Synthesis and biological evaluation of novel benzo[c][1,2,5]thiadiazol-5-yl and thieno[3,2-c]- pyridin-2-yl imidazole derivatives as ALK5 inhibitors

Transforming growth factor (TGF-β), a key mediator of tumor growth and metastasis, has been recognized as an important cancer drug target. A series of benzo[c][1,2,5]thiadiazol-5-yl imidazoles (14a–g) and thieno[3,2-c]-pyridin-2-yl imidazoles (20a–g) were designed, synthesized, and evaluated for their activin receptor-like kinase 5 (ALK5) activities. Among these compounds, 14c showed the highest activity (IC₅₀ = 0.008 μM) against ALK5 kinase, which was 16.1-fold and 1.8-fold higher than those of positive control compounds LY-2157299 (IC₅₀ = 0.129 μM) and EW-7197 (IC₅₀ = 0.014 μM), respectively. Compound 14g (350) showed the highest selectivity index of ALK5 against p38α MAP kinase, which was significantly higher than that of positive control compounds LY-2157299 (4) and EW-7197 (211). The inhibitory effects of compound 14c on TGF-β-induced Smad signaling and cell motility were studied in SPC-A1, HepG2 and HUVEC cells using western blot analysis and wound healing assay. ADMET prediction analysis showed that compounds 14c and 14g had good pharmacokinetics and drug-likeness behaviors.     

3-(Cyclopropylmethyl)-7-((4-(4-[11C]methoxyphenyl)piperidin-1-yl)methyl)-8-(trifluoromethyl)-[1,2,4]triazolo[4,3-a]pyridine: Synthesis and preliminary evaluation for PET imaging of metabotropic glutamate receptor subtype 2

Selective metabotropic glutamate receptor 2 (mGluR2) inhibitors have been demonstrated to show therapeutic effects by improving alleviating symptoms of schizophrenic patients in clinical studies. Herein we report the synthesis and preliminary evaluation of a ¹¹C-labeled positron emission tomography (PET) tracer originating from a mGluR2 inhibitor, 3-(cyclopropylmethyl)-7-((4-(4-methoxyphenyl)piperidin-1-yl)methyl)-8-(trifluoromethyl)-[1,2,4]triazolo[4,3-a]pyridine (CMTP, 1a). [¹¹C]CMTP ([¹¹C]1a) was synthesized by O-[¹¹C]methylation of desmethyl precursor 1b with [¹¹C]methyl iodide in 19.7 ± 8.9% (n = 10) radiochemical yield (based on [¹¹C]CO₂) with >98% radiochemical purity and >74 GBq/μmol molar activity. Autoradiography study showed that [¹¹C]1a possessed moderate in vitro specific binding to mGluR2 in the rat brain, with a heterogeneous distribution of radioactive accumulation in the mGluR2-rich brain tissue sections, such as the cerebral cortex and striatum. PET study indicated that [¹¹C]1a was able to cross the blood–brain barrier and enter the brain, but had very low specific binding in the rat brain. Further optimization for the chemical structure of 1a is necessary to increase binding affinity to mGluR2 and then improve in vivo specific binding in brain.     

In vitro and in vivo pharmacological profile of 4-(4-fluorobenzylidene)-1-[2-[5-(4-fluorophenyl)-1H-pyrazol-4-yl] ethyl] piperidine (NRA0161)

Atypical antipsychotic properties of 4-(4-fluorobenzylidene)-1-[2-[5-(4-fluorophenyl)-1H-pyrazol-4-yl]ethyl] piperidine (NRA0161) were investigated by in vitro receptor affinities, in vivo receptor occupancies and findings were compared with those of risperidone and haloperidol in rodent behavioral studies. In in vitro receptor binding studies, NRA0161 has a high affinity for human cloned dopamine D(4) and 5-HT(2A) receptor with Ki values of 1.00 and 2.52 nM, respectively. NRA0161 had a relatively high affinity for the alpha(1) adrenoceptor (Ki; 10.44 nM) and a low affinity for the dopamine D(2) receptor (Ki; 95.80 nM). In in vivo receptor binding studies, NRA0161 highly occupied the 5-HT(2A) receptor in rat frontal cortex. In contrast, NRA0161 did not occupy the striatal D(2) receptor. In behavioral studies, NRA0161, risperidone and haloperidol antagonized the locomotor hyperactivity in mice, as induced by methamphetamine (MAP). At a higher dosage, NRA0161, risperidone and haloperidol dose-dependently antagonized the MAP-induced stereotyped behavior in mice and NRA0161 dose-dependently and significantly induced catalepsy in rats. The ED(50) value in inhibiting the MAP-induced locomotor hyperactivity was 30 times lower than that inhibiting the MAP-induced stereotyped behavior and 50 times lower than that which induced catalepsy.These findings suggest that NRA0161 may have atypical antipsychotic activities yet without producing extrapyramidal side effects.     

