Towards a new combination therapy for tuberculosis with next generation benzothiazinones

Zumla A., Nahid P., Cole S.T.

Tuberculosis (TB) continues to cause considerable morbidity and mortality worldwide and there is an urgent need for novel therapies and treatment regimens of shorter duration. Here, Zumla, Nahid and Cole discuss current concepts and recent advances in TB drug discovery, development and clinical trial evaluation, and provide an update of new agents and approaches currently being investigated. Despite the introduction 40 years ago of the inexpensive and effective four-drug (isoniazid, rifampicin, pyrazinamide and ethambutol) treatment regimen, tuberculosis (TB) continues to cause considerable morbidity and mortality worldwide. For the first time since the 1960s, new and novel drugs and regimens for all forms of TB are emerging. Such regimens are likely to utilize both repurposed drugs and new chemical entities, and several of these regimens are now progressing through clinical trials. This article covers current concepts and recent advances in TB drug discovery and development, including an update of ongoing TB treatment trials, newer clinical trial designs, TB biomarkers and adjunct host-directed therapies.

Tiwari R., Moraski G.C., Krchňák V., Miller P.A., Colon-Martinez M., Herrero E., Oliver A.G., Miller M.J.

The development of multidrug resistant (MDR) and extensively drug resistant (XDR) forms of tuberculosis (TB) has stimulated research efforts globally to expand the new drug pipeline. Nitroaromatic compounds, including 1,3-benzothiazin-4-ones (BTZs) and related agents, are a promising new class for the treatment of TB. Research has shown that the nitroso intermediates of BTZs that are generated in vivo cause suicide inhibition of decaprenylphosphoryl-β-D-ribose 2' oxidase (DprE1), which is responsible for cell wall arabinogalactan biosynthesis. We have designed and synthesized novel anti-TB agents inspired from BTZs and other nitroaromatic compounds. Computational studies indicated that the unsubstituted aromatic carbons of BTZ043 and related nitroaromatic compounds are the most electron-deficient and might be prone to nucleophilic attack. Our chemical studies on BTZ043 and the additional nitroaromatic compounds synthesized by us and others confirmed the postulated reactivity. The results indicate that nucleophiles such as thiolates, cyanide, and hydride induce nonenzymatic reduction of the nitro groups present in these compounds to the corresponding nitroso intermediates by addition at the unsubstituted electron-deficient aromatic carbon present in these compounds. Furthermore, we demonstrate here that these compounds are good candidates for the classical von Richter reaction. These chemical studies offer an alternate hypothesis for the mechanism of action of nitroaromatic anti-TB agents, in that the cysteine thiol(ate) or a hydride source at the active site of DprE1 may trigger the reduction of the nitro groups in a manner similar to the von Richter reaction to the nitroso intermediates, to initiate the inhibition of DprE1.

Lechartier B., Hartkoorn R.C., Cole S.T.

ABSTRACT Benzothiazinones (BTZ) are a new class of drug candidates to combat tuberculosis that inhibit decaprenyl-phosphoribose epimerase (DprE1), an essential enzyme involved in arabinan biosynthesis. Using the checkerboard method and cell viability assays, we have studied the interaction profiles of BTZ043, the current lead compound, with several antituberculosis drugs or drug candidates against Mycobacterium tuberculosis strain H37Rv, namely, rifampin, isoniazid, ethambutol, TMC207, PA-824, moxifloxacin, meropenem with or without clavulanate, and SQ-109. No antagonism was found between BTZ043 and the tested compounds, and most of the interactions were purely additive. Data from two different approaches clearly indicate that BTZ043 acts synergistically with TMC207, with a fractional inhibitory concentration index of 0.5. TMC207 at a quarter of the MIC (20 ng/ml) used in combination with BTZ043 (1/4 MIC, 0.375 ng/ml) had a stronger bactericidal effect on M. tuberculosis than TMC207 alone at a concentration of 80 ng/ml. This synergy was not observed when the combination was tested on a BTZ-resistant M. tuberculosis mutant, suggesting that DprE1 inhibition is the basis for the interaction. This finding excludes the possibility of synergy occurring through an off-target mechanism. We therefore hypothesize that sub-MICs of BTZ043 weaken the bacterial cell wall and allow improved penetration of TMC207 to its target. Synergy between two new antimycobacterial compounds, such as TMC207 and BTZ043, with novel targets, offers an attractive foundation for a new tuberculosis regimen.

