SB-742457, a 5-HT6 receptor antagonist, which extends into Alzheimer disease (AD) sufferers further highlights the therapeutic promise of this mechanistic approach. Alzheimer's disease is a devastating neurological condition characterized by a progressive decline in cognitive performance accompanied by behavioral and psychological syndromes, such as depression and psychosis. With the subsequent development of selective 5-HT6 receptor antagonists, preclinical studies in rodents and primates have elucidated the function of this receptor subtype in more detail. It is increasingly clear that blockade of 5-HT6 receptors leads to an improvement of cognitive performance in a wide variety of learning and memory paradigms and also results in anxiolytic and antidepressant-like activity. SB-742457 is generally safe and well tolerated and may be efficacious in Alzheimer disease.