GT-2203, also known as VUF-5296, (1R,2R)-cyclopropylhistamine, or (1R,2R)-trans-2-(1H-imidazol-4-yl)cyclopropylamine, is a histamine H<sub>3</sub> receptor agonist which was under development for the treatment of insomnia and anxiety disorders but was never marketed. Its route of administration was unspecified.
The drug is a synthetic derivative of the neurotransmitter histamine. The other enantiomer, (1S,2S)-cyclopropylhistamine (VUF-5297), is about 10-fold more potent than GT-2203 as a histamine H<sub>3</sub> receptor agonist. Both enantiomers are partial agonists of the receptor and both enantiomers show additional weak activity at the histamine H<sub>1</sub> and H<sub>2</sub> receptors.
GT-2203 was under development by Gliatech. It reached the preclinical research stage of development for insomnia and anxiety disorders prior to the discontinuation of its development in 2004. The drug was first described in the scientific literature by 1997. Aside from immethridine (BP-1-5375), GT-2203 is the only other selective histamine H<sub>3</sub> receptor agonist to have been developed for potential pharmaceutical use.