MCHB-1 is a benzimidazole derived drug which was researched as an analgesic but never developed for medical use. It acts as a potent agonist of the CB<sub>2</sub> receptor, with an EC<sub>50</sub> of 0.52nM at CB<sub>2</sub>, and ~30x selectivity over CB<sub>1</sub> (Ki of 110nM at CB<sub>1</sub> vs 3.7nM at CB<sub>2</sub>). It has been sold online as a designer drug, first being identified in Germany in December 2013.