Synthesis of New Pyrrolo[1,2-a]quinoxaline Derivatives as Potential Inhibitors of Akt Kinase

Akt kinases are attractive targets for small molecule drug discovery because of their key role in tumor cell survival/proliferation and their overexpression/activation in many human cancers. Recent efforts in the development and biological evaluation of small molecule inhibitors of Akt have led to the identification of novel Akt kinase inhibitors, based on a quinoxaline or pyrazinone scaffold. A series of new substituted pyrrolo[1,2-a]quinoxaline derivatives, structural analogues of these active quinoxaline or pyrazinone pharmacophores, was synthesized from various substituted 2-nitroanilines or 1,2-phenylenediamine via multistep heterocyclization process. These new compounds were tested for their in vitro ability to inhibit the proliferation of the human leukemic cell lines K562, U937 and HL60, and the breast cancer cell line MCF7. Three of these human cell lines (K562, U937 and MCF7) exhibited an active phosphorylated Akt form. The most promising active pyrroloquinoxalines were found to be 1a that inhibited K562 cell line proliferation with an IC₅₀ of 4.5 μM, and 1h that inhibited U937 and MCF7 cell lines with IC₅₀ of 5 and 8 μM, respectively. These two candidates exhibited more potent activities than the reference inhibitor A6730.     

Synthesis of highly potent and selective hetaryl ureas as integrin alpha(V)beta3-receptor antagonists

Solid-phase synthesis and SAR of integrin alpha(V)beta3-receptor antagonists containing a urea moiety as non-basic guanidine mimetic are described. The most potent compounds exhibited IC(50) values towards alpha(V)beta3 in the nanomolar range and high selectivity versus related integrins like alpha(IIb)beta3. For selected examples efficacy in functional cellular assays is demonstrated.     

OPA1 (dys)functions

Mitochondrial morphology varies according to cell type and cellular context from an interconnected filamentous network to isolated dots. This morphological plasticity depends on mitochondrial dynamics, a balance between antagonistic forces of fission and fusion. DRP1 and FIS1 control mitochondrial outer membrane fission and Mitofusins its fusion. This review focuses on OPA1, one of the few known actors of inner membrane dynamics, whose mutations provoke an optic neuropathy. Since its first identification in 2000 the characterization of the functions of OPA1 has made rapid progress thus providing numerous clues to unravel the pathogenetic mechanisms of ADOA-1.     

Molecular docking and 3D-QSAR studies of HIV-1 protease inhibitors

HIV-1 protease is an obligatory enzyme in the replication process of the HIV virus. The abundance of structural information on HIV-1PR has made the enzyme an attractive target for computer-aided drug design strategies. The daunting ability of the virus to rapidly generate resistant mutants suggests that there is an ongoing need for new HIV-1PR inhibitors with better efficacy profiles and reduced toxicity. In the present investigation, molecular modeling studies were performed on a series of 54 cyclic urea analogs with symmetric P2/P2′ substituents. The binding modes of these inhibitors were determined by docking. The docking results also provided a reliable conformational superimposition scheme for the 3D-QSAR studies. To gain insight into the steric, electrostatic, hydrophobic and hydrogen-bonding properties of these molecules and their influence on the inhibitory activity, comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) were performed. Two different alignment schemes viz. receptor-based and atom-fit alignment, were used in this study to build the QSAR models. The derived 3D-QSAR models were found to be robust with statistically significant r ² and r ² _pred values and have led to the identification of regions important for steric, hydrophobic and electronic interactions. The predictive ability of the models was assessed on a set of molecules that were not included in the training set. Superimposition of the 3D-contour maps generated from these models onto the active site of enzyme provided additional insight into the structural requirements of these inhibitors. The CoMFA and CoMSIA models were used to design some new inhibitors with improved binding affinity. Pharmacokinetic and toxicity predictions were also carried out for these molecules to gauge their ADME and safety profile. The computational results may open up new avenues for synthesis of potent HIV-1 protease inhibitors.     

Positive regulation of apoptosis by HCA66, a new Apaf-1 interacting protein, and its putative role in the physiopathology of NF1 microdeletion syndrome patients

As a component of the apoptosome, a caspase-activating complex, Apaf-1 plays a central role in the mitochondrial caspase activation pathway of apoptosis. We report here the identification of a novel Apaf-1 interacting protein, hepatocellular carcinoma antigen 66 (HCA66) that is able to modulate selectively Apaf-1-dependent apoptosis through its direct association with the CED4 domain of Apaf-1. Expression of HCA66 was able to potentiate Apaf-1, but not receptor-mediated apoptosis, by increasing downstream caspase activity following cytochrome c release from the mitochondria. Conversely, cells depleted of HCA66 were severely impaired for apoptosome-dependent apoptosis. Interestingly, expression of the Apaf-1-interacting domain of HCA66 had the opposite effect of the full-length protein, interfering with the Apaf-1 apoptotic pathway. Using a cell-free system, we showed that reduction of HCA66 expression was associated with a diminished amount of caspase-9 in the apoptosome, resulting in a lower ability of the apoptosome to activate caspase-3. HCA66 maps to chromosome 17q11.2 and is among the genes heterozygously deleted in neurofibromatosis type 1 (NF1) microdeletion syndrome patients. These patients often have a distinct phenotype compared to other NF1 patients, including a more severe tumour burden. Our results suggest that reduced expression of HCA66, owing to haploinsufficiency of HCA66 gene, could render NF1 microdeleted patients-derived cells less susceptible to apoptosis.     

A simple theoretical model for fluorescence polarization binding assay development

Fluorescence polarization is a screening technology that is radioactivity free, homogeneous, and ratiometric. The signal measured with this technology is a weighted value of free and bound ligand. As a consequence, saturation curves are accessible only after calculation of the corresponding concentrations of free and bound ligand. To make this technology more accessible to assay development, the authors propose a simple mathematical model that predicts fluorescence polarization values from ligand and receptor total concentrations, depending on the corresponding dissociation constant. This model was validated using data of Bodipy-NDP-alphaMSH binding to MC(5), obtained after either ligand saturation of a receptor preparation or, conversely, receptor saturation of a ligand solution. These experimental data were also used to calculate the actual concentration of free and bound ligand and receptor and to obtain pharmacological constants by Scatchard analysis. A general method is proposed, which facilitates the design of fluorescence polarization binding assays by relying on the representation of theoretical polarization values. This approach is illustrated by the application to 2 systems of very different affinities.     

DNA methylation: an identity card for brain cells

A recently published study has revealed the genome-wide dynamics of DNA methylation and hydroxymethylation patterns at single-base resolution in the human and mouse developing brain.