RecruitingPhase 2Drug trialNS-089/NCNP-02-201 in Boys With Duchenne Muscular Dystrophy (DMD)This is a Phase 2, open-label, multi-center, 2-part study of NS-089/NCNP-02 administered by weekly IV infusion to ambulant boys aged ≥4 to \<15 years with DMD due to mutations amenable to exon 44 skipping. Participants will receive a selected dose of NS-089/NCNP-02 administered once weekly. The study consists of 2 parts: Part 1 and Part 2. Six participants (Cohort 1) will participate in both Part 1 and Part 2, and 14 participants (Cohort 2) will be added for Part 2.