SB-408124 is a drug which is a non-peptide antagonist selective for the orexin receptor subtype OX<sub>1</sub>, with around 70x selectivity for OX<sub>1</sub> over OX<sub>2</sub> receptors, and improved oral bioavailability compared to the older OX<sub>1</sub> antagonist SB-334867. It is used in scientific research into the function of orexinergic neurons in the body.