Toward More Selective Antibiotic Inhibitors: A Structural View of the Complexed Binding Pocket of E. coli Peptide Deformylase.

Peptide deformylase (PDF) is involved in bacterial protein maturation processes. Originating from the interest in a new antibiotic, tremendous effort was put into the refinement of PDF inhibitors (PDFIs) and their selectivity. We obtained a full NMR backbone assignment the emergent additional protein backbone resonances of ecPDF 1-147 in complex with 2-(5-bromo-1H-indol-3-yl)-N-hydroxyacetamide (2), a potential new structural scaffold for more selective PDFIs. We also determined the complex crystal structures of E. coli PDF (ecPDF fl) and 2. Our structure suggests an alternative ligand conformation within the protein, a possible starting point for further selectivity optimization. The orientation of the second ligand conformation in the crystal structure points toward a small region of the S1' pocket, which differs between bacterial PDFs and human PDF. Moreover, we analyzed the binding mode of 2 via NMR TITAN line shape analysis, revealing an induced fit mechanism.

The novel FAAH inhibitor, MCH1, reduces the infarction area in the motor cortex-related region but does not affect the sensorimotor function or memory and spatial learning in rats exposed to transient middle cerebral artery occlusion.

Macamides, amides of fatty acids first isolated from maca (Lepidium meyenii) are potentially responsible for the reduction of ischemic injury in the stroke animal model followed by maca extract administration. This deduction comes from its ability to inhibit the fatty acid amide hydrolase activity, an enzyme related to the endocannabinoid anandamide hydrolysis. However, no study about the effects of isolated macamides on in-vivo models has been published yet. Our objective was to evaluate the effect of a 10-day 30 mg/kg i.p. MCH1 administration, the macamide with the higher FAAH inhibition capability, on the neurological recovery and brain infarction area of Sprague-Dawley rats exposed to the transient middle cerebral artery occlusion (MCAO) model. Our results showed that the group receiving MCH1 for 10 days did not improve Garcia's neurological score compared to receiving the vehicle only. Likewise, the MCH1 group did not improve their sensorimotor dysfunction as indicated by the latency to detect and remove the tape from the contralateral forepaw in the adhesive removal test, and a similar number of errors with the contralateral forepaw in the foot fault test compared to the vehicle group at the 10th day. Evaluation of the spatial memory and learning using the Barnes test showed longer latency to reach the escape box in the Vehicle and MCH1 groups compared to the control group (no MCAO) only in the retrieval test, while no effect of MCAO procedure or MCH1 administration was observed in the reversal learning test. Despite the lack of behavioral effect of MCH1, analysis of the infarcted areas in the brain using the 2, 3, 5-Triphenyltetrazolium chloride (TTC) staining method in the seven consecutive coronal sections revealed that the infarcted area in the first (bregma + 4.2 mm) and fifth (bregma -3.8 mm) coronal sections of the MCAO + MCH1 group remained similar to the Control group. These results provide evidence that MCH1 can limit damage from ischemic stroke, although it is not reflected in neurological or sensorimotor behavior and spatial learning and memory.

Inhibiting immunoregulatory amidase NAAA blocks ZIKV maturation in Human Neural Stem Cells.

Recent evidence suggests that lipids play a crucial role in viral infections beyond their traditional functions of supplying envelope and energy, and creating protected niches for viral replication. In the case of Zika virus (ZIKV), it alters host lipids by enhancing lipogenesis and suppressing ß-oxidation to generate viral factories at the endoplasmic reticulum (ER) interface. This discovery prompted us to hypothesize that interference with lipogenesis could serve as a dual antiviral and anti-inflammatory strategy to combat the replication of positive sense single-stranded RNA (ssRNA+) viruses. To test this hypothesis, we examined the impact of inhibiting N-Acylethanolamine acid amidase (NAAA) on ZIKV-infected human Neural Stem Cells. NAAA is responsible for the hydrolysis of palmitoylethanolamide (PEA) in lysosomes and endolysosomes. Inhibition of NAAA results in PEA accumulation, which activates peroxisome proliferator-activated receptor-α (PPAR-α), directing ß-oxidation and preventing inflammation. Our findings indicate that inhibiting NAAA through gene-editing or drugs moderately reduces ZIKV replication by approximately one log10 in Human Neural Stem Cells, while also releasing immature virions that have lost their infectivity. This inhibition impairs furin-mediated prM cleavage, ultimately blocking ZIKV maturation. In summary, our study highlights NAAA as a host target for ZIKV infection.