Neres J., Pojer F., Molteni E., Chiarelli L.R., Dhar N., Boy-Röttger S., Buroni S., Fullam E., Degiacomi G., Lucarelli A.P., Read R.J., Zanoni G., Edmondson D.E., De Rossi E., Pasca M.R., et. al.

The crystal structure of the mycobacterial DprE1 reveals how the TB drug benzothiazinone BTZ043 blocks this microbial enzyme target.

Diacon A.H., Dawson R., von Groote-Bidlingmaier F., Symons G., Venter A., Donald P.R., van Niekerk C., Everitt D., Winter H., Becker P., Mendel C.M., Spigelman M.K.

New drugs, but also shorter, better-tolerated regimens are needed to tackle the high global burden of tuberculosis complicated by drug resistance and retroviral disease. We investigated new multiple-agent combinations over the first 14 days of treatment to assess their suitability for future development.In this prospective, randomised, early bactericidal activity (EBA) study, treatment-naive, drug-susceptible patients with uncomplicated pulmonary tuberculosis were admitted to hospitals in Cape Town, South Africa, between Oct 7, 2010, and Aug 19, 2011. Patients were randomised centrally by computer-generated randomisation sequence to receive bedaquiline, bedaquiline-pyrazinamide, PA-824-pyrazinamide, bedaquiline-PA-824, PA-824-moxifloxacin-pyrazinamide, or unmasked standard antituberculosis treatment as positive control. The primary outcome was the 14-day EBA assessed in a central laboratory from the daily fall in colony forming units (CFU) of M tuberculosis per mL of sputum in daily overnight sputum collections. Bilinear regression curves were fitted for each group separately and groups compared with ANOVA for ranks, followed by pair-wise comparisons adjusted for multiplicity. Clinical staff were partially masked but laboratory personnel were fully masked. This study is registered, NCT01215851.The mean 14-day EBA of PA-824-moxifloxacin-pyrazinamide (n=13; 0·233 [SD 0·128]) was significantly higher than that of bedaquiline (14; 0·061 [0·068]), bedaquiline-pyrazinamide (15; 0·131 [0·102]), bedaquiline-PA-824 (14; 0·114 [0·050]), but not PA-824-pyrazinamide (14; 0·154 [0·040]), and comparable with that of standard treatment (ten; 0·140 [0·094]). Treatments were well tolerated and appeared safe. One patient on PA-824-moxifloxacin-pyrazinamide was withdrawn because of corrected QT interval changes exceeding criteria prespecified in the protocol.PA-824-moxifloxacin-pyrazinamide is potentially suitable for treating drug-sensitive and multidrug-resistant tuberculosis. Multiagent EBA studies can contribute to reducing the time needed to develop new antituberculosis regimens.The Global Alliance for TB Drug Development (TB Alliance).

Vera-Cabrera L., Campos-Rivera M.P., Gonzalez-Martinez N.A., Ocampo-Candiani J., Cole S.T.

ABSTRACT The in vitro activity of PA-824 and BTZ043 against 30 Nocardia brasiliensis isolates was tested. The MIC 50 and MIC 90 values for PA-824 were both >64 μg/ml. The same values for BTZ043 were 0.125 and 0.250 μg/ml. Given the MIC values for benzothiazinone (BTZ) compounds, we consider them good candidates to be tested in vivo against N. brasiliensis .

