DUBLIN – Sanofi SA is paying €120 million (US$127 million) up front and could pay up to €495 million more in development and commercial milestones for a 50 percent share in the economics of Astrazeneca plc's MEDI8897, a next-generation successor to its longstanding Synagis (palivizumab) franchise for preventing respiratory syncytial virus (RSV) infection in at-risk infants.