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.

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.

Polyheterocyclic peptidomimetics: Parallel solid phase synthesis of oligo cyclic guanidines and their inhibition activity against Mycobacterium tuberculosis DNA gyrase.

Polyheterocycles are one of the most desired synthetic targets due to their numerous and valuable applications in various fields. We report the design and the parallel synthesis of novel linear oligocyclic guanidine peptidomimetics from predesigned reduced polyamides. A screening of these compounds identified active Mycobacterium tuberculosis DNA gyrase inhibitors which do not inhibit human DNA topoisomerase IIα and topoisomerase I.

The Lack of Synergy between Carvedilol and the Preventive Effect of Dexrazoxane in the Model of Chronic Anthracycline-Induced Cardiomyopathy.

The anticancer efficacy of doxorubicin (DOX) is dose-limited because of cardiomyopathy, the most significant adverse effect. Initially, cardiotoxicity develops clinically silently, but it eventually appears as dilated cardiomyopathy with a very poor prognosis. Dexrazoxane (DEX) is the only FDA-approved drug to prevent the development of anthracycline cardiomyopathy, but its efficacy is insufficient. Carvedilol (CVD) is another product being tested in clinical trials for the same indication. This study's objective was to evaluate anthracycline cardiotoxicity in rats treated with CVD in combination with DEX. The studies were conducted using male Wistar rats receiving DOX (1.6 mg/kg b.w. i.p., cumulative dose: 16 mg/kg b.w.), DOX and DEX (25 mg/kg b.w. i.p.), DOX and CVD (1 mg/kg b.w. i.p.), or a combination (DOX + DEX + CVD) for 10 weeks. Afterward, in the 11th and 21st weeks of the study, echocardiography (ECHO) was performed, and the tissues were collected. The addition of CVD to DEX as a cardioprotective factor against DOX had no favorable advantages in terms of functional (ECHO), morphological (microscopic evaluation), and biochemical alterations (cardiac troponin I and brain natriuretic peptide levels), as well as systemic toxicity (mortality and presence of ascites). Moreover, alterations caused by DOX were abolished at the tissue level by DEX; however, when CVD was added, the persistence of DOX-induced unfavorable alterations was observed. The addition of CVD normalized the aberrant expression of the vast majority of indicated genes in the DOX + DEX group. Overall, the results indicate that there is no justification to use a simultaneous treatment of DEX and CVD in DOX-induced cardiotoxicity.

Cyanotriazoles are selective topoisomerase II poisons that rapidly cure trypanosome infections.

Millions who live in Latin America and sub-Saharan Africa are at risk of trypanosomatid infections, which cause Chagas disease and human African trypanosomiasis (HAT). Improved HAT treatments are available, but Chagas disease therapies rely on two nitroheterocycles, which suffer from lengthy drug regimens and safety concerns that cause frequent treatment discontinuation. We performed phenotypic screening against trypanosomes and identified a class of cyanotriazoles (CTs) with potent trypanocidal activity both in vitro and in mouse models of Chagas disease and HAT. Cryo-electron microscopy approaches confirmed that CT compounds acted through selective, irreversible inhibition of trypanosomal topoisomerase II by stabilizing double-stranded DNA:enzyme cleavage complexes. These findings suggest a potential approach toward successful therapeutics for the treatment of Chagas disease.

Recent Developments in Combination Chemotherapy for Colorectal and Breast Cancers with Topoisomerase Inhibitors.

DNA topoisomerases are important enzymes that stabilize DNA supercoiling and resolve entanglements. There are two main types of topoisomerases in all cells: type I, which causes single-stranded DNA breaks, and type II, which cuts double-stranded DNA. Topoisomerase activity is particularly increased in rapidly dividing cells, such as cancer cells. Topoisomerase inhibitors have been an effective chemotherapeutic option for the treatment of several cancers. In addition, combination cancer therapy with topoisomerase inhibitors may increase therapeutic efficacy and decrease resistance or side effects. Topoisomerase inhibitors are currently being used worldwide, including in the United States, and clinical trials on the combination of topoisomerase inhibitors with other drugs are currently underway. The primary objective of this review was to comprehensively analyze the current clinical landscape concerning the combined application of irinotecan, an extensively investigated type I topoisomerase inhibitor for colorectal cancer, and doxorubicin, an extensively researched type II topoisomerase inhibitor for breast cancer, while presenting a novel approach for cancer therapy.

