Amyloid-beta-targeting monoclonal antibodies do what they were designed to do - strip amyloid plaques out of the brain - but a new systematic review concludes they fall short of delivering meaningful cognitive improvement for patients. The review, published in the Cochrane Database of Systematic Reviews, assessed both the efficacy and the harms of these drugs in people with mild cognitive impairment or mild dementia due to Alzheimer's disease.
That gap between biological effect and clinical effect is the crux of the matter. Alzheimer's is defined neuropathologically by extracellular amyloid-beta plaques and intracellular neurofibrillary tangles of hyperphosphorylated tau, which together drive synaptic dysfunction, neuronal loss and cognitive decline. Antibody therapies target the first of those features. Clearing plaques on a brain scan, however, is not the same as helping someone hold onto memory, judgment and independence, and this review found the second does not reliably follow from the first.
For patients and families weighing these treatments, the practical implication is that the visible marker of success reported in trials - reduced amyloid burden - should not be read as a promise of better day-to-day functioning. Cochrane reviews pool evidence across studies rather than reporting a single trial's result, which is why they carry weight when a field's headline findings and its patient-level outcomes appear to diverge.
The findings sharpen a long-running question about the amyloid hypothesis and where Alzheimer's drug development should go next. If removing plaques is not enough, researchers face pressure to look harder at tau pathology and other mechanisms of neuronal damage, or at intervening far earlier in the disease process than the mild cognitive impairment stage.