Dr. Thambisetty said the two deaths add to questions about lecanemab’s safety issues “in real world clinical practice where patients are likely to be sicker and have multiple other medical conditions in contrast to carefully selected patients in clinical trials.”
Nonetheless, the data on lecanemab, which Dr. Gandy noted attacks a different form of amyloid than previously tested drugs do, showed significantly lower rates of swelling and bleeding than with Aduhelm.
Nearly 13 percent of patients receiving lecanemab experienced brain swelling, which was mild or moderate in most cases, while less than 2 percent of patients receiving the placebo experienced such swelling, the study reported. Most brain swelling did not cause any symptoms and generally resolved within a few months. About 17 percent of lecanemab patients experienced brain bleeding, compared with 9 percent of patients receiving the placebo. The most common symptom from brain bleeds was dizziness, the study said.
The authors reported that “serious adverse events” occurred in 14 percent of lecanemab patients and 11 percent of those receiving placebo. Nearly 7 percent of lecanemab patients dropped out of the trial because of negative side effects, more than twice the percentage of placebo recipients who dropped out. More than a quarter of the lecanemab patients experienced adverse infusion-related reactions, which included fever and flu-like symptoms, usually with the first dose. A much smaller percentage of placebo patients experienced those reactions, the study found.
The main positive outcome of the study was that lecanemab patients declined cognitively by 1.21 points, while patients receiving placebo declined by 1.66 points on the 18-point scale, which assesses functions like memory, problem-solving and daily activities via interviews with patients and caregivers.
This result was supported by secondary measures in the trial, including three other cognitive tests, bolstering the possibility that the drug is having a real effect, experts said. In addition, on all the measures, patients began showing slower decline several months after starting lecanemab, and the pace slowed further during the 18-month trial.
The trial made an effort to include more participants of color than have typically been enrolled in Alzheimer’s trials. About 25 percent of those who participated in the trial in the United States were Black or Hispanic, the study reported. It also allowed people with various medical conditions to participate, including hypertension, diabetes, heart disease, obesity and kidney disease.