Combined in vivo effect of N-acylethanolamine-hydrolyzing acid amidase and glycogen synthase kinase-3ß inhibition to treat multiple sclerosis.

The current pharmacological approaches to multiple sclerosis (MS) target its inflammatory and autoimmune components, but effective treatments to foster remyelination and axonal repair are still lacking. We therefore selected two targets known to be involved in MS pathogenesis: N-acylethanolamine-hydrolyzing acid amidase (NAAA) and glycogen synthase kinase-3ß (GSK-3ß). We tested whether inhibiting these targets exerted a therapeutic effect against experimental autoimmune encephalomyelitis (EAE), an animal model of MS. The combined inhibition of NAAA and GSK-3ß by two selected small-molecule compounds, ARN16186 (an NAAA inhibitor) and AF3581 (a GSK-3ß inhibitor), effectively mitigated disease progression, rescuing the animals from paralysis and preventing a worsening of the pathology. The complementary activity of the two inhibitors reduced the infiltration of immune cells into the spinal cord and led to the formation of thin myelin sheaths around the axons post-demyelination. Specifically, the inhibition of NAAA and GSK-3ß modulated the over-activation of NF-kB and STAT3 transcription factors in the EAE-affected mice and induced the nuclear translocation of ß-catenin, reducing the inflammatory insult and promoting the remyelination process. Overall, this work demonstrates that the dual-targeting of key aspects responsible for MS progression could be an innovative pharmacological approach to tackle the pathology.

Pharmacological potentiators of the calcium signaling cascade identified by high-throughput screening.

Pharmacological modulators of the Ca2+ signaling cascade are important research tools and may translate into novel therapeutic strategies for a series of human diseases. We carried out a screening of a maximally diverse chemical library using the Ca2+-sensitive Cl- channel TMEM16A as a functional readout. We found compounds that were able to potentiate UTP-dependent TMEM16A activation. Mechanism of action of these compounds was investigated by a panel of assays that looked at intracellular Ca2+ mobilization triggered by extracellular agonists or by caged-IP3 photolysis, PIP2 breakdown by phospholipase C, and ion channel activity on nuclear membrane. One compound appears as a selective potentiator of inositol triphosphate receptor type 1 (ITPR1) with a possible application for some forms of spinocerebellar ataxia. A second compound is instead a potentiator of the P2RY2 purinergic receptor, an activity that could promote fluid secretion in dry eye and chronic obstructive respiratory diseases.

Discovery and SAR Evolution of Pyrazole Azabicyclo[3.2.1]octane Sulfonamides as a Novel Class of Non-Covalent N-Acylethanolamine-Hydrolyzing Acid Amidase (NAAA) Inhibitors for Oral Administration.

Inhibition of intracellular N-acylethanolamine-hydrolyzing acid amidase (NAAA) activity is a promising approach to manage the inflammatory response under disabling conditions. In fact, NAAA inhibition preserves endogenous palmitoylethanolamide (PEA) from degradation, thus increasing and prolonging its anti-inflammatory and analgesic efficacy at the inflamed site. In the present work, we report the identification of a potent, systemically available, novel class of NAAA inhibitors, featuring a pyrazole azabicyclo[3.2.1]octane structural core. After an initial screening campaign, a careful structure-activity relationship study led to the discovery of endo-ethoxymethyl-pyrazinyloxy-8-azabicyclo[3.2.1]octane-pyrazole sulfonamide 50 (ARN19689), which was found to inhibit human NAAA in the low nanomolar range (IC50 = 0.042 µM) with a non-covalent mechanism of action. In light of its favorable biochemical, in vitro and in vivo drug-like profile, sulfonamide 50 could be regarded as a promising pharmacological tool to be further investigated in the field of inflammatory conditions.

Inhibition of N-acylethanolamine-hydrolyzing acid amidase reduces T cell infiltration in a mouse model of multiple sclerosis.

Experimental autoimmune encephalomyelitis (EAE) is an animal model of multiple sclerosis (MS), in which myeloid cells sustain inflammation, take part in priming, differentiation, and reactivation of myelin-specific T cells, and cause direct myelin damage. N-Acylethanolamine-hydrolyzing acid amidase (NAAA) is a proinflammatory enzyme induced by phlogosis and overexpressed in macrophages and microglia of EAE mice. Targeting these cell populations by inhibiting NAAA may be a promising pharmacological strategy to modulate the inflammatory aspect of MS and manage disease progression. To address this goal, we used ARN16186, a small molecule specifically designed and synthesized as a pharmacological tool to inhibit NAAA. We assessed whether enzyme inhibition affected the severity of neurological symptoms and modulated immune cell infiltration into the central nervous system of EAE mice. We found that preventive chronic treatment with ARN16186 was efficacious in slowing disease progression and preserving locomotor activity in EAE mice. Furthermore, NAAA inhibition reduced the number of immune cells infiltrating the spinal cord and modulated the overactivation of NF-kB and STAT3 transcription factors, leading to less expansion of Th17 cells over the course of the disease.

