From 2-Alkylsulfanylimidazoles to 2-Alkylimidazoles: An Approach towards Metabolically More Stable p38α MAP Kinase Inhibitors.

In vitro and in vivo metabolism studies revealed that 2-alkylsulfanylimidazole ML3403 (4-(5-(4-fluorophenyl)-2-(methylthio)-1H-imidazol-4-yl)-N-(1-phenylethyl)pyridin-2-amine) undergoes rapid oxidation to the sulfoxide. Replacing the sulfur atom present in the two potent p38α mitogen-activated protein (MAP) kinase inhibitors ML3403 and LN950 (2-((5-(4-fluorophenyl)-4-(2-((3-methylbutan-2-yl)amino)pyridin-4-yl)-1H-imidazol-2-yl)thio)ethan-1-ol) by a methylene group resulted in 2-alkylimidazole derivatives 1 and 2, respectively, having a remarkably improved metabolic stability. The 2-alkylimidazole analogs 1 and 2 showed 20% and 10% biotransformation after 4 h of incubation with human liver microsomes, respectively. They display a 4-fold increased binding affinity towards the target kinase as well as similar in vitro potency and ex vivo efficacy relative to their 2-alkylsulfanylimidazole counterparts ML3403 and LN950. For example, 2-alkylimidazole 2, the analog of LN950, inhibits both the p38α MAP kinase as well as the LPS-stimulated tumor necrosis factor-α release from human whole blood in the low double-digit nanomolar range.

Pyridinylimidazoles as dual glycogen synthase kinase 3ß/p38α mitogen-activated protein kinase inhibitors.

Compounds simultaneously inhibiting two targets that are involved in the progression of the same complex disease may exhibit additive or even synergistic therapeutic effects. Here we unveil 2,4,5-trisubstituted imidazoles as dual inhibitors of p38α mitogen-activated protein kinase and glycogen synthase kinase 3ß (GSK3ß). Both enzymes are potential therapeutic targets for neurodegenerative disorders, like Alzheimer's disease. A set of 39 compounds was synthesized and evaluated in kinase activity assays for their ability to inhibit both target kinases. Among the synthesized compounds, potent dual-target-directed inhibitors showing IC50 values down to the low double-digit nanomolar range, were identified. One of the best balanced dual inhibitors presented in here is N-(4-(2-ethyl-4-(4-fluorophenyl)-1H-imidazol-5-yl)pyridin-2-yl)cyclopropanecarboxamide (20c) (p38α, IC50 = 16 nM; GSK3ß, IC50 = 35 nM) featuring an excellent metabolic stability and an appreciable isoform selectivity over the closely related GSK3α. Our findings were rationalized by computational docking studies based on previously published X-ray structures.

Natural chromones as potential anti-inflammatory agents: Pharmacological properties and related mechanisms.

Chromones are a group of natural substances with a diversity of biological activities. Herein we assessed the pharmacological potential of three chromones (1, 2 and 3) isolated from Dictyoloma vandellianum as anti-inflammatory agents using in vitro and in vivo approaches. During in vitro screening, the production of NO and cytokines by macrophages stimulated with LPS and IFN-γ was inhibited by all chromones at concentrations (5-20 µM) that did not induce cytotoxicity. Analysis of pharmacokinetic parameters (in vitro half-life and intrinsic clearance) using human liver microsomes revealed that 3 has a superior pharmacokinetic profile, compared to 1 and 2. Treatment with 3 (100 mg/kg, ip) did not affect the mice motor performance, while 1 and 2 induced motor deficit. Taking into account the pharmacokinetic profile and absence of motor impairment, 3 was selected for further pharmacological characterization. Corroborating the data from in vitro screening, treatment of cell cultures with 3 (5-20 µM) reduced TNF-α, IL-6 and IL-1ß production by stimulated macrophages. In the complete Freund's adjuvant-induced paw inflammation model in mice, 3 (25 and 50 mg/kg, ip) inhibited mechanical hyperalgesia, edema and cytokine production/release (IL-1ß, IL-6 and TNF-α). 3 (5-20 µM) also reduced the transcriptional activity of NF-κB in stimulated macrophages. Furthermore, treatment with RU486, a glucocorticoid receptor (GR) antagonist, partially prevented the inhibitory effect of 3 on macrophages, indicating that this chromone exerts its anti-inflammatory effects in part through the activation of GR. The results presented herein demonstrate the pharmacological potential of natural chromones, highlighting 3 as a possible candidate for the drug discovery process targeting new anti-inflammatory drugs.

Development, Optimization, and Structure-Activity Relationships of Covalent-Reversible JAK3 Inhibitors Based on a Tricyclic Imidazo[5,4- d]pyrrolo[2,3- b]pyridine Scaffold.

Janus kinases are major drivers of immune signaling and have been the focus of anti-inflammatory drug discovery for more than a decade. Because of the invariable colocalization of JAK1 and JAK3 at cytokine receptors, the question if selective JAK3 inhibition is sufficient to effectively block downstream signaling has been highly controversial. Recently, we discovered the covalent-reversible JAK3 inhibitor FM-381 (23) featuring high isoform and kinome selectivity. Crystallography revealed that this inhibitor induces an unprecedented binding pocket by interactions of a nitrile substituent with arginine residues in JAK3. Herein, we describe detailed structure-activity relationships necessary for induction of the arginine pocket and the impact of this structural change on potency, isoform selectivity, and efficacy in cellular models. Furthermore, we evaluated the stability of this novel inhibitor class in in vitro metabolic assays and were able to demonstrate an adequate stability of key compound 23 for in vivo use.

