Biogen Stock (BIIB) After-Hours on Dec. 19, 2025: Why Shares Jumped, Where They Closed After the Bell, and What to Watch Before the Next Market Open
Biogen Inc. (NASDAQ: BIIB) finished Friday, December 19, 2025 with a strong gain and unusually heavy trading volume, then edged higher in extended trading—capping a session dominated by fresh analyst commentary and renewed attention on the company’s Alzheimer’s and pipeline