FDA Sends Complete Response Letter To Sanofi, Delaying Approval of Tolebrutinib For Non-Relapsing SPMS Until More Information Is Provided

The US Food and Drug Administration (FDA) has issued a complete response letter for Sanofi’s new drug application for tolebrutinib, a medicine being developed to treat non-relapsing secondary progressive multiple sclerosis (nrSPMS) in adults. A complete response letter means that the FDA is unable to approve the application in its current form and requires additional information or changes before moving forward.

Sanofi recently shared an update on December 15, 2025, explaining that the FDA’s review was expected to extend beyond the revised target action date of December 28, 2025. The company also mentioned that it anticipated further guidance from the FDA by the end of the first quarter of 2026. In response to a request from the agency, Sanofi submitted an expanded access protocol to allow eligible patients with nrSPMS to receive tolebrutinib while regulatory discussions continue. These updates were based on the latest conversations between Sanofi and the FDA.

After receiving the complete response letter, Sanofi expressed strong disappointment, stating that the decision marks a significant shift from the FDA’s earlier feedback. According to Houman Ashrafian, Executive Vice President and Head of Research and Development at Sanofi, disability progression in multiple sclerosis continues to be a major unmet medical need. He noted that the FDA had previously granted tolebrutinib breakthrough therapy designation because of its potential to help address this challenge. Ashrafian emphasized that Sanofi believes input from scientific experts, clinicians, and patients should be considered to ensure a well-rounded evaluation. The company stated that it remains committed to working with the FDA to determine a clear path forward and ultimately support the MS community.

While progress in the US has slowed, tolebrutinib has advanced in other regions. The drug received provisional approval in the United Arab Emirates in July 2025 for treating non-relapsing secondary progressive multiple sclerosis and for slowing disability build-up that occurs independently of relapses. Regulatory reviews for tolebrutinib are also underway in the European Union and several other countries.

Regarding financial matters, Sanofi previously announced that it is conducting an impairment test on the intangible asset value of tolebrutinib in line with IFRS (IAS 36) requirements. The findings of this assessment will be shared with the company’s fourth-quarter and full-year 2025 results in January 2026. Sanofi confirmed that the outcome of this test will not affect business net income, business earnings per share, or the company’s financial guidance for 2025.

Tolebrutinib is an investigational oral Bruton’s tyrosine kinase inhibitor designed to reach the brain and target smoldering neuroinflammation, which is believed to be a major factor driving disability progression in multiple sclerosis. By addressing these underlying inflammatory processes, the medicine aims to impact the mechanisms that lead to neurodegeneration and long-term disability.

The development of tolebrutinib reflects Sanofi’s commitment to creating new therapies that address the root causes of neurological conditions. The company continues to invest in its neurology research pipeline, which includes several phase 3 programs for disorders such as multiple sclerosis, chronic inflammatory demyelinating polyneuropathy, Alzheimer’s disease, Parkinson’s disease, and age-related macular degeneration.