Bioisosteric Design Identifies Inhibitors of Mycobacterium tuberculosis DNA Gyrase ATPase Activity.

Mutations in DNA gyrase confer resistance to fluoroquinolones, second-line antibiotics for Mycobacterium tuberculosis infections. Identification of new agents that inhibit M. tuberculosis DNA gyrase ATPase activity is one strategy to overcome this. Here, bioisosteric designs using known inhibitors as templates were employed to define novel inhibitors of M. tuberculosis DNA gyrase ATPase activity. This yielded the modified compound R3-13 with improved drug-likeness compared to the template inhibitor that acted as a promising ATPase inhibitor against M. tuberculosis DNA gyrase. Utilization of compound R3-13 as a virtual screening template, supported by subsequent biological assays, identified seven further M. tuberculosis DNA gyrase ATPase inhibitors with IC50 values in the range of 0.42-3.59 µM. The most active compound 1 showed an IC50 value of 0.42 µM, 3-fold better than the comparator ATPase inhibitor novobiocin (1.27 µM). Compound 1 showed noncytotoxicity to Caco-2 cells at concentrations up to 76-fold higher than its IC50 value. Molecular dynamics simulations followed by decomposition energy calculations identified that compound 1 occupies the binding pocket utilized by the adenosine group of the ATP analogue AMPPNP in the M. tuberculosis DNA gyrase GyrB subunit. The most prominent contribution to the binding of compound 1 to M. tuberculosis GyrB subunit is made by residue Asp79, which forms two hydrogen bonds with the OH group of this compound and also participates in the binding of AMPPNP. Compound 1 represents a potential new scaffold for further exploration and optimization as a M. tuberculosis DNA gyrase ATPase inhibitor and candidate anti-tuberculosis agent.

Doxorubicin-Mediated miR-433 Expression on Exosomes Promotes Bystander Senescence in Multiple Myeloma Cells in a DDR-Independent Manner.

The success of senescence-based anticancer therapies relies on their anti-proliferative power and on their ability to trigger anti-tumor immune responses. Indeed, genotoxic drug-induced senescence increases the expression of NK cell-activating ligands on multiple myeloma (MM) cells, boosting NK cell recognition and effector functions. Senescent cells undergo morphological change and context-dependent functional diversification, acquiring the ability to secrete a vast pool of molecules termed the senescence-associated secretory phenotype (SASP), which affects neighboring cells. Recently, exosomes have been recognized as SASP factors, contributing to modulating a variety of cell functions. In particular, evidence suggests a key role for exosomal microRNAs in influencing many hallmarks of cancer. Herein, we demonstrate that doxorubicin treatment of MM cells leads to the enrichment of miR-433 into exosomes, which in turn induces bystander senescence. Our analysis reveals that the establishment of the senescent phenotype on neighboring MM cells is p53- and p21-independent and is related to CDK-6 down-regulation. Notably, miR-433-dependent senescence does not induce the up-regulation of activating ligands on MM cells. Altogether, our findings highlight the possibility of miR-433-enriched exosomes to reinforce doxorubicin-mediated cellular senescence.

Development of a microemulsion loaded with epoxy-α-lapachone against Leishmania (Leishmania) amazonensis murine infection.

Epoxy-α-lapachone (ELAP), an oxirane-functionalized molecule synthesized from naturally occurring lapachol, has shown promising activity against murine infection with Leishmania (Leishmania) amazonensis. Herein, we report the successful development of oil-in-water-type (o/w) microemulsions (ME) loaded with ELAP (ELAP-ME) using Capmul MCM, Labrasol, and PEG 400. Stability studies revealed that ELAP-ME (100 µg/mL of ELAP), which was comprised of globule size smaller than 120.4 ± 7.7 nm, displayed a good stability profile over 73 days. ELAP-ME had an effect in BALB/c mice infected with L. (L.) amazonensis, causing reductions in paw lesions after two weeks of treatment (∼2-fold) when compared to untreated animals. Furthermore, there was also a reduction in the parasite load both in the footpad (60.3%) and in the lymph nodes (31.5%). Based on these findings, ELAP-ME emerges as a promising treatment for tegumentar leishmaniasis.

