APOE and Alzheimer disease: Several studies indicate that the presence of the APOE-4 allele differentially affects the quality and extent of drug responsiveness in AD patients treated with cholinergic enhancers (tacrine, donepezil, galantamine, and rivastigmine), neuroprotective compounds (nootropics), endogenous nucleotides (CDP-choline), immunotrophins (anapsos), neurotrophic factors (cerebrolysin), rosiglitazone, or combination therapies [5–7, 9, 105, 112, 113, 138, 140]; however, controversial results are frequently found due to methodological problems, study design, and patient recruitment in clinical trials.