O-2050 is a drug that is a classical cannabinoid derivative, which acts as an antagonist for the CB<sub>1</sub> receptor. This gives it an advantage in research over many commonly used cannabinoid antagonists, such as rimonabant, which at higher doses act as inverse agonists at CB<sub>1</sub> as well as showing off-target effects. However, while O-2050 acts as a silent antagonist in vitro, some tests in vivo have suggested it may show agonist activity under certain circumstances.