Batt S.M., Jabeen T., Bhowruth V., Quill L., Lund P.A., Eggeling L., Alderwick L.J., Fütterer K., Besra G.S.

Resistance against currently used antitubercular therapeutics increasingly undermines efforts to contain the worldwide tuberculosis (TB) epidemic. Recently, benzothiazinone (BTZ) inhibitors have shown nanomolar potency against both drug-susceptible and multidrug-resistant strains of the tubercle bacillus. However, their proposed mode of action is lacking structural evidence. We report here the crystal structure of the BTZ target, FAD-containing oxidoreductase Mycobacterium tuberculosis DprE1, which is essential for viability. Different crystal forms of ligand-free DprE1 reveal considerable levels of structural flexibility of two surface loops that seem to govern accessibility of the active site. Structures of complexes with the BTZ-derived nitroso derivative CT325 reveal the mode of inhibitor binding, which includes a covalent link to conserved Cys387, and reveal a trifluoromethyl group as a second key determinant of interaction with the enzyme. Surprisingly, we find that a noncovalent complex was formed between DprE1 and CT319, which is structurally identical to CT325 except for an inert nitro group replacing the reactive nitroso group. This demonstrates that binding of BTZ-class inhibitors to DprE1 is not strictly dependent on formation of the covalent link to Cys387. On the basis of the structural and activity data, we propose that the complex of DrpE1 bound to CT325 is a representative of the BTZ-target complex. These results mark a significant step forward in the characterization of a key TB drug target.

Gler M.T., Skripconoka V., Sanchez-Garavito E., Xiao H., Cabrera-Rivero J.L., Vargas-Vasquez D.E., Gao M., Awad M., Park S., Shim T.S., Suh G.Y., Danilovits M., Ogata H., Kurve A., Chang J., et. al.

BACKGROUND Delamanid (OPC-67683), a nitro-dihydro-imidazooxazole derivative, is a new antituberculosis medication that inhibits mycolic acid synthesis and has shown potent in vitro and in vivo activity against drug-resistant strains of Mycobacterium tuberculosis. METHODS In this randomized, placebo-controlled, multinational clinical trial, we assigned 481 patients (nearly all of whom were negative for the human immunodeficiency virus) with pulmonary multidrug-resistant tuberculosis to receive delamanid, at a dose of 100 mg twice daily (161 patients) or 200 mg twice daily (160 patients), or placebo (160 patients) for 2 months in combination with a background drug regimen developed according to World Health Organization guidelines. Sputum cultures were assessed weekly with the use of both liquid broth and solid medium; sputum-culture conversion was defined as a series of five or more consecutive cultures that were negative for growth of M. tuberculosis. The primary efficacy end point was the proportion of patients with sputum-culture conversion in liquid broth medium at 2 months. RESULTS Among patients who received a background drug regimen plus 100 mg of delamanid twice daily, 45.4% had sputum-culture conversion in liquid broth at 2 months, as compared with 29.6% of patients who received a background drug regimen plus placebo (P=0.008). Likewise, as compared with the placebo group, the group that received the background drug regimen plus 200 mg of delamanid twice daily had a higher proportion of patients with sputum-culture conversion (41.9%, P=0.04). The findings were similar with assessment of sputum-culture conversion in solid medium. Most adverse events were mild to moderate in severity and were evenly distributed across groups. Although no clinical events due to QT prolongation on electrocardiography were observed, QT prolongation was reported significantly more frequently in the groups that received delamanid. CONCLUSIONS Delamanid was associated with an increase in sputum-culture conversion at 2 months among patients with multidrug-resistant tuberculosis. This finding suggests that delamanid could enhance treatment options for multidrug-resistant tuberculosis. (Funded by Otsuka Pharmaceutical Development and Commercialization; ClinicalTrials.gov number, NCT00685360.).

