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FDA Postpones Decision on Potential Alzheimer’s Treatment

Regulators to ask a panel of experts to review clinical trial data on donanemab

spinner image scan of a brain that is showing signs of alzheimers disease
Alamy Stock Photo

Federal regulators are delaying action on donanemab, a potential treatment for Alzheimer’s disease that was widely expected to gain approval in the first quarter of this year.

Drugmaker Eli Lilly announced March 8 that the Food and Drug Administration (FDA) wants to convene an advisory committee meeting to further discuss the safety and efficacy data from the drug’s phase 3 clinical trial. The date for this meeting has yet to be set.

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In a news release, the company said the FDA’s decision to meet with its panel of outside experts was unexpected but follows precedent and was part of the approval process for Leqembi (lecanemab), a similar Alzheimer’s treatment that was approved in 2023.

“Today’s FDA decision is not a setback, but another step forward in the drug approval process, with the regulatory agency doing its due diligence before the distribution of the drug to patients,” Howard Fillit, M.D., cofounder and chief science officer of the Alzheimer’s Drug Discovery Foundation, said in a statement.

Donanemab trial showed promising results 

Clinical trial results for donanemab were presented at the 2023 Alzheimer’s Association International Conference in July and published in the peer-reviewed medical journal JAMA. Researchers found that the experimental medication significantly slowed the loss of thinking and memory skills in people with early Alzheimer’s, with the greatest benefits seen among those in the earliest stages of the disease.

Donanemab also helped to remove a protein called amyloid from the brain, which is a defining feature of Alzheimer’s. In people with the disease, amyloid clumps together to form sticky plaques that disrupt normal cell function.

Experts say delaying the more severe stages of Alzheimer’s, which affects more than 6.5 million Americans, is not a cure but can help preserve a person’s level of functioning for longer. This can be particularly helpful for those who are still able to work, pay bills and engage with others, as is the case for many individuals with early Alzheimer’s.

“These benefits are real and meaningful, giving people more time to participate in daily life, remain independent and make future health care decisions,” Maria C. Carrillo, chief science officer for the Alzheimer’s Association, said in a statement.

Researchers leading the 18-month-long trial found that Alzheimer’s symptoms did not worsen after a year of treatment for nearly half of participants who received donanemab, compared with 29 percent who received a placebo. The study results also suggest that people may not need the treatment indefinitely; patients in the study were taken off the drug once a certain amount of amyloid was removed from the brain.  


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In its March 8 news release, Lilly said this “limited-duration dosing regimen that allowed patients to complete treatment based on an assessment of amyloid plaque” is one of the topics the FDA wants to further understand.

Approval could add more options for treatment

The drug’s manufacturer is seeking full, traditional FDA approval for donanemab. Until Leqembi’s 2023 approval, the only Alzheimer’s drugs with full FDA approval were medications that help to alleviate some of the disease’s symptoms, not disrupt its course.

Like Leqembi, donanemab is a monoclonal antibody given by infusion. Side effects reported in the donanemab trial were similar to those seen with Leqembi, with swelling and bleeding in the brain being the chief concerns. Often these events are small, temporary and asymptomatic, but larger bleeds can occur and can be serious, even fatal.

Even as the FDA decides whether to approve this latest medication, the search for effective Alzheimer’s treatments continues. Fillit of the Alzheimer’s Drug Discovery Foundation said in a statement that the latest amyloid-attacking drugs are “just a start” and that “we must continue advancing the drug pipeline to develop the next class of drugs centered around the biology of aging to ultimately stop Alzheimer’s in its tracks.”

Hundreds of potential treatments are being studied, including by the AARP-backed Dementia Discovery Fund, and many have targets other than amyloid. 

“Alzheimer’s disease and related dementias are complex disorders, caused by a constellation of overlapping and intertwined chains of biochemical reactions that wreck the brain,” Richard J. Hodes, M.D., director of the National Institute on Aging, said in a statement. “Successfully treating each individual’s dementia will likely require a diverse set of preventative and diagnostic therapies. The data reported in these donanemab and lecanemab studies suggest that anti-amyloid therapies may, at least, be the first of many other treatments.”

Video: How I Discovered I Had Early-Onset Alzheimer's

Editor's note: This story, first published July 18, 2023, has been updated to include new information.

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