Design,synthesis and biological evaluation of novel non-covalent piperidine-containing peptidyl proteasome inhibitors

A series of novel non-covalent piperidine-containing dipeptidyl derivatives were designed, synthesized and evaluated as proteasome inhibitors. All target compounds were tested for their proteasome chymotrypsin-like inhibitory activities, and selected derivatives were evaluated for the anti-proliferation activities against two multiple myeloma (MM) cell lines RPMI 8226 and MM-1S. Among all of these compounds, eight exhibited significant proteasome inhibitory activities with IC₅₀ less than 20 nM, and four are more potent than the positive control Carfilzomib. Compound 28 displayed the most potent proteasome inhibitory activity (IC₅₀: 1.4 ± 0.1 nM) and cytotoxicities with IC₅₀ values at 13.9 ± 1.8 nM and 9.5 ± 0.5 nM against RPMI 8226 and MM-1S, respectively. Additionally, the ex vivo blood cell proteasome inhibitory activities of compounds 24 and 27–29 demonstrated that the enzymatic metabolism in the whole blood could be well tolerated. All these experiments confirmed that the piperidine-containing non-covalent proteasome inhibitors are potential leads for exploring new anti-cancer drugs.     

Design,biological evaluation and 3D QSAR studies of novel dioxin-containing triaryl pyrazoline derivatives as potential B-Raf inhibitors

A series of novel dioxin-containing triaryl pyrazoline derivatives C1–C20 have been synthesized. Their B-Raf inhibitory and anti-proliferation activities were evaluated. Compound C6 displayed the most potent biological activity against B-Raf^V600E and WM266.4 human melanoma cell line with corresponding IC₅₀ value of 0.04 μM and GI₅₀ value of 0.87 μM, being comparable with the positive controls and more potent than our previous best compounds. Moreover, C6 was selective for B-Raf^V600E from B-Raf^WT, C-Raf and EGFR and low toxic. The docking simulation suggested the potent bioactivity might be caused by breaking the limit of previous binding pattern. A new 3D QSAR model was built with the activity data and binding conformations to conduct visualized SAR discussion as well as to introduce new directions. Stretching the backbone to outer space or totally reversing the backbone are both potential orientations for future researches.     

Identification of 2-thioxoimidazolidin-4-one derivatives as novel noncovalent proteasome and immunoproteasome inhibitors

This paper describes the design, synthesis, and biological evaluation of 2-thioxoimidazolidin-4-one derivatives as inhibitors of proteasome and immunoproteasome, potential targets for the treatment of hematological malignancies. In particular, we focused our efforts on the design of noncovalent inhibitors, which might be a promising therapeutic option potentially devoid of drawbacks and side-effects related to irreversible inhibition. Among all the synthesized compounds, we identified a panel of active inhibitors with K_i values towards one or two chymotrypsin-like activities of proteasome (β5c) and immunoproteasome (β5i and β1i subunits) in the low micromolar range. Docking studies suggested a unique binding mode of the molecules in the catalytic site of immunoproteasome proteolytic subunits.     

Discovery of novel 20S proteasome inhibitors by rational topology-based scaffold hopping of bortezomib

A series of structurally novel proteasome inhibitors 1–12 have been developed based rational topology-based scaffold hopping of bortezomib. Among these novel proteasome inhibitors, compound 10 represents an important advance due to the comparable proteasome-inhibitory activity (IC₅₀?=?9.7?nM) to bortezomib (IC₅₀?=?8.3?nM), the remarkably higher BEI and SEI values and the effectiveness in metabolic stability. Therefore, compound 10 provides an excellent lead suitable for further optimization.     

Design,synthesis, and biological evaluation of bone-targeted proteasome inhibitors for multiple myeloma

Multiple myeloma (MM) is an incurable neoplasm characterized by devastating and progressive bone destruction. Standard chemotherapeutic agents have not been effective at significantly prolonging the survival of MM patients and these agents are typically associated with often severe, dose-limiting side effects. There is great need for methods to target the delivery of novel, effective cytotoxic agents specifically to bone, where myeloma cells reside. We have synthesized and evaluated the effects of the bone-targeted proteasome inhibitors PS-341-BP-1, PS-341-BP-2 and MG-262-BP on cell proliferation using the mouse 5TGM1 and human RPMI 8226 cell lines in vitro. The compounds exhibit strong cytotoxicity on MM cell lines and reduce the number of viable cells in a dose dependent manner.     

