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Experimental Alzheimer's drug shows benefits in phase 3 trial, company says

Japanese drugmaker Eisai said cognitive decline slowed over 18 months in patients who received the drug, called lecanemab.
Scan of the brain of a patient affected by Alzheimer's Disease in an axial section.
The brain of a patient affected by Alzheimer's disease in a scan of an axial section. BSIP / UIG via Getty Images

The Japanese drugmaker Eisai said Tuesday its experimental drug for Alzheimer’s disease helped slow cognitive decline in patients in the early stages of the illness.

The company said that in a phase 3 clinical trial, the drug, called lecanemab, slowed cognitive decline by 27% after 18 months. The results were announced in a news release and have not yet been peer-reviewed. 

The results may offer renewed hope to Alzheimer’s patients after the U.S. drugmaker Biogen’s botched rollout of its drug, Aduhelm, last year. Biogen partnered with Eisai in the commercialization of the new drug, although Eisai led its development and the phase 3 trial.

Outside experts urged caution in interpreting the results, however.

The results are “a first step in the direction of making a significant impact on the disease,” said Dr. Ronald Petersen, a neurologist at the Mayo Clinic in Rochester, Minnesota.

Dr. Alberto Espay, a neurologist at the University of Cincinnati College of Medicine, said that the benefit was "small" and that it fell below the threshold of what would be meaningful to a patient. Still, he said, "patients can view this with cautious optimism."

The results were based on 1,795 patients, who were randomly assigned to receive either the drug or a placebo every two weeks over 18 months. Cognitive decline was measured using a clinical dementia rating scale that focused on six areas: memory, orientation, judgment and problem solving, community affairs, home and hobbies, and personal care.

Brain swelling was seen in 12.5% of those who received the medication, compared to 1.7% in the placebo group, according to Eisai. However, many of those with brain swelling did not experience symptoms and the prevalence of that side effect was lower than what has been seen with other similar experimental drugs, the company said on a call on Tuesday.

Eisai said that it will present the findings at an Alzheimer’s conference in late November and that it plans to submit the trial data to the Food and Drug Administration for approval by March. 

The company noted, however, that the FDA has already agreed to consider the drug under the agency's so-called accelerated approval pathway — the same process used to approve Biogen's Aduhelm. Eisai said the agency is expected to make a decision on conditional approval by early January.

Eisai's drug is a monoclonal antibody designed to target amyloid plaques, clumps of protein in the brain long considered a hallmark of Alzheimer’s.

Biogen's drug Aduhelm was shown to reduce amyloid in the brain, but that didn't translate into a slower progression of the disease. That is leading some scientists to shift from amyloid as a cause of Alzheimer's and look at other possibilities.

While the results appear to be positive, the single trial is unlikely to prove that amyloid is responsible for the decline in mental function often seen in patients, Espay said.

But Petersen, of the Mayo Clinic, said the trial may show that amyloid is in fact one of several components that lead to the progression of the disease.

"This is really positive for the field," he said of the trial results. "I think it's going to motivate a lot more beneficial research down the road."

He also advocated for more research into preventing the disease, noting that the new drug "is not a cure by any means.”

Besides Biogen’s drug, all other drugs approved by the FDA for Alzheimer’s are aimed at helping symptoms, not actually slowing the progression of the disease, which is the seventh-leading cause of death in the U.S., according to the Centers for Disease Control and Prevention.

Two similar drugs — from Roche and Eli Lilly — are expected to release late-stage clinical trial results over the next few months.

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