Partial Rescue of F508del-CFTR Stability and Trafficking Defects by Double Corrector Treatment.

Deletion of phenylalanine at position 508 (F508del) in the CFTR chloride channel is the most frequent mutation in cystic fibrosis (CF) patients. F508del impairs the stability and folding of the CFTR protein, thus resulting in mistrafficking and premature degradation. F508del-CFTR defects can be overcome with small molecules termed correctors. We investigated the efficacy and properties of VX-445, a newly developed corrector, which is one of the three active principles present in a drug (Trikafta®/Kaftrio®) recently approved for the treatment of CF patients with F508del mutation. We found that VX-445, particularly in combination with type I (VX-809, VX-661) and type II (corr-4a) correctors, elicits a large rescue of F508del-CFTR function. In particular, in primary bronchial epithelial cells of CF patients, the maximal rescue obtained with corrector combinations including VX-445 was close to 60-70% of CFTR function in non-CF cells. Despite this high efficacy, analysis of ubiquitylation, resistance to thermoaggregation, protein half-life, and subcellular localization revealed that corrector combinations did not fully normalize F508del-CFTR behavior. Our study indicates that it is still possible to further improve mutant CFTR rescue with the development of corrector combinations having maximal effects on mutant CFTR structural and functional properties.

Identification, Structure-Activity Relationship, and Biological Characterization of 2,3,4,5-Tetrahydro-1H-pyrido[4,3-b]indoles as a Novel Class of CFTR Potentiators.

Cystic fibrosis (CF) is a life-threatening autosomal recessive disease, caused by mutations in the CF transmembrane conductance regulator (CFTR) chloride channel. CFTR modulators have been reported to address the basic defects associated with CF-causing mutations, partially restoring the CFTR function in terms of protein processing and/or channel gating. Small-molecule compounds, called potentiators, are known to ameliorate the gating defect. In this study, we describe the identification of the 2,3,4,5-tetrahydro-1H-pyrido[4,3-b]indole core as a novel chemotype of potentiators. In-depth structure-activity relationship studies led to the discovery of enantiomerically pure 39 endowed with a good efficacy in rescuing the gating defect of F508del- and G551D-CFTR and a promising in vitro druglike profile. The in vivo characterization of γ-carboline 39 showed considerable exposure levels and good oral bioavailability, with detectable distribution to the lungs after oral administration to rats. Overall, these findings may represent an encouraging starting point to further expand this chemical class, adding a new chemotype to the existing classes of CFTR potentiators.

Discovery of a picomolar potency pharmacological corrector of the mutant CFTR chloride channel.

F508del, the most frequent mutation causing cystic fibrosis (CF), results in mistrafficking and premature degradation of the CFTR chloride channel. Small molecules named correctors may rescue F508del-CFTR and therefore represent promising drugs to target the basic defect in CF. We screened a carefully designed chemical library to find F508del-CFTR correctors. The initial active compound resulting from the primary screening underwent extensive chemical optimization. The final compound, ARN23765, showed an extremely high potency in bronchial epithelial cells from F508del homozygous patients, with an EC50 of 38 picomolar, which is more than 5000-fold lower compared to presently available corrector drugs. ARN23765 also showed high efficacy, synergy with other types of correctors, and compatibility with chronic VX-770 potentiator. Besides being a promising drug, particularly suited for drug combinations, ARN23765 represents a high-affinity probe for CFTR structure-function studies.

Identification of a 2,4-diaminopyrimidine scaffold targeting Trypanosoma brucei pteridine reductase 1 from the LIBRA compound library screening campaign.

