Global tuberculosis drug development pipeline: the need and the reality

Design, Synthesis, and Evaluation of the Antitubercular Activity of 5-Phenyl Substituted-5, 6-dihydropyrido[2, 3-d]pyrimidine-4, 7(3H, 8H)-dione Compounds

Tuberculosis (TB) remains a major public health challenge, with research on new anti-TB drugs crucial for global TB elimination efforts. Here, we report a novel class of anti-TB agents. Especially, compounds 5b and 5j exhibited the highest activity [minimum inhibitory concentration (MIC) H37Rv: 0.16 and 0.12 μg/mL]. Chiral resolution was performed on compounds 5b and 5j; the isomers were evaluated for their activity and safety, confirming that the R-isomer 5bb and 5jb displayed significant anti-TB activity (MIC H37Rv: 0.03-0.06 μg/mL; MDR-Mtb: 0.125-0.06 μg/mL) and low hERG toxicity. Further evaluations on 5bb and 5jb demonstrated good metabolic stability, favorable kinetic parameters and oral bioavailability (F: 56.7 and 63.8%, respectively). The results of in vivo activity assessment indicate that 5bb and 5jb exhibit protective and therapeutic effects on zebrafish larvae and adult zebrafish infected with Mycobacterium marinum. Based on these results, compounds 5bb and 5jb are considered promising candidates for further in-depth studies.

Targeting decaprenylphosphoryl-β-D-ribose 2'-epimerase for Innovative Drug Development Against Mycobacterium Tuberculosis Drug-Resistant Strains

Tuberculosis (TB) remains a global health challenge with the emergence of drug-resistant Mycobacterium tuberculosis variants, necessitating innovative drug molecules. One potential target is the cell wall synthesis enzyme decaprenylphosphoryl-β-D-ribose 2'-epimerase (DprE1), crucial for virulence and survival. This study employed virtual screening of 111 Protein Data Bank (PDB) database molecules known for their inhibitory biological activity against DprE1 with known IC50 values. Six compounds, PubChem ID: 390820, 86287492, 155294899, 155522922, 162651615, and 162665075, exhibited promising attributes as drug candidates and validated against clinical trial inhibitors BTZ043, TBA-7371, PBTZ169, and OPC-167832. Concurrently, this research focused on DprE1 mutation effects using molecular dynamic simulations. Among the 10 mutations tested, C387N significantly influenced protein behavior, leading to structural alterations observed through root-mean-square deviation (RMSD), root-mean-square fluctuation (RMSF), radius of gyration (Rg), and solvent-accessible surface area (SASA) analysis. Ligand 2 (ID: 390820) emerged as a promising candidate through ligand-based pharmacophore analysis, displaying enhanced binding compared with reference inhibitors. Molecular dynamic simulations highlighted ligand 2's interaction with the C387N mutation, reducing fluctuations, augmenting hydrogen bonding, and influencing solvent accessibility. These collective findings emphasize ligand 2's efficacy, particularly against severe mutations, in enhancing protein-ligand complex stability. Integrated computational and pharmacophore methodologies offer valuable insights into drug candidates and their interactions within intricate protein environments. This research lays a strategic foundation for targeted interventions against drug-resistant TB, highlighting ligand 2's potential for advanced drug development strategies.

Tuberculosis Immunoreactivity Surveillance in Malawi (Timasamala)-A protocol for a cross-sectional Mycobacterium tuberculosis immunoreactivity survey in Blantyre, Malawi

Tuberculosis (TB) transmission and prevalence are dynamic over time, and heterogeneous within populations. Public health programmes therefore require up-to-date, accurate epidemiological data to appropriately allocate resources, target interventions, and track progress towards End TB goals. Current methods of TB surveillance often rely on case notifications, which are biased by access to healthcare, and TB disease prevalence surveys, which are highly resource-intensive, requiring many tens of thousands of people to be tested to identify high-risk groups or capture trends. Surveys of "latent TB infection", or immunoreactivity to Mycobacterium tuberculosis (Mtb), using tests such as interferon-gamma release assays (IGRAs) could provide a way to identify TB transmission hotspots, supplementing information from disease notifications, and with greater spatial and temporal resolution than is possible to achieve in disease prevalence surveys. This cross-sectional survey will investigate the prevalence of Mtb immunoreactivity amongst young children, adolescents and adults in Blantyre, Malawi, a high HIV-prevalence city in southern Africa. Through this study we will estimate the annual risk of TB infection (ARTI) in Blantyre and explore individual- and area-level risk factors for infection, as well as investigating geospatial heterogeneity of Mtb infection (and its determinants), and comparing these to the distribution of TB disease case-notifications. We will also evaluate novel diagnostics for Mtb infection (QIAreach QFT) and sampling methodologies (convenience sampling in healthcare settings and community sampling based on satellite imagery), which may increase the feasibility of measuring Mtb infection at large scale. The overall aim is to provide high-resolution epidemiological data and provide new insights into methodologies which may be used by TB programmes globally.

Polymerase Chain Reaction (PCR) Profiling of Extensively Drug-Resistant (XDR) Pathogenic Bacteria in Pulmonary Tuberculosis Patients

Introduction Pulmonary tuberculosis (TB) remains a global health concern, exacerbated by the emergence of extensively drug-resistant (XDR) strains of Mycobacterium tuberculosis. This study employs advanced molecular techniques, specifically polymerase chain reaction (PCR) profiling, to comprehensively characterize the genetic landscape of XDR pathogenic bacteria in patients diagnosed with pulmonary TB. The objective of the study is to elucidate the genes that are associated with drug resistance in pulmonary TB strains through the application of PCR and analyze specific genetic loci that contribute to the development of resistance against multiple drugs. Materials and methods A total of 116 clinical samples suspected of TB were collected from the tertiary healthcare setting of Saveetha Medical College and Hospitals for the identification of MTB, which includes sputum (n = 35), nasal swabs (n = 17), blood (n = 44), and bronchoalveolar lavage (BAL) (n = 20). The collected specimens were processed and subjected to DNA extraction. As per the protocol, reconstitution of the DNA pellet was carried out. The reconstituted DNA was stored at -20 °C for the PCR assay. From the obtained positive sample specimens, XDR pulmonary TB specimens were focused on the targeted genes, specifically the rpoB gene for rifampicin resistance, inhA, and katG gene for thepromoter region for isoniazid resistance. Results Out of a total of 116 samples obtained, 53 tested positive for pulmonary TB, indicative of a mycobacterial infection. Among these positive cases, 43 patients underwent treatment at a tertiary healthcare facility. Subsequently, a PCR assay was performed with the extracted DNA for the target genes rpoB, inhA, and katG. Specifically, 22 sputum samples exhibited gene expression for rpoB, inhA, and katG, while nine nasal swabs showed expression of the rpoB and inhA genes. Additionally, rpoB gene expression was detected in seven blood specimens, and both rpoB and inhA genes were expressed in five BAL samples. Conclusion The swift diagnosis and efficient treatment of XDR-TB can be facilitated by employing advanced and rapid molecular tests and oral medication regimens. Utilizing both newly developed and repurposed anti-TB drugs like pretomanid, bedaquiline, linezolid, and ethionamide. Adhering to these current recommendations holds promise for managing XDR-TB effectively. Nevertheless, it is significant to conduct well-designed clinical trials and studies to further evaluate the efficacy of new agents and shorter treatment regimens, thus ensuring continuous improvement in the management of this challenging condition.

