PALO ALTO, Calif. (AP) — CV Therapeutics Inc. said Wednesday it is reviewing a buyout offer from partner Astellas Pharma Inc., which it had initially rejected. CV Therapeutics turned down the $1 billion bid in November. CV Therapeutics said it decided that offer was not in the best interest of the company or its shareholders, but after Astellas made the bid public Tuesday, CV said it will consider it again in light of changes in the market and its own business. The offer values CV shares at $16. The stock closed at $11.35 Monday, before the offer was made public, and jumped to $15.42 in Tuesday trading. As part of the review, CV Therapeutics said it extended the expiration date of its shareholder rights plan by one year, to Feb. 1, 2010. Tokyo-based Astellas owns the U.S. rights to CV Therapeutics’ drug Lexiscan, which is used in patients who cannot exercise sufficiently for a coronary stress test. In a note published Tuesday, Citi Investment Research analyst Yaron Werber said Astellas is looking to gain full worldwide rights to Lexiscan. “Astellas is likely interested in acquiring CVT since it is a perfect complement to its existing cardiology and in-hospital sales infrastructure,” he wrote.