Assessment of Structural Basis for Thiazolopyridine Derivatives as DNA Gyrase-B Inhibitors.

BACKGROUND: Tuberculosis (TB) is one of the leading causes of death in the post-COVID- 19 era. It has been observed that there is a devastating condition with a 25-30% increase in TB patients. DNA gyrase B isoform has proved its high potential to be a therapeutically effective target for developing newer and safer anti-TB agents. OBJECTIVE: This study aims to identify minimum structural requirements for the optimization of thiazolopyridine derivatives having DNA gyrase inhibitory activities. Moreover, developed QSAR models could be used to design new thiazolopyridine derivatives and predict their DNA gyrase B inhibitory activity before synthesis. METHODS: 3D-QSAR and Group-based QSAR (G-QSAR) methodologies were adopted to develop accurate, reliable, and predictive QSAR models. Statistical methods such as kNN-MFA SW-FB and MLR SW-FB were used to correlate dependent parameters with descriptors. Both models were thoroughly validated for internal and external predictive abilities. RESULTS: The 3D-QSAR model significantly correlated steric and electrostatic descriptors with q2 0.7491 and predicted r2 0.7792. The G-QSAR model showed that parameters such as SsOHE-index, slogP, ChiV5chain, and T_C_C_3 were crucial for optimizing thiazolopyridine derivatives as DNA gyrase inhibitors. The 3D-QSAR model was interpreted extensively with respect to 3D field points, and the pattern of fragmentation was studied in the G-QSAR model. CONCLUSION: The 3D-QSAR and G-QSAR models were found to be highly predictive. These models could be useful for designing potent DNA gyrase B inhibitors before their synthesis.

A Mini Review of Novel Topoisomerase II Inhibitors as Future Anticancer Agents.

Several reviews of inhibitors of topoisomerase II have been published, covering research before 2018. Therefore, this review is focused primarily on more recent publications with relevant points from the earlier literature. Topoisomerase II is an established target for anticancer drugs, which are further subdivided into poisons and catalytic inhibitors. While most of the topoisomerase II-based drugs in clinical use are mostly topoisomerase II poisons, their mechanism of action has posed severe concern due to DNA damaging potential, including the development of multi-drug resistance. As a result, we are beginning to see a gradual paradigm shift towards non-DNA damaging agents, such as the lesser studied topoisomerase II catalytic inhibitors. In addition, this review describes some novel selective catalytic topoisomerase II inhibitors. The ultimate goal is to bring researchers up to speed by curating and delineating new scaffolds as the leads for the optimization and development of new potent, safe, and selective agents for the treatment of cancer.

Targeting novel sites in DNA gyrase for development of anti-microbials.

Antimicrobial resistance in bacteria poses major challenges in selection of the therapeutic regime for managing the infectious disease. There is currently an upsurge in the appearance of multiple drug resistance in bacterial pathogens and a decline in the discovery of novel antibiotics. DNA gyrase is an attractive target used for antibiotic discovery due to its vital role in bacterial DNA replication and segregation in addition to its absence in mammalian organisms. Despite the presence of successful antibiotics targeting this enzyme, there is a need to bypass the resistance against this validated drug target. Hence, drug development in DNA gyrase is a highly active research area. In addition to the conventional binding sites for the novobiocin and fluoroquinolone antibiotics, several novel sites are being exploited for drug discovery. The binding sites for novel bacterial type II topoisomerase inhibitor (NBTI), simocyclinone, YacG, Thiophene and CcdB are structurally and biochemically validated active sites, which inhibit the supercoiling activity of topoisomerases. The novel chemical moieties with varied scaffolds have been identified to target DNA gyrase. Amongst them, the NBTI constitutes the most advanced DNA gyrase inhibitor which are in phase III trial of drug development. The present review aims to classify the novel binding sites other than the conventional novobiocin and quinolone binding pocket to bypass the resistance due to mutations in the DNA gyrase enzyme. These sites can be exploited for the identification of new scaffolds for the development of novel antibacterial compounds.