Synthesis, biological evaluation, and molecular docking studies of aldotetronic acid-based LpxC inhibitors.

In order to develop novel inhibitors of the bacterial deacetylase LpxC bearing a substituent to target the UDP binding site of the enzyme, a series of aldotetronic acid-based hydroxamic acids was accessed in chiral pool syntheses starting from 4,6-O-benzylidene-d-glucose and l-arabinitol. The synthesized hydroxamic acids were tested for LpxC inhibitory activity in vitro, revealing benzyl ether 17a ((2S,3S)-4-(benzyloxy)-N,3-dihydroxy-2-[(4-{[4-(morpholinomethyl)phenyl]ethynyl}benzyl)oxy]butanamide) as the most potent LpxC inhibitor. This compound was additionally tested for antibacterial activity against a panel of clinically relevant Gram-negative bacteria, bacterial uptake, and susceptibility to efflux pumps. Molecular docking studies were performed to rationalize the observed structure-activity relationships.

LpxC (UDP-3-O-(R-3-hydroxymyristoyl)-N-acetylglucosamine deacetylase) inhibitors: A long path explored for potent drug design.

Microbial infections are becoming resistant to traditional antibiotics. As novel resistance mechanisms are developed and disseminated across the world, our ability to treat the most common infectious diseases is becoming increasingly compromised. As existing antibiotics are losing their effectiveness, especially treatment of bacterial infections, is difficult. In order to combat this issue, it is of utmost importance to identify novel pharmacological targets or antibiotics. LpxC, a zinc-dependent metalloamidase that catalyzes the committed step in the biosynthesis of lipid A (endotoxin) in bacteria, is a prime candidate for drug/therapeutic target. So far, the rate-limiting metallo-amidase LpxC has been the most-targeted macromolecule in the Raetz pathway. This is because it is important for the growth of these bacterial infections. This review showcases on the research done to develop efficient drugs in this area before and after the 2015.

Inhibition of FAAH suppresses RANKL-induced osteoclastogenesis and attenuates ovariectomy-induced bone loss partially through repressing the IL17 pathway.

Fatty amide hydrolase (FAAH) is a key degradation enzyme of the endocannabinoid system, mainly responsible for the hydrolysis of arachidonic acid ethanolamine (AEA). Previous investigations have shown that FAAH is involved in a series of biological processes, such as inflammation, immune regulation, and transmembrane signal transduction of neurons. Endogenous cannabinoids and cannabinoid receptors have been reported to participate in the regulation of bone homeostasis by regulating the differentiation of osteoblasts and osteoclasts. We hypothesized that FAAH may play an important role in osteoclastogenesis based on the above evidence. The present study found that the FAAH expression was increased at both mRNA and protein levels during RANKL-induced osteoclastogenesis. Pharmacological and genetic inhibition of FAAH in bone marrow-derived macrophages (BMMs) inhibited osteoclastogenesis, F-actin ring formation, bone resorption, and osteoclast-specific gene expression in vitro. Moreover, intragastric administration of the FAAH inhibitor PF-04457845(PF) ameliorated ovariectomy (OVX)-induced bone loss in mice. Further investigation revealed that nuclear factor κB (NF-κB) and mitogen-activated protein kinase (MAPK) pathways were inhibited by PF treatment and FAAH knockdown. RNAseq indicated that the IL17 pathway was blocked by PF, and administration of recombinant murine IL17 protein could partially restore osteoclastogenesis and activate NF-κB and MAPK pathways. To sum up, our findings demonstrate that targeting FAAH could be a promising candidate strategy for treating osteoclast-related diseases, especially osteoporosis.