Azetidines Kill Multidrug-Resistant Mycobacterium tuberculosis without Detectable Resistance by Blocking Mycolate Assembly

Tuberculosis (TB) is the leading cause of global morbidity and mortality resulting from infectious disease, with over 10.6 million new cases and 1.4 million deaths in 2021. This global emergency is exacerbated by the emergence of multidrug-resistant MDR-TB and extensively drug-resistant XDR-TB; therefore, new drugs and new drug targets are urgently required. From a whole cell phenotypic screen, a series of azetidines derivatives termed BGAz, which elicit potent bactericidal activity with MIC99 values <10 μM against drug-sensitive Mycobacterium tuberculosis and MDR-TB, were identified. These compounds demonstrate no detectable drug resistance. The mode of action and target deconvolution studies suggest that these compounds inhibit mycobacterial growth by interfering with cell envelope biogenesis, specifically late-stage mycolic acid biosynthesis. Transcriptomic analysis demonstrates that the BGAz compounds tested display a mode of action distinct from the existing mycobacterial cell wall inhibitors. In addition, the compounds tested exhibit toxicological and PK/PD profiles that pave the way for their development as antitubercular chemotherapies.

Synthesis, antimycobacterial screening, molecular docking, ADMET prediction and pharmacological evaluation on novel pyran-4-one bearing hydrazone, triazole and isoxazole moieties: Potential inhibitors of SARS CoV-2

The respiratory infection tuberculosis is caused by the bacteria Mycobacterium tuberculosis and its unrelenting spread caused millions of deaths around the world. Hence, it is needed to explore potential and less toxic anti-tubercular drugs. In the present work, we report the synthesis and antitubercular activity of four different (hydrazones 7-12, O-ethynyl oximes 19-24, triazoles 25-30, and isoxazoles 31-36) hybrids. Among these hybrids 9, 10, 33, and 34, displayed high antitubercular activity at 3.12 g/mL with >90% of inhibitions. The hybrids also showed good docking energies between -6.8 and -7.8 kcal/mol. Further, most active molecules were assayed for their DNA gyrase reduction ability towards M. tuberculosis and E.coli DNA gyrase by the DNA supercoiling and ATPase gyrase assay methods. All four hybrids showed good IC50 values comparable to that of the reference drug. In addition, the targets were also predicted as a potential binder for papain-like protease (SARS CoV-2 PLpro) by molecular docking and a good interaction result was observed. Besides, all targets were predicted for their absorption, distribution, metabolism, and excretion - toxicity (ADMET) profile and found a significant amount of ADMET and bioavailability.

Real-time recombinase-aided amplification assay for rapid amplification of the IS1081 gene of Mycobacterium tuberculosis

Mycobacterium tuberculosis (MTB), the etiological agent of tuberculosis (TB), is the leading cause of death due to a single infectious agent worldwide. Rapid and accurate diagnosis of MTB is critical for controlling TB especially in resource-limited countries, since any diagnosis delay increases the chances of transmission. Here, a real-time recombinase-aided amplification (RAA) assay targeting conserved positions in IS1081 gene of MTB, is successfully established to detect MTB. The intact workflow was completed within 30 min at 42 °C with no cross-reactivity observed for non-tuberculous mycobacteria and other clinical bacteria, and the detection limit for recombinant plasmid of MTB IS1081 was 163 copies/reaction at 95% probability, which was approximately 1.5-fold increase in analytical sensitivity for the detection of MTB, compared to conventional quantitative real-time PCR (qPCR; 244 copies/reaction). Furthermore, the result of clinical performance evaluation revealed an increased sensitivity of RAA assay relative to qPCR was majorly noted in the specimens with low bacteria loads. Our results demonstrate that the developed real-time RAA assay is a convenient, sensitive, and low-cost diagnostic tool for the rapid detection of MTB.

Respirable Clofazimine Particles Produced by Air Jet Milling Technique Are Efficacious in Treatment of BALB/c Mice with Chronic Mycobacterium tuberculosis Infection

Tuberculosis (TB) remains a major cause of morbidity and mortality, particularly in low- and middle-income countries where access to health care workers, cold-chain storage, and sterile water sources may be limited. Inhaled drug delivery is a promising alternative to systemic delivery of antimycobacterial drugs, as it enables rapid achievement of high infection-site drug concentrations. The off-patent drug clofazimine (CFZ) may be particularly suitable for this route, given its known systemic toxicities. In this study, micronized CFZ particles produced by air jet milling were assessed for shelf-stability, pharmacokinetics, and anti-TB efficacy by the oral and pulmonary routes in BALB/c mice. Intratracheal instillation of micronized CFZ particles produced several-fold higher lung concentrations after a single 30 mg/kg dose compared to delivery via oral gavage, and faster onset of bactericidal activity was observed in lungs of mice with chronic Mycobacterium tuberculosis infection compared to the oral route. Both infection status and administration route affected the multidose pharmacokinetics (PK) of micronized CFZ. Increased lung and spleen accumulation of the drug after pulmonary administration was noted in infected mice compared to naive mice, while the opposite trend was noted in the oral dosing groups. The infection-dependent PK of inhaled micronized CFZ may point to a role of macrophage trafficking in drug distribution, given the intracellular-targeting nature of the formulation. Lastly, air jet milled CFZ exhibited robustness to storage-induced chemical degradation and changes in aerosol performance, thereby indicating the suitability of the formulation for treatment of TB in regions with limited cold chain supply.

Pediatric Tuberculosis Management: A Global Challenge or Breakthrough?

Managing pediatric tuberculosis (TB) remains a public health problem requiring urgent and long-lasting solutions as TB is one of the top ten causes of ill health and death in children as well as adolescents universally. Minors are particularly susceptible to this severe illness that can be fatal post-infection or even serve as reservoirs for future disease outbreaks. However, pediatric TB is the least prioritized in most health programs and optimal infection/disease control has been quite neglected for this specialized patient category, as most scientific and clinical research efforts focus on developing novel management strategies for adults. Moreover, the ongoing coronavirus pandemic has meaningfully hindered the gains and progress achieved with TB prophylaxis, therapy, diagnosis, and global eradication goals for all affected persons of varying age bands. Thus, the opening of novel research activities and opportunities that can provide more insight and create new knowledge specifically geared towards managing TB disease in this specialized group will significantly improve their well-being and longevity.

Short-term effect of sulfur dioxide (SO2) change on the risk of tuberculosis outpatient visits in 16 cities of Anhui Province, China: the first multi-city study to explore differences in occupational patients

A growing number of biological studies suggest that exogenous sulfur dioxide (SO₂) at a certain concentration may promote human resistance to Mycobacterium tuberculosis. However, the results of most relevant studies are inconsistent, and few studies have explored the relationship between SO₂ exposure and tuberculosis risk at provincial level. In addition, occupational exposure has long been considered to have a certain impact on the human body, so for the first time, we discussed the differences between different occupations in the study on the relationship between air pollutant exposure and tuberculosis risk, and evaluated the impact of occupational exposure. This study aimed to explore the association between short-term SO₂ exposure and the risk of outpatient visits to tuberculosis in Anhui province and 16 prefecture-level cities from 2015 to 2020. We used several models for multi-stage analysis, including distributed lag nonlinear model (DLNM), Poisson generalized linear regression model, and random-effects model. The association was assessed using the 28-day cumulative lag effect RR and 95%CI for each 10-unit increase in SO₂ concentration. We divided all patients into the following six occupations: Worker, Farmer, Retired people, Children and Students, Cadre and Office clerk, and Service staff (catering, business, etc.). Sex, age, and season were analyzed by subgroup. Finally, the robustness of the multi-pollutant model was tested. At provincial level, the overall effect value of SO₂ was RR=0.8191 (95%CI: 07702~0.8712); after grouping all patients by occupation, the association found only among Farmers (RR = 0.7150, 95%CI: 0.6699-0.7632, lag 0-28 days) and Workers (RR = 0.8566, 95%CI: 0.7930-0.9930, lag 0-4 days) was still statistically significant. Estimates for individual cities and using random-effects models to estimate average associations showed that SO₂ exposure was associated with a reduced risk of outpatient TB visits in 14 municipalities, which remained significant when aggregated (RR = 0.9030, 95%CI: 0.8730-0.9340). Analysis of patients grouped by occupation in each municipality showed that statistical significance was again observed only in the Farmer (RR = 0.8880, 95%CI: 0.8610-0.9160) and Worker (RR = 0.8250, 95%CI: 0.7290-0.9340) groups. Stratified analysis of age, sex, and season showed that the effect of SO₂ exposure was greater for middle-aged people (18-64 years old) and males, and less for seasonal changes. In summary, we found that exposure to SO₂ reduces the risk of outpatient visits to tuberculosis, with farmers and workers more susceptible to SO₂. Gender and age had a greater impact on the risk of TB outpatient visits than seasonal variations.

