Alzheimer's disease (AD) is pathologically characterized by deposition of amyloid plaques (comprising amyloid β [Aβ] protein) and neurofibrillary tangles (comprising tau protein), and neuronal death. Aβ monomers aggregate to form oligomers, protofibrils, and mature fibrils. Previously, the mature fibrils and plaques were implicated as contributors to neurotoxicity and neurodegeneration. However, a growing body of evidence proves stronger toxicity of oligomers and protofibrils. Among the many recent phase 3 clinical trials that have investigated the role of anti-Aβ antibodies in AD, some have shown the clinical efficacy of aducanumab, lecanemab, and donanemab in these patients. Lecanemab showed selectivity towards protofibrils over fibrils, and donanemab was specifically directed against Aβ only in brain-specific amyloid plaques. In contrast, other anti-Aβ antibodies did not show efficacy in AD.