This week the U.S. Food and Drug Administration approved the drug lecanemab after research showed it slowed the progression of Alzheimer’s disease in some patients with mild cognitive impairment.

This is undoubtedly a breakthrough for treatment of an irreversible, progressive brain disorder affecting more than 6.5 million Americans. While the drug was granted so-called accelerated approval in January, full FDA approval means wider coverage by Medicare so it can better reach patients.

Named Leqembi, lecanemab’s approval has triggered less controversy than a related drug called Aduhelm, or aducanumab, because its clinical trial results are more definitive.

With help from Stanford and UC San Francisco experts, we answer questions about the new drug.

Q: What is lecanemab?

A: It’s a drug that is designed to remove amyloid beta, a sticky plaque that builds up in the brain in people with Alzheimer’s disease, causing disease progression. It is the first anti-amyloid treatment to earn full approval by the FDA.

The drug, developed by the Japanese pharmaceutical company Eisai and sold in partnership with Biogen, is priced around $26,500 annually per patient.

Q: Does the drug cure Alzheimer’s?

A: No. Patients continued to experience decline in cognition and independence. But lecanemab causes a modest reduction in the progression of the earliest stages of the disease, slowing the rate of cognitive decline by 27% compared with a placebo in an 18-month study of 1,800 patients with early Alzheimer’s disease. This translated to a roughly 6-month delay in symptom progression, giving patients more meaningful time with their friends and families.

Q: Who is eligible for lecanemab?

A: This drug will only be prescribed for patients who are in the early stages of Alzheimer’s disease with a diagnosis of mild cognitive impairment or mild dementia.

Patients with moderate or severe dementia or other diagnoses are not eligible, because there is no safety or effectiveness data on its use in people with more advanced disease.

It is not recommended for patients with a history of stroke or seizures, bleeding disorders or treatment with blood thinners, immune conditions or treatment with immunosuppressants, other serious conditions such as cancer, MRI abnormalities with evidence of a tumor or hemorrhage or hypersensitivity to monoclonal antibody treatment.

Q: What is needed to get treatment?

A: Before starting lecanemab, your doctor will need to confirm the presence of amyloid in your brain. This requires either an amyloid PET scan or spinal tap. Because patients who have a specific genetic variation called ApoE4 are also at higher risk of side effects, genetic testing prior to receiving treatment is required.

At Stanford Health Care, neurologists will consider treatment for patients who are: ages 50 to 90 years, able to undergo frequent MRI scans and have PET scans or cerebrospinal fluid to confirm the presence of brain amyloid. Patients must be willing to undergo ApoE4 genotype testing. It is also recommended that they have have a care partner or someone else to support their frequent visits.

Q: How is lecanemab administered?

A: Lecanemab is given intravenously — infused through a vein — every two weeks.

Q: Where will treatment be offered?

A: Because neurologists and special equipment are needed to evaluate patients and administer the drug, its use will be limited to large academic hospitals and specialty clinics.

Q: What are some potential risks of lecanemab?

A: The drug is known to cause brain swelling or bleeding, called amyloid related imaging abnormality (ARIA) in about 20% of patients. While most patients with ARIA show no symptoms, some may experience headache, visual changes, and confusion. The majority — seven to eight of 10 cases — of ARIA resolve within three to four months. While severe symptoms and complications occur in fewer than 1 in 100 patients with ARIA, at least three people have died of serious brain bleeds after taking the drug.

The drug can also cause infusion-related reactions in about 20% of patients. Most of these reactions occurred with the first treatment. These symptoms may include changes in blood pressure, changes in breathing, skin changes, fevers, and chills. The majority of infusion reactions caused by lecanemab have been easily treatable.

Q: Is lecanemab covered by Medicare or other insurance?

A: To be covered by Medicare, a patient must be diagnosed with mild cognitive impairment or mild dementia due to Alzheimer’s disease and participate in a registry.

Amyloid PET scans are not currently covered by insurance. Coverage for other required tests – such as MRI scans, blood tests or cerebrospinal fluid analysis — is not yet certain.

The availability of private insurance coverage is not yet known.

Q: How does lecanemab differ from aducanumab, or Aduhelm, which won the FDA’s accelerated approval in June 2021?

A: The two drugs act through a similar mechanism. But Aduhelm targets a different version of amyloid and may be less effective at removing the plaque. Two large trials of Aduhelm in people with early symptomatic Alzheimer’s disease were discontinued prematurely, and one trial did not show a benefit in symptoms. Because of conflicting results on whether it slowed cognitive decline, Aduhelm is not covered by most insurers.

For more information:

UCSF’s Memory and Aging Center: https://memory.ucsf.edu/lecanemabStanford Health Care Center for Memory Disorders: https://stanfordhealthcare.org/campaigns/lecanemab.html