Gyrase and Topoisomerase IV: Recycling Old Targets for New Antibacterials to Combat Fluoroquinolone Resistance.

Beyond their requisite functions in many critical DNA processes, the bacterial type II topoisomerases, gyrase and topoisomerase IV, are the targets of fluoroquinolone antibacterials. These drugs act by stabilizing gyrase/topoisomerase IV-generated DNA strand breaks and by robbing the cell of the catalytic activities of these essential enzymes. Since their clinical approval in the mid-1980s, fluoroquinolones have been used to treat a broad spectrum of infectious diseases and are listed among the five "highest priority" critically important antimicrobial classes by the World Health Organization. Unfortunately, the widespread use of fluoroquinolones has been accompanied by a rise in target-mediated resistance caused by specific mutations in gyrase and topoisomerase IV, which has curtailed the medical efficacy of this drug class. As a result, efforts are underway to identify novel antibacterials that target the bacterial type II topoisomerases. Several new classes of gyrase/topoisomerase IV-targeted antibacterials have emerged, including novel bacterial topoisomerase inhibitors, Mycobacterium tuberculosis gyrase inhibitors, triazaacenaphthylenes, spiropyrimidinetriones, and thiophenes. Phase III clinical trials that utilized two members of these classes, gepotidacin (triazaacenaphthylene) and zoliflodacin (spiropyrimidinetrione), have been completed with positive outcomes, underscoring the potential of these compounds to become the first new classes of antibacterials introduced into the clinic in decades. Because gyrase and topoisomerase IV are validated targets for established and emerging antibacterials, this review will describe the catalytic mechanism and cellular activities of the bacterial type II topoisomerases, their interactions with fluoroquinolones, the mechanism of target-mediated fluoroquinolone resistance, and the actions of novel antibacterials against wild-type and fluoroquinolone-resistant gyrase and topoisomerase IV.

2,3-Dichloronaphthoquinone derivatives: Synthesis, antimicrobial activity, molecular modelling and ADMET studies.

In the present study, an intermediate namely 2-(3-bromopropylamino)-3-chloronaphthalene-1,4-dione was initially synthesized via the nucleophilic addition-elimination reaction between 2,3-dichloro-1,4-naphthoquinone and 3-bromo-1-aminopropane. Then a coupling reaction between the intermediate and piperazine derivatives yielded a number of 1,4-naphthoquinone derivatives. Spectroscopic analysis successfully characterized the products that were obtained in good yields. In vitro antibacterial properties of the compounds were examined against different bacterial strains. In vitro antibacterial properties of the compounds were examined against the bacterial strains S. Aureus, E. Faecalis, E. Coli and P. Aeruginosa. While compound 9 was found to be effective against all bacterial strains used, compound 12 was active against three strains and compounds 10 and 11 were effective against the two. None of the compounds are effective against C. albicans strain. In silico molecular docking studies revealed that all compounds had docking scores comparable to the antibacterial drugs ciprofloxacin and gentamicin and might be considered as DNA gyrase B inhibitors. Molecular dynamics simulations were also conducted for a better understanding of the stability and the selected docked complexes. Additionally, the drug similarity of the synthesized compounds and ADMET characteristics were examined in conjunction with the antibiotic ciprofloxacin, and drug potentials were then evaluated. Compatible predictions were found with the drug similarity and ADMET parameters.

New imidazole-2-thiones linked to acenaphythylenone as dual DNA intercalators and topoisomerase II inhibitors: structural optimization, docking, and apoptosis studies.

In this article, a new series of 2-((3,5-disubstituted-2-thioxo-imidazol-1-yl)imino)acenaphthylen-1(2H)-ones were synthesized. Imidazole-2-thione with acenaphthylen-one gave a hybrid scaffold that integrated key structural elements essential for DNA damage via direct DNA intercalation and inhibition of the topoisomerase II enzyme. All the synthesized compounds were screened to detect their DNA damage using a terbium fluorescent probe. Results demonstrated that 4-phenyl-imidazoles 5b and 5e in addition to 4-(4-chlorophenyl)imidazoles 5h and 5j would induce detectable potent damage in ctDNA. The four most potent compounds as DNA intercalators were further evaluated for their antiproliferative activity against HepG2, MCF-7 and HCT-116 utilizing the MTT assay. The highest anticancer activity was recorded with compounds 5b and 5h against the breast cancer cell line MCF-7 which were 1.5- and 3- folds more active than doxorubicin, respectively. Therefore, imidazole-2-thione tethered acenaphthylenone derivatives can be considered as promising scaffold for the development of effective dual DNA intercalators and topoisomerase II inhibitors.

