pbtz169 and Tuberculosis--Multidrug-Resistant

Despite enormous efforts have been made in the hunt for new drugs, tuberculosis (TB) still remains the first bacterial cause of mortality worldwide, causing an estimated 8.6 million new cases and 1.3 million deaths in 2012. Multi-drug resistant-TB strains no longer respond to first-line drugs and are inexorably spreading with an estimated 650,000 cases as well as extensively-drug resistant-TB strains, which are resistant to any fluoroquinolone and at least one of the second-line drugs, with 60,000 cases. Thus the discovery and development of new medicines is a major keystone for tuberculosis treatment and control. After decades of dormancy in the field of TB drug development, recent efforts from various groups have generated a promising TB drug pipeline. Several new therapeutic agents are concurrently studied in clinical trials together with much activity in the hittolead and lead optimization stages. In this article we will review the recent advances in TB drug discovery with a special focus on structure activity relationship studies of the most advanced compound classes.

Topics: Animals; Antitubercular Agents; Humans; Mycobacterium tuberculosis; Structure-Activity Relationship; Tuberculosis; Tuberculosis, Multidrug-Resistant

Tuberculosis, and especially multidrug-resistant tuberculosis (MDR-TB), is a major global health threat which emphasizes the need to develop new agents to improve and shorten treatment of this difficult-to-manage infectious disease. Among the new agents, macozinone (PBTZ169) is one of the most promising candidates, showing extraordinary potency in vitro and in murine models against drug-susceptible and drug-resistant Mycobacterium tuberculosis. A previous analytical method using liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) was developed by our group to support phase I clinical trials of PBTZ169. These plasma sample analyses revealed the presence of several additional metabolites among which the most prominent was H

Topics: Animals; Chromatography, Liquid; Clinical Trials, Phase I as Topic; Humans; Mammals; Mice; Piperazines; Reproducibility of Results; Tandem Mass Spectrometry; Tuberculosis; Tuberculosis, Multidrug-Resistant

Tuberculosis (TB) is the leading cause of death from any bacterial infection, causing 1.5 million deaths worldwide each year. Due to the emergence of drug-resistant strains of Mycobacterium tuberculosis (Mtb) there have been significant efforts aimed at developing novel drugs to treat TB. One promising drug target in Mtb is the arabinogalactan biosynthetic enzyme DprE1, and there have been over a dozen unique chemical scaffolds identified which inhibit the activity of this protein. Among the most promising lead compounds are the benzothiazinones BTZ043 and PBTZ169, both of which are currently in or have completed phase IIa clinical trials. Due to the potential clinical utility of these drugs, we sought to identify potential synergistic interactions and new mechanisms of resistance using a genome-scale CRISPRi chemical-genetic screen with PBTZ169. We found that knockdown of

Topics: Antitubercular Agents; Diarylquinolines; Humans; Microbial Sensitivity Tests; Mutation; Mycobacterium tuberculosis; Piperazines; Spiro Compounds; Thiazines; Tuberculosis; Tuberculosis, Multidrug-Resistant

A series of new benzothiazinone derivatives containing a symmetric 2-benzyl-2,7-diazaspiro[3.5]nonane moiety, based on the structure of LK02 discovered in our lab, were designed and synthesized. With one exception 3, all of them show excellent in vitro activity against both drug-sensitive and clinically isolated multidrug-resistant Mycobacterium tuberculosis (MTB) strains (MIC: < 0.016 μg/mL). Compound 2d with a methyl group at the benzylic carbon, was identified to have good safety and significant efficacy in an acute mouse model of TB, as well as better PK profiles than PBTZ169.

Topics: Alkanes; Animals; Antitubercular Agents; Drug Design; Drug Resistance; Mice; Mycobacterium tuberculosis; Structure-Activity Relationship; Thiazines; Tuberculosis, Multidrug-Resistant

A piperazine-containing benzothiazinones lead compound PBTZ169, served as DprE1 inhibitor, displays nanomolar bactericidal activity against Mycobacteria tuberculosis. Here, we systematically evaluate anti-tuberculosis activity of one of PBTZ169 analogues, TZY-5-84, in vitro and in vivo. The MIC value of TZY-5-84 against M. tuberculosis H37Rv ranged from 0.014 to 0.015 mg/L, lower than those of INH, RFP and BDQ. Five susceptible and thirteen drug-resistant clinical isolates were also susceptive to TZY-5-84. It had anti-tuberculosis activity against intracellular bacilli in infected macrophage model. It exhibited its activity in time-dependent manner and against intracellular bacilli in infected macrophage cells. However, the MIC of TZY-5-84 against three laboratory PBTZ169-induced resistant isolates increased four-fold increment compared to that of H37Rv. No antagonism was observed in any combination between TZY-5-84 and seven commonly used anti-tuberculosis drugs in an in vitro checkerboard assay. In murine infection model, TZY-5-84 at lower dosage (12.5 mg/kg) was found to be comparatively efficacious as PBTZ169 at 25 mg/kg. Our research suggests TZY-5-84 can be a promising preclinical candidate for further study on TB treatment.

