The $70-billion purchase of Botox maker Allergan Inc. of Irvine by Irish company Actavis closed on Tuesday.
Allergan's longtime leader, David E.I. Pyott, will not have a position at Actavis, which is expected to take the Allergan name later this year, pending shareholder approval.
The combination creates one of the 10 largest pharmaceutical companies in the world, in terms of revenue, Actavis said in a news release. The new company estimates it will reach $23 billion in sales this year.
In November, Actavis agreed to buy Allergan for a combination of cash and stock that was valued then at $66 billion. The sale price increased as Actavis' stock gained value, in part because Wall Street embraced the deal.
Actavis stock gained $2.51, or 1%, to $307.51 on Tuesday.
"They bought a very good asset and people are beginning to realize it," said industry analyst Aaron "Ronny" Gal, who covers Allergan and Actavis for Bernstein Research.
Actavis, headquartered in Dublin, is a global pharmaceutical company that specializes in both generic and branded medicines.
"We are creating an unrivaled foundation for long-term growth," said Brent Saunders, chief executive of Actavis.
Actavis won a bidding war to acquire Allergan, which spent about six months fighting a takeover bid by Canadian company Valeant Pharmaceuticals International Inc. and its partner, activist investor Bill Ackman.
Allergan had opposed Valeant's offer in part because the Canadian company had vowed to slash its research budget, a move that would have meant the elimination of hundreds of high-paying jobs in Orange County.
Actavis has said it will also impose some cuts, but not as far-reaching as those Valeant had planned.
In December, Actavis disclosed that it did not intend to retain many of Allergan's top executives.
On Tuesday, Pyott said in a statement that he would continue to serve as chairman of the Allergan Foundation, a nonprofit charity.
"I am excited for the opportunity to pursue new interests, including my work with a few public company boards, several universities in the U.S. and the U.K. and ophthalmic charities whose goals are to improve eye health in emerging markets," he said.
Pyott, who joined Allergan as CEO in 1998, was one of the longest-tenured chief executives in the pharmaceutical industry. He guided the company to staggering growth, led by its introduction of the Botox wrinkle treatment.
"He essentially created the company," said Shibani Malhotra, a pharmaceutical industry analyst with Sterne Agee. "They were probably the best-run company in our sector."
Allergan, founded in 1950 with a focus on allergy nasal drops, is expected to retain a major presence in Irvine. The new company will spend about $1.7 billion on research and development, Actavis said in the news release. Allergan said it spent $1.2 billion on R&D in 2014, according to a regulatory disclosure.
In addition to Botox, which generated more than $2.2 billion in sales last year, Allergan sold ophthalmic medications and breast implants.