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We present here an improved procedure for the preparation of the promising antitubercular drug SQ109 that is currently in phase Ib/III of clinical trials against Mycobacterium tuberculosis. We investigated and tested the literature synthetic procedure that enables the development of structure–activity relationships and report the observed inconsistencies as well as presenting improvements or novelties for the more efficient preparation of SQ109. Most significantly we applied a novel reduction step of the aminoamide precursor using Me3SiCl­/LiAlH4 under mild conditions. These findings are important for research groups investigating the efficacy of this drug and analogues in academia and industry.

The causative agent of tuberculosis (TB), Mycobacterium tuberculosis and more recently totally drug-resistant strains of M. tuberculosis, display unique mechanisms to survive in the host. A four-drug treatment regimen was introduced 40 years ago but the emergence of multidrug-resistance and more recently TDR necessitates the identification of new targets and drugs for the cure of M. tuberculosis infection. The current efforts in the drug development process are insufficient to completely eradicate the TB epidemic. For almost five decades the TB drug development process remained stagnant. The last 10 years have made sudden progress giving some new and highly promising drugs including bedaquiline, delamanid, and pretomanid. Many of the candidates are repurposed compounds, which were developed to treat other infections but later, exhibited anti-TB properties also. Each class of drug has a specific target and a definite mode of action. These targets are either involved in cell wall biosynthesis, protein synthesis, DNA/RNA synthesis, or metabolism. This review discusses recent progress in the discovery of newly developed and Food and Drug Administration approved drugs as well as repurposed drugs, their targets, mode of action, drug-target interactions, and their structure-activity relationship.

SQ109 is a novel well-tolerated drug candidate in clinical development for the treatment of drug resistant tuberculosis (TB). It is the only inhibitor of the MmpL3 mycolic acid transporter in clinical development. No SQ109 resistant mutant has been directly isolated thus far, in vitro, in mice or in patients, tentatively attributed to its multiple targets. It is considered as a potential replacement for poorly tolerated components of multidrug-resistant TB regimens. To prioritize SQ109-containing combinations with best potential for cure and treatment shortening, one must understand its contribution against different bacterial populations in pulmonary lesions. Here we have characterized the pharmacokinetics of SQ109 in the rabbit model of active TB and its penetration at the sites of disease: lung tissue, cellular and necrotic lesions, and caseum. A two-compartment model with first-order absorption and elimination described the plasma pharmacokinetics. At the human-equivalent dose, parameter estimates fell within the ranges published for preclinical species. Tissue concentrations were modelled using an "effect" compartment, showing high accumulation in lung and cellular lesion areas with penetration coefficients in excess of 1,000, and lower passive diffusion in caseum after 7 daily doses. These results, together with the hydrophobic nature and high non-specific caseum binding of SQ109, suggest that multi-week dosing would be required to reach steady state in caseum and poorly vascularized compartments, similar to bedaquiline. Linking lesion pharmacokinetics to SQ109 potency in assays against replicating, non-replicating, and intracellular M. tuberculosis showed SQ109 concentrations markedly above pharmacokinetic-pharmacodynamic targets in lung and cellular lesions throughout the dosing interval. IMPORTANCE Drug-resistant tuberculosis (TB) accounts for over 20% of all fatalities due to drug-resistant pathogens. With recently approved drugs and a promising drug candidate pipeline, the challenge faced by clinical developers is prioritization of drug combinations with the best potential to improve cure rates and shorten treatment duration. To this end, one must understand the contribution of each partner drug against different bacterial populations in pulmonary TB lesions. SQ109 is a safe drug candidate in clinical development for the treatment of multidrug resistant TB. It is active against replicating and non-replicating Mycobacterium tuberculosis persisters in vitro, in mouse models and in patients. SQ109 exhibits extremely low frequency of resistance, unprecedented among all TB drugs so far. Here we characterize the pharmacokinetics and activity of SQ109 at the site of TB disease to inform the selection of drug regimens that account for its lesion-centric pharmacokinetic-pharmacodynamic parameters and best leverage its contribution to efficient disease cure.

Mycobacterial membrane protein large 3 (Mmpl3) as a trehalose monomycolate lipid transporter contributes to cell wall biosynthesis. Inhibition of Mmpl3 can suppress cell growth and lead to mycobacterial death. SQ109 is a hydrophobic inhibitor of Mmpl3. We have devised a detergent-free strategy to characterize the SQ109/Mmpl3 interaction using the Native Cell Membrane Nanoparticles (NCMN) system, a new method for extracting membrane proteins that better retains native lipids. The homogeneity of the Mmpl3 NCMN particles was confirmed with electron microscopy. The hydrophobic protein-ligand interaction analysis shown for Mmpl3 using the NCMN system may broadly apply to other membrane proteins.

Tuberculosis (TB) remains a serious threat to whole human health. In particular, the drug resistance of Mycobacterium tuberculosis (Mtb) has become a huge challenge in clinical medicine, and it is extremely urgent to develop effective inhibitors with novel structures and mechanisms. Belonging to the Resistance, Nodulation and Division (RND) superfamily, Mycobacterial membrane proteins Large 3 (MmpL3) is mainly responsible for transporting mycolic acid outside cell membrane to form cell wall, and plays critical roles in iron acquisition which is vital to the survival of Mtb. As a potential Mtb target in recent years, its inhibitor research has attracted wide attention. A series of inhibitors (such as SQ109, AU1235, BM212, etc.) through experimental screening have been reported in succession, especially SQ109 has entered the clinical stage. In this paper, the structural biology information of target MmpL3 was summarized, and the structure-activity relationship (SAR) of inhibitors reported in recent years and their inhibitory mechanism both were reviewed, aiming to provide help for the rational design of MmpL3 inhibitors in the future.

Mycobacterium tuberculosis, the causative agent of tuberculosis disease, remains a public health crisis on a global scale, and development of new interventions and identification of drug resistance are pillars in the World Health Organization End TB Strategy. Leveraging the tractability of the TM4 mycobacteriophage and the sensitivity of the nanoluciferase reporter enzyme, the present work describes an evolution of phage-mediated detection and drug susceptibility testing of M. tuberculosis, adding a valuable tool in drug discovery and basic biology research. With additional validation, this system may play a role as a quantitative phenotypic reference method and complement to genotypic methods for diagnosis and antibiotic susceptibility testing., Phenotypic testing for drug susceptibility of Mycobacterium tuberculosis is critical to basic research and managing the evolving problem of antimicrobial resistance in tuberculosis management, but it remains a specialized technique to which access is severely limited. Here, we report on the development and validation of an improved phage-mediated detection system for M. tuberculosis. We incorporated a nanoluciferase (Nluc) reporter gene cassette into the TM4 mycobacteriophage genome to create phage TM4-nluc. We assessed the performance of this reporter phage in the context of cellular limit of detection and drug susceptibility testing using multiple biosafety level 2 drug-sensitive and -resistant auxotrophs as well as virulent M. tuberculosis strains. For both limit of detection and drug susceptibility testing, we developed a standardized method consisting of a 96-hour cell preculture followed by a 72-hour experimental window for M. tuberculosis detection with or without antibiotic exposure. The cellular limit of detection of M. tuberculosis in a 96-well plate batch culture was ≤102 CFU. Consistent with other phenotypic methods for drug susceptibility testing, we found TM4-nluc to be compatible with antibiotics representing multiple classes and mechanisms of action, including inhibition of core central dogma functions, cell wall homeostasis, metabolic inhibitors, compounds currently in clinical trials (SQ109 and Q203), and susceptibility testing for bedaquiline, pretomanid, and linezolid (components of the BPaL regimen for the treatment of multi- and extensively drug-resistant tuberculosis). Using the same method, we accurately identified rifampin-resistant and multidrug-resistant M. tuberculosis strains. IMPORTANCE Mycobacterium tuberculosis, the causative agent of tuberculosis disease, remains a public health crisis on a global scale, and development of new interventions and identification of drug resistance are pillars in the World Health Organization End TB Strategy. Leveraging the tractability of the TM4 mycobacteriophage and the sensitivity of the nanoluciferase reporter enzyme, the present work describes an evolution of phage-mediated detection and drug susceptibility testing of M. tuberculosis, adding a valuable tool in drug discovery and basic biology research. With additional validation, this system may play a role as a quantitative phenotypic reference method and complement to genotypic methods for diagnosis and antibiotic susceptibility testing.