Development of benzo[d]oxazol-2(3H)-ones derivatives as novel inhibitors of Mycobacterium tuberculosis InhA

A series of twenty seven substituted 2-(2-oxobenzo[d]oxazol-3(2H)-yl)acetamide derivatives were designed based on our earlier reported Mycobacterium tuberculosis (MTB) enoyl-acyl carrier protein reductase (InhA) lead. Compounds were evaluated for MTB InhA inhibition study, in vitro activity against drug-sensitive and -resistant MTB strains, and cytotoxicity against RAW 264.7 cell line. Among the compounds tested, 2-(6-nitro-2-oxobenzo[d]oxazol-3(2H)-yl)-N-(5-nitrothiazol-2-yl)acetamide (30) was found to be the most promising compound with IC₅₀ of 5.12 ± 0.44 μM against MTB InhA, inhibited drug sensitive MTB with MIC 17.11 μM and was non-cytotoxic at 100 μM. The interaction with protein and enhancement of protein stability in complex with compound 30 was further confirmed biophysically by differential scanning fluorimetry.     

4-N-Hydroxy-4-[1-(sulfonyl)piperidin-4-yl]-butyramides as HDAC inhibitors

A series of N-substituted 4-alkylpiperidine hydroxamic acids, corresponding to the basic structure of histone deacetylase (HDAC) inhibitors (zinc binding moiety-linker-capping group) has been previously reported by our group. Linker length and aromatic capping group connection were systematically varied to find the optimal geometric parameters. A new series of submicromolar inhibitors was thus identified, which showed antiproliferative activity on HCT-116 colon carcinoma cells. We report here the second part of the strategy used in our research group to find a new class of HDAC inhibitors, namely the SAR study for the compounds bearing a sulfonyl group on the piperidine nitrogen. In the present work, we have considered both sulfonamides and sulfonyl ureas.     

3-[2-Amino-2-imidazolin-4(5)-yl]alanine (enduracididine) and 2-[2-amino-2-imidazolin-4(5)-yl] acetic acid in seeds of Lonchocarpus sericeus

3-[2-Amino-2-imidazolin-4(5)-yl]alanine (enduracididine) and 2-[2-amino-2-imidazolin-4(5)-yl] acetic acid have been isolated from seeds of Lonchocarpus sericeus. The concentration of each compound was ca 0.5 % of the fresh seed weight.     

Synthesis,anticancer and antioxidant activities of some novel N-(benzo[d]oxazol-2-yl)-2-(7- or 5-substituted-2-oxoindolin-3-ylidene) hydrazinecarboxamide derivatives

A series of N-(benzo[d]oxazol-2-yl)-2-(7- or 5-substituted-2-oxoindolin-3-ylidene) hydrazinecarboxamide derivatives were synthesized by treating N-(benzoxazol-2-yl)hydrazinecarboxamide with different isatin derivatives. The newly synthesized compounds were characterized on the basis of spectral analyses. All the synthesized derivatives (Va-l) were screened for anticancer and antioxidant activities. The results showed the anticancer activity of test compounds against HeLa, IMR-32 and MCF-7 cancer cell lines using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. All the synthetic compounds produced a dose-dependant inhibition of growth of the cells. The IC₅₀ values of some compounds were comparable with standard anticancer agent, cisplatin. All the title compounds effectively scavenged the free radical, α,α-diphenyl-β-picryl hydrazyl. The test compounds having substitution with different halides (electron withdrawing groups) at C5 position showed more potent anticancer and antioxidant activities than those at C7 position. These results indicate that C5-substituted derivatives may be useful for developing antioxidant agents that play a protective role in many pathological conditions such as cancer, diabetes and so on.     

