Regarding this topic, Cristina Sampaio (Faculdade de Medicina de Lisboa) mentioned that although it may currently be impossible to accurately identify certain subpopulations (particularly, “at-risk” or “pre-dementia” cases), this would not preclude regulatory agencies from considering trials directed at certain readily identifiable subpopulations (e.g., “familial-type” AD, or APOE ε4 carriers) or other biomarker-defined subtypes, once they have been properly validated. This evidence concerns the gene APOE and Alzheimer disease.