Patient and health system level barriers to and facilitators for tuberculosis treatment initiation in Uganda: a qualitative study

BACKGROUND

The WHO END TB strategy targets to place at least 90% of all patients diagnosed with Tuberculosis (TB) on appropriate treatment. In Uganda, approximately 20% of patients diagnosed with TB are not initiated on TB treatment. We sought to identify the patient and health system level barriers to and facilitators for TB treatment initiation in Uganda.

METHODS

We conducted the study at ten public health facilities (three primary care, four district and three tertiary referral hospitals). We carried out in-depth interviews with patients diagnosed with TB and key informant interviews with health managers. In addition, we held focus group discussions with healthcare workers involved in TB care. Data collection and thematic analysis of transcripts was informed by the Capability, Opportunity, Motivation and Behavior (COM-B) model. We identified relevant intervention functions using the Behavior Change Wheel.

RESULTS

We interviewed 79 respondents (31 patients, 10 health managers and 38 healthcare workers). Common barriers at the health facility level included; lack of knowledge about the proportion of patients not initiated on TB treatment (psychological capability); difficulty accessing sputum results from the laboratory as well as difficulty tracing patients due to inadequate recording of patient addresses (physical opportunity). At the patient level, notable barriers included long turnaround time for sputum results and lack of transport funds to return to health facilities (physical opportunity); limited TB knowledge (psychological capability) and stigma (social opportunity). The most important facilitators identified were quick access to sputum test results either on the date of first visit (same-day diagnosis) or on the date of first return and availability of TB treatment (physical opportunity). We identified education, restructuring of the service environment to improve sputum results turnaround time and enablement to improve communication of test results as relevant intervention functions to alleviate these barriers to and enhance facilitators for TB treatment initiation.

CONCLUSION

We found that barriers to treatment initiation existed at both the patient and health facility-level across all levels of the (Capability, Opportunity and Motivation) model. The intervention functions identified here should be tested for feasibility.

A novel class of antimicrobial drugs selectively targets a Mycobacterium tuberculosis PE-PGRS protein

The continued spread of drug-resistant tuberculosis is one of the most pressing and complex challenges facing tuberculosis management worldwide. Therefore, developing a new class of drugs is necessary and urgently needed to cope with the increasing threat of drug-resistant tuberculosis. This study aims to discover a potential new class of tuberculosis drug candidates different from existing tuberculosis drugs. By screening a library of compounds, methyl (S)-1-((3-alkoxy-6,7-dimethoxyphenanthren-9-yl)methyl)-5-oxopyrrolidine-2-carboxylate (PP) derivatives with antitubercular activity were discovered. MIC ranges for PP1S, PP2S, and PP3S against clinically isolated drug-resistant Mycobacterium tuberculosis strains were 0.78 to 3.13, 0.19 to 1.56, and 0.78 to 6.25 μg/ml, respectively. PPs demonstrated antitubercular activities in macrophage and tuberculosis mouse models, showing no detectable toxicity in all assays tested. PPs specifically inhibited M. tuberculosis without significantly changing the intestinal microbiome in mice. Mutants selected in vitro suggest that the drug targets the PE-PGRS57, which has been found only in the genomes of the M. tuberculosis complex, highlighting the specificity and safety potency of this compound. As PPs show an excellent safety profile and highly selective toxicity specific to M. tuberculosis, PPs are considered a promising new candidate for the treatment of drug-resistant tuberculosis while maintaining microbiome homeostasis.

Acetylene containing 2-(2-hydrazinyl)thiazole derivatives: design, synthesis, and in vitro and in silico evaluation of antimycobacterial activity against Mycobacterium tuberculosis

Mycobacterium tuberculosis resistance to commercially available drugs is increasing day by day. To address this issue, various strategies were planned and are being implemented. However, there is a need for new drugs and rapid diagnostic methods. For this endeavour, in this paper, we present the synthesis of acetylene containing 2-(2-hydrazinyl) thiazole derivatives and in vitro evaluation against the H37Rv strain of Mycobacterium tuberculosis. Among the developed 26 acetylene containing 2-(2-hydrazinyl) thiazole derivatives, eight compounds inhibited the growth of Mycobacterium tuberculosis with MIC values ranging from 100 μg ml-1 to 50 μg ml-1. The parent acetylene containing thiosemicarbazones showed promising antimycobacterial activity by inhibiting up to 75% of the Mycobacterium at 50 μg ml-1. In addition, in silico studies were employed to understand the binding mode of all the novel acetylene-containing derivatives against the KasA protein of the Mycobacterium. Interestingly, the KasA protein interactions with the compounds were similar to the interactions of KasA protein with thiolactomycin and rifampicin. Cytotoxicity study results indicate that the compounds tested are non-toxic to human embryonic kidney cells.

Feasibility of a multifaceted intervention to improve treatment initiation among patients diagnosed with TB using Xpert MTB/RIF testing in Uganda

BACKGROUND

One in five patients diagnosed with TB in Uganda are not initiated on TB treatment within two weeks of diagnosis. We evaluated a multifaceted intervention for improving TB treatment initiation among patients diagnosed with TB using Xpert® MTB/RIF testing in Uganda.

METHODS

This was a pre-post interventional study at one tertiary referral hospital. The intervention was informed by the COM-B model and included; i) medical education sessions to improve healthcare worker knowledge about the magnitude and consequences of pretreatment loss to follow-up; ii) modified laboratory request forms to improve recording of patient contact information; and iii) re-designed workflow processes to improve timeliness of sputum testing and results dissemination. TB diagnostic process and outcome data were collected and compared from the period before (June to August 2019) and after (October to December 2019) intervention initiation.

RESULTS

In September 2019, four CME sessions were held at the hospital and were attended by 58 healthcare workers. During the study period, 1242 patients were evaluated by Xpert® MTB/RIF testing at the hospital (679 pre and 557 post intervention). Median turnaround time for sputum test results improved from 12 hours (IQR 4-46) in the pre-intervention period to 4 hours (IQR 3-6) in the post-intervention period. The proportion of patients started on treatment within two weeks of diagnosis improved from 59% (40/68) to 89% (49/55) (difference 30%, 95% CI 14%-43%, p<0.01) while the proportion of patients receiving a same-day diagnosis increased from 7.4% (5/68) to 25% (14/55) (difference 17.6%, 95% CI 3.9%-32.7%, p<0.01).

CONCLUSION

The multifaceted intervention was feasible and resulted in a higher proportion of patients initiating TB treatment within two weeks of diagnosis.

Role of Epistasis in Amikacin, Kanamycin, Bedaquiline, and Clofazimine Resistance in Mycobacterium tuberculosis Complex

Antibiotic resistance among bacterial pathogens poses a major global health threat. Mycobacterium tuberculosis complex (MTBC) is estimated to have the highest resistance rates of any pathogen globally. Given the low growth rate and the need for a biosafety level 3 laboratory, the only realistic avenue to scale up drug susceptibility testing (DST) for this pathogen is to rely on genotypic techniques. This raises the fundamental question of whether a mutation is a reliable surrogate for phenotypic resistance or whether the presence of a second mutation can completely counteract its effect, resulting in major diagnostic errors (i.e., systematic false resistance results). To date, such epistatic interactions have only been reported for streptomycin that is now rarely used. By analyzing more than 31,000 MTBC genomes, we demonstrated that the eis C-14T promoter mutation, which is interrogated by several genotypic DST assays endorsed by the World Health Organization, cannot confer resistance to amikacin and kanamycin if it coincides with loss-of-function (LoF) mutations in the coding region of eis. To our knowledge, this represents the first definitive example of antibiotic reversion in MTBC. Moreover, we raise the possibility that mmpR (Rv0678) mutations are not valid markers of resistance to bedaquiline and clofazimine if these coincide with an LoF mutation in the efflux pump encoded by mmpS5 (Rv0677c) and mmpL5 (Rv0676c).

