Amyloid-beta-targeting monoclonal antibodies for people with mild cognitive impairment or mild dementia due to Alzheimer's disease

RATIONALE: Alzheimer's disease is a neurodegenerative disorder and the most common cause of dementia. Aggregated amyloid-beta protein deposits are implicated in its pathogenesis. Amyloid-beta-targeting monoclonal antibodies (sometimes represented as Aβ-mAbs) are potentially disease-modifying for Alzheimer's disease: through the clearance of amyloid in the brain, they may slow cognitive and functional decline. OBJECTIVES: To assess the clinical benefits and harms of amyloid-beta-targeting monoclonal antibodies aducanumab, bapineuzumab, crenezumab, donanemab, gantenerumab, lecanemab, ponezumab, remternetug, and solanezumab in people with mild cognitive impairment or mild dementia due to Alzheimer's disease. SEARCH METHODS: We searched CENTRAL, MEDLINE (PubMed), Embase, and two clinical trials registries (Clinicaltrials.gov and WHO International Clinical Trials Registry Platform), and we undertook reference checking and citation research. The most recent search date was 7 August 2025. ELIGIBILITY CRITERIA: We included randomised controlled trials (RCTs) that lasted at least 12 months and compared amyloid-beta-targeting monoclonal antibodies with placebo or no treatment in people with mild cognitive impairment or mild dementia due to Alzheimer's disease. We included both parallel-group and cluster designs. OUTCOMES: Our outcomes of critical importance were: cognitive function; dementia severity; functional ability; any amyloid-related imaging abnormality (ARIA), which includes oedema (E) and haemorrhage (H); any symptomatic ARIA E and H; symptomatic brain haemorrhage; serious adverse events; and any-cause mortality. We analysed data at 12, 18, 24, and over 24 months of treatment. RISK OF BIAS: We used the Cochrane risk of bias tool RoB 2 to assess the risk of bias in outcomes of critical importance. SYNTHESIS METHODS: We meta-analysed results for each outcome within each comparison using the inverse variance method and the random-effects model. We used GRADE to assess the certainty of evidence for each outcome as very low, low, moderate, or high. INCLUDED STUDIES: Overall, we included 17 studies with 20,342 participants. The mean age of participants in the studies ranged from 70 to 74 years. Seven studies enroled only participants with mild dementia, and one study enroled only participants with mild cognitive impairment. The remaining studies included a mixed population. The mean duration of participants' cognitive impairment ranged from 17 to 52 months. The 17 studies assessed seven different amyloid-beta-targeting monoclonal antibodies: aducanumab (n = 3), bapineuzumab (n = 4), crenezumab (n = 2), donanemab (n = 1), gantenerumab (n = 4), lecanemab (n = 1), and solanezumab (n = 2). All used placebo as a comparison. Eleven studies lasted 18 months, four lasted 24 months, and two lasted more than 24 months. All studies were funded by the pharmaceutical industry. SYNTHESIS OF RESULTS: Below, we report the results of the studies at 18 months. Cognitive function Compared to placebo, amyloid-beta-targeting monoclonal antibodies probably result in little to no difference in cognitive function as measured by the ADAS-Cog (Alzheimer's Disease Assessment Scale-Cognitive) scale (standardised mean difference (SMD) -0.11, 95% confidence interval (CI) -0.16 to -0.06; 13 studies, 9895 participants; moderate certainty). Dementia severity Amyloid-beta-targeting monoclonal antibodies may result in little to no difference in dementia severity as measured by the CDR-SB (Clincal Dementia Rating Sum of Boxes) scale (SMD -0.12, 95% CI -0.24 to -0.00; 9 studies, 8053 participants; low certainty). Functional ability Amyloid-beta-targeting monoclonal antibodies probably result in little to no difference in functional ability as measured on the ADCS-ADL (Alzh