SB-224289 is a selective serotonin 5-HT<sub>1B</sub> receptor antagonist or inverse agonist which is used in scientific research. It is more than 75-fold selective for the serotonin 5-HT<sub>1B</sub> receptor over all other serotonin receptors. The drug indirectly increases serotonin release by blocking inhibitory serotonin 5-HT<sub>1B</sub> autoreceptors. In addition to its serotonin 5-HT<sub>1B</sub> receptor antagonism, SB-224289 has subsequently been found to counteract the antifungal effects of the marine depsipeptide papuamide A.