Chemical nucleases based on the transition-metal ions cleave DNA hydrolytically and/or oxidatively, with or without added reductant. We report here the novel DNA cleavage properties of the highly water-soluble, square-planar [Cu(Hpyrimol)Cl] complex, together with the results of cytotoxicities toward selected cancer cell lines. The copper complex cleaves PhiX174 supercoiled DNA efficiently without any reductant and shows high cytotoxicities toward L1210 murine leukemia and A2780 human ovarian carcinoma cancer cell lines that are sensitive and resistant to cisplatin. The IC50 values obtained for the copper complex in the sensitive cell lines are in the range of cisplatin, and for the cisplatin-resistant leukemia cell line, this value is even better.

Phenanthroline derivatives are of interest due to their potential activity against cancer, and viral, bacterial, and fungal infections. In a search for highly specific antitumor and antibacterial compounds, we report the activities of 1,10‐phenanthroline‐5,6‐dione (phendione or L1), dipyrido[3,2‐a:2′,3′‐c]phenazine (dppz or L2), and their corresponding platinum complexes ([PtL1Cl2] and [PtL2Cl2]), and provide the solid‐state 3D structure for [PtL1Cl2]. It is generally known that a toxic metal ion coordinated to an active organic moiety leads to a synergistic effect; however, we report herein that the platinum complexes [PtL1Cl2] and [PtL2Cl2] have weaker activities relative to those of the free ligands, especially against bacteria. Testing these agents against a variety of human cancer cell lines revealed that L1 and [PtL1Cl2] were at least as active as cisplatin against several of the cell lines (including a cisplatin‐resistant cell line). The absence of antibacterial activity of [PtL1Cl2] removes the detrimental effect of phenanthrolines toward intestinal flora, suggesting a highly promising new strategy for the development of anticancer drugs with reduced side effects.

Patients diagnosed with metastatic breast cancer have a dismal 5-year survival rate of only 24%. The RNA-binding protein Hu antigen R (HuR) is upregulated in breast cancer, and elevated cytoplasmic HuR correlates with high-grade tumors and poor clinical outcome of breast cancer. HuR promotes tumorigenesis by regulating numerous proto-oncogenes, growth factors, and cytokines that support major tumor hallmarks including invasion and metastasis. Here, we report a HuR inhibitor KH-3, which potently suppresses breast cancer cell growth and invasion. Furthermore, KH-3 inhibits breast cancer experimental lung metastasis, improves mouse survival, and reduces orthotopic tumor growth. Mechanistically, we identify FOXQ1 as a direct target of HuR. KH-3 disrupts HuR-FOXQ1 mRNA interaction, leading to inhibition of breast cancer invasion. Our study suggests that inhibiting HuR is a promising therapeutic strategy for lethal metastatic breast cancer.

Venezuelan equine encephalitis virus (VEEV) is an emerging pathogenic alphavirus that can cause significant disease in humans. Given the absence of therapeutic options available and the significance of VEEV as a weaponized agent, an optimization effort was initiated around a quinazolinone screening hit 1 with promising cellular antiviral activity (EC50 = 0.8 μM), limited cytotoxic liability (CC50 > 50 μM), and modest in vitro efficacy in reducing viral progeny (63-fold at 5 μM). Scaffold optimization revealed a novel rearrangement affording amidines, specifically compound 45, which was found to potently inhibit several VEEV strains in the low nanomolar range without cytotoxicity (EC50 = 0.02–0.04 μM, CC50 > 50 μM) while limiting in vitro viral replication (EC90 = 0.17 μM). Brain exposure was observed in mice with 45. Significant protection was observed in VEEV-infected mice at 5 mg kg–1 day–1 and viral replication appeared to be inhibited through interference of viral nonstructural proteins.

