APOE and Alzheimer disease: This review examines the biological rationale linking APOE4 status to disordered lipid metabolism in both peripheral and central compartments, the genetic and epidemiological evidence supporting CETP as a therapeutic target, the mechanisms through which CETP inhibition might confer neuroprotection, and the clinical data suggesting obicetrapib as the first oral agent associated with favorable changes in AD biomarkers across both amyloid and tau axes in individuals at high genetic risk for the development of AD.