Mitochondria morphology and organization were examined in electron microscope micrographs of gastrocnemius muscle sections of WT mice, SOD1G93A mice, and SOD1G93A mice treated with P110. Scale bar: 2 μm.H&E‐stained gastrocnemius muscle sections of terminal stage SOD1G93A mice with and without P110 treatment, muscle fibers presenting pathological alterations including atrophy, hypertrophy, round fibers, and fibers with central nuclei. 4‐HNE‐stained gastrocnemius muscle sections show increased staining in SOD1G93A mice as compared to either WT or P110‐treated mice. Scale bar: 50 μm.Muscle from vehicle‐TAT‐treated G93A mice shows several disarranged areas with a significant increase in intersarcomeric area containing a few mitochondria, these effects being greatly reversed by P110. At least 40 mitochondria were analyzed in each group by an observer blinded to the experimental conditions.In line with the preservation of mitochondrial architecture, P110 significantly reduces the percentage of altered mitochondria. At least 40 mitochondria were analyzed in each group by an observer blinded to the experimental conditions.Quantitation of muscle fibers diameter in gastrocnemius muscle sections.Quantitation of 4‐HNE in gastrocnemius muscle sections of terminal SOD1G93A mice.Data information: Treatment with vehicle‐TAT or P110 at 3 mg/kg/day using Alzet 28‐day pumps with pumps replaced at 120 days. Mean, standard deviation, and P‐values are shown. (C–F) n = 5 for WT mice; n = 5 for G93A ALS mice + TAT; n = 5 for G93A ALS mice + P110; probability by one‐way ANOVA (with uncorrected Fisher's LSD post hoc test).