5,6-Diphenylpyridazine derivatives as acyl-CoA:cholesterol acyltransferase inhibitors

Synthesis and evaluation of novel thiazole moiety-containing compounds as antibreast cancer agents

Progesterone receptor (PR) agonists represent pivotal agents in trapping breast cancer cells through modulating the expression of estrogen receptor (ER). The present investigation aimed to test three novel thiadiazole-containing compounds as antibreast cancer agents. Test compounds were synthesized and abbreviated as 2-{(5-amino-1, 3, 4-thiazole-2-yl) amino}-4-(4-chloro-3-methylphenyl)-4-oxobutanoic acid (TAB), 4-(4-chloro-3-methylphenyl)-4-oxo 2-[(5-sulfanyl-1, 3, 4-thiadiazol-2-yl)] sulfanyl-butanoic acid (TSB) and 4-(4-chloro-3-methylphenyl)-4-oxo 2-[(5-sulfanyl-1, 3, 4-thiadiazol-2-yl)] sulphonyl-botanic acid (TSSB). Molecular docking of the test compounds with PR was simulated. The IC 50 of the test compounds against both Michigan cancer foundation-7 (MCF-7) and HepG2 was determined. Ehrlich solid tumor (EST) was grown in the right thigh of the mouse as a model of breast cancer in vivo . Hepatic and renal functions, besides hematological indicators, were tested. The expression of ER and ER genes in EST was determined using real-time PCR. Immunohistochemistry was carried out for the determination of Ki-67 and cyclin-dependent kinase 1 (CDK-1) in EST. Our results revealed that TAB, TSB and TSSB reduced Ehrlich tumor size by 48, 64 and 52%, respectively, compared to the EST control group. The docking scores achieved by TAB, TSB and TSSB with PR were -9.29, -9.41 and -9.24 kcal/mol, respectively. The most potent compound against MCF-7 was TSB, with an IC 50 of 3.9 g/ml. The administration of test compounds suppressed Ki-67 and CDK1, and the best effect was observed at TSB. Our findings suggest that test compounds are applicants to be antibreast cancer agents.

Targeting Sterol O-Acyltransferase/Acyl-CoA:Cholesterol Acyltransferase (ACAT): A Perspective on Small-Molecule Inhibitors and Their Therapeutic Potential

Sterol O-acyltransferase (SOAT) is a membrane-bound enzyme that aids the esterification of cholesterol and fatty acids to cholesterol esters. SOAT has been studied extensively as a potential drug target, since its inhibition can serve as an alternative to statin therapy. Two SOAT isozymes that have discrete functions in the human body, namely, SOAT1 and SOAT2, have been characterized. Over three decades of research has focused on candidate SOAT1 inhibitors with unsatisfactory results in clinical trials. Recent research has focused on targeting SOAT2 selectively. In this perspective, we summarize the literature covering various SOAT inhibitory agents and discuss the design, structural requirements, and mode of action of SOAT inhibitors.

Isoxazolo[3,4-d]pyridazinones positively modulate the metabotropic glutamate subtypes 2 and 4

Isoxazolo[3,4-d] pyridazinones ([3,4-d]s) are selective positive modulators of the metabotropic glutamate receptors (mGluRs) subtypes 2 and 4, with no functional cross reactivity at mGluR1a, mGLuR5 or mGluR8. Modest binding for two of the [3,4-d]s is observed at the allosteric fenobam mGluR5 site, but not sufficient to translate into a functional effect. The structure activity relationship (SAR) for mGluR2 and mGluR4 are distinct: the compounds which select for mGluR2 all contain fluorine on the N-6 aryl group. Furthermore, the [3,4-d]s in this study showed no significant binding at inhibitory GABAA, nor excitatory NMDA receptors, and previously we had disclosed that they lack significant activity at the System Xc-Antiporter. A homology model based on Conn's mGluR1 crystal structure was examined, and suggested explanations for a preference for allosteric over orthosteric binding, subtype selectivity, and suggested avenues for optimization of efficacy as a reasonable working hypothesis.

