Alzheimer's: Few people in early stages are eligible for new drugs

  • In the past year, federal regulators have approved two new monoclonal antibody treatments for Alzheimer’s disease.
  • However, researchers report that only a small percentage of people in the early stages of the disease are eligible to be prescribed the two drugs.
  • Experts say it’s important to treat people with dementia as early as possible, so the lack of eligibility is a serious issue.

Only a small percentage of people with early stage Alzheimer’s disease are eligible for treatment using new monoclonal antibody drugs.

That’s according to research published today in the journal Neurology.

In their study, researchers report that because such a small number of people qualified for clinical trials of the drugs, only a small number of people meet the criteria for treatment with drugs such as aducanumab and lecanemab.

“There is hope that these new therapies for Alzheimer’s may slow progression of the disease for many people, although the fact remains that the drugs have only been studied in people with the earliest forms of the disease,” Maria Vassilaki, PhD, an epidemiologist at the Mayo Clinic in Rochester, Minnesota, and author of the study, said in a press statement.

“The inclusion and exclusion criteria of the clinical trials that led to FDA accelerated approval of these therapies form the basis of how people should be invited or discouraged from receiving one of these drugs. Our study estimates that only a small percentage of older people with early cognitive impairment due to Alzheimer’s may be eligible to be treated with monoclonal antibodies for amyloid-ß in the brain,” she added.

What the study on Alzheimer’s drugs revealed

The researchers examined 237 people between the ages of 50 to 90 who were experiencing mild dementia or cognitive impairment.

The subjects also had increased amounts of amyloid-ß plaques on brain scans.

The researchers then assessed these people against the inclusion and exclusion criteria for monoclonal antibody drugs lecanemab and aducanumab.

While the researchers found 47% of the participants met the inclusion criteria for the lecanemab trial, after applying the exclusion criteria they found just 8%, or only 19 people, would have been eligible.

Exclusion criteria included health issues such as cardiovascular disease, stroke, a history of cancer and brain injuries.

For aducanumab, just 5%, or 12 of the people studied, would have been eligible for the trial after accounting for inclusion and exclusion criteria. The aducanumab exclusion criteria also included health factors such as uncontrolled high blood pressure.

As FDA approval of the drugs is based on the findings of the clinical trials, the researchers say only a small amount of people with Alzheimer’s are likely to be eligible to use the drugs.

“Our study results show only a small percentage of people with early Alzheimer’s disease may be eligible to receive treatment, mostly due to chronic health conditions and brain scan abnormalities common in older adults,” said Vassilaki.

“In general, clinical trial participants are healthier than the general population. Additional research is needed to examine the safety and efficacy of monoclonal antibodies targeting amyloid-ß plaques in larger, more diverse populations, as well as in less healthy populations, before these therapies may be more widely available to people with Alzheimer’s disease,” she added.

How monoclonal antibody drugs treat Alzheimer’s

Monoclonal antibodies work by targeting amyloid-ß plaques in the brain, which can be a major pathological hallmark for Alzheimer’s disease.

Dr. Sharon Sha, a clinical professor of neurology and Chief for the Memory Disorders Division at Stanford University in California, says timing of treatment with monoclonal antibodies is critical.

“Because amyloid deposits 15 to 20 years prior to clinical symptoms, which is often memory loss, the key is to treat early to have the most benefit from the drug,” she told Medical News Today.

“The approval of these drugs were based on clinical trials that included people in early stages. Treating in moderate or late stages of the disease may not have any benefit and would change the risk/benefit profile of the drug,” Sha added.

Aducanumab was granted accelerated FDA approval in June 2021. Lecanemab was awarded accelerated approval in January 2023. This was then converted to traditional approval in July.

Lack of access for Alzheimer’s drugs

David Merrill, PhD, a geriatric psychiatrist and director of the Pacific Neuroscience Institute’s Pacific Brain Health Center in California, argues the majority of patients will be unlikely to benefit from these monoclonal antibody treatments.

“If you’re an average patient, coming into clinic hoping for this treatment, it’s almost miniscule chances that you will be able to be eligible to be offered the treatment in a way that’s considered on label,” he told Medical News Today. “That’s absolutely problematic, and it just goes to show that there’s so much more that needs to be done or addressed to help Alzheimer’s patients. To lessen the speed of the decline in their disease, to try to find the causes of dementia and for the vast majority of patients, that’s not going to be these treatments.”

“Removing amyloid may be dangerous for the majority of Alzheimer’s patients who have microbleeds in their brain to begin with, who have unstable medical conditions to begin with,” Merrill explained. “It’s just a real wake-up call that these antibody infusions, while they will have a role in treating Alzheimer’s, they’re not the end all be all and we need to keep working hard to figure out what are the factors that can be addressed, besides cleaning up amyloid in the brain.”

More Alzheimer’s research needed

The researchers argue their study highlights the importance of further research in a broader range of people.

They say Black and Hispanic people have been underrepresented in Alzheimer’s trials, even though they are more likely to experience Alzheimer’s or other forms of dementia.

Sha says this is an ongoing challenge for clinical trials.

“It is important to include broad, diverse populations in trials to better understand the benefit of these drugs in different types of patients,” she said. “However, people with lower socioeconomic status which often affects certain racial and ethnic groups have problems enrolling in trials due to lack of access to a trial center (distance, work, caregiver support, etc) and their health comorbidities. We as a community need to think and support ways to include broader communities in both clinical trials and clinical care so that we know whether these treatments are helpful for these patients.”

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