Astellas Pharma has finally persuaded OSI Pharmaceuticals to sell up, having sweetened its original offer by some 10.6% or around $500 million.

The Japanese drugmaker has been pursuing OSI for over a year and in March launched a hostile $3.50 billion ($0.52 per share) takeover bid, an offer that was firmly rejected. The US firm did however open its books to Astellas and also contacted other potential purchasers but no other bids were forthcoming.

The Tokyo-headquartered firm had said it was not prepared to up its offer but has now changed its mind. It is now offering $57.50 per share in cash, a premium of 55% to the closing price for OSI’s shares on February 26, the last trading day before the company made its first move.

The latest offer, worth $4.00 billion, has been unanimously approved by both boards which means that Astellas should finally get its hands on OSI’s share of the profits from the lung and pancreatic cancer blockbuster Tarceva (erlotinib), co-marketed with Roche. OSI’s total revenues for 2009 were $428 million and operating income was $153 million.

Masafumi Nogimori, chief executive at Astellas, said that in addition to Tarceva, “we are pleased to add its oncology infrastructure, discovery platform, expanded pipelines and talent base to our existing businesses”. His counterpart at OSI, Colin Goddard, said the deal “recognises the significant value we have built for our stockholders while providing the merged companies the opportunity to forge a stronger
collective path forward”.

Astellas will be relieved that the OSI deal is drawing to a successfful conclusion as it represents a second attempt to expand in the USA - it failed last year with a hostile bid for CV Therapeutics, losing out to Gilead Sciences.