Sanofi has agreed to develop Principia Biopharma Inc.‘s experimental oral treatment that shows promise in multiple sclerosis and, potentially, other central nervous system diseases.   The treatment, Bruton’s tyrosine kinase inhibitor (PRN2246), is designed to access the brain and spinal cord by crossing the blood-brain barrier and impact immune cell and brain cell signaling.    Under the deal, Sanofi will pay a $40 million upfront payment, along with future milestone ...