Evaluation of ENTR-601-44 in Duchenne Muscular Dystrophy Patients Amenable to Exon 44 Skipping: A Randomized, Double-Blind, Placebo-Controlled Study

The primary objective of this study is to evaluate the **safety** and tolerability of ENTR-601-44 in participants with **Duchenne Muscular Dystrophy** (DMD) amenable to exon 44 skipping. 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 development of effective treatments for DMD.

Secondary objectives include:

• Characterizing the **pharmacokinetics** of ENTR-601-44 in participants with DMD, which will provide insights into the drug's absorption, distribution, metabolism, and excretion.
• Characterizing the **pharmacodynamics** of ENTR-601-44, which will help understand the drug's biological effects and mechanism of action in the body.
• Evaluating the **immune response** to ENTR-601-44, which is important to assess potential immunogenicity and its implications for long-term treatment.

The clinical trial involves a total of **15 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 44 skipping. The trial specifically targets an ambulatory population, as participants must be able to perform the Performance of the Upper Limb v2.0 (PUL 2.0) test. The study includes a vulnerable population, indicating that special considerations are in place to ensure the safety and ethical treatment of participants. The selection criteria also require adequate muscle tissue for biopsy, as assessed by the investigator. Lifestyle factors such as diet and physical activity are not specified in the available data.

The clinical trial is designed as a **randomized**, **double-blind**, **placebo-controlled** study to evaluate the safety, tolerability, pharmacokinetics, and pharmacodynamics of **ENTR-601-44** in participants with **Duchenne Muscular Dystrophy** (DMD) amenable to exon 44 skipping. The trial is structured in two parts: Part A involves multiple ascending doses 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 January 4, 2027.

Participants will undergo a series of study visits, beginning with a screening visit to confirm eligibility based on criteria such as a genetic diagnosis of DMD and specific age and ambulatory status requirements. Following successful screening, participants will be randomized to receive either the investigational product, ENTR-601-44, or a placebo, both administered via **intravenous infusion**. The study will include regular follow-up visits to monitor the incidence and severity of treatment-emergent adverse events, changes in vital signs, clinical laboratory results, ECG parameters, and physical examination findings. Secondary endpoints will assess the concentration of ENTR-601-44 in plasma, muscle, and urine, as well as changes in dystrophin expression and exon 44 skipping in muscle biopsy samples.

The expected duration of participant involvement in the trial is contingent upon the completion of all scheduled visits and assessments, with the possibility of early termination if significant adverse events occur or if the participant no longer meets the study criteria. The end-of-study visit will involve a comprehensive evaluation to assess the primary and secondary endpoints, ensuring a thorough analysis of the investigational product's impact on the participants. The trial's design and procedures are meticulously crafted to ensure the collection of robust and reliable data, contributing to the understanding of ENTR-601-44's potential therapeutic benefits for individuals with Duchenne Muscular Dystrophy.

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

In addition to the experimental treatment, the study utilizes **Sodium Chloride** as a comparator treatment. **Sodium Chloride** is also provided as a **solution for infusion** and administered via **intravenous infusion**. It serves as a placebo in the trial, allowing for a double-blind, placebo-controlled study design. The active substance, **Sodium Chloride**, is of chemical origin and is sourced locally as per the study's requirements. The administration and dosing of **Sodium Chloride** are aligned with the study protocol to maintain consistency and reliability in the trial outcomes.

The efficacy of the investigational product **ENTR-601-44** in the clinical trial will be assessed through a series of secondary endpoints. These include the measurement of plasma, muscle, and urine concentrations of **ENTR-601-44** and its final metabolite. Additionally, changes from baseline in dystrophin levels will be evaluated using Western blot analysis from muscle biopsy samples at the end of the study. The expression and localization of dystrophin will also be assessed from muscle biopsy samples, with a focus on the percent change from baseline in exon 44 skipping. Furthermore, the presence of anti-drug antibodies (ADA) and anti-dystrophin antibodies in serum will be monitored.