Identification and validation of potent Mycobacterial proteasome inhibitor from Enamine library

As a consequence of present status of tuberculosis (TB) it is the obligation to develop novel targets and potential drugs so that rate of drug resistant TB can be declined. Mycobacterium proteasome is considered to be significant target for the purpose of drug designing as it is responsible for resisting the effect of NO (nitric oxide) immune system defence mechanism against the bacterial cells. Small compounds library from Enamine database has already been tested using virtual screening and molecular docking studies. Further a reanalysis with two picked out significant compounds Z1020863610, Z106766984 was carried out using molecular dynamic simulation studies and in vitro validations (in vitro susceptibility assay, enzyme inhibition assay and MTT assay). In silico outcome that two inhibiters were interacting at the active site pocket of receptor with high stability, was found to be very consistent with in vitro results. So it was conferred that compounds (Z1020863610, Z106766984) are potential lead for future process of drug development (in vivo testing and clinical trials).Communicated by Ramaswamy H. Sarma.

Access to experimental medicines for TB: ethical and human rights considerations

The revised edition of the WHO's Ethics Guidance for the Implementation of the TB Strategy has added a new chapter on compassionate use (CU) and expanded access (EA) to TB drugs. CU and EA programmes authorise access to drugs that have not yet received marketing approval outside of clinical trials. They are aimed at allowing researchers access to investigational drugs in the absence of complete evidence of efficacy and safety to patients with multidrug-resistant (MDR) or rifampicin-resistant TB (RR-TB) when no other treatment options are available. In doing so, the guidance acknowledged the urgent necessity to offer these patients all possible treatments in respect of considerations of justice, human rights, human dignity, autonomy of the individual and protection of the community. Regulators are in general willing to accept a higher level of uncertainty in the risk-benefit assessment of medicines for life-threatening diseases when there is an unmet medical need. This attests to a paradigm change, which this article argues should also apply to allow for effective access to experimental TB medicines. Furthermore, in this article, we analyse the challenges connected to the establishment of a secure and effective regime of access to experimental drugs in the context of MDR/RR-TB as well as the ethical principles and human rights arguments in favour of the development of such programmes.

Rifampin-resistant/multidrug-resistant Tuberculosis in Alberta, Canada: Epidemiology and treatment outcomes in a low-incidence setting

Treatment of rifampin-monoresistant/multidrug-resistant Tuberculosis (RR/MDR-TB) requires long treatment courses, complicated by frequent adverse events and low success rates. Incidence of RR/MDR-TB in Canada is low and treatment practices are variable due to the infrequent experience and challenges with drug access. We undertook a retrospective cohort study of all RR/MDR-TB cases in Alberta, Canada from 2007-2017 to explore the epidemiology and outcomes in our low incidence setting. We performed a descriptive analysis of the epidemiology, treatment regimens and associated outcomes, calculating differences in continuous and discrete variables using Student's t and Chi-squared tests, respectively. We identified 24 patients with RR/MDR-TB. All patients were foreign-born with the median time to presentation after immigration being 3 years. Prior treatment was reported in 46%. Treatment was individualized. All patients achieved sputum culture conversion within two months of treatment initiation. The median treatment duration after culture conversion was 18 months (IQR: 15-19). The mean number of drugs utilized during the intensive phase was 4.3 (SD: 0.8) and during the continuation phase was 3.3 (SD: 0.9) and the mean adherence to medications was 95%. Six patients completed national guideline-concordant therapy, with many patients developing adverse events (79%). Treatment success (defined as completion of prescribed therapy or cure) was achieved in 23/24 patients and no acquired drug resistance or relapse was detected over 1.8 years of median follow-up. Many cases were captured upon immigration assessment, representing important prevention of community spread. Despite high rates of adverse events and short treatment compared to international guidelines, success in our cohort was very high at 96%. This is likely due to individualization of therapy, frequent use of medications with high effectiveness, intensive treatment support, and early sputum conversion seen in our cohort. There should be ongoing exploration of treatment shortening with well-tolerated, efficacious oral agents to help patients achieve treatment completion.

Benzofuroxan Derivatives as Potent Agents against Multidrug-Resistant Mycobacterium tuberculosis

Tuberculosis (TB) is currently the leading cause of death related to infectious diseases worldwide, as reported by the World Health Organization. Moreover, the increasing number of multidrug-resistant tuberculosis (MDR-TB) cases has alarmed health agencies, warranting extensive efforts to discover novel drugs that are effective and also safe. In this study, 23 new compounds were synthesized and evaluated in vitro against the drug-resistant strains of M. tuberculosis. The compound 6-((3-fluoro-4-thiomorpholinophenyl)carbamoyl)benzo[c][1,2,5]oxadiazole 1-N-oxide (5 b) was particularly remarkable in this regard as it demonstrated MIC₉₀ values below 0.28 μM against all the MDR strains evaluated, thus suggesting that this compound might have a different mechanism of action. Benzofuroxans are an attractive new class of anti-TB agents, exemplified by compound 5 b, with excellent potency against the replicating and drug-resistant strains of M. tuberculosis.

Pulmonary Targeting of Inhalable Moxifloxacin Microspheres for Effective Management of Tuberculosis

In the present study, the objective was to attain a localized lung delivery of an anti-tubercular fluoroquinolone, moxifloxacin (MXF), targeting the alveolar macrophages through a non-invasive pulmonary route using inhalable microspheres as a dry powder inhaler approach. MXF-loaded poly (lactic-co-glycolic acid) (PLGA) microspheres (MXF-PLGA-MSs) were fabricated by solvent evaporation technique and optimized by using a central composite statistical design. The morphology and particle size, as well as the flowability of the optimized microspheres, were characterized. In addition, the aerosolization performance of the optimized formula was inspected using an Andersen cascade impactor. Furthermore, in vivo fate following intrapulmonary administration of the optimized formula was evaluated. The optimized MXF-PLGA-MSs were spherical in shape with a particle size of 3.16 µm, drug loading of 21.98% and entrapment efficiency of 78.0%. The optimized formula showed a mass median aerodynamic diameter (MMAD) of 2.85 ± 1.04 µm with a favorable fine particle fraction of 72.77 ± 1.73%, suggesting that the powders were suitable for inhalation. Most importantly, in vivo studies revealed that optimized MXF-PLGA-MSs preferentially accumulated in lung tissue as manifested by a two-fold increase in the area under the curve AUC_0–24h, compared to plain drug. In addition, optimized MXF-PLGA-MS sustained drug residence in the lung for up to 24 h following inhalation, compared to plain drug. In conclusion, inhalable microspheres of MXF could be a promising therapeutic approach that might aid in the effective eradiation of tuberculosis along with improving patient adherence to the treatment.

Bayesian Spatial Survival Analysis of Duration to Cure among New Smear-Positive Pulmonary Tuberculosis (PTB) Patients in Iran, during 2011-2018

Mycobacterium tuberculosis is the causative agent of tuberculosis (TB), and pulmonary TB is the most prevalent form of the disease worldwide. One of the most concrete actions to ensure an effective TB control program is monitoring TB treatment outcomes, particularly duration to cure; but, there is no strong evidence in this respect. Thus, the primary aim of this study was to examine the possible spatial variations of duration to cure and its associated factors in Iran using the Bayesian spatial survival model. All new smear-positive PTB patients have diagnosed from March 2011 to March 2018 were included in the study. Out of 34,744 patients, 27,752 (79.90%) patients cured and 6992 (20.10%) cases were censored. For inferential purposes, the Markov chain Monte Carlo algorithms are applied in a Bayesian framework. According to the Bayesian estimates of the regression parameters in the proposed model, a Bayesian spatial log-logistic model, the variables gender (male vs. female, TR = 1.09), altitude (>750 m vs. ≤750 m, TR = 1.05), bacilli density in initial smear (3+ and 2+ vs. 1–9 Basil & 1+, TR = 1.09 and TR = 1.02, respectively), delayed diagnosis (>3 months vs. <1 month, TR = 1.02), nationality (Iranian vs. other, TR = 1.02), and location (urban vs. rural, TR = 1.02) had a significant influence on prolonging the duration to cure. Indeed, pretreatment weight (TR = 0.99) was substantially associated with shorter duration to cure. In summary, the spatial log-logistic model with convolution prior represented a better performance to analyze the duration to cure of PTB patients. Also, our results provide valuable information on critical determinants of duration to cure. Prolonged duration to cure was observed in provinces with low TB incidence and high average altitude as well. Accordingly, it is essential to pay a special attention to such provinces and monitor them carefully to reduce the duration to cure while maintaining a focus on high-risk provinces in terms of TB prevalence.

