PipISB is a drug used in scientific research which acts as a potent and selective inverse agonist of the cannabinoid receptorCB1. It is highly selective for the CB1 receptor over CB2, with a Kd at CB1 of 1.5nM vs over 7000nM at CB2, has good blood-brain barrier penetration, and can be conveniently radiolabelled with either 11C or 18F, making it useful for mapping the distribution of CB1 receptors in the brain.
^Donohue, Sean R.; Halldin, Christer; Schou, Magnus; Hong, Jinsoo; Phebus, Lee; Chernet, Eyassu; Hitchcock, Stephen A.; Gardinier, Kevin M.; Ruley, Kevin M.; Krushinski, Joseph H.; Schaus, John; Pike, Victor W. (2008). "Radiolabeling of a high potency cannabinoid subtype-1 receptor inverse agonist, N-(4-fluoro-benzyl)-4-(3-(piperidin-1-yl-indole-1-sulfonyl)benzamide (PipISB), with carbon-11 or fluorine-18". Journal of Labelled Compounds and Radiopharmaceuticals51 (3): 146. doi:10.1002/jlcr.1491.edit