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Some experts question how effective lecanemab will be for people with Alzheimer’s disease. Manu Padilla/Stocksy United
  • A potential new Alzheimer’s drug, lecanemab, showed promise in slowing cognitive decline in a recent phase 3 clinical trial
  • Officials at an Alzheimer’s organization called the trial results “modest” but said they are nonetheless encouraging.
  • Some experts have said lecanemab may simply reduce symptoms and not improve brain function.

A potential new drug to treat Alzheimer’s disease showed promise in a recent clinical trial, although not all experts are convinced the medication is an effective treatment.

Researchers said the drug, lecanemab, slowed cognitive and functional decline by 27% when given to people with Alzheimer’s in a phase 3 clinical trial.

The study results were published in late November in the New Journal of Medicine.

The trial was conducted at 235 sites in North America, Asia, and Europe between March 2019 and March 2021. The study involved nearly 1,800 adults ages 50 to 90. All the participants had some form of early dementia or Alzheimer’s disease. Half of the participants were given lecanemab and the other half were given a placebo.

Researchers reported there wasn’t a significant difference between lecanemab and the placebo at 12 months, but at 18 months it appeared the people taking lecanemab had some clearance of amyloid and less cognitive decline.

However, researchers said participants taking lecanemab had a higher percentage of adverse events than people taking the placebo at both 12 months and 18 months.

Nonetheless, officials at Biogen and Eisai, the developers of lecanemab, said the latest clinical trial provides hope for the Alzheimer’s community.

“Today’s announcement gives patients and their families hope that lecanemab, if approved, can potentially slow the progression of Alzheimer’s disease and provide a clinically meaningful impact on cognition and function,” said Michel Vounatsos, the chief executive officer at Biogen, in a statement. “Importantly, the study shows that removal of aggregated amyloid beta in the brain is associated with a slowing of disease in patients at the early stage of the disease.”

In a statement in late September, officials at the Alzheimer’s Discovery Drug Foundation (ADDF) said the findings at that point showed “modest effectiveness,” but they were still encouraged by the news.

“The combination of the biomarker change – reduced amyloid – plus slowing of cognitive decline in this study is encouraging news for the 57 million patients around the world living with Alzheimer’s,” said Dr. Howard Fillit, the co-founder and chief science officer at the ADDF. “However, amyloid-clearing drugs will provide an incremental benefit at best and there is still a pressing need for the next generation of drugs focused on other targets based on our knowledge of the biology of aging. We are optimistic about the future as many of these drugs are in development, with 75% of drugs in the pipeline now targeting non-amyloid pathways of neurodegeneration.”

Lecanemab is used to treat early Alzheimer’s disease. In earlier clinical trials, it was shown to lower levels of beta-amyloid plaque, a biomarker of the disease found in the brain.

“Lecanemab… is a monoclonal antibody infusion therapy that targets components of beta-amyloid, which build up… as part of the plaques and tangles that are characteristic of Alzheimer’s disease. And these new therapies effectively clear those amyloid plaques. It’s an exciting new chapter in the treatment of Alzheimer’s disease,” said Dr. Scott A. Kaiser, a geriatrician and the director of geriatric cognitive health for the Pacific Neuroscience Institute at Providence Saint John’s Health Center in Santa Monica, California.

“We know that it clears the beta-amyloid plaque,” Kaiser told Healthline in September. “The question is whether or not that actually helps with brain function. But the idea is that these plaques are interfering with the effective communication and overall interaction between brain cells and that clearing them could have positive effects.”

The Food and Drug Administration is expected to vote in late January on whether to approve lecanemab for general use.

It’s estimated that nearly 6 million people in the United States are living with Alzheimer’s disease.

Alzheimer’s disease is a form of dementia that can progress from mild memory loss in the early stages to the potential for a person with the disease to have difficulty engaging in conversation or responding appropriately to what is around them.

There is currently no cure for Alzheimer’s disease, and treatment options are limited.

“There aren’t a lot of alternatives, particularly when it comes to drugs. There are drugs that can boost certain levels of neurotransmitters and, otherwise, potentially enhance cognition. But they don’t modify the actual underlying disease pathology or disease course,” Kaiser said.

“There are some minor symptomatic treatments. It’s akin to cough syrup for somebody who has a cold. It doesn’t actually cure or treat the underlying cold, it can just provide some symptomatic relief. And in terms of pharmacotherapy for Alzheimer’s disease… that’s all there is. That’s all that’s been approved in decades,” he added.

Lecanemab was granted breakthrough therapy designation by the Food and Drug Administration (FDA) in June 2021.

This status is designed to speed up the development of new drugs that will address medical needs that are currently unmet for serious or life-threatening conditions.

However, some scientists have expressed concern that the earlier phase 2 trials of lecanemab had flaws and that the actual benefit of the drug to people could be limited.

“The phase 2B lecanemab studies were fatally flawed because the high dose versus placebo analysis (that supposedly showed some clinical benefit) was profoundly compromised,” Dr. Michael Greicius, a professor of neurology and neurological sciences at Stanford University in California, told Healthline.

Greicius argues that in the phase 2B trial, people who were carriers of APOE4, a type of gene associated with an increased risk of Alzheimer’s disease, were prevented midway through the trial from receiving a high dose of the treatment.

“This means that there were many more APOE4 carriers in the placebo group (71 percent) than in the high dose group (30 percent),” Greicius explained. “This difference in percentage of APOE4 carriers is as likely (or in my view more likely) than the drug to account for the difference in clinical outcomes.”

A similar drug, Aduhelm, has been cleared for use.

In 2021, Aduhelm received FDA approval as the first new treatment for Alzheimer’s disease since 2003. It received approval on the basis of the drug being effective at reducing beta-amyloid plaque.

“This approval was met with a great deal of criticism by the scientific community because there are no compelling data to show that reducing amyloid plaque is associated with improved clinical outcomes,” Greicius said.

“Lecanemab also has a similar profile of dangerous side effects related to brain swelling and brain bleeding that we see with Aduhelm, though lecanemab is probably a bit friendlier than Aduhelm on this front in that ‘only’ 10 percent of patients in the high dose groups showed these side effects [in the phase 2 trial],” Greicius added.

He said that unless the phase 3 trials show a meaningful clinical slowing of decline in people, lecanemab is unlikely to be of much use.

“If these larger studies do show some benefit, it is likely (based on the skewed phase 2B results) to be small and of limited benefit to patients and their families,” he said.