EXPLANATION: New drug slows Alzheimer’s disease, but comes with caveats

WASHINGTON (AP) — A new Alzheimer’s drug has hit the market — for the first time, with clear evidence that it can slow the mind-robbing disease by months.

It’s a long-needed new treatment, but experts also voice caution: The drug isn’t a cure, it’s only for early-stage patients, requires IV doses every two weeks, and comes with some safety concerns.

It is not even clear how significant this modest benefit is will be in people’s daily life.

Still, “it’s remarkable,” he said. “It’s not enough, but it’s encouraging that there’s something we can do.”

Here are some things to know about Food and Drug Administration approval Lecanemab, which will be sold under the brand name Legembi:


The drug, made by Japan’s Eisai and its US partner Biogen, is designed to target and clear a sticky protein called beta-amyloid, one of the main symptoms of Alzheimer’s disease.

Alzheimer’s specialist Dr. at Mount Sinai Hospital in New York. Sam Gandy said it targets a slightly different form of that amyloid, which probably explains why it was successful in a rigorous study when a long list of drugs that target amyloid have failed.

The FDA cleared a similar drug called Aduhelm in 2021, even though studies never proved it actually helped patients, prompting sharp criticism from a congressional investigation..


In Eisai’s 18-month study of nearly 1,800 people, Legembi appeared to delay deterioration by about five months in early-stage patients.

It was measured using an 18-point scale that tracks cognitive and functional abilities. People who took the drug still got worse, but not as fast as the dummy versions — a difference of about half a point on the scale by the end of the study.

Experts differ on how meaningful this benefit is. Gandhi said it can be difficult for families to tell if a loved one’s decline is slowing.

Other experts say slowing down the disease in the early stages, when people are still doing well, is important, even if it’s not as easy to detect.

“A few months with better insight, what’s that worth to you?” Hodes asked. “I think you can make a strong argument there: If I can communicate with my family, if I can be independent for months … that’s a very meaningful outcome.”


Like other amyloid-targeting drugs, Legembi can cause brain swelling or small brain bleeds. In Eisai’s study, 13% of those taking the drug had swelling and 17% had small brain bleeds.

Possible cause: Amyloid plaques usually form around nerve cells in the brain, but sometimes they get into blood vessels. Gandy explained that removing amyloid from these blood vessels can weaken them and make them leaky.

While brain swelling and bleeding can cause minimal symptoms such as dizziness and vision problems, it can sometimes be severe — and several Legembi users have died while taking the drug, including two on blood thinners.

Eisai said the deaths could not be linked to the Alzheimer’s drug. But Gandy said the greatest risk of serious bleeding would be among Legembi users taking blood thinners used by older adults to prevent or treat strokes.

Patients may also experience temporary reactions after infusions, such as fever, flu-like chills, nausea, and changes in blood pressure.


The drug is only intended for people in the very early stages of Alzheimer’s disease, who have this tell-tale amyloid build-up.

The FDA has warned doctors to use caution if they prescribe Legembi to people using blood thinners. Patients will also be called for brain scans several times during treatment.

It’s not clear how long patients should continue receiving IV infusions twice a month as they get progressively worse. Study participants are being followed for longer periods of time, and other studies are investigating earlier use — before people with amyloid buildup show symptoms.


Eisai says the drug should be available by January 23, but most patients will likely have to wait months to get it.

That’s because health insurers are expected to scrutinize a drug’s effectiveness before deciding whether to cover it, for which patients, and what tests they can require to confirm they’re good candidates.

Medicare, which covers most Alzheimer’s patients, is not expected to pay for the drug until later this year. That’s because the seniors plan only pays for Alzheimer’s drugs that have received full FDA approval — the agency approved Legembi by taking a shortcut based on preliminary study results. The FDA is set to review the larger 18-month study soon, pending full approval later this year.


The IV drug will cost about $26,500 for a typical year’s treatment. Most people won’t pay that much if insurers cover it — though people with insurance who are required to shoulder a larger share of drug costs can pay thousands a year.


The Associated Press Department of Health and Science receives support from the Science and Education Media Group of the Howard Hughes Medical Institute. AP is responsible for all content.

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