Salloway S, Chalkias S, Barkhof F, et al. - In the phase 3 studies of aducanumab for Alzheimer disease, occurrence of amyloid-related imaging abnormalities (ARIA) was evident in approximately 40% of participants, and about one-quarter of these patients developed symptoms.

• This is a secondary analysis of data from the EMERGE and ENGAGE trials, two phase 3 randomized clinical trials that compared low-dose and high-dose aducanumab therapy with placebo in participants at 348 sites across 20 countries.

• The integrated studies involved 3,285 patients with Alzheimer disease treated with 1 or more doses of placebo (n = 1,087) or aducanumab (n = 2,198; 2,752 total person-years of exposure) during the placebo-controlled period.

• ARIA developed in 425 patients (41.3%) in the combined 10 mg/kg aducanumab group (n = 1,029); ARIA-edema (the most common adverse event in the 10-mg/kg group) occurred in 362 patients (35.2%), and associated symptoms [eg, headache (most common), confusion, dizziness, and nausea] were present in 94 of these patients (26.0%).

• Occurrence of ARIA-microhemorrhage and ARIA–superficial siderosis was evident in 197 patients (19.1%) and 151 patients (14.7%), respectively.