Enhanced tumor specific drug release by hypoxia sensitive dual-prodrugs based on 2-nitroimidazole

Hypoxia in cancer is important in the development of cancer-selective medicines. Here, a novel hypoxia-responsible dual-prodrug is described. We designed and synthesized 2-nitroimidazole derivatives which spontaneously release both a PYG inhibitor and gemcitabine under hypoxic conditions. One such derivative, a prodrug 9 was found to be stable against chemical and enzymatic hydrolysis, and upon chemical reduction of the nitro group on imidazole, successfully releases both drugs. In an in vitro proliferation assay using human pancreatic cells, compound 9 exhibited significant anti-proliferative effects in hypoxia but fewer effects in normoxia. Consequently, prodrug 9 should be useful for cancer treatment due to its improved cancer selectivity and potential to overcome drug resistance.

Molecular imaging of tumor hypoxia: Evolution of nitroimidazole radiopharmaceuticals and insights for future development

Though growing evidence has been collected in support of the concept of dose escalation based on the molecular level images indicating hypoxic tumor sub-volumes that could be radio-resistant, validation of the concept is still a work in progress. Molecular imaging of tumor hypoxia using radiopharmaceuticals is expected to provide the required input to plan dose escalation through Image Guided Radiation Therapy (IGRT) to kill/control the radio-resistant hypoxic tumor cells. The success of the IGRT, therefore, is heavily dependent on the quality of images obtained using the radiopharmaceutical and the extent to which the image represents the true hypoxic status of the tumor in spite of the heterogeneous nature of tumor hypoxia. Available literature on radiopharmaceuticals for imaging hypoxia is highly skewed in favor of nitroimidazole as the pharmacophore given their ability to undergo oxygen dependent reduction in hypoxic cells. In this context, present review on nitroimidazole radiopharmaceuticals would be immensely helpful to the researchers to obtain a birds-eye view on what has been achieved so far and what can be tried differently to obtain a better hypoxia imaging agent. The review also covers various methods of radiolabeling that could be utilized for developing radiotracers for hypoxia targeting applications.

A neutrophil-biomimic platform for eradicating metastatic breast cancer stem-like cells by redox microenvironment modulation and hypoxia-triggered differentiation therapy

Metastasis accounts for 90% of breast cancer deaths, where the lethality could be attributed to the poor drug accumulation at the metastatic loci. The tolerance to chemotherapy induced by breast cancer stem cells (BCSCs) and their particular redox microenvironment further aggravate the therapeutic dilemma. To be specific, therapy-resistant BCSCs can differentiate into heterogeneous tumor cells constantly, and simultaneously dynamic maintenance of redox homeostasis promote tumor cells to retro-differentiate into stem-like state in response to cytotoxic chemotherapy. Herein, we develop a specifically-designed biomimic platform employing neutrophil membrane as shell to inherit a neutrophil-like tumor-targeting capability, and anchored chemotherapeutic and BCSCs-differentiating reagents with nitroimidazole (NI) to yield two hypoxia-responsive prodrugs, which could be encapsulated into a polymeric nitroimidazole core. The platform can actively target the lung metastasis sites of triple negative breast cancer (TNBC), and release the escorted drugs upon being triggered by the hypoxia microenvironment. During the responsiveness, the differentiating agent could promote transferring BCSCs into non-BCSCs, and simultaneously the nitroimidazole moieties conjugated on the polymer and prodrugs could modulate the tumor microenvironment by depleting nicotinamide adenine dinucleotide phosphate hydrogen (NADPH) and amplifying intracellular oxidative stress to prevent tumor cells retro-differentiation into BCSCs. In combination, the BCSCs differentiation and tumor microenvironment modulation synergistically could enhance the chemotherapeutic cytotoxicity, and remarkably suppress tumor growth and lung metastasis. Hopefully, this work can provide a new insight in to comprehensively treat TNBC and lung metastasis using a versatile platform.

Discovery and preclinical evaluations of JBD0131, a novel nitrodihydro-imidazooxazole anti-tuberculosis agent

Multidrug-resistant pulmonary tuberculosis (MDR-TB) is a major health problem worldwide. The treatment for MDR-TB requires medications for a long duration (up to 20-24 months) with second-line drugs resulting in unfavorable outcomes. Nitroimidazoles are promising antimycobacterial agents known to inhibit both aerobic and anaerobic mycobacterial activity. Delamanid and pretomanid are two nitroimidazoles approved by the regulatory agencies for MDR-TB treatment. However, both agents possess unsatisfactory absorption and QTc prolongation. In our search for a safer nitroimidazole, we discovered JBD0131 (2). It exhibited excellent anti-mycobacterial activity against M. tuberculosis H37Rv in vitro and in vivo, improved PK and absorption, reduced QT prolongation potential of delamanid. JBD0131 is currently in clinical development in China for pulmonary tuberculosis (CTR20202308).

Hypoxia-responsive pullulan-based nanoparticles as erlotinib carriers

A hypoxia-responsive pullulan-based co-polymer was developed to assess its efficacy to deliver erlotinib (ERL) to the cervical cancer cells. Upon exposure to hypoxic condition, the synthesized and structurally characterized co-polymer i.e. succinyl pullulan-g-6-(2-nitroimidazole) hexylamine (Pull-SA-HA-NI) exhibited a hypochromic shift in the UV spectra and alteration in its self-assembled structures as compared to the control co-polymer, succinyl pullulan-g-hexylamine (Pull-SA-HA). Its corresponding ERL-loaded nanoparticles (NPs) displayed an attenuated crystallinity of pure ERL with excellent drug-trapping capacity (DEE, 94.23 ± 1.36%) and acceptable zeta potential (+39.21 ± 1.09 mV) and diameter (84.10 ± 2.10 nm) values. These also evidenced a faster drug release profile under hypoxic condition relative to the normoxic condition. The cellular internalization of the NPs was mediated through the energy-dependent endocytic process, which could utilize its multiple pathways (i.e., macropinocytosis, clathrin- and caveolae-mediated endocytosis). The ERL-loaded NPs suppressed HeLa cell proliferation and induced apoptosis more efficiently than the pristine drug.