Vicinal diaryl azole-based urea derivatives as potential cholesterol lowering agents acting through inhibition of SOAT enzymes

A novel series of vicinal diaryl azole-urea derivatives were synthesized and evaluated for their potential to inhibit SOAT enzyme. Among the reported compounds, compound (12d) emerged as the most potent compound with an IC₅₀ value of 2.43 μM. In polaxamer-407 induced lipoprotein lipase inhibition model, compound (12d) reduced triglyceride turnover in vivo. Compound (12d) also showed dose-dependent prevention of serum total cholesterol and prevention of LDL-C elevation at a dose of 30 mg/kg. Furthermore, compound (12d) showed potential to stop falling levels of serum HDL-C dose-dependently and improved the atherogenic index. Effect of 12d on body weight, plaque formation and development of atherogenic lesions were studied. Toxicological study of compound (12d) indicated that at a dose of 2000 mg/kg, 12d was devoid of any signs of toxicity or mortality.

Two Efficient One-Pot Approaches for Regioselective Synthesis of New 3-Arylpyridazino[4,3-c]quinolin-5(6H)-ones

Two efficient regioselective approaches for the one-pot synthesis of 3-arylpyridazino[4,3-c]quinolin-5(6H)-one derivatives are reported, by the three-component reaction of arylglyoxal monohydrates, quinoline-2,4-diol, and hydrazinium dihydrochloride or hydrazine hydrate in ethanol and pyridine. In ethanol, the reactions were catalyzed by 1,4-diazobicyclo[2,2,2]octane. The features of both procedures are high regioselectivity, mild reaction conditions, good to high yields, and operational simplicity.

Microwave accelerated synthesis of isoxazole hydrazide inhibitors of the system xc- transporter: Initial homology model

Microwave accelerated reaction system (MARS) technology provided a good method to obtain selective and open isoxazole ligands that bind to and inhibit the Sxc- antiporter. The MARS provided numerous advantages, including: shorter time, better yield and higher purity of the product. Of the newly synthesized series of isoxazoles the salicyl hydrazide 6 exhibited the highest level of inhibitory activity in the transport assay. A homology model has been developed to summarize the SAR results to date, and provide a working hypothesis for future studies.

Discovery of novel acyl coenzyme a: cholesterol acyltransferase inhibitors: pharmacophore-based virtual screening, synthesis and pharmacology

The present study describes ligand-based pharmacophore modeling of a series of structurally diverse acyl coenzyme A cholesterol acyltransferase inhibitors. Quantitative pharmacophore models were generated using HypoGen module of Discovery Studio 2.1, whereby the best pharmacophore model possessing two hydrophobic, one ring aromatic, and one hydrogen bond acceptor feature for inhibition of acyl coenzyme A cholesterol acyltransferase showed a very good correlation coefficient (r = 0.942) along with satisfactory cost analysis. Hypo1 was also validated by test set and cross-validation methods. Developed models were found to be predictive as indicated by low error values for test set molecules. Virtual screening against Maybridge database using Hypo1 was performed. The two most potent compounds (47 and 48; predicted IC₅₀ = 1 nM) of the retrieved hits were synthesized and biologically evaluated. These compounds showed 86% and 88% inhibition of acyl coenzyme A cholesterol acyltransferase (at 10 μg/mL) with IC₅₀ value of 3.6 and 2.5 nM, respectively. As evident from the close proximity of biological data to the predicted values, it can be concluded that the generated model (Hypo1) is a reliable and useful tool for lead optimization of novel acyl coenzyme A cholesterol acyltransferase inhibitors.

Biphenyl versus phenylpyridazine derivatives: the role of the heterocycle in a series of acyl-CoA:cholesterol acyl transferase inhibitors

A series of alkylamido- ( 1) and alkylaminobiphenyl ( 2) derivatives were synthesized as possible bioisosters of the reported ACAT inhibitors phenylpyridazine analogues ( I). Both 1 and 2 were tested on the human ACAT-1 and ACAT-2 isoforms. The amino derivatives 2 were found to be inactive, contrary to the related pyridazine derivatives. By contrast, the ortho -substituted amides 1a and 1d showed an interesting activity. These results support the essential role of the pyridazine nucleus. Modeling studies were also performed.