Tahlan K., Wilson R., Kastrinsky D.B., Arora K., Nair V., Fischer E., Barnes S.W., Walker J.R., Alland D., Barry C.E., Boshoff H.I.

ABSTRACT SQ109, a 1,2-diamine related to ethambutol, is currently in clinical trials for the treatment of tuberculosis, but its mode of action remains unclear. Here, we demonstrate that SQ109 disrupts cell wall assembly, as evidenced by macromolecular incorporation assays and ultrastructural analyses. SQ109 interferes with the assembly of mycolic acids into the cell wall core of Mycobacterium tuberculosis, as bacilli exposed to SQ109 show immediate inhibition of trehalose dimycolate (TDM) production and fail to attach mycolates to the cell wall arabinogalactan. These effects were not due to inhibition of mycolate synthesis, since total mycolate levels were unaffected, but instead resulted in the accumulation of trehalose monomycolate (TMM), the precursor of TDM and cell wall mycolates. In vitro assays using purified enzymes showed that this was not due to inhibition of the secreted Ag85 mycolyltransferases. We were unable to achieve spontaneous generation of SQ109-resistant mutants; however, analogs of this compound that resulted in similar shutdown of TDM synthesis with concomitant TMM accumulation were used to spontaneously generate resistant mutants that were also cross-resistant to SQ109. Whole-genome sequencing of these mutants showed that these all had mutations in the essential mmpL3 gene, which encodes a transmembrane transporter. Our results suggest that MmpL3 is the target of SQ109 and that MmpL3 is a transporter of mycobacterial TMM.

Trefzer C., Škovierová H., Buroni S., Bobovská A., Nenci S., Molteni E., Pojer F., Pasca M.R., Makarov V., Cole S.T., Riccardi G., Mikušová K., Johnsson K.

Benzothiazinones (BTZs) are antituberculosis drug candidates with nanomolar bactericidal activity against tubercle bacilli. Here we demonstrate that BTZs are suicide substrates of the FAD-dependent decaprenylphosphoryl-β-D-ribofuranose 2'-oxidase DprE1, an enzyme involved in cell-wall biogenesis. BTZs are reduced by DprE1 to an electrophile, which then reacts in a near-quantitative manner with an active-site cysteine of DprE1, thus providing a rationale for the extraordinary potency of BTZs. Mutant DprE1 enzymes from BTZ-resistant strains reduce BTZs to inert metabolites while avoiding covalent inactivation. Our results explain the basis for drug sensitivity and resistance to an exceptionally potent class of antituberculosis agents.

Adams K., Takaki K., Connolly L., Wiedenhoft H., Winglee K., Humbert O., Edelstein P., Cosma C., Ramakrishnan L.

Treatment of tuberculosis, a complex granulomatous disease, requires long-term multidrug therapy to overcome tolerance, an epigenetic drug resistance that is widely attributed to nonreplicating bacterial subpopulations. Here, we deploy Mycobacterium marinum-infected zebrafish larvae for in vivo characterization of antitubercular drug activity and tolerance. We describe the existence of multidrug-tolerant organisms that arise within days of infection, are enriched in the replicating intracellular population, and are amplified and disseminated by the tuberculous granuloma. Bacterial efflux pumps that are required for intracellular growth mediate this macrophage-induced tolerance. This tolerant population also develops when Mycobacterium tuberculosis infects cultured macrophages, suggesting that it contributes to the burden of drug tolerance in human tuberculosis. Efflux pump inhibitors like verapamil reduce this tolerance. Thus, the addition of this currently approved drug or more specific efflux pump inhibitors to standard antitubercular therapy should shorten the duration of curative treatment.

Stoop E.J., Schipper T., Rosendahl Huber S.K., Nezhinsky A.E., Verbeek F.J., Gurcha S.S., Besra G.S., Vandenbroucke-Grauls C.M., Bitter W., van der Sar A.M.