New chemical matter is needed to target the divergent biology associated with the different life cycle stages ofPlasmodium. Here, we report the parallel screening of the Medicines for Malaria Venture Pandemic Response Box to identify multistage-active and stage-specific compounds against various life cycle stages ofPlasmodiumparasites (asexual parasites, stage IV/V gametocytes, gametes, oocysts and liver stages) and for endectocidal activity. Hits displayed unique chemotypes and included two multistage-active compounds, 16 asexual-targeted, six with prophylactic potential and ten gametocyte-targeted compounds. Notably, four structurally diverse gametocyte-targeted compounds with potent transmission-blocking activity were identified: the JmjC inhibitor ML324, two azole antifungals including eberconazole, and the antitubercular clinical candidate SQ109. Besides ML324, none of these have previously attributed antiplasmodial activity, emphasizing the success ofde novoparallel screening against differentPlasmodiumstages to deliver leads with novel modes-of-action. Importantly, the discovery of such transmission-blocking targeted compounds covers a previously unexplored base for delivery of compounds required for malaria elimination strategies.

The objective of the study: to assess efficiency and safety of SQ109 used within standard treatment regimens for multiple drug resistant tuberculosis (MDR TB) Subjects and Methods A multi-center, double, blind, randomized, placebo-controlled study was conducted in two parallel groups from September 21, 2012 to September 30, 2016, in 6 research centers located in 5 cities of the Russian Federation Main results 1 Cessation of bacillary excretion confirmed by cultures on liquid media by the end of the 6th month of the intensive phase of chemotherapy in pulmonary MDR TB patients receiving SQ109 was observed confidently more often versus treatment regimens containing only existing anti-tuberculosis drugs: both for ITT population (610% versus 429%, p = 00412), and PP population (797% versus 614%, p = 00486) 2 There were no statistically significant differences in the achievement of sputum conversion between the groups, but by the end of the 8th week, the sputum converted in 52% of patients in the group treated with SQ109 versus 38% in the group taking a placebo The median time of bacillary excretion cessation confirmed by culture on liquid media in SQ109 group made 56 days, while in the placebo group it was 84 days 3 Use of SQ109 along with basic chemotherapy for pulmonary MDR TB did not result in the higher frequency of adverse events, worsening of their severity, development of new variants of adverse events compared to the basic anti-tuberculosis treatment of this group of patients in combination with placebo 4 Results of the study allow concluding that SQ109 is an effective drug, satisfactory tolerated (compatible with tolerability of placebo) being a part of integral etiotropic chemotherapy of pulmonary MDR TB patients

Made available in DSpace on 2020-12-12T02:32:59Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-05-14 A series of N-phenyl-2,5-dimethylpyrrole derivatives, designed as hybrids of the antitubercular agents BM212 and SQ109, have been synthesized and evaluated against susceptible and drug-resistant mycobacteria strains. Compound 5d, bearing a cyclohexylmethylene side chain, showed high potency against M. tuberculosis including MDR-TB strains at submicromolar concentrations. The new compound shows bacteriostatic activity and low toxicity and proved to be effective against intracellular mycobacteria too, showing an activity profile similar to isoniazid. School of Cancer and Pharmaceutical Sciences King's College London, 150 Stamford Street Dipartimento di Biotecnologie Chimica e Farmacia, via A. Moro 2 Tuberculosis Research Laboratory School of Pharmaceutical Sciences Sao Paulo State University (UNESP), Rod. Araraquara-Jau, km1 Centre for Clinical Microbiology University College London Mycobacteria Research Laboratory Department of Biological Sciences Institute of Structural and Molecular Biology Birkbeck University of London, Malet Street Department of Chemistry Faculty of Exact Sciences Bar-Ilan University Tuberculosis Research Laboratory School of Pharmaceutical Sciences Sao Paulo State University (UNESP), Rod. Araraquara-Jau, km1

Tuberculosis is very much rampant in our society and accounts for a large number of deaths annually. In spite of consistent efforts being made, the disease has not been curtailed yet. The emergence of MDR and XDR strains in the society along with an increase in the number of HIV cases and that of latent TB, have further aggravated the problem making the disease very much persistent. The current situation clearly manifests the need to discover and develop new potent molecules/approaches that could help to tackle drug resistance. Various molecules, such as derivatives of fluoroquinolones (e.g. gatifloxacin, moxifloxacin and DC-159a), rifamycins (rifapentine), oxazolidinones (linezolid, sutezolid/PNU-100480), diarylquinolines (TMC207/bedaquiline), antifungal azoles, pyrrole (LL3858), nitroimidazopyran (PA824), nitroimidazole (OPC67683, TBA-354), diamine (SQ109) and benzothiazinone (BTZ043) are being developed in an attempt to combat the disease. This review presents a general introduction to the current status of the disease, the biology of the pathogen as well as the state of drug development against tuberculosis (TB) with emphasis on the major problems and bottlenecks associated with the same. Starting from the first drug against TB, the review discusses the entire history and the course of development of the drugs which are available today in the market as well as those which are under various phases of clinical and pre-clinical trials along with their mechanism of action. It also talks about the possible role of nanosciences in combating TB.

Author(s): Clemens, Daniel L; Lee, Bai-Yu; Silva, Aleidy; Dillon, Barbara Jane; Maslesa-Galic, Sasa; Nava, Susana; Ding, Xianting; Ho, Chih-Ming; Horwitz, Marcus A | Abstract: BackgroundShorter, more effective treatments for tuberculosis (TB) are urgently needed. While many TB drugs are available, identification of the best regimens is challenging because of the large number of possible drug-dose combinations. We have found consistently that responses of cells or whole animals to drug-dose stimulations fit a parabolic response surface (PRS), allowing us to identify and optimize the best drug combinations by testing only a small fraction of the total search space. Previously, we used PRS methodology to identify three regimens (PRS Regimens I-III) that in murine models are much more effective than the standard regimen used to treat TB. However, PRS Regimens I and II are unsuitable for treating drug-resistant TB and PRS Regimen III includes an experimental drug. Here, we use PRS methodology to identify from an expanded pool of drugs new highly effective near-universal drug regimens comprising only approved drugs.Methods and findingsWe evaluated combinations of 15 different drugs in a human macrophage TB model and identified the most promising 4-drug combinations. We then tested 14 of these combinations in Mycobacterium tuberculosis-infected BALB/c mice and chose for PRS dose optimization and further study the two most potent regimens, designated PRS Regimens IV and V, consisting of clofazimine (CFZ), bedaquiline (BDQ), pyrazinamide (PZA), and either amoxicillin/clavulanate (AC) or delamanid (DLM), respectively. We then evaluated the efficacy in mice of optimized PRS Regimens IV and V, as well as a 3-drug regimen, PRS Regimen VI (CFZ, BDQ, and PZA), and compared their efficacy to PRS Regimen III (CFZ, BDQ, PZA, and SQ109), previously shown to reduce the time to achieve relapse-free cure in mice by 80% compared with the Standard Regimen (isoniazid, rifampicin, PZA, and ethambutol). Efficacy measurements included early bactericidal activity, time to lung sterilization, and time to relapse-free cure. PRS Regimens III-VI all rapidly sterilized the lungs and achieved relapse-free cure in 3 weeks (PRS Regimens III, V, and VI) or 5 weeks (PRS Regimen IV). In contrast, mice treated with the Standard Regimen still had high numbers of bacteria in their lungs after 6-weeks treatment and none achieved relapse-free cure in this time-period.ConclusionsWe have identified three new regimens that rapidly sterilize the lungs of mice and dramatically shorten the time required to achieve relapse-free cure. All mouse drug doses in these regimens extrapolate to doses that are readily achievable in humans. Because PRS Regimens IV and V contain only one first line drug (PZA) and exclude fluoroquinolones and aminoglycosides, they should be effective against most TB cases that are multidrug resistant (MDR-TB) and many that are extensively drug-resistant (XDR-TB). Hence, these regimens have potential to shorten dramatically the time required for treatment of both drug-sensitive and drug-resistant TB. If clinical trials confirm that these regimens dramatically shorten the time required to achieve relapse-free cure in humans, then this radically shortened treatment has the potential to improve treatment compliance, decrease the emergence of drug resistance, and decrease the healthcare burden of treating both drug-sensitive and drug-resistant TB.

