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An experimental drug appears to slow memory loss in people with early Alzheimer's

MARY LOUISE KELLY, HOST:

In a large new study, an experimental Alzheimer's drug appeared to slow down the deadly disease. But as NPR's Jon Hamilton reports, the drug is not a cure and it carries some risks.

JON HAMILTON, BYLINE: The study's results were presented Tuesday at the Clinical Trials on Alzheimer's Disease meeting in San Francisco. They were also published online in The New England Journal of Medicine. During the meeting's opening session, Dr. Christopher Van Dyck of Yale University described the effects of the drug lecanemab in people with early Alzheimer's.

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CHRISTOPHER VAN DYCK: Lecanemab reduced clinical decline by 27%.

HAMILTON: The study included nearly 1,800 people. Half got the drug. Half got a placebo. Van Dyke, the lead author, noted that even people who got the drug experienced declines in memory and thinking.

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VAN DYCK: In the placebo group, people declined by 1.66 points over the course of 18 months. The actively treated group declines by 1.21.

HAMILTON: A difference of less than half a point on a dementia scale that runs from 0 to 18. Dr. Madhav Thambisetty, a neurologist who was not involved in the study, says that's not much.

MADHAV THAMBISETTY: It's a very small effect. And from my perspective as a physician caring for Alzheimer's patients, it's very unlikely that these differences are going to be noticeable by individual patients in their everyday lives.

HAMILTON: Thambisetty is a senior investigator at the National Institutes of Health, though his views on the drug are purely his own. Thambisetty is concerned that lecanemab's modest benefit may not outweigh its risks.

THAMBISETTY: This drug, like other drugs in the same class, is not a benign drug. It's associated with side effects.

HAMILTON: Like swelling and bleeding in the brain. At the meeting, though, Dr. Marwan Sabbagh of the Barrow Alzheimer's Institute (ph) downplayed those side effects.

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MARWAN SABBAGH: I know there's been a lot of discussion, a lot of buzz, a lot of energy around safety-related issues.

HAMILTON: Lecanemab removes a substance called amyloid from the brain. This removal process can cause excess fluid or small hemorrhages. And on an MRI scan, that shows up as something called ARIA or amyloid-related imaging abnormalities. About 20% of people who got lecanemab had ARIA. But Sabbagh says that's not cause for alarm.

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SABBAGH: The overwhelming majority of the ARIA events were mild or moderate.

HAMILTON: Sabbagh says the abnormalities usually disappeared after a few treatments and often went unnoticed by patients.

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SABBAGH: They were symptomatic less than 3% of the time, and it would include headache, visual disturbance and some confusion.

HAMILTON: The risks are acceptable to Mike Zuendel. He's 68 and works as an investment advisor in Telluride, Colo. He's also been diagnosed with mild cognitive impairment, an early stage of Alzheimer's.

MIKE ZUENDEL: I am a person living with a progressive and fatal disease. I do not have time to wait for the perfect research study.

HAMILTON: Zuendel is currently taking a different amyloid drug called Aduhelm. It was approved in 2021 despite conflicting evidence about whether it helps patients. Zuendel says he thinks Aduhelm is keeping his memory and thinking problems from getting worse. But he says lecanemab may prove to be a better option.

ZUENDEL: The results are extremely positive and, in my mind, has passed all safety requirements. And I'm extremely hopeful that the FDA will approve it.

HAMILTON: The Food and Drug Administration is expected to make a decision on lecanemab early next year.

Jon Hamilton, NPR News. Transcript provided by NPR, Copyright NPR.

Jon Hamilton is a correspondent for NPR's Science Desk. Currently he focuses on neuroscience and health risks.