Synthesis, anticancer and antioxidant activities of some novel N-(benzo[d]oxazol-2-yl)-2-(7- or 5-substituted-2-oxoindolin-3-ylidene) hydrazinecarboxamide derivatives

A series of N-(benzo[d]oxazol-2-yl)-2-(7- or 5-substituted-2-oxoindolin-3-ylidene) hydrazinecarboxamide derivatives were synthesized by treating N-(benzoxazol-2-yl)hydrazinecarboxamide with different isatin derivatives. The newly synthesized compounds were characterized on the basis of spectral analyses. All the synthesized derivatives (Va-l) were screened for anticancer and antioxidant activities. The results showed the anticancer activity of test compounds against HeLa, IMR-32 and MCF-7 cancer cell lines using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. All the synthetic compounds produced a dose-dependant inhibition of growth of the cells. The IC(50) values of some compounds were comparable with standard anticancer agent, cisplatin. All the title compounds effectively scavenged the free radical, α,α-diphenyl-β-picryl hydrazyl. The test compounds having substitution with different halides (electron withdrawing groups) at C5 position showed more potent anticancer and antioxidant activities than those at C7 position. These results indicate that C5-substituted derivatives may be useful for developing antioxidant agents that play a protective role in many pathological conditions such as cancer, diabetes and so on.     

Discovery of novel 2-[2-(3-hydroxy-pyridin-2-yl)-thiazol-4-yl]-acetamide derivatives as HIF prolyl 4-hydroxylase inhibitors; SAR,synthesis and modeling evaluation

The design, synthesis, and capacity to inhibit HIF prolyl 4-hydroxylases (PHDs) are described for 2-[2-(3-hydroxy-pyridin-2-yl)-thiazol-4-yl]-acetamide analogs. These analogs revealed two kinds of novel scaffolds as PHD2 inhibitors. Synthetic routes were developed for the preparation of their analogs containing the new scaffolds. In addition, the structure–activity relationship (SAR) of the 2-[2-(3-hydroxy-pyridin-2-yl)-thiazol-4-yl]-acetamide derivatives and their biological activities were reported. The complex structure of compound 18 with PHD2 was also obtained for the purpose of more efficient lead optimization.     

5-(2-amino-pyrimidin-4-yl)-1H-pyrrole and 2-(2-amino-pyrimidin-4-yl)-1,5,6,7-tetrahydro-pyrrolo[3,2-c]pyridin-4-one derivatives as new classes of selective and orally available Polo-like kinase 1 inhibitors

The discovery and characterization of two new chemical classes of potent and selective Polo-like kinase 1 (PLK1) inhibitors is reported. For the most interesting compounds, we discuss the biological activities, crystal structures and preliminary pharmacokinetic parameters. The more advanced compounds inhibit PLK1 in the enzymatic assay at the nM level and exhibit good activity in cell proliferation on A2780 cells. Furthermore, these compounds showed high levels of selectivity on a panel of unrelated kinases, as well as against PLK2 and PLK3 isoforms. Additionally, the compounds show acceptable oral bioavailability in mice making these inhibitors suitable candidates for further in vivo activity studies.     

Discovery of 6-[5-(4-fluorophenyl)-3-methyl-pyrazol-4-yl]-benzoxazin-3-one derivatives as novel selective nonsteroidal mineralocorticoid receptor antagonists

In the course of our study on selective nonsteroidal mineralocorticoid receptor (MR) antagonists, a series of novel benzoxazine derivatives possessing an azole ring as the core scaffold was designed for the purpose of attenuating the partial agonistic activity of the previously reported dihydropyrrol-2-one derivatives. Screening of alternative azole rings identified 1,3-dimethyl pyrazole 6a as a lead compound with reduced partial agonistic activity. Subsequent replacement of the 1-methyl group of the pyrazole ring with larger lipophilic side chains or polar side chains targeting Arg817 and Gln776 increased MR binding activity while maintaining the agonistic response at the lower level. Among these compounds, 6-[1-(2,2-difluoro-3-hydroxypropyl)-5-(4-fluorophenyl)-3-methyl-1H-pyrazol-4-yl]-2H-1,4-benzoxazin-3(4H)-one (37a) showed highly potent in vitro activity, high selectivity versus other steroid hormone receptors, and good pharmacokinetic profiles. Oral administration of 37a in deoxycorticosterone acetate-salt hypertensive rats showed a significant blood pressure-lowering effect with no signs of antiandrogenic effects.     