Naphthoquinone amino acid derivatives,synthesis and biological activity as proteasome inhibitors

The ubiquitin-proteasome system has been largely investigated for its key role in protein degradation mechanisms that regulate both apoptosis and cell division. Because of their antitumour activity, different classes of proteasome inhibitors have been identified to date. Some of these compounds are currently employed in the clinical treatment of several types of cancer among which multiple myeloma. Here, we describe the design, chemistry, biological activity and modelling studies of a large series of amino acid derivatives linked to a naphthoquinone pharmacophoric group through variable spacers. Some analogues showed interesting inhibitory potency for the β1 and β5 subunits of the proteasome with IC₅₀ values in the sub-µm range.     

Studies of C-terminal naphthoquinone dipeptides as 20S proteasome inhibitors

The ubiquitin proteasome pathway is crucial in regulating many processes in the cell. Modulation of proteasome activities has emerged as a powerful strategy for potential therapies against much important pathologies. In particular, specific inhibitors may represent a useful tool for the treatment of tumors. Here, we report studies of a new series of peptide-based analogues bearing a naphthoquinone pharmacophoric unit at the C-terminal position. Some derivatives showed inhibition in the µM range of the post-acidic-like and chymotrypsin-like active sites of the proteasome.     

Design,synthesis and biological evaluation of novel oseltamivir derivatives as potent neuraminidase inhibitors

Neuraminidase (NA) is one of the particular potential targets for novel antiviral therapy. In this work, a series of neuraminidase inhibitors with the cyclohexene scaffold were studied based upon the combination of 3D-QSAR, molecular docking, and molecular dynamics techniques. The results indicate that the built 3D-QSAR models yield reliable statistical information: the correlation coefficient (r²) and cross-validation coefficient (q²) of CoMFA (comparative molecular field analysis) are 0.992 and 0.819; the r² and q² of CoMSIA (comparative molecular similarity analysis) are 0.992 and 0.863, respectively. Molecular docking and MD simulations were conducted to confirm the detailed binding mode of enzyme-inhibitor system. The new NA inhibitors had been designed, synthesized, and their inhibitory activities against group-1 neuraminidase were determined. One agent displayed excellent neuraminidase inhibition, with IC₅₀ value of 39.6?μM against NA, while IC₅₀ value for oseltamivir is 61.1?μM. This compound may be further investigated for the treatment of infection by the new type influenza virus.     

Design,synthesis and biological evaluation of novel zanamivir derivatives as potent neuraminidase inhibitors

Neuraminidase (NA) is an important antiviral drug target. Zanamivir is one of the most potent NA inhibitors. In this paper, a series of zanamivir derivatives as potential NA inhibitors were studied by combination of molecular modeling techniques including 3D-QSAR, molecular docking, and molecular dynamics (MD) simulation. The results show that the best CoMFA (comparative molecular field analysis) model has q²?=?0.728 and r²?=?0.988, and the best CoMSIA (comparative molecular similarity indices analysis) model has q²?=?0.750 and r²?=?0.981, respectively. The built 3D-QSAR models show significant statistical quality and excellent predictive ability. Seven new NA inhibitors were designed and predicted. 20?ns of MD simulations were carried out and their binding free energies were calculated. Two designed compounds were selected to be synthesized and biologically evaluated by NA inhibition and virus inhibition assays. One compound (IC₅₀?=?0.670?µM, SI?>?149) exhibits excellent antiviral activity against A/WSN/33 H1N1, which is superior to the reference drug zanamivir (IC₅₀?=?0.873?µM, SI?>?115). The theoretical and experimental results may provide reference for development of new anti-influenza drugs.     

