Population Pharmacokinetics of the Antituberculosis Agent Pretomanid

Advanced drug delivery and therapeutic strategies for tuberculosis treatment

Tuberculosis (TB) remains a significant global health challenge, necessitating innovative approaches for effective treatment. Conventional TB therapy encounters several limitations, including extended treatment duration, drug resistance, patient noncompliance, poor bioavailability, and suboptimal targeting. Advanced drug delivery strategies have emerged as a promising approach to address these challenges. They have the potential to enhance therapeutic outcomes and improve TB patient compliance by providing benefits such as multiple drug encapsulation, sustained release, targeted delivery, reduced dosing frequency, and minimal side effects. This review examines the current landscape of drug delivery strategies for effective TB management, specifically highlighting lipid nanoparticles, polymer nanoparticles, inorganic nanoparticles, emulsion-based systems, carbon nanotubes, graphene, and hydrogels as promising approaches. Furthermore, emerging therapeutic strategies like targeted therapy, long-acting therapeutics, extrapulmonary therapy, phototherapy, and immunotherapy are emphasized. The review also discusses the future trajectory and challenges of developing drug delivery systems for TB. In conclusion, nanomedicine has made substantial progress in addressing the challenges posed by conventional TB drugs. Moreover, by harnessing the unique targeting abilities, extended duration of action, and specificity of advanced therapeutics, innovative solutions are offered that have the potential to revolutionize TB therapy, thereby enhancing treatment outcomes and patient compliance.

Pretomanid resistance: An update on emergence, mechanisms and relevance for clinical practice

Pretomanid (PA-824), a novel anti-tuberculosis (TB) nitroimidazoxazine, has been approved for multi-drug-resistant TB treatment for a few years. Pretomanid has been demonstrated to be highly active against Mycobacterium tuberculosis when combined with other anti-TB drugs. This review provides an update of the current knowledge on the modes of action, resistance mechanisms, emergence of drug resistance, and status of antimicrobial susceptibility testing for pretomanid and its relevance for clinical practice. Pretomanid resistance has been reported in in-vitro and animal models but not yet in clinical trials. Pretomanid-resistance-associated mutations have been reported in the fbiA, fbiB, fbiC, fbiD, ddn and fgd1 genes. However, understanding of in-vivo molecular resistance mechanisms remains limited, and complicates the development of accurate antimicrobial susceptibility testing methods for pretomanid. As such, no reference method for antimicrobial susceptibility testing of pretomanid has been established to guide clinical use. Further studies linking specific mutations, in-vitro susceptibility, drug exposure and resistance mechanisms to treatment failure with pretomanid should be prioritized.

Infant Exposure to Antituberculosis Drugs via Breast Milk and Assessment of Potential Adverse Effects in Breastfed Infants: Critical Review of Data

Infants of mothers treated for tuberculosis might be exposed to drugs via breast milk. The existing information on the exposure of breastfed infants lacks a critical review of the published data. We aimed to evaluate the quality of the existing data on antituberculosis (anti-TB) drug concentrations in the plasma and milk as a methodologically sound basis for the potential risk of breastfeeding under therapy. We performed a systematic search in PubMed for bedaquiline, clofazimine, cycloserine/terizidone, levofloxacin, linezolid, pretomanid/pa824, pyrazinamide, streptomycin, ethambutol, rifampicin and isoniazid, supplemented with update references found in LactMed^®. We calculated the external infant exposure (EID) for each drug and compared it with the recommended WHO dose for infants (relative external infant dose) and assessed their potential to elicit adverse effects in the breastfed infant. Breast milk concentration data were mainly not satisfactory to properly estimate the EID. Most of the studies suffer from limitations in the sample collection, quantity, timing and study design. Infant plasma concentrations are extremely scarce and very little data exist documenting the clinical outcome in exposed infants. Concerns for potential adverse effects in breastfed infants could be ruled out for bedaquiline, cycloserine/terizidone, linezolid and pyrazinamide. Adequate studies should be performed covering the scenario in treated mothers, breast milk and infants.

