BACE1 and Cognitive impairment: It also examines the approaches of clinical trials and the trend of biomarker-based patient selection and precision medicine.<h4>Results</h4>Although β-site APP-cleaving enzyme 1 (BACE1) and secretase inhibitors did not achieve success in clinical trials because of mechanism-based toxicity and cognitive impairment, new monoclonal antibodies such as lecanemab and donanemab have shown high amyloid plaque clearance and reduced cognitive deterioration.