Upgrade of chrysomycin A as a novel topoisomerase II inhibitor to curb KRAS-mutant lung adenocarcinoma progression.

A primary strategy employed in cancer therapy is the inhibition of topoisomerase II (Topo II), implicated in cell survival. However, side effects and adverse reactions restrict the utilization of Topo II inhibitors. Thus, investigations focus on the discovery of novel compounds that are capable of inhibiting the Topo II enzyme and feature safer toxicological profiles. Herein, we upgrade an old antibiotic chrysomycin A from Streptomyces sp. 891 as a compelling Topo II enzyme inhibitor. Our results show that chrysomycin A is a new chemical entity. Notably, chrysomycin A targets the DNA-unwinding enzyme Topo II with an efficient binding potency and a significant inhibition of intracellular enzyme levels. Intriguingly, chrysomycin A kills KRAS-mutant lung adenocarcinoma cells and is negligible cytotoxic to normal cells at the cellular level, thus indicating a capability of potential treatment. Furthermore, mechanism studies demonstrate that chrysomycin A inhibits the Topo II enzyme and stimulates the accumulation of reactive oxygen species, thereby inducing DNA damage-mediated cancer cell apoptosis. Importantly, chrysomycin A exhibits excellent control of cancer progression and excellent safety in tumor-bearing models. Our results provide a chemical scaffold for the synthesis of new types of Topo II inhibitors and reveal a novel target for chrysomycin A to meet its further application.

Treatment-Associated Acute Lymphoblastic Leukemia Following Autologous Hematopoietic Stem Cell Transplant and Lenalidomide Maintenance in Patients With Multiple Myeloma.

Secondary malignancies including leukemia are an increasing concern in patients with prior primary malignancies treated with alkylating agents or topoisomerase II inhibitors. These can also be referred to as therapy-related leukemia. Therapy-related leukemia most commonly results in myelodysplastic syndrome or acute myeloid leukemia. The alkylating agent can cause chromosomal aberrations typically manifest as deletions in chromosome 11 or loss of part of complete loss of chromosomes 5 and 7. Conversely, acute lymphoblastic leukemia (ALL) has been described following maintenance therapy with immunomodulatory (IMiD) drugs pomalidomide, thalidomide, and lenalidomide. We present a case of a 71-year-old man with a history of multiple myeloma (MM) maintained on lenalidomide after stem cell transplant who presented with treatment-associated ALL. At time of leukemic presentation, chromosomal analysis showed a near-triploid clone consistent with masked double low hyplodiploidy which is associated with a poor prognosis. The patient had a deletion of the long arm of chromosome 5 which has been described in prior case reports with ALL secondary to lenalidomide therapy. There are explicit mechanisms in the literature, which have been attributed to development of ALL after exposure to thalidomide or lenalidomide. At time of submission, there are 20 cases described in the literature linking ALL to IMiD drugs. We describe a case and review the mechanisms of lenalidomide-associated ALL.

Pharmacological strategies to reduce anthracycline-associated cardiotoxicity in cancer patients.

INTRODUCTION: Anthracycline chemotherapeutic agents are widely used in the treatment of hematological and solid tumors, working principally through DNA intercalation and topoisomerase II inhibition. However, they are also well known to have cardiotoxic sequelae, commonly denoted as a reduction in ejection fraction. Drug-associated cardiotoxicity remains a significant limiting factor in the use of anthracyclines. AREAS COVERED: In this review, we explore the potential mechanisms of anthracycline-associated cardiotoxicity, identifying high-risk cohorts and approaches to cardiovascular monitoring. The mechanisms through which cardiotoxicity occurs are complex and diverse, ultimately leading to increased oxidative stress, mitochondrial dysfunction, and subsequent cellular apoptosis. Many of the cardiotoxic effects of anthracyclines exhibit a dose-dependent cumulative relationship and are more apparent in patients with previously existing cardiovascular risk factors. Long-term cardiovascular monitoring and optimization of risk factors, prior to commencing treatment as well as beyond the time of treatment, is therefore essential. EXPERT OPINION: We discuss some of the pharmacological strategies proposed to mitigate anthracycline-associated cardiotoxicity as well as prevention strategies to reduce the burden of coexisting cardiovascular risk factors. We highlight methods of early detection of patient cohorts who are at increased risk of developing anthracycline-associated cardiotoxicity and identify potential avenues for further research.