Pharmacodynamics and Bactericidal Activity of Combination Regimens in Pulmonary Tuberculosis: Application to Bedaquiline-Pretomanid-Pyrazinamide

A critical barrier to codevelopment of tuberculosis (TB) regimens is a limited ability to identify optimal drug and dose combinations in early-phase clinical testing. While pharmacokinetic-pharmacodynamic (PKPD) target attainment is the primary tool for exposure-response optimization of TB drugs, the PD target is a static index that does not distinguish individual drug contributions to the efficacy of a multidrug combination. A PKPD model of bedaquiline-pretomanid-pyrazinamide (BPaZ) for the treatment of pulmonary TB was developed as part of a dynamic exposure-response approach to regimen development. The model describes a time course relationship between the drug concentrations in plasma and their individual as well as their combined effect on sputum bacillary load assessed by solid culture CFU counts and liquid culture time to positivity (TTP). The model parameters were estimated using data from the phase 2A studies NC-001-(J-M-Pa-Z) and NC-003-(C-J-Pa-Z). The results included a characterization of BPaZ activity as the most and least sensitive to changes in pyrazinamide and bedaquiline exposures, respectively, with antagonistic activity of BPa compensated by synergistic activity of BZ and PaZ. Simulations of the NC-003 study population with once-daily bedaquiline at 200 mg, pretomanid at 200 mg, and pyrazinamide at 1,500 mg showed BPaZ would require 3 months to attain liquid culture negativity in 90% of participants. These results for BPaZ were intended to be an example application with the general approach aimed at entirely novel drug combinations from a growing pipeline of new and repurposed TB drugs.

Clinical standards for the dosing and management of TB drugs

BACKGROUND: Optimal drug dosing is important to ensure adequate response to treatment, prevent development of drug resistance and reduce drug toxicity. The aim of these clinical standards is to provide guidance on 'best practice´ for dosing and management of TB drugs.METHODS: A panel of 57 global experts in the fields of microbiology, pharmacology and TB care were identified; 51 participated in a Delphi process. A 5-point Likert scale was used to score draft standards. The final document represents the broad consensus and was approved by all participants.RESULTS: Six clinical standards were defined: Standard 1, defining the most appropriate initial dose for TB treatment; Standard 2, identifying patients who may be at risk of sub-optimal drug exposure; Standard 3, identifying patients at risk of developing drug-related toxicity and how best to manage this risk; Standard 4, identifying patients who can benefit from therapeutic drug monitoring (TDM); Standard 5, highlighting education and counselling that should be provided to people initiating TB treatment; and Standard 6, providing essential education for healthcare professionals. In addition, consensus research priorities were identified.CONCLUSION: This is the first consensus-based Clinical Standards for the dosing and management of TB drugs to guide clinicians and programme managers in planning and implementation of locally appropriate measures for optimal person-centred treatment to improve patient care.

Male reproductive hormones in patients treated with pretomanid

BACKGROUND:

Pretomanid (Pa) is a nitroimidazole-class drug recently approved by the US Food and Drug Administration and other regulatory authorities as part of a regimen for treating highly drug-resistant pulmonary Mycobacterium tuberculosis infections. Studies in rodents identified the testis as a target organ of concern, which led to monitoring of reproductive hormones in >800 male patients enrolled in four clinical trials of Pa-containing regimens and the HRZE (isoniazid+rifampin+pyrazinamide+ethambutol) control regimen.

METHODS:

Serum hormone levels relevant to male reproductive health – follicle stimulating hormone (FSH), luteinizing hormone (LH), inhibin B (InhB) and total testosterone (T) – from the four clinical trials were summarized numerically and analyzed by repeated-measures modeling.

RESULTS:

Hormone levels generally behaved similarly in Pa-containing and HRZE arms. Relative to baseline, serum T and InhB levels generally increased at the end of treatment and follow-up. FSH and LH levels were variable, but were generally at or below baseline levels by follow-up. Before treatment, many patients were borderline hypogonadal, with T levels near the lower limits of the normal range.