FAAH Inhibition Restores Early Life Stress-Induced Alterations in PFC microRNAs Associated with Depressive-Like Behavior in Male and Female Rats.

Early life stress (ELS) increases predisposition to depression. We compared the effects of treatment with the fatty acid amide hydrolase (FAAH) inhibitor URB597, and the selective serotonin reuptake inhibitor paroxetine, on ELS-induced depressive-like behavior and the expression of microRNAs (miRs) associated with depression in the medial prefrontal cortex (mPFC), hippocampal CA1 area, lateral habenula and dorsal raphe in rats. We also examined the mRNA expression of serotonergic (htr1a and slc6a4) and endocannabinoid (cnr1, cnr2 and faah) targets in the mPFC following ELS and pharmacological treatment. Adult males and females exposed to the 'Limited Bedding and Nesting' ELS paradigm demonstrated a depressive-like phenotype and late-adolescence URB597 treatment, but not paroxetine, reversed this phenotype. In the mPFC, ELS downregulated miR-16 in males and miR-135a in females and URB597 treatment restored this effect. In ELS females, the increase in cnr2 and decrease in faah mRNAs in the mPFC were reversed by URB597 treatment. We show for the first time that URB597 reversed ELS-induced mPFC downregulation in specific miRs and stress-related behaviors, suggesting a novel mechanism for the beneficial effects of FAAH inhibition. The differential effects of ELS and URB597 on males and females highlight the importance of developing sex-specific treatment approaches.

Lanostane triterpenoids from Ganoderma lucidum and their inhibitory effects against FAAH.

Ganoderma lucidum is a famous edible and medicinal fungus. Through a bioactive phytochemical investigation of the ethanolic extracts of the fruiting bodies of G. lucidum, twenty-nine triterpenoids, including eleven previously undescribed triterpenoids, were isolated and characterized based on spectroscopic data. The inhibitory effects of all the triterpenes against fatty acid amide hydrolase (FAAH) were found to be in the range of 30-60% at 100 µM. Methyl ganoderate A displayed the strongest inhibitory activity (61%) against FAAH. Furthermore, all compounds displayed no cytotoxicity against LOVO and MCF-7 human cancer cells. Hence, our present study provides information about G. lucidum as a functional food or pharmaceutical supplement for the treatment of neuroinflammation.

The multitarget FAAH inhibitor/D3 partial agonist ARN15381 decreases nicotine self-administration in male rats.

Tobacco use disorder is a worldwide health problem for which available medications show limited efficacy. Nicotine is the psychoactive component of tobacco responsible for its addictive liability. Similar to other addictive drugs, nicotine enhances mesolimbic dopamine transmission. Inhibition of the fatty acid amide hydrolase (FAAH), the enzyme responsible for the degradation of the endocannabinoid anandamide (AEA), palmitoylethanolamide (PEA) and oleoylethanolamide (OEA), reduces nicotine-enhanced dopamine transmission and acquisition of nicotine self-administration in rats. Down-regulation of dopamine transmission by antagonists or partial agonists of the dopamine D3 receptor (DRD3) also reduced nicotine self-administration and conditioned place preference. Based on these premises, we evaluated the effect of ARN15381, a multitarget compound showing FAAH inhibition and DRD3 partial agonist activity in the low nanomolar range, on nicotine self-administration in rats. Pretreatment with ARN15381 dose dependently decreased self-administration of a nicotine dose at the top of the nicotine dose/response (D/R) curve, while it did not affect self-administration of a nicotine dose laying on the descending limb of the D/R curve. Conversely, pretreatment with the selective FAAH inhibitor URB597 and the DRD3 partial agonist CJB090 failed to modify nicotine self-administration independent of the nicotine dose self-administered. Our data indicates that the concomitant FAAH inhibition and DRD3 partial agonism produced by ARN15381 is key to the observed reduction of nicotine self-administration, demonstrating that a multitarget approach may hold clinical importance for the treatment of tobacco use disorder.

Discovery and characterization of amentoflavone as a naturally occurring inhibitor against the bile salt hydrolase produced by Lactobacillus salivarius.

