Leqembi and Alzheimer’s: What to Know About the New Drug, Treatment and Benefits

Over the last three years, a new class of Alzheimer’s drug, the first to treat a root cause of the disease, has set off a roller coaster of hope and disappointment. But while these so-called anti-amyloid antibodies had a rough start, many patients and their doctors are feeling more optimistic now that one of the medications is finally being used more widely.

Lecanemab (brand name Leqembi; pronounced le-KEM-bee) was given full approval by the Food and Drug Administration in July 2023 and is currently the only one of its class available to Alzheimer’s patients, outside clinical trials. The drug has been shown to slow the progression of the disease, but its benefits are fairly modest. It is also a burdensome therapy and has a high risk of troubling side effects.

With lecanemab having been approved for nearly a year — and with a similar drug, donanemab, recommended for approval by an F.D.A. advisory committee at a meeting on Monday — The New York Times checked in with experts at three major medical centers about who’s receiving lecanemab and how they’re responding.

Who’s being prescribed lecanemab?

There are strict requirements for patients to be eligible for lecanemab; by one estimate, fewer than 20 percent met the qualifications for the medication. Neurologists at the Mayo Clinic, Massachusetts General Hospital and the University of California, San Francisco, all described a similar review process when deciding which patients are good candidates.

First, the patient must be diagnosed with mild cognitive impairment or mild dementia, the earliest two stages of Alzheimer’s disease. Second, because lecanemab works by removing the amyloid plaques that are a hallmark of the disease, patients undergo a PET scan or a lumbar puncture to make sure plaques are actually present in the brain. Third, the patient needs an M.R.I. to screen for signs of other brain diseases.

“We want to make sure that they don’t have another explanation for their cognitive problems,” said Dr. Ronald Petersen, the director of the Mayo Clinic Alzheimer’s Disease Research Center.

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