NEW YORK (AP) -- Dainippon Sumitomo Pharma Co. said Wednesday its tender offer for shares of drugmaker Sepracor Inc. was successful.

Dainippon agreed to buy Sepracor in September for about $2.6 billion, or $23 per Sepracor share. The first phase of the tender offer ended at midnight Tuesday, and a total of 86.9 million Sepracor shares were tendered in favor of the offer. That represents about 78.2 percent of Sepracor stock.

Dainippon started a follow-up tender offer to buy the rest of the Marlborough, Mass., company's shares. That offer will close on Monday. Sepracor stock added 3 cents to $22.98 in afternoon trading.

Sepracor makes drugs for respiratory and nervous system disorders. It reported $1.29 billion in revenue in 2008, with almost half of that total coming from sales of its sleep aid Lunesta.