* Shareholders reject Biogen tender offer
* Facet says open to other, better offers
* Facets shares rise 2.38 percent; Biogen off 2 percent
BOSTON, Dec. 17 (Reuters) - Biotechnology company Biogen Idec Inc (BIIB.O) has terminated its bid to acquire Facet Biotech Corp FACT.O after Facet shareholders rejected the offer of $17.50 a share.
Facet said it has asked its financial adviser, Centerview Partners, to solicit additional parties that may have an interest in a transaction.
Facet said Biogen still has an the opportunity to make a "materially increased offer."
Biogen's tender offer expired at midnight on Wednesday.
The companies are jointly developing an experimental drug to treat multiple sclerosis, daclizumab, and a treatment for solid tumors, voliciximab.
Facet shares rose 2.4 percent to $16.79 in early trading on Nasdaq. Biogen was down 2 percent at $49.25.
On Wednesday, Facet received a big boost when The Baupost Group, a hedge fund run Seth Klarman, said it would not tender its shares to Biogen. Klarman is the author of "Margin of Safety: Risk-Averse Value Investing Strategies for the Thoughtful Investor," a book that is hard to find but has a cult following among value investors.
Baupost holds a 14 percent stake in Facet. It said it did not believe Biogen's offer adequately reflected Facet's value. (Reporting by Toni Clarke; editing by John Wallace)