"More than a century ago, Dr. Alois Alzheimer described the brain changes in a younger woman who had passed away from what we now call Alzheimer's disease," explains neurologist Dan Murman, MD. "The hallmark changes were amyloid plaques and neurofibrillary tangles. That's been the focus of Alzheimer's research ever since."
Amyloid is an aggregation of a protein called beta-amyloid that accumulates in the brain of older adults. It's one of the hallmark brain changes in Alzheimer's disease. Scientists don't know precisely what role amyloids play in Alzheimer's disease, but it appears that amyloids may be damaging or toxic to nerve cells.
Amyloid levels aren't a good indicator of the severity of memory loss or the stage of Alzheimer's disease. However, they seem to be an important marker of the start of the disease process. The buildup of amyloid begins about 15 years before people have memory loss. By the time significant memory loss occurs, the amount of amyloid in the brain is high but doesn't change much after that.
How anti-amyloid therapy works
Anti-amyloid treatments work by attaching to and removing beta-amyloid, a protein that accumulates into plaques, from the brain. Each drug works differently and targets beta-amyloid at a different stage of plaque formation.
The drugs haven't been shown to stop progression or to help people improve cognitive function. However, by removing the amyloid plaque, these drugs appear to slow down brain changes in the early stages of Alzheimer's disease and slow the rate of decline on tests of thinking and everyday function by approximately 30% to 40% in the 1½-year trials.
"It's possible that the benefit of anti-amyloid therapy may grow over time," says Dr. Murman. "Some studies suggest that it might keep people at these mild stages of the disease for one to two years longer. But we still need more information to prove that."
Currently approved treatments
Lecanemab (Leqembi™)
Lecanemab was approved by the FDA in July 2023. It is an anti-amyloid antibody for treatment of prodromal (the earliest stage) to mild Alzheimer's with confirmation of elevated beta-amyloid through an amyloid PET scan. Treatment consists of IV infusions every two weeks. A baseline MRI is required before starting treatment, followed by three safety MRIs within the first six months. Treatment typically continues for 2-3 years until a patient progresses to a moderate stage of dementia.