15 Things to Know About the Two New Alzheimer’s Drugs

These drugs are so new, many doctors aren’t prepared with answers to patients’ questions

Marlene Cimons

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Ariel R. Green, M.D., Ph.D.

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En español

Published November 06, 2024

An illustration of the outline of a person's head connecting to an IV bag in the middle of it

Illustration by Rob Dobi

For the first time in history, doctors who care for people with Alzheimer’s have access to two medications that may be able to modestly slow the progression of the disease — at least for some patients.

The two drugs — Leqembi (lecanemab) and Kisunla (donanemab) — are “transformational,” says Paul E. Schulz, M.D., professor of neurology and director of the Neurocognitive Disorders Center at the McGovern Medical School at UTHealth Houston. “They provide the first inkling that we are on the right path, which gives us great hope that we can continue to tweak things and improve the effects.”

Someday, the drugs — or their next generation — might prevent cognitive decline entirely in people whose brains show signs of disease, but who don’t yet have symptoms, predicts Andrew Budson, M.D., chief of cognitive behavioral neurology, VA Boston and professor of neurology at Boston University. “These drugs are an absolute breakthrough for patients today, but even more so for patients tomorrow,” he says.

Yet even with the excitement and potential, there are serious considerations when it comes to these medications. Side effects can occur and can be serious — even deadly. What’s more, the drugs are expensive, with list prices higher than $25,000 a year.

It’s no wonder then that people who are newly diagnosed with Alzheimer’s may have questions. Those with certain risk factors are told, “talk to your doctor.” But do most doctors have answers?

“In my experience, most neurologists haven’t had a chance to learn about this area of treatment,” says Schulz, one of the researchers who studied Kisunla in clinical trials. “We’re all in the learning curve now.”

AARP interviewed six leading Alzheimer’s specialists to get answers to 15 questions about the new Alzheimer’s drugs.

Alzheimer’s disease is the most common form of dementia, afflicting an estimated 6.9 million Americans older than 65, according to 2020 data from the Centers for Disease Control and Prevention. The disease is marked by progressive memory loss, personality changes and ultimately the inability to perform routine daily tasks, such as bathing and dressing and paying bills.

1. How do these two drugs work?

Leqembi and Kisunla are antibodies that bind to the amyloid protein in Alzheimer’s plaques. Those plaques are formed from naturally occurring proteins that build up in the brain and cause problems. Most antibodies in the body are made by our immune system to fight off infections from viruses or bacteria, but these two are produced in the lab. When the antibody sticks to the amyloid molecule, the body’s immune system is alerted to destroy the amyloid, removing it from the brain and potentially slowing the disease.

2. How do the drugs differ from existing Alzheimer’s medications?

Other Alzheimer’s drugs help alleviate symptoms of Alzheimer’s like memory loss and confusion by altering brain chemicals. They are given as pills. These two drugs are given by intravenous infusion.

3. How do they differ from each other?

Leqembi binds to small molecules of amyloid called “amyloid protofibrils.” Kisunla binds to the amyloid plaques themselves. “Whether these different binding targets are critical is not clear,” Budson says. Leqembi is administered every two weeks for 18 months, then every 4 weeks after that, Budson says, adding, “There is no clear guidance on when to stop, if ever.” Kisunla is given every four weeks until the amyloid is cleared — as measured by a scan. If a PET scan shows minimal levels of amyloid, treatment is stopped.

4. What are the side effects? Are they serious?

There can be drug reactions that resemble flu-like symptoms, such as chills, shortness of breath and rash, generally mild and treatable with over-the-counter acetaminophen and antihistamines, such as Benadryl, says Jason Karlawish, M.D., professor of geriatrics at the University of Pennsylvania’s Perelman School of Medicine and codirector of the Penn Memory Center. More concerning, however, is when amyloid-related imaging abnormalities, known as ARIA, occur, which can include brain swelling or bleeding or both. “ARIA can be mild, moderate or severe,” Budson says. “When severe, it can be serious and life threatening.”

While patients taking Kisunla experienced more ARIA than those on Leqembi, the researchers point out that the two drugs were not compared to one another in the studies. Plus, “the donanemab [Kisunla] patients were further along [in the disease] cognitively and biologically, and so many of us believe that this is why donanemab had more ARIA,” Schulz says.

“I have many patients on each medication, and I feel confident that I am doing a service to my patients with each medication and I am not exposing one group to greater risks than the other,” Schulz adds.

Geriatrician Mia Yang, M.D., associate professor of internal medicine in the gerontology and geriatric medicine section at Wake Forest School of Medicine, prints an article from the Annals of Internal Medicine for her patients when discussing the new drugs, and points out that the drugs are risky for patients with medical conditions that make it likely they will experience a heart attack, ischemic stroke or a blood clot in the legs or lungs in the next 1-2 years. “The deaths that occurred during the trials were most commonly in patients who received additional blood thinner,” she wrote in an email.

5. Do the benefits outweigh the risks?

Schulz thinks so. “If it were me or my wife, I would definitely go on either one of them,” he says.” I don’t see a lot of differences between them in the real world. The risks can be very serious, but we are very scrupulous about monitoring for them.” Budson stresses that the decision is an individual one by patient and family members.

For Yang, the benefits outweigh the risks “only in those who have Alzheimer’s as their main problem,” and who are willing to take on the risk of intracranial bleed “and the burden of multiple MRIs, biweekly or monthly infusions, and who live within a reasonable driving distance to their infusion site/health system to get repeat MRIs that can accurately and timely capture ARIAs and associated symptoms,” such as headaches and dizziness, she wrote in an email.