CONCLUSION:

Changes in male hormones in four clinical trials studying patients with TB indicate that Pa-containing treatment was not associated with testicular toxicity but rather led to improvement in the underlying hypogonadism.

OUP accepted manuscript

Objectives

To develop a robust phenotypic antimicrobial susceptibility testing (AST) method with a correctly set breakpoint for pretomanid (Pa), the most recently approved anti-tuberculosis drug.

Methods

The Becton Dickinson Mycobacterial Growth Indicator Tube™ (MGIT) system was used at six laboratories to determine the MICs of a phylogenetically diverse collection of 356 Mycobacterium tuberculosis complex (MTBC) strains to establish the epidemiological cut-off value for pretomanid. MICs were correlated with WGS data to study the genetic basis of differences in the susceptibility to pretomanid.

Results

We observed ancient differences in the susceptibility to pretomanid among various members of MTBC. Most notably, lineage 1 of M. tuberculosis, which is estimated to account for 28% of tuberculosis cases globally, was less susceptible than lineages 2, 3, 4 and 7 of M. tuberculosis, resulting in a 99th percentile of 2 mg/L for lineage 1 compared with 0.5 mg/L for the remaining M. tuberculosis lineages. Moreover, we observed that higher MICs (≥8 mg/L), which probably confer resistance, had recently evolved independently in six different M. tuberculosis strains. Unlike the aforementioned ancient differences in susceptibility, these recent differences were likely caused by mutations in the known pretomanid resistance genes.

Conclusions

In light of these findings, the provisional critical concentration of 1 mg/L for MGIT set by EMA must be re-evaluated. More broadly, these findings underline the importance of considering the global diversity of MTBC during clinical development of drugs and when defining breakpoints for AST.

Characterizing Absorption Properties of Dispersible Pretomanid Tablets Using Population Pharmacokinetic Modelling

BACKGROUND AND INTRODUCTION

The dispersible tablet formulation (DTF) of pretomanid has been developed to facilitate future use in children. This work aimed to assess the pharmacokinetics (PK) and relative bioavailability of the DTF compared to the marketed formulation (MF) and the potential influence of dose.

METHODS

Pretomanid DTF was investigated in a single-dose, randomized, four-period, cross-over study, with 7 days of washout between doses. Forty-eight healthy volunteers were enrolled and randomized into one of two panels to receive doses either in the fasted state or after a high-fat meal. Each volunteer received doses of 10, 50, and 200 mg DTF, and 200 mg MF pretomanid. Blood samples for pharmacokinetic assessment were drawn following a rich schedule up to 96 h after each single dose. The study data from the panel receiving the high-fat meal were analyzed using a nonlinear mixed-effects modeling approach, and all data were characterized with noncompartmental methods.

RESULTS

A one-compartment model with first-order elimination and absorption through a transit compartment captured the mean and variability of the observed pretomanid concentrations with acceptable precision. No significant difference in bioavailability was found between formulations. The mean absorption time for the DTF was typically 137% (86-171%) of that for the MF. The bioavailability was found to be dose dependent with a small positive and larger negative correlation under fed and fasted conditions, respectively.

CONCLUSION

Using data from a relative bioavailability study in healthy adult volunteers, a mathematical model has been developed to inform dose selection for the investigation of pretomanid in children using the new dispersible tablet formulation. Under fed conditions and at the currently marketed adult dose of 200 mg, the formulation type was found to influence the absorption rate, but not the bioavailability. The bioavailability of the DTF was slightly positively correlated with doses when administered with food.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT04309656, first posted on 16 March 2020.