Design,synthesis and biological evaluation of benzimidazole derivatives as novel human Pin1 inhibitors

In this work, a series of novel benzimidazole derivatives were designed and synthesized as Pin1 inhibitors. Protease-coupled assay was used to investigate the Pin1 inhibitory potency of all synthesized compounds. Thirteen of them showed preferable Pin1 inhibitory effects with IC₅₀ values lower than 5 μM, and 12a, 15b, 15d and 16c exhibited the most promising Pin1 inhibitory activity at low micromolar level (0.33–1.00 μM) than the positive control compound Juglone. Flow cytometry results showed that treating PC-3 cells with 16c caused slight cycle arrest in a concentration-dependent manner. The structure-activity relationships of R¹, R², R³ and linker of the benzimidazole derivatives were analyzed in detail, which would help further exploration of new Pin1 inhibitors.     

Design,synthesis and biological evaluation of novel aminomethyl-piperidones based DPP-IV inhibitors

A series of novel aminomethyl-piperidones were designed and evaluated as potential DPP-IV inhibitors. Optimized analogue 12v ((4S,5S)-5-(aminomethyl)-1-(2-(benzo[d][1,3]dioxol-5-yl)ethyl)-4-(2,5-difluorophenyl)piperidin-2-one) showed excellent in vitro potency and selectivity for DPP-IV over other serine proteases. The lead compound 12v showed potent and long acting antihyperglycemic effects (in vivo), along with improved pharmacokinetic profile.     

Design,synthesis and biological evaluation of curcumin analogues as novel LSD1 inhibitors

Histone lysine-specific demethylase 1 (LSD1) was the first discovered histone demethylase. Inactivating LSD1 or downregulating its expression inhibits cancer-cell development, and thus, it is an attractive molecular target for the development of novel cancer therapeutics. In this study, we worked on the structural optimization of natural products and identified 30 novel LSD1 inhibitors. Utilizing a structure-based drug design strategy, we designed and synthesized a series of curcumin analogues that were shown to be potent LSD1 inhibitors in the enzyme assay. Compound WB07 displayed the most potent LSD1 inhibitory activity, with an IC₅₀ value of 0.8 μM. Moreover, WA20 showed an anticlonogenic effect on A549 cells with an IC₅₀ value of 4.4 μM. Molecular docking simulations were also carried out, and the results indicated that the inhibitors bound to the protein active site located around the key residues of Asp555 and Asp556. These findings suggested that compounds WA20 and WB07 are the first curcumin analogue-based LSD1 inhibitors with remarkable A549 suppressive activity, providing a novel scaffold for the development of LSD1 inhibitors.     

Design,synthesis and biological evaluation of novel L-isoserine tripeptide derivatives as aminopeptidase N inhibitors

Aminopeptidase N (APN/CD13) is one of the essential proteins for tumour invasion, angiogenesis and metastasis as it is over-expressed on the surface of different tumour cells. Based on our previous work that L-isoserine dipeptide derivatives were potent APN inhibitors, we designed and synthesized L-isoserine tripeptide derivatives as APN inhibitors. Among these compounds, one compound 16l (IC₅₀?=?2.51?±?0.2 µM) showed similar inhibitory effect compared with control compound Bestatin (IC₅₀?=?6.25?±?0.4 µM) and it could be used as novel lead compound for the APN inhibitors development as anticancer agents in the future.     

New betulinic acid derivatives as potent proteasome inhibitors

In this study, 22 new betulinic acid (BA) derivatives were synthesized and tested for their inhibition of the chymotrypsin-like activity of 20S proteasome. From the SAR study, we concluded that the C-3 and C-30 positions are the pharmacophores for increasing the proteasome inhibition effects, and larger lipophilic or aromatic side chains are favored at these positions. Among the BA derivatives tested, compounds 13, 20, and 21 showed the best proteasome inhibition activity with IC(50) values of 1.42, 1.56, and 1.80 μM, respectively, which are three to fourfold more potent than the proteasome inhibition controls LLM-F and lactacystin.     

