DEERFIELD — Horizon Pharma Inc. plans to buy the privately held Vidara Therapeutics International Ltd. in a cash-and-stock deal that will add the immune system disorder drug Actimmune to the specialty drugmaker’s product portfolio.
Shares of Horizon soared in premarket trading Wednesday after the Deerfield company said it will pay about $660 million in a deal that creates an Ireland-based company named Horizon Pharma PLC.
Vidara shareholders will receive $200 million in cash and retain about a 26 percent stake in Horizon Pharma PLC.
Horizon Chairman and CEO Timothy P. Walbert will keep those titles with the combined company.
Vidara has operations in both Dublin and the United States. It bought Actimmune from InterMune Inc. in 2012 for $55 million. The drug tallied nearly $59 million in sales for Vidara last year.
Walbert said in a statement that the addition of Actimmune complements his company’s business model, which focuses on promotions to primary care doctors and specialists. Horizon’s portfolio already includes Vimovo, which is approved as a treatment for symptoms of osteoarthritis and rheumatoid arthritis.
The company also said the deal gives it a “tax efficient corporate structure” to support growth and acquisitions.
Horizon said the boards of both companies have unanimously approved the acquisition, which is expected to close in the middle of the year.
Shares of Horizon were up nearly 20 percent, or $2.92, to $17.60 in premarket trading more than an hour before markets opened Wednesday. That would easily top the company’s all-time high price during regular trading of $14.75, which the stock reached Tuesday.
The shares have nearly doubled in value since closing 2013 at $7.62.