BOSTON/TOKYO: Dainippon Sumitomo Pharma Co Ltd agreed yesterday to buy US drugmaker Sepracor Inc for $2.6 billion, giving the Japanese firm a big, local sales force in the world's largest drugs market.

The deal is the latest in a string of overseas acquisitions by Japanese drugmakers keen to grow outside a mature home market and build product pipelines before key drug patents expire.

Dainippon, Japan's No 7 drugmaker by revenues, will gain a sales force of 1,200 familiar with central nervous disorders as it looks to promote its experimental schizophrenia drug lurasidone, which has performed well in late-stage trials.