Recently, Cummings et al. [86] carried out a placebo-controlled, randomized, double-blind, parallel-group study of a single dose (300 mg per day) of bexarotene (a highly specific agonist of retinoid X receptor) in individuals with AD and both noncarriers and carriers of the apolipoprotein E (APOE) allele. Here, APOE is linked to Alzheimer disease.