Astellas Pharma and OSI Pharmaceuticals have entered into a merger agreement under which Astellas will acquire OSI for approximately $4.0 billion in cash. Astellas first launched a takeover bid for OSI in March 2010, offering $3.5 billion.

The acquisition is part of Astellas’ strategy to become a global leader in oncology, a high-priority therapeutic area for Astellas. OSI focuses on the discovery, development and commercialization of molecular targeted therapies in oncology, diabetes and obesity. OSI also commercializes the leading cancer drug Tarceva (erlotinib). OSI’s total revenues for 2009 were $428 million and operating income was $153 million.

Masafumi Nogimori, president and chief executive officer of Astellas, said, “The merger with OSI provides Astellas with a top-tier oncology platform in the U.S. and an expanded product portfolio and pipelines. In addition to Tarceva, we are pleased to add its oncology infrastructure, discovery platform, expanded pipelines and talent base to our existing businesses.”

Colin Goddard, Ph.D., chief executive officer of OSI Pharmaceuticals, said, “We believe today’s announcement recognizes the significant value we have built for our stockholders while providing the merged companies the opportunity to forge a stronger collective path forward in a shared mission to provide innovative new medicines to patients around the world.”