We report 1,4-azaindoles as a new inhibitor class that kills Mycobacterium tuberculosis in vitro and demonstrates efficacy in mouse tuberculosis models. The series emerged from scaffold morphing efforts and was demonstrated to noncovalently inhibit decaprenylphosphoryl-β-D-ribose2'-epimerase (DprE1). With "drug-like" properties and no expectation of pre-existing resistance in the clinic, this chemical class has the potential to be developed as a therapy for drug-sensitive and drug-resistant tuberculosis.

New therapeutic strategies against multidrug-resistant (MDR) and extensively drug-resistant (XDR) Mycobacterium tuberculosis are urgently required to combat the global tuberculosis (TB) threat. Toward this end, we previously reported the identification of 1,4-azaindoles, a promising class of compounds with potent antitubercular activity through noncovalent inhibition of decaprenylphosphoryl-␤-D-ribose 2=-epimerase (DprE1). Further, this series was optimized to improve its physicochemical properties and pharmacokinetics in mice. Here, we describe the short-listing of a potential clinical candidate, compound 2, that has potent cellular activity, drug-like properties, efficacy in mouse and rat chronic TB infection models, and minimal in vitro safety risks. We also demonstrate that the compounds, including compound 2, have no antagonistic activity with other anti-TB drugs. Moreover, compound 2 shows synergy with PA824 and TMC207 in vitro, and the synergy effect is translated in vivo with TMC207. The series is predicted to have a low clearance in humans, and the predicted human dose for compound 2 is <1 g/day. Altogether, our data suggest that a 1,4-azaindole (compound 2) is a promising candidate for the development of a novel anti-TB drug.

Beta-lactams, in combination with beta-lactamase inhibitors, are reported to have activity against Mycobacterium tuberculosis bacteria growing in broth, as well as inside the human macrophage. We tested representative beta-lactams belonging to 3 different classes for activity against replicating M. tuberculosis in broth and nonreplicating M. tuberculosis under hypoxia, as well as against streptomycin-starved M. tuberculosis strain 18b (ss18b) in the presence or absence of clavulanate. Most of the combinations showed bactericidal activity against replicating M. tuberculosis, with up to 200-fold improvement in potency in the presence of clavulanate. None of the combinations, including those containing meropenem, imipenem, and faropenem, killed M. tuberculosis under hypoxia. However, faropenem-and meropenem-containing combinations killed strain ss18b moderately. We tested the bactericidal activities of meropenem-clavulanate and amoxicillin-clavulanate combinations in the acute and chronic aerosol infection models of tuberculosis in BALB/c mice. Based on pharmacokinetic/pharmacodynamic indexes reported for beta-lactams against other bacterial pathogens, a cumulative percentage of a 24-h period that the drug concentration exceeds the MIC under steady-state pharmacokinetic conditions (%T MIC ) of 20 to 40% was achieved in mice using a suitable dosing regimen. Both combinations showed marginal reduction in lung CFU compared to the late controls in the acute model, whereas both were inactive in the chronic model. Beta-lactam (BL) agents have been widely used for treating a broad spectrum of bacterial pathogens (1). However, there are very few reports on successful clinical use of beta-lactam antibiotics for the treatment of tuberculosis (TB). Mycobacterium tuberculosis is reported to produce a chromosomally encoded betalactamase enzyme (2, 3, 4) that degrades the beta-lactam agent, and therefore, use of BL along with a beta-lactamase inhibitor (BLI) like clavulanate is essential for killing M. tuberculosis. Many of the BL-BLI agents are reported to have a poor plasma half-life and poor oral bioavailability (1,5,6). Limitations of oral dosing and the requirement for frequent dosing for longer durations may have limited the use of BL-BLI agents for TB treatment. However, recent reports on successful treatment of patients with multidrugresistant and extremely drug-resistant (MDR/XDR) TB by including meropenem (7,8) in the second-line combination therapy have raised interest in understanding the efficacy of the meropenem-clavulanate combination in the mouse TB model (9). We have extended this interest to include understanding the pharmacokinetic-pharmacodynamic (PK-PD) relationship for meropenem-clavulanate and amoxicillin-clavulanate combinations in the mouse TB model. Discovery of novel anti-TB agents or therapies is essential to treat MDR/XDR TB, as well as to shorten the current 6-monthlong treatment of drug-sensitive TB. Therefore, activity against drug-resistant strains, as well as against both replicating and nonrepl...

