Pfizer-Allergan tie-up news pushes M&A to record level for 2015 By: MarketWatch November 23, 2015 at 13:42 PM EST The $155 billion deal uniting U.S.-based Pfizer with Dublin-headquartered Allergan would be the biggest tax inversion deal ever. Read More >> Related Stocks: Allergan Plc Macy's Pfizer