Abstact

Drugs that target the human serotonin 2A receptor (5-HT2AR) are used to treat neuropsychiatric diseases; however, many have hallucinogenic effects, hampering their use. Here, we present structures of 5-HT2AR complexed with the psychedelic drugs psilocin (the active metabolite of psilocybin) and d-lysergic acid diethylamide (LSD), as well as the endogenous neurotransmitter serotonin and the nonhallucinogenic psychedelic analog lisuride. Serotonin and psilocin display a second binding mode in addition to the canonical mode, which enabled the design of the psychedelic IHCH-7113 (a substructure of antipsychotic lumateperone) and several 5-HT2AR β-arrestin-biased agonists that displayed antidepressant-like activity in mice but without hallucinogenic effects. The 5-HT2AR complex structures presented herein and the resulting insights provide a solid foundation for the structure-based design of safe and effective nonhallucinogenic psychedelic analogs with therapeutic effects.