Why did Biogen stock surge today? Alzheimer's drug data
Diego Thomazini         

Biogen (NASDAQ:BIIB) stock closedÂ up 40%Â Wednesday thanks to the release after Tuesday's closing bell of phase 3 data for its Alzheimer's disease candidate lecanemab.
The stock closed at $276.61. The last time it closed that high was Nov. 5, 2021 at $278.68.
The top-line data showed the candidate met its primary endpoint, reducing cognitive decline significantly better than placebo.
Results also showed improvements were seen as little as six months after treatment began and the treatment effect increased over 18 months.
The US FDA is set to decide on conditional approval for lecanemab by Jan. 6, 2023.