AR-A000002, also known as AZD-8129, is a drug which is one of the first compounds developed to act as a selective antagonist for the serotonin receptor 5-HT<sub>1B</sub>, with approximately 10x selectivity for 5-HT<sub>1B</sub> over the closely related 5-HT<sub>1D</sub> receptor. It has been shown to produce sustained increases in levels of serotonin in the brain, and has anxiolytic effects in animal studies.