p38MAP kinase inhibitors. Part 1: design and development of a new class of potent and highly selective inhibitors based on 3,4-dihydropyrido[3,2-d]pyrimidone scaffold

A new class of p38 antagonists based on 3,4-dihydropyrido[3,2,-d]pyrimidine scaffold has been developed. These inhibitors exhibit unprecedented selectivity towards p38 over other very closely related kinases. Compounds 25, 33, and 34 were identified as benchmark analogues for follow-up studies. They show good potency for enzyme inhibition and excellent functional activity.     

p38 MAP kinase inhibitors. Part 3: SAR on 3,4-dihydropyrimido[4,5-d]pyrimidin-2-ones and 3,4-dihydropyrido[4,3-d]pyrimidin-2-ones

p38 inhibitors based on 3,4-dihydropyrimido[4,5-d]pyrimidin-2-one and 3,4-dihydropyrido[4,3-d]pyrimidin-2-one platforms were synthesized and preliminary SAR explored. Among the pyrimido-pyrimidones the emergence of two sub-types of analogs-C7-amino-pyrimidines such as 24 and C7-amino-piperidines such as 42-characterized with good p38 inhibition and better off-target profiles in terms of ion channel activities was significant. Representative compound 54 in the pyrido-pyrimidone class was found to be equipotent with corresponding analog in the quinazolinone series.     

Identification and SAR of a new series of thieno[3,2-d]pyrimidines as Tpl2 kinase inhibitors

We report here the synthesis and SAR of a new series of thieno[3,2-d]pyrimidines as potent Tpl2 kinase inhibitors. The proposed binding mode suggests the potential flipped binding mode depending on the substitution. Biacore studies show evidence of binding of these molecules to the protein kinase. The kinome inhibition profile of these molecules suggests good selectivity.     

Discovery of 5,6,7,8-tetrahydropyrido[3,4-d]pyrimidine inhibitors of Erk2

The discovery and optimization of a series of tetrahydropyridopyrimidine based extracellular signal-regulated kinase (Erks) inhibitors discovered via HTS and structure based drug design is reported. The compounds demonstrate potent and selective inhibition of Erk2 and knockdown of phospho-RSK levels in HepG2 cells and tumor xenografts.     

3D-QSAR studies on thieno[3,2-d]pyrimidines as phosphodiesterase IV inhibitors

Cyclic nucleotide phosphodiesterase IV (PDE IV) inhibitors find utility in asthma and Chronic Obstructive Pulmonary Disease (COPD) therapy. A series of 29 thieno[3,2-d]pyrimidines with affinity for PDE IV was subjected to three dimensional quantitative structure activity relationship (3D-QSAR) studies using comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA). Both CoMFA and CoMSIA provided statistically valid models with good correlative and predictive power. The incorporation of hydrophobic, hydrogen bond donor and hydrogen bond acceptor fields showed insignificant improvement in CoMSIA model. The 3D-QSAR models provide information for predicting the affinity of related compounds and designing more potent inhibitors.     

Synthesis and anticancer activities of thieno[3,2-d]pyrimidines as novel HDAC inhibitors

A series of thieno[3,2-d]pyrimidines bearing a hydroxamic acid moiety as novel HDAC inhibitors were designed and synthesized. The structures of the new synthesized compounds were confirmed using IR, ¹H, ¹³C NMR spectrum. Compounds 11–13 showed potent inhibitory activities against HDACs with IC₅₀ values at 0.38, 0.49 and 0.61 μM. Most of target compounds displayed strong anti-proliferative activity by a MTT assay on three human cancer cell lines including HCT-116, MCF-7 and HeLa. Compound 11, having potent inhibitory activities against HDACs, induced apoptosis and G2/M cell cycle arrest in HCT-116 cell line.     

Dual EGFR/ErbB-2 inhibitors from novel pyrrolidinyl-acetylenic thieno[3,2-d]pyrimidines

A novel class of substituted pyrrolidinyl-acetylenic thieno[3,2-d]pyrimidines has been identified that are potent and selective inhibitors of both EGFR/ErbB-2 receptor tyrosine kinases. The inhibitors are found to display a range of enzyme and cellular potency and also to display a varying level of covalent modification of the kinase targets. Selected molecules, including compound 15h, were found to be potent in enzymatic and cellular assays while also demonstrating exposure in the mouse from an oral dose.     

Synthesis and cytotoxicity of 8-cyano-3-substitutedalkyl-5-methyl-4-methylene-7-methoxy-3,4-dihydropyrido[4,3-d]pyrimidines

Synthesis and cytotoxicity of 11 4-methylene pyrido[4,3-d]pyrimidines 5a-k were described. Cytotoxicity assay results showed that some compounds had much stronger antitumor activity than Fluorouracil against KB cell lines. The most active compound 5i exhibited high potency against KB, CNE2, MGC-803 cell lines with IC(50) values of 0.48, 0.15, 0.59 μM, respectively. The preliminary structure-activity relationships indicated that the introduction of benzyl groups bearing electron-donating function groups is favorable for the activity.     

