TOKYO (AFP) -– Japan's second-largest drugs maker by sales Astellas said Monday it will buy U.S. firm OSI Pharmaceuticals for four billion dollars after raising its bid during a two-month-long takeover attempt.

Astellas lifted its offering price to 57.50 dollars per share, up from an initial offer of 52 dollars. The new offer is 55 percent higher than OSI's price on February 26 when the bid was first announced, it said.
In a statement the Japanese firm said the all-cash acquisition was fully approved by the boards of both Astellas and OSI.
The Japanese company said the deal would propel it to become a global leader in oncology, but the drug-maker's shares fell 1.74 percent in Tokyo trade after the announcement on concerns the purchase was expensive.
The agreement between the Tokyo-based drug maker and the U.S. developer of Tarceva cancer drug comes two months after Astellas launched a hostile takeover bid for the company in March.
Astellas is looking to offset a profit decline as rival generic drugs enter the market.
A rival generic version of Astellas' immune system drug Prograf came to the market in August last year, while generic competitors for its urinary disorder treatment Flomax were launched in March.
Dow Jones Newswires contributed to this story.