Zhihao Liu

Discovery of imidazo[2,1-b]thiazole HCV NS4B inhibitors exhibiting synergistic effect with other direct-acting antiviral agents.

The design, synthesis, and SAR studies of novel inhibitors of HCV NS4B based on the imidazo[2,1-b]thiazole scaffold were described. Optimization of potency with respect to genotype 1b resulted in the discovery of two potent leads 26f (EC50 = 16 nM) and 28g (EC50 = 31 nM). The resistance profile studies revealed that 26f and 28g targeted HCV NS4B, more precisely the second amphipathic α helix of NS4B (4BAH2). Cross-resistance between our 4BAH2 inhibitors and other direct-acting antiviral agents targeting NS3/4A, NS5A, and NS5B was not observed. For the first time, the synergism of a series of combinations based on 4BAH2 inhibitors was evaluated. The results demonstrated that our 4BAH2 inhibitor 26f was synergistic with NS3/4A inhibitor simeprevir, NS5A inhibitor daclatasvir, and NS5B inhibitor sofosbuvir, and it could also reduce the dose of these drugs at almost all effect levels. Our study suggested that favorable effects could be achieved by combining 4BAH2 inhibitors such as 26f with these approved drugs and that new all-oral antiviral combinations based on 4BAH2 inhibitors were worth developing to supplement or even replace current treatment regimens for curing HCV infection.

Identification of novel 2-aminothiazole conjugated nitrofuran as antitubercular and antibacterial agents

The emergence of antibiotic resistant pathogens is an ongoing main problem in the therapy of bacterial infections. In order to develop promising antitubercular and antibacterial lead compounds, we designed and synthesized a new series of derivatives of 2-aminothiazole conjugated nitrofuran with activities against both Mycobacterium tuberculosis and Staphylococcus aureus. Eight compounds 12e, 12k, 12l, 12m, 18a, 18d, 18e, and 18j emerged as promising antitubercular agents. Structure-activity relationships (SARs) were discussed and showed that the derivatives substituted at the position-3 of benzene of 5-nitro-N-(4-phenylthiazol-2-yl)furan-2-carboxamide exhibited superior potency. The most potent compound 18e, substituted with benzamide at this position, displayed minimum inhibitory concentrations (MICs) of 0.27μg/mL against Mtb H37Ra and 1.36μg/mL against S. aureus. Furthermore, compound 18e had no obvious cytotoxicity to normal Vero cells (IC50=50.2μM). The results suggest that the novel scaffolds of aminothiazole conjugated nitrofuran would be a promising class of potent antitubercular and antimicrobial agents.

Synthesis and biological evaluation of (E)-4-(3-arylvinyl-1H-indazol-6-yl)pyrimidin-2-amine derivatives as PLK4 inhibitors for the treatment of breast cancer

Polo-like kinase 4 (PLK4), a vital regulator of centriole duplication, is important for maintaining genome stability. Dysregulation of PLK4 has been found in several human cancers and is associated with a predisposition to tumorigenesis. Herein, we describe the discovery of (E)-4-(3-arylvinyl-1H-indazol-6-yl)pyrimidin-2-amine derivatives as potent PLK4 inhibitors with more concise structure using a scaffold hopping strategy. SAR exploration and preliminary assessment identified 14i as a new PLK4 inhibitor which displayed excellent potency in vitro. 14i could inhibit the activity of PLK4, perturb centriole replication, result in mitosis disorder and induce cell apoptosis in breast cancer cells. Moreover 14i demonstrated significant antitumor efficacy in the MDA-MB-468 and MDA-MB-231 xenograft models. This study suggested that this concise chemotype would represent a promising scaffold of PLK4 inhibitors for cancer therapy and 14i would be an attractive lead compound for further optimization and evaluation.

Niclosamide induces colorectal cancer apoptosis, impairs metastasis and reduces immunosuppressive cells in vivo

Colorectal cancer (CRC) is one of the most common malignancies with considerable metastatic potential, explaining the need for new candidates that inhibit tumor growth and metastasis. Constitutive activation of signal transducers and activator of transcription 3 (Stat3) signaling promote tumorigenesis through disordering of the expression of key genes, and is associated with CRC progression. In this study, niclosamide, an FDA approved anthelmintic drug identified as a potent inhibitor of Stat3, was assessed for its anti-CRC activities in vitro and in vivo. We showed that niclosamide significantly inhibited proliferation in four CRC cell lines. In addition, the apoptosis was also found after treatment with niclosamide, which was related with the up-regulation of cleaved-caspases-3 and Bax but the down-regulation of Bcl-2 and the loss of mitochondrial membrane potential (ΔΨm) in CT26 cells. Moreover, niclosamide potently suppressed cell migration and invasion in a dose-dependent manner. Furthermore, our study showed that the administration of niclosamide in vivo markedly inhibited the number of tumor nodules in the abdomen metastasis model of colon cancer. The antitumor effect of niclosamide was correlated with a marked decrease in the number of MDSCs in tumor. Interestingly, niclosamide also suppressed the activation of FAK, Stat3 and the expression of matrix metalloproteinase MMP9. Taken together, these findings indicated that niclosamide might be a candidate drug for impairing the metastasis of colon cancer in part by inhibiting the activation of Stat3.

