Phase 1/2 Trial of Brogidirsen: Dual-Targeting Antisense Oligonucleotides for Exon 44 Skipping in Duchenne Muscular Dystrophy

New Advances in Dual-Targeting Antisense Oligonucleotide Therapy for Duchenne Muscular Dystrophy: Phase 12 Clinical Trial of Brogidirsen

Background

Duchenne Muscular Dystrophy (DMD) is a fatal genetic disorder primarily affecting skeletal and cardiac muscles, leading to early loss of mobility and, eventually, organ failure. Currently, there is no cure for DMD. The disease is caused by mutations in the DMD gene localized on the short arm of the X chromosome (Xp21.2), resulting in a deficiency or abnormality in dystrophin, a crucial protein responsible for stabilizing the structure of muscle cell membranes. The absence of dystrophin leads to a gradual degeneration of muscle fibers, ultimately causing muscle necrosis and functional decline.

Among the existing therapeutic strategies for DMD, exon-skipping therapy shows great promise as a molecular therapy by using short antisense oligonucleotides (ASOs) to correct deficient DMD gene transcripts. This enables the production of partially functional dystrophin. However, the current ASO-based therapies are limited to specific mutation types with suboptimal efficacy. To address these shortcomings, researchers at Japan’s National Center of Neurology and Psychiatry (NCNP) have developed a new dual-targeting antisense oligonucleotide, Brogidirsen (compound number NS-089/NCNP-02), specifically designed to induce skipping of exon 44 in the DMD gene.

Source of the Study

The study was conducted by a team of researchers led by Hirofumi Komaki, Eri Takeshita, Katsuhiko Kunitake, and others at NCNP, Japan. It represents the first human clinical application of Brogidirsen. The findings were published in Cell Reports Medicine under the title “Phase 12 Trial of Brogidirsen: Dual-Targeting Antisense Oligonucleotides for Exon 44 Skipping in Duchenne Muscular Dystrophy” on January 21, 2025. The clinical trial is registered at ClinicalTrials.gov (NCT04129294).

Research Design and Methods

Study Design

This study is an open-label, dose-escalation, Phase 12 clinical trial, consisting of two phases:

  1. Part 1: Dose Exploration Phase (4 Weeks)

    • Two cohorts were treated with four escalating doses of Brogidirsen (1.62 mg/kg, 10 mg/kg, 40 mg/kg, and 80 mg/kg) via intravenous administration. Each cohort included three DMD patients.
    • The primary goal was to assess the safety, tolerability, and preliminary efficacy of the drug.
  2. Part 2: Extension Treatment Phase (24 Weeks)

    • Based on findings from Part 1, two doses (40 mg/kg and 80 mg/kg) were selected for evaluation. Each dosage group consisted of three patients.

The trial enrolled six male DMD patients aged 4 to 13 years. Among them, five had exon 45 deletions, and one had an exon 45–54 deletion. All patients were ambulatory, with most receiving corticosteroid therapy.

Data Collection and Analysis
  1. Exon Skipping Efficiency
    Using reverse transcription polymerase chain reaction (RT-PCR), exon 44 skipping efficiency in muscle biopsy samples was calculated as the ratio of skipped fragments to total fragments: skipped fragment/(skipped fragment + full-length fragment) × 100%.

  2. Dystrophin Protein Expression
    Western blotting and immunohistochemistry were performed to quantify dystrophin expression, expressed as a ratio relative to a reference protein. Immunofluorescent staining was used to visualize protein localization.

  3. Pharmacokinetics (PK)
    High-performance liquid chromatography-tandem mass spectrometry was used to measure Brogidirsen plasma concentrations and pharmacokinetic parameters, including Cmax (maximum plasma concentration), AUC (area under the curve), Tmax (time to peak concentration), and T1/2 (half-life).

  4. Proteomics Analysis
    Blood samples were analyzed using high-throughput proteomics (Olink platform) to investigate changes in proteins associated with muscle pathology.

  5. In Vitro Experiments with Patient-Derived Cells
    Urine samples obtained from patients were used to derive muscle-like cells. Brogidirsen experiments evaluated dose-dependent effects on exon skipping and dystrophin expression, validating efficacy in vitro.

Key Results

  1. Safety and Tolerability

    • During Part 1, mild drug-related adverse events (e.g., elevation of urinary β2 microglobulin) were observed at low-to-moderate doses. No serious adverse events (SAEs) were reported during Part 2’s high-dose treatment phase.
    • Brogidirsen demonstrated excellent safety and tolerability at 40 mg/kg and 80 mg/kg over the 24-week period.
  2. Exon Skipping Efficiency and Dystrophin Levels

    • Exon 44 skipping efficiency increased significantly from baseline, with a mean efficiency of 32.10% and a statistically significant improvement in the high-dose group.
    • Dystrophin expression levels reached 16.63% (40 mg/kg) and 24.47% (80 mg/kg) of normal levels, significantly higher than baseline.
  3. Proteomic Biomarkers

    • Muscle damage biomarkers, including Titin (Ttn), Myomesin 2 (Myom2), and Myosin Light Chain Phosphorylatable (Mylpf), decreased significantly by weeks 12 and 24 post-treatment.
    • PADI2, an astrocyte-associated biomarker, was substantially reduced, suggesting improvements in muscle pathology.
  4. Pharmacokinetics

    • Cmax and AUC increased dose-dependently, with no drug accumulation observed over time.

Conclusions and Significance

This study demonstrated that Brogidirsen is a safe and effective dual-targeting ASO therapy for DMD patients. Its innovative design significantly improved exon 44 skipping efficiency and dystrophin protein production, stabilizing patients’ muscular functions.

Moreover, the study validated its efficacy through patient-derived in vitro models, providing a non-invasive method for assessing individual drug responses. The absence of non-responders during the trial suggests broad applicability, though further research is needed to explore long-term therapeutic benefits.

Study Highlights

  1. Innovative Dual-Targeting Sequence Design
    Enhanced drug delivery and exon-skipping efficiency.

  2. High-Precision Proteomics
    Identification of novel biomarkers associated with disease progression and treatment response.

  3. Patient-Derived Cells as Validation Models
    A non-invasive method to predict therapeutic effects in vitro.

Outlook and Implications

Brogidirsen represents a breakthrough in ASO-based therapy for DMD, showing the best therapeutic outcomes achieved to date. It paves the way for more precise and effective treatments for exon-skipping therapies, expanding avenues for clinical application. Future studies aim to include larger patient samples, longer treatment durations, and strategies to enhance drug delivery to skeletal and cardiac muscles.

This landmark study not only establishes a solid foundation for DMD therapies but also offers valuable insights into precision medicine for rare genetic disorders.