Synthesis and biological evaluation of unprecedented classes of spiro-beta-lactams and azido-beta-lactams as acyl-CoA:cholesterol acyltransferase inhibitors

Unprecedented classes of four- and five-membered hydroxyl-spiro-beta-lactams and hydroxyl-azido-beta-lactams were prepared via regioselective ring opening of hydroxyl-epoxides. The potential of these particular beta-lactams as biologically active compounds has been confirmed by the results obtained in ACAT inhibition assays.

3-Heptylamino-5-Phenylpyridazine Derivatives as Analogues of Acyl-CoA: Cholesterol Acyltransferase Inhibitors Containing theN-Heptyl-N′-Arylureidic Moiety

A series of novel Acyl-CoA: cholesterol acyltransferase (ACAT) inhibitors 8a-f was synthesized; the substances were characterized by the presence of a 2,5-dimethylpyrazin-3-yl moiety at one end and a 3-heptylamino-5-phenylpyridazine system at the other one, linked through linear alkyl spacers of different length. The new derivatives were designed based on the hypothesis that the 3-amino-5-phenylpyridazine moiety could mimic the aryl substituted urea, which was present in a number of ACAT inhibitors previously described. The choice of the 2,5-dimethylpyrazin-3-yl substituent was supported by a preliminary investigation, which indicated that this moiety is the most powerful in conferring ACAT inhibitory properties to the new series. The pharmacological results proved the idea to be sound. Finally, compounds 9a-c, lacking the phenylpyridazine moiety were prepared and tested to further strengthen our hypothesis.

Mono- or diphenylpyridazines connected to N-(2,4-difluorophenyl)-N'-heptylurea as acyl-CoA:cholesterol acyltransferase inhibitors

Mono- and diphenylpyridazine ureido derivatives, structurally related to DuP 128, were synthesized and tested for their inhibitory activity against ACAT isolated from rat liver microsomes. Several compounds displayed ACAT inhibition in the micromolar range. The amino derivatives 4a-c were also tested against hACAT-1 and hACAT-2 isoforms. They retained the same trend shown in the previous assay. Modeling studies on representative terms were performed. Significant similarities between the geometrical features of the model DuP 128 and the most active pyridazine derivatives were observed.

Hydrophobic Molecular Similarity from MST Fractional Contributions to the Octanol/water Partition Coefficient

The use of a recently proposed hydrophobic similarity index for the alignment of molecules and the prediction of their differences in biological activity is described. The hydrophobic similarity index exploits atomic contributions to the octanol/water transfer free energy, which are evaluated by means of the fractional partitioning scheme developed within the framework of the Miertus-Scrocco-Tomasi continuum model. Those contributions are used to define global and local measures of hydrophobic similarity. The suitability of this computational strategy is examined for two series of compounds (ACAT inhibitors and 5-HT3 receptor agonists), which are aligned to maximize the global hydrophobic similarity using a Monte Carlo-simulated protocol. Indeed, the concept of local hydrophobic similarity is used to explore structure-activity relationships in a series of COX-2 inhibitors. Inspection of the 3D distribution of hydrophobic/hydrophilic contributions in the aligned molecules is valuable to identify regions of very similar hydrophobicity, which can define pharmacophoric recognition patterns. Moreover, low similar regions permit to identify structural elements that modulate the differences in activity between molecules. Finally, the quantitative relationships found between the pharmacological activity and the hydrophobic similarity index points out that not only the global hydrophobicity, but its 3D distribution, is important to gain insight into the activity of molecules.

Novel 3-arylamino- and 3-cycloalkylamino-5, 6-diphenyl-pyridazines active as ACAT inhibitors

A new series of pyridazine derivatives, structurally related to the previously reported ACAT inhibitors 3-(cyclo)alkylamino-5, 6-diphenyl-pyridazines, were synthesized and tested for their inhibitory properties. Substitution of the 3-alkylamino chain with a phenylamino group maintains activity. In contrast, the presence of either substituents on the phenylamino group or aliphatic rings having more or less than six carbon atoms lowers it.