RU-28253, also known as 5-MeO-THPI, is a non-selective serotonin receptor agonist of the tryptamine, 5-methoxytryptamine, and tetrahydropyridinylindole families. It is a tetrahydropyridylindole and a conformationally constrained analogue of 5-MeO-DMT.
The drug shows high affinity for the serotonin 5-HT<sub>1A</sub> receptor (K<sub>i</sub> = 5.7nM) and lower affinity for the serotonin 5-HT<sub>2A</sub> receptor (K<sub>i</sub> = 230nM). Its affinities for these receptors were higher than those of dimethyltryptamine (DMT). RU-28253 is described as a potent agonist of the serotonin 5-HT<sub>1</sub> and 5-HT<sub>2</sub> receptors, including of the serotonin 5-HT<sub>1B</sub> receptor, and is also an agonist of the serotonin 5-HT<sub>4</sub> receptor.
RU-28253 was first described in the scientific literature by 1983.