431P Exon 45 skipping and dystrophin production with ENTR-601-45 in preclinical models of Duchenne muscular dystrophy

• Published in: Neuromuscular disorders : NMD 2024-10, Vol.43, p.104441, Article 104441.302
• Main Authors: Girgenrath, M., Estrella, N., Kumar, A., Hicks, A., Brennan, C., Blake, S., Li, X., Pathak, A., Kheirabadi, M., Dougherty, P., Lian, W., Liu, N., Gao, N., Wang, D., Streeter, M., Stadheim, A., Dhanabal, M., Qian, Z.
• Format: Article
• Language: English
• ISSN: 0960-8966
• DOI: 10.1016/j.nmd.2024.07.311

Intracellular delivery of oligonucleotide therapeutics for the treatment of Duchenne muscular dystrophy (DMD) is challenging because of poor cell entry and limited escape from the endosome in the target cell resulting in high therapeutic doses. To address this, we designed a family of cyclic cell-penetrating peptides that form the core of our Endosomal Escape Vehicle (EEV™) platform, which has been shown to efficiently deliver exon skipping phosphorodiamidate morpholino oligomers (PMOs) to skeletal and cardiac muscle. Proof of concept studies in D2-mdx mice showed robust exon skipping and dystrophin production in skeletal and cardiac muscle following administration of an EEV-exon 23 skipping PMO conjugate confirming the therapeutic potential of EEV-PMO conjugates for the treatment of DMD. ENTR-601-45 is an EEV-exon 45 skipping PMO conjugate in development for the treatment of exon 45 skip amenable DMD. Here, we aim to examine the efficacy of ENTR-601-45 in cell and animal models. Treatment of DMD patient-derived skeletal and cardiac muscle cells harboring an exon 45 amenable mutation deletion demonstrated robust, dose-dependent exon 45 skipping and dystrophin production. In vivo exon skipping efficacy of ENTR-601-45 was confirmed in both cardiac and skeletal muscle of human dystrophin expressing (hDMD). To further examine the therapeutic potential of exon 45 skipping EEV-PMO constructs, we utilized hDMD mice containing a mutation in the human DMD exon 44 transgene on an mdx mouse background. These mice are amenable to exon 45 skipping and allow for quantification of both exon 45 skipping and dystrophin production in vivo. Administration of a single IV dose of an exon 45 skipping EEV-PMO construct showed robust exon skipping translating to dystrophin production. Of note, significantly higher exon skipping was observed in this disease model compared with wild-type hDMD mice, demonstrating the importance of an appropriate disease model for translational preclinical studies. These findings demonstrate the robust preclinical efficacy of ENTR-601-45 in both cell and animal models and support further study in DMD patients amenable to exon 45 skipping.