UPDATE 4-Pfizer set to buy Allergan for more than $150 bln-sources
November 22, 2015 at 22:24 PM EST
Nov 22 (Reuters) - Pfizer Inc secured formal board approval on Sunday for its acquisition of Botox maker Allergan Plc for more than $150 billion, a deal that will create the world's biggest drug maker, according to people familiar with the matter.