Anthracyclines induce cardiotoxicity through a shared gene expression response signature.

TOP2 inhibitors (TOP2i) are effective drugs for breast cancer treatment. However, they can cause cardiotoxicity in some women. The most widely used TOP2i include anthracyclines (AC) Doxorubicin (DOX), Daunorubicin (DNR), Epirubicin (EPI), and the anthraquinone Mitoxantrone (MTX). It is unclear whether women would experience the same adverse effects from all drugs in this class, or if specific drugs would be preferable for certain individuals based on their cardiotoxicity risk profile. To investigate this, we studied the effects of treatment of DOX, DNR, EPI, MTX, and an unrelated monoclonal antibody Trastuzumab (TRZ) on iPSC-derived cardiomyocytes (iPSC-CMs) from six healthy females. All TOP2i induce cell death at concentrations observed in cancer patient serum, while TRZ does not. A sub-lethal dose of all TOP2i induces limited cellular stress but affects calcium handling, a function critical for cardiomyocyte contraction. TOP2i induce thousands of gene expression changes over time, giving rise to four distinct gene expression response signatures, denoted as TOP2i early-acute, early-sustained, and late response genes, and non-response genes. There is no drug- or AC-specific signature. TOP2i early response genes are enriched in chromatin regulators, which mediate AC sensitivity across breast cancer patients. However, there is increased transcriptional variability between individuals following AC treatments. To investigate potential genetic effects on response variability, we first identified a reported set of expression quantitative trait loci (eQTLs) uncovered following DOX treatment in iPSC-CMs. Indeed, DOX response eQTLs are enriched in genes that respond to all TOP2i. Next, we identified 38 genes in loci associated with AC toxicity by GWAS or TWAS. Two thirds of the genes that respond to at least one TOP2i, respond to all ACs with the same direction of effect. Our data demonstrate that TOP2i induce thousands of shared gene expression changes in cardiomyocytes, including genes near SNPs associated with inter-individual variation in response to DOX treatment and AC-induced cardiotoxicity.

Multi-target rational design and synthesis of novel diphenyl-tethered pyrazolopyrimidines targeting EGFR and topoisomerase II with potential DNA intercalation and apoptosis induction.

Herein, we envisioned the design and synthesis of novel pyrazolopyrimidines (confirmed by elemental analysis, 1H and 13C NMR, and mass spectra) as multitarget-directed drug candidates acting as EGFR/TOPO II inhibitors, DNA intercalators, and apoptosis inducers. The target diphenyl-tethered pyrazolopyrimidines were synthesized starting from the reaction of phenyl hydrazine and ethoxymethylenemalononitrile to give aminopyrazole-carbonitrile 2. The latter hydrolysis with NaOH and subsequent reaction with 4-chlorobenzaldhyde afforded the corresponding pyrazolo[3,4-d]pyrimidin-4-ol 4. Chlorination of 4 with POCl3 and sequential reaction with different amines afforded the target compounds in good yields (up to 73 %). The growth inhibition % of the new derivatives (6a-m) was investigated against different cancer and normal cells and the IC50 values of the most promising candidates were estimated for HNO97, MDA-MB-468, FaDu, and HeLa cancer cells. The frontier derivatives (6a, 6i, 6k, 6l, and 6m) were pursued for their EGFR inhibitory activity. Compound 6l decreased EGFR protein concentration by a 6.10-fold change, compared to imatinib as a reference standard. On the other side, compounds (6a, 6i, 6k, 6l, and 6m) underwent topoisomerase II (TOPO II) inhibitory assay. In particular, compounds 6a and 6l exhibited IC50s of 17.89 and 19.39 µM, respectively, surpassing etoposide with IC50 of 20.82 µM. Besides, the DNA fragmentation images described the great potential of both candidates 6a and 6l in inducing DNA degradation at lower concentrations compared to etoposide and doxorubicin. Moreover, compound 6l, with the most promising EGFR/TOPO II inhibition and DNA intercalation, was selected for further investigation for its apoptosis induction ability by measuring caspases 3, 7, 8, and 9, Bax, p53, MMP2, MMP9, and BCL-2 proteins. Additionally, molecular docking was used to explain the SAR results based on the differences in the molecular features of the investigated congeners and the target receptors' topology.