SUMMARY The hallmark of tuberculosis (TB) is the formation of granulomas, which are clusters of infected macrophages surrounded by additional macrophages, neutrophils and lymphocytes. Although it has long been thought that granulomas are beneficial for the host, there is evidence that mycobacteria also promote the formation of these structures. In this study, we aimed to identify new mycobacterial factors involved in the initial stages of granuloma formation. We exploited the zebrafish embryo Mycobacterium marinum infection model to study initiation of granuloma formation and developed an in vivo screen to select for random M. marinum mutants that were unable to induce granuloma formation efficiently. Upon screening 200 mutants, three mutants repeatedly initiated reduced granuloma formation. One of the mutants was found to be defective in the espL gene, which is located in the ESX-1 cluster. The ESX-1 cluster is disrupted in the Mycobacterium bovis BCG vaccine strain and encodes a specialized secretion system known to be important for granuloma formation and virulence. Although espL has not been implicated in protein secretion before, we observed a strong effect on the secretion of the ESX-1 substrates ESAT-6 and EspE. We conclude that our zebrafish embryo M. marinum screen is a useful tool to identify mycobacterial genes involved in the initial stages of granuloma formation and that we have identified a new component of the ESX-1 secretion system. We are confident that our approach will contribute to the knowledge of mycobacterial virulence and could be helpful for the development of new TB vaccines.

Koul A., Arnoult E., Lounis N., Guillemont J., Andries K.

Although vaccination has been successful in some countries, tuberculosis (TB) is more prevalent in the world today than ever before, with nearly 10 million new cases expected yearly. Anil Koul and colleagues report on the various new TB drugs and treatment regimens under development. The prospects for some of them are good, they conclude, but the TB pathogen Mycobacterium tuberculosis deploys a range of mechanisms to evade host-control measures, so it will be important to keep the drugs pipeline well supplied. In addition, successful control of TB will depend on economic and societal measures to bolster health-care infrastructure in developing countries where TB is particularly prevalent. Tuberculosis (TB) is more prevalent in the world today than at any other time in human history. Mycobacterium tuberculosis, the pathogen responsible for TB, uses diverse strategies to survive in a variety of host lesions and to evade immune surveillance. A key question is how robust are our approaches to discovering new TB drugs, and what measures could be taken to reduce the long and protracted clinical development of new drugs. The emergence of multi-drug-resistant strains of M. tuberculosis makes the discovery of new molecular scaffolds a priority, and the current situation even necessitates the re-engineering and repositioning of some old drug families to achieve effective control. Whatever the strategy used, success will depend largely on our proper understanding of the complex interactions between the pathogen and its human host. In this review, we discuss innovations in TB drug discovery and evolving strategies to bring newer agents more quickly to patients.

Trefzer C., Rengifo-Gonzalez M., Hinner M.J., Schneider P., Makarov V., Cole S.T., Johnsson K.

Benzothiazinones (BTZs) form a new class of potent antimycobacterial agents. Although the target of BTZs has been identified as decaprenylphosphoryl-β-D-ribose 2'-epimerase (DprE1), their detailed mechanism of action remains obscure. Here we demonstrate that BTZs are activated in the bacterium by reduction of an essential nitro group to a nitroso derivative, which then specifically reacts with a cysteine residue in the active site of DprE1.

Manina G., Bellinzoni M., Pasca M.R., Neres J., Milano A., De Jesus Lopes Ribeiro A.L., Buroni S., Škovierová H., Dianišková P., Mikušová K., Marák J., Makarov V., Giganti D., Haouz A., Lucarelli A.P., et. al.

Mhetre U.V., Bhagat A.N., Londhe S.V., Salunke S.S., More R.A., Rathod S.S., Choudhari P.B., Haval K.P.

Eke I.E., Abramovitch R.B.

