Nature Neuroscience study shows β-arrestin-biased 5-HT2AR agonist IHCH-8134 produces sustained antidepressant-like effects in mice without hallucinogenic responses

{"The study combined structural biology, cell signaling assays, and behavioral pharmacology. Researchers optimized IHCH-8134 from the earlier β-arrestin-preferring partial agonist IHCH-7086 published in Science 2022. In vitro, the ligand showed no detectable Gαq/Ca²⁺ activation yet robust β-arrestin recruitment. In vivo, single doses produced antidepressant-like responses in forced-swim and sucrose-preference tests that persisted beyond the drug's clearance; these effects were absent in 5-HT2AR or β-arrestin knockout mice.","Ligand dissociation kinetics explained the separation: LSD's slow off-rate allows cumulative β-arrestin signaling, while fast-dissociating analogs reduce hallucinogenic liability. IHCH-8134 exhibited no LSD-like head-twitch response in mice or motor/cognitive disruption in cynomolgus monkeys. This addresses a key regulatory barrier for psychedelic-derived antidepressants such as COMP360 and DT120, which still require supervised administration.","Contextual analysis reveals the work extends prior observational data linking 5-HT2AR to both therapeutic and adverse effects, yet remains limited to acute and subchronic rodent models. No human pharmacokinetic or safety data exist. Future studies must test whether the β-arrestin bias translates to durable remission in treatment-resistant depression without the 6-8 hour monitoring currently mandated.","Evidence quality note: The findings derive from interventional mouse and primate experiments with mechanistic knockouts; they establish proof-of-concept but cannot yet predict human efficacy or long-term safety. Randomized controlled trials in patients are required next."}