On Monday, Sanofi SA (NASDAQ:SNY) announced results from the PERSEUS phase 3 study of tolebrutinib compared to placebo for primary progressive multiple sclerosis (PPMS).
Multiple sclerosis is an autoimmune disease resulting in damage to myelin, which is the insulating cover of nerve cells in the brain and spinal cord.
PPMS is a less common, severe form of MS where neurological function steadily worsens from the start, without distinct relapses or remissions, causing gradual disability, especially mobility issues.
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Participants were randomized (2:1) to receive either an oral daily dose of tolebrutinib or a matching placebo for up to approximately 60 months.
The trial did not meet its primary endpoint in delaying time to 6-month composite confirmed disability progression, which represents 10% of the overall multiple sclerosis patient population.
Based on these results, Sanofi will not pursue regulatory registration for primary progressive multiple sclerosis.
Preliminary analysis showed the safety profile was consistent with previous tolebrutinib studies.
As previously reported, drug-induced liver injury (DILI) is an identified risk of tolebrutinib. Strict adherence to liver monitoring requirements and prompt management of liver enzyme elevations are important to mitigate DILI risk.
Tolebrutinib was provisionally approved in the United Arab Emirates in July 2025 for non-relapsing secondary progressive multiple sclerosis and to slow disability accumulation independent of relapse activity in adults.
It is currently under regulatory review in the EU and other jurisdictions worldwide. Tolebrutinib was previously granted breakthrough therapy designation by the FDA in December 2024.
Financial Impact And Impairment Review
Sanofi will conduct an impairment test on the intangible asset value attached to tolebrutinib with a status to be provided for the fourth quarter and fiscal 2025 in January 2026.
The outcome of this test will have no impact on the business net income/business EPS, and there is no change to the financial guidance for 2025.
FDA Update
Sanofi anticipates that the review process for the ongoing U.S. regulatory review of tolebrutinib in non-relapsing secondary progressive multiple sclerosis will extend beyond the previously communicated U.S. target action date of December 28, 2025.
nrSPMS is a form of MS where symptoms gradually worsen over time without distinct flare-ups (relapses) or periods of remission, representing a steady accumulation of neurological damage and disability.
The French firm expects further guidance from the U.S. Food and Drug Administration (FDA) by the end of the first quarter of 2026.
In response to an FDA request, Sanofi has submitted an expanded access protocol for tolebrutinib in non-relapsing secondary progressive multiple sclerosis.
SNY Price Action: Sanofi shares were down 1.77% at $47.82 during premarket trading on Monday, according to Benzinga Pro data.
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