Botox maker Allergan, Inc. will be acquired by Actavis plc for $66 billion after fending off a hostile takeover bid by activist investor William Ackman and Valeant Pharmaceuticals International Inc.

Allergan had spent seven months being pursued by Canada's Valeant, whose most recent offer was worth about $54 billion. The company believed that the Valeant deal would lead to significant cuts in research and development spending.

Instead, it opted for a bid by Dublin-based Actavis, whose offer came with only $400 million in R&D cuts for Allergan, much less than the $900 million decrease proposed by Valeant, Reuters reported. The tie-up with Actavis may ensure that some of Allergan's promising experimental eye treatments for macular degeneration and glaucoma remain in the pipeline, the news agency said.

Under the terms of the Actavis offer, the company will acquire Allergan for a combination of $129.22 in cash and 0.3683 Actavis shares for each share of Allergan common stock. That values the company at approximately $219 per Allergan share.

The two companies said that the combination will create one of the top 10 global pharmaceutical groups by sales revenue, with combined annual pro forma revenues of more than $23 billion anticipated in 2015. Together, the companies have leading blockbuster franchises in ophthalmology, neurosciences/CNS, medical aesthetics/dermatology/plastic surgery, women's health, gastroenterology and urology.

Brent Saunders, CEO and president of Actavis, said that the deal will result in double-digit accretion to non-GAAP earnings within the first 12 months.

The transaction remains subject to the approval of shareholders of both companies, as well as regulatory clearance in the United States, the European Union and in certain other jurisdictions. It is expected to be completed in the second quarter of 2015.