An Alzheimer’s Drug’s Big Surprise: What It Means

Until this past week, there seemed to be no answers to the Alzheimer’s puzzle. The leading theory of the disease, that it was caused by a buildup of beta amyloid plaque in the brain, had been disproved by the failure of earlier drugs. But, in a surprise on Tuesday evening, Biogen and partner Eisai released positive results from a new therapy they were testing, lecanemab.

This bombshell sent shares of


Biogen


up 35% and


Eisai


32% on the week. Eisai said the drug slowed cognitive decline in early-stage Alzheimer’s patients by 27% after 18 months, a better result than that achieved by Biogen’s approved, if controversial, Alzheimer’s drug, Aduhelm. “This appears to be basically a near-best-case scenario and should lead to full FDA approval,” Jefferies’ Michael Yee wrote; other analysts remained cautious.