Fatty acid binding proteins (FABPs) serve as critical modulators of endocannabinoid signaling by facilitating the intracellular transport of anandamide and whose inhibition potentiates anandamide signaling. Our previous work has identified a novel small-molecule FABP inhibitor, α-truxillic acid 1-naphthyl monoester (SB-FI-26, 3) that has shown efficacy as an antinociceptive and anti-inflammatory agent in rodent models. In the present work, we have performed an extensive SAR study on a series of 3-analogs as novel FABP inhibitors based on computer-aided inhibitor drug design and docking analysis, chemical synthesis and biological evaluations. The prediction of binding affinity of these analogs to target FABP3, 5 and 7 isoforms was performed using the AutoDock 4.2 program, using the recently determined co-crystal structures of 3 with FABP5 and FABP7. The compounds with high docking scores were synthesized and evaluated for their activities using a fluorescence displacement assay against FABP3, 5 and 7. During lead optimization, compound 3l emerged as a promising compound with the Ki value of 0.21 μM for FABP 5, 4-fold more potent than 3 (Ki, 0.81 μM). Nine compounds exhibit similar or better binding affinity than 3, including compounds 4b (Ki, 0.55 μM) and 4e (Ki, 0.68 μM). Twelve compounds are selective for FABP5 and 7 with >10 μM Ki values for FABP3, indicating a safe profile to avoid potential cardiotoxicity concerns. Compounds 4f, 4j and 4k showed excellent selectivity for FABP5 and would serve as other new lead compounds. Compound 3a possessed high affinity and high selectivity for FABP7. Compounds with moderate to high affinity for FABP5 displayed antinociceptive effects in mice while compounds with low FABP5 affinity lacked in vivo efficacy. In vivo pain model studies in mice revealed that exceeding hydrophobicity significantly affects the efficacy. Thus, among the compounds with high affinity to FABP5 in vitro, the compounds with moderate hydrophobicity were identified as promising new lead compounds for the next round of optimization, including compounds 4b and 4j. For select cases, computational analysis of the observed SAR, especially the selectivity of new inhibitors to particular FABP isoforms, by comparing docking poses, interaction map, and docking energy scores has provided useful insights.

Fatty acid binding proteins (FABPs) are intracellular lipid carriers that regulate inflammation, and pharmacological inhibition of FABP5 reduces inflammation and pain. The mechanism(s) underlying the anti-inflammatory effects associated with FABP5 inhibition are poorly understood. Herein, we identify a novel mechanism through which FABP5 modulates inflammation. In mice, intraplantar injection of carrageenan induces acute inflammation that is accompanied by edema, enhanced pain sensitivity, and elevations in pro-inflammatory cytokines and prostaglandin E2 (PGE2). Inhibition of FABP5 reduced pain, edema, cytokine, and PGE2 levels. PGE2 is a major eicosanoid that enhances pain in the setting of inflammation and we focused upon the mechanism(s) through which FABP5 modulates PGE2 production. Cyclooxygenase-2 and microsomal prostaglandin E synthase-1 (mPGES-1) are enzymes upregulated at the site of inflammation and account for the bulk of PGE2 biosynthesis. Pharmacological or genetic FABP5 inhibition suppressed the induction of mPGES-1 but not COX-2 in carrageenan-injected paws, which occurred predominantly in macrophages.The cytokine interleukin 1β (IL-1β) is a major inducer of mPGES-1 during inflammation. Using A549 cells that express FABP5, IL-1β stimulation upregulated mPGES-1 expression, and mPGES-1 induction was attenuated in A549 cells bearing a knockdown of FABP5. IL-1β upregulates mPGES-1 via NF-kB, which activates the mPGES-1 promoter. Knockdown of FABP5 reduced the activation and nuclear translocation of NF-kB, and attenuated mPGES-1 promoter activity. Deletion of NF-kB binding sites within the mPGES-1 promoter abrogated the ability of FABP5 to inhibit mPGES-1 promoter activation. Collectively, these results position FABP5 as a novel regulator of mPGES-1 induction and PGE2 biosynthesis during inflammation. ________________________________________ Pain is a frequent reason for seeking medical care and approximately thirty percent of older adults experience chronic pain (1-3). Nonsteroidal anti-inflammatory drugs (NSAIDs) and opioids are mainstay treatments for chronic pain. However, chronic NSAID use is associated with gastrointestinal hemorrhage and even acute NSAID use increases the incidence of myocardial FABP5 regulates mPGES-1 during inflammation2 infarctions (4,5). Chronic opioid use is associated with significant addiction and overdose liability (6)(7)(8). Consequently, there is a need to develop novel efficacious non-opioid analgesics.Fatty acid binding proteins (FABPs) are intracellular carriers for fatty acids and related bioactive lipids such as the endocannabinoid anandamide (9-11). In addition to the cytosolic transport of lipids, FABPs deliver ligands to the nucleus wherein they activate nuclear receptors (10,(12)(13)(14). There are ten FABP isoforms expressed in mammals and we previously demonstrated that pharmacological inhibition of FABP5 produces analgesic effects by enhancing endocannabinoid signaling (15)(16)(17)(18). We also demonstrated that FABP5 is expressed in nociceptors, p...