Moreover, the “benefit is modest in cognition; both groups worsen over time,” she says. “The drug is very good at removing amyloid, but amyloid does not equal Alzheimer’s dementia or dementia in general.”

David Jones, M.D., a Mayo Clinic neurologist, who prescribes Leqembi for some of his patients, urges prudence. “I approach their use with a cautious attitude towards the risk/benefit equation,” he wrote in an email. “These drugs are certainly not the right choice for everyone, but they can be appropriate for some patients.”

6. Who are the best candidates for these drugs? What tests must I take before a physician will prescribe these drugs?

The drugs typically are recommended for those age 60 or older with Alzheimer’s disease as the primary cause of cognitive impairment. The diagnosis must be confirmed by lumbar puncture or amyloid PET scan, and blood tests to ensure nothing else is responsible for the symptoms, such as medication, for example, or a prior stroke.

Patients also should undergo cognitive testing, either the MoCA, for Montreal Cognitive Assessment, or the Mini-Mental State Examination, Budson says.

Yang typically prescribes the drugs to patients in their early 60s, who most likely have early onset Alzheimer’s disease but are otherwise healthy, but only after an extensive discussion of the risks and benefits.

If you think you are developing dementia — especially if your symptoms are mild — waste no time in getting evaluated, Schulz says, adding that starting one of these drugs as early as possible is very important. “As soon as you have an inkling of symptoms, get seen,” he says. “If it’s nothing, that’s OK. But the earliest you can catch it, the better.”

The drugs are most effective when the patient still can function normally, or has only minor difficulty with complicated tasks, such as paying bills and taking medications, Budson says.

7. Should certain people avoid these drugs?

Very important — potential patients should undergo genetic testing for the APOE e4 gene mutation. APOE e4 raises the risk of Alzheimer’s but also increases the possibility of ARIA. Patients with two copies of the gene, meaning one from each parent, should not take the drugs, Budson says. Those with only one copy must be carefully monitored if they take the drugs. “Patients with two copies of this gene have more side effects, and the medication does not seem to work as well,” says Alison O’Donnell, D.O. medical director for VA Pittsburgh Healthcare System’s Center for Cognitive Health.

Patients should not take the drugs if they have bleeding problems, or if they are on blood thinners other than aspirin. Also, they must be able to tolerate having MRIs, which are necessary to monitor for side effects.

8. Are there differences between the drugs that might make one more suitable for a person than the other?

Both remove amyloid from the brain, but they work at different stages of amyloid plaque formation. Leqembi is currently an IV infusion given every 2 weeks, while Kisunla is an IV infusion given every 4 weeks. “Less frequent infusions might make donanemab [Kisunla] more appealing to some patients,” O’Donnell says.

9. Once I am taking one of these drugs, what kind of monitoring is required?

You must undergo regular MRIs to ensure there are no side effects, especially microscopic brain bleeds or brain swelling associated with ARIA.

10. Will my insurance cover the testing? The drugs?

The drugs are quite expensive – but they are covered by Medicare, as is necessary testing. Other insurance coverage, including Medicare Advantage plans, may vary, depending on the plan, Schulz says.

11. What should I expect in the way of results if I take one of these drugs?

The research, which was conducted over 18 months, suggests “you get an additional six months of better quality of life for every 18 months, if you start early and keep using them,” Budson says. Schulz cautions, however, that it is still unclear how long these benefits will last. “We are still following those patients to give more guidance,” Schulz says. “As of this time, we don’t know whether we can say that we delay things 6 months for every 18 months. What we can say is that it is true for the first 18 months.”

12. Are there other options and what are their side effects?

There are no other FDA-approved treatments shown to slow cognitive decline in Alzheimer’s disease, though there are other drugs that deal with certain symptoms. These other treatments would be taken along with Leqembi or Kisunla, “so it isn’t an either/or situation,” Budson says.

13. Does efficacy wane over time, that is, do you have to take higher doses (like with Parkinson’s drugs) to get the same effects?

Unlikely. Data presented at the 2024 Alzheimer’s Association International Conference showed that patients on Leqembi continue to benefit compared with matched controls through at least 36 months of treatment, O’Donnell says.

14. Must the drugs be taken for life?

Opinions vary. At this time, Leqembi appears to need continuous treatment to maintain its benefits, O’Donnell says. Kisunla may be able to be stopped if amyloid levels decrease.

“The science isn’t 100 percent clear here, but for both drugs I believe a lot of us will see how individual patients do and make a decision as to whether to continue or stop the medications,” Schulz says, adding that so far, for Kisunla, “the data show no sudden decline as a result of stopping.”

15. What physicians are qualified to prescribe these therapies?

“If I was a patient, I would ask the physician: Do you think of yourself as an Alzheimer’s specialist?” Karlawish says. Usually, these are neurologists, geriatricians or psychiatrists who can make a diagnosis and who know how to prescribe and monitor these drugs. “Often they work at memory centers or an Alzheimer’s disease center,” he adds.

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Marlene Cimons is a Maryland-based writer and frequent Washington Post contributor who specializes in health, science and the environment.

Ariel Green, M.D., Ph.D., is a geriatrician and Associate Professor of Medicine at the Johns Hopkins University School of Medicine.