Discovery of a novel sub-class of ROMK channel inhibitors typified by 5-(2-(4-(2-(4-(1H-Tetrazol-1-yl)phenyl)acetyl)piperazin-1-yl)ethyl)isobenzofuran-1(3H)-one

A sub-class of distinct small molecule ROMK inhibitors were developed from the original lead 1. Medicinal chemistry endeavors led to novel ROMK inhibitors with good ROMK functional potency and improved hERG selectivity. Two of the described ROMK inhibitors were characterized for the first in vivo proof-of-concept biology studies, and results from an acute rat diuresis model confirmed the hypothesis that ROMK inhibitors represent new mechanism diuretic and natriuretic agents.     

Design,synthesis, and evaluation of N-(4-(4-phenyl piperazin-1-yl)butyl)-4-(thiophen-3-yl)benzamides as selective dopamine D3 receptor ligands

As part of our on-going effort to explore the role of dopamine receptors in drug addiction and identify potential novel therapies for this condition, we have a identified a series of N-(4-(4-phenyl piperazin-1-yl)butyl)-4-(thiophen-3-yl)benzamide D₃ ligands. Members of this class are highly selective for D₃ versus D₂, and we have identified two compounds (13g and 13r) whose rat in vivo IV pharmacokinetic properties that indicate that they are suitable for assessment in in vivo efficacy models of substance use disorders.     

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.     

Discovery of 5-(5-fluoro-1H-pyrrolo[2,3-b]pyridin-3-yl)pyrazin-2(1H)-one derivatives as new potent PB2 inhibitors

PB2 is an important subunit of influenza RNA-dependent RNA polymerase (RdRP) and has been recognized as a promising target for the treatment of influenza. We herein report the discovery of a new series of PB2 inhibitors containing the skeleton 5-(5-fluoro-1H-pyrrolo[2,3-b]pyridin-3-yl)pyrazin-2(1H)-one. Compound 12b is the most potent one, which showed K_D values of 0.11 μM and 0.19 μM in surface plasmon resonance (SPR) and isothermal titration calorimetry (ITC) assays, respectively. In antiviral activity and cellular cytotoxicity assays, compound 12b showed an EC₅₀ value of 1.025 μM and a CC₅₀ value greater than 100 μM. Molecular docking was also used to predict the binding mode of 12b with PB2. Collectively, this study provides a promising lead compound for subsequent anti-influenza drug discovery targeting PB2.     

Design and synthesis of (5-amino-1, 2, 4-triazin-6-yl)(2-(benzo[d] isoxazol-3-yl) pyrrolidin-1-yl)methanone derivatives as sodium channel blocker and anticonvulsant agents

Abstract

A series of novel (5-amino-3-substituted-1, 2, 4-triazin-6-yl) (2-(6-halo-substituted benzo[d]isoxazol-3-yl) pyrrolidin-1-yl) methanone 5a–5r was synthesized. Their anticonvulsant activities were evaluated by the maximal electroshock (MES) test and neurotoxicity was evaluated by the rotorod test. The MES test showed that (5-amino-3-phenyl-1, 2, 4-triazin-6-yl)(2-(6-fluorobenzo[d]isoxazol-3-yl) pyrrolidin-1-yl) methanone 5c was found to be the most potent compound with ED₅₀ value of 6.20?mg/kg (oral/rat) and a protective index (PI?=?ED₅₀/TD₅₀) value of >48.38, which was much higher than the PI of the reference drug phenytoin. To explain the possible mechanism of action of selected derivatives 5b, 5c, 5i and 5o, their influence on sodium channel was evaluated in vitro.     