Pretomanid for tuberculosis treatment: an update for clinical purposes

Coronavirus disease (COVID-19) pandemic determined a 10 years-set back in tuberculosis (TB) control programs. Recent advances in available therapies may help recover the time lost. While Linezolid (LZD) and Bedaquiline (BDQ), previously Group D second line drugs (SLDs) for TB, have been relocated to Group A, other drugs are currently being studied in regimens for drug resistant TB (DR-TB). Among these, Pretomanid (PA), a recently introduced antimycobacterial drug derived from nitroimidazole with both solid bactericidal and bacteriostatic effect, and with an excellent effectiveness and tolerability profile, is in the spotlight. Following promising data obtained from recently published and ongoing randomized controlled trials (RCTs), the World Health Organization (WHO) determined to include PA in its guidelines for the treatment of rifampicin-resistant (RR), multi drug resistant (MDR) and pre-extensively drug resistant TB (pre-XDR-TB) with BDQ, LZD and Moxifloxacine (MFX) in a 6-month regimen. Although further studies on the subject are needed, PA may also represent a treatment option for drug-susceptible TB (DS-TB), latent TB infection (LTBI) and non tuberculous mycobacteria (NTM). This narrative review aims to examine current implementation options and future possibilities for PA in the never-ending fight against TB.

Evaluating the effect of clofazimine against Mycobacterium tuberculosis when given alone or in combination with pretomanid, bedaquiline or linezolid

Clofazimine (CFZ) has been regaining prominence for treating tuberculosis in recent years. However, as a single drug, it shows limited efficacy and optimal combination partners have not been identified. Therefore, the objective of our analysis was to evaluate the efficacy of CFZ-containing two-drug regimen with pretomanid (PMD), bedaquiline (BDQ) or linezolid (LZD) by determining: i) their pharmacodynamic (PD) mode of interaction against Mycobacterium tuberculosis (Mtb) strain H37Rv in log- and acid-metabolic states, and Mtb strain 18b in a non-replicating persister metabolic state, ii) to predict bacterial cell kill of the drugs alone and in combination, and iii) to evaluate the relationship between the interaction mode and bacterial cell kill amount. The results of our Greco universal response surface analysis showed that CFZ was at least additive with a clear trend towards synergy when combined with PMD, BDQ, and LZD against Mtb in all explored metabolic states under in vitro checkerboard assay conditions. They further showed that all 2-drug combination regimens exerted more bacterial kill than any of the drugs alone. CFZ alone showed the least antimicrobial efficacy amongst the evaluated drugs and there was a lack of correlation between the mode of interaction and the amount of bacterial kill. However, we may underestimate the effect of CFZ in this screening approach due to limited in vitro study duration and neglect of target site accumulation.

Emerging Therapeutics, Technologies, and Drug Development Strategies to Address Patient Nonadherence and Improve Tuberculosis Treatment

Imperfect medication adherence remains the biggest predictor of treatment failure for patients with tuberculosis. Missed doses during treatment lead to relapse, tuberculosis resistance, and further spread of disease. Understanding individual patient phenotypes, population pharmacokinetics, resistance development, drug distribution to tuberculosis lesions, and pharmacodynamics at the site of infection is necessary to fully measure the impact of adherence on patient outcomes. To decrease the impact of expected variability in drug intake on tuberculosis outcomes, an improvement in patient adherence and new forgiving regimens that protect against missed doses are needed. In this review, we summarize emerging technologies to improve medication adherence in clinical practice and provide suggestions on how digital adherence technologies can be incorporated in clinical trials and practice and the drug development pipeline that will lead to more forgiving regimens and benefit patients suffering from tuberculosis. Expected final online publication date for the Annual Review of Pharmacology and Toxicology, Volume 62 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Population pharmacokinetics and pharmacodynamics of investigational regimens' drugs in the TB-PRACTECAL clinical trial (the PRACTECAL-PKPD study): a prospective nested study protocol in a randomised controlled trial

INTRODUCTION

Drug-resistant tuberculosis (TB) remains a global health threat, with little over 50% of patients successfully treated. Novel regimens like the ones being studied in the TB-PRACTECAL trial are urgently needed. Understanding anti-TB drug exposures could explain the success or failure of these trial regimens. We aim to study the relationship between the patients' exposure to anti-TB drugs in TB-PRACTECAL investigational regimens and their treatment outcomes.