The reactions of the ligand 2-(2-pyridyl)benzthiazole (pbt) with CuBr 2 and ZnCl 2 in acetonitrile produce the complexes [Cu(pbt)Br 2] ( 1) and [Zn(pbt)Cl 2] ( 3), respectively. When complex 1 is dissolved in DMF, complex 2 is obtained as light-green crystals. The reaction of pbt with CuBr 2 in DMF also yields the complex [Cu(pbt)Br 2(dmf)] ( 2) (dmf = dimethylformamide). Complexes 1- 3 were characterized by X-ray crystallography. Complexes 1 and 3 have distorted tetrahedral coordination environments, and complex 2 is constituted of two slightly different copper centers, both exhibiting distorted trigonal bipyramidal geometries. Complexes 1 and 2 cleave phiX174 phage DNA, both in the presence and the absence of reductant. The free ligand pbt does not show any DNA-cleaving abilities. The poor solubility of complex 3 makes it not applicable for biological tests. The occurrence of DNA breaks in the presence of various radical scavengers suggests that no diffusible radicals are involved in the DNA cleavage by complex 1, as none of the scavengers inhibit the cleavage reaction. The DNA-cleavage products are not religated with the enzyme T4 DNA ligase, which is an additional proof that the cleavage is nonhydrolytic. Most probably the cleaving reaction involves reactive oxygen species, which could not be trapped, leading to an oxidative mechanism. An easy oxidation of Cu (II)(pbt)Br 2 to Cu (III) in DMF and the reduction of the same to Cu (I), under similar electrochemical conditions may lead to the in situ activation of molecular oxygen, resulting in the formation of metal solvated nondiffusible radicals able to prompt the oxidative cleavage of DNA. Complex 1 and the pure ligand exhibit remarkable cytotoxic effects against the cancer cell lines L1210 and A2780 and also against the corresponding cisplatin-resistant mutants of these cell lines.

Human antigen (Hu) R is an RNA-binding protein whose overexpression in human cancer correlates with aggressive disease, drug resistance, and poor prognosis. HuR inhibition has profound anticancer activity. Pharmacologic inhibitors can overcome the limitations of genetic inhibition. In this study, we examined the antitumor activity of CMLD-2, a small-molecule inhibitor directed against HuR, using non-small cell lung cancer (NSCLC) as a model. CMLD-2 efficacy was tested in vitro using H1299, A549, HCC827, and H1975 NSCLC cells and MRC-9 and CCD-16 normal human fibroblasts. Treatment of NSCLC cells with CMLD-2 produced dose-dependent cytotoxicity, caused a G1 phase cell-cycle arrest and induced apoptosis. CMLD-2 decreased HuR mRNA and the mRNAs of HuR-regulated proteins (Bcl2 and p27) in tumor cells. Additionally, reduction in the expression of HuR, Bcl2, cyclin E, and Bcl-XL with increased expression of Bax and p27 in CMLD-2-treated NSCLC cells were observed. CMLD-2-treated normal cells, HuR-regulated mRNAs and proteins albeit showed some reduction were less compared to tumor cells. Finally, CMLD-2 treatment resulted in greater mitochondrial perturbation, activation of caspase-9 and -3 and cleavage of PARP in tumor cells compared to normal cells. Our proof-of concept study results demonstrate CMLD-2 represents a promising HuR-targeted therapeutic class that with further development could lead to advanced preclinical studied and ultimately for lung cancer treatment.

No abstract

Coronaviruses are viral infections that have a significant ability to impact human health. Coronaviruses have produced two pandemics and one epidemic in the last two decades. The current pandemic has created a worldwide catastrophe threatening the lives of over 15 million as of July 2020. Current research efforts have been focused on producing a vaccine or repurposing current drug compounds to develop a therapeutic. There is, however, a need to study the active site preferences of relevant targets, such as the SARS-CoV-2 main protease (SARS-CoV-2 Mpro), to determine ways to optimize these drug compounds. The ensemble docking and characterization work described in this article demonstrates the multifaceted features of the SARS-CoV-2 Mpro active site, molecular guidelines to improving binding affinity, and ultimately the optimization of drug candidates. A total of 220 compounds were docked into both the 5R7Z and 6LU7 SARS-CoV-2 Mpro crystal structures. Several key preferences for strong binding to the four subsites (S1, S1′, S2, and S4) were identified, such as accessing hydrogen binding hotspots, hydrophobic patches, and utilization of primarily aliphatic instead of aromatic substituents. After optimization efforts using the design guidelines developed from the molecular docking studies, the average docking score of the parent compounds was improved by 6.59 −log10(Kd) in binding affinity which represents an increase of greater than six orders of magnitude. Using the optimization guidelines, the SARS-CoV-2 Mpro inhibitor cinanserin was optimized resulting in an increase in binding affinity of 4.59 −log10(Kd) and increased protease inhibitor bioactivity. The results of molecular dynamic (MD) simulation of cinanserin-optimized compounds CM02, CM06, and CM07 revealed that CM02 and CM06 fit well into the active site of SARS-CoV-2 Mpro [Protein Data Bank (PDB) accession number 6LU7] and formed strong and stable interactions with the key residues, Ser-144, His-163, and Glu-166. The enhanced binding affinity produced demonstrates the utility of the design guidelines described. The work described herein will assist scientists in developing potent COVID-19 antivirals.