French healthcare company Sanofi S.A. (Euronext Paris:SAN) (Nasdaq:SNY) announced on Tuesday that the US Food and Drug Administration (FDA) has accepted the regulatory submission of tolebrutinib for priority review to treat non-relapsing secondary progressive multiple sclerosis (nrSPMS) and slow disability accumulation independent of relapse activity.

The FDA's target action date for a decision is 28 September 2025. A regulatory submission is also under review in the European Union.

If approved, tolebrutinib would be the first brain-penetrant Bruton's tyrosine kinase (BTK) inhibitor to treat nrSPMS and target smouldering neuroinflammation, a key driver of disability accumulation in multiple sclerosis. The FDA granted breakthrough therapy designation to tolebrutinib following positive results from the HERCULES phase 3 study in adults with nrSPMS.

The US and EU submissions are supported by data from the HERCULES phase 3 study in nrSPMS and the GEMINI 1 and 2 phase 3 studies in relapsing multiple sclerosis. Additionally, the PERSEUS phase 3 study evaluating tolebrutinib in primary progressive multiple sclerosis is ongoing, with results expected in the second half of 2025.

Tolebrutinib remains under clinical investigation, and its safety and efficacy have not yet been evaluated by any regulatory authority.