Sanofi’s MS Drug Failure Sparks Market Concerns Amid Regulatory Delays
Sanofi shares tumbled following a dual setback for its experimental multiple sclerosis treatment tolebrutinib. The PERSEUS phase 3 trial failed to demonstrate efficacy in primary progressive MS patients, while concurrent FDA regulatory delays compounded investor concerns.
The French pharma giant faces mounting pressure as its year-to-date stock decline reaches 15%. While maintaining 2025 financial guidance, Sanofi's retreat from primary progressive MS registration leaves a therapeutic gap for 10% of MS patients who experience irreversible neurological decline.
Market analysts note the timing of these developments creates unusual headwinds for Sanofi's neurology pipeline. The company continues pursuing approval for non-relapsing secondary progressive MS, but confidence in tolebrutinib's commercial potential has clearly eroded.
