(2S,4S)-1-[2-(1,1-Dimethyl-3-oxo-3-pyrrolidin-1-yl-propylamino)acetyl]-4-fluoro-pyrrolidine-2-carbonitrile: A potent,selective, and orally bioavailable dipeptide-derived inhibitor of dipeptidyl peptidase IV

A series of 2-[3-[2-[(2S)-2-cyano-1-pyrrolidinyl]-2-oxoethylamino]-3-methyl-1-oxobutyl]-based DPP-IV inhibitors with various monocyclic amines were synthesized. The structure–activity relationships (SAR) led to the discovery of potent DPP-IV inhibitors, having IC₅₀ values of <100 nM with excellent selectivity over the closely related enzymes, DPP-II, DPP8, DPP9 and FAP (IC₅₀ > 20 μM). Of these compounds, the analogues 12a, 12h and 12i exhibited a long-lasting ex vivo DPP-IV inhibition in rats.     

Novel tricyclic pyrazolo[1,5-d][1,4]benzoxazepin-5(6H)-one: Design,synthesis, model and use as hMAO-B inhibitors

Based on our recently reported selective hMAO-A inhibitors, on which, the intramolecular cyclization led to a very interesting change of isoform selectivity. A series of selective hMAO-B inhibitors (3a–3u) with novel scaffold of tricyclic pyrazolo[1,5-d][1,4]benzoxazepin-5(6H)-one were designed and synthesized. Compound 3u (IC₅₀ = 221 nM) exhibited the best inhibitory activity and isoform selectivity against hMAO-B, superior to selegiline (IC₅₀ = 321 nM), which is a commercial selective hMAO-B inhibitor used to Parkinson’s disease. Modeling study indicated that the selectivity of our compounds to hMAO-B is determined by at least two residues, i.e., Ile 199 and Cys 172 (or corresponded Phe 208 and Asn 181 of hMAO-A). These data support further studies to assess rational design of more efficiently selective hMAO-B inhibitors.     

Identification of 2,3-dihydro-1H-pyrrolo[3,4-c]pyridine-derived ureas as potent inhibitors of human nicotinamide phosphoribosyltransferase (NAMPT)

Potent nicotinamide phosphoribosyltransferase (NAMPT) inhibitors containing 2,3-dihydro-1H-pyrrolo[3,4-c]pyridine-derived ureas were identified using structure-based design techniques. The new compounds displayed improved aqueous solubilities, determined using a high-throughput solubility assessment, relative to previously disclosed urea and amide-containing NAMPT inhibitors. An optimized 2,3-dihydro-1H-pyrrolo[3,4-c]pyridine-derived compound exhibited potent anti-NAMPT activity (18; BC NAMPT IC₅₀ = 11 nM; PC-3 antiproliferative IC₅₀ = 36 nM), satisfactory mouse PK properties, and was efficacious in a PC-3 mouse xenograft model. The crystal structure of another optimized compound (29; NAMPT IC₅₀ = 10 nM; A2780 antiproliferative IC₅₀ = 7 nM) in complex with the NAMPT protein was also determined.     

Synthesis and anticancer activity of novel 4-morpholino-7,8-dihydro-5H-thiopyrano[4,3-d]pyrimidine derivatives bearing chromone moiety

Herein, we designed and synthesized of a novel series of 7,8-dihydro-5H-thiopyrano[4,3-d]pyrimidine derivatives bearing chromone moiety (10a–j, 13a–j). All the compounds were evaluated for the IC₅₀ values against five cancer cell lines (A549, PC-3, MCF-7, Hela and HepG2). Seven of the target compounds exhibited moderate to excellent cytotoxicity. For these compounds, we tested their inhibitory activities against mTOR kinase, and four of them were tested their inhibitory activities against PI3Kα kinase in further. The results indicated that the optimized compound 10j showed excellent inhibitory activity and cytotoxicity against mTOR kinase, PI3Kα kinase and five cancer cell lines with IC₅₀ values of 1.1 μM, 0.92 μM and 8.77–14.3 μM. Structure–activity relationships (SARs) and docking studies indicated that the thiopyrano[4,3-d]pyrimidine scaffolds exerted little effect on antitumor activities of target compounds. Substitutions of chromone moiety at C-6 position with carboxyl were benefit to the antitumor activities.     

