Those who got Leqembi in a clinical trial for 18 months experienced 27% less decline in memory and thinking relative to the group who got a placebo. It also reduced amyloid in the brain, the sticky protein that builds up in the brains of people with Alzheimer’s and is considered a hallmark of the disease.
Howard Fillit, MD, co-founder and chief science officer of the Alzheimer’s Drug Discovery Foundation, says, “It’s the first phase III study in our field of a disease-modifying drug where the clinical efficacy was very clear.”
Concerns About Side Effects
The drug has raised safety concerns as it has been linked with certain serious adverse events, including brain swelling and bleeding. In the trial, 14% of patients who received the drug experienced side effects that included brain swelling and bleeding, compared to about 11% in the placebo group.
Scientists have reportedly linked three deaths during the clinical trial to lecanemab, though it is unclear whether it caused the deaths.
Fillit notes that the first two people who died were on blood thinners when they received lecanemab.
“There are things about the use of the drug in the real world that we need to work out, especially in the context of people with comorbidities,” he says.
The third death is a little different, Fillit says. The patient, who had a stroke, showed signs of vasculitis, or inflammation of the blood vessels.
“We don’t know exactly what happened, but we do know it was very, very rare” among the people involved in the trials, he says.
Edelmayer says that the most common reported side effects during the trials were infusion-related reactions, headache, and amyloid-related imaging abnormalities (ARIA). According to the FDA, these abnormalities “are known to occur with antibodies of this class. ARIA usually does not have symptoms, although serious and life-threatening events rarely may occur.”
The FDA has added these as warnings to the drug’s label, describing the possible infusion-related reactions as flu-like symptoms, nausea, vomiting, and changes in blood pressure.
How Much Will It Cost?