Vol. 300, Issue 3, 984-991, March 2002

A Structure/Activity Relationship Study on Arvanil, an Endocannabinoid and Vanilloid Hybrid

Vincenzo Di Marzo, Graeme Griffin, Luciano De Petrocellis, Ines Brandi, Tiziana Bisogno, William Williams, Mark C. Grier, Sanjitha Kulasegram, Anu Mahadevan, Raj K. Razdan and Billy R. Martin

Endocannabinoid Research Group, Istituto di Chimica Biomolecolare, Pozzuoli (Napoli), Italy (V.D.M., I.B., T.B.); and Istituto di Cibernetica, Consiglio Nazionale delle Ricerche, Comprensorio Olivetti, Pozzuoli (Napoli), Italy (L.D.P.); Department of Pharmacology and Toxicology, Medical School of Virginia, Virginia Commonwealth University, Richmond, Virginia (G.G., B.R.M.); and Organix Inc., Woburn, Massachusetts (W.W., M.C.G., S.K., A.M., R.K.R.)

Arvanil, a structural "hybrid" between the endogenous cannabinoid CB₁ receptor ligand anandamide and capsaicin, is a potent agonist for the capsaicin receptor VR₁ (vanilloid receptor type 1), inhibits the anandamide membrane transporter (AMT), and induces cannabimimetic responses in mice. Novel arvanil derivatives prepared by N-methylation, replacement of the amide with urea and thiourea moieties, and manipulation of the vanillyl group were evaluated for their ability to bind/activate CB₁ receptors, activate VR₁ receptors, inhibit the AMT and fatty acid amide hydrolase (FAAH), and produce cannabimimetic effects in mice. The compounds did not stimulate the CB₁ receptor. Methylation of the amide group decreased the activity at VR₁, AMT, and FAAH. On the aromatic ring, the substitution of the 3-methoxy group with a chlorine atom or the lack of the 4-hydroxy group decreased the activity on VR₁ and AMT, but not the affinity for CB₁ receptors, and increased the capability to inhibit FAAH. The urea or thiourea analogs retained activity at VR₁ and AMT but exhibited little affinity for CB₁ receptors. The urea analog was a potent FAAH inhibitor (IC₅₀ = 2.0 µM). A water-soluble analog of arvanil, O-2142, was as active on VR₁, much less active on AMT and CB₁, and more potent on FAAH. All compounds induced a response in the mouse "tetrad", particularly those with EC₅₀ <10 nM on VR₁. However, the most potent compound, N-N'-di-(3-chloro-4-hydroxy)benzyl-arachidonamide (O-2093, ED₅₀ ~0.04 mg/kg), did not activate VR₁ or CB₁ receptors. Our findings suggest that VR₁ and/or as yet uncharacterized receptors produce cannabimimetic responses in mice in vivo.