P.129 One-year data from ENDEAVOR, a phase 1b trial of delandistrogene moxeparvovec in boys with DMD

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Delandistrogene moxeparvovec (SRP-9001) is an investigational gene transfer therapy developed for targeted skeletal and cardiac muscle expression of a micro-dystrophin that is being studied in patients with Duchenne muscular dystrophy (DMD). Findings from ongoing Phase 1 and 2 trials demonstrate micro-dystrophin expression in patients treated with delandistrogene moxeparvovec clinical process material. ENDEAVOR (NCT04626674) is a two-part, open-label, Phase 1b study assessing the expression and safety of commercially representative delandistrogene moxeparvovec material in boys with DMD who represent different stages of disease progression. Four cohorts will be evaluated: Cohort 1: ≥4- to <8-year-old ambulatory boys; Cohort 2: ≥8- to <18-year-old ambulatory boys; Cohort 3: non-ambulatory boys; and cohort 4: ≥3- to <4-year-old ambulatory boys. Inclusion criteria include a genetic DMD diagnosis and stable steroid dosing (Cohorts 1 3 only, ≥12 weeks prior to screening). Participants received a single intravenous dose of commercially representative delandistrogene moxeparvovec material. The follow-up period consists of: Part 1, from post-infusion through to week 12, and Part 2, from week 12 through to week 260. The primary outcome measure is the change in micro-dystrophin protein expression from baseline to Week 12 (Part 1). Secondary outcome measures include change in micro-dystrophin expression at the sarcolemma from baseline to week 12 (Part 1) and safety (over 260 weeks). Exploratory functional endpoints include the North Star Ambulatory Assessment and timed function tests (Cohorts 1, 2 and 4) and performance of the upper limb and pulmonary function tests (Cohorts 2 and 3). We present 1-year safety and functional data and 12-week expression data following treatment with commercially representative delandistrogene moxeparvovec material. Delandistrogene moxeparvovec (SRP-9001) is an investigational gene transfer therapy developed for targeted skeletal and cardiac muscle expression of a micro-dystrophin that is being studied in patients with Duchenne muscular dystrophy (DMD). Findings from ongoing Phase 1 and 2 trials demonstrate micro-dystrophin expression in patients treated with delandistrogene moxeparvovec clinical process material. ENDEAVOR (NCT04626674) is a two-part, open-label, Phase 1b study assessing the expression and safety of commercially representative delandistrogene moxeparvovec material in boys with DMD who represent different stages of disease progression. Four cohorts will be evaluated: Cohort 1: ≥4- to <8-year-old ambulatory boys; Cohort 2: ≥8- to <18-year-old ambulatory boys; Cohort 3: non-ambulatory boys; and cohort 4: ≥3- to <4-year-old ambulatory boys. Inclusion criteria include a genetic DMD diagnosis and stable steroid dosing (Cohorts 1 3 only, ≥12 weeks prior to screening). Participants received a single intravenous dose of commercially representative delandistrogene moxeparvovec material. The follow-up period consists of: Part 1, from post-infusion through to week 12, and Part 2, from week 12 through to week 260. The primary outcome measure is the change in micro-dystrophin protein expression from baseline to Week 12 (Part 1). Secondary outcome measures include change in micro-dystrophin expression at the sarcolemma from baseline to week 12 (Part 1) and safety (over 260 weeks). Exploratory functional endpoints include the North Star Ambulatory Assessment and timed function tests (Cohorts 1, 2 and 4) and performance of the upper limb and pulmonary function tests (Cohorts 2 and 3). We present 1-year safety and functional data and 12-week expression data following treatment with commercially representative delandistrogene moxeparvovec material.