Synthesis and activity of BNF15 against drug-resistant Mycobacterium tuberculosis

Aim: Tuberculosis is the leading cause of mortality among infectious diseases worldwide. Finding a new competent anti tubercular therapy is essential. Materials & methods: We screened thousands of compounds and evaluated their efficacy against Mycobacterium tuberculosis. Results: Initially, 2-nitronaphtho[2,3-b]benzofuran-6,11-dione was active against M. tuberculosis. Next, among 15 newly synthesized derivatives, BNF15 showed promising effect against all drug-sensitive and drug-resistant M. tuberculosis (MIC: 0.02-0.78 μg/ml). BNF15 effectively killed intracellular M. tuberculosis and nontuberculous mycobacteria. BNF15 exhibited a prolonged post antibiotic effect superior to isoniazid, streptomycin, and ethambutol and synergistic interaction with rifampicin. In acute oral toxicity test, BNF15 did not show toxic effect at a concentration up to 2000 mg/kg. Conclusion: These results highlight the perspective of BNF15 to treat drug-resistant M. tuberculosis.

Loperamide exerts a direct bactericidal effect against M. tuberculosis, M. bovis, M. terrae and M. smegmatis

Tuberculosis (TB) is caused by Mycobacterium tuberculosis. TB is highly prevalent, characterized by the constant occurrence of drug-resistant cases, and confounded by the incidence of respiratory disease caused by non-tuberculous mycobacteria (NTB). Expanding the spectrum of drugs for the treatment of TB is indispensable. Loperamide, an antidiarrhoeal drug, enhances immune-driven antimycobacterial activity, and we aimed to evaluate its bactericidal activity against M. tuberculosis, Mycobacterium bovis BCG, Mycobacterium terrae and Mycobacterium smegmatis. Loperamide exhibited an inhibitory effect against all mycobacterial species tested, with MICs of 100 and 150 μg ml^-1 . Thus, loperamide is a mycobactericidal drug with potential as adjunctive therapy for TB and NTB infections.

Effect of interval between food intake and drug administration at fasting condition on the plasma concentrations of first-line anti-tuberculosis drugs in Chinese population

We aimed to investigate the effect of interval between food intake and drug administration at fasting condition on the plasma concentrations of first-line anti- tuberculosis (TB) drugs in Chinese population. Newly diagnosed TB patients administered the anti-TB drugs under fasting conditions orally, and then had prepared breakfast at 30 minutes and 120 min after dosing, respectively. Blood sampling was also performed 120  minutes after dosing for the detection of Cmax purpose. Overall, twenty-five participants were included in our analysis. The Cmaxs of 30  minutes interval and 120  minutes interval were 21.8 ± 2.0 and 19.2 ± 2.0 μg/mL for rifampin, 1.6 ± 0.2 and 2.1 ± 0.2 μg/mL for isoniazid (INH), 1.5 ± 0.1and 1.5 ± 0.2 μg/mL for ethambutol (EMB), and 49.2 ± 3.7 and 41.5 ± 3.9 μg/mL for pyrazinamide, respectively. Statistical analysis revealed that there was no statistical difference between 2 groups. Additionally, 88.0% and 72.0% of the 25 participants at 2-hour interval group had peak concentrations less than the lower limit of the reference range for INH and EMB, respectively. The Cmaxs of INH were 0.9 ± 0.4 μg/ml for rapid acetylator, which was significantly lower than those of intermediate (1.4 ± 1.0 μg/mL), and slow acetylator (2.5 ± 1.0 μg/mL), respectively (P < .01). In conclusion, our data demonstrate that early food intake at 30 minutes after drug administration had no significant influence on the plasma concentrations. In addition, a high proportion of patients receiving first-line anti-TB regimen fail to achieve the expected plasma drug ranges of INH and EMB (P > .05).

Structure and Function of L,D- and D,D-Transpeptidase Family Enzymes from Mycobacterium tuberculosis

Peptidoglycan, the exoskeleton of bacterial cell and an essential barrier that protects the cell, is synthesized by a pathway where the final steps are catalysed by transpeptidases. Knowledge of the structure and function of these vital enzymes that generate this macromolecule in M. tuberculosis could facilitate the development of potent lead compounds against tuberculosis. This review summarizes the experimental and computational studies to date on these aspects of transpeptidases in M. tuberculosis that have been identified and validated. The reported structures of L,D- and D,D-transpeptidases, as well as their functionalities, are reviewed and the proposed enzymatic mechanisms for L,D-transpeptidases are summarized. In addition, we provide bioactivities of known tuberculosis drugs against these enzymes based on both experimental and computational approaches. Advancing knowledge about these prominent targets supports the development of new drugs with novel inhibition mechanisms overcoming the current need for new drugs against tuberculosis.

A systematic assessment of mycobacterial F1 -ATPase subunit ε's role in latent ATPase hydrolysis

In contrast to most bacteria, the mycobacterial F₁ F_O -ATP synthase (α₃ :β₃ :γ:δ:ε:a:b:b':c₉ ) does not perform ATP hydrolysis-driven proton translocation. Although subunits α, γ and ε of the catalytic F₁ -ATPase component α₃ :β₃ :γ:ε have all been implicated in the suppression of the enzyme's ATPase activity, the mechanism remains poorly defined. Here, we brought the central stalk subunit ε into focus by generating the recombinant Mycobacterium smegmatis F₁ -ATPase (MsF₁ -ATPase), whose 3D low-resolution structure is presented, and its ε-free form MsF₁ αβγ, which showed an eightfold ATP hydrolysis increase and provided a defined system to systematically study the segments of mycobacterial ε's suppression of ATPase activity. Deletion of four amino acids at ε's N terminus, mutant MsF₁ αβγε_Δ2-5 , revealed similar ATP hydrolysis as MsF₁ αβγ. Together with biochemical and NMR solution studies of a single, double, triple and quadruple N-terminal ε-mutants, the importance of the first N-terminal residues of mycobacterial ε in structure stability and latency is described. Engineering ε's C-terminal mutant MsF₁ αβγε_Δ121 and MsF₁ αβγε_Δ103-121 with deletion of the C-terminal residue D121 and the two C-terminal ɑ-helices, respectively, revealed the requirement of the very C terminus for communication with the catalytic α₃ β₃ -headpiece and its function in ATP hydrolysis inhibition. Finally, we applied the tools developed during the study for an in silico screen to identify a novel subunit ε-targeting F-ATP synthase inhibitor.

Some New Hydrazone Derivatives Bearing the 1,2,4-Triazole Moiety as Potential Antimycobacterial Agents

Objectives

The aim of this study was to synthesize, characterize, and screen some new 1-(4-((2-(4-substitutedphenyl)hydrazono)methyl)phenyl)-1H-1,2,4-triazole derivatives for their antimycobacterial activities.

Materials and Methods

The target compounds (2a-h) were gained by condensation of 4-(1H-1,2,4-triazol-1-yl)benzaldehyde with appropriate phenylhydrazines. Their structures were elucidated by IR, ¹H-NMR, and mass spectrometry. The antimycobacterial activities of the compounds were determined in vitro against Mycobacterium tuberculosis H37Rv.

Results

The biological assay results showed that the methylsulfonyl-substituted derivative 2f displayed the highest antimycobacterial activity in this series.

