Sage Therapeutics 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.

Sage Therapeutics has rejected the unsolicited acquisition offer it received earlier this month from longtime partner Biogen Inc.

Following a lawsuit filed last week, Sage has officially rejected Biogen’s unsolicited buyout offer, which valued the embattled biotech at just $469 million.

Sage Therapeutics has brought a lawsuit against Biogen shortly after receiving an “unsolicited” offer from its neuroscience partner. | Sage Therapeutics has brought a lawsuit seeking a temporary restraining order against Biogen shortly after receiving an "unsolicited" offer from its neuroscience partner.

Biogen’s effort to buy Sage reveals its “desire to expand its pipeline at a discount,” according to analysts from BMO Capital Markets.

Sage Therapeutics said on Monday that its board has unanimously rejected Biogen’s $469 million offer, stating it "significantly undervalues" the company and does not serve shareholders' best interests.

Sage Therapeutics rejected a takeover offer from Biogen and said it started a process to review its strategic alternatives. Sage rose 5.6%. Sage's board will look at