Abstract summary 

Trace amine-associated receptor 1 (TAAR1) agonism shows promise for treating psychosis, prompting us to synthesise data from human and non-human studies.We co-produced a living systematic review of controlled studies examining TAAR1 agonists in individuals (with or without psychosis/schizophrenia) and relevant animal models. Two independent reviewers identified studies in multiple electronic databases (until 17.11.2023), extracted data, and assessed risk of bias. Primary outcomes were standardised mean differences (SMD) for overall symptoms in human studies and hyperlocomotion in animal models. We also examined adverse events and neurotransmitter signalling. We synthesised data with random-effects meta-analyses.Nine randomised trials provided data for two TAAR1 agonists (ulotaront and ralmitaront), and 15 animal studies for 10 TAAR1 agonists. Ulotaront and ralmitaront demonstrated few differences compared to placebo in improving overall symptoms in adults with acute schizophrenia (N=4 studies, n=1291 participants; SMD=0.15, 95%CI: -0.05, 0.34), and ralmitaront was less efficacious than risperidone (N=1, n=156, SMD=-0.53, 95%CI: -0.86, -0.20). Large placebo response was observed in ulotaront phase-III trials. Limited evidence suggested a relatively benign side-effect profile for TAAR1 agonists, although nausea and sedation were common after a single dose of ulotaront. In animal studies, TAAR1 agonists improved hyperlocomotion compared to control (N=13 studies, k=41 experiments, SMD=1.01, 95%CI: 0.74, 1.27), but seemed less efficacious compared to dopamine D receptor antagonists (N=4, k=7, SMD=-0.62, 95%CI: -1.32, 0.08). Limited human and animal data indicated that TAAR1 agonists may regulate presynaptic dopaminergic signalling.TAAR1 agonists may be less efficacious than dopamine D receptor antagonists already licensed for schizophrenia. The results are preliminary due to the limited number of drugs examined, lack of longer-term data, publication bias, and assay sensitivity concerns in trials associated with large placebo response. Considering their unique mechanism of action, relatively benign side-effect profile and ongoing drug development, further research is warranted.PROSPERO-ID: CRD42023451628.

Authors & Co-authors:  Siafis Spyridon S Chiocchia Virginia V Macleod Malcolm R MR Austin Charlotte C Homiar Ava A Tinsdeall Francesca F Friedrich Claire C Ramage Fiona J FJ Kennett Jaycee J Nomura Nobuyuki N Maksym Olena O Rutigliano Grazia G Vano Luke J LJ McCutcheon Robert A RA Gilbert David D Ostinelli Edoardo G EG Stansfield Claire C Dehdarirad Hossein H Juma Damian Omari DO Wright Simonne S Simple Ouma O Elugbadebo Olufisayo O Tonia Thomy T Mantas Ioannis I Howes Oliver D OD Furukawa Toshi A TA Milligan Lea L Moreno Carmen C Elliott Julian H JH Hastings Janna J Thomas James J Michie Susan S Sena Emily S ES Seedat Soraya S Egger Matthias M Potts Jennifer J Cipriani Andrea A Salanti Georgia G Leucht Stefan S

Study Outcome 

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