Sanofi SA’s brain-penetrant Bruton's tyrosine kinase (BTK) inhibitor, tolebrutinib, met the primary endpoint in the phase III Hercules trial in non-relapsing secondary progressive multiple sclerosis (nrSPMS). The first compound to show reduction in disability accumulation in MS, tolebrutinib delayed the time to onset of confirmed disability progression in people with nrSPMS, a population for which there are currently no approved therapies.