Duchenne Muscular Dystrophy (DMD) is a severe, progressive muscle-wasting disease characterised by mitochondrial dysfunction, loss of muscle strength and difficulty in movement from 2-3 years old. There is a huge urgent and unmet clinical need for this condition. To address this, we have developed a library of novel small molecule mitochondriotropic agents for use in neuromuscular disease. After structural, physicochemical and pharmacological optimisation including stability, ADME, toxicology and in vivo plasma and target tissue PK we identified Myo2 and Myo4 as lead compounds. Therefore, we investigated Myo2 in the D2.B10-Dmdmdx/J murine model of DMD in vivo and Myo2 and Myo4 in DMD patient (Delta52)-derived skeletal myotubes ex vivo and for the first time report our findings. Animals were dosed (1 mg/kg i.p., q.d. or vehicle; n= >7) from 5 weeks of age for 8 weeks. Aged-matched, non-dosed DBA mice were used as a genetic background control. At week 13, soleus muscle was excised, and Absolute Force and Fatigue were determined (standard published protocols). Similarly, mitochondrial membrane potential was determined in isolated gastrocnemius (GN) muscle fibre bundles from these animals. We also assessed mitochondrial efficacy of Myo2 and 4 (3-30 nM) in DMD patient-derived myotubes by fluorimetry (MitoSOX). In D2.B10-Dmdmdx/J animals, Myo2 caused a significant (p<0.05; mixed analysis, unpaired t-test) improvement in muscle strength and lowered fatiguability (Force [mN]) and in GN muscle fibre bundles reversed loss of mitochondrial function (all assays p<0.05; ANOVA, post-hoc Bonferroni c.f. vehicle-treatment). Similarly, in Delta52 patient-derived myotubes, Myo2 and Myo4 at concentrations measured in skeletal muscle after systemic dosing, significantly lowered mitochondrial oxidant production in a concentration-dependent manner (p<0.05; ANOVA, post-hoc Bonferroni c.f. vehicle-treatment). Our studies clearly show successful functional (skeletal muscle) and target (mitochondrial) engagement of Myo2 and Myo4, highlighting the therapeutic potential of small molecule skeletal muscle penetrating mitochondriotropic agents in DMD, and related dystrophies. We are progressing Myo2, Myo4 and other lead molecules through pre-clinical development.