Synthesis and evaluation of 8-amino-[1,2,4]triazolo[4,3-a]pyridin-3(2H)-one derivatives as glycogen synthase kinase-3 (GSK-3) inhibitors

New potent glycogen synthase kinase-3 (GSK-3) inhibitors, 8-amino-[1,2,4]triazolo[4,3-a]pyridin-3(2H)-one derivatives, were designed by modeling, synthesized and evaluated in vitro. Compound 17c showed good potency in enzyme and cell-based assays (IC₅₀ = 111 nM, EC₅₀ = 1.78 μM). Moreover, it has demonstrated desirable water solubility, PK profile, and moderate brain penetration.     

Structure-based design,synthesis, and evaluation of imidazo[1,2-b]pyridazine and imidazo[1,2-a]pyridine derivatives as novel dual c-Met and VEGFR2 kinase inhibitors

To identify compounds with potent antitumor efficacy for various human cancers, we aimed to synthesize compounds that could inhibit c-mesenchymal epithelial transition factor (c-Met) and vascular endothelial growth factor receptor 2 (VEGFR2) kinases. We designed para-substituted inhibitors by using co-crystal structural information from c-Met and VEGFR2 in complex with known inhibitors. This led to the identification of compounds 3a and 3b, which were capable of suppressing both c-Met and VEGFR2 kinase activities. Further optimization resulted in pyrazolone and pyridone derivatives, which could form intramolecular hydrogen bonds to enforce a rigid conformation, thereby producing potent inhibition. One compound of particular note was the imidazo[1,2-a]pyridine derivative (26) bearing a 6-methylpyridone ring, which strongly inhibited both c-Met and VEGFR2 enzyme activities (IC₅₀ = 1.9, 2.2 nM), as well as proliferation of c-Met-addicted MKN45 cells and VEGF-stimulated human umbilical vein endothelial cells (IC₅₀ = 5.0, 1.8 nM). Compound 26 exhibited dose-dependent antitumor efficacy in vivo in MKN45 (treated/control ratio [T/C] = 4%, po, 5 mg/kg, once-daily) and COLO205 (T/C = 13%, po, 15 mg/kg, once-daily) mouse xenograft models.     

Discovery of new [1,4]dioxino[2,3-f]quinazoline-based inhibitors of EGFR including the T790M/L858R mutant

A novel series of 2,3-dihydro-[1,4]dioxino[2,3-f]quinazoline derivatives were designed, synthesized and evaluated as reversible and noncovalent epidermal growth factor receptor (EGFR) inhibitors. Most of the compounds exhibited good potency against EGFR^wt and some showed moderate to excellent potency against EGFR^T790M/L858R mutant. The half-maximal inhibitory concentration (IC₅₀) values of twenty-one compounds against EGFR^wt were less than 50 nM, and those of six compounds were less than 10 nM. The IC₅₀ values of eleven compounds against EGFR^T790M/L858R were less than 100 nM. Among these, compound b1 displayed the most potent inhibitory activity against EGFR^wt (IC₅₀ = 2.0 nM) and EGFR^T790M/L858R (IC₅₀ = 6.9 nM). Compounds with excellent inhibitory activities against EGFR^wt and EGFR^T790M/L858R kinase inhibitory activities showed good antiproliferative activities against H358 and A549 cells. Docking study was performed to position compound b1 into the EGFR active pocket to determine the probable binding conformation.     

Discovery of triazole aminopyrazines as a highly potent and selective series of PI3Kδ inhibitors

A novel class of potent PI3Kδ inhibitors with >1000-fold selectivity against other class I PI3K isoforms is described. Optimization of the substituents on a triazole aminopyrazine scaffold, emerging from an in-house PI3Kα program, turned moderately selective PI3Kδ compounds into highly potent and selective PI3Kδ inhibitors. These efforts resulted in a series of aminopyrazines with PI3Kδ IC₅₀ ? 1 nM in the enzyme assay, some of the most selective PI3Kδ inhibitors published to date, with a cell potency in a JeKo-cell assay of 20–120 nM.     

