Medarex and Massachusetts Biologic Laboratories, the University of Massachusetts Medical School's nonprofit unit, agreed to license worldwide rights of CDA-1 and CDB-1, two monoclonal antibodies designed to treat Clostridium difficile infections, to Merck & Co. Under the deal, Medarex and MBL will share a $60 million upfront payment and are entitled to as much as $165 million more in potential milestone fees.