Pfizer and Allergan’s boards of directors are preparing to approve their merger agreement on Sunday.
Once the deal is approved it will mark the largest merger ever in the healthcare sector.
The deal is valued at more than $150 billion, and would have Pfizer paying 11.3 of its shares for each Allergan share.
The deal will also include a small cash component that will equal less than 10% of the value of the deal, sources tell Reuters.
The deal will be structured as Allergen buying Pfizer, although Pfizer’s CEO, Ian read, will lead the combined companies, while Allergan CEO Brent Saunders would serve as his deputy in an operational role.
Pfizer has been very public with its desire to court a foreign company. Pfizer’s chief executive has repeated said the drug maker wants to flee the United States in order to avoid high U.S. corporate taxes. The merger with Allergen would allow Pfizer to move its corporate address to Ireland.
The Obama Administration is urging Congress to stop such moves, which have become commonplace in recent years.
Obama says the trend of purchasing foreign companies in order to move U.S. operations to other countries, can only be stopped if Congress acts swiftly.
Pfizer and Allergan are not commenting on the details of the merger, which still requires governmental approval.