) --Japanese drug maker


has launched a $3.5 billion hostile tender offer for U.S. biotech firm

OSI Pharmaceuticals


, maker of the lung cancer drug Tarceva.

Astellas is seeking to acquire all outstanding shares of OSI Pharma for $52 a share, representing a 40% premium over OSI Pharma's Friday closing price of $37.02, Astellas announced Monday.

The hostile tender offer for OSI Pharma comes after numerous previous entreaties by Astellas to buy the U.S. drugmaker were spurned, Astellas said in a statement.

"This offer follows our attempts over the past 13 months to engage OSI in meaningful discussions. We firmly believe in the compelling strategic rationale behind the combination and the opportunity it provides to the OSI stockholders to realize full and fair value, in cash, immediately," said Masafumi Nogimori, president and CEO of Astellas, in a statement.

Sales of OSI Pharma's lung cancer drug Tarceva rose 17% to $1.2 billion in 2009. Tarceva is co-marketed by the Swiss drug giant



Last year, Astellas launched an unsuccessful and hostile tender offer for U.S. drugmaker

CV Therapeutics

, which was ultimately acquired by

Gilead Sciences

(GILD) - Get Report


-- Reported by Adam Feuerstein in Boston.

Follow Adam Feuerstein on



Adam Feuerstein writes regularly for In keeping with TSC's editorial policy, he doesn't own or short individual stocks, although he owns stock in He also doesn't invest in hedge funds or other private investment partnerships. Feuerstein appreciates your feedback;

click here

to send him an email.