Houman Ashrafian

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The BTK inhibitor race for multiple sclerosis

Leading Sanofi's response to FDA rejection

The FDA rejected Sanofi's tolebrutinib for progressive MS on December 28, 2025—a crushing blow for a drug that had won Breakthrough Therapy status and became the first BTK inhibitor approved anywhere in the world. Meanwhile, Roche's rival drug fenebrutinib is racing toward approval after strong Phase 3 results, and Merck's evobrutinib crashed out entirely. Three pharma giants bet billions that brain-penetrating BTK inhibitors could finally slow the relentless neurodegeneration that leaves MS patients in wheelchairs, and only one looks likely to reach the finish line first.

Updated May 16

Notable Quotes

We are very disappointed by the FDA's action. Disability progression remains a large unmet medical need in MS, and tolebrutinib was awarded breakthrough therapy designation in recognition of its potential to address this critical gap.

from The BTK inhibitor race for multiple sclerosis · Updated May 16

Today's FDA decision is a significant and meaningful change in direction from the feedback the agency previously provided to Sanofi. We are very disappointed by the FDA's action. Disability progression remains a large unmet medical need in MS, and tolebrutinib was awarded breakthrough therapy designation in recognition of its potential to address this critical gap.

from The BTK inhibitor race for multiple sclerosis · Updated May 16