Randomized, Double-Blind, Placebo-Controlled Study of ENTR-601-45 in Duchenne Muscular Dystrophy Patients Amenable to Exon 45 Skipping

The primary objective of this study is to evaluate the **safety** and **tolerability** of ENTR-601-45 in participants with **Duchenne Muscular Dystrophy** (DMD) during Part A of the trial. This is clinically relevant as it aims to ensure that the investigational drug is safe for use in this patient population, which is crucial for the progression of therapeutic development for DMD.

Secondary objectives include:

• Characterizing the **pharmacokinetics** of ENTR-601-45 in participants with DMD, which will provide insights into the drug's absorption, distribution, metabolism, and excretion.
• Characterizing the **pharmacodynamics** of ENTR-601-45, which will help understand the drug's biological effects and mechanism of action in the body.
• Evaluating the **immune response** to ENTR-601-45, which is important to assess potential immunogenicity and its implications for long-term treatment safety and efficacy.

The clinical trial involves a total of **10 participants** diagnosed with **Duchenne Muscular Dystrophy** (DMD). The study population includes individuals aged **4 to 20 years**, with both male and female participants being eligible. Participants were selected based on a genetic diagnosis of DMD with a confirmed pathologic variant in the dystrophin gene amenable to exon 45 skipping. The trial population is ambulatory, with adequate muscle for tissue biopsy, as assessed by the investigator. The study considers vulnerable populations, and participants are required to have clinical signs compatible with DMD. Lifestyle factors such as diet and physical activity are not specified in the available data. The selection criteria ensure that participants have a specific Performance of the Upper Limb v2.0 (PUL 2.0) entry item at screening, indicating their ambulatory status. Other protocol-defined criteria apply, but these are not detailed in the provided information.

The clinical trial is a **randomized**, **double-blind**, placebo-controlled study designed to evaluate the safety, tolerability, pharmacokinetics, and pharmacodynamics of **ENTR-601-45** in participants with **Duchenne Muscular Dystrophy** (DMD) amenable to exon 45 skipping. The trial is structured in two parts: Part A involves a multiple ascending dose phase to assess safety and tolerability, while Part B focuses on evaluating the safety and efficacy of the investigational product. The trial is expected to commence recruitment on June 30, 2025, and conclude by October 30, 2028.

Participants will undergo a series of study visits, beginning with an inclusion (screening) visit to confirm eligibility based on criteria such as a genetic diagnosis of DMD, age between 4-20 years, and ambulatory status. The screening will also involve assessments to ensure adequate muscle tissue for biopsy. Following successful screening, participants will be randomized to receive either the investigational product, **ENTR-601-45**, or a placebo, both administered via **intravenous infusion**. Subsequent follow-up visits will be scheduled to monitor safety, tolerability, and pharmacokinetic parameters, including plasma, muscle, and urine concentrations of ENTR-601-45 and its metabolites.

The primary endpoint of Part A is to assess the overall safety and tolerability of ENTR-601-45. Secondary endpoints include changes in dystrophin levels and exon 45 skipping in muscle biopsy samples, as well as the presence of anti-drug and anti-dystrophin antibodies. The end-of-study visit will involve comprehensive evaluations to determine changes from baseline in these parameters. Participant involvement is expected to last throughout the trial duration unless early termination is warranted due to adverse events, non-compliance, or withdrawal of consent. The trial is conducted under a Phase I/II integrated framework, ensuring rigorous assessment of both safety and preliminary efficacy.

The clinical trial involves the administration of **ENTR-601-45**, an experimental medication designed for participants with Duchenne muscular dystrophy amenable to exon 45 skipping. ENTR-601-45 is a **solution for infusion** and is administered via **intravenous infusion**. The active substance in ENTR-601-45 is a conjugate of a DMD exon 44 skipping phosphorodiamidate morpholino oligomer and a cyclic peptide, originating from nucleic acid. The pharmaceutical form is specifically tailored for infusion, ensuring precise delivery of the active compound. The dosing schedule and frequency of administration are determined based on the study protocol, with careful monitoring of participant compliance to ensure adherence to the treatment regimen.

In addition to the experimental treatment, the study utilizes **Sodium Chloride** as a placebo comparator. Sodium Chloride is also provided as a **solution for infusion** and administered through **intravenous infusion**. This chemical compound serves as a control to evaluate the safety and efficacy of ENTR-601-45. The placebo is designed to mimic the administration process of the experimental drug without delivering the active therapeutic agent. Participant compliance with the placebo administration is monitored in parallel with the experimental treatment to maintain the integrity of the study's double-blind design.

The efficacy of ENTR-601-45 in the clinical trial will be assessed during Part B of the study, which is designed to evaluate the safety and efficacy of the investigational product in participants with **Duchenne Muscular Dystrophy** (DMD) amenable to exon 45 skipping. The primary endpoints for efficacy assessment include changes in dystrophin levels and expression, as well as exon 45 skipping efficiency. These will be measured through muscle biopsy samples analyzed by Western blot techniques at the end of the study. Secondary endpoints include the concentration of ENTR-601-45 and its metabolites in plasma, muscle, and urine, as well as the presence of anti-drug and anti-dystrophin antibodies in serum. The collection and analysis of these parameters will provide comprehensive data on the pharmacodynamics and potential therapeutic impact of ENTR-601-45 in the target population.