METHODS AND ANALYSIS

Adults with multidrug-resistant TB randomised to investigational regimens in TB-PRACTECAL will be recruited to a nested pharmacokinetic-pharmacodynamic (PKPD) study. Venous blood samples will be collected at 0, 2 and 23 hours postdose on day 1 and 0, 6.5 and 23 hours postdose during week 8 to quantify drug concentrations in plasma. Trough samples will be collected during week 12, 16, 20 and 24 visits. Opportunistic samples will be collected during weeks 32 and 72. Drug concentrations will be quantified using liquid chromatography-tandem mass spectrometry. Sputum samples will be collected at baseline, monthly to week 24 and then every 2 months to week 108 for MICs and bacillary load quantification. Full blood count, urea and electrolytes, liver function tests, lipase, ECGs and ophthalmology examinations will be conducted at least monthly during treatment.PK and PKPD models will be developed for each drug with nonlinear mixed effects methods. Optimal dosing will be investigated using Monte-Carlo simulations.

ETHICS AND DISSEMINATION

The study has been approved by the Médecins sans Frontières (MSF) Ethics Review Board, the LSHTM Ethics Committee, the Belarus RSPCPT ethics committee and PharmaEthics and the University of Witwatersrand Human Research ethics committee in South Africa. Written informed consent will be obtained from all participants. The study results will be shared with public health authorities, presented at scientific conferences and published in a peer-reviewed journal.

TRIAL REGISTRATION NUMBER

NCT04081077; Pre-results.

Chemical Classes Presenting Novel Antituberculosis Agents Currently in Different Phases of Drug Development: A 2010-2020 Review

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), is a curable airborne disease currently treated using a drug regimen consisting of four drugs. Global TB control has been a persistent challenge for many decades due to the emergence of drug-resistant Mtb strains. The duration and complexity of TB treatment are the main issues leading to treatment failures. Other challenges faced by currently deployed TB regimens include drug-drug interactions, miss-matched pharmacokinetics parameters of drugs in a regimen, and lack of activity against slow replicating sub-population. These challenges underpin the continuous search for novel TB drugs and treatment regimens. This review summarizes new TB drugs/drug candidates under development with emphasis on their chemical classes, biological targets, mode of resistance generation, and pharmacokinetic properties. As effective TB treatment requires a combination of drugs, the issue of drug-drug interaction is, therefore, of great concern; herein, we have compiled drug-drug interaction reports, as well as efficacy reports for drug combinations studies involving antitubercular agents in clinical development.

Population Pharmacokinetics and Bayesian Dose Adjustment to Advance TDM of Anti-TB Drugs

Tuberculosis (TB) is still the number one cause of death due to an infectious disease. Pharmacokinetics and pharmacodynamics of anti-TB drugs are key in the optimization of TB treatment and help to prevent slow response to treatment, acquired drug resistance, and adverse drug effects. The aim of this review was to provide an update on the pharmacokinetics and pharmacodynamics of anti-TB drugs and to show how population pharmacokinetics and Bayesian dose adjustment can be used to optimize treatment. We cover aspects on preclinical, clinical, and population pharmacokinetics of different drugs used for drug-susceptible TB and multidrug-resistant TB. Moreover, we include available data to support therapeutic drug monitoring of these drugs and known pharmacokinetic and pharmacodynamic targets that can be used for optimization of therapy. We have identified a wide range of population pharmacokinetic models for first- and second-line drugs used for TB, which included models built on NONMEM, Pmetrics, ADAPT, MWPharm, Monolix, Phoenix, and NPEM2 software. The first population models were built for isoniazid and rifampicin; however, in recent years, more data have emerged for both new anti-TB drugs, but also for defining targets of older anti-TB drugs. Since the introduction of therapeutic drug monitoring for TB over 3 decades ago, further development of therapeutic drug monitoring in TB next steps will again depend on academic and clinical initiatives. We recommend close collaboration between researchers and the World Health Organization to provide important guideline updates regarding therapeutic drug monitoring and pharmacokinetics/pharmacodynamics.