Tuberculosis, caused by the intracellular pathogen Mycobacterium tuberculosis , is a deadly disease that requires a long course of treatment. The emergence of drug-resistant strains has driven efforts to discover new small molecules that can kill the bacterium. Here, we report characterizations of the compound HC2091, which kills M. tuberculosis in a time- and dose-dependent manner in vitro and inhibits M. tuberculosis growth in macrophages. Whole-genome sequencing of spontaneous HC2091-resistant mutants identified single-nucleotide variants in the mmpL3 mycolic acid transporter gene. HC2091-resistant mutants do not exhibit cross-resistance with the well-characterized Mycobacterium membrane protein large 3 (MmpL3) inhibitor SQ109, suggesting a distinct mechanism of interaction with MmpL3. Additionally, HC2091 does not modulate bacterial membrane potential or kill nonreplicating M. tuberculosis , thus acting differently from other known MmpL3 inhibitors. RNA sequencing (RNA-seq) transcriptional profiling and lipid profiling of M. tuberculosis treated with HC2091 or SQ109 show that the two compounds target a similar pathway. HC2091 has a chemical structure dissimilar to those of previously described MmpL3 inhibitors, supporting the notion that HC2091 is a new class of MmpL3 inhibitor.

We synthesized a library of 48 analogs of the Mycobacterium tuberculosis cell growth inhibitor SQ109 in which the ethylene diamine linker was replaced by oxa-, thia- or heterocyclic species, and in some cases, the adamantyl group was replaced by a 1,2-carborane or the N-geranyl group by another hydrophobic species. Compounds were tested against Mycobacterium tuberculosis (H37Rv and/or Erdman), Mycobacterium smegmatis, Bacillus subtilis, Escherichia coli, Saccharomyces cerevisiae, Trypanosoma brucei and two human cell lines (human embryonic kidney, HEK293T, and the hepatocellular carcinoma, HepG2). Most potent activity was found against T. brucei, the causative agent of human African trypanosomiasis, and involved targeting of the mitochondrial membrane potential with 15 SQ109 analogs being more active than was SQ109 in cell growth inhibition, having IC50 values as low as 12 nM (5.5 ng/mL) and a selectivity index of ~300.

Objectives SQ109, an asymmetrical diamine, is a novel anti-TB drug candidate. This first study in patients was done to determine safety, tolerability, pharmacokinetics and bacteriological effect of different doses of SQ109 alone and in combination with rifampicin when administered over 14 days. Patients and methods Smear-positive pulmonary TB patients were randomized into six groups of 15 to receive once-daily oral treatment with 75, 150 or 300 mg of SQ109, rifampicin (10 mg/kg body weight), rifampicin plus 150 mg of SQ109, or rifampicin plus 300 mg of SQ109 for 14 days. Patients were hospitalized for supervised treatment, regular clinical, biochemical and electrocardiographic safety assessments, pharmacokinetic profiling and daily overnight sputum collection. Results SQ109 was safe and generally well tolerated. Mild to moderate dose-dependent gastrointestinal complaints were the most frequent adverse events. No relevant QT prolongation was noted. Maximum SQ109 plasma concentrations were lower than MICs. Exposure to SQ109 (AUC0–24) increased by drug accumulation upon repeated administration in the SQ109 monotherapy groups. Co-administration of SQ109 150 mg with rifampicin resulted in decreasing SQ109 exposures from day 1 to day 14. A higher (300 mg) dose of SQ109 largely outweighed the evolving inductive effect of rifampicin. The daily fall in log cfu/mL of sputum (95% CI) was 0.093 (0.126–0.059) with rifampicin, 0.133 (0.166–0.100) with rifampicin plus 150 mg of SQ109 and 0.089 (0.121–0.057) with rifampicin plus 300 mg of SQ109. Treatments with SQ109 alone showed no significant activity. Conclusions SQ109 alone or with rifampicin was safe over 14 days. Upon co-administration with rifampicin, 300 mg of SQ109 yielded a higher exposure than the 150 mg dose. SQ109 did not appear to be active alone or to enhance the activity of rifampicin during the 14 days of treatment.

We report the discovery of a series of new drug leads that have potent activity against Mycobacterium tuberculosis as well as against other bacteria, fungi, and a malaria parasite. The compounds are analogues of the new tuberculosis (TB) drug SQ109 (1), which has been reported to act by inhibiting a transporter called MmpL3, involved in cell wall biosynthesis. We show that 1 and the new compounds also target enzymes involved in menaquinone biosynthesis and electron transport, inhibiting respiration and ATP biosynthesis, and are uncouplers, collapsing the pH gradient and membrane potential used to power transporters. The result of such multitarget inhibition is potent inhibition of TB cell growth, as well as very low rates of spontaneous drug resistance. Several targets are absent in humans but are present in other bacteria, as well as in malaria parasites, whose growth is also inhibited.

Tuberculosis is a major global health problem. In the middle of the last century several laboratories identified, developed and synthesized several substances which were active against Mycobacterium tuberculosis, the causative agent of the disease. In the 1980s the standard oral treatment regimen was introduced with isoniazid, rifampicin, pyrazinamide, and ethambutol. In combination with the DOTS strategy it was possible treat TB within 6–8 months. But with the emergence of drug resistant strains, the formerly successful regiment became ineffective for MDR and XDR TB patients. Even more alarming, the rapidly increasing HIV epidemic also increases the number of HIV-related TB. Facing these facts, it became evident that novel strategies and antibiotics were needed to treat the new forms of TB. But over the last 60 years no novel TB drug was developed or even in the drug pipeline. But during the last ten years several novel substances have been developed to combat the deadly disease. For the first time in decades the TB drug pipeline is filled again with several promising compounds and many of them have reached Phase II and Phase III clinical trials. Several laboratories and companies all over the world currently are developing and evaluating these substances. This review presents novel substances, which were for the first time exclusively developed for TB such as bedaquilines, nitroimidazoles and the diamine SQ109. We also summarize the present knowledge about enzymes and biosynthesis pathways which offer potential targets for drug discovery against M. tuberculosis.

