NEW YORK (AP) -- Forest Laboratories Inc. said Tuesday it is buying specialty pharmaceutical company Clinical Data Inc. in a $1.2 billion deal in order to gain access to a key antidepressant.

Forest is paying $30 per share, a discount of nearly 12 percent from Clinical Data's closing price on Friday. Forest also will pay an extra $6 per share if sales of the recently approved antidepressant, Viibryd, achieve certain milestones.

New York-based Forest makes the blockbuster antidepressant Lexapro, the Alzheimer's disease treatment Namenda and the blood pressure drug Bystolic. It expects the deal will dilute earnings for the next three years and may add to earnings afterward.

The Food and Drug Administration approved Viibryd last month. Clinical Data, based in Newton, Massachusetts, holds exclusive worldwide rights to the drug from Germany-based Merck KGaA. The drug should be available in U.S. pharmacies in the second quarter.

Forest said it will make significant investments in marketing and sales to launch the drug, including expanding its sales force.

Last month, Clinical Data reported a fiscal third-quarter loss of $5.2 million, or 17 cents per share, on revenue of $2 million. Forest, meanwhile, saw profits jump 53 percent in its latest quarter, as revenue rose 6 percent to $1.13 billion. Lexapro revenue amounted $586.5 million in the quarter.

In morning trading Tuesday, shares of Clinical Data slipped $3, or 8.8 percent, to $30.90.

Forest Laboratories shares fell $1.33, or 3.9 percent, to $33 as the broader markets declined.