Topics: Animals; Antitubercular Agents; Dose-Response Relationship, Drug; Female; Macrophages; Male; Mice; Mice, Inbred BALB C; Mice, Inbred C3H; Microbial Sensitivity Tests; Mycobacterium tuberculosis; Piperazine; Piperazines; Thiazines; Time Factors; Tuberculosis; Tuberculosis, Multidrug-Resistant

The emergence of Mycobacterium tuberculosis strains resistant to current first-line antibiotic regimens constitutes a major global health threat. New treatments against multidrug-resistant tuberculosis (MDR-TB) are thus eagerly needed in particular in countries with a high MDR-TB prevalence. In this context, macozinone (PBTZ169), a promising drug candidate with an unique mode of action and highly potent in vitro tuberculocidal properties against MDR Mycobacterium strains, has now reached the clinical phase and has been notably tested in healthy male volunteers in Switzerland. To that endeavor, a multiplex UHPLC-MS/MS method has been developed for the sensitive and accurate human plasma levels determination of PBTZ169 along with five metabolites retaining in vitro anti-TB activity. Plasma protein precipitation with methanol was carried out as a simplified sample clean-up procedure followed by direct injection of the undiluted supernatant for the bioanalysis of the six analytes within 5 min, using 1.8 μm reversed-phase chromatography coupled to triple quadrupole mass spectrometry employing electrospray ionization in the positive mode. Stable isotopically-labelled PBTZ169 was used as internal standard (ISTD), while metabolites could be reliably quantified using two unlabeled chemical analogues selected as ISTD from a large in-house analogous compounds library. The overall methodology was fully validated according to current recommendations (FDA, EMEA) for bioanalytical methods, which include selectivity, carryover, qualitative and quantitative matrix effect, extraction recovery, process efficiency, trueness, precision, accuracy profiles, method and instrument detection limits, integrity to dilution, anticoagulant comparison and short- and long-term stabilities. Stability studies on the reduced metabolite H2-PBTZ169 have shown no significant impact on the actual PBTZ169 concentrations determined with the proposed assay. This simplified, rapid, sensitive and robust methodology has been applied to the bioanalysis of human plasma samples collected within the frame of a phase I clinical study in healthy volunteers receiving PBTZ169.

Topics: Anti-Bacterial Agents; Antitubercular Agents; Chromatography, High Pressure Liquid; Drugs, Investigational; Humans; Male; Metabolome; Mycobacterium tuberculosis; Piperazines; Reproducibility of Results; Switzerland; Tandem Mass Spectrometry; Thiazines; Tuberculosis, Multidrug-Resistant

Benzothiazinones (BTZs) are a class of compounds found to be extremely potent against both drug-susceptible and drug-resistant Mycobacterium tuberculosis strains. The potency of BTZs is explained by their specificity for their target decaprenylphosphoryl-d-ribose oxidase (DprE1), in particular by covalent binding of the activated form of the compound to the critical cysteine 387 residue of the enzyme. To probe the role of C387, we used promiscuous site-directed mutagenesis to introduce other codons at this position into dprE1 of M. tuberculosis The resultant viable BTZ-resistant mutants were characterized in vitro, ex vivo, and biochemically to gain insight into the effects of these mutations on DprE1 function and on M. tuberculosis Five different mutations (C387G, C387A, C387S, C387N, and C387T) conferred various levels of resistance to BTZ and exhibited different phenotypes. The C387G and C387N mutations resulted in a lower growth rate of the mycobacterium on solid medium, which could be attributed to the significant decrease in the catalytic efficiency of the DprE1 enzyme. All five mutations rendered the mycobacterium less cytotoxic to macrophages. Finally, differences in the potencies of covalent and noncovalent DprE1 inhibitors in the presence of C387 mutations were revealed by enzymatic assays. As expected from the mechanism of action, the covalent inhibitor PBTZ169 only partially inhibited the mutant DprE1 enzymes compared to the near-complete inhibition with a noncovalent DprE1 inhibitor, Ty38c. This study emphasizes the importance of the C387 residue for DprE1 activity and for the killing action of covalent inhibitors such as BTZs and other recently identified nitroaromatic inhibitors.

Topics: Alcohol Oxidoreductases; Amino Acid Substitution; Antitubercular Agents; Bacterial Proteins; Cell Line; Cysteine; Drug Resistance, Multiple, Bacterial; Enzyme Inhibitors; Gene Expression; Humans; Macrophages; Molecular Docking Simulation; Mutagenesis, Site-Directed; Mutation; Mycobacterium smegmatis; Mycobacterium tuberculosis; Phenotype; Piperazines; Structure-Activity Relationship; Thiazines; Tuberculosis, Multidrug-Resistant

Clofazimine (CZM) is an antileprosy drug that was recently repurposed for treatment of multidrug-resistant tuberculosis. In Mycobacterium tuberculosis, CZM appears to act as a prodrug, which is reduced by NADH dehydrogenase (NDH-2), to release reactive oxygen species upon reoxidation by O2. CZM presumably competes with menaquinone (MK-4), a key cofactor in the mycobacterial electron transfer chain, for its reduction by NDH-2. We studied the effect of MK-4 supplementation on the activity of CZM against M. tuberculosis and found direct competition between CZM and MK-4 for the cidal effect of CZM, against nonreplicating and actively growing bacteria, as MK-4 supplementation blocked the drug's activity against nonreplicating bacteria. We demonstrated that CZM, like bedaquiline, is synergistic in vitro with benzothiazinones such as 2-piperazino-benzothiazinone 169 (PBTZ169), and this synergy also occurs against nonreplicating bacteria. The synergy between CZM and PBTZ169 was lost in an MK-4-rich medium, indicating that MK-4 is the probable link between their activities. The efficacy of the dual combination of CZM and PBTZ169 was tested in vivo, where a great reduction in bacterial load was obtained in a murine model of chronic tuberculosis. Taken together, these data confirm the potential of CZM in association with PBTZ169 as the basis for a new regimen against drug-resistant strains of M. tuberculosis.

Topics: Animals; Antitubercular Agents; Clofazimine; Diarylquinolines; Drug Therapy, Combination; Female; Mice; Mice, Inbred BALB C; Mycobacterium tuberculosis; Piperazines; Thiazines; Tuberculosis, Multidrug-Resistant; Vitamin K 2