The drug from Eisai and Biogen slowed cognitive decline in study volunteers, but many had brain bleeds, swelling or other side effects
Researchers released new details from a study of a closely watched drug for Alzheimer’s disease on Tuesday, shedding more light on the drug’s risks and benefits as U.S. health regulators weigh approving it.
Eisai Co. and Biogen Inc.’s drug, called lecanemab, slowed cognitive decline by 27% compared with a placebo over 18 months in a study of more than 1,700 people with early-stage Alzheimer’s, researchers reported in the New England Journal of Medicine on Tuesday.
The drug’s effect was moderate, and was associated with swelling and bleeding in the brain, the researchers said. They recommended further, longer study of the drug.
Some 17.3% of patients taking lecanemab had signs of brain bleeding, compared with 9% in the placebo group. Brain swelling occurred in 12.6% of people getting the drug, versus 1.7% who got placebos.
The study data have been eagerly anticipated by Alzheimer’s researchers since Eisai disclosed high-level results in September, raising the hopes of doctors and patients that a new treatment proven to help Alzheimer’s patients is on the horizon.
The companies have asked the U.S. Food and Drug Administration to conditionally approve lecanemab based on an earlier study showing that the drug reduced levels of a protein in the brain called amyloid associated with Alzheimer’s. The agency is expected to make a decision by Jan. 6.
Eisai, which is leading the development of lecanemab, has said it plans to seek full approval using the new study data.
Some doctors said the latest data are likely good enough to support approval because the drug met the goals of the study, but questioned whether the drug’s effectiveness is strong enough to outweigh its potential harms for real-world use.
“No one yet knows whether the benefit will be clinically meaningful. This may take years to determine, and the debate is likely to continue,” said Samuel Gandy, professor of neurology and psychiatry at New York’s Mount Sinai.
Dr. Gandy and other doctors also raised concerns about recent reports of patients who died while taking lecanemab as part of ongoing testing. An Eisai spokeswoman said that the two patients who died had other significant medical problems and that the deaths couldn’t be attributed to lecanemab.
Alzheimer’s is a progressive disease that robs patients of their memories and the ability to carry out everyday tasks. Some six million people in the U.S. and tens of millions more worldwide have the condition.
Drugmakers have struggled to find drugs that slow Alzheimer’s march. Only a few medicines are approved in the U.S., and they mostly treat the symptoms.
Last year, the FDA approved another Alzheimer’s drug from Biogen and Eisai, but many doctors raised questions about its effectiveness, and Medicare and other health insurers balked at paying for it. In May, Biogen said it would effectively stop marketing the drug, called Aduhelm.
L ike Aduhelm, lecanemab was designed by researchers to reduce amyloid in the brain. Amyloid has long been associated with Alzheimer’s disease, though there is still no consensus on whether removing it will slow the disease.
The latest data come from a late stage, or Phase 3, study of 1,795 people ages 50 to 90 years with early Alzheimer’s who got either lecanemab or a placebo and were followed for 18 months.
Researchers measured patients’ clinical decline using an 18-point scale in which higher numbers indicate worse disease. Patients had an average score of about 3.2 when the study started, and were considered to have mild cognitive impairment or mild dementia.
Over the course of the study, placebo patients’ disease severity increased by 1.66 points on average, or 0.45 point more than patients who took lecanemab and whose scores increased by 1.21 points.
The difference amounted to a 27% slower decline over 18 months, but may not amount to a noticeable difference in patients’ cognitive function, said Michael Greicius, medical director of Stanford University’s Center for Memory Disorders.
More than one-quarter of lecanemab patients had negative reactions to the drug infusion, compared with 7.4% of patients in the placebo group.
The infusion-related side effects, in addition to the brain bleeding and swelling, may have tipped off some patients and their caregivers that they were receiving the drug and not placebos, which could potentially bias the study results, said Dr. Greicius.
“It’s not a benign therapy,” said Dr. Greicius. Even if the results withstand statistical analysis correcting for potential bias, “we’re still stuck with weighing this pretty borderline difference over 18 months with a drug that causes brain swelling in 12% of patients,” he said.
Write to Joseph Walker at joseph.walker@wsj.com