The LIBRA compound library is a collection of 522 non-commercial molecules contributed by various Italian academic laboratories. These compounds have been designed and synthesized during different medicinal chemistry programs and are hosted by the Italian Institute of Technology. We report the screening of the LIBRA compound library against Trypanosoma brucei and Leishmania major pteridine reductase 1, TbPTR1 and LmPTR1. Nine compounds were active against parasitic PTR1 and were selected for cell-based parasite screening, as single agents and in combination with methotrexate (MTX). The most interesting TbPTR1 inhibitor identified was 4-(benzyloxy)pyrimidine-2,6-diamine (LIB_66). Subsequently, six new LIB_66 derivatives were synthesized to explore its Structure-Activity-Relationship (SAR) and absorption, distribution, metabolism, excretion and toxicity (ADMET) properties. The results indicate that PTR1 has a preference to bind inhibitors, which resemble its biopterin/folic acid substrates, such as the 2,4-diaminopyrimidine derivatives.

A European regulatory perspective on cystic fibrosis: current treatments, trends in drug development and translational challenges for CFTR modulators.

In this article we analyse the current authorised treatments and trends in early drug development for cystic fibrosis (CF) in the European Union for the time period 2000-2016. The analysis indicates a significant improvement in the innovation and development of new potential medicines for CF, shifting from products that act on the symptoms of the disease towards new therapies targeting the cause of CF. However, within these new innovative medicines, results for CF transmembrane conductance regulator (CFTR) modulators indicate that one major challenge for turning a CF concept product into an actual medicine for the benefit of patients resides in the fact that, although pre-clinical models have shown good predictability for certain mutations, a good correlation to clinical end-points or biomarkers (e.g. forced expiratory volume in 1 s and sweat chloride) for all mutations has not yet been achieved. In this respect, the use of alternative end-points and innovative nonclinical models could be helpful for the understanding of those translational discrepancies. Collaborative endeavours to promote further research and development in these areas as well as early dialogue with the regulatory bodies available at the European competent authorities are recommended.

Potent α-amino-ß-lactam carbamic acid ester as NAAA inhibitors. Synthesis and structure-activity relationship (SAR) studies.

4-Cyclohexylbutyl-N-[(S)-2-oxoazetidin-3-yl]carbamate (3b) is a potent, selective and systemically active inhibitor of intracellular NAAA activity, which produces profound anti-inflammatory effects in animal models. In the present work, we describe structure-activity relationship (SAR) studies on 3-aminoazetidin-2-one derivatives, which have led to the identification of 3b, and expand these studies to elucidate the principal structural and stereochemical features needed to achieve effective NAAA inhibition. Investigations on the influence of the substitution at the ß-position of the 2-oxo-3-azetidinyl ring as well as on the effect of size and shape of the carbamic acid ester side chain led to the discovery of 3ak, a novel inhibitor of human NAAA that shows an improved physicochemical and drug-like profile relative to 3b. This favourable profile, along with the structural diversity of the carbamic acid chain of 3b, identify this compound as a promising new tool to investigate the potential of NAAA inhibitors as therapeutic agents for the treatment of pain and inflammation.

Activity-Based Probe for N-Acylethanolamine Acid Amidase.

N-Acylethanolamine acid amidase (NAAA) is a lysosomal cysteine hydrolase involved in the degradation of saturated and monounsaturated fatty acid ethanolamides (FAEs), a family of endogenous lipid signaling molecules that includes oleoylethanolamide (OEA) and palmitoylethanolamide (PEA). Among the reported NAAA inhibitors, α-amino-ß-lactone (3-aminooxetan-2-one) derivatives have been shown to prevent FAE hydrolysis in innate-immune and neural cells and to reduce reactions to inflammatory stimuli. Recently, we disclosed two potent and selective NAAA inhibitors, the compounds ARN077 (5-phenylpentyl-N-[(2S,3R)-2-methyl-4-oxo-oxetan-3-yl]carbamate) and ARN726 (4-cyclohexylbutyl-N-[(S)-2-oxoazetidin-3-yl]carbamate). The former is active in vivo by topical administration in rodent models of hyperalgesia and allodynia, while the latter exerts systemic anti-inflammatory effects in mouse models of lung inflammation. In the present study, we designed and validated a derivative of ARN726 as the first activity-based protein profiling (ABPP) probe for the in vivo detection of NAAA. The newly synthesized molecule 1 is an effective in vitro and in vivo click-chemistry activity based probe (ABP), which is able to capture the catalytically active form of NAAA in Human Embryonic Kidney 293 (HEK293) cells overexpressing human NAAA as well as in rat lung tissue. Competitive ABPP with 1 confirmed that ARN726 and ARN077 inhibit NAAA in vitro and in vivo. Compound 1 is a useful new tool to identify activated NAAA both in vitro and in vivo and to investigate the physiological and pathological roles of this enzyme.

A Potent Systemically Active N-Acylethanolamine Acid Amidase Inhibitor that Suppresses Inflammation and Human Macrophage Activation.