In vitro evaluation and in vivo efficacy of nitroimidazole-sulfanyl ethyl derivatives against Leishmania (V.) braziliensis and Leishmania (L.) mexicana

The aim of this study was to synthesize several small molecules of the type 5-nitroimidazole-sulfanyl and evaluate biological properties against the main Leishmania species that cause cutaneous leishmaniasis in Venezuela. Final compounds 4-7 were generated through simple nucleophilic substitution of 1-(2-chloroethyl)-2-methyl-5-nitroimidazole 3 with 2-mercaptoethanol, 1-methyl-2-mercaptoethanol, and 2-thyolacetic acid derivative. Compound 8 was synthesized via a coupling reaction between 7 and (S)-Methyl 2-amino-4-methylpentanoate hydrochloride. The inhibitory concentrations of (3, 4, 7, 8) against Leishmania (L.) mexicana and (V.) braziliensis in promastigotes and experimentally infected macrophages were determined by in vitro activity assays. Compounds 7 and 8 shown high activity against both species of Leishmania and were selected for the in vivo evaluation. Animals were infected with promastigotes of the two species and divided into four groups of ten (10) animals and a control group. Intralesional injection way was used for the treatment. The parasitological diagnostic after treatment was obtained by PCR using species specific oligonucleotides. The two Leishmania species were susceptible to compounds 7 and 8 in vivo assays. The results indicated that both compounds reduce significantly (96%) the size of the lesion and cure 63% of the mice infected with L (L) mexicana or L (V) braziliensis as was determined by PCR. The results are indicating that both compounds may represent an alternative treatment for these two Leishmania species.

Identification of proteins and cellular pathways targeted by 2-nitroimidazole hypoxic cytotoxins

Tumour hypoxia negatively impacts therapy outcomes and continues to be a major unsolved clinical problem. Nitroimidazoles are hypoxia selective compounds that become entrapped in hypoxic cells by forming drug-protein adducts. They are widely used as hypoxia diagnostics and have also shown promise as hypoxia-directed therapeutics. However, little is known about the protein targets of nitroimidazoles and the resulting effects of their modification on cancer cells. Here, we report the synthesis and applications of azidoazomycin arabinofuranoside (N3-AZA), a novel click-chemistry compatible 2-nitroimidazole, designed to facilitate (a) the LC-MS/MS-based proteomic analysis of 2-nitroimidazole targeted proteins in FaDu head and neck cancer cells, and (b) rapid and efficient labelling of hypoxic cells and tissues. Bioinformatic analysis revealed that many of the 62 target proteins we identified participate in key canonical pathways including glycolysis and HIF1A signaling that play critical roles in the cellular response to hypoxia. Critical cellular proteins such as the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and the detoxification enzyme glutathione S-transferase P (GSTP1) appeared as top hits, and N3-AZA adduct formation significantly reduced their enzymatic activities only under hypoxia. Therefore, GAPDH, GSTP1 and other proteins reported here may represent candidate targets to further enhance the potential for nitroimidazole-based cancer therapeutics.

68Ga-labeled PET tracers for targeting tumor hypoxia: Role of bifunctional chelators on pharmacokinetics

INTRODUCTION

By virtue of their oxygen dependant accumulation in hypoxic cells, radiolabeled nitroimidazole analogues have been widely used for detecting tumor hypoxia. Present study evaluates two 2-nitroimidazole (2-NIM) based ⁶⁸Ga-labeled radiotracers, [⁶⁸Ga]Ga-DOTAGA-2-NIM and [⁶⁸Ga]Ga-NODAGA-2-NIM, for hypoxia targeting applications.

METHODS

Bifunctional chelating agents suitable for radiolabeling with ⁶⁸Ga, viz. 1,4,7,10-tetraazacyclododececane,1-(glutaric acid)-4,7,10-triacetic acid (DOTAGA) and 1,4,7-triazacyclododececane,1-(glutaric acid)-4,7-diacetic acid (NODAGA), were coupled to appropriately modified 2-nitroimidazole to obtain 2-NIM-DOTAGA and 2-NIM-NODAGA, respectively. These ligands were radiolabeled using [⁶⁸Ga]GaCl₃ obtained from a commercial ⁶⁸Ge/⁶⁸Ga-generator to obtain corresponding ⁶⁸Ga-complexes. Both the radiotracers were tested for their hypoxia selectivity in CHO cells under hypoxic and normoxic conditions. Biodistribution studies in fibrosarcoma tumor bearing Swiss mice were carried out to evaluate the radiotracer in vivo.

RESULTS

The ⁶⁸Ga complexes of 2-NIM-DOTAGA and 2-NIM-NODAGA could be prepared in ~82% and ~90% yield, respectively. In vitro studies of the complexes in CHO cells showed significant accumulation of [⁶⁸Ga]Ga-NODAGA-2-NIM complex under hypoxic conditions with hypoxic to normoxic ratio of 2.88 ± 0.36 at 180 min post incubation. The [⁶⁸Ga]Ga-DOTAGA-2-NIM complex also showed hypoxia selectivity albeit to a lesser extent. Biodistribution studies of the complexes in Swiss mice bearing fibrosarcoma tumor showed significant tumor uptake by both radiolabeled complexes. [⁶⁸Ga]Ga-NODAGA-2-NIM showed a more favorable pharmacokinetics with respect to [⁶⁸Ga]Ga-DOTAGA-2-NIM.

CONCLUSION

The nitroimidazole radiotracer with NODAGA chelator displayed more favorable pharmacokinetics and good hypoxia selectivity, making it a promising candidate for further investigation. The present study also provides an insight into the possible role of bifunctional chelator on overall pharmacokinetics of small molecule radiotracers.

Synthesis and evaluation of gallium-68-labeled nitroimidazole-based imaging probes for PET diagnosis of tumor hypoxia

OBJECTIVE

In this study, we designed and synthesized four novel ⁶⁸Ga-radiolabeled compounds ([⁶⁸Ga]DN-3, [⁶⁸Ga]DN-4, [⁶⁸Ga]NN-3, and [⁶⁸Ga]NN-4) composed of a nitroimidazole and two types of bifunctional chelates (DOTA or NOTA) via several alkyl linkers of different length. Then, we evaluated their properties as hypoxia imaging probes for positron emission tomography (PET) compared with conventional compounds ([⁶⁸Ga]DN-2 and [⁶⁸Ga]NN-2).

METHODS

The precursors of ⁶⁸Ga-radiolabeled compounds were synthesized through a two-step reaction, and then reacted with ⁶⁸GaCl₃ to be ⁶⁸Ga-radiolabeled compounds. FaDu cells were treated with ⁶⁸Ga-radiolabeled compounds and then incubated under normoxic (21% O₂) or hypoxic (1% O₂) conditions. The radioactivity of these cells was measured 2 h after incubation. The biodistribution and PET/CT imaging of ⁶⁸Ga-radiolabeled compounds in FaDu-bearing Balb/c nude mice were evaluated 2 h after intravenous injection.