Design,synthesis, and evaluation of 2-aryl-7-(3′,4′-dialkoxyphenyl)-pyrazolo[1,5-a]pyrimidines as novel PDE-4 inhibitors

Described herein is design, synthesis, and biological evaluation of novel series of 2-aryl-7-(3′,4′-dialkoxyphenyl)-pyrazolo[1,5-a]pyrimidines acting as inhibitors of type 4 phosphodiesterase (PDE4) which is known as a good target for the treatment of asthma and COPD. For this purpose, structure optimization was conducted with the aid of structure-based drug design using the known X-ray crystallography. Also, biological effects of these compounds on the target enzyme were evaluated by using in vitro assays, leading to the potent and selective PDE-4 inhibitor (IC₅₀ < 10 nM).     

New halogenated 3-phenylcoumarins as potent and selective MAO-B inhibitors

With the aim to find out the structural features for the MAO inhibitory activity and selectivity, in the present communication we report the synthesis and pharmacological evaluation of a new series of bromo-6-methyl-3-phenylcoumarin derivatives (with bromo atom in both different benzene rings of the skeleton) with and without different number of methoxy substituent at the 3-phenyl ring. The methoxy substituents were introduced, in this new scaffold, in the meta and/or para positions of the 3-phenyl ring. The synthesized compounds 3–7 were evaluated as MAO-A and B inhibitors using R-(?)-deprenyl (selegiline) and iproniazide as reference inhibitors, showing, most of them, MAO-B inhibitory activities in the low nanomolar range. Compounds 4 (IC₅₀ = 11.05 nM), 5 (IC₅₀ = 3.23 nM) and 6 (IC₅₀ = 7.12 nM) show higher activity than selegiline (IC₅₀ = 19.60 nM) and higher MAO-B selectivity, with more than 9050-fold, 30,960-fold and 14,045-fold inhibition levels, with respect to the MAO-A isoform.     

Synthesis and CYP26A1 inhibitory activity of novel methyl 3-[4-(arylamino)phenyl]-3-(azole)-2,2-dimethylpropanoates

The role of all-trans-retinoic acid (ATRA) in the development and maintenance of many epithelial and neural tissues has raised great interest in the potential of ATRA and related compounds (retinoids) as pharmacological agents, particularly for the treatment of cancer, skin, neurodegenerative and autoimmune diseases. The use of ATRA or prodrugs as pharmacological agents is limited by a short half-life in vivo resulting from the activity of specific ATRA hydroxylases, CYP26 enzymes, induced by ATRA in liver and target tissues. For this reason retinoic acid metabolism blocking agents (RAMBAs) have been developed for treating cancer and a wide range of other diseases.The synthesis, CYP26A1 inhibitory activity and molecular modeling studies of novel methyl 3-[4-(arylamino)phenyl]-3-(azole)-2,2-dimethylpropanoates are presented. From this series of compounds clear SAR can be derived for 4-substitution of the phenyl ring with electron-donating groups more favourable for inhibitory activity. Both the methylenedioxyphenyl imidazole (17, IC₅₀ = 8 nM) and triazole (18, IC₅₀ = 6.7 nM) derivatives were potent inhibitors with additional binding interactions between the methylenedioxy moiety and the CYP26 active site likely to be the main factor. The 6-bromo-3-pyridine imidazole 15 (IC₅₀ = 5.7 nM) was the most active from this series compared with the standards liarozole (IC₅₀ = 540 nM) and R116010 (IC₅₀ = 10 nM).     

Development and characterization of endocannabinoid hydrolases FAAH and MAGL inhibitors bearing a benzotriazol-1-yl carboxamide scaffold

A series of (1H-benzo[d][1,2,3]triazol-1-yl)(4-benzylpiperazin-1-yl)methanones and of (1H-benzo[d][1,2,3]triazol-1-yl)(4-phenylpiperazin-1-yl)methanones has been prepared and tested on human fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL). In the benzylpiperazinyl series, compound 29 (ML30) exhibited an IC₅₀ value of 0.54 nM on MAGL, combined with a 1000-fold selectivity versus FAAH, while compounds 11 and 16 acted as potent dual FAAH-MAGL inhibitors (IC₅₀ <10 nM). In the phenylpiperazinyl series, compounds 37, 38, 42, and 43 displayed IC₅₀ values against MAGL in the nanomolar range, whilst being between one and two orders of magnitude less potent on the FAAH, while compounds 31 and 32 were potent FAAH inhibitors (IC₅₀ <20 nM) and over 12-fold selective versus MAGL. The key structural determinants driving the structure–activity relationships were explored by the minimization of the inhibitors inside the active site of both enzymes.     

