Dominik Hauser

Design, synthesis, and biological evaluation of novel Tri- and tetrasubstituted imidazoles as highly potent and specific ATP-mimetic inhibitors of p38 MAP kinase: focus on optimized interactions with the enzyme's surface-exposed front region.

The synthesis, biological testing, and SAR of novel 2,4,5- and 1,2,4,5-substituted 2-thioimidazoles are described. Amino, oxy, or thioxy substituents at the 2-position of the pyridinyl moiety were evaluated for their contributions to inhibitor potency and selectivity against p38 mitogen activated protein kinase (p38 MAPK) as well as for the ability to minimize cytochrome P450 (CYP450) inhibition. Incorporation of polar substituted (cyclo)aliphatic amino substituents (e.g., tetrahydropyranylamino), which positively interacted with the surface-exposed front region (hydrophobic region II) of the enzyme led to the identification of extremely potent p38 MAPK inhibitors with p38 IC 50 values in the low nanomolar range. Approximately 90 pyridinylimidazole-based compounds with a range of potencies against p38alpha MAP kinase were further investigated for their ability to inhibit the release of tumor necrosis factor-alpha (TNFalpha) and/or interleukin-1beta (IL-1beta) from human whole blood. Some of the most promising drug candidates underwent selectivity profiling against a panel of 17 different kinases besides p38alpha and/or were tested for their interaction potential toward a number of metabolically relevant CYP450 isozymes.

3,4-Diaryl-isoxazoles and -imidazoles as Potent Dual Inhibitors of p38α Mitogen Activated Protein Kinase and Casein Kinase 1δ

In this study, we report on the discovery of isoxazole 1 as a potent dual inhibitor of p38alpha (IC(50) = 0.45 microM) and CK1delta (IC(50) = 0.23 microM). Because only a few effective small molecule inhibitors of CK1 have been described so far, we aimed to develop this structural class toward specific agents. Molecular modeling studies comparing p38alpha/CK1delta suggested an optimization strategy leading to design, synthesis, biological characterization, and SAR of highly potent compounds including 9 (IC(50) p38alpha = 0.006 microM; IC(50) CK1delta = 1.6 microM), 13 (IC(50) p38alpha = 2.52 microM; IC(50) CK1delta = 0.033 microM), 17 (IC(50) p38alpha = 0.019 microM; IC(50) CK1delta = 0.004 microM; IC(50) CK1epsilon = 0.073 microM), and 18 (CKP138) (IC(50) p38alpha = 0.041 microM; IC(50) CK1delta = 0.005 microM; IC(50) CK1epsilon = 0.447 microM) possessing differentiated specificity. Selected compounds were profiled over 76 kinases and evaluation of their cellular efficacy showed 18 (CKP138) to be a highly potent and dual-specific inhibitor of CK1delta and p38alpha.

Tri- and tetrasubstituted imidazoles as p38α mitogen-activated protein kinase inhibitors

The synthesis of 2,4,5-trisubstituted and 1,2,4,5-tetrasubstituted imidazoles as potent p38α mitogen-activated protein kinase inhibitors is described. The trisubstituted imidazole series was found to be more potent than the tetrasubstituted imidazole series. Many of these compounds show low-nanomolar activities in the isolated p38α MAP kinase inhibition assay. The structure-activity relationships between these two series are different and not comparable.

Fluorescence polarization binding assay to develop inhibitors of inactive p38α mitogen-activated protein kinase

Development of inhibitors that target inactive kinase conformations is becoming a more attractive approach to kinase inhibitor research. The major advantage of this methodology is that targeting the inactive conformation reduces competition with high intracellular adenosine triphosphate (ATP) concentrations. p38alpha Mitogen-activated protein kinase (MAPK) signaling has been identified as the principal mediator of inflammation associated with a spectrum of disorders (e.g., arthritis, Alzheimers disease, various malignancies). To allow identification and development of p38alpha MAPK inhibitors that preferentially bind to the inactive conformation, a novel fluorescence polarization-based binding assay is presented. The assay is homogeneous, requires low amounts of the kinase and fluoroprobe, and does not rely on radioactivity. It may, therefore, offer an inexpensive alternative to current p38alpha MAPK inhibitor screening methods. The validation of the system with known p38alpha MAPK inhibitors confirmed that the binding assay, rather than the conventional enzyme activity assay, correlates with cellular efficacy. Finally, we show that pyridinyl imidazoles that potently bind to the inactive p38alpha MAPK prevent activation of p38 MAPK in living cells, suggesting that pyridinyl imidazoles other than SB203580 are able to induce the DFG-out conformation that is incompatible with activation (where DFG is a single-letter amino acid code for the aspartate-phenylalanine-glycine sequence at the start of the activation loop).

