Identification and characterization of a new reversible MAGL inhibitor Tiziano Tuccinardi a,⇑ , Carlotta Granchi a , Flavio Rizzolio b , Isabella Caligiuri b , Vittoria Battistello a , Giuseppe Toffoli b , Filippo Minutolo a , Marco Macchia a , Adriano Martinelli a a Department of Pharmacy, University of Pisa, 56126 Pisa, Italy b Division of Experimental and Clinical Pharmacology, Department of Molecular Biology and Translational Research, CRO National Cancer Institute and Center for Molecular Biomedicine, IRCCS, Aviano (PN), Italy article info Article history: Received 27 February 2014 Accepted 28 April 2014 Available online xxxx Keywords: Monoacylglycerol lipase inhibitors Virtual screening MAGL Hydrolase abstract Monoacylglycerol lipase is a serine hydrolase that play a major role in the degradation of 2-arachidonoyl- glycerol, an endocannabinoid neurotransmitter implicated in several physiological processes. Recent studies have shown the possible role of MAGL inhibitors as anti-inflammatory, anti-nociceptive and anti-cancer agents. The use of irreversible MAGL inhibitors determined an unwanted chronic MAGL inactivation, which acquires a functional antagonism function of the endocannabinoid system. However, the application of reversible MAGL inhibitors has not yet been explored, mainly due to the scarcity of known compounds possessing efficient reversible inhibitory activities. In this study we reported the first virtual screening analysis for the identification of reversible MAGL inhibitors. Among the screened compounds, the (4-(4-chlorobenzoyl)piperidin-1-yl)(4-methoxyphenyl)methanone (CL6a) is a promising reversible MAGL inhibitor lead (K i = 8.6 lM), which may be used for the future development of a new class of MAGL inhibitors. Furthermore, the results demonstrate the validity of the methodologies that we followed, encouraging additional screenings of other commercial databases. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction Monoacylglycerol lipase (MAGL) is a 33 kDa cytosolic serine hydrolase that preferentially cleaves monoacylglycerols into fatty acids and glycerol, with the highest expression in brain, adipose tissue and liver. 1 This protein contains two lipase motives (active serine motif GXSXG and the HG dipeptide) with a Ser/His/Asp catalytic triad, and belongs to the ‘a/b hydrolases fold family’, whose conserved three-dimensional structure consists of a central b sheet surrounded by a variable number of a helices. After standing as a little interest enzyme for many years, Piomelli and co-workers found out that it plays a fundamental role in the deactivation of the endocannabinoid 2-arachidonoglycerol (2-AG), a monoglyceride of arachidonic acid esterified at the sn-2 position, which tunes the functionality and plasticity of many synapses. 2 2-AG exhibits a full agonist efficacy for both CB1 and CB2 cannabinoid receptors. 3 Unlike the classical neurotransmitters, it is produced on demand from membrane lipid precursors and after its action has been effected, it is rapidly taken up by cells and hydrolyzed. Very recently, Nomura et al. showed that in specific tissues such as brain, liver and lung, MAGL acts as a metabolic switch able to connect the endocannabinoid and the eicosanoid lipid signaling systems: through the hydrolysis of 2-AG, MAGL releases a major arachidonic acid precursor pool for the synthesis of pro-inflammatory eicosanoids such as prostaglandins PGE 2 and PGD 2 . 4 In agreement with the role of MAGL in modulating the 2-AG-mediated endocannabinoid signaling, in vivo studies showed that the inhibition of MAGL exerts CB1-dependent antinociceptive effects. 5 In 2012, Chen et al. demonstrated that the inhibition of MAGL by a covalent inhibitor resulted in significantly diminished amyloid neuropathology, reduced neuroinflammation and degen- eration, and improved synaptic and cognitive function in a mouse model of Alzheimer’s disease. 6 In aggressive cancer cells and primary tumors, MAGL is upregulated and has a unique role of providing lipolytic source of free fatty acids for the synthesis of oncogenic signaling lipids that promote cancer aggressiveness. 7 Other studies showed that MAGL inhibitors impair colorectal cancer tumorigenesis 8 and prostate cancer pathogenicity. 9 Taken together all these findings strongly suggest that MAGL inhibition could determine significant therapeutic benefits. Over the past five years, great efforts have been made for developing novel MAGL inhibitors; 10–15 however, almost all the reported compounds are characterized by an irreversible MAGL inhibition mechanism and, http://dx.doi.org/10.1016/j.bmc.2014.04.057 0968-0896/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Tel.: +39 0502219595. E-mail address: tiziano.tuccinardi@farm.unipi.it (T. Tuccinardi). Bioorganic & Medicinal Chemistry xxx (2014) xxx–xxx Contents lists available at ScienceDirect Bioorganic & Medicinal Chemistry journal homepage: www.elsevier.com/locate/bmc Please cite this article in press as: Tuccinardi, T.; et al. Bioorg. Med. Chem. (2014), http://dx.doi.org/10.1016/j.bmc.2014.04.057