Expiration Date of OSI Offer Extended to May 17, 2010

Expiration Date of OSI Offer Extended to May 17, 2010

Tokyo, Japan - April 23, 2010 - Astellas Pharma Inc. (TSE: 4503) announced today that it has extended its all-cash tender offer for $52 per share for all of the currently outstanding shares of common stock (including the associated stock purchase rights) of OSI Pharmaceuticals, Inc. (Nasdaq: OSIP) to 5:00 p.m. New York City time on Monday, May 17, 2010, unless further extended. The tender offer was previously set to expire at 12:00 midnight New York City time on Friday, April 23, 2010.

As of 4:00 p.m. New York City time on Thursday, April 22 2010, 42,283 shares of OSI had been tendered in and not withdrawn from the tender offer. Citigroup is acting as exclusive financial advisor to Astellas and Morrison & Foerster LLP is acting as legal counsel.

Additional Information
Further details related to this proposal can be found on www.oncologyleader.com

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About Astellas
Astellas Pharma Inc., located in Tokyo, Japan, is a pharmaceutical company dedicated to
improving the health of people around the world through the provision of innovative and
reliable pharmaceuticals. Astellas has approximately 15,000 employees worldwide. The
organization is committed to becoming a global category leader in urology, immunology
& infectious diseases, neuroscience, DM complications & metabolic diseases and
oncology. For more information on Astellas Pharma Inc., please visit our website at