ABSTRACT Tuberculosis is a respiratory infection that is caused by members of the Mycobacterium tuberculosis complex, with M. tuberculosis (Mtb) being the predominant cause of the disease in humans. The approval of pretomanid and delamanid, two nitroimidazole-based compounds, for the treatment of tuberculosis encourages the development of more nitro-containing drugs that target Mtb. Similar to the nitroimidazoles, many antimycobacterial nitro-containing scaffolds are prodrugs that require reductive activation into metabolites that inhibit the growth of the pathogen. This reductive activation is mediated by mycobacterial nitroreductases, leading to the hypothesis that these nitroreductases contribute to the specificity of the nitro prodrugs for mycobacteria. In addition to their prodrug-activating activities, these nitroreductases have different native activities that support the growth of the bacteria. This review summarizes the activities of different mycobacterial nitroreductases with respect to their activation of different nitro prodrugs and highlights their physiological functions in the bacteria.

Raghu M.S., Jassim A.Y., Kumar K.Y., Alharethy F., Prashanth M.K., Jeon B.

Objective: As a possible antitubercular agent, we disclose in this study the design and synthesis of a novel series of benzothiazinone derivatives (Va–Vi), contributing to the worldwide fight to eradicate TB, one of the deadliest infectious killers in the world. Methods: The newly synthesized benzothiazinone derivatives were characterized using various spectroscopic and elemental analysis techniques. The antituberculosis activity of the synthesized benzothiazinone derivatives was evaluated against drug-sensitive Mtb H37Rv and MDR-TB strains. To explain their inhibitory qualities, potent compounds underwent molecular docking studies. The synthetic molecules’ ability to function as lead-like molecules and the drug-likeness of the compounds were computed using the SwissADME online tool. Results and Discussion: With a MIC of 0.01 and 0.21 µM, respectively, compound (Vi) showed the most promising antitubercular efficacy against drug-sensitive Mtb H37Rv and MDR-TB strains. Four of the nine studied compounds had strong DprE1 inhibitory action, with IC50 values ranging from 0.02 to 0.79 μM. The molecular docking findings indicated that these compounds had a high docking score and a strong binding affinity to the target DprE1 protein’s active pocket. Conclusions: The current study demonstrated the potential significance of novel benzothiazinone derivatives as antitubercular prospects, and further investigation into optimization may lead to the creation of new antitubercular medication candidates.

Shaik B.B., Moodley K., Ghumran S., Bala M.D., Singh P., Karpoormath R.

ABSTRACTAntitubercular drug discovery progress in the last decade, especially research on the biological function, target inhibition and diagnosis of tuberculosis (TB) diagnosis has considerably advanced. The application of target‐based drug discovery techniques have become a more powerful tool for medicinal chemists in developing new therapeutic strategies, such as its application in the identification/validation of new targets, new leads, and drug candidates with optimized efficacy. This has been further evidenced by the recent approval of delamanid and bedaquiline for the treatment of MDR‐TB and XDR‐TB, respectively. While a TB drug pipeline has shown great development, high attrition rates must constantly replenish the pipeline with high‐quality leads acting through the inhibition of new targets. This review provides a critical analysis of the approaches used to advance hit compounds into viable lead candidates as well as the possible influence of new targets on drug development in the near future. Finally, we concluded with the present challenges that are faced in TB drug development.

Bakale R.D., Bhagat A.N., Mhetre U.V., Londhe S.V., Rathod S.S., Choudhari P.B., Haval K.P.

Kufa M., Finger V., Kovar O., Soukup O., Torrueallas C., Roh J., Korabecny J.

Komm O.D., Tyagi S., Garcia A., Almeida D., Chang Y., Li S., Castillo J.R., Converse P.J., Black T., Fotouhi N., Nuermberger E.L.

