Horizon Pharma Inc. (Nasdaq: HZNP) is buying Vidara Therapeutics International Ltd. in a deal valued at $660 million.

Vidara, headquartered in Dublin, is a specialty pharmaceutical company that makes Actimmune, a drug approved by the U.S. Food and Drug Administration that is used in patients with chronic granulomatous disease and osteopetrosis.

Deerfield, Ill.-based Horizon Pharma makes medications for arthritis, pain and inflammatory diseases.

Under the terms of the deal, a reverse merger for stock and cash, 74 percent of Horizon Pharma's shares will be exchanged for shares in the new company. Vidara will own 26 percent of the combined company and receive a $200 million cash payment.

The combined company will be called Horizon Pharma plc.

Horizon Pharma secured a $250 bridge loan commitment from Deerfield Management Co. LP.

Advisors Citigroup Global Markets Inc. is Horizon Pharma's financial adviser, with JMP Securities LLC acted as co-financial adviser. Cooley LLP and McCann FitzGerald acted as legal counsel, and KPMG LLP is providing tax advice. Citigroup Global Markets Inc. and Cowen and Co. advised Horizon Pharma on the financing.

Lazard Middle Market provided financial advice to Vidara on the deal, while Mayer Brown LLP, Burke Warren McKay and Serritella PC and A&L Goodbody served as legal advisers.

Other recent pharmaceutical deals include Envision Pharma Group's February purchase of ProScribe, and GVK Biosciences' purchase of Aragen Bioscience, announced in January.