With an eye to sustaining its multiple sclerosis (MS) franchise, Sanofi SA plucked a Bruton's tyrosine kinase (BTK) inhibitor from Principia Biopharma Inc. The Paris-based pharma agreed to pay $40 million up front, with milestone payments that could reach $765 million, for the oral candidate, PRN-2246, which recently became the subject of a phase I study in healthy volunteers.