao Mou, PhD, Entrada Therapeutics, Terrance A. Stadheim, PhD, Entrada Therapeutics, Wenlong Lian, PhD, Entrada Therapeutics

Antisense phosphorodiamidate morpholino oligomer (PMO)–mediated exon skipping therapies for DMD have the potential to restore dystrophin expression in skeletal muscle tissue. To enhance PMO delivery to muscle tissues, we developed Endosomal Escape Vehicle (EEV) cyclic cell-penetrating peptides conjugated to DMD exon skipping PMOs. Preclinical efficacy of ENTR-601-51, a novel EEV-PMO construct that targets exon 51 skip-amenable mutations in DMD pre-mRNA transcripts, was assessed to support its development as a potential therapy for patients with exon 51 skip-amenable DMD.

Skeletal muscle cell lines derived from patients with DMD mutations amenable to exon 51 skipping were treated with ENTR-601-51 or vehicle, and exon 51 skipping and dystrophin protein levels were assessed. Efficacy of ENTR-601-51 was also assessed via an exon 51 skip-amenable DMD mouse model (del52hDMD.mdx). In skeletal and cardiac muscle of del52hDMD.mdx mice, exon 51 skipping and dystrophin protein levels were measured after ENTR-601-51 or vehicle treatment. Tetanic force and force retention changes during eccentric injury of del52hDMD.mdx gastrocnemius muscle were also measured.

In patient-derived skeletal muscle cell lines with DMD exon 51 skip-amenable mutations, ENTR-601-51 treatment resulted in robust, dose-dependent exon 51 skipping and dystrophin protein expression. In del52hDMD.mdx mice, ENTR-601-51 treatment produced robust, dose-dependent exon 51 skipping and dystrophin protein expression in skeletal and cardiac muscle tissues, accompanied by significant increases in dystrophin-positive fibers and qualitative improvements in gastrocnemius muscle pathology. Importantly, a dose-dependent rescue of specific tetanic force loss and improvement in force retention during eccentric injury assays were observed in the gastrocnemius muscle.

These results demonstrate that ENTR-601-51 is efficiently delivered to skeletal and cardiac muscle, thereby producing durable exon skipping and functional dystrophin protein that can rescue muscle contractile function in a relevant mouse model of human DMD. These findings support further evaluation of ENTR-601-51 in patients with DMD amenable to exon 51 skipping.