Sage Therapeutics reviews Biogen's $7.22 per share acquisition proposal amid ongoing restructuring and focus on Zurzuvae for postpartum depression.

Sage Therapeutics reported that Biogen made an unsolicited offer to purchase all of the shares of the biopharmaceutical firm it doesn't already own.

Shares of Sage Therapeutics jumped nearly 40% in premarket trading Monday after the biopharmaceutical company received an unsolicited buyout bid from partner Biogen. Biogen, which already owns a roughly 10.2% stake in Sage, has proposed buying the rest of the company for $7.22 a share in cash in a deal that would value Sage at about $442 million.

BofA is moving to No Rating on Sage Therapeutics (SAGE) after the company announced it has received an unsolicited, nonbinding acquisition