Conclusion

Although the methylsulfonyl-substituted derivative exhibited significant antimycobacterial activity, none of the synthesized compounds was as effective as isoniazid, rifampin, ethambutol, and ciprofloxacin against M. tuberculosis.

Bis-(imidazole/benzimidazole)-pyridine derivatives: synthesis, structure and antimycobacterial activity

Aim:

Over the last decades, few significant achievements have been made in tuberculosis (TB) therapy. As a result, there is an urgent need for new anti-TB drugs.

Results:

Two new classes of bis-(imidazole/benzimidazole)-pyridine derivatives were designed, synthesized and evaluated for their antimycobacterial activity.

Conclusion:

The synthesis is efficient and straightforward, involving only two successive N-alkylations. The anti-TB assay reveal that our compounds have an excellent anti-TB activity against both replicating and nonreplicating Mtb, are not cytotoxic, exhibited a very good intracellular activity and are active against drug-resistant Mtb strains, some compounds have a bactericidal mechanism. The absorption, distribution, metabolism, excretion and toxicity studies performed for one compound are promising, indicating that it is a good candidate for a future drug.

Shortened treatment regimens versus the standard regimen for drug-sensitive pulmonary tuberculosis

BACKGROUND

Tuberculosis causes more deaths than any other infectious disease worldwide, with pulmonary tuberculosis being the most common form. Standard first-line treatment for drug-sensitive pulmonary tuberculosis for six months comprises isoniazid, rifampicin, pyrazinamide, and ethambutol (HRZE) for two months, followed by HRE (in areas of high TB drug resistance) or HR, given over a four-month continuation phase. Many people do not complete this full course. Shortened treatment regimens that are equally effective and safe could improve treatment success.

OBJECTIVES

To evaluate the efficacy and safety of shortened treatment regimens versus the standard six-month treatment regimen for individuals with drug-sensitive pulmonary tuberculosis.

SEARCH METHODS

We searched the following databases up to 10 July 2019: the Cochrane Infectious Diseases Group Specialized Register; the Central Register of Controlled Trials (CENTRAL), in the Cochrane Library; MEDLINE (PubMed); Embase; the Latin American Caribbean Health Sciences Literature (LILACS); Science Citation Index-Expanded; Indian Medlars Center; and the South Asian Database of Controlled Clinical Trials. We also searched the World Health Organization (WHO) International Clinical Trials Registry Platform, ClinicalTrials.gov, the Clinical Trials Unit of the International Union Against Tuberculosis and Lung Disease, the UK Medical Research Council Clinical Trials Unit, and the Clinical Trials Registry India for ongoing trials. We checked the reference lists of identified articles to find additional relevant studies.

SELECTION CRITERIA

We searched for randomized controlled trials (RCTs) or quasi-RCTs that compared shorter-duration regimens (less than six months) versus the standard six-month regimen for people of all ages, irrespective of HIV status, who were newly diagnosed with pulmonary tuberculosis by positive sputum culture or GeneXpert, and with presumed or proven drug-sensitive tuberculosis. The primary outcome of interest was relapse within two years of completion of anti-tuberculosis treatment (ATT).

DATA COLLECTION AND ANALYSIS

Two review authors independently selected trials, extracted data, and assessed risk of bias for the included trials. For dichotomous outcomes, we used risk ratios (RRs) with 95% confidence intervals (CIs). When appropriate, we pooled data from the included trials in meta-analyses. We assessed the certainty of evidence using the GRADE approach.

MAIN RESULTS

We included five randomized trials that compared fluoroquinolone-containing four-month ATT regimens versus standard six-month ATT regimens and recruited 5825 adults with newly diagnosed drug-sensitive pulmonary tuberculosis from 14 countries with high tuberculosis transmission in Asia, Africa, and Latin Ameria. Three were multi-country trials that included a total of 572 HIV-positive people. These trials excluded children, pregnant or lactating women, people with serious comorbid conditions, and those with diabetes mellitus. Four trials had multiple treatment arms. Moxifloxacin replaced ethambutol in standard four-month, daily or thrice-weekly ATT regimens in two trials; moxifloxacin replaced isoniazid in four-month ATT regimens in two trials, was given daily in one trial, and was given with rifapentine instead of rifampicin daily for two months and twice weekly for two months in one trial. Moxifloxacin was added to standard ATT drugs for three to four months in one ongoing trial that reported interim results. Gatifloxacin replaced ethambutol in standard ATT regimens given daily or thrice weekly for four months in two trials. Follow-up ranged from 12 months to 24 months after treatment completion for the majority of participants. Moxifloxacin-containing four-month ATT regimens Moxifloxacin-containing four-month ATT regimens that replaced ethambutol or isoniazid probably increased the proportions who experienced relapse after successful treatment compared to standard ATT regimens (RR 3.56, 95% CI 2.37 to 5.37; 2265 participants, 3 trials; moderate-certainty evidence). For death from any cause, there was probably little or no difference between the two regimens (2760 participants, 3 trials; moderate-certainty evidence). Treatment failure was rare, and there was probably little or no difference in proportions with treatment failure between ATT regimens (2282 participants, 3 trials; moderate-certainty evidence). None of the participants given moxifloxacin-containing regimens developed resistance to rifampicin, and these regimens may not increase the risk of acquired resistance (2282 participants, 3 trials; low-certainty evidence). Severe adverse events were probably little or no different with moxifloxacin-containing four-month regimens that replaced ethambutol or isoniazid, and with three- to four-month regimens that augmented standard ATT with moxifloxacin, when compared to standard six-month ATT regimens (3548 participants, 4 trials; moderate-certainty evidence). Gatifloxacin-containing four-month ATT regimens Gatifloxacin-containing four-month ATT regimens that replaced ethambutol probably increased relapse compared to standard six-month ATT regimens in adults with drug-sensitive pulmonary tuberculosis (RR 2.11, 95% CI 1.56 to 2.84; 1633 participants, 2 trials; moderate-certainty evidence). The four-month regimen probably made little or no difference in death compared to the six-month regimen (1886 participants, 2 trials; moderate-certainty evidence). Treatment failure was uncommon and was probably little or no different between the four-month and six-month regimens (1657 participants, 2 trials; moderate-certainty evidence). Acquired resistance to isoniazid or rifampicin was not detected in those given the gatifloxacin-containing shortened ATT regimen, but we are uncertain whether acquired drug resistance is any different in the four- and six-month regimens (429 participants, 1 trial; very low-certainty evidence). Serious adverse events were probably no different with either regimen (1993 participants, 2 trials; moderate-certainty evidence).

AUTHORS' CONCLUSIONS

Evidence to date does not support the use of shortened ATT regimens in adults with newly diagnosed drug-sensitive pulmonary tuberculosis. Four-month ATT regimens that replace ethambutol with moxifloxacin or gatifloxacin, or isoniazid with moxifloxacin, increase relapse substantially compared to standard six-month ATT regimens, although treatment success and serious adverse events are little or no different. The results of six large ongoing trials will help inform decisions on whether shortened ATT regimens can replace standard six-month ATT regimens. 9 December 2019 Up to date All studies incorporated from most recent search All eligible published studies found in the last search (10 Jul, 2019) were included.

AI‐Enabled Parabolic Response Surface Approach Identifies Ultra Short‐Course Near‐Universal TB Drug Regimens

Tuberculosis (TB) is a major health problem that causes more deaths worldwide than any other single infectious disease. Current multidrug therapy for tuberculosis is exceedingly lengthy, leading to poor drug adherence, and consequently the emergence of drug resistance. Hence, much more rapid treatments are needed. Experimentally identifying the most synergistic drug combinations among available drugs is complicated by the astronomical number of possible drug-dose combinations. This problem is dealt with by the use of an artificial-intelligence-enabled parabolic response surface platform in conjunction with an in vitro Mycobacterium tuberculosis–infected macrophage cell culture assay amenable to high-throughput screening. This strategy allows rapid identification of the most effective drug-dose combinations by testing only a small fraction of the total drug-dose efficacy response surface. The same platform is then used to optimize the in vivo doses of each drug in the most potent regimens. Thus, regimens are identified that are dramatically more effective than the Standard Regimen in treating TB in a mouse model—a model broadly predictive of drug efficacy in humans. The most effective regimens reported herein shorten the duration of treatment required to achieve relapse-free cure by 80% and are suitable for treating both drug-sensitive and most drug-resistant cases of tuberculosis.

