Of all the patients, 125 completed the treatment. Among the 40 who discontinued it, most withdrew due to negative side effects, which included fluid building up in the brain as a result of the removal of plaques. In some cases, this can cause brain bleeds.
Larger trials of the drug involving Alzheimer's patients are in progress and planned to run until at least 2020.
I wonder how many of those 40 had the fluid buildup?