Item does not contain fulltext Current treatment for tuberculosis (TB) is complicated by the emergence of multidrug resistant TB (MDR-TB). As a result, there is an urgent need for new powerful anti-TB regimens and novel strategies. In this study, we aimed to potentiate a moxifloxacin + linezolid backbone as treatment for MDR-TB with the efflux pump inhibitors verapamil and timcodar as well as with drugs that act on mycobacterial cell wall stability such as colistin and SQ109. Using a time-kill kinetics assay, the activities of moxifloxacin, linezolid, verapamil, timcodar, colistin and SQ109 as single drugs against Mycobacterium tuberculosis were evaluated. In addition, the activity of the moxifloxacin + linezolid backbone in combination with one of the potentiator drugs was assessed. As little as 0.125 mg/L moxifloxacin achieved 99% killing of M. tuberculosis after 6 days of exposure. Linezolid showed moderate killing but 99% killing was not achieved. Verapamil, timcodar and colistin only resulted in killing with the highest concentrations tested but 99% killing was not achieved. SQ109 resulted in complete elimination after 1 day of exposure to 256 mg/L and in 99% elimination after 6 days of exposure to 1 mg/L. Furthermore, colistin added to the moxifloxacin + linezolid backbone resulted in increased elimination, whereas verapamil, timcodar and SQ109 showed no added value to the backbone. This finding that colistin potentiates the activity of the moxifloxacin + linezolid backbone against M. tuberculosis suggests its potential role in further studies on the applicability of a moxifloxacin + linezolid treatment of MDR-TB.

New treatments for tuberculosis infection are critical to combat the emergence of multi-drug and extensively-drug resistant Mycobacterium tuberculosis (Mtb). We report the characterization of a diphenylether modified adamantyl 1,2-diamine that we refer to as TBL-140, which has a minimal inhibitory concentration (MIC(99)) of 1.2 μg/mL. TBL-140 is effective against drug-resistant Mtb and non-replicating bacteria. In addition, TBL-140 eliminates expansion of Mtb in cell culture infection assays at its MIC. To define the mechanism of action of this compound, we performed a spontaneous mutant screen and biochemical assays. We determined that TBL-140 treatment impacts the proton motive force (PMF) by perturbing the transmembrane potential (ΔΨ), consistent with a target in the electron transport chain (ETC). As a result, treated bacteria have reduced intracellular ATP levels. We show that TBL-140 exhibits greater metabolic stability than SQ109, a structurally similar compound in clinical trials for treatment of MDR-TB infections. Combined, these results suggest that TBL-140 should be investigated further to assess its potential as an improved therapeutic lead against Mtb.

The objective of this review is to report evidence about the efficacy and potential of currently licensed drugs and new molecules beyond pre-clinical development for improving the chemotherapy of tuberculosis (TB). Rifapentine, a rifamycin with low minimum inhibitory concentration, long half-life and potent sterilizing activity in mice did not confirm its potential in a recent short-term clinical trial and is being extensively re-evaluated. Moxifloxacin, a fluoroquinolone, improved the activity of the standard drug regimen when substituted for ethambutol (EMB). It is being studied to shorten the duration of treatment for fully drug-susceptible TB (Remox study). Clofazimine, a fat-soluble dye with experimental activity against TB, but used only for leprosy in the last 50 years, requires further study because it has been included in a successful short 9-month combined drug regimen for the treatment of multidrug-resistant TB. The diarylquinoline TMC207 is the most promising among the new TB drugs because of its experimental and clinical rate of culture conversion. Also exciting, 200 mg daily doses in humans of the nitroimidazo-oxazine PA-824 and the nitro-dihydro-imidazooxazole OPC-67683 were safe and induced a bactericidal effect of respectively 0.098 ± 0.072 log(10) and 0.040 ± 0.056 log(10) per day. The new oxazolidinones PNU-100480 and AZD-5847 might be at least as active as linezolid and much less toxic. SQ109 is an EMB analogue that does not have cross-resistance with EMB and might have synergistic activity in combined regimens. Benzothiazinones and dinitrobenzamides show exciting in vitro anti-microbial activity and deserve careful attention.

The increasing drug resistance of Mycobacterium tuberculosis to the currently used drugs and HIV coinfection has caused alarm in the international scientific community. Subsequently, there is an urgent need for the development of new drug molecules with newer targets and with an alternative mechanism of action. Since the last 50 years, the same long-duration, multidrug treatment plan is being followed for the treatment of tuberculosis. The objective of this review article is to critically analyze the antitubercular potential of various classes of compounds (quinoline, diamine, quinolone, fluoroquinolone, quinone, nitroimidazole, terpenoid, isonicotinyl, oxazolidinone, pyrimidine, and purine), their possibility to be a future drug candidate, and latest information on the clinical status of some novel antitubercular compounds. Compounds such as moxifloxacin, PA824, and TMC207 are well tolerated and there is no adverse effect shown by them. Moxifloxacin and gatifloxacin shows cross-resistance to the currently used drugs while no cross-resistance observed in case of TMC207 and PA824. Some compounds like OPC67683 and PA824 are bactericidal in nature.

New chemotherapeutics active against multidrug-resistant Mycobacterium tuberculosis are urgently needed. We report on the identification of an adamantyl urea compound that shows potent bactericidal activity against M. tuberculosis and a unique mode of action, namely the abolition of the translocation of mycolic acids from the cytoplasm, where they are synthesized to the periplasmic side of the plasma membrane and are in turn transferred onto cell wall arabinogalactan or used in the formation of virulence-associated, outer membrane, trehalose-containing glycolipids. Whole-genome sequencing of spontaneous-resistant mutants of M. tuberculosis selected in vitro followed by genetic validation experiments revealed that our prototype inhibitor targets the inner membrane transporter MmpL3. Conditional gene expression of mmpL3 in mycobacteria and analysis of inhibitor-treated cells validate MmpL3 as essential for mycobacterial growth and support the involvement of this transporter in the translocation of trehalose monomycolate across the plasma membrane.

Tuberculosis (TB) remains one of the leading public health problems worldwide. Declared as a global emergency in 1993 by the WHO, its control is hampered by the emergence of multidrug resistance (MDR), defined as resistance to at least rifampicin and isoniazid, two key drugs in the treatment of the disease. More recently, severe forms of drug resistance such as extensively drug-resistant (XDR) TB have been described. After the discovery of several drugs with anti-TB activity, multidrug therapy became fundamental for control of the disease. Major advances in molecular biology and the availability of new information generated after sequencing the genome of Mycobacterium tuberculosis increased our knowledge of the mechanisms of resistance to the main anti-TB drugs. Better knowledge of the mechanisms of drug resistance in TB and the molecular mechanisms involved will help us to improve current techniques for rapid detection and will also stimulate the exploration of new targets for drug activity and drug development. This article presents an updated review of the mechanisms and molecular basis of drug resistance in M. tuberculosis. It also comments on the several gaps in our current knowledge of the molecular mechanisms of drug resistance to the main classical and new anti-TB drugs and briefly discusses some implications of the development of drug resistance and fitness, transmission and pathogenicity of M. tuberculosis.

Tuberculosis is a serious global health threat for which new treatments are urgently needed. This study examined the safety, tolerability, pharmacokinetics, and pharmacodynamics of multiple ascending doses of the oxazolidinone PNU-100480 in healthy volunteers, using biomarkers for safety and efficacy. Subjects were randomly assigned to PNU-100480 or placebo (4:1) at schedules of 100, 300, or 600 mg twice daily or 1,200 mg daily for 14 days or a schedule of 600 mg twice daily for 28 days to which pyrazinamide was added on days 27 and 28. A sixth cohort was given linezolid at 300 mg daily for 4 days. Signs, symptoms, and routine safety tests were monitored. Bactericidal activity against Mycobacterium tuberculosis was measured in ex vivo whole-blood culture. Plasma drug and metabolite concentrations were compared to the levels required for inhibition of M. tuberculosis growth and 50% inhibition of mitochondrial protein synthesis. All doses were safe and well tolerated. There were no hematologic or other safety signals during 28 days of dosing at 600 mg twice daily. Plasma concentrations of PNU-100480 and metabolites at this dose remained below those required for 50% inhibition of mitochondrial protein synthesis. Cumulative whole-blood bactericidal activity of PNU-100480 at this dose (−0.316 ± 0.04 log) was superior to the activities of all other doses tested ( P < 0.001) and was significantly augmented by pyrazinamide (−0.420 ± 0.06 log) ( P = 0.002). In conclusion, PNU-100480 was safe and well tolerated at all tested doses. Further studies in patients with tuberculosis are warranted. Biomarkers can accelerate early development of new tuberculosis treatments.

