Italian drugmaker Chiesi Farmaceutici SpA said it would buy the rest of Cornerstone Therapeutics Inc CRTX.O that it does not already own, valuing the U.S. company at about $255 million.
Chiesi, which currently owns 58 percent of Cornerstone, will buy the remaining shares for $9.50 each.
The offer is below Cornerstone's Friday closing of $9.74, but represents a premium of about 78 percent to the stock's trading level just before Chiesi made its initial written proposal in February.
Shares of Cornerstone were down 3 percent at $9.43.
The deal will give Chiesi, owned by the Chiesi family, a distribution network for all the products it intends to market in the United States. Chiesi makes drugs for respiratory disorders and heart diseases.
Cornerstone also sells drugs to treat diseases such as asthma and heart conditions. It holds licenses to market Chiesi's respiratory drugs, Curosurf and Bethkis, in the United States.
Cornerstone Chief Executive Craig Collard, who owns about 6 percent of the company's outstanding shares, agreed to vote all his shares in favor of the deal.
The company first received a going-private proposal from Chiesi on February 18. The Italian drugmaker had then offered $6.40 to $6.70 per share.
The deal, which has been approved by the boards of both companies, is expected to close in the first quarter of 2014.
Jefferies International Ltd was financial adviser to Chiesi and Lazard advised Cornerstone. Morgan, Lewis & Bockius LLP was Chiesi's legal adviser and Clifford Chance was legal adviser to Cornerstone.
(Reporting by Vrinda Manocha and Esha Dey in Bangalore; Editing by Kirti Pandey)