SR144528 is a drug that acts as a potent and highly selective CB₂ receptor inverse agonist, with a K_i of 0.6 nM at CB₂ and 400 nM at the related CB₁ receptor. It is used in scientific research for investigating the function of the CB₂ receptor, as well as for studying the effects of CB₁ receptors in isolation, as few CB₁ agonists that do not also show significant activity as CB₂ agonists are available. It has also been found to be an inhibitor of sterol O-acyltransferase, an effect that appears to be independent from its action on CB₂ receptors.