Eisai Co. unveiled much-anticipated findings on its experimental Alzheimer’s drug, providing tinder for the hot debate over whether its modest efficacy is worth potential risks that include serious brain bleeding.
Lecanemab, developed with help from collaborator Biogen Inc., pulled large amounts of an Alzheimer’s-linked protein from the brain while slowing decline in mental capabilities and daily activities by 27% over 18 months, according to a commonly used rating scale. Yet this came at the price of side effects including brain swelling and bleeding that occurred in about 22% of people on the drug, compared to 10% of those who received a placebo.
The results are the main event at the often-sleepy Clinical Trials on Alzheimer’s Disease conference in San Francisco, and mark the first time a drug aimed at slowing the brain disease has generated unambiguously positive results in a final-stage trial.
Eisai’s shares, after swinging at the open of Tokyo trading Wednesday, were up about 2.5% at 10:39 a.m. local time, while Biogen was halted.
Still, the benefits of the drug appear modest, said Lon Schneider, a professor of psychiatry and neuroscience at the University of Southern California Keck School of Medicine.
“This is a very small effect, and the debate is going to be about whether it is clinically meaningful,” Schneider said in an email. However, the findings provide an opportunity “to assess subgroups that might have preferentially improved.”
Five presentations from researchers at Japan-based Eisai, Yale University and elsewhere were to delve into the benefits and side effects in great detail Tuesday. While most cases of swelling and bleeding weren’t symptomatic, they sometimes led to headaches, visual disturbances, confusion or worse. There were five large brain hemorrhages in patients who got the drug, compared to just one in the placebo group, according to results from the trial published in the New England Journal of Medicine.
The journal report doesn’t include two widely publicized patient deaths that occurred in the extension portion of the trial, when all subjects, including those on placebo, were offered the drug. Both deceased patients were taking blood thinners that may have contributed to bleeding in the brain.
“Both cases had significant comorbidities and risk factors including anticoagulation contributing to macrohemorrhage or death,” the company said. “Therefore, it is Eisai’s assessment that the deaths cannot be attributed to lecanemab.”
In an interview before the meeting, Michael Irizarry, Eisai senior vice president of clinical research, said there were “complicating factors” in both cases. In one, a man in his late 80s who had multiple other medical conditions suffered a heart attack following a brain hemorrhage. An examination indicated that the cause was cardiopulmonary, meaning the doctor’s opinion was that hemorrhage likely wasn’t the main cause of death, Irizarry said.