Sanofi announced the closure of an agreement with Principia Biopharma to develop a promising experimental oral treatment for multiple sclerosis (MS) and, potentially, other central nervous system (CNS) diseases. Principia’s Bruton’s tyrosine kinase (BTK) inhibitor (PRN2246) has been designed to access the brain and spinal cord by crossing the blood-brain barrier and impact immune cell and brain cell signalling. PRN2246 is currently in clinical development. Sanofi will pay Principia a $40 million upfront payment, future milestone payments that could total $765 million and royalties on product sales.