New data shows Alzheimer's drug can slow cognitive decline

Promising data shows that an Alzheimer's drug can slow cognitive decline.

In a phase III clinical trial, with results published Tuesday in the New England Journal of Medicine, the drug, Lecanemab -- developed by Eisai and Biogen Inc. -- slowed the rate of cognitive decline by 27% in patients in the early stages of the disease, making it the first drug of its kind to produce such positive trial results, the study showed.

"Lecanemab reduced markers of amyloid in early Alzheimer's disease and resulted in less decline than placebo on all measures of cognition and function at 18 months," said Dr. Christopher Van Dyck, director of the Yale Alzheimer's Disease Research Center, during his presentation of trial efficacy results at the Clinical Trials on Alzheimer's Disease meeting, held in San Francisco.

Researchers followed nearly 1,800 patients over the course of 18 months and found the drug "resulted in moderately less decline on measures of cognition and function," compared to patients who received a placebo.

However, the companies noted that "longer trials are warranted to determine the efficacy and safety of Lecanemab in early Alzheimer's disease."

Patients who have Alzheimer's disease have build-up of two proteins, amyloid-beta and tau, in the brain. They clump together and form plaques, disrupting cell function and causing symptoms such as memory loss and confusion.

Lecanemab is a monoclonal antibody that helps remove the amyloid-beta clumps.

Trial participants were split into two groups, both with a Clinical Dementia Rating Scale Sum of Boxes (CDR-SB) score of about 3.2 when the trial began. This score, which measures dementia impairment, has a scale from 0 indicating no impairment to 18.0 indicating severe impairment. A score of 3.2 indicates very mild impairment.

Over the course of 18 months, patients in the Lecanemab group saw their score go up by 1.21 points in comparison with patients in the placebo group, who saw their score go up by 1.66 points.

This is the "most exciting meeting we've had for clinical trials on Alzheimer's disease over the last 10 years. I think part of it is that finally we may have a medication that is showing efficacy in this primary outcome of this study," Dr. Babak Tousi, lead Investigator at the Cleveland Clinic study site and an associate professor of neurology and medicine at Lerner College of Medicine at Cleveland Clinic, told ABC News.

It will "not only be able to remove the amyloid plaques on the brain, we were able to show maybe the cognitive decline is less than what's expected without any treatment...So that's the part probably makes it exciting," he added.

There were some adverse events in the trial, the companies said, including about 20% of Lecanemab-treated patients who experienced brain swelling or brain bleeding, although side effects were largely asymptomatic.

Following the 18-month study, two patients died after experiencing brain hemorrhaging. However, Eisai said no deaths are considered linked to Lecanemab.

Dr. Marwan Sabbah, a neurologist at the Barrow Neurological Institute, said during the presentation Tuesday that doctors will need to proceed with caution when thinking about whether or not to recommend the drug for patients on blood thinners.

The Alzheimer's Association said it was "encouraged" by the news and called on the U.S. Food and Drug Administration to give accelerated approval of Lecanemab. The FDA is currently slated to make an approval decision by Jan. 6, 2023.

If approved, the drug would likely only be given to patients who are in the very early stages of the disease, not to people who already have significant cognitive impairment.

"These peer-reviewed, published results show Lecanemab will provide patients more time to participate in daily life and live independently," the Alzheimer's Association said in a statement. "It could mean many months more of recognizing their spouse, children and grandchildren."

The statement continued, "Treatments that deliver tangible benefits to those living with mild cognitive impairment (MCI) due to Alzheimer's and early Alzheimer's dementia are as valuable as treatments that extend the lives of those with other terminal diseases."

Researchers not involved in the study, including Dr. Leah Croll, a neurologist and assistant professor of neurology at the Lewis Katz School of Medicine at Temple University, said the results were promising.

"This is encouraging news for the millions of Americans affected by Alzheimer's disease, especially because the Alzheimer's drug pipeline has been met with many disappointments over the years," she told ABC News.

There have been hundreds of Alzheimer's drug trials over the years, most with disappointing results.

"Lecanemab is an important incremental change in the way we treat Alzheimer's," Croll said. "I'm hopeful that we are really starting to chip away at this disease process and that in the future, we will have even more options to offer patients."

If the drug gets FDA approval, cost could be a concern. For example, aducanumab, a controversial Alzheimer's drug that was approved last year despite critics arguing that trial data was conflicting, costs about $28,000 per year.