RESULTS

The ⁶⁸Ga-radiolabeled compounds were synthesized with radiochemical purities over 95%. In the in vitro study, the levels of ⁶⁸Ga-radiolabeled compounds were significantly higher in hypoxic cells than in normoxic cells. In hypoxic cells, the compounds we designed in this study demonstrated higher accumulation than the conventional compounds. In the in vivo biodistribution study, [⁶⁸Ga]DN-3 exhibited the highest accumulation in tumor. In the in vivo PET/CT imaging study, the tumor tissues of the FaDu-xenografted mice were visualized at 2 h after intravenous administration of ⁶⁸Ga-radiolabeled compounds.

CONCLUSIONS

Our study suggested that the length of the linkers connecting nitroimidazole to a bifunctional chelate affect PET imaging of hypoxic tumors with ⁶⁸Ga-radiolabeled compounds.

Metronidazole-conjugates: A comprehensive review of recent developments towards synthesis and medicinal perspective

Nitroimidazoles based compounds remain a hot topic of research in medicinal chemistry due to their numerous biological activities. Moreover, many clinical candidates based on this chemical core have been reported to be valuable in the treatment of human diseases. Metronidazole (MTZ) derived conjugates demonstrated a potential application in medicinal chemistry research over the last decade. In this review, we summarize the synthesis, key structure-activity-relationship (SAR) and associated biological activities such as antimicrobial, anticancer, antidiabetic, anti-inflammatory, anti-HIV and anti-parasitic (Anti-trichomonas, antileishmanial, antiamoebic and anti-giardial) of explored MTZ-conjugates. The molecular docking analysis is also presented simultaneously, which will assist in developing an understanding towards designing of new MTZ-conjugates for target-based drug discovery against multiple disease areas.

Synthesis and evaluation of [99mTcN]2+ core and [99mTcO]3+ core labeled complexes with 4-nitroimidazole xanthate derivative for tumor hypoxia imaging

A 4-nitroimidazole xanthate ligand (NMXT) was synthesized and radiolabeled with [^99mTcN]²⁺ core and [^99mTcO]³⁺ core to obtain ^99mTcN-NMXT and ^99mTcO-NMXT, respectively. The two ^99mTc-complexes were prepared with high radiochemical purity and had good stability. The partition coefficient results indicated both of them were hydrophilic, and cellular uptake studies showed they exhibited good hypoxic selectivity. From the biodistribution study results, ^99mTcO-NMXT showed more favourable tumor uptake (1.73 ± 0.14 ID%/g) and higher tumor/muscle ratio (7.01 ± 0.16) than ^99mTcN-NMXT at 4 h post-injection. Single photon emission computed tomography (SPECT) imaging study of ^99mTcO-NMXT showed there was a visible accumulation in tumor site, suggesting it would be a promising candidate as a tumor hypoxia imaging agent.

Directed evolution of the B. subtilis nitroreductase YfkO improves activation of the PET-capable probe SN33623 and CB1954 prodrug

OBJECTIVES

To use directed evolution to improve YfkO-mediated reduction of the 5-nitroimidazole PET-capable probe SN33623 without impairing conversion of the anti-cancer prodrug CB1954.

RESULTS

Two iterations of error-prone PCR, purifying selection, and FACS sorting in a DNA damage quantifying GFP reporter strain were used to identify three YfkO variants able to sensitize E. coli host cells to at least 2.4-fold lower concentrations of SN33623 than the native enzyme. Two of these variants were able to be purified in a functional form, and in vitro assays revealed these were twofold and fourfold improved in k_cat/K_M with SN33623 over wild type YfkO. Serendipitously, the more-active variant was also nearly fourfold improved in k_cat/K_M versus wild type YfkO in converting CB1954 to a genotoxic drug.

CONCLUSIONS

The enhanced activation of the PET imaging probe SN33623 and CB1954 prodrug exhibited by the lead evolved variant of YfkO offers prospects for improved enzyme-prodrug therapy.

Development and biological investigations of hypoxia-sensitive prodrugs of the tyrosine kinase inhibitor crizotinib

Despite the huge success of tyrosine kinase inhibitors as anticancer agents, severe side effects are a major problem. In order to overcome this drawback, the first hypoxia-activatable 2-nitroimidazole-based prodrugs of the clinically approved ALK and c-MET inhibitor crizotinib were developed. The 2-aminopyridine functionality of crizotinib (essential for target kinase binding) was considered as ideal position for prodrug derivatization. Consequently, two different prodrugs were synthesized with the nitroimidazole unit attached to crizotinib either via carbamoylation (A) or alkylation (B) of the 2-aminopyridine moiety. The successful prodrug design could be proven by docking studies and a dramatically reduced ALK and c-MET kinase-inhibitory potential. Furthermore, the prodrugs showed high stability in serum and release of crizotinib in an enzymatic nitroreductase-based cleavage assay was observed for prodrug A. The in vitro activity of both prodrugs was investigated against ALK- and c-MET-dependent or -overexpressing cells, revealing a distinct hypoxia-dependent activation for prodrug A. Finally, inhibition of c-MET phosphorylation and cell proliferation could also be proven in vivo. In summary of the theoretical, chemical and biological studies, prodrug derivatization of the 2-aminopyridine position can be considered as a promising strategy to reduce the side effects and improve the anticancer activity of crizotinib.

Pursuing for the better lung cancer therapy effect: Comparison of two different kinds of hyaluronic acid and nitroimidazole co-decorated nanomedicines

Lung cancer remains the leading cause of cancer associated deaths worldwide. Compared with traditional chemotherapy for non-small cell lung cancer (NSCLC), specific targeted therapies are better choices for advanced patients to improve their survival. In this study, we attempted to fabricate Nitroimidazoles (NI) and Hyaluronic acid (HA) co-decorated, cisplatin (DDP) loaded polymeric nanoparticles (PNPs) (NI/HA-DDP-PNPs) and lipid-polymer hybrid nanoparticles (LPNs) (NI/HA-DDP-LPNs) for the facilitated drug delivery at lung tumor regions (hypoxic regions). In vitro cytotoxicity and cellular uptake; In vivo anti-tumor activity and in vivo tissue biodistribution of PNPs and LPNs were evaluated and compared in lung carcinoma cells and xenograft. Hydrodynamic size of NI/HA-DDP-LPNs was 185.6 ± 4.7 nm, which is larger than that of NI/HA-DDP-PNPs (136.7 ± 3.5 nm). The zeta potential of NI/HA-DDP-PNPs (-31.2 ± 2.7 mV) was more negative than NI/HA-DDP-LPNs (-22.3 ± 2.1 mV). The peak plasma concentration (C_max) achieved from NI/HA-DDP-PNPs and NI/HA-DDP-LPNs was 35.2 ± 1.6 and 37.3 ± 1.7 μg/mL. The half-life (T_1/2) of NI/HA-DDP-PNPs and NI/HA-DDP-LPNs was 12.03 ± 0.75 and 11.78 ± 0.89 h. Area Under Curve (AUC) of NI/HA-DDP-PNPs and NI/HA-DDP-LPNs showed no significant difference while greater than other groups. NI/HA-DDP-LPNs exhibited excellent antitumor effect against drug-resistant human lung cancer A549/DDP cells in vitro and in vivo, better than that of NI/HA-DDP-PNPs. Considering that the low toxicity of NI/HA-DDP-LPNs and NI/HA-DDP-PNPs, NI/HA-DDP-LPNs could be a more promising system for lung cancer targeted therapy.