Despite intensive efforts to discover highly effective treatments to eradicate tuberculosis (TB), it remains as a major threat to global human health. For this reason, new TB drugs directed toward new targets are highly coveted. MmpLs (Mycobacterial membrane proteins Large), which play crucial roles in transporting lipids, polymers and immunomodulators and which also extrude therapeutic drugs, are among the most important therapeutic drug targets to emerge in recent times. Here, crystal structures of mycobacterial MmpL3 alone and in complex with four TB drug candidates, including SQ109 (in Phase 2b-3 clinical trials), are reported. MmpL3 consists of a periplasmic pore domain and a twelve-helix transmembrane domain. Two Asp-Tyr pairs centrally located in this domain appear to be key facilitators of proton-translocation. SQ109, AU1235, ICA38, and rimonabant bind inside the transmembrane region and disrupt these Asp-Tyr pairs. This structural data will greatly advance the development of MmpL3 inhibitors as new TB drugs.

As current treatment of tuberculosis is burdensomely long, provoking non-adherence and drug resistance, effective short-course treatments are needed. Using the output-driven parabolic response surface (PRS) platform, we have identified drug regimens that treat tuberculosis more rapidly in mice than the current Standard Regimen used in humans. We show that PRS Regimen III, comprising clofazimine, SQ109, bedaquiline and pyrazinamide, rapidly sterilizes the lung both in conventionally studied BALB/c mice and in C3HeB/FeJ mice, highly susceptible mice that develop massive necrotic granulomatous lung lesions akin to those in humans, achieving relapse-free cure in only 4 weeks (p

The antimicrobial activity of five novel SQ109 derivatives including SQ109 against bacteria, yeast and filamentous fungi is reported herein. Using broth microdilution techniques, compounds 2 and 3 were found to be active against most tested fungi and bacteria, with minimum inhibitory concentrations (MICs) ranging from 0.98 to 31 μg ml−1, except for Klebsiella pneumonia where the MIC was 250 μg ml−1. SQ109 and derivative 4 did not show any significant activity against most of the organisms used. However, their reduced derivatives 1 and 5 showed promising activity with MICs between 0.49 and 62.5 μg ml−1 against most of the microorganisms used.

The increase in drug-resistant tuberculosis and the global pandemic of human immunodeficiency virus infection‐related tuberculosis threaten global tuberculosis control. There are needs for improved therapy in all aspects of tuberculosis treatment: treatment of latent infection, active drug-susceptible disease, and particularly, drug-resistant disease. Fortunately, at this time of great need, the field of tuberculosis drug development has reemerged after 130 years of inactivity. I review the specific needs for new treatment regimens, the pathways of tuberculosis drug development, and the agents that are currently in clinical development. There is renewed interest in the rifamycin class; studies in the mouse model suggest that higher doses of rifampin or rifapentine may markedly improve the treatment of drug-susceptible disease. Fluoroquinolones may allow shorter treatment durations for drug-susceptible disease, though initial phase 2B trials have shown inconsistent activity. Novel drugs, such as TMC207, OPC-67683, PA824, SQ109, and PNU-100480, may improve the treatment of drug-resistant and drug-susceptible tuberculosis.

As part of an ongoing effort to develop highly potent anti-tuberculosis agents, fourteen pentacyclo-undecane (PCU) tetra-amine compounds were synthesized and screened for their in vitro anti-mycobacterial activity against two TB strains, H37Rv and XDR 194 [an extensively drug-resistant strain of tuberculosis]. Using the broth macrodilution method, nitrofuranylamide based compounds (6a and 6b) showed almost similar activities against the H37Rv strain of Mycobacterium tuberculosis when compared with the control drug, ethambutol. N-Geranyl piperazine PCU (8a) and trans-trans farnesyl piperazine PCU (8b) were 3.2 and 3.7 times more potent than commercially available ethambutol. Both isoprenyl PCU tetra-amine derivatives and N-decyl piperazine PCU (9a) were highly active against the XDR 194 strain of tuberculosis with MICs in the range of 0.63-3.02 microM. Cytotoxicities (IC(50)) of isoprenyl based compounds (8a, 8b) and compound 9a were tested on a mammalian cell line [MDBK (Madin Darby bovine kidney epithelium)] with values of 30, 24 and 25 microM respectively.

PA-824 is a novel antibacterial agent that has shown in vitro activity against both drug-sensitive and drug-resistant Mycobacterium tuberculosis . The compound's MIC is between 0.015 and 0.25 μg/ml for drug-sensitive strains and between 0.03 and 0.53 μg/ml for drug-resistant strains. In addition, it is active against nonreplicating anaerobic Mycobacterium tuberculosis . The safety, tolerability, and pharmacokinetics of PA-824 were evaluated in two escalating-dose clinical studies, one a single-dose study and the other a multiple-dose study (up to 7 days of daily dosing). In 58 healthy subjects dosed with PA-824 in these studies, the drug candidate was well tolerated, with no significant or serious adverse events. In both studies, following oral administration PA-824 reached maximal plasma levels in 4 to 5 h independently of the dose. Maximal blood levels averaged approximately 3 μg/ml (1,500-mg dose) in the single-dose study and 3.8 μg/ml (600-mg dose) in the multiple-dose study. Steady state was achieved after 5 to 6 days of daily dosing, with an accumulation ratio of approximately 2. The elimination half-life averaged 16 to 20 h. Overall, PA-824 was well tolerated following oral doses once daily for up to 7 days, and pharmacokinetic parameters were consistent with a once-a-day regimen. The results of these studies, combined with the demonstrated activity of PA-824 against drug-sensitive and multidrug-resistant Mycobacterium tuberculosis , support the investigation of this novel compound for the treatment of tuberculosis.

Background The diarylquinoline TMC207 offers a new mechanism of antituberculosis action by inhibiting mycobacterial ATP synthase. TMC207 potently inhibits drug-sensitive and drug-resistant Mycobacterium tuberculosis in vitro and shows bactericidal activity in patients who have drug-susceptible pulmonary tuberculosis. Methods In the first stage of a two-stage, phase 2, randomized, controlled trial, we randomly assigned 47 patients who had newly diagnosed multidrug-resistant pulmonary tuberculosis to receive either TMC207 (400 mg daily for 2 weeks, followed by 200 mg three times a week for 6 weeks) (23 patients) or placebo (24 patients) in combination with a standard five-drug, second-line antituberculosis regimen. The primary efficacy end point was the conversion of sputum cultures, in liquid broth, from positive to negative. Results The addition of TMC207 to standard therapy for multidrug-resistant tuberculosis reduced the time to conversion to a negative sputum culture, as compared with placebo (hazard ratio, 11.8; 95% confidence interval, 2.3 to 61.3; P=0.003 by Cox regression analysis) and increased the proportion of patients with conversion of sputum culture (48% vs. 9%). The mean log10 count of colony-forming units in the sputum declined more rapidly in the TMC207 group than in the placebo group. No significant differences in average plasma TMC207 concentrations were noted between patients with and those without culture conversion. Most adverse events were mild to moderate, and only nausea occurred significantly more frequently among patients in the TMC207 group than among patients in the placebo group (26% vs. 4%, P=0.04). Conclusions The clinical activity of TMC207 validates ATP synthase as a viable target for the treatment of tuberculosis. (ClinicalTrials.gov number, NCT00449644 [ClinicalTrials.gov] .)