New pyranopyrazole based derivatives: Design, synthesis, and biological evaluation as potential topoisomerase II inhibitors, apoptotic inducers, and antiproliferative agents.

A new series of pyranopyrazole-based derivatives were designed and synthesized. The synthesized compounds were assessed for their cytotoxic efficacy against A549 human lung carcinoma and MCF-7 human breast carcinoma cell lines. Three compounds (1b, 4b, and 7b) exhibited 1.3- to 2.3-fold more antiproliferative activity than that of doxorubicin against the A549 cell line. In comparison to doxorubicin, compounds 1d and 3b were 4.1- and 1.04-fold, respectively more powerful against MCF-7 cancer cells. All the synthesized compounds were found to be more selective toward A549 cancer cells than the normal human fibroblast BJ cells. Of interest, compounds 1b and 7b exhibited promising cytotoxicity and SIs of 27.72 and 25.30, respectively, towards A549 cancer cells, higher than that of doxorubicin (SI 4.81). The most potent compounds 1b, 1d, 3b, 4b, and 7b were then subjected to in vitro Topo II inhibition assay. They showed IC50 values in the range of 2.07 to 8.86 µM. Of particular interest, compound 7b (IC50 = 2.07 µM), exhibited higher Topo II inhibitory activity than that of doxorubicin (IC50 = 2.56 µM). The significant Topo II inhibition of compound 7b was explained by molecular docking simulations into the Topo II active site. Compound 7b halted the cell cycle in the S phase in A549 cancer cells. It induced total apoptosis and necrosis of 20.73- and 4-fold, respectively, greater than the control. This evidence was supported by a 3.59-fold increase in the level of apoptotic caspase-9 and a remarkable elevation of the Bax/BCL-2 ratio. The physiochemical parameters of compound 7b were aligned with Lipinski's rule of five.

Tapcin, an In Vivo Active Dual Topoisomerase I/II Inhibitor Discovered by Synthetic Bioinformatic Natural Product (Syn-BNP)-Coupled Metagenomics.

DNA topoisomerases are attractive targets for anticancer agents. Dual topoisomerase I/II inhibitors are particularly appealing due to their reduced rates of resistance. A number of therapeutically relevant topoisomerase inhibitors are bacterial natural products. Mining the untapped chemical diversity encoded by soil microbiomes presents an opportunity to identify additional natural topoisomerase inhibitors. Here we couple metagenome mining, bioinformatic structure prediction algorithms, and chemical synthesis to produce the dual topoisomerase inhibitor tapcin. Tapcin is a mixed p-aminobenzoic acid (PABA)-thiazole with a rare tri-thiazole substructure and picomolar antiproliferative activity. Tapcin reduced colorectal adenocarcinoma HT-29 cell proliferation and tumor volume in mouse hollow fiber and xenograft models, respectively. In both studies it showed similar activity to the clinically used topoisomerase I inhibitor irinotecan. The study suggests that the interrogation of soil microbiomes using synthetic bioinformatic natural product methods has the potential to be a rewarding strategy for identifying potent, biomedically relevant, antiproliferative agents.

Identification of apigenin-4'-glucoside as bacterial DNA gyrase inhibitor by QSAR modeling, molecular docking, DFT, molecular dynamics, and in vitro confirmation studies.

