A bid for Allergan, which has a market value of $113 billion, would be Pfizer’s second attempt to acquire a European rival, following its unsuccessfully courtship last year of Anglo-Swedish pharmaceuticals group AstraZeneca Plc (AZN.L). After six months of negotiation, AstraZeneca rejected Pfizer’s final bid in May 2014. The potential for lowering Pfizer’s tax bill by switching its headquarters from the United States to the United Kingdom was touted by Chief Executive Officer Ian Read as a key reason for the deal.