The Irish pharmaceutical company Actavis is buying Allergan for $219 per share in a cash and stock deal valued at $66 billion.
For months, Allergan has worked to fend off a hostile bid from the Canadian pharmaceutical company Valeant and activist investor Bill Ackman.
All of Ackman and Valeant's offers had been rejected. The most recent bid for the Botox-maker was $53 billion.
Even though Valeant was unsuccessful in its takeover attempt, Ackman is still getting a massive payout.
Ackman, who runs Pershing Square Capital, last held 28,878,538 shares of Allergan, according to his fund's most recent 13F filing.
Since he first disclosed his stake back in April, shares of Allergan have surged.
According to our calculations, Ackman has made more than $2.28 billion on his position in Allergan. He started buying Allergan stock back in February, so it's probably even higher.
Ackman doesn't own any shares of Valeant.
Meanwhile, Ackman recently disclosed a large stake in the animal health company Zoetis.
Zoetis is seen as a potential takeover target. Shares of Zoetis were trading up more than 2.10% on Monday.
