Sanofi Dips as Multiple Sclerosis Treatment Misses in Late-stage Trial, Faces US Regulatory Delay

05:28 AM EST, 12/15/2025 (MT Newswires) -- Sanofi (SAN.PA) shares dropped nearly 3% by Monday midday trading in Paris, after announcing negative developments for its multiple sclerosis drug candidate, tolebrutinib. Results from the phase 3 Perseus study showed that tolebrutinib was unable to meet the primary endpoint of delaying time to onset of six-month composite confirmed disability progression in patients with primary progressive multiple sclerosis, or PPMS. The safety profile of the therapy was consistent with previous trials, including the confirmed risk of drug-induced liver injury, which requires strict monitoring. As a result, the drugmaker will not pursue regulatory submission for the use of tolebrutinib in PPMS, which affects 10% of multiple sclerosis patients. "We are disappointed by today's results; however, we do believe that these results will improve our understanding of the underlying disease biology of multiple sclerosis," said Houman Ashrafian, Sanofi executive vice president, head of research and development. "Our commitment to the multiple sclerosis community remains unchanged, as do our efforts to pursue novel advancements that address existing unmet needs and we remain confident in the value tolebrutinib can bring to those living with non-relapsing secondary progressive multiple sclerosis." While remaining committed to the development of tolebrutinib for the non-relapsing secondary progressive multiple sclerosis, or nrSPMS, Sanofi flagged a delay in the US Food and Drug Administration's approval of tolebrutinib for the indication. Citing ongoing talks with the US FDA, the biopharmaceutical company said it expects the regulator to move the previously communicated target action date of Dec. 28, 2025, with guidance anticipated by the end of the first quarter of 2026. As such, the French healthcare group submitted an expanded access protocol for tolebrutinib in nrSPMS, helping eligible patients access the investigational therapy. "We see [tolebrutinib's] PPMS fail as surprising given Roche's fenebrutinib recently hit in this setting vs a tough comparator," analysts at BofA Global Research said. "Visible Alpha consensus currently reflects Eur1.4bn peak sales for Tolebrutinib, we assume mostly from [secondary progressive multiple sclerosis] (bigger opp, with a lower risk adjustment), and a smaller portion from PPMS (our peak sales was split c25% to PPMS/c75% SPMS). Removing tolebrutinib SPMS/PPMS would thus pose a c3% risk to consensus sales," they added. Globally, tolebrutinib was provisionally approved in the United Arab Emirates in July for nrSPMS, while it remains under active regulatory review in the European Union and other jurisdictions internationally.