Electron Ionization of Imidazole and Its Derivative 2-Nitroimidazole

Imidazole (IMI) is a basic building block of many biologically important compounds. Thus, its electron ionization properties are of major interest and essential for the comparison with other molecular targets containing its elemental structure. 2-Nitroimidazole (2NI) contains the imidazole ring together with nitrogen dioxide bound to the C2 position, making it a radiosensitizing compound in hypoxic tumors. In the present study, we investigated electron ionization of IMI and 2NI and determined the mass spectra, the ionization energies, and appearance energies of the most abundant fragment cations. The experiments were complemented by quantum chemical calculations on the thermodynamic thresholds and potential energy surfaces, with particular attention to the calculated transition states for the most important dissociation reactions. In the case of IMI, substantially lower threshold values (up to ~ 1.5 eV) were obtained in the present work compared to the only available previous electron ionization study. Closer agreement was found with recent photon ionization values, albeit the general trend of slightly higher values for the case of electron ionization. The only exception for imidazole was found in the molecular cation at m/z 40 which is tentatively assigned to the quasi-linear HCCNH+/ HCNCH+. Electron ionization of 2NI leads to analogous fragment cations as in imidazole, yet different dissociation pathways must be operative due to the presence of the NO2 group. Regarding the potential radiosensitization properties of 2NI, electron ionization is characterized by dominant parent cation formation and release of the neutral NO radical.

Novel benzoxaborole, nitroimidazole and aminopyrazoles with activity against experimental cutaneous leishmaniasis

OBJECTIVES

Drugs for Neglected Diseases initiative (DNDi) has identified three chemical lead series, the nitroimidazoles, benzoxaboroles and aminopyrazoles, as innovative treatments for visceral leishmaniasis. The leads discovered using phenotypic screening, were optimised following disease- and compound-specific criteria. Several leads of each series were progressed and preclinical drug candidates have been nominated. Here we evaluate the efficacy of the lead compounds of each of these three chemical classes in in vitro and in vivo models of cutaneous leishmaniasis.

METHODS

The in vitro activity of fifty-five compounds was evaluated against the intracellular amastigotes of L. major, L. aethiopica, L. amazonensis, L. panamensis, L. mexicana and L. tropica. The drugs demonstrating potent activity (EC50 < 5 μM) against at least 4 of 6 species were subsequently evaluated in vivo in different L. major - BALB/c mouse models using a 5 or 10-day treatment with either the oral or topical formulations. Efficacy was expressed as lesion size (measured daily using callipers), parasite load (by quantitative PCR - DNA) and bioluminescence signal reduction relative to the untreated controls.

RESULTS

The selected drug compounds (3 nitroimidazoles, 1 benzoxaborole and 3 aminopyrazoles) showed consistent and potent activity across a range of Leishmania species that are known to cause CL with EC50 values ranging from 0.29 to 18.3 μM. In all cases, this potent in vitro antileishmanial activity translated into high levels of efficacy with a linear dose-response against murine CL. When administered at 50 mg/kg/day, DNDI-0690 (nitroimidazole), DNDI-1047 (aminopyrazole) and DNDI-6148 (benzoxaborole) all resulted in a significant lesion size reduction (no visible nodule) and an approximate 2-log-fold reduction of the parasite load as measured by qPCR compared to the untreated control.

CONCLUSIONS

The lead compounds DNDI-0690, DNDI-1047 and DNDI-6148 showed excellent activity across a range of Leishmania species in vitro and against L. major in mice. These compounds offer novel potential drugs for the treatment of CL.

Preparation and preliminary evaluation of bio-nanocomposites based on hydroxyapatites with antibacterial properties against anaerobic bacteria

Hexagonal nanocrystalline powders of the non-doped Ca₁₀(PO₄)₆(OH)₂ as well as activated with Ag⁺ and Eu³⁺ ions were synthesized by using different wet chemistry methods. Moreover, the obtained hydroxyapatite was loaded with Ag⁰, as well as nitroimidazole antimicrobials: metronidazole and tinidazole. The structural properties of the products were analyzed by X-ray diffraction (XRD), scanning (SEM) and transmission (TEM) electron microscopy as well as infrared (IR) and Raman spectroscopy. The photoluminescence properties of the Eu³⁺ and Ag⁺ co-doped Ca₁₀(PO₄)₆(OH)₂ were characterized via the PL emission, excitation spectra and the luminescence decay curve. The antimicrobial activity of the obtained materials against Prevotella bivia and Parabacteroides distasonis was studied. The cytotoxicity assessment was carried out on the human osteosarcoma cell line (U2OS) as well as human red blood cells (RBC). The choice of the in vitro model was based on the fact that U2OS is a cancer cell line derived from bone tissue which is rich in apatites that play a pivotal role in the extracellular matrix formation. RBCs are the most abundant blood cells and they are used as a cell model in the study of biocompatibility of new prepared biocompounds with potential medical applications. The obtained multifunctional materials do not exhibit the haemolytic activity, therefore, they could be used as a promising antimicrobial agent and for anaerobic bacteria.

Nitroimidazole-containing compounds and their antibacterial and antitubercular activities

Infections especially tuberculosis caused by various bacteria including mycobacteria result in millions of lives every year, but the control of bacterial infections is challenged by the limitation of effective pharmaceuticals against drug-resistant pathogens. Nitroimidazoles belong to a group of nitroheterocyclic compounds that have broad-spectrum activity against a series of organisms such as mycobacteria, anaerobic Gram-positive and Gram-negative bacteria, and some of them have already been used in clinics or under clinical trials for the treatment of infectious diseases. In this review, we made an overview of the recent advances in nitroimidazole-containing compounds with antibacterial and antitubercular activity in the recent 20 years.

