Sanofi has promised up to US$805 M to Principia Biopharma in return for licensing global rights to a Phase I drug that has potential in the treatment of multiple sclerosis (MS) and other neurological disorders. PRN2246 is a Bruton’s tyrosine kinase(BTK) inhibitor that can permeate the blood-brain barrier and modulate immune cell and brain cell signalling. Sanofi already successfully markets two MS drugs: Aubagio® (teriflunomide) and Lemtrada® (alemtuzumab).