Synthesis and SAR studies of 5-(pyridin-4-yl)-1,3,4-thiadiazol-2-amine derivatives as potent inhibitors of Bloom helicase

Human cells utilize a variety of complex DNA repair mechanisms in order to combat constant mutagenic and cytotoxic threats from both exogenous and endogenous sources. The RecQ family of DNA helicases, which includes Bloom helicase (BLM), plays an important function in DNA repair by unwinding complementary strands of duplex DNA as well as atypical DNA structures such as Holliday junctions. Mutations of the BLM gene can result in Bloom syndrome, an autosomal recessive disorder associated with cancer predisposition. BLM-deficient cells exhibit increased sensitivity to DNA damaging agents indicating that a selective BLM inhibitor could be useful in potentiating the anticancer activity of these agents. In this work, we describe the medicinal chemistry optimization of the hit molecule following a quantitative high-throughput screen of >355,000 compounds. These efforts lead to the identification of ML216 and related analogs, which possess potent BLM inhibition and exhibit selectivity over related helicases. Moreover, these compounds demonstrated cellular activity by inducing sister chromatid exchanges, a hallmark of Bloom syndrome.     

Discovery,synthesis and molecular substantiation of N-(benzo[d]thiazol-2-yl)-2-hydroxyquinoline-4-carboxamides as anticancer agents

The effort was taken to develop a series of benzothiazole and quinoline fused bioactive compounds obtained through a four-step synthetic route using a range of substituted acetoacetanilides. Achieved N-(benzo[d]thiazol-2-yl)-2-hydroxyquinoline-4-carboxamides (6a-l) were produced up to 96% of yield while the eco-friendly p-TSA used as a catalyst. Further, the anticancer activity of these compounds was determined using a range of cancer cell lines starting from MCF-7 (Breast cancer), HCT-116 (Colon cancer), PC-3 & LNCaP (Prostate) and SK-HEP-1 (Liver cancer). Present study compounds were also testified for antioxidant properties prior to anticancer studies since the Reactive Oxygen Species (ROS) being vital in cancer development. To determine the cell membrane stability effects of the compounds, human red blood cells (HRBC) based membrane protection assay was determined. In the results, compounds 6a-l were able to produce a dominated result values over PC3 cell lines (Prostate cancer) than the other cell lines used in this study. Since the connectivity of human germ cell alkaline phosphatase (hGC-ALP) in the development of prostate cancer is known, the most active compounds were evaluated for the hGC-ALP inhibition in order to ensure a mechanism of anticancer action of these compounds. The mode of interaction and binding affinity of these compounds was also investigated by a molecular docking study. In the results, 6d, 6i, 6k, and 6l were found with least IC₅₀ values <0.075 µM and highest relative activity of 92%, 90%, and 96% respectively. The need for further animal model evaluation and pre-clinical studies recognized.     

1-[4-(1H-Benzoimidazol-2-yl)-phenyl]-3-[4-(1H-benzoimidazol-2-yl)-phenyl]-urea derivatives as small molecule heparanase inhibitors

A novel class of 1-[4-(1H-benzoimidazol-2-yl)-phenyl]-3-[4-(1H-benzoimidazol-2-yl)-phenyl]-ureas are described as potent inhibitors of heparanase. Among them are 1,3-bis-[4-(1H-benzoimidazol-2-yl)-phenyl]-urea (7a) and 1,3-bis-[4-(5,6-dimethyl-1H-benzoimidazol-2-yl)-phenyl]-urea (7d), which displayed good heparanase inhibitory activity (IC(50) 0.075-0.27 microM). Compound 7a showed good efficacy in a B16 metastasis model.     

3-[2-(Aminomethyl)-5-[(pyridin-4-yl)carbamoyl]phenyl] benzoates as soft ROCK inhibitors

Clinical development of ROCK inhibitors has so far been limited by systemic or local ROCK-associated side effects. A soft drug approach, which involves predictable metabolic inactivation of an active compound to a nontoxic metabolite, could represent an attractive way to obtain ROCK inhibitors with improved tolerability. We herein report the design and synthesis of a new series of soft ROCK inhibitors structurally related to the ROCK inhibitor Y-27632. These inhibitors contain carboxylic ester moieties which allow inactivation by esterases. While the parent esters display strong activity in enzymatic (ROCK2) and cellular (MLC phosphorylation) assays, their corresponding carboxylic acid metabolites have negligible functional activity. Compound 32 combined strong efficacy (ROCK2 IC₅₀ = 2.5 nM) with rapid inactivation in plasma (t_1/2 <5′). Compound 32 also demonstrated in vivo efficacy when evaluated as an IOP-lowering agent in ocular normotensive New-Zealand White rabbits, without ocular side effects.