Will unpredictable side effects dim the promise of new Alzheimer’s drugs?


Despite landmark antibody approval, research into potentially serious brain swelling and bleeding still lags.

A sea change is underway in the treatment of Alzheimer’s disease, where for the first time a drug that targets the disease’s pathology and clearly slows cognitive decline has hit the U.S. market. A related therapy will likely be approved in the coming months. As many neurologists, patients, and brain scientists celebrate, they’re also nervously eyeing complications from treatment: brain swelling and bleeding, which in clinical trials affected up to about one-third of patients and ranged from asymptomatic to fatal.

The side effect—amyloid-related imaging abnormalities, or ARIA—remains mysterious. “We don’t really understand what it is, what causes it, and what we can do about it,” says neurologist R. Scott Turner, director of the Memory Disorders Program at Georgetown University.