Quantum Mechanics/Molecular Mechanics Modeling of Fatty Acid Amide Hydrolase Reactivation Distinguishes Substrate from Irreversible Covalent Inhibitors

Carbamate and urea derivatives are important classes of fatty acid amide hydrolase (FAAH) inhibitors that carbamoylate the active-site nucleophile Ser241. In the present work, the reactivation mechanism of carbamoylated FAAH is investigated by means of a quantum mechanics/molecular mechanics (QM/MM) approach. The potential energy surfaces for decarbamoylation of FAAH covalent adducts, derived from the <i>O</i>-aryl carbamate URB597 and from the <i>N</i>-piperazinylurea JNJ1661610, were calculated and compared to that for deacylation of FAAH acylated by the substrate oleamide. Calculations show that a carbamic group bound to Ser241 prevents efficient stabilization of transition states of hydrolysis, leading to large increments in the activation barrier. Moreover, the energy barrier for the piperazine carboxylate was significantly lower than that for the cyclohexyl carbamate derived from URB597. This is consistent with experimental data showing slowly reversible FAAH inhibition for the <i>N</i>-piperazinylurea inhibitor and irreversible inhibition for URB597

Synthesis and Biological Evaluation of Metabolites of 2‑<i>n</i>‑Butyl-9-methyl-8-[1,2,3]triazol-2-yl‑9<i>H</i>‑purin-6-ylamine (ST1535), A Potent Antagonist of the A_2A Adenosine Receptor for the Treatment of Parkinson’s Disease

The synthesis and preliminary in vitro evaluation of five metabolites of the A_2A antagonist ST1535 (<b>1</b>) are reported. The metabolites, originating in vivo from enzymatic oxidation of the 2-butyl group of the parent compound, were synthesized from 6-chloro-2-iodo-9-methyl-9<i>H</i>-purine (<b>2</b>) by selective C–C bond formation via halogen/magnesium exchange reaction and/or palladium-catalyzed reactions. The metabolites behaved in vitro as antagonist ligands of cloned human A_2A receptor with affinities (<i>K</i>_i 7.5–53 nM) comparable to that of compound <b>1</b> (<i>K</i>_i 10.7 nM), thus showing that the long duration of action of <b>1</b> could be in part due to its metabolites. General behavior after oral administration in mice was also analyzed

Synthesis of (<i>E</i>)‑8-(3-Chlorostyryl)caffeine Analogues Leading to 9‑Deazaxanthine Derivatives as Dual A_2A Antagonists/MAO‑B Inhibitors

A systematic modification of the caffeinyl core and substituents of the reference compound (<i>E</i>)-8-(3-chlorostyryl)­caffeine led to the 9-deazaxanthine derivative (<i>E</i>)-6-(4-chlorostyryl)-1,3,5,-trimethyl-1<i>H</i>-pyrrolo­[3,2-<i>d</i>]­pyrimidine-2,4-(3<i>H</i>,5<i>H</i>)-dione (<b>17f</b>), which acts as a dual human A_2a antagonist/MAO-B inhibitor (<i>K</i>_i(A_2A) = 260 nM; IC₅₀(MAO-B) = 200 nM; IC₅₀(MAO-A) = 10 μM) and dose dependently counteracts haloperidol-induced catalepsy in mice from 30 mg/kg by the oral route. The compound is the best balanced A_2A antagonist/MAO-B inhibitor reported to date, and it could be considered as a new lead in the field of anti-Parkinson’s agents. A number of analogues of <b>17f</b> were synthesized and qualitative SARs are discussed. Two analogues of <b>17f</b>, namely <b>18b</b> and <b>19a</b>, inhibit MAO-B with IC₅₀ of 68 and 48 nM, respectively, being 5–7-fold more potent than the prototypical MAO-B inhibitor deprenyl (IC₅₀ = 334 nM)

Synthesis and Structure–Activity Relationship (SAR) of 2‑Methyl-4-oxo-3-oxetanylcarbamic Acid Esters, a Class of Potent <i>N</i>‑Acylethanolamine Acid Amidase (NAAA) Inhibitors

<i>N</i>-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 β-lactone derivatives (<i>S</i>)-<i>N</i>-(2-oxo-3-oxetanyl)-3-phenylpropionamide (<b>2</b>) and (<i>S</i>)-<i>N</i>-(2-oxo-3-oxetanyl)-biphenyl-4-carboxamide (<b>3</b>) inhibit NAAA, prevent FAE hydrolysis in activated inflammatory cells, and reduce tissue reactions to pro-inflammatory stimuli. Recently, our group disclosed ARN077 (<b>4</b>), 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 β-lactone analogues of compound <b>4</b>. The main results of this work were an enhancement of the inhibitory potency of β-lactone carbamate derivatives for NAAA and the identification of (4-phenylphenyl)-methyl-<i>N</i>-[(2<i>S</i>,3<i>R</i>)-2-methyl-4-oxo-oxetan-3-yl]­carbamate (<b>14q</b>) as the first single-digit nanomolar inhibitor of intracellular NAAA activity (IC₅₀ = 7 nM on both rat NAAA and human NAAA)

A Potent Systemically Active <i>N</i>‑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, <i>N</i>-acylethanolamine acid amidase (NAAA), which is highly expressed in macrophages. Here, we describe a new class of β-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