Bile salt hydrolases (BSHs), a group of cysteine-hydrolases produced by gut microbes, play a crucial role in the hydrolysis of glycine- or taurine-conjugated bile acids and have been validated as key targets to modulate bile acid metabolism. This study aims to discover one or more efficacious inhibitors against a BSH produced by Lactobacillus salivarius (lsBSH) from natural products and to characterize the mechanism of the newly identified BSH inhibitor(s). Following screening of the inhibition potentials of more than 100 natural compounds against lsBSH, amentoflavone (AMF), a naturally occurring biflavone isolated from various medicinal plants, was discovered to be an efficacious BSH inhibitor (IC50 = 0.34 µM). Further investigation showed that AMF could strongly inhibit the lsBSH-catalyzed hydrolytic reaction in living gut microbes. Inhibition kinetic analyses demonstrated that AMF reversibly inhibited the lsBSH-catalyzed hydrolytic reaction in a mixed-inhibition manner, with an apparent Ki value of 0.65 µM. Fluorescence quenching assays suggested that AMF could quench the fluorescence of lsBSH via a static quenching procedure. Docking simulations suggested that AMF could be fitted into lsBSH at two distinct ligand-binding sites, mainly via hydrophobic interactions and hydrogen bonding, which explained well the mixed inhibition mode of this agent. Animal tests showed that the hydrolytic activities of BSHs in mice feces could be significantly blocked by AMF. In summary, this study reports that AMF is a strong, naturally occurring inhibitor of lsBSH, which offers a promising lead compound to develop novel agents for modulating bile acid metabolism in the host via targeting BSHs.

A New Series of Aryloxyacetic Acids Endowed with Multi-Target Activity towards Peroxisome Proliferator-Activated Receptors (PPARs), Fatty Acid Amide Hydrolase (FAAH), and Acetylcholinesterase (AChE).

A new series of aryloxyacetic acids was prepared and tested as peroxisome proliferator-activated receptors (PPARs) agonists and fatty acid amide hydrolase (FAAH) inhibitors. Some compounds exhibited an interesting dual activity that has been recently proposed as a new potential therapeutic strategy for the treatment of Alzheimer's disease (AD). AD is a multifactorial pathology, hence multi-target agents are currently one of the main lines of research for the therapy and prevention of this disease. Given that cholinesterases represent one of the most common targets of recent research, we decided to also evaluate the effects of our compounds on the inhibition of these specific enzymes. Interestingly, two of these compounds, (S)-5 and 6, showed moderate activity against acetylcholinesterase (AChE) and even some activity, although at high concentration, against Aß peptide aggregation, thus demonstrating, in agreement with the preliminary dockings carried out on the different targets, the feasibility of a simultaneous multi-target activity towards PPARs, FAAH, and AChE. As far as we know, these are the first examples of molecules endowed with this pharmacological profile that might represent a promising line of research for the identification of novel candidates for the treatment of AD.

Pharmacokinetic Characterization of the DDAH1 Inhibitors ZST316 and ZST152 in Mice Using a HPLC-MS/MS Method.

The pharmacokinetic profile of ZST316 and ZST152, arginine analogues with inhibitory activity towards human dimethylarginine dimethylaminohydrolase-1 (DDAH1), was investigated in mice using a newly developed HPLC-MS/MS method. The method proved to be reproducible, precise, and accurate for the measurement of the compounds in plasma and urine. Four-week-old female FVB mice received a single dose of ZST316 and ZST152 by intravenous bolus (30 mg/Kg) and oral gavage (60 mg/Kg). ZST316 Cmax was 67.4 µg/mL (intravenous) and 1.02 µg/mL (oral), with a half-life of 6 h and bioavailability of 4.7%. ZST152 Cmax was 24.9 µg/mL (intravenous) and 1.65 µg/mL (oral), with a half-life of 1.2 h and bioavailability of 33.3%. Urinary excretion of ZST152 and ZST316 was 12.5%-22.2% and 2.3%-7.5%, respectively. At least eight urinary metabolites were identified. After chronic intraperitoneal treatment with the more potent DDAH1 inhibitor, ZST316 (30 mg/Kg/day for three weeks), the bioavailability was 59% and no accumulation was observed. Treatment was well tolerated with no changes in body weight vs. untreated animals and no clinical signs of toxicity or distress. The results of this study show that ZST316 has a favorable pharmacokinetic profile, following intraperitoneal administration, to investigate the effects of DDAH1 inhibition in mice.