The bicyclic nitroimidazole PA-824 is a pro-drug with a very complex mechanism of action active against both replicating and hypoxic, non-replicating Mycobacterium tuberculosis. Microarray analysis of the mode of action of PA-824 showed a puzzling mixed effect both on genes responsive to both cell wall inhibition (like isoniazid) and respiratory poisoning (like cyanide). The aerobic killing mechanism of this drug appears to involve inhibition of cell wall mycolic acid biosynthesis through an as yet unknown molecular mechanism. However, the structure-activity relationships governing aerobic activity do not parallel the relationships determining anaerobic activity. Based on the metabolite profiling of PA-824 and various derivatives by Ddn-mediated activation, we have shown that PA-824 acts directly as an NO donor.1 This respiratory poisoning through nitric oxide release seemed to be a crucial element of anaerobic activity by PA-824. The effect of PA-824 on the respiratory complex under hypoxic non-replicating conditions was also manifested in a rapid drop in intracellular ATP levels, again similar to that observed by cyanide treatment. Thus, transcriptional profiling provided valuable clues to elucidating the molecular mechanism of mycobacterial killing.

Tuberculosis (TB) remains a global health problem today. The development of new TB drugs is in line with WHO's Stop TB Strategy. The Global TB Drug Alliance was formed in 2000 to enhance TB drug development. Current drug therapy for active TB, TB/HIV coinfections, multidrug-resistant TB and latent TB infection are far from satisfactory. New drugs with desirable characteristics are required. Ideally, drugs should be active against drug-sensitive and drug-resistant bacteria, and act on both dividing and nonreplicating persistent bacteria. More needs to be known about the biology of ‘persistent’ bacilli which may be important for development of drugs for shortening current treatment regimens and tackling the huge pool of latent infection. The TB drug development process has been very slow, and there are a number of hurdles in efficacy evaluation. Mathematical models have predicted that substantial benefits can be gained with the introduction of new, shorter treatment regimens. Nowadays, an increasing number of potential candidates are in the global TB drug development pipeline. Among these, seven relatively more important novel compounds are in various stages of clinical development, namely, gatifloxacin, moxifloxacin, TMC207, OPC-67683, PA-824, LL3858 and SQ109. In addition, there are other new compounds in the TB Alliance's portfolio in various stages of development, and many more in the projects of other workers worldwide. The stock-taking exercise by the Working Group on New Drugs has provided many examples of such work. With the flourishing interest in this field, it is hoped that a new drug may become available rather soon.

It is estimated that a third of the world's population is currently infected with tuberculosis, leading to 1.6 million deaths annually. The current drug regimen is 40 years old and takes 6-9 months to administer. In addition, the emergence of drug resistant strains and HIV co-infection mean that there is an urgent need for new anti-tuberculosis drugs. The twenty-first century has seen a revival in research and development activity in this area, with several new drug candidates entering clinical trials. This review considers new potential first-line anti-tuberculosis drug candidates, in particular those with novel mechanisms of action, as these are most likely to prove effective against resistant strains. A brief overview of current first-line and recent drugs (such as fluoroquinolones, rifampicin and isoniazid analogues) is initially presented. This is followed by a description of structure-activity relationships, in vitro and in vivo activity, pharmacokinetics, mechanism of action, combination regimens and clinical trials of the new drug candidates SQ109, PA-824, OPC-67683, TMC207 and others.

Tibotec Medicinal Compound 207 (TMC207) is a novel diarylquinoline with a unique mode of action that targets mycobacterial ATP synthase. TMC207 exhibits high in vitro activity against mycobacterial strains either susceptible or resistant to all first-line and many second-line drugs, including fluoroquinolones, and has shown exceptional in vivo activity against several mycobacterial species in different animal models. In this early bactericidal activity study, 75 treatment-naïve patients with smear-positive pulmonary tuberculosis were randomized to once-daily oral TMC207 (25 mg, 100 mg, or 400 mg), 600 mg rifampin (RIF), or 300 mg isoniazid (INH) for 7 days. Sixteen-hour overnight sputum collected at baseline and on each treatment day was plated in serial dilutions on selective agar plates. The bactericidal activity was expressed as the log 10 decrease in CFU/ml sputum/day. Pharmacokinetic sampling was performed on day 7 of TMC207 administration up to 24 h postdose. The decreases in log 10 CFU counts (± standard deviation) from baseline to day 7 were 0.04 ± 0.46 for 25 mg TMC207 ( n = 14), 0.26 ± 0.64 for 100 mg TMC207 ( n = 14), 0.77 ± 0.58 for 400 mg TMC207 ( n = 14), 1.88 ± 0.74 for INH ( n = 11), and 1.70 ± 0.71 for RIF ( n = 14). Significant bactericidal activity of 400 mg TMC207 was observed from day 4 onward and was similar in magnitude to those of INH and RIF over the same period. The pharmacokinetics of TMC207 were linear across the dose range. In summary, TMC207 demonstrated bactericidal activity with a delayed onset and was well tolerated, and no study drug-related serious adverse events occurred.

Tuberculosis (TB) is a serious health problem causing 1.5 million deaths worldwide. After the discovery of first-line anti-TB drugs, the mortality rate declined sharply, however, the emergence of drug-resistant strains and HIV co-infection have led to increased incidence of this disease. A number of new potential antitubercular drug candidates with novel modes of action have entered clinical trials in recent years. Compounds such as gatifloxacin, moxifloxacin and linezolid, the already known antibiotics are currently being evaluated for their anti-TB activity. OPC-67683 and TMC207 have been approved for the treatment of MDR-TB patients recently, while PA-824, SQ109, PNU-100480, AZD5847, LL3858, SQ609, SQ641, BTZ043, DC-159a, CPZEN-45, Q-203, DNB1, TBA-354 are in various phases of clinical and preclinical developments. This review evaluates the current status of TB drug development and future aspects.

Contains fulltext : 167529.pdf (Publisher’s version ) (Closed access) BACKGROUND: Multiple-drug therapy for tuberculosis (TB) and TB-associated co-morbidity increase the likelihood of drug-drug interactions (DDIs). Inhibition of membrane transporters is an important mechanism underlying DDIs. In this study, we assessed the in vitro inhibitory potential of currently used first and second-line TB drugs and of proposed mycobacterial efflux pump inhibitors (EPIs) on the major ABC transporters relevant to drug transport, namely P-gp, BCRP, BSEP and MRP1-5. METHODS: Membrane vesicles isolated from transporter-overexpressing HEK293 cells were used to study the inhibitory action of TB drugs and EPIs on the transport of model substrates [(3)H]-NMQ (P-gp); [(3)H]-E1S (BCRP); [(3)H]-TCA (BSEP); [(3)H]-E217betaG (MRP1, 3 and 4) and [(3)H]-MTX (MRP2 and 5). RESULTS: A strong inhibition (IC50 value

The creation of new chemotherapeutic regimens that permit shortening the duration of treatment is a major priority for antituberculosis drug development. In this study, we used the murine model of experimental tuberculosis therapy to determine whether incorporation of the investigational new nitroimidazopyran PA-824 into the standard first-line regimen has the potential to shorten the 6-month duration of treatment. As demonstrated previously, PA-824 alone had significant bactericidal activity over the first 2 months of treatment. Moreover, the substitution of PA-824 for isoniazid led to significantly lower lung CFU counts after 2 months of treatment and to more rapid culture-negative conversion compared to the standard regimen of rifampin, isoniazid, and pyrazinamide. Despite this, there was no difference in the proportion of mice relapsing after completing 6 months of therapy (2 of 19 mice treated with PA-824 in place of isoniazid relapsed versus 0 of 46 mice treated with the standard regimen). Meanwhile, no other PA-824-containing regimen tested was superior to the standard regimen on any assessment. Thus, we were unable to establish a clear role for PA-824 in a treatment-shortening regimen that includes two or more of the current first-line drugs. Future preclinical studies should include the evaluation of novel combinations of PA-824 with new drug candidates in addition to existing antituberculosis drugs for their potential to substantially improve the treatment of both drug-susceptible and multidrug-resistant tuberculosis.

