Discovery and Characterization of a Highly Selective FAAH Inhibitor that Reduces Inflammatory Pain

Abstract

Endocannabinoids are lipid signaling molecules that regulate a wide range of mammalian behaviors, including pain, inflammation, and cognitive/emotional state. The endocannabinoid anandamide is principally degraded by the integral membrane enzyme fatty acid amide hydrolase (FAAH), and there is currently much interest in developing FAAH inhibitors to augment endocannabinoid signaling in vivo. Here we report the discovery and detailed characterization of a highly efficacious and selective FAAH inhibitor PF-3845. Mechanistic and structural studies confirm that PF-3845 is a covalent inhibitor that carbamylates FAAH's serine nucleophile. PF-3845 selectively inhibits FAAH in vivo as determined by activity-based protein profiling and raises brain anandamide levels for up to 24 hrs, resulting in profound cannabinoid receptor-dependent reductions in inflammatory pain. These data thus designate PF-3845 as a valuable pharmacological tool for in vivo characterization of the endocannabinoid system.

Cellular and intracellular mechanisms involved in the cognitive impairment of cannabinoids

“…AEA is mainly degraded by fatty acid amide hydrolase (FAAH) [44], whereas 2-AG is primarily metabolized by monoacylglycerol lipase (MAGL) [45]. Therefore, the action of AEA can be prolonged by inhibiting its degradation through FAAH enzyme inhibitors, such as URB532, URB597 [46], OL-135, OL-92 [47] and PF-3845 [48]. On the other hand, endogenous 2-AG concentrations can be enhanced by the administration of the selective MAGL inhibitor JZL184 [49].…”

Therapeutic Potential of Fatty Acid Amide Hydrolase, Monoacylglycerol Lipase, and N-Acylethanolamine Acid Amidase Inhibitors

“…To improve the binding affinity for FAAH, replacement of the quinoline with different biaryl ether functions was performed and the pharmacological activities were profiled as kinact/Ki values. 95 These modifications led to the discovery of a potent, selective, covalent, irreversible FAAH inhibitor, compound 62 (PF-3845, Figure 27). 95 The profile of inhibitory potency indicated that 62 possessed an impressive kinact/Ki value of 12600 M -1 s -1 for hFAAH, which was 8 times and 16 times more than 30 and 60, respectively.…”

“…95 These modifications led to the discovery of a potent, selective, covalent, irreversible FAAH inhibitor, compound 62 (PF-3845, Figure 27). 95 The profile of inhibitory potency indicated that 62 possessed an impressive kinact/Ki value of 12600 M -1 s -1 for hFAAH, which was 8 times and 16 times more than 30 and 60, respectively. Indeed, compound 62 showed rapid elevation of brain AEA, PEA, and OEA levels in mice brain.…”

The evolution and comparative neurobiology of endocannabinoid signalling

“…In 1996, Cravatt et al [36] identified an enzyme known as fatty acid amide hydrolase (FAAH), which converts anandamide to arachidonic acid and ethanolamine, and subsequent analysis of FAAH-knockout mice and mice treated with selective FAAH inhibitors have demonstrated that FAAH has a major role in regulation of anandamide levels in the brain [37,38]. In humans, but not in rodents, there is a second FAAH-like enzyme, which is known as FAAH-2 [39].…”