Discovery of a Series of Pyrimidine Carboxamides as Inhibitors of Vanin-1.

A diaryl ketone series was identified as vanin-1 inhibitors from a high-throughput screening campaign. While this novel scaffold provided valuable probe 2 that was used to build target confidence, concerns over the ketone moiety led to the replacement of this group. The successful replacement of this moiety was achieved with pyrimidine carboxamides derived from cyclic secondary amines that were extensively characterized using biophysical and crystallographic methods as competitive inhibitors of vanin-1. Through optimization of potency and physicochemical and ADME properties, and guided by co-crystal structures with vanin-1, 3 was identified with a suitable profile for advancement into preclinical development.

Role of PI3K/Akt axis in mitigating hippocampal ischemia-reperfusion injury via CB1 receptor stimulation by paracetamol and FAAH inhibitor in rat.

AIMS: Acetaminophen or paracetamol (PAR), the recommended antipyretic in COVID-19 and clinically used to alleviate stroke-associated hyperthermia interestingly activates cannabinoid receptor (CB1) through its AM404 metabolite, however, to date, no study reports the in vivo activation of PAR/AM404/CB1 axis in stroke. The current study deciphers the neuroprotective effect off PAR in cerebral ischemia/reperfusion (IR) rat model and unmasks its link with AM404/CB1/PI3K/Akt axis. MATERIALS AND METHODS: Animals were allocated into 5 groups: (I) sham-operated (SO), (II) IR, (III) IR + PAR (100 mg/kg), (IV) IR + PAR (100 mg/kg) + URB597; anandamide degradation inhibitor (0.3 mg/kg) and (V) IR + PAR (100 mg/kg) + AM4113; CB1 Blocker (5 mg/kg). All drugs were intraperitoneally administered at the inception of the reperfusion period. KEY FINDINGS: PAR administration alleviated the cognitive impairment in the Morris Water Maze as well as hippocampal histopathological and immunohistochemical examination of GFAP. The PAR signaling was associated with elevation of anandamide level, CB1 receptor expression and survival proteins as pS473-Akt. P(tyr202/thr204)-ERK1/2 and pS9-GSK3ß. Simultaneously, PAR increased hippocampal BDNF and ß-arrestin1 levels and decreased glutamate level. PAR restores the deranged redox milieu induced by IR Injury, by reducing lipid peroxides, myeloperoxidase activity and NF-κB and increasing NPSH, total antioxidant capacity, nitric oxide and Nrf2 levels. The pre-administration of AM4113 reversed PAR effects, while URB597 potentiated them. SIGNIFICANCE: PAR poses a significant neuroprotective effect which may be mediated, at least in part, via activation of anandamide/CB1/PI3K/Akt pathway in the IR rat model.

TP0586532, a non-hydroxamate LpxC inhibitor, has in vitro and in vivo antibacterial activities against Enterobacteriaceae.

The emergence of multi-drug resistant pathogenic bacteria, especially Gram-negative bacteria, is a worldwide health problem. New antibiotics directed at previously unexplored targets are urgently needed to overcome resistance to existing antibiotic classes. UDP-3-O-acyl-N-acetylglucosamine deacetylase (LpxC) is an attractive target for a new antibacterial agent. Although a number of LpxC inhibitors have been identified, none have been approved as antibacterial agents. These LpxC inhibitors contain a hydroxamate moiety, which is a robust zinc ion chelator. The nonspecific inhibition of metalloenzymes through zinc ion chelation is one of possibilities leading to unwanted side effects. Herein, we report that TP0586532, a non-hydroxamate LpxC inhibitor, has a broad spectrum of antibacterial activity against carbapenem-resistant Enterobacteriaceae. The MIC90 of TP0586532 against clinical isolates of carbapenem-resistant Klebsiella pneumoniae was 4 µg ml-1. TP0586532 also showed an in vivo efficacy against murine systemic, urinary tract and lung infection models caused by meropenem- or ciprofloxacin-resistant strains. The estimated maximum unbound plasma concentration value at the effective dose of TP0586532 in murine infection models was around 13 µg ml-1. TP0586532 is predicted to exhibit a in vivo efficacy without cardiovascular toxicity and showed the potential of non-hydroxamate LpxC inhibitors as antibacterial agents against carbapenem-resistant Enterobacteriaceae.