Trisubstituted Imidazoles with a Rigidized Hinge Binding Motif Act As Single Digit nM Inhibitors of Clinically Relevant EGFR L858R/T790M and L858R/T790M/C797S Mutants: An Example of Target Hopping.

The high genomic instability of non-small cell lung cancer tumors leads to the rapid development of resistance against promising EGFR tyrosine kinase inhibitors (TKIs). A recently detected triple mutation compromises the activity of the gold standard third-generation EGFR inhibitors. We have prepared a set of trisubstituted imidazoles with a rigidized 7-azaindole hinge binding motif as a new structural class of EGFR inhibitors by a target hopping approach from p38α MAPK inhibitor templates. On the basis of an iterative approach of docking, compound preparation, biological testing, and SAR interpretation, robust and flexible synthetic routes were established. As a result, we report two reversible inhibitors 11d and 11e of the clinically challenging triple mutant L858R/T790M/C797S with IC50 values in the low nanomolar range. Furthermore, we developed a kinome selective irreversible inhibitor 45a with an IC50 value of 1 nM against the EGFR L858R/T790M double mutant. Target binding kinetics and metabolic stability data are included. These potent mutant EGFR inhibitors may serve as a basis for the development of structurally novel EGFR probes, tools, or candidates.

Trisubstituted Pyridinylimidazoles as Potent Inhibitors of the Clinically Resistant L858R/T790M/C797S EGFR Mutant: Targeting of Both Hydrophobic Regions and the Phosphate Binding Site.

Inhibition of the epidermal growth factor receptor represents one of the most promising strategies in the treatment of lung cancer. Acquired resistance compromises the clinical efficacy of EGFR inhibitors during long-term treatment. The recently discovered EGFR-C797S mutation causes resistance against third-generation EGFR inhibitors. Here we present a rational approach based on extending the inhibition profile of a p38 MAP kinase inhibitor toward mutant EGFR inhibition. We used a privileged scaffold with proven cellular potency as well as in vivo efficacy and low toxicity. Guided by molecular modeling, we synthesized and studied the structure-activity relationship of 40 compounds against clinically relevant EGFR mutants. We successfully improved the cellular EGFR inhibition down to the low nanomolar range with covalently binding inhibitors against a gefitinib resistant T790M mutant cell line. We identified additional noncovalent interactions, which allowed us to develop metabolically stable inhibitors with high activities against the osimertinib resistant L858R/T790M/C797S mutant.

Tri- and Tetrasubstituted Pyridinylimidazoles as Covalent Inhibitors of c-Jun N-Terminal Kinase 3.

The concept of covalent inhibition of c-Jun N-terminal kinase 3 (JNK3) was successfully transferred to our well validated pyridinylimidazole scaffold varying several structural features in order to deduce crucial structure-activity relationships. Joint targeting of the hydrophobic region I and methylation of imidazole-N1 position increased the activity and reduced the number of off-targets. The most promising covalent inhibitor, the tetrasubstituted imidazole 3-acrylamido-N-(4-((4-(4-(4-fluorophenyl)-1-methyl-2-(methylthio)-1H-imidazol-5-yl)pyridin-2-yl)amino)phenyl)benzamide (7) inhibits the JNK3 in the subnanomolar range (IC50 = 0.3 nM), shows high metabolic stability in human liver microsomes, and displays excellent selectivity in a screening against a panel of 410 kinases. Covalent bond formation to Cys-154 was confirmed by incubation of the inhibitors with wild-type JNK3 and JNK3-C154A mutant followed by mass spectrometry.

Design, Synthesis, and Biological Evaluation of Novel Type I1/2 p38α MAP Kinase Inhibitors with Excellent Selectivity, High Potency, and Prolonged Target Residence Time by Interfering with the R-Spine.

We recently reported 1a (skepinone-L) as a type I p38α MAP kinase inhibitor with high potency and excellent selectivity in vitro and in vivo. However, as a type I inhibitor, it is entirely ATP-competitive and shows just a moderate residence time. Thus, the scope was to develop a new class of advanced compounds maintaining the structural binding features of skepinone-L scaffold like inducing a glycine flip at the hinge region and occupying both hydrophobic regions I and II. Extending this scaffold with suitable residues resulted in an interference with the kinase's R-Spine. By synthesizing 69 compounds, we could significantly prolong the target residence time with one example to 3663 s, along with an excellent selectivity score of 0.006 and an outstanding potency of 1.0 nM. This new binding mode was validated by cocrystallization, showing all binding interactions typifying type I1/2 binding. Moreover, microsomal studies showed convenient metabolic stability of the most potent, herein reported representatives.

Tetra-substituted pyridinylimidazoles as dual inhibitors of p38α mitogen-activated protein kinase and c-Jun N-terminal kinase 3 for potential treatment of neurodegenerative diseases.

Tetra-substituted imidazoles were designed as dual inhibitors of c-Jun N-terminal kinase (JNK) 3 and p38α mitogen-activated protein (MAP) kinase. A library of 45 derivatives was prepared and evaluated in a kinase activity assay for their ability to inhibit both kinases, JNK3 and p38α MAP kinase. Dual inhibitors with IC50 values down to the low double-digit nanomolar range at both enzymes were identified. The best balanced dual JNK3/p38α MAP kinase inhibitors are 6m (IC50: JNK3, 18 nM; p38α, 30 nM) and 14d (IC50: JNK3, 26 nM; p38α, 34 nM) featuring both excellent solubility and metabolic stability. They may serve as useful tool compounds for preclinical proof-of-principle studies in order to validate the synergistic role of both kinases in the progression of Huntington's disease.