2-Acylaminopyridin-4-ylimidazoles as p38 MAP kinase inhibitors: Design, synthesis, and biological and metabolic evaluations.

Targeting cytokines has become an important focus in the treatment of many inflammatory disorders. p38 MAP kinase (MAPK) is the key enzyme in regulating the biosynthesis and release of pro‐inflammatory cytokines such as IL‐1β and TNFα. Inhibition of p38 MAPK results in decreased expression of these cytokines. Tri‐ and tetrasubstituted pyridinylimidazoles are potent inhibitors of p38 MAPK. Substitution on the pyridinyl moiety allows the design of inhibitors that show increased selectivity and activity by targeting the enzymes hydrophobic region II. The objective of this study was to synthesize novel 1,2,4,5‐tetrasubstituted imidazole derivates and to characterize them not only for their ability to inhibit p38 MAPK and modulate cytokine release in human whole blood, but also to evaluate their metabolic stability. Biological data and metabolic studies demonstrate that the introduction of a 2‐acylamino function at C2 of the pyridine results in highly efficient and metabolically stable inhibitors relative to C2‐alkylamino derivatives. A series of novel candidates was investigated for metabolic stability in human liver microsomes and in human whole blood. Additionally, metabolic S‐oxidation was investigated, and possible metabolites were synthesized.

Design, synthesis and characterization of N9/N7-substituted 6-aminopurines as VEGF-R and EGF-R inhibitors.

In this study we report on the design, synthesis and biological characterization of novel N(9) or N(7) arylethanone-substituted 6-aminopurines and 6-methoxypurines, respectively, as EGF-R and VEGF-R inhibitors. The compounds were initially profiled in a panel of 24 cancer-relevant protein kinases. Dependent on the regio-substitution of the purine core we found inhibition activity for EGF-R and VEGF-R with IC(50) values in the microM range. The two novel N(9)/N(7) 2-(6-amino-purine)-1-(1H-indole-3-yl)ethanone derivatives were characterized in an enhanced panel of 78 kinases showing the N(9) derivative to also inhibit MNK1 and IRR while the N(7) isomer was found to be specific for VEGF-R2.

Synthesis and Biological Testing of N-Aminoimidazole-Based p38α MAP Kinase Inhibitors

The p38 mitogen‐activated protein (MAP) kinase α plays a central role in the regulation of cellular responses such as differentiation, proliferation, apoptosis, and inflammation. Inhibition of p38 results in decreased synthesis of pro‐inflammatory cytokines. To date, diverse p38α inhibitors are in phase II clinical trials for numerous cytokine‐dependent diseases. 2‐Sulfanylimidazole derivatives offer advantages over the prototype inhibitor SB 203580, including fewer cytochrome P450 interactions and better kinetic properties. The aim of this study was to develop novel 1,2,4,5‐tetrasubstituted pyridinylimidazoles with acyl residues at the imidazole N1 position that can interact with the kinases hydrophobic region II (HR II) or sugar pocket (SP) to improve both selectivity and activity. The substitution pattern was optimized by variation of the acyl moiety at the N1 position of the N‐aminoimidazole core. Acylation of the amino function was used for optimization and led to potent p38α MAPK inhibitors.

N-{4-[4-(4-Fluoro-phen-yl)-1-methyl-2-[(R)-methyl-sulfin-yl]-1H-imidazol-5-yl]-2-pyridyl}acetamide dihydrate.

In the crystal structure of the title compound, C18H17FN4O2S·2H2O, the organic molecules are linked by intermolecular O—H⋯O, O—H⋯N and N—H⋯O hydrogen bonds with the water molecules, generating a three-dimensional network. The imidazole ring system forms a dihedral angle of 24.9 (2)° with the 4-fluorophenyl ring. The pyridine ring is oriented approximately perpendicular [72.24 (8)°] to the imidazole ring system.

2-(6-Amino-7H-purin-7-yl)-1-phenylethanone

In the title compound, C13H11N5O, the exocyclic amino group of one purine molecule forms two intermolecular N—H N hydrogen bonds to different ring N atoms of another molecule. The purine system is orientated almost perpendicular [77.96 (6) ] to the phenylethanone substituent. The preparation of the title compound occurred via a regioselective synthesis using the methyl(aqua)cobaloxime complex CH3Co(DH)2OH2 as a temporary auxiliary, and its X-ray crystal structure confirmed the regioselective N-alkylation of this molecule.