No abstract

The cell envelope of Mycobacterium tuberculosis contains glycans and lipids of peculiar structure that play prominent roles in the biology and pathogenesis of tuberculosis. Consequently, the chemical structure and biosynthesis of the cell wall have been intensively investigated in order to identify novel drug targets. Here, we validate that the function of phosphatidyl-myo-inositol mannosyltransferase PimA is vital for M. tuberculosis in vitro and in vivo. PimA initiates the biosynthesis of phosphatidyl-myoinositol mannosides by transferring a mannosyl residue from GDP-Man to phosphatidyl-myo-inositol on the cytoplasmic side of the plasma membrane. To prove the essential nature of pimA in M. tuberculosis, we constructed a pimA conditional mutant by using the TetR-Pip off system and showed that downregulation of PimA expression causes bactericidality in batch cultures. Consistent with the biochemical reaction catalyzed by PimA, this phenotype was associated with markedly reduced levels of phosphatidyl-myo-inositol dimannosides, essential structural components of the mycobacterial cell envelope. In addition, the requirement of PimA for viability was clearly demonstrated during macrophage infection and in two different mouse models of infection, where a dramatic decrease in viable counts was observed upon silencing of the gene. Notably, depletion of PimA resulted in complete clearance of the mouse lungs during both the acute and chronic phases of infection. Altogether, the experimental data highlight the importance of the phosphatidyl-myo-inositol mannoside biosynthetic pathway for M. tuberculosis and confirm that PimA is a novel target for future drug discovery programs.T he lack of proper treatment for serious infectious diseases due to the emergence of multidrug resistance (MDR) underlines the need for the discovery of novel antibiotics (1). This is particularly true for tuberculosis (TB), for which 3.7% of new cases and 20% of previously treated cases are estimated to have MDR-TB. In several countries in Eastern Europe and central Asia, these numbers rise to 9 to 32% and more than 50%, respectively, making the situation particularly worrisome. In addition, in the case of TB, which claimed 1.3 million lives in 2012, the treatment of the leastcomplicated, drug-sensitive cases is lengthy and uncomfortable, and new drugs are urgently needed to shorten the regimen and make it more acceptable to the patients (2).The cell envelope of Mycobacterium tuberculosis represents a highly attractive target for the discovery of novel TB drugs. Supporting this notion, several key medicines used in the current TB therapy are inhibitors of essential enzymes participating in cell envelope biosynthesis. The first-line drug ethambutol has been shown to target at least three unique integral membrane-associated arabinofuranosyltransferases (EmbA, EmbB, and EmbC) involved in the biosynthesis of arabinogalactan (AG) and lipoarabinomannan (LAM) (3, 4). The inhibition of InhA by isoniazid (INH) in M. tuberculosis leads to the specific depl...

Tuberculosis (TB) has been a human disease for centuries. Its frequency is increased manyfold in patients with liver cirrhosis. The gold standard of TB management is a 6-mo course of isoniazid, rifampicin, pyrazinamide and ethambutol. Although good results are seen with this treatment in general, the management of patients with underlying cirrhosis is a challenge. The underlying depressed immune response results in alterations in many diagnostic tests. The tests used for latent TB have many flaws in this group of patients. Three of four first-line antitubercular drugs are hepatotoxic and baseline liver function is often disrupted in patients with underlying cirrhosis. Frequency of hepatotoxicity is increased in patients with liver cirrhosis, frequently leading to severe liver failure. There are no established guidelines for the treatment of TB in relation to the severity of liver disease. There is no consensus on the frequency of liver function tests required or the cut-off used to define hepatotoxicity. No specific treatment exists for prevention or treatment of hepatotoxicity, making monitoring even more important. A high risk of multidrug-resistant TB is another major worry due to prolonged and interrupted treatment.

Intragastric balloon placement is a useful modality for promoting short-term weight loss and thereby making morbidly obese recipients fit for liver transplantation surgery.

Helicobacter pylori is an important cause of chronic gastritis leading to peptic ulcer and is a major risk factor for gastric malignancies. Failure in the eradication of H. pylori infection and increasing antibiotic resistance are two major problems in preventing H. pylori colonization. Hence, a deeper understanding of the bacterial survival strategies is needed to tackle the increasing burden of H. pylori infection by an appropriate intervention. Our study demonstrated that the lack of cholesteryl glucosides (CGs) remarkably altered the morphology of H. pylori and increased permeability of the bacterial cell wall. Further, this study highlighted the substantial role of CGs in maintaining the typical H. pylori morphology that is essential for retaining its pathogenic potential. We also demonstrated that the loss of CGs in H. pylori renders the bacterium susceptible to different antibiotics.