March 19 (Reuters) - Horizon Pharma Inc said it would buy privately held specialty pharmaceutical company Vidara Therapeutics International Ltd through a reverse merger for stock and cash valued at about $660 million.

Horizon Pharma said the resulting company, Horizon Pharma Plc, would be 26 percent owned by shareholders of Vidara, which has operations in Ireland and the United States.

(Reporting By Vrinda Manocha in Bangalore; Editing by Sriraj Kalluvila)