Paris – sanofi faced a setback in its efforts to bring a new treatment to market for progressive multiple sclerosis, as the U.S. Food and Drug Governance issued a Complete Response letter for tolebrutinib. The decision, announced December 24, delays potential U.S. approval for the drug and follows a recent failure in a Phase 3 study for primary progressive MS, adding to challenges for Sanofi‘s neurology pipeline. While tolebrutinib has received provisional approval in the United Arab Emirates, the company anticipates receiving further guidance from the FDA by the end of the first quarter of 2026.
Sanofi Provides Update on Tolebrutinib Regulatory Submission in Progressive Multiple Sclerosis
Paris, December 24, 2025 – Sanofi announced today that the U.S. Food and Drug Administration (FDA) has issued a Complete Response Letter regarding the marketing application for tolebrutinib, intended for the treatment of secondary progressive multiple sclerosis (SPMS) in adults.
The company provided an update on the ongoing review process on December 15, 2025, stating that the FDA anticipates the review will extend beyond the previously communicated revised target action date of December 28, 2025. Sanofi also expects to receive further guidance from the FDA before the end of the first quarter of 2026. Additionally, at the FDA’s request, Sanofi has submitted a protocol for an expanded access program for tolebrutinib in SPMS, following recent discussions with the agency.
“The FDA’s decision represents a significant and important shift from previous feedback Sanofi had received,” said Houman Ashrafian, Executive Vice President and Head of Research & Development at Sanofi. “We are deeply disappointed with this action. Unrelenting disability progression remains a major unmet medical need in multiple sclerosis, and tolebrutinib had previously been granted Breakthrough Therapy designation by the FDA in recognition of its potential to address this critical need. We believe the FDA should also consider the input of scientific experts, clinicians, and patients on this matter to ensure all perspectives are considered. We remain committed to working with the FDA to find a path forward for tolebrutinib and, ultimately, serve the multiple sclerosis patient community.”
Tolebrutinib received provisional approval in the United Arab Emirates in July 2025 for the treatment of SPMS and to slow the accumulation of disability independent of relapse activity in adults. The drug is currently under regulatory review in the European Union and other jurisdictions globally. Sanofi’s shares traded on EURONEXT: SAN and NASDAQ: SNY.
Financial Considerations
As announced on December 15, 2025, Sanofi is performing an impairment test in accordance with IFRS (IAS 36) on the value of the intangible asset related to tolebrutinib, the status of which will be communicated with the fourth quarter and full year 2025 results in January 2026. The outcome of this test will have no impact on the net income/earnings per share of activities, and the financial outlook for 2025 remains unchanged.
About Tolebrutinib
Tolebrutinib is a brain-penetrating Bruton’s tyrosine kinase inhibitor. This investigational oral medication is specifically designed to target underlying neuroinflammation, a key driver of disability progression in MS. Its mechanism addresses the underlying pathology of progressive MS by targeting inflammatory processes that contribute to neurodegeneration and disability accumulation.
The development of tolebrutinib reflects Sanofi’s commitment to developing innovative treatments that address the root causes of neurological diseases and potentially transform the therapeutic landscape. At the intersection of neurology and immunology, Sanofi is focused on improving the lives of people with serious neuro-inflammatory and neurodegenerative diseases, including MS, chronic inflammatory demyelinating polyneuropathy, Alzheimer’s disease, Parkinson’s disease, and age-related macular degeneration. The company’s neurology pipeline currently includes several projects in Phase 3 studies for various indications.
For more information about the clinical trials of tolebrutinib, please visit clinicaltrials.gov.
About Sanofi
Sanofi is a global biopharmaceutical company driven by innovation in R&D and a large-scale deployment of artificial intelligence to improve people’s lives and deliver long-term growth. We apply our deep understanding of the immune system to invent medicines and vaccines that treat and protect millions of people worldwide, with an innovative pipeline that could benefit millions more. Our team is guided by a single purpose: to chase the miracles of science to improve people’s lives – inspiring us to drive progress and have a positive impact for our collaborators and the communities we serve, tackling the most urgent health, environmental, and societal challenges of our time.
Sanofi is listed on EURONEXT: SAN and NASDAQ: SNY
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