Adsorption of nitroimidazole antibiotics from aqueous solutions on self-shaping porous biomass carbon foam pellets derived from Vallisneria natans waste as a new adsorbent

Powdered biomass adsorbents can potentially remove antibiotics from wastewater. However, recovering or separating the adsorbents after use is difficult. The preparation of mold-assisted shaping of biomass carbon foam pellets (BCFPs) without compaction and addition of binder instead of powdered adsorbent, is rarely reported. Therefore, the study explored the formation mechanism of BCFPs by using Vallisneria natans (V. natans) waste as precursor and investigated the adsorption performance and mechanisms of metronidazole (MNZ) and dimetridazole (DMZ) onto BCFPs. The optimal preparation conditions were V. natans-and-ZnCl₂ mass ratio of 1:2.4, carbonization temperature of 600 °C, and time of 90 min. BCFPs exhibited uniform size, excellent floatability, and abundant micropores. The Brunauer-Emmett-Teller specific surface area, total pore volume, and micropore volume of BCFPs were 922.56 m² g^-1, 0.421 cm³ g^-1, and 0.386 cm³ g^-1, respectively. The adsorption process of MNZ and DMZ was both described well by pseudo-first-order kinetic model. However, the isotherm data fitted well with Langmuir for MNZ and Dubinin-Radushkevic model for DMZ, with a maximum monolayer adsorption capacity of 64.23 and 82.58 mg g^-1, respectively. The nature of the adsorption process is endothermic and spontaneous. The adsorption mechanisms of MNZ and DMZ onto BCFPs were mainly hydrogen bonding, π-π interactions, and micropore filling. Preparation of BCFPs with high mechanical strength and excellent adsorption capacity from V. natans waste without compaction and any binder is feasible. Furthermore, BCFPs are easily separated and recyclable adsorbents, and their average recovery rate was 99.6%.

Comparative evaluation of [18F]DiFA and its analogs as novel hypoxia positron emission tomography and [18F]FMISO as the standard

INTRODUCTION

Hypoxia, a common feature of most solid tumors, is an important predictor of tumor progression and resistance to radiotherapy. We developed a novel hypoxia imaging probe with optimal biological characteristics for use in clinical settings.

METHODS

We designed and synthesized several new hypoxia probes with additional hydrophilic characteristics compared to [¹⁸F]fluoromisonidazole ([¹⁸F]FMISO). These were 1-(2,2-Dihydroxy-methyl-3-[¹⁸F]-Fluoropropyl) azomycin ([¹⁸F]DiFA, formerly [¹⁸F]HIC101) and its analogs ([¹⁸F]F1 and [¹⁸F]F2). Biodistribution studies with EMT6 mammary carcinoma cell-bearing mice were performed 1 and 2 h after injection of each probe. Small-animal positron emission tomography (PET) imaging studies were conducted using [¹⁸F]DiFA and [¹⁸F]FMISO in the same mice. Tumoral hypoxia was confirmed via pimonidazole staining. Ex vivo digital autoradiographs were obtained for confirming the co-localization of [¹⁸F]DiFA and pimonidazole in the tumor tissues.

RESULTS

The EMT6 tumors used had pimonidazole-positive regions. In biodistribution studies, the tumor-to-blood ratio and tumor-to-muscle ratio of [¹⁸F]DiFA was significantly higher than the respective [¹⁸F]FMISO ratios 1 h after injection. Hence, we selected [¹⁸F]DiFA as the best hypoxia probe among those tested. Small-animal PET imaging studies showed time-dependent increases in the tumor-to-normal tissue ratio of [¹⁸F]DiFA uptake. Rapid clearance from the rest of the body was observed primarily via the renal system. Ex vivo autoradiography showed a positive correlation between [¹⁸F]DiFA uptake and the regions of pimonidazole distribution, indicating that [¹⁸F]DiFA selectively accumulated in the tumor tissue's hypoxic region.

CONCLUSIONS

A better contrast image and a shorter waiting time may be obtained with [¹⁸F]DiFA than with [¹⁸F]FMISO.

ADVANCES IN KNOWLEDGE

By optimizing LogP based on the [¹⁸F]FMISO structure, we demonstrated that [¹⁸F]DiFA could detect tumor hypoxia regions at an early time point. IMPLICATIONS FOR PATIENT CARE: [¹⁸F]DiFA imaging facilitates the evaluation of various cancer hypoxic states due to the lower uptake of normal tissues and could contribute to novel treatment development.

Nitroimidazole derivative incorporated liposomes for hypoxia-triggered drug delivery and enhanced therapeutic efficacy in patient-derived tumor xenografts

Hypoxia is not merely a tumor microenvironment byproduct, but rather an active participant in tumor development, invasion, and metastasis. Hypoxia contributes to poor outcomes in tumor treatment and has currently emerged as an important therapeutic target. In this work, a facile hypoxia-responsive liposomal drug delivery system was developed by incorporating derivatized nitroimidazole into liposome membranes. Under hypoxic conditions, hypoxia-induced reductive metabolism of the nitroimidazole derivative facilitated disassembly of the liposomes for triggered drug release. The liposomes showed high sensitivity to hypoxia, even at the cellular level, and could release payload in an oxygen-dependent manner, leading to high cytotoxicity in hypoxic conditions. In vivo fluorescence imaging revealed that there was a selective release of the liposomes at the hypoxic tumor site. As a result, the liposomes exhibited enhanced therapeutic efficacy in treating a hypoxic tumor in both cell line-derived and clinically relevant patient-derived xenograft models. Thus, hypoxia-responsive liposomes are a promising drug delivery system for hypoxia targeted tumor therapy. STATEMENT OF SIGNIFICANCE: 1. A facile but smart hypoxia-responsive liposomal drug delivery system is developed by incorporating nitroimidazole derivative, one of representative hypoxia-responsive moieties, into phospholipid bilayer of the liposomes. 2. The liposomes show extremely high sensitivity to hypoxia and can selectively release payload in hypoxic cells and hypoxic tumor. 3. The liposomes show enhanced therapeutic efficacy not only in cell line-derived xenograft model but also in clinically relevant patient-derived xenograft model, indicating their promising prospect in clinical application.

99mTc labelled complexes with secnidazole xanthate: Synthesis and evaluation as potential radiotracers to target tumor hypoxia

In this study, the commercially available secnidazole was successfully converted to secnidazole xanthate (SNXT), in which the xanthate group can act as a bifunctional chelator to coordinate with ^99mTc. ^99mTc-nitrido complex of SNXT(^99mTcN-SNXT) and ^99mTc-oxo complex of SNXT(^99mTcO-SNXT) were prepared with high radiochemical purity. Both of the complexes were found to be stable in vitro and to exhibit similar hydrophilicity. In addition, comparative in vitro cell uptake studies under anoxic and normoxic conditions demonstrated that both agents were preferentially taken up by hypoxic cells. Biodistribution studies in mice bearing S180 tumor showed ^99mTcO-SNXT exhibited a higher tumor uptake and tumor-to-muscle ratio than ^99mTcN-SNXT. Furthermore, in SPECT imaging study, ^99mTcO-SNXT exhibited a clear accumulation in tumor at 2 h post-injection, suggesting its potential to be a novel hypoxia imaging agent.

