SNY Stock Down on Double Trouble With Multiple Sclerosis Drug

Core Insights - Sanofi's shares fell nearly 2% following two setbacks related to its investigational multiple sclerosis (MS) drug, tolebrutinib [1][9] Regulatory Developments - The FDA has extended the review period for Sanofi's filing for tolebrutinib to treat non-relapsing secondary progressive MS (nrSPMS) by three months, now expected to conclude by December 28, 2025 [2][3] - A final decision is anticipated in the first quarter of 2026, with a similar filing under review in the European Union [4] Clinical Setbacks - Sanofi did not meet the primary endpoint in the phase III PERCEUS study for tolebrutinib in primary progressive MS (PPMS), leading to the decision to halt further development in this area [5][6] - The company plans to report full safety and efficacy results from the study at a future medical meeting [6] Market Reaction - Investors expressed concerns about Sanofi's future growth prospects, particularly as tolebrutinib was seen as a key diversification effort beyond the company's reliance on Dupixent [7][8] - Year-to-date, Sanofi's stock has declined by 1%, contrasting with a 16% growth in the industry [8] Historical Context - This is not the first setback for tolebrutinib; in 2022, the FDA placed a partial clinical hold on its phase III studies due to drug-induced liver injury cases [11] - The MG studies for tolebrutinib were discontinued in 2022 after evaluating the competitive treatment landscape [12]