The FDA Has Just Given Rare Approval to a New Alzheimer's Drug, Leqembi—Here's What We Know So Far

As a neurological diagnosis, Alzheimer’s is bad news. The degenerative illness affects memory, recognition, and cognitive functioning, with dementia being the best-known symptom. More than 6 million Americans live with Alzheimer’s, which has no cure and few treatments.

Leqembi, a new drug purported to slow progression of cognitive impairment, has gotten full FDA approval. But, as The New York Times reports, some health care experts are concerned that the risks outweigh the benefits. Here’s what we know so far.

What Is Leqembi and how does it work?

Leqembi is a monoclonal drug developed by Japanese pharmaceutical company Eisai and marketed by Biogen. The drug targets and clears out the amyloid beta proteins in the brain that create amyloid plaque, a hallmark of the disease. About 1.5 million people in the U.S. with early-stage Alzheimer's disease could be eligible (Leqembi is not recommended for those with moderate to severe Alzheimer's).

In a clinical trial of people with mild cognitive impairment, Leqembi slowed cognitive decline in those taking the drug compared to those who received a placebo—roughly a 27 percent reduction in the rate of disease progression over an 18-month period. Subjects on Leqembi scored roughly a half-point better on an 18-point cognitive test than those who were not taking the drug.

What will Leqembi do for patients on a day-to-day basis?

It’s possible Leqembi will allow for those with Alzheimer’s to stave off cognitive impairment for a longer period of time (five months over the 18-month term of treatment) than those not taking the drug. Someone might retain memory of a phone number or name for longer, for example. But for others, the difference may not be that noticeable.

Who can take Leqembi?

Leqembi is intended for individuals with mild symptoms and in the beginning stages of Alzheimer’s who have been tested for elevated amyloid protein. Its effect on those with moderate to advanced Alzheimer’s has not yet been evaluated. Eisai recommends patients stop taking Leqembi once they progress to a moderate stage of the disease.

How is Leqembi administered?

Leqembi is not an oral medication. It’s an intravenous drug administered through IV injection twice a month.

Is Leqembi a cure for Alzheimer’s?

No, Leqembi cannot cure Alzheimer’s. It is a treatment intended for those in the early stages of the disease.

Is Leqembi approved by the FDA?

Yes. Leqembi was first approved by the Food and Drug Administration in January 2023 under its Accelerated Approval program, which permits the use of a drug for a serious condition if a benefit is likely but as yet unproven. The FDA then mandates a clinical trial to confirm that benefit. Leqembi was given full FDA approval in July 2023.

What are the side effects of Leqembi?

While a new treatment for Alzheimer’s is cause for enthusiasm, there are some very significant risks associated with the drug. The most concerning is the potential for brain swelling or brain bleeds in patients, which may or may not be symptomatic. Roughly 13 percent of trial participants experienced brain swelling; 17 percent experienced brain bleeds. These symptoms were also observed in participants taking the placebo, though at lower rates: 2 percent for swelling, and 9 percent for bleeding. The risk was higher among patients taking anticoagulant medications or those with the APOE4 gene mutation. Between 15 and 25 percent of people in the U.S. carry the mutation.

The FDA has included a notice with the drug that warns of these potentially fatal side effects. In their statement announcing approval of Leqembi, the agency added that:

“The most common side effects of Leqembi were headache, infusion-related reactions, and amyloid-related imaging abnormalities (ARIA), a side effect known to occur with the class of antibodies targeting amyloid. ARIA most commonly presents as temporary swelling in areas of the brain seen on imaging studies that usually resolves over time and may be accompanied by small spots of bleeding in or on the surface of the brain. Although ARIA is often not associated with any symptoms, symptoms can occur and include headache, confusion, dizziness, vision changes and nausea. ARIA can also infrequently present with serious and life-threatening brain edema that can be associated with seizures and other severe neurological symptoms. Intracerebral hemorrhages can occur in patients treated with this class of medications and can be fatal.”

How much does Leqembi cost?

Leqembi is an expensive drug. A year’s worth of treatment is $26,500, though Medicare will cover about 80 percent of the cost for eligible patients. Patients will be responsible for the remaining 20 percent.

What do experts think about Leqembi?

There is ongoing dialogue about the risk vs. reward benefit of Leqembi. Speaking with The New York Times, Dr. Jason Karalawish, co-director of the University of Pennsylvania’s Penn Memory Center, said that the side effects could potentially cause disability if not detected in time. “In contrast,” he said, “the benefits of slowing are subtle. You’re not going to experience the perception of changes in your cognition or function in the same amount of time.”

The Alzheimer’s Association, an advocacy group for those with the disease and their caregivers, praised the FDA’s decision in a press release. “This treatment, while not a cure, gives people in the early stages of Alzheimer’s disease more time to maintain their independence and do the things they love,” Dr. Joanne Pike, its CEO and president, said in a statement. “While we continue efforts to discover new targets and test new treatments, people living with this fatal disease deserve the opportunity to discuss and make the choice with their doctor if an FDA-approved treatment is right for them.”

Wasn't another drug recently approved for Alzheimer's?

Yes. In 2021, the FDA approved Aduhelm, another intravenous drug that reduced beta amyloid in the brain, under its Accelerated Approval program. That drug was marred with controversy, as its potential benefits were unclear. The FDA was later scrutinized via a congressional investigation for its conditional approval of the drug. Biogen markets both Adulhelm and Leqembi.

Should I take Leqembi?

Treatment for Alzheimer’s is highly individualized. Anyone considering Leqembi should discuss the benefits and risks with their health care provider, who can help patients make an informed decision.