ABSTRACT The clinical efficacy of combination drug regimens containing the first-generation diarylquinoline (DARQ) bedaquiline in the treatment of multidrug-resistant tuberculosis has validated ATP synthesis as a vulnerable pathway in Mycobacterium tuberculosis . New DARQs in clinical development may be even more effective than bedaquiline, including against emerging bedaquiline-resistant strains. Telacebec (T) is a novel cytochrome bc 1 :aa 3 oxidase inhibitor that also inhibits ATP synthesis. Based on its demonstrated efficacy as a monotherapy in mice and in a phase 2a clinical trial, we tested the contribution of T to novel combination therapies against two strains of M. tuberculosis (H37Rv and HN878) in an established BALB/c mouse model of tuberculosis in an effort to find more effective regimens. Overall, T was more effective in regimens against the HN878 strain than against the H37Rv strain, a finding supported by the greater vulnerability of the former strain to T and to genetic depletion of QcrB. Against both strains, combinations of a DARQ, clofazimine, and T were highly bactericidal. However, only against HN878 did T contribute synergistically, whereas an antagonistic effect was observed against H37Rv. These results demonstrate the therapeutic potential of T and highlight how differences in the susceptibility of M. tuberculosis strains could lead to different conclusions about a drug’s potential contribution to novel drug regimens. CLINICAL TRIALS This study is registered with Clinicaltrials.gov as NCT04890535 and NCT06058299 .

Vocat A., Luraschi-Eggemann A., Antoni C., Cathomen G., Cichocka D., Greub G., Riabova O., Makarov V., Opota O., Mendoza A., Cole S.T., Sturm A.

ABSTRACT Novel drugs and improved diagnostics for Mycobacterium tuberculosis (MTB) are urgently needed and go hand in hand. We evaluated the in vitro activity of two benzothiazinone drug candidates (MCZ, PBTZ169; BTZ043) and their main metabolites against MTB using advanced nanomotion technology. The results demonstrated significant reductions in MTB viability within 7 h, indicating the potential for rapid, precise antibiotic susceptibility testing based on a phenotypic read-out in real time. PBTZ169 and H 2 -PBTZ169 achieved 100% separation between the susceptible H37Rv and a resistant dprE1 mutant strain NTB1. These findings support nanomotion technology’s potential for faster antibiotic susceptibility testing of novel MTB drug candidates targeting the DprE1 enzyme that could reduce empirical treatment duration and antibiotic resistance selection pressure due to inaccurate treatments.

Heimann D., Kohnhäuser D., Kohnhäuser A.J., Brönstrup M.

The rise of antimicrobial resistance represents a significant global health threat, driven by the diminishing efficacy of existing antibiotics, a lack of novel antibacterials entering the market, and an over- or misuse of existing antibiotics, which accelerates the evolution of resistant bacterial strains. This review focuses on innovative therapies by highlighting 19 novel antibacterials in clinical development as of June 2024. These selected compounds are characterized by new chemical scaffolds, novel molecular targets, and/or unique mechanisms of action, which render their potential to break antimicrobial resistance particularly high. A detailed analysis of the scientific foundations behind each of these compounds is provided, including their pharmacodynamic profiles, current development state, and potential for overcoming existing limitations in antibiotic therapy. By presenting this subset of chemically novel antibacterials, the review highlights the ability to innovate in antibiotic drug development to counteract bacterial resistance and improve treatment outcomes.

Römpp A., Treu A., Kokesch-Himmelreich J., Marwitz F., Dreisbach J., Aboutara N., Hillemann D., Garrelts M., Converse P.J., Tyagi S., Gerbach S., Gyr L., Lemm A., Volz J., Hölscher A., et. al.

Abstract The development of granulomas with central necrosis harboring Mycobacterium tuberculosis (Mtb) is the hallmark of human tuberculosis (TB). New anti-TB therapies need to effectively penetrate the cellular and necrotic compartments of these lesions and reach sufficient concentrations to eliminate Mtb. BTZ-043 is a novel antibiotic showing good bactericidal activity in humans in a phase IIa trial. Here, we report on lesional BTZ-043 concentrations severalfold above the minimal-inhibitory-concentration and the substantial local efficacy of BTZ-043 in interleukin-13-overexpressing mice, which mimic human TB pathology of granuloma necrosis. High-resolution MALDI imaging further reveals that BTZ-043 diffuses and accumulates in the cellular compartment, and fully penetrates the necrotic center. This is the first study that visualizes an efficient penetration and accumulation of a clinical-stage TB drug in human-like centrally necrotizing granulomas and that also determines its lesional activity. Our results most likely predict a substantial bactericidal effect of BTZ-043 at these hard-to-reach sites in TB patients.