Small Molecule TH-39 Potentially Targets Hec1/Nek2 Interaction and Exhibits Antitumor Efficacy in K562 Cells via G0/G1 Cell Cycle Arrest and Apoptosis Induction

Background: Cancer is still a major public health issue worldwide, and new therapeutics with anti-tumor activity are still urgently needed. Methods: The anti-tumor activity of TH-39, which shows potent anti-proliferative activity against K562 cells with an IC50 of 0.78 µM, was investigated using immunoblot, co-immunoprecipitation, the MTT assay, and flow cytometry. Results: Mechanistically, TH-39 may disrupt the interaction between Hec1 and Nek2 in K562 cells. Moreover, TH-39 inhibited cell proliferation in a concentration- and time-dependent manner by influencing the morphology of K562 cells and inducing G0/G1 phase arrest. G0/G1 phase arrest was associated with down-regulation of CDK2-cyclin E complex and CDK4/6-cyclin D complex activities. Furthermore, TH-39 also induced cell apoptosis, which was associated with activation of caspase-3, down-regulation of Bcl-2 expression and up-regulation of Bax. TH-39 could also decrease mitochondrial membrane potential (Δψm) and increase reactive oxygen species (ROS) accumulation in K562 cells. The results indicated that TH-39 might induce apoptosis via the ROS-mitochondrial apoptotic pathway. Conclusion: This study highlights the potential therapeutic efficacy of the anti-cancer compound TH-39 in treatment-resistant chronic myeloid leukemia.

YLT-11, a novel PLK4 inhibitor, inhibits human breast cancer growth via inducing maladjusted centriole duplication and mitotic defect

Polo-like kinase 4 (PLK4) is indispensable for precise control of centriole duplication. Abnormal expression of PLK4 has been reported in many human cancers, and inhibition of PLK4 activity results in their mitotic arrest and apoptosis. Therefore, PLK4 may be a valid therapeutic target for antitumor therapy. However, clinically available small-molecule inhibitors targeting PLK4 are deficient and their underlying mechanisms still remain not fully clear. Herein, the effects of YLT-11 on breast cancer cells and the associated mechanism were investigated. In vitro, YLT-11 exhibited significant antiproliferation activities against breast cancer cells. Meanwhile, cells treated with YLT-11 exhibited effects consistent with PLK4 kinase inhibition, including dysregulated centriole duplication and mitotic defects, sequentially making tumor cells more vulnerable to chemotherapy. Furthermore, YLT-11 could strongly regulate downstream factors of PLK4, which was involved in cell cycle regulation, ultimately inducing apoptosis of breast cancer cell. In vivo, oral administration of YLT-11 significantly suppressed the tumor growth in human breast cancer xenograft models at doses that are well tolerated. In summary, the preclinical data show that YLT-11 could be a promising candidate drug for breast tumor therapy.

Selective and efficient synthesis of trans-arylvinylboronates and trans-hetarylvinylboronates using palladium catalyzed cross-coupling

trans-Arylvinylboronate derivatives are important synthesis blocks in natural products, pharmaceuticals and organic materials. There are only a few reaction conditions that could selectively provide trans-arylvinylboronates by Heck coupling of pinacol vinylboronate and aryl halides. Here we report an efficient and versatile method of palladium catalyzed cross-coupling between pinacol vinylboronate and various aryl or hetaryl bromides to obtain the corresponding trans-(het)arylvinylboronates in excellent yields and selectivity. 30 examples have been synthesized using this protocol which offers an alternative method to prepare these useful building blocks.

Synthesis and biological evaluation of N-(3-oxo-3,4-dihydro-2H-benzo[b][1,4]oxazin-7-yl)benzenesulfonamide derivatives as new BET bromodomain inhibitors for anti-hematologic malignancies activities

The bromodomain and extra-terminal proteins (BETs), in particular BRD4, has been reported to play important roles in cancer, inflammation, obesity, cardiovascular disease, and neurological disorders. In this paper, a series of benzomorpholinone derivatives were synthesized and biologically evaluated as BETs inhibitors. Detailed structure–activity relationship studies led to the discovery of several new potent compounds, of which 15h and 15i displayed

Correction: Synthesis and biological evaluation of N -(4-phenylthiazol-2-yl)cinnamamide derivatives as novel potential anti-tumor agents

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