Phase 1/2a for Safety, PK and PD of SQY51 in Paediatric and Adult Patients Duchenne Muscular Dystrophy (AVANCE1)

INCLUSION CRITERIA FOR PHASE 1: Boys of ≥6 years of age and ≥ 16 kg body weight. Ambulatory or non-ambulatory status, Patients and, if minor, their legal guardians, who are willing and able to comply with scheduled visits, treatment plan, laboratory tests, and other study procedures. Diagnosed with Duchenne Muscular Dystrophy (DMD), genotypically confirmed with DMD mutations amenable to exon-51 skipping. Stable hepatic and renal function. Left ventricular ejection fraction (LVEF) at screening ≥40%. If clinically indicated, approved concomitant treatment within standards of care guidelines for DMD, such as antihypertensive, vasodilators, lipid lowering, thyroid replacement, vitamins, mineral substitution, gastric protectors, and nutritional supplements. Non-invasive mechanical ventilation is permissive if < 16 h/day. Being affiliated with a French social security. Informed consent form signed by the patient or, if minor, by the legal guardian(s). INCLUSION CRITERIA FOR PHASE 2a: Patients must have completed Phase 1 of the study. EXCLUSION CRITERIA FOR PHASE 1 AND 2a: Patient with any serious medical/surgical or psychiatric condition/illness/history that in the opinion of the investigator would jeopardize patient's safety or would interfere with the study assessments/results, including insufficient vaccination against infectious diseases as recommended by national guidelines, medical history of infection with Hepatitis B,C and HIV. Patient with any known allergies to products likely to be used in the study (e.g., antiseptics, anesthetics), known hypersensitivity to any of the ingredients, or excipients of the study drug). Patient who participated in other investigational study within the last three months, including those with investigational drugs that aim at restoring dystrophin expression such as other antisense oligomers. Patient that received gene therapy. Patient with intellectual disability or behavioral problem such that they cannot comply with the study procedure. Patient with advanced cardiomyopathy and LVEF < 40%. Patients with dysrhythmias and being treated for dysrhythmias. Patients with non-treated tachycardia. Patient for which orthopedic surgery is planned during the time of the study. Tracheostomized patients and dependent on invasive mechanical ventilation. Non-invasive mechanical ventilation ≥ 16 h/day. Predicted vital forced capacity < 20%. Medical history with more than two respiratory decompensations requiring hospitalization during the previous year. No respiratory decompensation in the four months preceding enrolment. Patients on medications that can restore dystrophin expression, tamoxifen and other drugs without indication for DMD or paediatric population. Abnormal laboratory values in the clinically significant range.