Biogen (BIIB.US) plans to acquire Sage (SAGE.US) shares at a 30% premium.

Biogen (BIIB.US) announced on Friday that it would buy the outstanding shares of Sage Therapeutics (SAGE.US) for $7.22 per share, driving Sage's stock up 34% in after-hours trading.

Regulatory filings show that Biogen owns 10.2% of Sage Therapeutics. The offer is 30% above Sage's closing price on Friday and values Sage at $441.7 million.

Biogen's Alzheimer's drug Leqembi has been slow to recover in the U.S. due to concerns about cost, efficacy and side effects.

Sage's stock has plunged 75% in 2024. The company abandoned its drug dalzanemdor after multiple trial failures. Sage said in November that it would focus on Zurzuvae, a postpartum depression drug being developed with Biogen.

Sage also abandoned another neurological disease drug being developed with Biogen in July.