What's Happening?
Sanofi has encountered a significant setback with its oral BTK inhibitor, tolebrutinib, which is under development for treating multiple sclerosis (MS). The drug failed to meet its primary endpoint in a Phase
3 trial for primary progressive multiple sclerosis (PPMS), a condition affecting about 10% of MS patients. The trial, known as PERSEUS, involved 767 patients aged 18 to 55 who had a confirmed PPMS diagnosis and either limited access to or an insufficient response to Roche's Ocrevus. As a result of the trial's disappointing outcome, Sanofi has decided not to pursue regulatory registration for PPMS. This development could benefit Roche, whose rival drug fenebrutinib has shown positive results in Phase 3 trials for both relapsing MS and PPMS. Despite this setback, Sanofi is continuing with its filing for tolebrutinib in non-relapsing secondary progressive MS (nrSPMS) based on positive results from the HERCULES trial.
Why It's Important?
The failure of tolebrutinib in the PPMS trial is a blow to Sanofi's efforts to expand its presence in the MS treatment market, particularly in the progressive forms of the disease where there is a significant unmet need. The decision not to pursue PPMS registration could shift competitive advantage to Roche, which is advancing its own BTK inhibitor, fenebrutinib. This development also impacts Sanofi's strategic positioning, as the company had invested heavily in acquiring tolebrutinib through a $3.7 billion buyout of Principia Biopharma. The outcome of the trial has affected investor confidence, as reflected in a drop in Sanofi's share price. The broader implications for the MS treatment landscape include a potential delay in the availability of new therapies for progressive MS, which could affect patients seeking alternative treatment options.
What's Next?
Sanofi plans to continue its efforts with tolebrutinib for nrSPMS, having submitted an expanded access protocol and awaiting further guidance from the FDA by the end of the first quarter of 2026. The company is likely to focus on securing approval in this indication, which represents a larger patient population than PPMS. Meanwhile, Roche is expected to proceed with regulatory filings for fenebrutinib, potentially strengthening its position in the MS market. The competitive dynamics in the MS treatment space will be closely watched, as other pharmaceutical companies may also seek to develop or advance alternative therapies for progressive forms of MS.
