To evaluate the effect of NV189 on patient cells, fibroblasts from a patient with Leigh syndrome due to recessive nuclear DNA mutations in the structural CI gene NDUFS2 and three control cell lines were investigated using a Seahorse Bioscience XFe 96 Extracellular Flux Analyzer (Fig. 3; Supplementary Fig. 5). This evidence concerns the gene NDUFS2 and Leigh syndrome.