Antiproliferative activities of halogenated thieno[3,2-d]pyrimidines

The in vitro evaluation of thieno[3,2-d]pyrimidines identified halogenated compounds 1 and 2 with antiproliferative activity against three different cancer cell lines. A structure activity relationship study indicated the necessity of the chlorine at the C4-position for biological activity. The two most active compounds 1 and 2 were found to induce apoptosis in the leukemia L1210 cell line. Additionally, the compounds were screened against a variety of other microbial targets and as a result, selective activity against several fungi was also observed. The synthesis and preliminary biological results are reported herein.     

Synthesis and biological activity of pyrazolo[3,4-d]thiazolo[3,2-a]pyrimidin-4-one derivatives: in silico approach

Xanthine oxidase (XO) is responsible for the pathological condition called gout. Inhibition of XO activity by various pyrazolo[3,4-d]thiazolo[3,2-a]pyrimidine-4-one derivatives was assessed and compared with the standard inhibitor allopurinol. Out of 10 synthesized compounds, two compounds, viz. 3-amino-6-(2-hydroxyphenyl)-1H-pyrazolo[3,4-d]thiazolo[3,2-a]pyrimidin-4-one (3b) and 3-amino-6-(4-chloro-2-hydroxy-5-methylphenyl)-1H-pyrazolo[3,4-d]thiazolo[3,2-a]pyrimidin-4-one (3g) were found to have promising XO inhibitory activity of the same order as allopurinol. Both compounds and allopurinol inhibited competitively with comparable Ki (3b: 3.56?µg, 3g: 2.337?µg, allopurinol: 1.816?µg) and IC₅₀ (3b: 4.228?µg, 3g: 3.1?µg, allopurinol: 2.9?µg) values. The enzyme–ligand interaction was studied by molecular docking using Autodock in BioMed Cache V. 6.1 software. The results revealed a significant dock score for 3b (?84.976?kcal/mol) and 3g (?90.921?kcal/mol) compared with allopurinol (?55.01?kcal/mol). The physiochemical properties and toxicity of the compounds were determined in silico using online computational tools. Overall, in vitro and in silico study revealed 3-amino-6-(4-chloro-2-hydroxy-5-methylphenyl)-1H-pyrazolo[3,4-d]thiazolo[3,2–a]pyrimidin-4-one (3g) as a potential lead compound for the design and development of XO inhibitors.     

Pyrazolo[3,4-d]pyrimidines as adenosine antagonists

A large number of nitrogen heterocycles structurally related to caffeine and theophylline have been tested for activity as adenosine antagonists. Preliminary screening, utilizing displacement of [3H]N6-phenylisopropyladenosine (PIA) binding to rat brain membranes, identified several pyrazolo[3,4-d]pyrimidines with potential antagonist activity. These were then tested for their ability to antagonize adenosine-stimulated adenylate cyclase of guinea-pig slices and to block adenosine receptors which mediate presynaptic inhibition of transmitter release from cholinergic nerves in guinea-pig ileum. Of several compounds found to have antagonist activity, one of these, 4,6-bis-alpha- carbamoylethylthio -1-phenylpyrazolo[3,4-d]pyrimidine ( DJB -KK) was approximately an order of magnitude more potent than theophylline in both tests. GTP greatly reduces the potency of purine agonists, but not antagonists, as inhibitors of [3H] PIA binding; the potency of the pyrazolo[3,4-d]pyrimidine compounds was not altered by GTP. The compounds have no significant activity against [3H]adenosine uptake or on the binding of ligands to muscarinic cholinergic, beta-adrenergic, GABA or L-glutamate receptors.     

Aurora kinase A inhibitors: identification, SAR exploration and molecular modeling of 6,7-dihydro-4H-pyrazolo-[1,5-a]pyrrolo[3,4-d]pyrimidine-5,8-dione scaffold

Tricyclic 6,7-dihydro-4H-pyrazolo[1,5-a]pyrrolo[3,4-d]pyrimidine-5,8-dione was identified as a novel scaffold for Aurora kinase A inhibition through virtual screening. SAR exploration coupled with molecular modeling of 8a reveals the minimum pharmacophore requirements for Aurora kinase A inhibition.     

Discovery of 4-anilino-N-methylthieno[3,2-d]pyrimidines and 4-anilino-N-methylthieno[2,3-d]pyrimidines as potent apoptosis inducers

We report the discovery of N-((benzo[d][1,3]dioxol-5-yl)methyl)-6-phenylthieno[3,2-d]pyrimidin-4-amine (2a) as an apoptosis inducer using our proprietary cell- and caspase-based ASAP HTS assay, and SAR study of HTS hit 2a which led to the discovery of 4-anilino-N-methylthieno[3,2-d]pyrimidines and 4-anilino-N-methylthieno[2,3-d]pyrimidines as potent apoptosis inducers. Compounds 5d and 5e were the most potent with EC₅₀ values of 0.008 and 0.004 μM in T47D human breast cancer cells, respectively. Compound 5d was found to be highly active in the MX-1 breast cancer model. Functionally, compounds 5d and 5e both induced apoptosis through inhibition of tubulin polymerization.     

