GM-2040 is a putatively non-hallucinogenic serotonin 5-HT<sub>2A</sub> receptor agonist which was developed by Gilgamesh Pharmaceuticals. It is a partial agonist of the serotonin 5-HT<sub>2A</sub> receptor, with a K<sub>i</sub> of 3.4nM, an of 43.8nM, and an of 71.1%. Relative to the serotonergic psychedelic DOPR, the drug only weakly produces the head-twitch response (HTR), a behavioral proxy of psychedelic effects, in rodents, and hence may not produce hallucinogenic effects in humans. On the other hand, GM-2040 shows robust and persistent antidepressant-like effects in rodents.