Design,synthesis, and biological evaluation of novel triazoloquinazolinone derivatives as SHP2 protein inhibitors

A novel series of triazoloquinazolinone derivatives were designed, synthesised, and evaluated for their in vitro biological activities against the SHP2 protein. Moreover, some compounds were evaluated against A375 cells. The results revealed that target compounds possessed moderate to excellent inhibitory activity against SHP2 protein, whereas compounds 12f, 12l, 12j, 17e, and 17f have strong antiproliferative activity on A375 cells. The compound 12l showed remarkable cytotoxicity against A375 cells and a strong inhibitory effect against SHP2 protein when compared with SHP244. The structure-activity relationships (SARs) indicated that electron-donating groups (EDGs) on phenyl rings are beneficial for improving the antitumor activity; compounds with a hydroxyl substituent at the 2-position of phenyl ring exhibited superior activities than compounds with a substituent at the 4-position. In addition, compound 12l displayed improved physicochemical properties as well as metabolic stability compared to SHP244. Our efforts identified 12l as a promising SHP2 protein inhibitor, warranting its further investigation.     

Design, synthesis and biological evaluation of novel nitroaromatic compounds as potent glutathione reductase inhibitors

Discovery of GR inhibitors has become very popular recently due to antimalarial and anticancer activities. In this study, the synthesis and GR inhibitory capacities of novel nitroaromatic compounds (NCs) (1-3) were reported. Some commercially available molecules were also tested for comparison reasons. The novel NCs were obtained in high yields using simple chemical procedures and exhibited much potent inhibitory activities against GR at low micromolar concentrations with K(i) values ranging from 0.211 to 4.57 μM as compared with well-known agents. Inhibition mechanism was assessed as being due to occlusion of the active site entrance by means of the NCs. Molecular docking results have shown that docking poses of ligands are able to construct binding interactions with the essential amino acids.     

Naegleria fowleri and Naegleria gruberi 20S proteasome: identification and characterization

The Naegleria are ubiquitous free-living amoebae and are characterized by the presence of three phases in their biological cycle: trophozoite, cyst and flagellate. Of this genus, only Naegleria fowleri has been reported as pathogenic to humans. The proteasome is a multi-catalytic complex and is considered to be the most important structure responsible for the degradation of intracellular proteins. This structure is related to the maintenance of cellular homeostasis and, in pathogenic microorganisms, to the modulation of their virulence. Until now, the proteasome and its function have not been described for the Naegleria genus. In the current study, using bioinformatic analysis, protein sequences homologous to those reported for the subunits of the 20S proteasome in other organisms were found, and virtual modelling was used to determine their three-dimensional structure. The presence of structural and catalytic subunits of the 20S proteasome was detected by Western and dot blot assays. Its localization was observed by immunofluorescence microscopy to be mainly in the cytoplasm, and a leading role of the chymotrypsin-like catalytic activity was determined using fluorogenic peptidase assays and specific proteasome inhibitors. Finally, the role of the 20S proteasome in the proliferation and differentiation of Naegleria genus trophozoites was demonstrated.     

Design,synthesis and biological studies of novel tubulin inhibitors

A series of compounds originally derived from the vascular endothelial growth factor receptor tyrosine kinase inhibitor, SU5416, were synthesized and evaluated. The most potent compound in this series, compound 3, which structurally resembles the potent anti-microtubule agent combretastatin A-4, inhibited tubulin polymerization and showed potent growth inhibitory activities on both prostate and breast cancer lines with IC₅₀ values in the low nanomolar range.     

Design and synthesis of a novel class of furan-based molecules as potential 20S proteasome inhibitors

A novel class of furan-based compounds as potential 20S proteasome inhibitors have been designed and synthesized, among which nine compounds are peptide derivatives and six molecules are statine peptidomimetics. The C-terminal furanyl moiety was introduced to target molecules as furan-based amino acids. All the compounds were obtained steadily with moderate to high yield. Compound 12 was a selective moderate potent proteasome peptidomimetic inhibitor. It inhibited HepG2 and HL-60 proliferation effectively.