An experimental new drug slowed the rate of cognitive decline among individuals in the early stages of Alzheimer’s in a large late-stage clinical trial, the pharmaceutical companies developing the drug announced last week.
The medication, called lecanemab, reduced cognitive decline by 27 percent compared to participants who received a placebo. The 18-month clinical trial, run by drugmakers Biogen and Eisai, included 1,795 individuals with mild Alzheimer's disease or mild cognitive impairment. Researchers evaluated the participants on a scale that measures cognitive decline, as well as their ability to perform routine tasks such as feeding or dressing themselves.
Scientists believe Alzheimer’s may develop as a result of a protein called amyloid, which clumps together and forms plaques in the brain. Lecanemab, like other anti-amyloid drugs, aims to clear the brain of those destructive plaques, theoretically helping to slow the progressive neurological disease.
The recent lecanemab trial is believed to be the largest test of whether clearing plaque from the brain can help slow Alzheimer’s. Some participants suffered from brain bleeding or brain swelling, which are common side effects of anti-amyloid drugs, but fewer people on lecanemab had these symptoms.
“These are the most encouraging results in clinical trials treating the underlying causes of Alzheimer’s to date,” the nonprofit Alzheimer’s Association said in a statement. “These results indicate lecanemab may give people more time at or near their full abilities to participate in daily life, remain independent and make future health care decisions.”
Alzheimer’s is the most common cause of dementia, the umbrella term for memory loss and cognitive decline; it accounts for 60 to 80 percent of dementia cases. Roughly 6 million Americans have Alzheimer’s disease, a number that’s expected to increase to 13 million by 2050, per the Alzheimer’s Association. Worldwide, more than 55 million people suffer from some form of dementia, including cases caused by Alzheimer’s.
There is no known cure for Alzheimer’s, and scientists are still trying to fully understand what causes it. Most existing treatments simply help patients manage, rather than heal, their symptoms.
Though lecanemab’s impact on cognitive decline was small—a reduction of 0.45 on an 18-point scale—some experts say it could provide much-needed relief for patients.
The Alzheimer’s Association said it “enthusiastically welcomes” the early results reported in this trial, adding that it looks forward to reviewing more detailed data in the future, per the statement.
Responses were similarly positive in the United Kingdom, where an estimated 850,000 individuals live with dementia, per the Alzheimer’s Society.
“Many people feel Alzheimer’s is an inevitable part of aging,” says Susan Kohlhaas, the director of research at Alzheimer’s Research UK, to the Guardian’s Hannah Devlin. “This spells it out: If you intervene early, you can make an impact on how people progress.
Still, not everyone believes the drug’s modest effect on cognitive decline will have a significant impact on patients, particularly those in the early stages of the disease.
The drug’s effect is “small and would not be considered by many as a minimally clinically important difference,” says Lon Schneider, who directs the California Alzheimer’s Disease Center at the University of Southern California and was not involved in the trial, to the New York Times’ Rebecca Robbins and Pam Belluck.
Japan-based Eisai, one of the drug’s developers, applied to the Food and Drug Administration (FDA) for accelerated approval, which allows the FDA to greenlight drugs that “treat serious conditions and that fill an unmet medical need,” per the agency.
The company expects an FDA decision by early January. After that, Eisai executives plan to use the new clinical trial data to seek full approval.
Eisai intends to publish findings from the trial in a peer-reviewed journal and will also present the results at a conference in November, reports Tom Murphy of the Associated Press.