Novel Chemical Series of 5-Lipoxygenase-Activating Protein Inhibitors for Treatment of Coronary Artery Disease.

5-Lipoxygenase (5-LO)-activating protein (FLAP) inhibitors have proven to attenuate 5-LO pathway activity and leukotriene production in human clinical trials. However, previous clinical candidates have been discontinued and the link between FLAP inhibition and outcome in inflammatory diseases remains to be established. We here describe a novel series of FLAP inhibitors identified from a screen of 10k compounds and the medicinal chemistry strategies undertaken to progress this series. Compound 4i showed good overall properties and a pIC50 hWBfree of 8.1 and an lipophilic ligand efficiency of 5.2. Target engagement for 4i was established in dogs using ex vivo measurement of leukotriene B4 (LTB4) levels in blood with good correlation to in vitro potency. A predicted human dose of 280 mg b.i.d. suggests a wide margin to any identified in vitro off-target effects and sufficient exposure to achieve an 80% reduction of LTB4 levels in humans. Compound 4i is progressed to preclinical in vivo safety studies.

Synthesis and biological evaluation of C(5)-substituted derivatives of leukotriene biosynthesis inhibitor BRP-7.

Pharmacological intervention with 5-lipoxygenase (5-LO) pathway leading to suppression of leukotriene (LT) biosynthesis is a clinically validated strategy for treatment of respiratory and cardiovascular diseases such as asthma and atherosclerosis. Here we describe the synthesis of a series of C(5)-substituted analogues of the previously described 5-LO-activating protein (FLAP) inhibitor BRP-7 (IC50 = 0.31 µM) to explore the effects of substitution at the C(5)-benzimidazole (BI) ring as a strategy to increase the potency against FLAP-mediated 5-LO product formation. Incorporation of polar substituents on the C(5) position of the BI core, exemplified by compound 11 with a C(5)-nitrile substituent, significantly enhances the potency for suppression of 5-LO product synthesis in human neutrophils (IC50 = 0.07 µM) and monocytes (IC50 = 0.026 µM).

Synthesis of [(3) H] and [(2) H6 ]AZD6642, an inhibitor of 5-lipoxygenase activating protein (FLAP).

An AstraZeneca effort to identify a 5-lipoxygenase activating protein inhibitor with good drug-like properties resulted in the identification of AZD6642. To further understand its drug metabolism and pharmacokinetic properties, it was required labeled with tritium. The tritiation of AZD6642 was effected by Ir-catalyzed exchange chemistry to give an average of one tritium per molecule. Additionally, a stable isotope labeled version of AZD6642 was required to support bioanalytical studies. The synthesis originated from [(2) H6 ]acetone which was converted to the trimethylsilyl cyanide adduct and subsequently reduced to give 2-(aminomethyl)-[1,1,1,3,3,3-(2) H6 ]propan-2-ol in good yield. Carbonylation to give an amide adduct resulted in an intermediate that was converted to the final compound in four steps.

4,5-Diarylisoxazol-3-carboxylic acids: A new class of leukotriene biosynthesis inhibitors potentially targeting 5-lipoxygenase-activating protein (FLAP).

In this article, we report novel leukotriene (LT) biosynthesis inhibitors that may target 5-lipoxygenase-activating protein (FLAP) based on the previously identified isoxazole derivative (8). The design and synthesis was directed towards a subset of 4,5-diaryl-isoxazole-3-carboxylic acid derivatives as LT biosynthesis inhibitors. Biological evaluation disclosed a new skeleton of potential anti-inflammatory agents, exemplified by 39 and 40, which potently inhibit cellular 5-LO product synthesis (IC50 = 0.24 µM, each) seemingly by targeting FLAP with weak inhibition on 5-LO (IC50 ≥ 8 µM). Docking studies and molecular dynamic simulations with 5-LO and FLAP provide valuable insights into potential binding modes of the inhibitors. Together, these diaryl-isoxazol-3-carboxylic acids may possess potential as leads for development of effective anti-inflammatory drugs through inhibition of LT biosynthesis.

Development of an asymmetric synthesis of a chiral quaternary FLAP inhibitor.

A practical sequence involving a noncryogenic stereospecific boronate rearrangement followed by a robust formylation with an in situ generated DCM anion has been developed for the asymmetric construction of an all-carbon quaternary stereogenic center of a FLAP inhibitor. The key boronate rearrangement was rendered noncryogenic and robust by using LDA as the base and instituting an in situ trapping of the unstable lithiated benzylic carbamate with the boronic ester. A similar strategy was implemented for the DCM formylation reaction. It was found that the 1,2-boronate rearrangement for the formylation reaction could be temperature-controlled, thus preventing overaddition of the DCM anion and rendering the process reproducible. The robust stereospecific boronate rearrangement and formylation were utilized for the practical asymmetric synthesis of a chiral quaternary FLAP inhibitor.

