Recent Trends in Antisense Therapies for Duchenne Muscular Dystrophy.

Duchenne muscular dystrophy (DMD) is a debilitating and fatal genetic disease affecting 1/5000 boys globally, characterized by progressive muscle breakdown and eventual death, with an average lifespan in the mid-late twenties. While no cure yet exists for DMD, gene and antisense therapies have been heavily explored in recent years to better treat this disease. Four antisense therapies have received conditional FDA approval, and many more exist in varying stages of clinical trials. These upcoming therapies often utilize novel drug chemistries to address limitations of existing therapies, and their development could herald the next generation of antisense therapy. This review article aims to summarize the current state of development for antisense-based therapies for the treatment of Duchenne muscular dystrophy, exploring candidates designed for both exon skipping and gene knockdown.

Systemic administration of the antisense oligonucleotide NS-089/NCNP-02 for skipping of exon 44 in patients with Duchenne muscular dystrophy: Study protocol for a phase I/II clinical trial.

AIM: The purpose of this study is to evaluate the safety and pharmacokinetics of the novel morpholino oligomer NS-089/NCNP-02 which can induce exon 44 skipping, in patients with DMD. Additionally, we aimed to identify markers predictive of therapeutic efficacy and determine the optimal dosing for future studies. METHODS: This is an open-label, dose-escalation, two-center phase I/II trial in ambulant patients with DMD, presence of an out-of-frame deletion, and a mutation amenable to exon 44 skipping. Part 1 is a stepwise dose-finding stage (4 weeks) during which NS-089/NCNP-02 will be administered intravenously at four dose levels once weekly (1.62, 10, 40, and 80 mg/kg); Part 2 is a 24-week evaluation period based on the dosages determined during Part 1. The primary (safety) endpoints are the results of physical examinations, vital signs, 12-lead electrocardiogram and echocardiography tests, and adverse event reporting. Secondary endpoints include expression of dystrophin protein, motor function assessment, exon 44 skipping efficiency, plasma and urinary NS-089/NCNP-02 concentrations, and changes in blood creatine kinase levels. DISCUSSION: Exon-skipping therapy using ASOs shows promise in selected patients, and this first-in-human study is expected to provide critical information for subsequent clinical development of NS-089/NCNP-02.

Exon 44 skipping in Duchenne muscular dystrophy: NS-089/NCNP-02, a dual-targeting antisense oligonucleotide.

Exon-skipping therapy mediated by antisense oligonucleotides is expected to provide a therapeutic option for Duchenne muscular dystrophy. Antisense oligonucleotides for exon skipping reported so far target a single continuous sequence in or around the target exon. In the present study, we investigated antisense oligonucleotides for exon 44 skipping (applicable to approximately 6% of all Duchenne muscular dystrophy patients) to improve activity by using a novel antisense oligonucleotide design incorporating two connected sequences. Phosphorodiamidate morpholino oligomers targeting two separate sequences in exon 44 were created to target two splicing regulators in exon 44 simultaneously, and their exon 44 skipping was measured. NS-089/NCNP-02 showed the highest skipping activity among the oligomers. NS-089/NCNP-02 also induced exon 44 skipping and dystrophin protein expression in cells from a Duchenne muscular dystrophy patient to whom exon 44 skipping is applicable. We also assessed the in vivo activity of NS-089/NCNP-02 by intravenous administration to cynomolgus monkeys. NS-089/NCNP-02 induced exon 44 skipping in skeletal and cardiac muscle of cynomolgus monkeys. In conclusion, NS-089/NCNP-02, an antisense oligonucleotide with a novel connected-sequence design, showed highly efficient exon skipping both in vitro and in vivo.