Increased EAT volume after anthracycline chemotherapy is associated with a low risk of cardiotoxicity in breast cancer.

PURPOSE: Chemotherapy-induced cardiotoxicity is a critical issue for patients with breast cancer. Change of epicardial adipose tissue (EAT) is associated with cardiac dysfunction. The objective of this study was to investigate the relationship between EAT and chemotherapy-induced cardiotoxicity. METHODS: This retrospective study analyzed EAT on chest computed tomography (CT) of patients with early breast cancer using automatic, quantitative measurement software between November 2015 and January 2020. Changes in EAT before and after initiation of chemotherapy were compared according to the type of anticancer drug. Subclinical cardiotoxicity was defined as worsening ≥ 10% in left ventricular ejection fraction to an absolute value > 50% with a lower limit of normal measured with standard echocardiography. RESULTS: Among 234 patients with breast cancer, 85 were treated with adjuvant anthracycline-based (AC) and 149 were treated with non-anthracycline-based (non-AC) chemotherapy. There was a significant increase in EAT volume index (mL/kg/m2) at the end of chemotherapy compared to that at the baseline in the AC group (3.33 ± 1.53 vs. 2.90 ± 1.52, p < 0.001), but not in the non-AC group. During the follow-up period, subclinical cardiotoxicity developed in 20/234 (8.6%) patients in the total population [13/85 (15.3%) in the AC group and 7/149 (4.8%) in the non-AC group]. In the multivariable analysis, EAT volume index increment after chemotherapy was associated with a lower risk of subclinical cardiotoxicity in the AC group (Odds ratio: 0.364, 95% CI 0.136-0.971, p = 0.044). CONCLUSIONS: Measurement of EAT during anthracycline-based chemotherapy might help identify subgroups who are vulnerable to chemotherapy-induced cardiotoxicity. Early detection of EAT volume change could enable tailored chemotherapy with cardiotoxicity prevention strategies.

Spiropyrimidinetrione DNA Gyrase Inhibitors with Potent and Selective Antituberculosis Activity.

New antibiotics with either a novel mode of action or novel mode of inhibition are urgently needed to overcome the threat of drug-resistant tuberculosis (TB). The present study profiles new spiropyrimidinetriones (SPTs), DNA gyrase inhibitors having activity against drug-resistant Mycobacterium tuberculosis (Mtb), the causative agent of TB. While the clinical candidate zoliflodacin has progressed to phase 3 trials for the treatment of gonorrhea, compounds herein demonstrated higher inhibitory potency against Mtb DNA gyrase (e.g., compound 42 with IC50 = 2.0) and lower Mtb minimum inhibitor concentrations (0.49 µM for 42). Notably, 42 and analogues showed selective Mtb activity relative to representative Gram-positive and Gram-negative bacteria. DNA gyrase inhibition was shown to involve stabilization of double-cleaved DNA, while on-target activity was supported by hypersensitivity against a gyrA hypomorph. Finally, a docking model for SPTs with Mtb DNA gyrase was developed, and a structural hypothesis was built for structure-activity relationship expansion.

PTEN loss drives resistance to the neddylation inhibitor MLN4924 in glioblastoma and can be overcome with TOP2A inhibitors.

