Salloway's study looked at the drug's safety in 194 Alzheimer's patients, most of whom had mild- to-moderate Alzheimer's and participated in a long-term (78 weeks or longer) study. Some of the participants were followed for four years or more.
Ninety-one percent of participants had side effects, about a quarter of which were attributable to bapineuzumab. Of these, 85 percent were mild or moderate.
The overall rate of vasogenic edema (water on the brain) was 9.3 percent, a number that decreased over time, said Salloway, a professor of neurology and psychiatry at Alpert Medical School of Brown University and director of the Butler Hospital Memory and Aging Program in Providence, R.I. The edema was symptomless in most cases, he said.
The other study, which involved looking at more than 2,000 MRI scans from 262 patients, found 36 cases of amyloid-related imaging abnormalities (ARIA) may have been linked to the bapineuzumab.
These imaging abnormalities may indicate inflammation of the brain caused by water retention.
But only 8 of those 36 cases involved symptoms, and they were more likely to be found in patients with APOE-e4 who were taking higher doses of the drug. The likelihood of these effects diminished with additional infusions of lower-dose bapineuzumab.
"There is a growing sense that VE [vasogenic edema] or ARIA [amyloid-related imaging abnormalities] is a manageable side effect and may actually be a sign that the drug is clearing amyloid from the brain and the blood vessels," said Salloway. "Treatment will require ongoing monitoring with MRI."
The researchers, who said monitoring of bapineuzumab will continue, are now awaiting the results of a larger Phase III trial on the drug.
Because this study was presented at a medical meeting, the data and conclusions should be viewed as preliminary until published in a pe
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