Synthesis and stereochemical effects of pyrrolidinyl-acetylenic thieno[3,2-d]pyrimidines as EGFR and ErbB-2 inhibitors

A novel class of pyrrolidinyl-acetyleneic thieno[3,2-d]pyrimidines has been identified which potently inhibit the EGFR and ErbB-2 receptor tyrosine kinases. Synthetic modifications of the pyrrolidine carbamate moiety result in a range of effects on enzyme and cellular potency. In addition, the impact of the absolute stereochemical configuration on cellular potency and oral mouse pharmacokinetics is described.     

Synthesis and SAR of new pyrrolo[2,1-f][1,2,4]triazines as potent p38 alpha MAP kinase inhibitors

A novel series of compounds based on the pyrrolo[2,1-f][1,2,4]triazine ring system have been identified as potent p38 alpha MAP kinase inhibitors. The synthesis, structure-activity relationships (SAR), and in vivo activity of selected analogs from this class of inhibitors are reported. Additional studies based on X-ray co-crystallography have revealed that one of the potent inhibitors from this series binds to the DFG-out conformation of the p38 alpha enzyme.     

Synthesis, SAR and biological evaluation of 1,6-disubstituted-1H-pyrazolo[3,4-d]pyrimidines as dual inhibitors of Aurora kinases and CDK1

Since the early 2000s, the Aurora kinases have become major targets of oncology drug discovery particularly Aurora-A and Aurora-B kinases (AKA/AKB) for which the selective inhibition in cells lead to different phenotypes. In addition to targeting these Aurora kinases involved in mitosis, CDK1 has been added as a primary inhibition target in hopes of enhancing the cytotoxicity of our chemotypes harboring the pyrazolopyrimidine core. SAR optimization of this series using the AKA, AKB and CDK1 biochemical assays led to the discovery of the compound 7h which combines strong potency against the 3 kinases with an acceptable microsomal stability. Finally, switching from a primary amide to a two-substituted pyrrolidine amide gave rise to compound 15a which exhibited the desired AKA/CDK1 inhibition phenotype in cells but showed moderate activity in animal models using HCT116 tumor cell lines.     

Anticytokinin activity of 4-substituted triazolo[4,5-d]pyrimidines and 4-substituted pyrazolo[3,4-d]pyrimidines

The synthesis and physiological activity of some novel 4-substituted triazolo[4,5-d]pyrimidines and 4-substituted pyrazolo[3,4-d]pyrimidines are described. Most of the compounds possessed high anticytokinin activity towards purine (benzyladenine) and phenylurea (4-PU-30) type cytokinins. 1-Benzyl-4-ethoxycarbonylpiperazinyl-1H-1,2,3-triazolo[4,5-d]pyrimidine almost completely removed cytokinin stimulated effects—betacyanin synthesis in Amaranthus caudatus cotyledons; growth of radish cotyledons and retention of chlorophyll in leaf explants. Some chemical structurephysiological activity relationships have been established.     

Discovery of 3,6-dihydro-2H-pyran as a morpholine replacement in 6-aryl-1H-pyrazolo[3,4-d]pyrimidines and 2-arylthieno[3,2-d]pyrimidines: ATP-competitive inhibitors of the mammalian target of rapamycin (mTOR)

The morpholine hinge-region binding group on a series of pyrazolopyrimidine and thienopyrimidine mammalian target of rapamycin (mTOR) inhibitors was replaced with 3,6-dihydro-2H-pyran (DHP), giving compounds of equivalent potency and selectivity versus PI3K. These results establish the DHP group as a hinge-region binding motif for the preparation of highly potent and selective mTOR inhibitors.     

Synthesis and biological evaluation of pyrido[3',2':4,5]furo[3,2-d]pyrimidine derivatives as novel PI3 kinase p110alpha inhibitors

4-Morpholin-4-ylpyrido[3',2':4,5]thieno[3,2-d]pyrimidine 2a was discovered in our chemical library as a novel p110alpha inhibitor with an IC(50) of 1.4 microM. By structural modification of 2a, the 2-aryl-4-morpholinopyrido[3',2':4,5]furo[3,2-d]pyrimidine derivative 10e was discovered as a p110alpha inhibitor with approximately 400-fold greater potency than 2a. Evaluation of isoform selectivity showed that 10e is a potent inhibitor of p110beta. Furthermore, 10e showed anti-proliferative activity in various cell lines, including multi-drug resistant MCF7/ADR-res cells, and was effective against HeLa human cervical tumor xenografts in nude mice.