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

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 announced its boards unanimous rejection of Biogens $469 million acquisition offer, stating the proposal significantly undervalues the company and does not align with shareholder interests.