(Reuters) -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.

Biogen (NASDAQ: BIIB ), which currently holds a 10.2% stake in Sage, proposed to acquire all outstanding Sage shares it does not already own for $7.22 per share.

Shares of Sage were up 5.3% at $7.48 in early trading.

Sage announced it has initiated a process to explore strategic alternatives but has not set a timeline for the review.

The company stated it will not provide updates unless necessary.

Sage shares plummeted 74.9% last year after discontinuing the development of its experimental drug dalzanemdor due to trial failures.

In October, the Massachusetts-based company announced the departure of Chief Financial Officer Kimi Iguchi and laid off over 165 employees as part of a reorganization to focus on the launch of its postpartum depression pill, Zurzuvae.

The U.S. Food and Drug Administration approved Zurzuvae, co-developed with Biogen, for postpartum depression in 2023.

Sage halted development of another neurological drug with Biogen in July.