alzheimers disease brain sanjay gupta orig _00002128.png
How Alzheimer's disease destroys the brain
01:38 - Source: CNN
CNN  — 

A monoclonal antibody treatment for Alzheimer’s disease called lecanemab slows the progression of cognitive decline by 27% compared with a placebo, drugmakers Biogen and Eisai said Tuesday.

The drug, tested in a Phase 3 global clinical trial, also met all secondary endpoints, showing “target engagement” with reduced amyloid levels – a protein that is one of the hallmarks of Alzheimer’s – and positive effects on cognition and the ability to perform everyday tasks when compared with a placebo.

“We believe that helping to alleviate these burdens will positively impact society as a whole,” Eisai CEO Haruo Naito said in a statement. “Additionally, the lecanemab Clarity AD study results prove the amyloid hypothesis, in which the abnormal accumulation of Aβ in the brain is one of the main causes of Alzheimer’s disease.”

However, Dr. Richard Isaacson, director of the Alzheimer’s Prevention Clinic in the Center for Brain Health at Florida Atlantic University’s Schmidt College of Medicine, told CNN that the trial results are not proof of the amyloid hypothesis.

“It proves that, in people with a certain amount of amyloid in their brain at a certain stage of the disease, that this drug works. In terms of proving a mechanism by using a drug, no. Alzheimer’s is a very heterogeneous disease.”

But he says that does not diminish the potential significance of the trial.

“In the past, reducing amyloid in the brain has not always been tied to cognitive improvements or any meaningful clinical improvements. In this study, every endpoint was positive. That’s never happened before.”

About 2.8% of trial participants who took the drug had a symptomatic side effect called ARIA-E, swelling in the brain, but none of those taking the placebo did. The rate of symptomatic ARIA-H, brain bleeding and iron buildup in tissue, was 0.7% in the drug group and 0.2% in the placebo group.

Overall, there were ARIA side effects in 21.3% of the trial participants taking lecanemab, but Isaacson cautions that when people receive this type of treatment, they need to be monitored closely throughout the process. Symptomatic side effects are a more important measure, he says.

“When this drug is used correctly, the side effects are manageable, and the negative outcomes are preventable in most cases,” he said.