Jan 27 (Reuters) - Sage Therapeutics ( SAGE ) said on

Monday that its board has unanimously rejected the takeover

offer it received from Biogen.

The company said Biogen's offer to buy all outstanding

shares of Sage that it does not already own for $7.22 apiece,

"significantly undervalues Sage and believes it is not in the

best interest of shareholders."

Biogen has a 10.2% stake in Sage Therapeutics ( SAGE ).

Sage said it has initiated a process to explore

strategic alternatives, but has not set a timetable for the

review process.