SN-22 is a piperidinylindole which acts as a moderately selective agonist at the 5-HT<sub>2</sub> family of serotonin receptors, with a K<sub>i</sub> of 19 nM at 5-HT<sub>2</sub> subtypes versus 514 nM at 5-HT<sub>1A</sub> receptors. Many related derivatives are known, most of which are ligands for 5-HT<sub>1A</sub>, 5-HT<sub>6</sub> or dopamine D<sub>2</sub> receptors or show SSRI activity.