Willkie Farr & Gallagher and Paul Weiss Rifkind Wharton & Garrison have taken lead roles on the $2.6bn (£1.6bn) acquisition of US drugmaker Sepracor by Japan’s Dainippon Sumitomo Pharma (DSP).

The all-cash purchase price represents a premium of nearly $5 (£3) per share above Sepracor’s closing price on 1 September. Sepracor’s board has unanimously approved the deal, under which the company will continue operating as a wholly-owned subsidiary of DSP.