Effects of Fatty Acid Amide Hydroxylase Inhibitor URB597 on the Catecholaminergic Activity of the Adrenal Medulla in Stressed Male and Female Rats.

INTRODUCTION: The present study examined the effects of fatty acid amide hydrolase inhibitor URB597 on the level of plasma catecholamine and their content, synthesis, and degradation in the adrenal medulla of male and female rats subjected to chronic unpredictable stress (CUS). MATERIAL AND METHODS: Male and female Wistar rats were exposed to the 6 weeks of CUS and treated intraperitoneally with either 0.3 mg/kg/day of URB597 or vehicle in the last 2 weeks of stress protocol. Catecholamines' plasma levels and catecholamines' levels in adrenal medulla were examined using Elabscience ELISA kits. Western blot analysis was used to detect the protein in the medulla. RESULTS: The results of our experiment showed that adrenal weights and catecholamine of unstressed control were higher in females and that CUS induced further enlargement of adrenal glands and catecholamine content and its synthesis compared to male rats. CUS caused an increase of plasma norepinephrine and depletion of norepinephrine content as well as unchanged synthesis and degradation of catecholamine in the adrenal medulla of male rats. URB597 reduced enlarged adrenals and catecholamine content and its synthesis in stressed female rats. URB597 reduces increased plasma norepinephrine and restores its content in the adrenal medulla, unchanging the expression of enzyme synthesis, while reduced protein levels of monoamine oxidase A in male rats are exposed to CUS. DISCUSSION: Our results support the role of endocannabinoids as an antistress mechanism that inhibits elevated adrenomedullary activation and promotes its recovery to baseline in both male and female stressed rats.

Sex specific effects of the fatty acid amide hydrolase inhibitor URB597 on memory and brain ß2-adrenergic and D1-dopamine receptors.

An increasing body of evidence shows significant sex differences in the mammalian brain in multiple behaviours and psychiatric and neurological diseases and as well as that the endocannabinoid system may differ between males and females. In this study we investigated sex differences in working, short-term and long-term memory and the expression of ß2-adrenergic and D1- and D2-receptors in the mPFC and hippocampus, brain regions that are involved in stress response and memory modulation in rats exposed to the chronic unpredictable stress (CUS) and the potential beneficial effects of the chronic fatty acid amide hydrolase inhibitor URB597 treatment. Chronically stressed male rats had an improvement of working memory, while stressed females showed very low object-recognition abilities. On the other hand, animals of both sexes exhibited long-term memory impairment. Our results showed that CUS decreased the expression of ß2-adrenoceptors in the mPFC and D1 receptors in the mPFC and hippocampus of male rats and decreased ß2-adrenoceptors and D1- receptors in the hippocampus of female. URB597 treatment had a positive effect on the short-term memory of stressed animals of both sexes whereas failed to restore long-term memory and did not affect the protein levels ß2-adrenoceptors and D1 receptors in the hippocampus of CUS female rats. The present results support that endocannabinoids induced long-term memory and neurochemical alternations which are sex dependent, suggesting sex specific treatment strategies of mental disorders.

The effects of systemic and local fatty acid amide hydrolase and monoacylglycerol lipase inhibitor treatments on the metabolomic profile of lungs.

