Prescription benefits manager Express Scripts Inc. said Monday it is buying health insurer WellPoint Inc.'s NextRX pharmaceutical benefit management subsidiaries for just under $4.68 billion in cash and stock.The deal gives St. Louis-based Express Scripts, the third-largest pharmacy benefits manager with about 506 million prescriptions filled in 2008, an additional 265 million. That would pull it close to the No. 1 stand-alone company, Medco Health Solutions Inc ...