U.S. drugmaker AbbVie Inc bought Dublin-based Shire Plc on Friday in a 32 billion pound ($54.7 billion) deal that will allow it to slash its tax bill by relocating to Britain. The London-listed company, which makes expensive medicines to treat rare diseases, fought off four earlier bids from AbbVie until the U.S. firm raised its price to 52.48 pounds per share – made up of 24.44 pounds in cash and 0.8960 new AbbVie shares. Chicago-based AbbVie is buying Shire to cut both its U.S. tax bill and its reliance on arthritis drug Humira, the world’s top selling medicine which loses U.S.