The Risks and Benefits of Leqembi, the Newest Alzheimer's Drug, Explained

Leqembi binds to brain amyloids, abnormal proteins that are thought to play a role in Alzheimer’s. The drug prompts immune cells to essentially "chop up the amyloid and get rid of it," says Rudolph Tanzi, PhD, co-director of the Mass-General Institute for Neurodegenerative Disease at Massachusetts General Hospital and a professor of neurology at Harvard Medical School.

But the extent to which this actually mitigates Alzheimer’s symptoms remains unclear. What’s more, because amyloids accumulate in the brain decades before symptoms emerge, identifying and targeting these proteins earlier could be more effective, Tanzi says. That hypothesis is currently being tested.

Leqembi is approved for people with early Alzheimer’s. In clinical trials, it was tested on those in "the mildest of mild" stages of the disease, Tanzi says.

Because the trials stopped after 18 months, it’s unclear whether people who progressed to moderate Alzheimer’s would continue to benefit from the drug.

Those who took Leqembi in the clinical trial had 25 percent less cognitive decline. "It takes people who are declining at 60 miles an hour and slows them to declining at 45 miles an hour," Rind says. "You’re still declining, you’re just not declining as fast." ICER calculated that this would keep someone with Alzheimer’s out of long-term care for six more months.

Leqembi is "slowing an already slowly progressing condition," says Constantine Lyketsos, MD, an Alzheimer’s disease researcher at Johns Hopkins Medicine in Baltimore. "It’s probably not a perceptible slowing day to day."

For most people eligible, yes. Veterans Affairs indicated early on that it would be covered for veterans. And now with full approval from the FDA, Medicare will offer coverage of Leqembi as well. But Medicare patients taking Leqembi could still incur more than $5,000 in out-of-pocket costs each year. The Alzheimer’s Association has said that it expects other insurers to ensure access to Leqembi for those who are eligible but are not on Medicare.

Without insurance, Leqembi has an initial annual price of $26,500. Add fees for additional services such as MRIs, and the price could be "as high as $100,000 per year," Tanzi says.

Mild-to-moderate infusion-related reactions were the most common side effects. Brain swelling and bleeding were less frequent but still significant. While temporary and reversible in a vast majority of cases, three people who participated in the clinical trial died from hemorrhaging, according to Science magazine. Two of them were on blood thinners.

People on blood thinners should not take Leqembi, Tanzi advises. The FDA advises caution in such individuals as well.

"It’s recommended that you monitor [treatment] with MRIs," Rind says. Should brain swelling or bleeding occur, "you can either discontinue the drug or pause the drug while waiting for changes to reverse."

If you think you’d like to try Leqembi, start by talking with your Alzheimer’s disease specialist about its benefits and risks. Should you qualify and decide to move forward, he or she can incorporate the drug and monitoring it into your treatment plan.

Tanzi suggests tempering expectations. While the drug slows decline, its effect is probably too small to result in a perceptible difference from one day to another.