ABSTRACT
Indole-5-carboxylic acids with 3-aryloxy-2-oxopropyl residues in position 1 have been found to be potent inhibitors of human cytosolic phospholipase A2α (cPLA2α). In the course of structure-activity relationship studies, we investigated the effect of a substitution of indole 3 position with acyl, alkyl, and oxadiazole residues. The highest increase of inhibitory potency could be achieved by a 3-methyl-1,2,4-oxadiazol-5-yl-moiety. Appropriate compound 40 revealed an IC50 of 0.0021 µM against isolated cPLA2α. In a cellular assay applying human platelets 40 blocked cPLA2α activity even with an IC50 of 0.0006 µM. Metabolic stability and aqueous solubility of the target compounds were also determined. Furthermore, one selected compound was tested for peroral bioavailability in mice.
Subject(s)
Group IV Phospholipases A2/antagonists & inhibitors , Indoles/chemistry , Oxadiazoles/pharmacology , Phospholipase A2 Inhibitors/pharmacology , Animals , Biological Availability , Humans , Indoles/pharmacology , Inhibitory Concentration 50 , Magnetic Resonance Spectroscopy , Mice , Mice, Inbred C57BL , Oxadiazoles/chemistry , Phospholipase A2 Inhibitors/chemistry , Phospholipase A2 Inhibitors/pharmacokinetics , Solubility , Spectrometry, Mass, Electrospray IonizationABSTRACT
Indole-5-carboxylic acids with 3-aryloxy-2-oxopropyl residues in position 1 were previously reported to be potent inhibitors of human cytosolic phospholipase A(2)alpha (cPLA(2)alpha). In continuation of our attempts to develop clinical active cPLA(2)alpha inhibitors, a series of structurally related indole-5-carboxylic acids with reduced lipophilicity was synthesized and tested for cPLA(2)alpha-inhibitory potency. Furthermore, the thermodynamic solubility of these compounds and their metabolic stability in rat liver microsomes were evaluated. With an IC(50) of 0.012 microM against the isolated enzyme, compound 36 was one of the most potent cPLA(2)alpha inhibitors that emerged during the structure-activity relationship study. Concomitantly, 36 possessed the highest water solubility (212 microg/mL at pH 7.4) of all new target compounds. Despite these favorable properties, peroral application of 36 (100 mg/kg) in mice only led to low concentrations of the substance in blood plasma. A very high plasma clearance was observed after intravenous administration of 36 (10 mg/kg). However, in a topical murine model of contact dermatitis, 36 showed a pronounced anti-inflammatory in vivo activity.
Subject(s)
Anti-Inflammatory Agents, Non-Steroidal/chemical synthesis , Cytosol/enzymology , Group IV Phospholipases A2/antagonists & inhibitors , Indoles/chemical synthesis , Phenyl Ethers/chemical synthesis , Administration, Topical , Animals , Anti-Inflammatory Agents, Non-Steroidal/pharmacokinetics , Anti-Inflammatory Agents, Non-Steroidal/pharmacology , Bile/metabolism , Biological Availability , Blood Platelets/drug effects , Blood Platelets/enzymology , Dermatitis, Contact/drug therapy , Drug Stability , Glucuronides/metabolism , Humans , Indoles/pharmacokinetics , Indoles/pharmacology , Mice , Mice, Inbred C57BL , Microsomes, Liver/metabolism , Phenyl Ethers/pharmacokinetics , Phenyl Ethers/pharmacology , Rats , Solubility , Structure-Activity Relationship , ThermodynamicsABSTRACT
Cytosolic phospholipase A(2)alpha (cPLA(2)alpha) and fatty acid amide hydrolase (FAAH) are enzymes, which have emerged as attractive targets for the development of analgetic and anti-inflammatory drugs. We recently reported that 1-[3-(4-octylphenoxy)-2-oxopropyl]indole-5-carboxylic acid (10) and related compounds are inhibitors of cPLA(2)alpha. Since cPLA(2)alpha and FAAH possess several common structural features, we now screened this substance series together with some new derivatives for FAAH inhibition. Some of the assayed compounds proved to be selective cPLA(2)alpha inhibitors, while others showed high FAAH and moderate cPLA(2)alpha inhibitory potency. Furthermore, several derivatives were favorably active against both enzymes and, therefore, could represent agents, which have improved analgetic and anti-inflammatory qualities in comparison with selective cPLA(2)alpha and FAAH inhibitors.
Subject(s)
Amidohydrolases/antagonists & inhibitors , Enzyme Inhibitors/pharmacology , Group IV Phospholipases A2/antagonists & inhibitors , Heterocyclic Compounds/pharmacology , Indoles/pharmacology , Amidohydrolases/metabolism , Animals , Enzyme Inhibitors/chemical synthesis , Enzyme Inhibitors/chemistry , Group IV Phospholipases A2/isolation & purification , Group IV Phospholipases A2/metabolism , Heterocyclic Compounds/chemical synthesis , Heterocyclic Compounds/chemistry , Humans , Indoles/chemical synthesis , Indoles/chemistry , Molecular Conformation , Rats , Stereoisomerism , Structure-Activity RelationshipABSTRACT
The indole ring systems of the cytosolic phospholipase A(2)alpha (cPLA(2)alpha) inhibitor 1-[3-(4-octylphenoxy)-2-oxopropyl]indole-5-carboxylic acid (2) and the isomeric 6-carboxylic acid (3) were replaced by benzimidazole, benzotriazole and indazole scaffolds, respectively. The effect of the structural variations on cPLA(2)alpha inhibitory potency, metabolic stability and solubility was studied. The lead 2 and the indazole-5-carboxylic acid 28 were the metabolically most stable compounds in an assay with rat liver microsomes, while the benzimidazole-5-carboxylic acid derivative 13 possessed the best water solubility (22 microg/mL at pH 7.4). The indazole-5-carboxylic acid 28 revealed the highest cPLA(2)alpha inhibitory potency of the compounds in this series. With an IC(50)-value of 0.005 microM it was about sevenfold more active than the lead 2.
Subject(s)
Benzimidazoles/chemical synthesis , Cytosol/enzymology , Group IV Phospholipases A2/antagonists & inhibitors , Indazoles/chemical synthesis , Indoles/chemical synthesis , Propionates/chemical synthesis , Triazoles/chemical synthesis , Benzimidazoles/pharmacology , Cytosol/drug effects , Group IV Phospholipases A2/metabolism , Humans , Indazoles/pharmacology , Indoles/pharmacology , Propionates/pharmacology , Stereoisomerism , Triazoles/pharmacologyABSTRACT
The synthesis and structure-activity relationship study of a series of 1-indol-1-yl-3-phenoxypropan-2-one inhibitors of cytosolic phospholipase A(2)alpha (cPLA(2)alpha) are described. The compounds were evaluated in a vesicle assay with isolated cPLA(2)alpha and in cellular assays with intact human platelets. Systematic variation led to 3-methylhydrogen 1-[3-(4-decyloxyphenoxy)-2-oxopropyl]indole-3,5-dicarboxylate (57), which revealed the highest activity against the isolated enzyme. With an IC(50) value of 4.3 nM in this assay, it is one of the most potent in vitro cPLA(2)alpha inhibitors known today.
