RS134-49, also known as 4-methyl-THPI, is a tetrahydropyridinylindole (THPI) derivative related to psychedelic tryptamines which acts as a 5-HT<sub>2A</sub> receptor agonist, with a 5-HT<sub>2A</sub> K<sub>i</sub> of 11.5nM and an EC<sub>50</sub> of 22nM. It is a biased agonist selective for activation of the G<sub>q</sub> coupled signalling pathway with weaker activation of the ò-arrestin 2 coupled pathway, but shows a more balanced profile than related compounds such as (R)-69.