In a move that Sanofi SA said will bring it an mRNA-based research platform with applications in oncology, immunology and other diseases, the company has acquired Tidal Therapeutics Inc. for $160 million up front and up to $310 million in milestone payments. The preclinical startup, led by Merrimack Pharmaceuticals Inc. and Torque Therapeutics Inc. co-founder Ulrik Nielsen, is based in Cambridge, Mass.