LY2183240 is a highly potent blocker of anandamide uptake with IC50 value of 270 pM, and an inhibitor of fatty acid amide hydrolase (FAAH) activity with IC50 value of 12.4 nM [1].

Fatty acid amide hydrolase (FAAH) belongs to the family of serine hydrolase, which is an integral membrane enzyme. It has esterase and amidase activity that are responsive for the uptake of fatty acid amide (FAA) family signaling lipids, including anandamide. The uptake and metabolic process of anandamide is mainly achieved by FAAH, therefore the inhibition of FAAH may result in the blockage of anadaminde uptake.

LY2183240 is a potent and covalent inhibitor of FAAH, with the effect of blocking anandamide uptake. Biochemical research had identified that LY2183240 inactivate FAAH via carbamylation of the serine nucleophile of FAAH [2]. In RBL cell line containing FAAH, radioactive labeled 3H-LY2183240 exhibited strong binding to FAAH, inhibition of FAAH and thus blockage of anandamide uptake. However, in HeLa cells lacking FAAH, 3H-LY2183240 was less bound, and the blockage of anandamide uptake was very weak. It suggested that the direct interaction between LY2183240 and FAAH was required to block the anandamide uptake. However, it also indicated that there might be uncharacterized pathways of anandamide uptake regulated by LY2183240, independent from FAAH [1]. However, FAAH is not the sole target for LY2183240. Several uncharacterized brain serine hydrolases were also identified as the target of LY2183240, and these might be additional pathway for anandamide uptake [2].

In mouse model, 10 mg/kg injection of LY2183240 would produce analgesic effects in the formalin test of noxious pain which is a phenotype associated with elevated level of anandamide in brain. It indicated LY2183240 might inhibit FAAH in vivo [2]. When mice were administrated with LY2183240 (10 mg/kg, ip) for 90 min, characterization of brain tissues revealed that LY2183240 inactivated FAAH and other brain serine hydrolases ranging from 25-35 kDa [2].

References:
[1] Dickason-Chesterfield A K et al. , Pharmacological characterization of endocannabinoid transport and fatty acid amide hydrolase inhibitors. Cell Mol Neurobiol. 2006, 26(4-6): 407-23.
[2] Alexander J P, Cravatt B F.  The putative endocannabinoid transport blocker LY2183240 is a potent inhibitor of FAAH and several other brain serine hydrolases. J Am Chem Soc. 2006, 128(30): 9699-9704.