O-2050 is a drug that is a classical cannabinoid derivative, which acts as an antagonist for the CB1receptor. 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 CB1 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.
^Martin et al. SULFONAMIDE CANNABINOID AGONISTS AND ANTAGONISTS. US Patent 7279500, Oct 9 2007
^Gardner A, Mallet PE. Suppression of feeding, drinking, and locomotion by a putative cannabinoid receptor 'silent antagonist'. European Journal of Pharmacology. 2006 Jan 13;530(1-2):103-6. PMID 16380113
^Higuchi S, Irie K, Mishima S, Araki M, Ohji M, Shirakawa A, Akitake Y, Matsuyama K, Mishima K, Mishima K, Iwasaki K, Fujiwara M. The cannabinoid 1-receptor silent antagonist O-2050 attenuates preference for high-fat diet and activated astrocytes in mice. Journal of Pharmacological Sciences. 2010;112(3):369-72. PMID 20168044
^Higuchi S, Ohji M, Araki M, Furuta R, Katsuki M, Yamaguchi R, Akitake Y, Matsuyama K, Irie K, Mishima K, Mishima K, Iwasaki K, Fujiwara M. Increment of hypothalamic 2-arachidonoylglycerol induces the preference for a high-fat diet via activation of cannabinoid 1 receptors. Behavioural Brain Research. 2011 Jan 1;216(1):477-80. PMID 20817042
^Wiley JL, Breivogel CS, Mahadevan A, Pertwee RG, Cascio MG, Bolognini D, Huffman JW, Walentiny DM, Vann RE, Razdan RK, Martin BR. Structural and pharmacological analysis of O-2050, a putative neutral cannabinoid CB1 receptor antagonist. European Journal of Pharmacology. 2011 Jan 25;651(1-3):96-105. PMID 21114999