Secnidazole for control of giardiasis in dairy calves

The aim of this study was to verify whether secnidazole, given in a single oral dose (10 mg/kg), decreases or eliminates the excretion of Giardia duodenalis cysts. Holstein calves were raised from birth to 15 ± 2 days of age in individual stalls. Subsequently, 12 calves were grouped and housed in collective stalls. After seven days (day of life 21), we collected stool samples directly from the rectal ampulla in order to determine the degree of parasitic infection. Fecal examination was performed by a centrifugal-flotation technique, which allows for visualization and quantification of G. duodenalis cysts. After division into control and treatment groups, six animals were treated with one 400 mg secnidazole capsule. The first stool collection following treatment was performed on day 5 and the second on day 30. This experiment was repeated at 15 days, with a total of 24 calves studied. Animals on the farm where the experiment was conducted often suffer from giardiasis, despite hygiene care (disinfection) and adequate facilities. All 24 calves were excreting G. duodenalis cysts prior to starting treatment. Five days after receiving the treatment, animals in the experiment group were Giardia-negative, i.e., they did not excrete parasite cysts, whereas calves in the control group continued to excrete cysts. After 30 days of treatment, the stool of most treated animals (83.3%) remained free of G. duodenalis cysts. Therefore, we believe that secnidazole was 100% effective in eliminating the excretion of Giardia duodenalis cysts.

Recent advances of imidazole-containing derivatives as anti-tubercular agents

Tuberculosis still remains one of the most common, communicable, and leading deadliest diseases known to mankind throughout the world. Drug-resistance in Mycobacterium tuberculosis which threatens to worsen the global tuberculosis epidemic has caused great concern in recent years. To overcome the resistance, the development of new drugs with novel mechanisms of actions is of great importance. Imidazole-containing derivatives endow with various biological properties, and some of them demonstrated excellent anti-tubercular activity. As the most emblematic example, 4-nitroimidazole delamanid has already received approval for treatment of multidrug-resistant tuberculosis infected patients. Thus, imidazole-containing derivatives have caused great interests in discovery of new anti-tubercular agents. Numerous of imidazole-containing derivatives were synthesized and screened for their in vitro and in vivo anti-mycobacterial activities against both drug-sensitive and drug-resistant Mycobacterium tuberculosis pathogens. This review aims to outline the recent advances of imidazole-containing derivatives as anti-tubercular agents, and summarize the structure-activity relationship of these derivatives. The enriched structure-activity relationship may pave the way for the further rational development of imidazole-containing derivatives as anti-tubercular agents.

Assessment of a pretomanid analogue library for African trypanosomiasis: Hit-to-lead studies on 6-substituted 2-nitro-6,7-dihydro-5H-imidazo[2,1-b][1,3]thiazine 8-oxides

A 900 compound nitroimidazole-based library derived from our pretomanid backup program with TB Alliance was screened for utility against human African trypanosomiasis (HAT) by the Drugs for Neglected Diseases initiative. Potent hits included 2-nitro-6,7-dihydro-5H-imidazo[2,1-b][1,3]thiazine 8-oxides, which surprisingly displayed good metabolic stability and excellent cell permeability. Following comprehensive mouse pharmacokinetic assessments on four hits and determination of the most active chiral form, a thiazine oxide counterpart of pretomanid (24) was identified as the best lead. With once daily oral dosing, this compound delivered complete cures in an acute infection mouse model of HAT and increased survival times in a stage 2 model, implying the need for more prolonged CNS exposure. In preliminary SAR findings, antitrypanosomal activity was reduced by removal of the benzylic methylene but enhanced through a phenylpyridine-based side chain, providing important direction for future studies.

In vitro anti-tuberculosis activity of azole drugs against Mycobacterium tuberculosis clinical isolates

BACKGROUND

Latent tuberculosis has been associated with the persistence of dormant Mycobacterium tuberculosis in the organism of infected individuals, who are reservoirs of the bacilli and the source for spreading the disease in the community. New active anti-TB drugs exerting their metabolic action at different stages and on latent/dormant bacilli are urgently required to avoid endogenous reactivations and to be part of treatments of multi- and extensively-drug resistant tuberculosis (M/XDR-TB). It was previously reported that azole drugs are active against M. tuberculosis. For that reason, the aims of this study were to determine the in vitro activity of azole drugs, imidazole (clotrimazole, CLO and econazole, ECO) and nitroimidazole (metronidazole, MZ and ipronidazole, IPZ), against a collection of MDR M. tuberculosis clinical isolates; and to analyze their potential use in both the LTB and the active forms of M/XDR-TB treatments.

METHODS

A total of 55 MDR M. tuberculosis isolates and H37Rv were included. MZ and IPZ activity against M. tuberculosis isolates were tested using anaerobic culture conditions. The activity of ECO and CLO was measured by the minimal inhibitory concentration (MIC) using a microdilution colorimetric method.

RESULTS

MZ and IPZ showed bacteriostatic activity against M. tuberculosis strains. MIC₅₀ and MIC₉₀ to ECO was 4.0μg/ml, while MIC₅₀ to CLO was 4.0μg/ml and MIC₉₀ was 8.0μg/ml respectively.

CONCLUSION

All azole compounds tested in the study showed inhibitory activity against MDR M. tuberculosis clinical isolates.

Nitroimidazole-refractory giardiasis: a growing problem requiring rational solutions

BACKGROUND

Giardia intestinalis is microaerophilic diarrhoea-causing protozoan common in countries with suboptimal sanitation. Standard treatment is with nitroimidazoles, but a growing number of refractory cases is being reported. Treatment failure has become increasingly prevalent in travellers who contract giardiasis in Asia. Clinicians are increasingly falling back on second-line and less well-known drugs to treat giardiasis.

AIMS

To review nitroimidazole-refractory G. intestinalis infection, examine the current efficacy of standard therapeutic agents, consider potential resistance mechanisms which could cause treatment failure and describe the practical aspects of managing this emerging clinical problem.

SOURCES

A PubMed search was conducted using combinations of the following terms: refractory, Giardia, giardiasis, resistance and treatment. Articles on the pharmacotherapy, drug resistance mechanisms and use of alternative agents in nitroimidazole-refractory giardiasis were reviewed.

CONTENT

We review the standard drugs for giardiasis, including their efficacy in initial treatment, mode of action and documented in vitro and in vivo drug resistance. We assess the efficacy of alternative drugs in nitroimidazole-refractory disease. Existing data suggest a potential advantage of combination treatment.