Objectives: The purpose of this study was to determine interactions of SQ109, a new asymmetric diamine tuberculosis (TB) drug candidate, with existing antitubercular drugs in vitro and assess its potential to improve combination drug activities against Mycobacterium tuberculosis. Methods: Two-drug combinations at various concentrations below their MICs were tested for growth inhibition of M. tuberculosis using the BACTEC 460 system in vitro. Drug interactions were evaluated based on the quotient values that were derived numerically from the growth indices of cultures treated with a single antibiotic or combination treatment with two antibiotics. Results: SQ109at0.5 of its MIC demonstrated strong Synergistic activity with 0.5 MIC isoniazid and as low as 0.1 MIC rifampicin in inhibition of M. tuberculosis growth. Additive effects were observed between SQ109 and streptomycin, but neither synergy nor additive effects were observed with the combination of SQ109 with ethambutol or pyrazinamide. The synergy between SQ109 and rifampicin was also demonstrated using rifampicin-resistant (RIF R ) M. tuberculosis strains; SQ109 lowered the MIC of rifampicin for these drug-resistant strains. Conclusions: SQ109 interacts Synergistically with isoniazid and rifampicin, two of the most important front-line TB drugs. This finding supports efforts to further evaluate new combination therapies containing SQ109 in experimental animal models of TB that emulate future clinical trial studies in humans.

The present study was aimed at fingerprinting pharmacoproteomic alterations of the Mycobacterium tuberculosis H37Rv strain induced by antitubercular drugs isoniazid (INH), ethambutol (EMB), and SQ109 [N-geranyl-N'-(2-adamantyl)ethane-1,2-diamine, a novel 1,2-diamine-based EMB analog], providing new understanding of pharmacoproteomic mechanisms of each and exploring new drug targets. The three drugs produced significant down-regulation of 13 proteins, including immunogenic ModD, Mpt64, with proteins from the Pro-Glu family being inhibited the most. Alternatively, the three drugs up-regulated 17 proteins, including secreted antigenic proteins ESAT-6 and CFP-10. Among these, ESAT-6 and AphC were most affected by INH, whereas EMB had the greatest effect on ESAT-6. All three drugs produced only moderate up-regulation of aerobic and iron metabolism proteins, i.e., electron transfer flavoprotein Fix A and Fix B, and ferritin-like protein BfrB, suggesting that the interruption of microbacterial energy metabolism is not a primary mechanism of action. INH suppressed ATP-dependent DNA/RNA helicase, but up-regulated beta-ketoacyl-acyl carrier protein synthase. These effects may contribute to its bactericidal effects. In contrast, EMB and SQ109 did just the opposite: these drugs up-regulated the helicase and down-regulated the synthase. For most of the H37Rv proteins, similar pharmacoproteomic patterns were found for both EMB and SQ109. None of the drugs significantly regulated expression of chaperonins GroES, GroEL2, and Dnak, suggesting that these drugs do not affect chaperone-mediated nascent polypeptide folding and sorting. The present study identified proteins directly modulated by the actions of INH, EMB, and SQ109 and distinguished INH activity from the diamine antitubercular compounds that inhibit M. tuberculosis H37Rv.

The nitroimidazopyran PA-824 has potent in vitro activity against Mycobacterium tuberculosis , a narrow spectrum of activity limited primarily to the M. tuberculosis complex, and no demonstrable cross-resistance to a variety of antituberculosis drugs. In a series of experiments, we sequentially characterized the activity of PA-824 in an experimental murine model of tuberculosis. The minimal effective dose was 12.5 mg/kg of body weight/day. The minimal bactericidal dose (MBD) was 100 mg/kg/day. When PA-824 was used as monotherapy at the MBD, it exhibited promising bactericidal activity during the initial intensive phase of therapy that was similar to that of the equipotent dose of isoniazid in humans. In combination with isoniazid, PA-824 prevented the selection of isoniazid-resistant mutants. Perhaps more importantly, PA-824 also demonstrated potent activity during the continuation phase of therapy, during which it targeted bacilli that had persisted through an initial 2-month intensive phase of treatment with rifampin, isoniazid, and pyrazinamide. Together, these data strongly support further evaluation of PA-824 in combination with first- or second-line antituberculosis drugs to determine its potential contribution to the treatment of drug-susceptible or multidrug-resistant tuberculosis, respectively.

This study extends earlier reports regarding the in vitro and in vivo efficacies of the nitroimidazopyran PA-824 against Mycobacterium tuberculosis . PA-824 was tested in vitro against a broad panel of multidrug-resistant clinical isolates and was found to be highly active against all isolates (MIC < 1 μg/ml). The activity of PA-824 against M. tuberculosis was also assessed grown under conditions of oxygen depletion. PA-824 showed significant activity at 2, 10, and 50 μg/ml, similar to that of metronidazole, in a dose-dependent manner. In a short-course mouse infection model, the efficacy of PA-824 at 50, 100, and 300 mg/kg of body weight formulated in methylcellulose or cyclodextrin/lecithin after nine oral treatments was compared with those of isoniazid, rifampin, and moxifloxacin. PA-824 at 100 mg/kg in cyclodextrin/lecithin was as active as moxifloxacin at 100 mg/kg and isoniazid at 25 mg/kg and was slightly more active than rifampin at 20 mg/kg. Long-term treatment with PA-824 at 100 mg/kg in cyclodextrin/lecithin reduced the bacterial load below 500 CFU in the lungs and spleen. No significant differences in activity between PA-824 and the other single drug treatments tested (isoniazid at 25 mg/kg, rifampin at 10 mg/kg, gatifloxacin at 100 mg/kg, and moxifloxacin at 100 mg/kg) could be observed. In summary, its good activity in in vivo models, as well as its activity against multidrug-resistant M. tuberculosis and against M. tuberculosis isolates in a potentially latent state, makes PA-824 an attractive drug candidate for the therapy of tuberculosis. These data indicate that there is significant potential for effective oral delivery of PA-824 for the treatment of tuberculosis.

We tested the antituberculosis drug SQ109, which is currently in advanced clinical trials for the treatment of drug-susceptible and drug-resistant tuberculosis, for its in vitro activity against the trypanosomatid parasite Trypanosoma cruzi , the causative agent of Chagas disease. SQ109 was found to be a potent inhibitor of the trypomastigote form of the parasite, with a 50% inhibitory concentration (IC 50 ) for cell killing of 50 ± 8 nM, but it had little effect (50% effective concentration [EC 50 ], ∼80 μM) in a red blood cell hemolysis assay. It also inhibited extracellular epimastigotes (IC 50 , 4.6 ± 1 μM) and the clinically relevant intracellular amastigotes (IC 50 , ∼0.5 to 1 μM), with a selectivity index of ∼10 to 20. SQ109 caused major ultrastructural changes in all three life cycle forms, as observed by light microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). It rapidly collapsed the inner mitochondrial membrane potential (Δψ m ) in succinate-energized mitochondria, acting in the same manner as the uncoupler FCCP [carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone], and it caused the alkalinization of internal acidic compartments, effects that are likely to make major contributions to its mechanism of action. The compound also had activity against squalene synthase, binding to its active site; it inhibited sterol side-chain reduction and, in the amastigote assay, acted synergistically with the antifungal drug posaconazole, with a fractional inhibitory concentration index (FICI) of 0.48, but these effects are unlikely to account for the rapid effects seen on cell morphology and cell killing. SQ109 thus most likely acts, at least in part, by collapsing Δψ/ΔpH, one of the major mechanisms demonstrated previously for its action against Mycobacterium tuberculosis . Overall, the results suggest that SQ109, which is currently in advanced clinical trials for the treatment of drug-susceptible and drug-resistant tuberculosis, may also have potential as a drug lead against Chagas disease.

