Among these 5-HT6R antagonists, 2 (idalopirdine) was studied in phase 3 of clinical trials (Wilkinson et al., 2014), and 3 (landipirdine), a dual antagonist of the 5-HT6 and 5-HT2A receptors is currently under investigation in the field of Parkinson Disease (Figure 1; Ellis and Fell, 2017). This evidence concerns the gene HTR6 and Parkinson disease.