A drug lauded last year as a major breakthrough in the treatment and prevention of Alzheimer’s disease has come under a safety cloud following the deaths of three patients who received the drug.
Hailed as recently as November as “truly a historic moment for dementia research”, the drug lecanemab has been approved for use by the US Food and Drug Administration (FDA). But some critics have cast doubt over whether the potential gains to be made from the treatment are worth the risk.
One of those is Dr Diana Zuckerman, president of the National Center for Health Research, a non-profit organisation in Washington DC. “You’re dealing with people with mild cognitive impairment who are functioning, and you’re putting them at risk,” says Dr Zuckerman.
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Those potential risks are not just to a patient’s health, but also their hip pocket. According to lecanemab co-manufacturer, the Tokyo-based Eisai (along with Massachusetts-based Biogen), a year of treatment with the drug will cost US$26,000.
The potentially health risk appears to be grounded in the way lecanemab works. The drug is a monoclonal antibody given to patients via intravenous infusion. It enters the brain and, according to medical claims, clears the amyloid plaques believed to cause cognitive impairment and dementia in Alzheimer’s.
However, there are suspicions that the antibody weakened blood vessels in the brain of the patients who died as it attacked the amyloid plaques lining them. All three patients were taking anticoagulant drugs at the time, which may also have contributed to the bleeding.
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The set of conditions that may have resulted in the deaths is known as amyloid-related imaging abnormalities (ARIA). As a result, the FDA’s approval requires that lecanemab include a warning about ARIA, and that physicians monitor for the condition. The condition is usually neither serious nor life-threatening.
Eisai reported all three deaths as part of its trial reporting and says that the individual cases are not a basis for drawing any conclusions about lecanemab.
The cloud hanging over lecanemab has been further darkened by revelations that one of its predecessors, aducanumab, also manufactured by Eisai and Biogen, was approved for use by the FDA in 2021 despite its own scientific advisory panel voting 8–1 against its approval. After the FDA authorised its use, three advisory panel members resigned.
In the case of lecanemab, the FDA did not hold a public advisory meeting before approving it.
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Phase III trials of lecanemab, conducted last year, showed that cognitive decline was slowed by 27 per cent in those with early-stage Alzheimer’s over 18 months of treatment. But doubts remain over whether the slowing will continue beyond that period, or even what it will mean in practical terms for patients.
Eric Reiman, executive director of the Banner Alzheimer’s Institute in Phoenix, Arizona, says: “It could mean an extra six months of recognising a loved one’s face, or performing a valued activity.”
As it stands, the FDA’s recommendation is that lecanemab be used only by those with mild cognitive impairment, as it was for the clinical trials. The Australian government’s Therapeutic Goods Administration has not yet approved lecanemab for use in Australia.
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