The contribution of the endocannabinoid system to both physiology and pathological processes in the respiratory system makes it a promising target for inflammatory airway diseases. Previously, we have shown that increasing the tissue endocannabinoid levels by fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL) inhibitors can prevent airway inflammation and hyperreactivity. In this study, the changes in the levels of major metabolites of endocannabinoids by systemic and local FAAH or MAGL inhibitor treatments were evaluated. Mice were treated with either the FAAH inhibitor URB597 or the MAGL inhibitor JZL184 by local (intranasal) or systemic (intraperitoneal) application. Bronchoalveolar lavage (BAL) fluids and lungs were isolated afterward in order to perform histopathological and metabolomic analyses. There were no significant histopathological changes in the lungs and neutrophil, and macrophage and lymphocyte numbers in BAL fluid were not altered after local and systemic treatments. However, GC-MS-based metabolomics profile allowed us to identify 102 metabolites in lung samples, among which levels of 75 metabolites were significantly different from the control. The metabolites whose levels were changed by treatments were mostly related to the endocannabinoid system and energy metabolism. Therefore, these changes may contribute to the anti-inflammatory effects of URB597 and JZL184 treatments in mice.

Safety, Tolerability, and Pharmacokinetics of FAAH Inhibitor BIA 10-2474: A Double-Blind, Randomized, Placebo-Controlled Study in Healthy Volunteers.

This study evaluated the safety, tolerability, pharmacokinetics, and pharmacodynamics of BIA 10-2474, a fatty acid amide hydrolase (FAAH) inhibitor, after first administration to healthy male and female participants. Participants (n = 116) were recruited into this phase I, double-blind, randomized, placebo-controlled, single ascending dose and multiple ascending dose (10-day) study. The primary outcome was the safety and tolerability of BIA 10-2474. Secondary outcomes were pharmacokinetics of BIA 10-2474 and pharmacodynamics, considering plasma concentrations of anandamide and three other fatty acid amides (FAAs) and leukocyte FAAH activity. Single oral doses of 0.25-100 mg and repeated oral doses of 2.5-50 mg were evaluated. BIA 10-2474 was well tolerated up to 100 mg as a single dose and up to 20 mg once daily for 10 days. In the cohort receiving repeated administrations of 50 mg, there were central nervous system adverse events in five of six participants, one with fatal outcome, which led to early termination of the study. BIA 10-2474 showed a linear relationship between dose and area under plasma concentration-time curve (AUC) across the entire dose range and reached steady state within 5-6 days of administration, with an accumulation ratio, based on AUC0-24h , of <2 on Day 10. BIA 10-2474 was rapidly absorbed with a mean terminal elimination half-life of 8-10 hours (Day 10). BIA 10-2474 caused reversible, dose-related increases in plasma FAAs. In conclusion, we propose that these data, as well as the additional data generated since the clinical trial was stopped, do not provide a complete mechanistic explanation for the tragic fatality.

TRPV1 blockers as potential new treatments for psychiatric disorders.

The transient receptor potential vanilloid-1 channel (TRPV1) is responsible for decoding physical and chemical stimuli. TRPV1 is activated by capsaicin (a compound from chili peppers), heat (above 43°C) and acid environment, playing a major role in pain, inflammation and body temperature. Molecular and histological studies have suggested TRPV1 expression in specific brain regions, where it can be activated primarily by the endocannabinoid anandamide, fostering studies on its potential role in psychiatric disorders. TRPV1 blockers are effective in various animal models predictive of anxiolytic and antipanic activities, in addition to reducing conditioned fear. In models of antidepressant activity, these compounds reduce behavioral despair and promote active stress-coping behavior. TRPV1 blockers also reduce the effects of certain drugs of abuse and revert behavioral changes in animal models of neurodevelopmental disorders. The main limiting factor in developing TRPV1 blockers as therapeutic agents concerns their effects on body temperature, particularly hyperthermia. New compounds, which block specific states of the channel, could represent an alternative. Moreover, compounds blocking both TRPV1 and the anandamide-hydrolyzing enzyme, fatty acid amide hydrolase (FAAH), termed dual TRPV1/FAAH blockers, have been investigated with promising results. Overall, preclinical studies yield favorable results with TRPV1 blockers in animal models of psychiatric disorders.