Mycobacterial tuberculosis Enzyme Targets and their Inhibitors

Tuberculosis (TB) still continues to be a major killer disease worldwide. Unlike other bacteria Mycobacterium tuberculosis (Mtb) has the ability to become dormant within the host and to develop resistance. Hence efforts are being made to overcome these problems by searching for new antitubercular agents which may be useful in the treatment of multidrug-(MDR) and extensively drugresistant (XDR) M. tuberculosis and shortening the treatment time. The recent introduction of bedaquiline to treat MDR-TB and XDR-TB may improve the status of TB treatment. The target enzymes in anti-TB drug discovery programs play a key role, hence efforts have been made to review the work on molecules including antiTB drugs acting on different enzyme targets including ATP synthase, the target for bedaquiline. Literature searches have been carried out to find the different chemical molecules including drugs and their molecular targets responsible for their antitubercular activities in recent years. This review provides an overview of the chemical structures with their antitubercular activities and enzyme targets like InhA, ATP synthase, Lip Y, transmembrane transport protein large (MmpL3), and decaprenylphospho-β-D-ribofuranose 2-oxidase, (DprE1). The major focus has been on the new target ATP synthase. Such an attempt may be useful in designing new chemical entities (NCEs) for specific and multi-drug targeting against Mtb.

Artificial intelligence enabled parabolic response surface platform identifies ultra-rapid near-universal TB drug treatment regimens comprising approved drugs

Background

Shorter, 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 findings

We 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.

Conclusions

We 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.

Design, synthesis, and antitubercular activity of 3-amidophenols with 5-heteroatomic substitutions

A series of novel 3-amidophenols with 5-heteroatomic substitutions were designed and synthesized. Several compounds showed potent antitubercular activity against Mycobacterium tuberculosis H37Ra (MIC = 0.25-5 μg/mL). Compounds 12j and 14i also displayed good inhibitory activity against M. tuberculosis H37Rv and two clinically isolated multidrug-resistant M. tuberculosis strains (MIC = 0.39-3.12 μg/mL). The privileged compound 14i showed certain oral efficacy on a mouse infection model. The compounds are non-cytotoxic against L-O2 hepatocytes and RAW264.7 macrophagocytes. They did not exert inhibitory activity against representative Gram-positive and Gram-negative bacteria.

Triple oral beta-lactam containing therapy for Buruli ulcer treatment shortening

The potential use of clinically approved beta-lactams for Buruli ulcer (BU) treatment was investigated with representative classes analyzed in vitro for activity against Mycobacterium ulcerans. Beta-lactams tested were effective alone and displayed a strong synergistic profile in combination with antibiotics currently used to treat BU, i.e. rifampicin and clarithromycin; this activity was further potentiated in the presence of the beta-lactamase inhibitor clavulanate. In addition, quadruple combinations of rifampicin, clarithromycin, clavulanate and beta-lactams resulted in multiplicative reductions in their minimal inhibitory concentration (MIC) values. The MIC of amoxicillin against a panel of clinical isolates decreased more than 200-fold within this quadruple combination. Amoxicillin/clavulanate formulations are readily available with clinical pedigree, low toxicity, and orally and pediatric available; thus, supporting its potential inclusion as a new anti-BU drug in current combination therapies.

Buruli ulcer (BU) is a chronic debilitating disease of the skin and soft tissue, mainly affecting children and young adults in tropical regions. Before 2004, the only treatment option was surgery; a major breakthrough was the discovery that BU could be cured in most cases with a standard treatment that involved 8 weeks of combination therapy with rifampicin and streptomycin. However, the use of streptomycin is often associated with severe side effects such as ototoxicity, or nephrotoxicity. More recently, a clinical trial demonstrated equipotency of replacing the injectable streptomycin by the clarithromycin, which is orally available and associated with fewer side effects. BU treatment is now moving toward a full orally available treatment of clarithromycin-rifampicin. Although effective and mostly well tolerated, this new treatment is still associated with side effects and only moxifloxacin is additionally recommended by WHO for BU therapy. New drugs are thus needed to increase the number of available treatments, reduce side effects, and improve efficacy with treatments shorter than 8 weeks. In this work, we describe for the first time the potential inclusion of beta-lactams in BU therapy. More specifically, we propose the use of amoxicillin/clavulanate since it is oral, suitable for the treatment of children, and readily available with a long track record of clinical pedigree. Its inclusion in a triple oral therapy complementing current combinatorial rifampicin-clarithromycin treatment has the potential to counteract resistance development and to reduce length of treatment and time to cure.

Strategies towards the synthesis of anti-tuberculosis drugs

In this report, we reviewed the strategies towards the synthesis of anti-tuberculosis drugs. They include semisynthetic approaches, resolution based strategies, microbial transformations, solid phase synthesis, and asymmetric synthesis.

Application of genetically encoded redox biosensors to measure dynamic changes in the glutathione, bacillithiol and mycothiol redox potentials in pathogenic bacteria

Gram-negative bacteria utilize glutathione (GSH) as their major LMW thiol. However, most Gram-positive bacteria do not encode enzymes for GSH biosynthesis and produce instead alternative LMW thiols, such as bacillithiol (BSH) and mycothiol (MSH). BSH is utilized by Firmicutes and MSH is the major LMW thiol of Actinomycetes. LMW thiols are required to maintain the reduced state of the cytoplasm, but are also involved in virulence mechanisms in human pathogens, such as Staphylococcus aureus, Mycobacterium tuberculosis, Streptococcus pneumoniae, Salmonella enterica subsp. Typhimurium and Listeria monocytogenes. Infection conditions often cause perturbations of the intrabacterial redox balance in pathogens, which is further affected under antibiotics treatments. During the last years, novel glutaredoxin-fused roGFP2 biosensors have been engineered in many eukaryotic organisms, including parasites, yeast, plants and human cells for dynamic live-imaging of the GSH redox potential in different compartments. Likewise bacterial roGFP2-based biosensors are now available to measure the dynamic changes in the GSH, BSH and MSH redox potentials in model and pathogenic Gram-negative and Gram-positive bacteria. In this review, we present an overview of novel functions of the bacterial LMW thiols GSH, MSH and BSH in pathogenic bacteria in virulence regulation. Moreover, recent results about the application of genetically encoded redox biosensors are summarized to study the mechanisms of host-pathogen interactions, persistence and antibiotics resistance. In particularly, we highlight recent biosensor results on the redox changes in the intracellular food-borne pathogen Salmonella Typhimurium as well as in the Gram-positive pathogens S. aureus and M. tuberculosis during infection conditions and under antibiotics treatments. These studies established a link between ROS and antibiotics resistance with the intracellular LMW thiol-redox potential. Future applications should be directed to compare the redox potentials among different clinical isolates of these pathogens in relation to their antibiotics resistance and to screen for new ROS-producing drugs as promising strategy to combat antimicrobial resistance.

Drug-susceptible tuberculosis treatment success and associated factors in Ethiopia from 2005 to 2017: a systematic review and meta-analysis

OBJECTIVES

The main aim of this study was to assess the overall tuberculosis (TB) treatment success in Ethiopia and to identify potential factors for poor TB treatment outcome.

DESIGN

A systematic review and meta-analysis of published literature was conducted. Original studies were identified through a computerised systematic search using PubMed, Google Scholar and Science Direct databases. Heterogeneity across studies was assessed using Cochran's Q test and I² statistic. Pooled estimates of treatment success were computed using the random-effects model with 95% CI using Stata V.14 software.