Fatty acid ethanolamides such as palmitoylethanolamide (PEA) and oleoylethanolamide (OEA) are lipid-derived mediators that potently inhibit pain and inflammation by ligating type-α peroxisome proliferator-activated receptors (PPAR-α). These bioactive substances are preferentially degraded by the cysteine hydrolase, N-acylethanolamine acid amidase (NAAA), which is highly expressed in macrophages. Here, we describe a new class of ß-lactam derivatives that are potent, selective, and systemically active inhibitors of intracellular NAAA activity. The prototype of this class deactivates NAAA by covalently binding the enzyme's catalytic cysteine and exerts profound anti-inflammatory effects in both mouse models and human macrophages. This agent may be used to probe the functions of NAAA in health and disease and as a starting point to discover better anti-inflammatory drugs.

Synthesis, biological evaluation, and 3D QSAR study of 2-methyl-4-oxo-3-oxetanylcarbamic acid esters as N-acylethanolamine acid amidase (NAAA) inhibitors.

N-(2-Oxo-3-oxetanyl)carbamic acid esters have recently been reported to be noncompetitive inhibitors of the N-acylethanolamine acid amidase (NAAA) potentially useful for the treatment of pain and inflammation. In the present study, we further explored the structure-activity relationships of the carbamic acid ester side chain of 2-methyl-4-oxo-3-oxetanylcarbamic acid ester derivatives. Additional favorable features in the design of potent NAAA inhibitors have been found together with the identification of a single digit nanomolar inhibitor. In addition, we devised a 3D QSAR using the atomic property field method. The model turned out to be able to account for the structural variability and was prospectively validated by designing, synthesizing, and testing novel inhibitors. The fairly good agreement between predictions and experimental potency values points to this 3D QSAR model as the first example of quantitative structure-activity relationships in the field of NAAA inhibitors.

3-Aminoazetidin-2-one derivatives as N-acylethanolamine acid amidase (NAAA) inhibitors suitable for systemic administration.

N-Acylethanolamine acid amidase (NAAA) is a cysteine hydrolase that catalyzes the hydrolysis of endogenous lipid mediators such as palmitoylethanolamide (PEA). PEA has been shown to exert anti-inflammatory and antinociceptive effects in animals by engaging peroxisome proliferator-activated receptor α (PPAR-α). Thus, preventing PEA degradation by inhibiting NAAA may provide a novel approach for the treatment of pain and inflammatory states. Recently, 3-aminooxetan-2-one compounds were identified as a class of highly potent NAAA inhibitors. The utility of these compounds is limited, however, by their low chemical and plasma stabilities. In the present study, we synthesized and tested a series of N-(2-oxoazetidin-3-yl)amides as a novel class of NAAA inhibitors with good potency and improved physicochemical properties, suitable for systemic administration. Moreover, we elucidated the main structural features of 3-aminoazetidin-2-one derivatives that are critical for NAAA inhibition.

Synthesis, structure-activity, and structure-stability relationships of 2-substituted-N-(4-oxo-3-oxetanyl) N-acylethanolamine acid amidase (NAAA) inhibitors.

N-Acylethanolamine acid amidase (NAAA) is a cysteine amidase that preferentially hydrolyzes saturated or monounsaturated fatty acid ethanolamides (FAEs), such as palmitoylethanolamide (PEA) and oleoylethanolamide (OEA), which are endogenous agonists of nuclear peroxisome proliferator-activated receptor-α (PPAR-α). Compounds that feature an α-amino-ß-lactone ring have been identified as potent and selective NAAA inhibitors and have been shown to exert marked anti-inflammatory effects that are mediated through FAE-dependent activation of PPAR-α. We synthesized and tested a series of racemic, diastereomerically pure ß-substituted α-amino-ß-lactones, as either carbamate or amide derivatives, investigating the structure-activity and structure-stability relationships (SAR and SSR) following changes in ß-substituent size, relative stereochemistry at the α- and ß-positions, and α-amino functionality. Substituted carbamate derivatives emerged as more active and stable than amide analogues, with the cis configuration being generally preferred for stability. Increased steric bulk at the ß-position negatively affected NAAA inhibitory potency, while improving both chemical and plasma stability.

Synthesis and structure-activity relationship (SAR) of 2-methyl-4-oxo-3-oxetanylcarbamic acid esters, a class of potent N-acylethanolamine acid amidase (NAAA) inhibitors.

