“While the prediction is that the F.D.A. will approve lecanemab, there are issues of safety,” said Dr. Sam Gandy, an Alzheimer’s clinician who is director of the Mount Sinai Center for Cognitive Health and was not involved in the study.
Concerns about the safety of lecanemab — at least for some types of patients, especially those taking blood thinners — have been fueled recently by news reports of the deaths of two patients who experienced brain swelling and brain bleeding. Swelling and bleeding are known side effects of several anti-amyloid drugs. If lecanemab ends up being considered unsafe for people taking blood thinners, then tens of thousands of patients could be excluded.
The study published Tuesday reported six deaths among the trial’s 898 lecanemab patients and seven deaths among the 897 patients receiving placebo. The authors wrote that no deaths were considered to be related to lecanemab or to have occurred with brain swelling or bleeding.
The two recently reported deaths occurred after the 18-month randomized portion of the trial, so the deaths of those trial participants are not included in the study and it is not known if those patients received lecanemab or placebo during that time. But after the 18 months, both patients opted to receive lecanemab in an open-label extension study.
The patients, whose cases were reported by the journal Science and STAT, had other medical complications. One case involved a 65-year-old woman who suffered a stroke and, after receiving a standard treatment for stroke-related blood clots, suffered serious brain bleeding and died a few days later. A neuropathologist who conducted an autopsy at the request of the woman’s husband told the journal that lecanemab likely weakened her blood vessels and made them vulnerable to bursting when she received the blood-clotting treatment.
The other case involved a man in his late 80s who was taking a blood thinner for a heart condition and had also experienced falls and ministroke-like events shortly before his death.
In a statement, Eisai, citing the patients’ other medical conditions and blood-thinning medication, said, “It is Eisai’s assessment that the deaths cannot be attributed to lecanemab.” The company said that in the trial’s randomized and open-label phases, the total rate of deaths with major brain bleeds was 0.1 percent for patients in both the lecanemab and placebo groups.