Merck says it is buying Inspire Pharmaceuticals for about $430 million in a move to expand its product portfolio with treatments for eye conditions.
Inspire makes Azasite, which is a treatment for pinkeye cause by bacteria, and the dry-eye treatment Restasis, which is sold by Allergan.
New Jersey-based Merck & Co. is paying $5 per share, a 26 percent premium to Inspire's closing price on Monday.
Inspire's board recommended that its shareholders tender their shares in the deal. Warburg Pincus Private Equity IX L.P., which owns about 28 percent of the outstanding shares of Raleigh, N.C.-based Inspire, says it will tender its shares.
Inspire Pharmaceuticals Inc. shares rose $1 to $4.98 in morning trading Tuesday.