Discovery of AZD6642, an inhibitor of 5-lipoxygenase activating protein (FLAP) for the treatment of inflammatory diseases.

A drug discovery program in search of novel 5-lipoxygenase activating protein (FLAP) inhibitors focused on driving a reduction in lipophilicity with maintained or increased ligand lipophilic efficiency (LLE) compared to previously reported compounds led to the discovery of AZD6642 (15b). Introduction of a hydrophilic tetrahydrofuran (THF) ring at the stereogenic central carbon atom led to a significant shift in physicochemical property space. The structure-activity relationship exploration and optimization of DMPK properties leading to this compound are described in addition to pharmacokinetic analysis and an investigation of the pharmacokinetic (PK)-pharmacodynamic (PD) relationship based on ex vivo leukotriene B4 (LTB4) levels in dog. AZD6642 shows high specific potency and low lipophilicity, resulting in a selective and metabolically stable profile. On the basis of initial PK/PD relation measured, a low dose to human was predicted.

Evaluation of endo- and exo-aryl-substitutions and central scaffold modifications on diphenyl substituted alkanes as 5-lipoxygenase activating protein inhibitors.

A search for a suitable replacement for the central norbornyl scaffold presented in the recently disclosed novel FLAP inhibitors is herein described, as well as the SAR study performed on the endo and exo-aryl groups.

5-Lipoxygenase-activating protein (FLAP) inhibitors. Part 4: development of 3-[3-tert-butylsulfanyl-1-[4-(6-ethoxypyridin-3-yl)benzyl]-5-(5-methylpyridin-2-ylmethoxy)-1H-indol-2-yl]-2,2-dimethylpropionic acid (AM803), a potent, oral, once daily FLAP inhibitor.

The potent 5-lipoxygenase-activating protein (FLAP) inhibitor 3-[3-tert-butylsulfanyl-1-[4-(6-ethoxypyridin-3-yl)benzyl]-5-(5-methylpyridin-2-ylmethoxy)-1H-indol-2-yl]-2,2-dimethylpropionic acid 11cc is described (AM803, now GSK2190915). Building upon AM103 (1) (Hutchinson et al. J. Med Chem.2009, 52, 5803-5815; Stock et al. Bioorg. Med. Chem. Lett. 2010, 20, 213-217; Stock et al. Bioorg. Med. Chem. Lett.2010, 20, 4598-4601), SAR studies centering around the pyridine moiety led to the discovery of compounds that exhibit significantly increased potency in a human whole blood assay measuring LTB(4) inhibition with longer drug preincubation times (15 min vs 5 h). Further studies identified 11cc with a potency of 2.9 nM in FLAP binding, an IC(50) of 76 nM for inhibition of LTB(4) in human blood (5 h incubation) and excellent preclinical toxicology and pharmacokinetics in rat and dog. 11cc also demonstrated an extended pharmacodynamic effect in a rodent bronchoalveolar lavage (BAL) model. This compound has successfully completed phase 1 clinical studies in healthy volunteers and is currently undergoing phase 2 trials in asthmatic patients.

Structure-based discovery of inhibitors of microsomal prostaglandin E2 synthase-1, 5-lipoxygenase and 5-lipoxygenase-activating protein: promising hits for the development of new anti-inflammatory agents.

Microsomal prostaglandin E(2) synthase (mPGES)-1 catalyzes the transformation of PGH(2) to PGE(2) that is involved in several pathologies like fever, pain, and inflammatory disorders. To identify novel mPGES-1 inhibitors, we used in silico screening to rapidly direct the synthesis, based on the copper-catalyzed 3 + 2 Huisgen's reaction (click chemistry), of potential inhibitors. We designed 26 new triazole-based compounds in accordance with the pocket binding requirements of human mPGES-1. Docking results, in agreement with ligand efficiency values, suggested the synthesis of 15 compounds that at least in theory were shown to be more efficient in inhibiting mPGES-1. Biological evaluation of these selected compounds has disclosed three new potential anti-inflammatory drugs: (I) compound 4 displaying selectivity for mPGES-1 with an IC(50) value of 3.2 µM, (II) compound 20 that dually inhibits 5-lipoxygenase and mPGES-1, and (III) compound 7 apparently acting as 5-lipoxygenase-activating protein inhibitor (IC(50) = 0.4 µM).