α-Tetralone derivatives as inhibitors of monoamine oxidase

In the present study, a series of fifteen α-tetralone (3,4-dihydro-2H-naphthalen-1-one) derivatives were synthesised and evaluated as inhibitors of recombinant human monoamine oxidase (MAO) A and B. The α-tetralone derivatives examined are structurally related to a series of chromone (1-benzopyran-4-one) derivatives which has previously been shown to act as MAO-B inhibitors. The results document that the α-tetralones are highly potent MAO-B inhibitors with all compounds exhibiting IC₅₀ values in the nanomolar range (<78 nM). Although most compounds are selective inhibitors of MAO-B, the α-tetralones are also potent MAO-A inhibitors with ten compounds exhibiting IC₅₀ values in the nanomolar range (<792 nM). The most potent MAO-B inhibitor, 6-(3-iodobenzyloxy)-3,4-dihydro-2H-naphthalen-1-one, exhibits an IC₅₀ value of 4.5 nM with a 287-fold selectivity for MAO-B over the MAO-A isoform, while the most potent MAO-A inhibitor, 6-(3-cyanobenzyloxy)-3,4-dihydro-2H-naphthalen-1-one, exhibits an IC₅₀ value of 24 nM with a 3.25-fold selectivity for MAO-A. Analyses of the structure–activity relationships for MAO inhibition show that substitution on the C6 position of the α-tetralone moiety is a requirement for MAO-A and MAO-B inhibition, and that a benzyloxy substituent on this position is more favourable for MAO-A inhibition than phenylethoxy and phenylpropoxy substitution. For MAO-B inhibition, alkyl and halogen substituents on the meta and para positions of the benzyloxy ring enhance inhibitory potency. It may be concluded that α-tetralone derivatives are promising leads for design of therapies for Parkinson’s disease and depression.     

A hit to lead discovery of novel N-methylated imidazolo-, pyrrolo-, and pyrazolo-pyrimidines as potent and selective mTOR inhibitors

A series of N-7-methyl-imidazolopyrimidine inhibitors of the mTOR kinase have been designed and prepared, based on the hypothesis that the N-7-methyl substituent on imidazolopyrimidine would impart selectivity for mTOR over the related PI3Kα and δ kinases. The corresponding N-Me substituted pyrrolo[3,2-d]pyrimidines and pyrazolo[4,3-d]pyrimidines also show potent mTOR inhibition with selectivity toward both PI3α and δ kinases. The most potent compound synthesized is pyrazolo[4,3-d]pyrimidine 21c. Compound 21c shows a K_i of 2 nM against mTOR inhibition, remarkable selectivity (>2900×) over PI3 kinases, and excellent potency in cell-based assays.     

Synthesis and biological evaluation of pyrido[2,3-d]pyrimidine-2,4-dione derivatives as eEF-2K inhibitors

A small molecule library of pyrido[2,3-d]pyrimidine-2,4-dione derivatives 6–16 was synthesized from 6-amino-1,3-disubstituted uracils 18, characterized, and screened for inhibitory activity against eukaryotic elongation factor-2 kinase (eEF-2K). To understand the binding pocket of eEF-2K, structural modifications of the pyrido[2,3-d]pyrimidine were made at three regions (R¹, R², and R³). A homology model of eEF-2K was created, and compound 6 (A-484954, Abbott laboratories) was docked in the catalytic domain of eEF-2K. Compounds 6 (IC₅₀ = 420 nM) and 9 (IC₅₀ = 930 nM) are found to be better molecules in this preliminary series of pyrido[2,3-d]pyrimidine analogs. eEF-2K activity in MDA-MB-231 breast cancer cells is significantly reduced by compound 6, to a lesser extent by compound 9, and is unaffected by compound 12. Similar inhibitory results are observed when eEF-2K activity is stimulated by 2-deoxy-d-glucose (2-DOG) treatment, suggesting that compounds 6 and 9 are able to inhibit AMPK-mediated activation of eEF-2K to a notable extent. The results of this work will shed light on the further design and optimization of novel pyrido[2,3-d]pyrimidine analogs as eEF-2K inhibitors.     