N-Acylethanolamine acid amidase (NAAA) is a lysosomal cysteine hydrolase involved in the degradation of saturated and monounsaturated fatty acid ethanolamides (FAEs), a family of endogenous lipid agonists of peroxisome proliferator-activated receptor-α, which include oleoylethanolamide (OEA) and palmitoylethanolamide (PEA). The ß-lactone derivatives (S)-N-(2-oxo-3-oxetanyl)-3-phenylpropionamide (2) and (S)-N-(2-oxo-3-oxetanyl)-biphenyl-4-carboxamide (3) inhibit NAAA, prevent FAE hydrolysis in activated inflammatory cells, and reduce tissue reactions to pro-inflammatory stimuli. Recently, our group disclosed ARN077 (4), a potent NAAA inhibitor that is active in vivo by topical administration in rodent models of hyperalgesia and allodynia. In the present study, we investigated the structure-activity relationship (SAR) of threonine-derived ß-lactone analogues of compound 4. The main results of this work were an enhancement of the inhibitory potency of ß-lactone carbamate derivatives for NAAA and the identification of (4-phenylphenyl)-methyl-N-[(2S,3R)-2-methyl-4-oxo-oxetan-3-yl]carbamate (14q) as the first single-digit nanomolar inhibitor of intracellular NAAA activity (IC50 = 7 nM on both rat NAAA and human NAAA).

Discovery of a new class of highly potent inhibitors of acid ceramidase: synthesis and structure-activity relationship (SAR).

Acid ceramidase (AC) is an intracellular cysteine amidase that catalyzes the hydrolysis of the lipid messenger ceramide. By regulating ceramide levels in cells, AC may contribute to the regulation of cancer cell proliferation and senescence and to the response to cancer therapy. We recently identified the antitumoral agent carmofur (4a) as the first nanomolar inhibitor of intracellular AC activity (rat AC, IC50 = 0.029 µM). In the present work, we expanded our initial structure-activity relationship (SAR) studies around 4a by synthesizing and testing a series of 2,4-dioxopyrimidine-1-carboxamides. Our investigations provided a first elucidation of the structural features of uracil derivatives that are critical for AC inhibition and led us to identify the first single-digit nanomolar inhibitors of this enzyme. The present results confirm that substituted 2,4-dioxopyrimidine-1-carboxamides are a novel class of potent inhibitors of AC. Selected compounds of this class may represent useful probes to further characterize the functional roles of AC.

ß-Lactones Inhibit N-acylethanolamine Acid Amidase by S-Acylation of the Catalytic N-Terminal Cysteine.

The cysteine amidase N-acylethanolamine acid amidase (NAAA) is a member of the N-terminal nucleophile class of enzymes and a potential target for anti-inflammatory drugs. We investigated the mechanism of inhibition of human NAAA by substituted ß-lactones. We characterized pharmacologically a representative member of this class, ARN077, and showed, using high-resolution liquid chromatography-tandem mass spectrometry, that this compound forms a thioester bond with the N-terminal catalytic cysteine in human NAAA.

Neuropeptide FF receptors have opposing modulatory effects on nociception.

The role of neuropeptide FF (NPFF) and its analogs in pain modulation is ambiguous. Although NPFF was first characterized as an antiopioid peptide, both antinociceptive and pronociceptive effects have been reported, depending on the route of administration. Currently, two NPFF receptors, termed FF1 and FF2, have been identified and cloned, but their roles in pain modulation remain elusive because of the lack of availability of selective compounds suitable for systemic administration in in vivo models. Ligand-binding studies confirm ubiquitous expression of both subtypes in brain, whereas only FF2 receptors are expressed spinally. This disparity in localization has served as the foundation of the hypothesis that FF1 receptors mediate the pronociceptive actions of NPFF. We have identified novel small molecule NPFF receptor agonists and antagonists with varying degrees of FF2/FF1 functional selectivity. Using these pharmacological tools in vivo has allowed us to define the roles of NPFF receptor subtypes as pertains to the modulation of nociception. We demonstrate that selective FF2 agonism does not modulate acute pain but instead ameliorates inflammatory and neuropathic pains. Treatment with a nonselective FF1/FF2 agonist potentiates allodynia in neuropathic rats and increases sensitivity to noxious thermal and to non-noxious mechanical stimuli in normal rats in an FF1 antagonist-reversible manner. Treatment with FF1 antagonists reversed established mechanical allodynia, indicating the possibility of increased NPFF tone through FF1 receptors. In conclusion, we provide evidence for the opposing roles of NPFF receptors and highlight selective FF2 agonism and/or selective FF1 antagonism as potential targets warranting further investigation.