The authors present an overview about proteomics studies in Mycobacterium tuberculosis exposed to some anti-tuberculosis drugs and new candidates, using two-dimensional gel electrophoresis and mass spectrometry. To date, that the authors have knowledge, this is the first studies that was performed specifically in M. tuberculosis using systematic review on electronic literature conducted in three databases using the following search terms: tuberculosis OR mycobacterium tuberculosis, proteome OR proteomics, and mass spectrometry electrospray ionization OR matrix-assisted laser desorption ionization OR two-dimensional gel electrophoresis. By electronic search, 622 abstracts of the original articles published from November 2003 to March 2016 were selected. After the selection, four articles fulfill proposed criteria and were included in this study. The studies reported changes in the protein profile of M. tuberculosis after exposure to isoniazid, ethambutol, streptomycin, ofloxacin, moxifloxacin and two new drugs candidates, SQ109 and ATB107. In conclusion, the proteins changes were related to the synthesis of mycolic acids, cellular metabolism pathways, bacterial stress and starvation.

The United Nations Millennium Development Goal of reversing the global spread of tuberculosis by 2015 has been offset by the rampant re-emergence of drug-resistant tuberculosis, in particular fluoroquinolone-resistant multidrug-resistant and extensively drug-resistant tuberculosis. After decades of quiescence in the development of antituberculosis medications, bedaquiline and delamanid have been conditionally approved for the treatment of drug-resistant tuberculosis, while several other novel compounds (AZD5847, PA-824, SQ109 and sutezolid) have been evaluated in phase II clinical trials. Before novel drugs can find their place in the battle against drug-resistant tuberculosis, linezolid has been compassionately used with success in the treatment of fluoroquinolone-resistant multidrug-resistant tuberculosis. This review largely discusses six novel drugs that have been evaluated in phase II and III clinical trials, with focus on the clinical evidence for efficacy and safety, potential drug interactions, and prospect for using multiple novel drugs in new regimens.

The first cases of totally drug-resistant (TDR) tuberculosis (TB) were reported in Italy 10 years ago; more recently, cases have also been reported in Iran, India and South Africa. Although there is no consensus on terminology, it is most commonly described as 'resistance to all first- and second-line drugs used to treat TB'. Mycobacterium tuberculosis (M.tb) acquires drug resistance mutations in a sequential fashion under suboptimal drug pressure due to monotherapy, inadequate dosing, treatment interruptions and drug interactions. The treatment of TDR-TB includes antibiotics with disputed or minimal effectiveness against M.tb, and the fatality rate is high. Comorbidities such as diabetes and infection with human immunodeficiency virus further impact on TB treatment options and survival rates. Several new drug candidates with novel modes of action are under late-stage clinical evaluation (e.g., delamanid, bedaquiline, SQ109 and sutezolid). 'Repurposed' antibiotics have also recently been included in the treatment of extensively drug resistant TB. However, because of mutations in M.tb, drugs will not provide a cure for TB in the long term. Adjunct TB therapies, including therapeutic vaccines, vitamin supplementation and/or repurposing of drugs targeting biologically and clinically relevant molecular pathways, may achieve better clinical outcomes in combination with standard chemotherapy. Here, we review broader perspectives of drug resistance in TB and potential adjunct treatment options.

A “golden age” of tuberculosis (TB) chemotherapy was heralded by the discovery of streptomycin in 1944. The chemotherapeutic regimen consists of an initial 2-month phase of treatment with isoniazid (INH), rifampin (RIF), pyrazinamide (PZA), and ethambutol (EMB), followed by a continuation phase of treatment lasting four months with INH and RIF. Important considerations for new agents include enhancement of penetration of infection sites, such as lung cavities, and long biological half-lives; achieving either might represent a significant advance toward shortening therapy and lead to simpler treatment regimens with improved patient compliance. The products of the emb locus of Mycobacterium avium were identified as the targets for EMB using a strategy of target overexpression. The locus contains three genes, embR, embA, and embB; the former encodes a putative regulator of embA and embB and is expendable for the resistant phenotype, which is copy number dependent. Pharmacoproteomic studies with M. tuberculosis H37Rv revealed that similar protein profiles were catalogued after both EMB and SQ109 treatments. A spontaneous mutant of Mycobacterium smegmatis designated mc2651 is resistant to INH, but retains wild-type KatG activity. Analyses of treated sensitive bacteria using electron microscopy revealed dysfunction in cell wall biosynthesis and incomplete septation. The increased abundance of CmaA2, involved in mycolic acid biosynthesis under anaerobic conditions suggests a level of metabolic activity related to mycolic acid biosynthesis under conditions usually associated with a transition to dormancy that may be linked, resulting in modulation of mycolic acid chain length during a dormant or persistent anaerobic state.

Purpose of review Recent advances in the development of new drugs and regimens provide hope that well tolerated, effective, and shorter-duration treatments for tuberculosis (TB) will become available. This review covers the recent trials of new TB drugs and regimens. Recent findings Moxifloxacin and levofloxacin have equally good efficacy and safety in the early phase of treatment of multidrug-resistant TB (MDR-TB), and linezolid has the potential to cure refractory cases of MDR-TB. Bedaquiline and delamanid may be the best drug candidates for enhancing treatment options for MDR-TB. New chemicals, such as sutezolid, AZD5847, PA-824, SQ109, and BTZ043, show potent activity against Mycobacterium tuberculosis. Late-generation fluoroquinolones in combination with the first-line and second-line anti-TB drugs have been used to shorten the treatment duration in drug-susceptible and MDR-TB. Summary New drugs and new combination regimens in clinical trials are expected to increase therapeutic efficacy and shorten treatment duration in both drug-susceptible and drug-resistant TB.

Mycobacterium tuberculosis, which causes tuberculosis, is the greatest single infectious cause of mortality worldwide, killing roughly two million people annually. Estimates indicate that one-third of the world population is infected with latent M. tuberculosis. The synergy between tuberculosis and the AIDS epidemic, and the surge of multidrug-resistant clinical isolates of M. tuberculosis have reaffirmed tuberculosis as a primary public health threat. However, new antitubercular drugs with new mechanisms of action have not been developed in over thirty years. Here we report a series of compounds containing a nitroimidazopyran nucleus that possess antitubercular activity. After activation by a mechanism dependent on M. tuberculosis F420 cofactor, nitroimidazopyrans inhibited the synthesis of protein and cell wall lipid. In contrast to current antitubercular drugs, nitroimidazopyrans exhibited bactericidal activity against both replicating and static M. tuberculosis. Lead compound PA-824 showed potent bactericidal activity against multidrugresistant M. tuberculosis and promising oral activity in animal infection models. We conclude that nitroimidazopyrans offer the practical qualities of a small molecule with the potential for the treatment of tuberculosis.

The low bioavailability of SQ109 in rats, resulting from first-pass effect in the liver, may be remedied by prodrug strategy. Based on esterase-sensitive carbamate prodrug strategy, a novel series of prodrugs of SQ109 has been reported. Bioavailability of SQ109 after administration of prodrug 7a was 91.4% compared with 21.4% after oral administration of SQ109. After oral administration of compound 7a, the parent drug SQ109 exhibited preferential tissue distribution into lung and spleen, the target organs of tubercular infection and replication.