Pfizer has agreed to buy Botox maker Allergan in a deal worth more than $150bn (€141bn) - the biggest deal in pharmaceuticals history.
The newly merged entity will be known as Pfizer, following the unanimous approval of the transaction by the boards of directors of the two companies.
This deal will create the world's largest pharmaceutical firm - and it is likely that Pfizer will redomicile to Ireland where Allergan is registered to take advantage of Ireland's low tax rates.
In a statement, the companies announced that "Allergan shareholders will receive 11.3 shares of the combined company for each of their Allergan shares, and Pfizer stockholders will receive one share of the combined company for each Pfizer share".
The companies say the deal marks a 30% premium on Pfizer’s and Allergan’s unaffected share prices as of October 28th.
The deal has been a controversial proposition, and has become a live issue on the 2016 presidential election campaign trail in the United States.
The US Treasury Department has issued a letter on tax inversion deals, saying that it is reviewing means of stopping them taking place. It plans to release a guidance on the matter on Wednesday of this week.
