Safety and Tolerability Assessment of BMN 351 in Duchenne Muscular Dystrophy: A Phase 1/2 Dose Escalation Study

The primary objective of this study is to assess the **safety** and **tolerability** of BMN 351 at different dose levels in participants with **Duchenne Muscular Dystrophy** (DMD). This is clinically relevant as it aims to determine the appropriate dosing regimen that minimizes adverse effects while maintaining therapeutic efficacy, which is crucial for the management of DMD, a severe and progressive neuromuscular disorder.

Secondary objectives include evaluating the plasma and urine **pharmacokinetics** and muscle distribution of BMN 351. Understanding the pharmacokinetics and distribution is essential for optimizing dosing strategies and ensuring that the drug reaches the target tissues effectively, thereby potentially improving clinical outcomes for patients with DMD.

The clinical trial involves a total of **12 participants** diagnosed with **Duchenne Muscular Dystrophy**. The study population consists exclusively of male subjects, aged between 4 and 10 years, who are ambulatory and able to walk independently without assistive devices. Participants were selected based on a clinical diagnosis of Duchenne Muscular Dystrophy resulting from a documented dystrophin mutation in the DMD gene amenable to exon 51 skipping. All participants are currently receiving treatment with oral corticosteroids or vamorolone and have been on a stable dose for at least 12 weeks prior to the baseline. The trial does not include female subjects and focuses on a vulnerable population. Participants are not currently dependent on daytime ventilators and are not expected to require mechanical or noninvasive ventilation within the next year. Normal urinalysis at screening is required, with trace protein being permissible. The trial aims to assess the safety and tolerability of BMN 351 at different dose levels in this specific population.

The clinical trial is a **Phase 1/2**, open-label, dose escalation study designed to evaluate the safety, tolerability, pharmacokinetics, and pharmacodynamics of multiple intravenous doses of BMN 351 in participants with **Duchenne Muscular Dystrophy**. The trial is not categorized as low intervention and is classified as a Category 2 trial, in accordance with EMA guidance. The study is expected to commence recruitment on November 30, 2023, and conclude by August 30, 2026. Participants will be involved in the study for a duration that aligns with the trial's timeline, subject to their continued eligibility and adherence to study protocols.

The trial involves a series of study visits, beginning with an inclusion (screening) visit to confirm eligibility based on criteria such as age, clinical diagnosis, ambulatory status, and current treatment regimen. Participants must be male, aged 4 to 10 years, with a documented dystrophin mutation amenable to exon 51 skipping. The screening visit will also include assessments like urinalysis and a timed 10-meter walk/run test. Following successful screening, participants will undergo multiple study visits for dose administration and monitoring. These visits will include physical examinations, safety laboratory tests, ECGs, and echocardiography to assess primary endpoints related to safety and adverse events.

Secondary endpoints will focus on the pharmacokinetics of BMN 351, including plasma and urine levels, as well as muscle concentration. The end-of-study visit will mark the conclusion of the participant's involvement, with final assessments to ensure safety and gather comprehensive data. Participants may be withdrawn from the study early if they no longer meet eligibility criteria, experience significant adverse events, or if the investigator deems it necessary for their safety. The study is conducted with rigorous adherence to ethical standards and regulatory requirements, ensuring the integrity and reliability of the collected data.

The clinical trial involves the administration of **Exon 51 specific phosphorothioate oligonucleotide**, also known by its sponsor product code **BMN 351**. This experimental medication is provided in the form of a **concentrate for solution for infusion**. The active substance, **BMN 351**, is a nucleic acid-based compound developed by BioMarin Pharmaceutical Inc. The route of administration for this investigational product is via **intravenous infusion**. The study is designed to evaluate multiple doses, although specific dosing schedules and maximum daily or total dose amounts are not detailed in the provided data. The trial aims to assess the safety, tolerability, pharmacokinetics, and pharmacodynamics of BMN 351 in participants diagnosed with **Duchenne Muscular Dystrophy** (DMD).

In this study, no non-experimental treatments such as standard-of-care therapy, placebo, or comparator treatments are mentioned. The focus remains solely on the investigational product, BMN 351. Participant compliance with the dosing regimen will be monitored throughout the trial, although specific compliance monitoring strategies are not outlined in the available information. The trial is structured as a Phase 1/2, open-label, dose-escalation study, which indicates that participants and investigators are aware of the treatment being administered, and doses may be adjusted based on observed safety and tolerability outcomes.

Efficacy in this clinical trial will be assessed through a series of primary and secondary endpoints. The primary endpoints focus on safety and tolerability, which include the incidence of adverse events, serious adverse events, and adverse events of special interest. Additionally, physical examinations, safety laboratory test parameters, electrocardiogram (ECG) parameters, and echocardiography will be utilized to evaluate these aspects. These assessments are crucial for determining the safety profile of the investigational product, **BMN 351**, in participants with Duchenne Muscular Dystrophy.

The secondary endpoints will involve pharmacokinetic (PK) evaluations, specifically measuring BMN 351 plasma PK, urine PK, and its concentration in muscle tissue. These measurements will provide insights into the drug's absorption, distribution, metabolism, and excretion, which are essential for understanding its pharmacodynamic effects. The trial is designed as an open-label, dose-escalation study, allowing for the collection of comprehensive data on the drug's efficacy and safety across different dose levels. The schedule for these assessments will be aligned with the trial's protocol, ensuring systematic data collection and analysis throughout the study duration.