The board of Redwood City, CA-based Facet Biotech (NASDAQ:[[ticker:FACT]]) unanimously recommended that shareholders reject the latest tender offer from Cambridge, MA-based Biogen Idec (NASDAQ:[[ticker:BIIB]]), saying that the $17.50 per-share offer, which would value Facet at about $438.7 million, was inadequate. Biogen called the bid, made a week ago, its “best-and-final offer.” Facet nonetheless says it is giving the Cambridge firm chance for due diligence discussions “to enable Biogen Idec to determine whether it will materially increase its offer to reflect the true value of our company and prospects.” Biogen began its takeover bid for Facet in September.