Mega deals morph into mega problems for Wall Street

New York

IF 2015 was a dream year for Wall Street's top dealmakers, 2016 is starting to take a nightmarish turn.

Some of the mega transactions that had champagne corks popping in boardrooms are running into antitrust problems and, in the case of pharmaceutical firm Pfizer's US$160 billion takeover of rival Allergan PLC, political opposition to a deal that envisaged the biggest drug company in the United States moving to Ireland to lower its taxes.