RESULTS

A total of 230 articles were identified in the systematic search. Of these 34 observational studies were eligible for systematic review and meta-analysis. It was found that 117 750 patients reported treatment outcomes. Treatment outcomes were assessed by World Health Organization (WHO) standard definitions of TB treatment outcome. The overall pooled TB treatment success rate in Ethiopia was 86% (with 95% CI 83%_88%). TB treatment success rate for each region showed that, Addis Ababa (93%), Oromia (84%), Amhara (86%), Southern Nations (83%), Tigray (85%) and Afar (86%). Mainly old age, HIV co-infection, retreatment cases and rural residence were the most frequently identified factors associated with poor TB treatment outcome.

CONCLUSION

The result of this study revealed that the overall TB treatment success rate in Ethiopia was below the threshold suggested by WHO (90%). There was also a discrepancy in TB treatment success rate among different regions of Ethiopia. In addition to these, HIV co-infection, older age, retreatment cases and rural residence were associated with poor treatment outcome. In order to further improve the treatment success rate, it is strategic to give special consideration for regions which had low TB treatment success and patients with TB with HIV co-infection, older age, rural residence and retreatment cases.

In vitro inhibition potential of mono-n-octyl phthalate on Mycobacterium tuberculosis H37Ra: Possibility of binding to mycobacterial PknB-An in silico approach

Fatty acids of specific chain lengths have been shown to inhibit the growth of Mycobacterium tuberculosis. In the present study, specific synthetic aromatic derivatives of n-octyl esters were investigated for their property to inhibit the growth of M. tuberculosis H37Ra. Agar well diffusion assay indicated that the crude synthetic derivatives obtained by the esterification of phthalic acid (PA) and n-octanol exhibited antimycobacterial activity. Further, the activity was authenticated with the Miroplate Alamar Blue Assay (MABA). Subsequently, the active component was purified by bioactivity guided chromatographic fractionation. The structure of the synthetic derivative was deduced by UV-Vis, FT-IR, LC-MS, GC-mass spectrometry, and NMR spectroscopy. Molecular docking and molecular dynamic simulation (MDS) were performed with Autodock 4.0 and GROMACS 5.1.2 softwares, respectively. It was found that mono-n-octyl phthalate (MOP) exhibited antimycobacterial activity with a MIC of 20 μg/mL, and not by any other related compounds, including di-n-octyl phthalate, PA, phthalic anhydride, and n-octanol. Binding of MOP with protein kinase B can participate in the binding cavity region, which was previously reported. Subsequently, we authenticate the stability with MDS. This is first report on the inhibition of M. tuberculosis growth by MOP.

IMB-SD62, a triazolothiadiazoles derivative with promising action against tuberculosis

One lead 3,6-disubstituted 1,2,4-triazolo[3,4-b][1,3,4]thiadiazole was identified as an inhibitor of shikimate dehydrogenase with antitubercular activity. Following up this compound, we optimized the lead through systematic modification of the 3 and 6 positions. The antitubercular activities in vitro, shikimate dehydrogenase inhibitory activities and cytotoxicity of derivatives were determined. We found IMB-SD62 with lower cytotoxicity and better activity. Thus, we studied the in vivo efficacy of IMB-SD62 against Mycobacterium tuberculosis and pharmacokinetics of IMB-SD62. In vivo acute M. tuberculosis H37Rv infection assay, IMB-SD62 showed antitubercular activity with the mean lung CFU counts decreasing 1.7 lg. The plasma pharmacokinetics study in rats showed that the oral bioavailability of IMB-SD62 was 14% and the half time was 1.05 h. The results of tissue distribution indicated that IMB-SD62 was mainly absorbed by liver and lung. In vitro metabolism study suggested that the metabolic ways of IMB-SD62 were dealkylated, oxidized and demethylated. CYP enzyme inhibition of IMB-SD62 in human liver microsomes was also evaluated. IMB-SD62 showed barely inhibition on CYP3A4 and CYP2D6. The excretion study manifested that IMB-SD62 was mainly eliminated by fecal excretion in rats. We concluded that based on these pharmaceutical properties, IMB-SD62 has the potential to be developed into new TB drug.

Decaprenyl-phosphoryl-ribose 2'-epimerase (DprE1): challenging target for antitubercular drug discovery

Tuberculosis has proved harmful to the entire history of mankind from past several decades. Decaprenyl-phosphoryl-ribose 2′-epimerase (DprE1) is a recent target which was identified in 2009 but unfortunately it is neither explored nor crossed phase II. In past several decades few targets were identified for effective antitubercular drug discovery. Resistance is the major problem for effective antitubercular drug discovery. Arabinose is constituent of mycobacterium cell wall. Biosynthesis of arabinose is FAD dependant two step epimerisation reaction which is catalysed by DprE1 and DprE2 flavoprotein enzymes. The current review is mainly emphases on DprE1 as a perspective challenge for further research.

Molecular dynamics simulation and binding free energy studies of novel leads belonging to the benzofuran class inhibitors of Mycobacterium tuberculosis Polyketide Synthase 13

In this work, the binding mechanism of new Polyketide Synthase 13 (Pks13) inhibitors has been studied through molecular dynamics simulation and free energy calculations. The drug Tam1 and its analogs, belonging to the benzofuran class, were submitted to 100 ns simulations, and according to the results obtained for root mean square deviation, all the simulations converged from approximately 30 ns. For the analysis of backbone flotation, the root mean square fluctuations were plotted for the Cα atoms; analysis revealed that the greatest fluctuation occurred in the residues that are part of the protein lid domain. The binding free energy value (ΔG_bind) obtained for the Tam16 lead molecule was of -51.43 kcal/mol. When comparing this result with the ΔG_bind values for the remaining analogs, the drug Tam16 was found to be the highest ranked: this result is in agreement with the experimental results obtained by Aggarwal and collaborators, where it was verified that the IC₅₀ for Tam16 is the smallest necessary to inhibit the Pks13 (IC₅₀ = 0.19 μM). The energy decomposition analysis suggested that the residues which most interact with inhibitors are: Ser1636, Tyr1637, Asn1640, Ala1667, Phe1670, and Tyr1674, from which the greatest energy contribution to Phe1670 was particularly notable. For the lead molecule Tam16, a hydrogen bond with the hydroxyl of the phenol not observed in the other analogs induced a more stable molecular structure. Aggarwal and colleagues reported this hydrogen bonding as being responsible for the stability of the molecule, optimizing its physic-chemical, toxicological, and pharmacokinetic properties.

Naphthoquinone Derivatives as Scaffold to Develop New Drugs for Tuberculosis Treatment

Despite being a curable disease, tuberculosis (TB) remains a public health problem worldwide mainly due to lengthy treatment, as well as its toxic effects, TB/HIV co-infection and the emergence of resistant Mycobacterium tuberculosis strains. These barriers reinforcing the need for development of new antimicrobial agents, that ideally should reduce the time of treatment and be active against susceptible and resistant strains. Quinones are compounds found in natural sources and among them, the naphthoquinones show antifungal, antiparasitic, and antimycobacterial activity. Thus, we evaluated the potential antimycobacterial activity of six 1,4-naphthoquinones derivatives. We determined the minimum inhibitory concentration (MIC) of the compounds against three M. tuberculosis strains: a pan-susceptible H37Rv (ATCC 27294); one mono-resistant to isoniazid (ATCC 35822); and one mono-resistant to rifampicin (ATCC 35838); the cytotoxicity in the J774A.1 (ATCC TIB-67) macrophage lineage; performed in silico analysis about absorption, distribution, metabolism, and excretion (ADME) and docking sites. All evaluated naphthoquinones were active against the three strains with MIC between 206.6 and 12.5 μM, and the compounds with lower MIC values have also showed low cytotoxicity. Moreover, two naphthoquinones derivatives 5 and 6 probably do not exhibit cross resistance with isoniazid and rifampicin, respectively, and regarding ADME analysis, no compound violated the Lipinski's rule-of-five. Considering the set of findings in this study, we conclude that these naphthoquinones could be promising scaffolds to develop new therapeutic strategies to TB.