BACKGROUND: Neddylation inhibition, affecting posttranslational protein function and turnover, is a promising therapeutic approach to cancer. We report vulnerability to MLN4924 or pevonedistat (a neddylation inhibitor) in a subset of glioblastoma (GBM) preclinical models and identify biomarkers, mechanisms, and signatures of differential response. METHODS: GBM sequencing data were queried for genes associated with MLN4924 response status; candidates were validated by molecular techniques. Time-course transcriptomics and proteomics revealed processes implicated in MLN4924 response. RESULTS: Vulnerability to MLN4924 is associated with elevated S-phase populations, re-replication, and DNA damage. Transcriptomics and shotgun proteomics depict PTEN signaling, DNA replication, and chromatin instability pathways as significant differentiators between sensitive and resistant models. Loss of PTEN and its nuclear functions is associated with resistance to MLN4924. Time-course proteomics identified elevated TOP2A in resistant models through treatment. TOP2A inhibitors combined with MLN4924 prove synergistic. CONCLUSIONS: We show that PTEN status serves as both a novel biomarker for MLN4924 response in GBM and reveals a vulnerability to TOP2A inhibitors in combination with MLN4924.

Identification of Potent DNA Gyrase Inhibitors Active against Mycobacterium tuberculosis.

Mycobacterium tuberculosis DNA gyrase manipulates the DNA topology using controlled breakage and religation of DNA driven by ATP hydrolysis. DNA gyrase has been validated as the enzyme target of fluoroquinolones (FQs), second-line antibiotics used for the treatment of multidrug-resistant tuberculosis. Mutations around the DNA gyrase DNA-binding site result in the emergence of FQ resistance in M. tuberculosis; inhibition of DNA gyrase ATPase activity is one strategy to overcome this. Here, virtual screening, subsequently validated by biological assays, was applied to select candidate inhibitors of the M. tuberculosis DNA gyrase ATPase activity from the Specs compound library (www.specs.net). Thirty compounds were identified and selected as hits for in vitro biological assays, of which two compounds, G24 and G26, inhibited the growth of M. tuberculosis H37Rv with a minimal inhibitory concentration of 12.5 µg/mL. The two compounds inhibited DNA gyrase ATPase activity with IC50 values of 2.69 and 2.46 µM, respectively, suggesting this to be the likely basis of their antitubercular activity. Models of complexes of compounds G24 and G26 bound to the M. tuberculosis DNA gyrase ATP-binding site, generated by molecular dynamics simulations followed by pharmacophore mapping analysis, showed hydrophobic interactions of inhibitor hydrophobic headgroups and electrostatic and hydrogen bond interactions of the polar tails, which are likely to be important for their inhibition. Decreasing compound lipophilicity by increasing the polarity of these tails then presents a likely route to improving the solubility and activity. Thus, compounds G24 and G26 provide attractive starting templates for the optimization of antitubercular agents that act by targeting DNA gyrase.

The Novel Dual Topoisomerase Inhibitor P8-D6 Shows Anti-myeloma Activity In Vitro and In Vivo.

P8-D6 is a novel dual inhibitor of human topoisomerase I (TOP1) and II (TOP2) with broad pro-apoptotic antitumor activity. NCI-60 screening revealed markedly improved cytotoxicity of P8-D6 against solid and leukemia cell lines compared with other single and dual topoisomerase inhibitors, for example, irinotecan, doxorubicin, or pyrazoloacridine. In this study, we investigated the capacity of P8-D6 to inhibit myeloma cell growth in vitro and in vivo Growth inhibition assays demonstrated significant anti-myeloma effects against different myeloma cell lines with IC50 values in the low nanomolar range. Freshly isolated plasma cells of patients with multiple myeloma were killed by P8-D6 with similar doses. P8-D6 activated caspase 3/7 and induced significant apoptosis of myeloma cells. Supportive effects of bone marrow stromal cells on IL6-dependent INA-6 myeloma cells were abrogated by P8-D6 and apoptosis occurred in a time- and dose-dependent manner. Of note, healthy donor peripheral blood mononuclear cells and human umbilical vein endothelial cells were not affected at concentrations toxic for malignant plasma cells. Treatment of myeloma xenografts in immunodeficient SCID/beige mice by intravenous and, notably, also oral application of P8-D6 markedly inhibited tumor growths, and significantly prolonged survival of tumor-bearing mice.