How the FDA-approved Alzheimer’s drug works and its possible side effects

Top line

The FDA granted accelerated approval to the Alzheimer’s drug lecanemab (brand name Leqembi) on Friday, but serious side effects and deaths during a clinical trial possibly linked to the drug have many in the health industry cautious in their optimism about the drug, which would treat a disease that has no known cure.


A report published in New England Journal of Medicine looked at a clinical trial for lecanemab and found that the drug effectively slowed cognitive decline for some participants with the disease.

The study also found that cognitive decline was 27% slower over an 18-month period in people who took lecanemab compared to those who did not.

Lecanemab is manufactured by the drug manufacturers Biogen and Eisai and is intended to be administered every two weeks intravenously.

Over 55 million people worldwide have dementia, and a majority (60%-80%) have Alzheimer’s disease, a progressive brain disease that slowly erodes memory and thinking skills.

There is no known cure for Alzheimer’s, but there are a few FDA-approved drugs that slow progression and relieve symptoms, such as aducanumab (which slows progression) and rivastigmine (which treats symptoms).

Patients may have to wait to receive the drug, as Medicare promised to cover any anti-amyloid drug with accelerated approval only in clinical trials after the controversial approval of Alzheimer’s drug Aduhelm in 2021.

The wholesale acquisition cost of a 200mg vial is $254.81, and the cost of a 500mg vial is $637.07, with the annual cost estimated at around $26,500 according to Eisai.

How Lecanemab works

According to Medical News Today, lecanemab is a monoclonal antibody: a laboratory-made antibody that is used to treat certain diseases such as cancer and Alzheimer’s and viruses such as Covid by acting like antibodies made by the body. When introduced into the body, monoclonal antibodies are used to fight infection, acting like the human immune system. Neurons play an important role in the way the brain works, helping in areas such as communication and regeneration. But in brains with Alzheimer’s, neurons stop working and communicating with each other, eventually leading to their death. As a result, plaque (buildup that forms when pieces of protein clump together) forms, which can be highly toxic to the brain, according to the National Institute on Aging. Lecanemab works by removing the plaque and slowing the progression of the disease. “Lecanemab has been reported to clear the amyloid plaques most robustly because it intervenes earlier in the pathological process that contributes to Alzheimer’s disease and with fewer side effects,” Dr. Karen D. Sullivan, a board-certified neuropsychologist, told Medical News Today.

Side effects

according to New England Journal of Medicine study, about 17% experienced brain bleeding, compared to 9% of those who did not take the drug. Almost 13% experienced brain swelling, while only 2% of those in the control group who did not take lecanemab experienced swelling. However, most of these incidents were not serious and subsided within months. But 3% of lecanemab patients experienced more severe brain swelling with symptoms such as confusion and visual disturbances. And 14% experienced serious side effects compared to the 11% who did not take lecanemab.

Possible death

A separate report published in New England Journal of Medicine on Wednesday detailed the death of a participant possibly linked to lecanemab. The participant – a 65-year-old with early stages of Alzheimer’s – was rushed to a hospital in Chicago when he or she showed signs of a stroke. The patient was treated with an intravenously administered clot-clearing drug tissue plasminogen activator (t-PA), which is standard practice in the treatment of stroke, but ultimately ended up dying. The combination of t-PA and lecanemab, researchers suspect, resulted in the patient’s death. “The extensive number and variation in sizes of the cerebral hemorrhages in this patient would be unusual,” researchers from the Northwestern University Feinberg School of Medicine in Chicago said in the report.

Critical quote

“Americans living with Alzheimer’s disease have the right to FDA-approved therapies, just like people with conditions such as cancer, heart disease and HIV/AIDS,” said Dr. Joanne Pike, president and CEO of the Alzheimer’s Association in a statement.

Further reading

Report shares new details on death possibly linked to experimental Alzheimer’s drug (CNN)

Lecanemab in early Alzheimer’s disease (New England Journal of Medicine)

FDA Approves Alzheimer’s Drug That Slowed Cognitive Decline in Clinical Trials (CNBC)

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