PipISB
PipISB is a drug used in scientific research which acts as a potent and selective inverse agonist of the cannabinoid receptor CB1. 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.