CONTEXT: It is well known that antibiotic resistance is a major health hazard. To eradicate antibiotic-resistant bacterial infections, it is essential to find a novel antibacterial agent. Hence, in this study, a quantitative structure-activity relationship (QSAR) model was developed using 43 DNA gyrase inhibitors, and 700 natural compounds were screened for their antibacterial properties. Based on molecular docking and absorption, distribution, metabolism, excretion, and toxicity (ADMET) studies, the top three leads viz., apigenin-4'-glucoside, 8-deoxygartanin, and cryptodorine were selected and structurally optimized using density functional theory (DFT) studies. The optimized structures were redocked, and molecular dynamic (MD) simulations were performed. Binding energies were calculated by molecular mechanics/Poisson-Boltzmann surface area solvation (MM-PBSA). Based on the above studies, apigenin-4'-glucoside was identified as a potent antibacterial lead. Further in vitro confirmation studies were performed using the plant Lawsonia inermis containing apigenin-4'-glucoside to confirm the antibacterial activity. METHODS: For QSAR modeling, 2D descriptors were calculated by PaDEL-Descriptors v2.21 software, and the model was developed using the DTClab QSAR tool. Docking was performed using PyRx v0.8 software. ORCA v5.0.1 computational package was used to optimize the structures. The job type used in optimization was equilibrium structure search using the DFT hybrid functional ORCA method B3LYP. The basis set was 6-311G (3df, 3pd) plus four polarization functions for all atoms. Accurate docking was performed for optimized leads using the iGEMDOCK v2.1 tool with a genetic algorithm by 10 solutions each of 80 generations. Molecular dynamic simulations were performed using GROMACS 2020.04 software with CHARMM36 all-atom force field.

Novel terpyridines as Staphylococcus aureus gyrase inhibitors: efficient synthesis and antibacterial assessment via solvent-drop grinding.

Aim: This study was designed to synthesize a novel series of terpyridines with potential antibacterial properties, targeting multidrug resistance. Materials & methods: Terpyridines (4a-h and 6a-c) were synthesized via a one-pot multicomponent reaction using 2,6-diacetylpyridines, benzaldehyde derivatives and malononitrile or ethyl 2-cyanoacetate. The reactions, conducted under grinding conditions with glacial acetic acid, produced high-yield compounds, confirmed by spectroscopic data. Results: The synthesized terpyridines exhibited potent antibacterial activity. Notably, compounds 4d and 4h demonstrated significant inhibition zones against Staphylococcus aureus and Bacillus subtilis, outperforming ciprofloxacin. Conclusion: Molecular docking studies highlighted compounds 4d, 4h and 6c as having strong binding affinity to DNA gyrase B, correlating with their robust antibacterial activity, suggesting their potential as effective agents against multidrug-resistant bacterial strains.

Exploring the effects of topoisomerase II inhibitor XK469 on anthracycline cardiotoxicity and DNA damage.

Anthracyclines, such as doxorubicin (adriamycin), daunorubicin, or epirubicin, rank among the most effective agents in classical anticancer chemotherapy. However, cardiotoxicity remains the main limitation of their clinical use. Topoisomerase IIß has recently been identified as a plausible target of anthracyclines in cardiomyocytes. We examined the putative topoisomerase IIß selective agent XK469 as a potential cardioprotective and designed several new analogs. In our experiments, XK469 inhibited both topoisomerase isoforms (α and ß) and did not induce topoisomerase II covalent complexes in isolated cardiomyocytes and HL-60, but induced proteasomal degradation of topoisomerase II in these cell types. The cardioprotective potential of XK469 was studied on rat neonatal cardiomyocytes, where dexrazoxane (ICRF-187), the only clinically approved cardioprotective, was effective. Initially, XK469 prevented daunorubicin-induced toxicity and p53 phosphorylation in cardiomyocytes. However, it only partially prevented the phosphorylation of H2AX and did not affect DNA damage measured by Comet Assay. It also did not compromise the daunorubicin antiproliferative effect in HL-60 leukemic cells. When administered to rabbits to evaluate its cardioprotective potential in vivo, XK469 failed to prevent the daunorubicin-induced cardiac toxicity in either acute or chronic settings. In the following in vitro analysis, we found that prolonged and continuous exposure of rat neonatal cardiomyocytes to XK469 led to significant toxicity. In conclusion, this study provides important evidence on the effects of XK469 and its combination with daunorubicin in clinically relevant doses in cardiomyocytes. Despite its promising characteristics, long-term treatments and in vivo experiments have not confirmed its cardioprotective potential.

Is Simultaneous Binding to DNA and Gyrase Important for the Antibacterial Activity of Cystobactamids?

