Evaluate the Efficacy and Safety of EN001 in Patients With Duchenne Muscular Dystrophy

A Multi-center, Randomized, Double-blind, Placebo-controlled, Phase 1/2 Trial to Evaluate the Efficacy and Safety of EN001 in Patients with Duchenne Muscular Dystrophy

This clinical trial is a multi-center study conducted in two phases: Phase 1 and Phase 2. Phase 1 follows a 3+3 dose-escalation design to assess the safety, efficacy, and tolerability of EN001, an investigational product. Phase 2 evaluates the efficacy and safety of EN001 at the recommended phase 2 dose (RP2D), as determined in Phase 1, compared to a placebo.

Phase 1 is designed using the traditional 3+3 dose-escalation method to determine the maximum tolerated dose (MTD) and establish the RP2D. Dose escalation continues until the MTD is identified, which must be within the maximum planned dose (MPD) of 2.5 x 10\^6 cells/kg (Cohort 2) or lower. The MTD is defined as the highest dose at which the incidence rate of dose-limiting toxicity (DLT) is less than 33%. To determine the MTD, 3-6 subjects are enrolled in each dose cohort. They receive EN001 every 6 weeks for 3 cycles, with DLTs evaluated up to the 2-week time point (Visit 7).

The Safety Review Committee (SRC) consists of the coordinating Investigator, the responsible trial monitor for subjects enrolled in cohorts requiring safety review, and the sponsor. These members participate as committee members. At the conclusion of each cohort-defined as the endpoint of the DLT assessment for the last subject in that cohort-they comprehensively review the safety data for EN001. The committee makes decisions related to dose adjustments, whether to increase or decrease the dose, and ultimately determines the RP2D.

Phase 2 clinical trials are randomized, double-blind, placebo-controlled clinical trials.

In phase 2, eligible subjects will be randomly assigned to the test group (recommended phase 2 dose (RP2D) of EN001) or the control group (placebo of EN001) in a 1:1 ratio. Efficacy and safety will be evaluated up to 48 weeks after EN001 administration compared to placebo.

In addition, test subjects participating in phase 1 and phase 2 will be followed up for safety and effectiveness for 5 years from the time of EN001 administration according to the long-term follow-up protocol.

Eligibility Criteria:
Inclusion Criteria:

1. Males aged between 6 and 11 years at the time of providing written consent.
2. Individuals exhibiting phenotypic signs of Duchenne Muscular Dystrophy (DMD), such as lower limb muscle weakness, a duck walk, or Gower's sign, and who are diagnosed with DMD following confirmation of a dystrophin gene mutation through genetic testing.
3. Participants who meet the Time to Stand Test (TTSTAND) criteria without the use of assistive devices or help from others during screening and baseline assessments:

   * Phase 1: Capable of completing the TTSTAND evaluation.
   * Phase 2: TTSTAND time of 10 seconds or less.
4. Participants with a 6-Minute Walk Test (6MWT) result of 75 meters or more at screening and baseline.
5. Individuals who meet the following laboratory test criteria at the time of screening and baseline:

   * Hemoglobin ≥10 g/dL
   * Platelet ≥50,000/μL
   * Serum albumin ≥2.5 g/dL
   * Gamma glutamyl transferase (γ-GT) and total bilirubin ≤ upper limit of normal (ULN)
   * Serum creatinine ≤ 1.5 x ULN
6. Participants who have been on a stable dose of glucocorticoids for at least 12 weeks prior to screening, with treatment maintained. Dosage adjustments for body weight changes are allowed.
7. Individuals who, along with their representatives when applicable, have voluntarily agreed in writing to participate in this clinical trial.

Exclusion Criteria:

1. Individuals with confirmed comorbidities at the time of screening:

   * Left ventricular ejection fraction (LVEF) below 50%, as determined by echocardiography
   * Percent predicted forced vital capacity (FVC%) less than 35%
   * Positive for Hepatitis B surface antigen (HBsAg). However, individuals undergoing interferon or antiviral treatment can register
   * Positive for Hepatitis C virus antibody (HCV Ab). Registration is possible if the HCV ribonucleic acid (RNA) test result is negative
   * Positive for Human immunodeficiency virus (HIV) antibody
   * Comorbidities that are uncontrollable or require treatment that could affect the safety and efficacy evaluation of this clinical trial, based on the investigator's judgment
2. Individuals with confirmed treatment history at the time of screening:

   * Administration of cell therapy or gene therapy throughout life
   * Administer antisense oligonucleotide (e.g., exon skipping treatment) or stop- codon readthrough treatment (e.g., aminoglycoside, ataluren) within 24 weeks before screening.
   * Administration of the following medications within 12 weeks before screening: Idebenone, Resveratrol, Adenosine triphosphate
   * Administration of the following medications within 12 weeks before screening. However, registration is possible if the drug is being administered at a stable dose for at least 12 weeks before screening and the dose is expected to remain unchanged during the clinical trial period. Angiotensin-converting enzyme (ACE) inhibitor Angiotensin II receptor blocker (ARB) Beta-blocker Aldosterone antagonist Ivabradine Sacubitril Growth hormone Anabolic steroids
   * Major surgery within 12 weeks before screening or expected major surgery during the clinical trial period.
   * Use of other investigational products (or medical devices) within 4 weeks before screening.
   * Use of systemic immunosuppressants other than systemic glucocorticoids.
3. Individuals requiring mechanical ventilation during the day.
4. Persons with hypersensitivity to the components of the clinical investigational products.
5. Individuals unwilling to use appropriate contraception from the date of written consent to the termination visit:

   * Appropriate contraceptive methods are as follows, and use more than one method.

     * The use of hormonal contraceptives by the partner
     * Implantation of an intrauterine device or system in your partner
     * Sterilization or surgical procedures for you or your partner
6. Others who, in the investigator's discretion, are not willing or able to comply with the clinical trial procedures.