Sanofi's multiple sclerosis (MS) drug candidate tolebrutinib has shown mixed results in late-stage trials, failing to meet key goals in two studies for relapsing forms of the disease but succeeding in a trial for the less common progressive MS. Specifically, tolebrutinib did not outperform existing treatment Aubagio in reducing relapse rates, which was largely anticipated by analysts. However, in a separate trial, tolebrutinib significantly slowed disability progression in patients with non-relapsing secondary progressive MS, marking a potential breakthrough in treatment options. Sanofi plans to file for regulatory approval by the end of 2024, as the company aims to offset revenue losses post-Aubagio's patent expiration. Despite the setbacks, investor confidence appears to be bolstered by the promising results in progressive MS, as indicated by a recent uptick in share prices. CEO Paul Hudson continues to navigate challenges while striving to enhance the company's drug development pipeline.