Cystobactamids are aromatic oligoamides that exert their natural antibacterial properties by inhibition of bacterial gyrases. Such aromatic oligoamides were proposed to inhibit α-helix-mediated protein-protein interactions and may serve for specific recognition of DNA. Based on this suggestion, we designed new derivatives that have duplicated cystobactamid triarene units as model systems to decipher the specific binding mode of cystobactamids to double stranded DNA. Solution NMR analyses revealed that natural cystobactamids as well as their elongated analogues show an overall bent shape at their central aliphatic unit, with an average CX-CY-CZ angle of ~110 degrees. Our finding is corroborated by the target-bound structure of close analogues, as established by cryo-EM very recently. Cystobactamid CN-861-2 binds directly to the bacterial gyrase with an affinity of 9 µM, and also exhibits DNA-binding properties with specificity for AT-rich DNA. Elongation/dimerization of the triarene subunit of native cystobactamids is demonstrated to lead to an increase in DNA binding affinity. This implies that cystobactamids' gyrase inhibitory activity necessitates not just interaction with the gyrase itself, but also with DNA via their triarene unit.

Discovery of benzopyridone cyanoacetates as new type of potential broad-spectrum antibacterial candidates.

Unique benzopyridone cyanoacetates (BCs) as new type of promising broad-spectrum antibacterial candidates were discovered with large potential to combat the lethal multidrug-resistant bacterial infections. Many prepared BCs showed broad antibacterial spectrum with low MIC values against the tested strains. Some highly active BCs exhibited rapid sterilization capacity, low resistant trend and good predictive pharmacokinetic properties. Furthermore, the highly active sodium BCs (NaBCs) displayed low hemolysis and cytotoxicity, and especially octyl NaBC 5g also showed in vivo potent anti-infective potential and appreciable pharmacokinetic profiles. A series of preliminary mechanistic explorations indicated that these active BCs could effectively eliminate bacterial biofilm and destroy membrane integrity, thus resulting in the leakage of bacterial cytoplasm. Moreover, their unique structures might further bind to intracellular DNA, DNA gyrase and topoisomerase IV through various direct noncovalent interactions to hinder bacterial reproduction. Meanwhile, the active BCs also induced bacterial oxidative stress and metabolic disturbance, thereby accelerating bacterial apoptosis. These results provided a bright hope for benzopyridone cyanoacetates as potential novel multitargeting broad-spectrum antibacterial candidates to conquer drug resistance.

Palindromic carbazole derivatives: unveiling their antiproliferative effect via topoisomerase II catalytic inhibition and apoptosis induction.

Human DNA topoisomerases are essential for crucial cellular processes, including DNA replication, transcription, chromatin condensation, and maintenance of its structure. One of the significant strategies employed in cancer treatment involves the inhibition of a specific type of topoisomerase, known as topoisomerase II (Topo II). Carbazole derivatives, recognised for their varied biological activities, have recently become a significant focus in oncological research. This study assesses the efficacy of three symmetrically substituted carbazole derivatives: 2,7-Di(2-furyl)-9H-carbazole (27a), 3,6-Di(2-furyl)-9H-carbazole (36a), and 3,6-Di(2-thienyl)-9H-carbazole (36b) - as anticancer agents. Among investigated carbazole derivatives, compound 3,6-di(2-furyl)-9H-carbazole bearing two furan moieties emerged as a novel catalytic inhibitor of Topo II. Notably, 3,6-di(2-furyl)-9H-carbazole effectively selectively inhibited the relaxation and decatenation activities of Topo IIα, with minimal effects on the IIß isoform. These findings underscore the potential of compound 3,6-Di(2-furyl)-9H-carbazole as a promising lead candidate warranting further investigation in the realm of anticancer drug development.

Synthesis and antitumor activity of cyclopentane-fused anthraquinone derivatives.

In our pursuit of developing novel analogs of anthracyclines with enhanced antitumor efficacy and safety, we have designed a synthesis scheme for 4,11-dihydroxy-5,10-dioxocyclopenta[b]anthracene-2-carboxamides. These newly synthesized compounds exhibit remarkable antiproliferative potency against various mammalian tumor cell lines, including those expressing activated mechanisms of multidrug resistance. The structure of the diamine moiety in the carboxamide side chain emerges as a critical determinant for anticancer activity and interaction with key targets such as DNA, topoisomerase 1, and ROS induction. Notably, the introduced modification to the doxorubicin structure results in significantly increased lipophilicity, cellular uptake, and preferential distribution in lysosomes. Consequently, while maintaining an impact on anthracyclines targets, these novel derivatives also demonstrate the potential to induce cytotoxicity through pathways associated with lysosomes. In summary, derivatives of cyclic diamines, particularly 3-aminopyrrolidine, can be considered a superior choice compared to aminosugars for incorporation into natural and semi-synthetic anthracyclines or new anthraquinone derivatives, aiming to circumvent efflux-mediated drug resistance.