IMPLICATIONS

An optimal treatment strategy for refractory giardiasis has still to be determined, so there is no standard treatment regimen for nitroimidazole-refractory giardiasis. Further work on drug resistance mechanisms and the use of drug combinations in this condition is a priority.

Delamanid is not metabolized by Salmonella or human nitroreductases: A possible mechanism for the lack of mutagenicity

Nitro-containing compounds such as nitrofuran and nitroimidazole are drugs used for the treatment of infectious diseases. However, many of these nitro-containing drugs are positive in the bacterial reverse mutation assay (Ames test). The recently approved anti-multidrug-resistant tuberculosis (MDR-TB) drug, delamanid (Deltyba™; OPC-67683), a derivative of 4-nitroimidazole, was negative for mutagenicity in the Ames assay. In Salmonella typhimurium, mutagenicity of nitro compounds has been closely associated with the ability of nitroreductase to metabolize (degradation)these compounds. To explore the lack of mutagenicity for delamanid, we examined the initial metabolic rate and mutagenic-specific activity of a series of nitro compounds in S. typhimurium TA100. The order of maximum mutagenic-activity was nitrofuran > 2-nitroimidazole > 5-nitroimidazole ≥ 4-nitroimidazole, which is very similar to the order of initial metabolic rate, i.e., the Pearson's correlation coefficient (r = 0.85) showed a correlation between metabolic rate and mutagenic-activity. No metabolism of delamanid was detected even after 60 h of treatment. In addition, delamanid was not reduced by two human nitroreductases. These facts may explain the absence of genotoxicity of delamanid in both in vitro and in vivo tests.

Effect of common and experimental anti-tuberculosis treatments on Mycobacterium tuberculosis growing as biofilms

Much is known regarding the antibiotic susceptibility of planktonic cultures of Mycobacterium tuberculosis, the bacterium responsible for the lung disease tuberculosis (TB). As planktonically-grown M. tuberculosis are unlikely to be entirely representative of the bacterium during infection, we set out to determine how effective a range of anti-mycobacterial treatments were against M. tuberculosis growing as a biofilm, a bacterial phenotype known to be more resistant to antibiotic treatment. Light levels from bioluminescently-labelled M. tuberculosis H37Rv (strain BSG001) were used as a surrogate for bacterial viability, and were monitored before and after one week of treatment. After treatment, biofilms were disrupted, washed and inoculated into fresh broth and plated onto solid media to rescue any surviving bacteria. We found that in this phenotypic state M. tuberculosis was resistant to the majority of the compounds tested. Minimum inhibitory concentrations (MICs) increased by 20-fold to greater than 1,000-fold, underlying the potential of this phenotype to cause significant problems during treatment.

Preparation of alkyne-labeled 2-nitroimidazoles for identification of tumor hypoxia by Raman spectroscopy

Hypoxia is a characteristic feature of solid tumors. Herein, we have developed novel hypoxia-sensitive probes (IM-ACs) for Raman spectroscopic analysis, consisting of nitroimidazole as a hypoxia-targeting unit and acetylene group as the signal-emitting unit. Among IM-ACs synthesized in this study, IM-AC possessing a diacetylene group (IM-AC 3), showed suitable properties as a hypoxia indicator. When administered to A549 cells, we observed a strong signal of IM-AC 3 around 2200cm^-1 in the Raman spectra from hypoxic cells. Ex vivo experiments suggest that IM-AC 3 remained in hypoxic tumor tissue and emitted a strong signal.

Development and validation of a highly sensitive LC-MS/MS-ESI method for quantification of IIIM-019-A novel nitroimidazole derivative with promising action against Tuberculosis: Application to drug development

The study aims to illustrate an analytical validation of a rapid and sensitive liquid chromatography (LC) coupled to tandem mass spectrometry (MS-MS) and electrospray ionization (ESI) method for quantification of IIIM-019 (a novel nitroimidazole derivative with potential activity against Tuberculosis) in mice plasma. The extraction of the analyte and the internal standard (Tolbutamide) from the plasma samples involves protein precipitation using acetonitrile. The chromatographic separation was accomplished using a gradient mode and the mobile phase comprised of acetonitrile and 0.1% formic acid in water. The flow rate used was 0.7 ml/min on a C18e high performance Chromolith column. IIIM-019 and Tolbutamide (IS) were analyzed by combined reversed-phase LC/MS-MS with positive ion electrospray ionization. The MS-MS ion transitions used were 533>170.1, 533>198 for IIIM-019 and 271>74, 271>155 for internal standard (IS) respectively. The method was linear over a concentration range of 0.5-1000 ng/ml and the lower limit of quantification was 0.50 ng/ml. The entire study was validated for accuracy, precision, linearity, range, selectivity, lower limit of quantification (LLOQ), recovery, and matrix effect in accordance with the FDA guidelines of method validation. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. The intra and inter-day precisions were in the range of 0.51-11.18% and 0.51-7.55%. The pharmacokinetics was performed on male Balb/c mice by oral (2.5mg/kg), intraperitoneal (2.5mg/kg) and intravenous (1mg/kg) routes. The oral bioavailability of IIIM-019 was 51.6%. The method was also applied successfully in determining microsomal stability wherein the compound was found to be very slightly metabolized by rat liver microsomes.

Nitroimidazole carboxamides as antiparasitic agents targeting Giardia lamblia, Entamoeba histolytica and Trichomonas vaginalis

Diarrhoeal diseases caused by the intestinal parasites Giardia lamblia and Entamoeba histolytica constitute a major global health burden. Nitroimidazoles are first-line drugs for the treatment of giardiasis and amebiasis, with metronidazole 1 being the most commonly used drug worldwide. However, treatment failures in giardiasis occur in up to 20% of cases and development of resistance to metronidazole is of concern. We have re-examined 'old' nitroimidazoles as a foundation for the systematic development of next-generation derivatives. Using this approach, derivatisation of the nitroimidazole carboxamide scaffold provided improved antiparasitic agents. Thirty-three novel nitroimidazole carboxamides were synthesised and evaluated for activity against G. lamblia and E. histolytica. Several of the new compounds exhibited potent activity against G. lamblia strains, including metronidazole-resistant strains of G. lamblia (EC50 = 0.1-2.5 μM cf. metronidazole EC50 = 6.1-18 μM). Other compounds showed improved activity against E. histolytica (EC50 = 1.7-5.1 μM cf. metronidazole EC50 = 5.0 μM), potent activity against Trichomonas vaginalis (EC50 = 0.6-1.4 μM cf. metronidazole EC50 = 0.8 μM) and moderate activity against the intestinal bacterial pathogen Clostridium difficile (0.5-2 μg/mL, cf. metronidazole = 0.5 μg/mL). The new compounds had low toxicity against mammalian kidney and liver cells (CC50 > 100 μM), and selected antiparasitic hits were assessed for human plasma protein binding and metabolic stability in liver microsomes to demonstrate their therapeutic potential.