Agnivesh P.K., Roy A., Sau S., Kumar S., Kalia N.P.

Zhong X., Wu J., Du N., Zhou S., Ma C., Xue T., Wei M., gong J., Wang B., Liu M., Wang A., Lv K., Lu Y.

Nitrobenzothiazinones (BTZs) represent a novel type of antitubercular agents targeting DprE1. Two clinical candidates BTZ043 and PBTZ169, as well as many other BTZs showed potent anti-TB activity, but they are all highly lipophilic and their poor aqueous solubility is still a serious issue need to be addressed. Here, we designed and synthesized a series of new BTZ derivatives, wherein a hydrophilic COOH or NH

Ibrahim M.A., Mahmoud D.G., Abdelrahman A.H., Abdeljawaad K.A., Mekhemer G.A., Shoeib T., El-Tayeb M.A., Sidhom P.A., Paré P.W., Hegazy M.F.

Mycobacterium tuberculosis is a lethal human pathogen, with the key flavoenzyme for catalyzing bacterial cell-wall biosynthesis, decaprenylphosphoryl-D-ribose oxidase (DprE1), considered an Achilles heal for tuberculosis (TB) progression. Inhibition of DprE1 blocks cell wall biosynthesis and is a highly promising antitubercular target. Macozinone (PBTZ169, a benzothiazinone (BTZ) derivative) is an irreversible DprE1 inhibitor that has attracted considerable attention because it exhibits an additive activity when combined with other anti-TB drugs. Herein, 754 BTZ analogs were assembled in a virtual library and evaluated against the DprE1 target using a covalent docking approach. After validation of the employed covalent docking approach, BTZ analogs were screened. Analogs with a docking score less than –9.0 kcal/mol were advanced for molecular dynamics (MD) simulations, followed by binding energy evaluations utilizing the MM-GBSA approach. Three BTZ analogs–namely, PubChem-155-924-621, PubChem-127-032-794, and PubChem-155-923-972– exhibited higher binding affinities against DprE1 compared to PBTZ169 with ΔGbinding values of –77.2, –74.3, and –65.4 kcal/mol, versus –49.8 kcal/mol, respectively. Structural and energetical analyses were performed for the identified analogs against DprE1 throughout the 100 ns MD simulations, and the results demonstrated the great stability of the identified BTZ analogs. Physicochemical and ADMET characteristics indicated the oral bioavailability of the identified BTZ analogs. The obtained in-silico results provide promising anti-TB inhibitors that are worth being subjected to in-vitro and in-vivo investigations.

Shivakumar, Dinesha P., Udayakumar D.

Sonawane K., Said R., Lele M., Chaudhari H., Hatvate N.

AbstractBenzothiazinone analogs have emerged as a promising class of compounds having potent antimycobacterial activity, particularly against Mycobacterium tuberculosis, the pathogen responsible for tuberculosis. This review highlights the development of benzothiazinone analogs as potential antitubercular agents from the beginning to the recent advancement in the past decade. These compounds have shown potent activity, including drug‐resistant strains of Mycobacterium tuberculosis. Structure–activity relationship studies and modifications have improved their efficacy. Benzothiazinone analogs have favorable pharmacokinetic profiles and show promise in preclinical studies. Challenges include addressing resistance mechanisms and ensuring safety. Their unique mode of action and promising properties make them attractive candidates for the battle against drug‐resistant tuberculosis.