Design,synthesis and biological evaluation of 4-anilinothieno[2,3-d]pyrimidine-based hydroxamic acid derivatives as novel histone deacetylase inhibitors

A series of 4-anilinothieno[2,3-d]pyrimidine-based hydroxamic acid derivatives as novel HDACs inhibitors were designed, synthesized and evaluated. Most of these compounds displayed good to excellent inhibitory activities against HDAC1, 3, 6. The IC₅₀ values of compound 10r against HDAC1, HDAC3, HDAC6 was 1.14 ± 0.03 nM, 3.56 ± 0.08 nM, 11.43 ± 0.12 nM. Compound 10r noticeably up-regulated the level of histone H3 acetylation compared to the SAHA. Most of the compounds showed the strong anti-proliferative activity against human cancer cell lines including RMPI8226 and HCT-116. The IC₅₀ values of Compounds 10r and 10t against RPMI8226 was 2.39 ± 0.20 μM, 1.41 ± 0.44 μM, respectively, and the HCT-116 was sensitive to the compounds 10h, 10m, 10r, 10w with the IC₅₀ values <1.9 μM.     

Discovery of 8-azabicyclo[3.2.1]octan-3-yloxy-benzamides as selective antagonists of the kappa opioid receptor. Part 1

Initial high throughput screening efforts identified highly potent and selective kappa opioid receptor antagonist 3 (κ IC₅₀ = 77 nM; μ:κ and δ:κ IC₅₀ ratios >400) which lacked CNS exposure in vivo. Modification of this scaffold resulted in development of a series of 8-azabicyclo[3.2.1]octan-3-yloxy-benzamides showing potent and selectivity κ antagonism as well as good brain exposure. Analog 6c (κ IC₅₀ = 20 nM; μ:κ = 36, δ:κ = 415) was also shown to reverse κ-agonist induced rat diuresis in vivo.     

Substituted 4-amino-1H-pyrazolo[3,4-d]pyrimidines as multi-targeted inhibitors of insulin-like growth factor-1 receptor (IGF1R) and members of ErbB-family receptor kinases

This Letter describes the lead discovery, optimization, and biological characterization of a series of substituted 4-amino-1H-pyrazolo[3,4-d]pyrimidines as potent inhibitors of IGF1R, EGFR, and ErbB2. The leading compound 11 showed an IGF1R IC₅₀ of 12 nM, an EGFR (L858R) IC₅₀ of 31 nM, and an ErbB2 IC₅₀ of 11 nM, potent activity in cellular functional and anti-proliferation assays, as well as activity in an in vivo pharmacodynamic assay.     

Benzo[b]furan derivatives induces apoptosis by targeting the PI3K/Akt/mTOR signaling pathway in human breast cancer cells

The PI3K/Akt/mTOR signaling pathway plays a key regulatory function in cell survival, proliferation, migration, metabolism and apoptosis. Aberrant activation of the PI3K/Akt/mTOR pathway is found in many types of cancer and thus plays a major role in breast cancer cell proliferation. In our previous studies, benzo[b]furan derivatives were evaluated for their anticancer activity and the lead compounds identified were 26 and 36. These observations prompted us to investigate the molecular mechanism and apoptotic pathway of these lead molecules against breast cancer cells. Benzo[b]furan derivatives (26 and 36) were evaluated for their antiproliferative activity against human breast cancer cell lines MCF-7 and MDA MB-231. These compounds (26 and 36) have shown potent efficiency against breast cancer cells (MCF-7) with IC₅₀ values 0.057 and 0.051 μM respectively. Cell cycle analysis revealed that these compounds induced cell cycle arrest at G2/M phase in MCF-7 cells. Western blot analysis revealed that these compounds inhibit the PI3K/Akt/mTOR signaling pathway and induced mitochondrial mediated apoptosis in human breast cancer cells (MCF-7).     

Functionalized 3-amino-imidazo[1,2-a]pyridines: A novel class of drug-like Mycobacterium tuberculosis glutamine synthetase inhibitors

3-Amino-imidazo[1,2-a]pyridines have been identified as a novel class of Mycobacterium tuberculosis glutamine synthetase inhibitors. Moreover, these compounds represent the first drug-like inhibitors of this enzyme. A series of compounds exploring structural diversity in the pyridine and phenyl rings have been synthesized and biologically evaluated. Compound 4n was found to be the most potent inhibitor (IC₅₀ = 0.38 ± 0.02 μM). This compound was significantly more potent than the known inhibitors, l-methionine-SR-sulfoximine and phosphinothricin.