Schematic-portfolio of potent anti-microbial scaffolds targeting DNA gyrase: Unlocking ways to overcome resistance.

Drug development process demands validation of specific drug target impeding the Multi Drug Resistance (MDR). DNA gyrase, as a bacterial target has been in trend for developing newer antibacterial candidates due to its absence in higher eukaryotes. The fluoroquinolones are the leading molecules in the drug discovery pipeline for gyrase inhibition due to its diversity. The fluoroquinolones like levofloxacin and moxifloxacin have been listed in class A drugs for treating MDR. Gatifloxacin and ciprofloxacin also proved its efficacy against MDR TB and MDR enteric fever in adults, whereas nemonoxacin can induce anti-MDR activity of other antibiotics already suggested by studies. Though fluoroquinolones already proved its effectiveness against gyrase, other molecules viz., benzothiazinone, phenyl pyrrolamide, substituted oxadiazoles, triazolopyrimidine, arylbenzothiazole, coumarinyl amino alcohols and ciprofloxacin uracil, can inhibit the target more precisely. The structure-activity-relationships of the different scaffolds along with their synthetic strategies have been deciphered in the current review. Also, the naturally occurring compounds along with their extraction procedure have also been highlighted as potent DNA gyrase inhibitors. In addition to fluoroquinolone, the natural compounds novobiocin and simocyclinone could also inhibit the gyrase, impressively which has been designed with the gyrase structure for better understanding. Herein, ongoing clinical development of some novel drugs possessing triazaacenaphthylenes, spiropyrimidinetriones, and oxazolidinone-quinolone hybrids have been highlighted which could further assist the future generation antibiotic development corroborating gyrase as a potential target against MDR pathogens.

The overview of development of novel bacterial topoisomerase inhibitors effective against multidrug-resistant bacteria in an academic environment: From early hits to in vivo active antibacterials.

Antimicrobial resistance caused by the excessive and inappropriate use of antibacterial drugs is a global health concern. Currently, we are walking a fine line between the fact that most bacterial infections can still be cured with the antibiotics known so far, and the emergence of infections with bacteria resistant to several drugs at the same time, against which we no longer have an effective drug. Therefore, new antibacterial drugs are urgently needed to curb the hard-to-treat infections. Our group has developed new antibacterials from the class of novel bacterial topoisomerase inhibitors (NBTIs) that exhibit broad-spectrum antibacterial activity. This article reviews our efforts in developing highly potent NBTIs over the past decade. Following the discovery of an initial hit with potent enzyme inhibitory and broad-spectrum antibacterial activity, an extensive hit-to-lead campaign was conducted with the goal of optimizing physicochemical properties, reducing hERG inhibition, and maintaining antibacterial activity against both Gram-positive and Gram-negative bacteria, with a focus on methicillin-resistant Staphylococcus aureus (MRSA). This optimization strategy resulted in an amide-containing, focused NBTI library with compounds exhibiting potent antibacterial activity against Gram-positive bacteria, reduced hERG inhibition, no cardiotoxicity in in vivo zebrafish model, and favorable in vivo efficacy in a neutropenic murine thigh infection model for MRSA infections.

Design and synthesis of luotonin A-derived topoisomerase targeting scaffold with potent antitumor effect and low genotoxicity.

Conventional topoisomerase (Topo) inhibitors typically usually exert their cytotoxicity by damaging the DNAs, which exhibit high toxicity and tend to result in secondary carcinogenesis risk. Molecules that have potent topoisomerase inhibitory activity but involve less DNA damage provide more desirable scaffolds for developing novel chemotherapeutic agents. In this work, we broke the rigid pentacyclic system of luotonin A and synthesized thirty-three compounds as potential Topo inhibitors based on the devised molecular motif. Further investigation disclose that two compounds with the highest antiproliferation activity against cancer cells, 5aA and 5dD, had a distinct Topo I inhibitory mechanism different from those of the classic Topo I inhibitors CPT or luteolin, and were able to obviate the obvious cellular DNA damage typically associated with clinically available Topo inhibitors. The animal model experiments demonstrated that even in mice treated with a high dosage of 50 mg/kg 5aA, there were no obvious signs of toxicity or loss of body weight. The tumor growth inhibition (TGI) rate was 54.3 % when 20 mg/kg 5aA was given to the T24 xenograft mouse model, and 5aA targeted the cancer tissue precisely without causing damage to the liver and other major organs.

