Furthermore, CSF Aβ40, along with Aβ42 and soluble amyloid precursor protein beta (sAPPβ; a direct product of BACE1 enzymatic activity), may be valuable in evaluating drugs such as verubecestat, a BACE1 (aspartyl protease β-site amyloid precursor protein cleaving enzyme 1) inhibitor that discriminatingly decreases Aβ42 and Aβ40 in Alzheimer’s disease patients [74]. Here, BACE1 is linked to Alzheimer disease.