Metronidazole-triazole conjugates: activity against Clostridium difficile and parasites

Metronidazole has been used clinically for over 50 years as an antiparasitic and broad-spectrum antibacterial agent effective against anaerobic bacteria. However resistance to metronidazole in parasites and bacteria has been reported, and improved second-generation metronidazole analogues are needed. The copper catalysed Huigsen azide-alkyne 1,3-dipolar cycloaddition offers a way to efficiently assemble new libraries of metronidazole analogues. Several new metronidazole-triazole conjugates (Mtz-triazoles) have been identified with excellent broad spectrum antimicrobial and antiparasitic activity targeting Clostridium difficile, Entamoeba histolytica and Giardia lamblia. Cross resistance to metronidazole was observed against stable metronidazole resistant C. difficile and G. lamblia strains. However for the most potent Mtz-triazoles, the activity remained in a therapeutically relevant window.

•

A series of 20 metronidazole (Mtz)-triazole conjugates were synthesised.

•

Several Mtz-triazoles had increased potency against pathogenic anaerobes.

•

The compounds were not cytotoxic at 100 μM against mammalian cell lines.

•

Cross-resistance was observed against Mtz-resistant bacteria and parasites.

•

Therapeutically relevant activity was retained against Mtz-resistant G. lamblia.

Action of nitroheterocyclic drugs against Clostridium difficile

The nitroheterocyclic classes of drugs have a long history of use in treating anaerobic infections, as exemplified by metronidazole as a first-line treatment for mild-to-moderate Clostridium difficile infection (CDI). Since direct comparisons of the three major classes of nitroheterocyclic drugs (i.e. nitroimidazole, nitazoxanide and nitrofurans) and nitrosating agents against C. difficile are under-examined, in this study their actions against C. difficile were compared. Results show that whilst transient resistance occurs to metronidazole and nitazoxanide, stable resistance arises to nitrofurans upon serial passage. All compounds killed C. difficile at high concentrations in addition to the host defence nitrosating agent S-nitrosoglutathione (GSNO). This suggests that GSNO killing of C. difficile contributes to its efficacy in murine CDI. Although nitric oxide production could not be detected for the nitroheterocyclic drugs, the cellular response to metronidazole and nitrofurans has some overlap with the response to GSNO, causing significant upregulation of the hybrid-cluster protein Hcp that responds to nitrosative stress. These findings provide new insights into the action of nitroheterocyclic drugs against C. difficile.

Novel nitroimidazole alkylsulfonamides as hypoxic cell radiosensitisers

A novel class of nitroimidazole alkylsulfonamides have been prepared and evaluated as hypoxia-selective cytotoxins and radiosensitisers. The sulfonamide side chain markedly influences the physicochemical properties of the analogues: lowering aqueous solubility and raising the electron affinity of the nitroimidazole group. The addition of hydroxyl or basic amine groups increased aqueous solubility, with charged amine groups contributing to increased electron affinity. The analogues covered the range of electron affinity for effective radiosensitisation with one-electron reduction potentials ranging from -503 to -342mV. Cytotoxicity under normoxia or anoxia against a panel of human tumour cell lines was determined using a proliferation assay. 2-Nitroimidazole sulfonamides displayed significant hypoxia-selective cytotoxicity (6 to 64-fold), while 4- and 5-nitroimidazole analogues did not display hypoxia-selective cytotoxicity. All analogues sensitised anoxic HCT-116 human colorectal cells to radiation at non-toxic concentrations. 2-Nitroimidazole analogues provided modest sensitisation due to the relatively low concentrations used while several 5-nitroimidazole analogues provided equivalent sensitisation to misonidazole and etanidazole at similar molar concentrations.

Schiff's base derivatives bearing nitroimidazole and quinoline nuclei: new class of anticancer agents and potential EGFR tyrosine kinase inhibitors

New Schiff's base derivatives 5a-j have been synthesized by reaction between 2-phenoxyquinoline-3-carbaldehydes 3a-j and 2-(2-methyl-5-nitro-1H-imidazol-1-yl)acetohydrazide 4 in presence of nickel(II) nitrate as a catalyst in ethanol under reflux in good yield (78-92%). All compounds were tested for anticancer and inhibition of EGFR. Of the compounds studied, majority of the compounds showed effective antiproliferation and inhibition of EGFR and HER-2 activities. Compound 5h showed most effective inhibition (IC50=0.12±0.05 μM) by binding in to the active pocket of EGFR receptor with minimum binding energy (ΔGb=-58.3691 kcal/mol). The binding was stabilized by two hydrogen bonds, two π-cation and one π-sigma interactions. Compound 5d showed most effective inhibition (IC50=0.37±0.04 μM).

[New tuberculosis drugs in resistant and multiresistant tuberculosis]

Drug-resistant tuberculosis is a globally emerging problem with a rising incidence. According to the WHO in 2008, 17% of strains of Mycobacterium tuberculosis, in untreated cases were resistant to at least one drug and 3.6% were resistant to rifampicin and isoniazid, which is called multidrug-resistant tuberculosis. The problem is greater in patients previously treated and in some countries, where rates of multidrug resistance reach 60%. Approximately 5% of multidrug-resistant tuberculosis patients are also resistant to any fluoroquinolone and at least one injectable drug, being called extensively drug-resistant tuberculosis. The treatment of these forms of tuberculosis requires the use of second-line drugs, which causes higher cost, higher toxicity and a longer duration of treatment. There is a need for new compounds with efficacy and safety profiles better than those currently used to treat these forms of tuberculosis. In the last decade different drugs have being reassessed and appeared, which are at different stages of development.

Cytotoxic effect of some 1, 4-dihydropyridine derivatives containing nitroimidazole moiety

The 1,4-dihydropyridine (DHP) derivatives are a known class of calcium channel blockers. Some derivatives of DHP showed significant cytotoxicity. It was shown that this effect may not be the result of interaction with Ca(2+) channels. In this study, we performed an investigation about the intrinsic cytotoxicity of some derivatives of DHP containing nitroimidazole moiety on their C4 position on four different cancer cell lines (Raji, K562, Fen and HeLa). The result showed that these compounds had moderate-good cytotoxic activity. In addition, QSAR model shows the importance of N atom in cytotoxicity; Ca(2+) channels.