Virtual Screening and ADMET Prediction to Uncover the Potency of Flavonoids from Genus Erythrina as Antibacterial Agent through Inhibition of Bacterial ATPase DNA Gyrase B.

The emergence of antimicrobial resistance due to the widespread and inappropriate use of antibiotics has now become the global health challenge. Flavonoids have long been reported to be a potent antimicrobial agent against a wide range of pathogenic microorganisms in vitro. Therefore, new antibiotics development based on flavonoid structures could be a potential strategy to fight against antibiotic-resistant infections. This research aims to screen the potency of flavonoids of the genus Erythrina as an inhibitor of bacterial ATPase DNA gyrase B. From the 378 flavonoids being screened, 49 flavonoids show potential as an inhibitor of ATPase DNA gyrase B due to their lower binding affinity compared to the inhibitor and ATP. Further screening for their toxicity, we identified 6 flavonoids from these 49 flavonoids, which are predicted to have low toxicity. Among these flavonoids, erystagallin B (334) is predicted to have the best pharmacokinetic properties, and therefore, could be further developed as new antibacterial agent.

Cell cycle responses to Topoisomerase II inhibition: Molecular mechanisms and clinical implications.

DNA Topoisomerase IIA (Topo IIA) is an enzyme that alters the topological state of DNA and is essential for the separation of replicated sister chromatids and the integrity of cell division. Topo IIA dysfunction activates cell cycle checkpoints, resulting in arrest in either the G2-phase or metaphase of mitosis, ultimately triggering the abscission checkpoint if non-disjunction persists. These events, which directly or indirectly monitor the activity of Topo IIA, have become of major interest as many cancers have deficiencies in Topoisomerase checkpoints, leading to genome instability. Recent studies into how cells sense Topo IIA dysfunction and respond by regulating cell cycle progression demonstrate that the Topo IIA G2 checkpoint is distinct from the G2-DNA damage checkpoint. Likewise, in mitosis, the metaphase Topo IIA checkpoint is separate from the spindle assembly checkpoint. Here, we integrate mechanistic knowledge of Topo IIA checkpoints with the current understanding of how cells regulate progression through the cell cycle to accomplish faithful genome transmission and discuss the opportunities this offers for therapy.

Lower cardiotoxicity of CPX-351 relative to daunorubicin plus cytarabine free-drug combination in hiPSC-derived cardiomyocytes in vitro.

Liposomal formulations are hypothesized to alleviate anthracycline cardiotoxicity, although this has only been documented clinically for doxorubicin. We developed an in vitro multiparametric model using human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM) to assess the relative toxicity of anthracyclines across formulations. Proof of concept was established by treating hiPSC-CM with equivalent concentrations of free and liposomal doxorubicin. The study was then repeated with free daunorubicin plus cytarabine and CPX-351, a dual-drug liposomal encapsulation of daunorubicin/cytarabine. hiPSC-CM were treated with free-drug or liposomal formulations for 24 h on Days 1, 3, and 5 at equivalent concentrations ranging from 0 to 1000 ng/mL and assessed on subsequent days. Free-drug treatment resulted in concentration-dependent cumulative cytotoxicity (microscopy), more profound decrease in ATP levels, and significant time- and concentration-dependent decreases in oxygen consumption versus liposomal formulations (p < 0.01). Repeated free-drug exposure also resulted in greater release of biomarkers (cardiac troponin I, FABP3) and lactate dehydrogenase, as well as in a biphasic rhythmicity response (initial increase followed by slowing/quiescence of beating) indicating significant injury, which was not observed after repeated exposure to liposomal formulations. Overall, liposomal formulations were considerably less toxic to hiPSC-CM than their free-drug counterparts. Clinical data will be needed to confirm findings for CPX-351.