Charcot-Marie-Tooth disease type 1A (CMT1A) is a disease for which no drug treatments are available. Passage et al. reported that ascorbic acid reduced the mRNA level of PMP22, improved motor function and increased the numbers of myelinated peripheral nerve axons in a mouse model of CMT1A. Based on these results, five clinical trials were undertaken at different centers worldwide. However, none of them demonstrated significant effectiveness. Although these outcomes were disappointing, these studies have provided many useful insights for conducting the next randomised controlled trial for CMT1A.