Pretomanid dose selection for pulmonary tuberculosis: An application of multi-objective optimization to dosage regimen design

Clinical development of combination chemotherapies for tuberculosis (TB) is complicated by partial or restricted phase II dose‐finding. Barriers include a propensity for drug resistance with monotherapy, practical limits on numbers of treatment arms for component dose combinations, and limited application of current dose selection methods to multidrug regimens. A multi‐objective optimization approach to dose selection was developed as a conceptual and computational framework for currently evolving approaches to clinical testing of novel TB regimens. Pharmacokinetic‐pharmacodynamic (PK‐PD) modeling was combined with an evolutionary algorithm to identify dosage regimens that yield optimal trade‐offs between multiple conflicting therapeutic objectives. The phase IIa studies for pretomanid, a newly approved nitroimidazole for specific cases of highly drug‐resistant pulmonary TB, were used to demonstrate the approach with Pareto optimized dosing that best minimized sputum bacillary load and the probability of drug‐related adverse events. Results include a population‐typical characterization of the recommended 200 mg once daily dosage, the optimality of time‐dependent dosing, examples of individualized therapy, and the determination of optimal loading doses. The approach generalizes conventional PK‐PD target attainment to a design problem that scales to drug combinations, and provides a benefit‐risk context for clinical testing of complex drug regimens.

Phase 1 Study of the Effects of the Tuberculosis Treatment Pretomanid, Alone and in Combination With Moxifloxacin, on the QTc Interval in Healthy Volunteers

Tuberculosis (TB) continues to be a serious threat to public health throughout the world. Newer treatments are needed that could offer simplified regimens with activity against both drug‐sensitive and drug‐resistant bacilli, while optimizing safety. Pretomanid (PA‐824), a nitroimidazooxazine compound, is a new drug for the treatment of pulmonary TB that was recently approved in the United States and Europe in the context of a regimen combined with bedaquiline and linezolid. This phase 1 double‐blind, randomized, placebo‐controlled crossover study specifically examined the effect of single‐dose administration of pretomanid 400 or 1000 mg and pretomanid 400 mg plus moxifloxacin 400 mg on the QTc interval in 74 healthy subjects. Subjects were fasting at the time of drug administration. Pretomanid concentrations following single 400‐ or 1000‐mg doses were not associated with any QT interval prolongation of clinical concern. Moxifloxacin did not alter the pharmacokinetics of pretomanid, and the effect of pretomanid 400 mg plus moxifloxacin 400 mg on the individually corrected QT interval was consistent with the effect of moxifloxacin alone. Both drugs were generally well tolerated. Although supratherapeutic exposure of pretomanid relative to the now‐recommended dosing with food was not achieved, these findings contribute to the favorable assessment of cardiac safety for pretomanid.

An Exposure-Response Perspective on the Clinical Dose of Pretomanid

Pretomanid was approved by the U.S. FDA, via the limited population pathway for antibacterial and antifungal drugs, as part of a three-drug regimen with bedaquiline and linezolid for the treatment of extensively drug-resistant and treatment-intolerant or nonresponsive multidrug-resistant tuberculosis. The recommended dose of pretomanid is 200 mg once daily with food. The objective of this work was to retrospectively evaluate this recommended dose by means of exposure-response (E-R) modeling applied to outcomes of both efficacy and safety. Cox proportional-hazards modeling was used, with the steady-state average pretomanid concentration as the exposure metric. The efficacy outcome was time to sputum culture conversion (TSCC) to negative. The safety outcomes were times to the first occurrence of adverse events in classes selected from either pretomanid's investigator brochure or the new drug application (NDA) submission as recognized safety signals for pretomanid based on preclinical as well as clinical experience. Significant E-R relationships were found for TSCC and two adverse-event classes, vomiting (a single preferred term) and gastrointestinal (GI) symptoms (a collection of related terms). No significant E-R relationships were found for the single preferred terms nausea, alanine aminotransferase (ALT) increased, aspartate aminotransferase (AST) increased, and headache and for the collections hepatic disorders, transaminases increased, skin and subcutaneous tissue disorders, and headache. The results suggest that the recommended dose of pretomanid, 200 mg given in the fed state, is appropriate over the range of pharmacokinetic exposures.

Pretomanid: A novel therapeutic paradigm for treatment of drug resistant tuberculosis

Tuberculosis is currently an anticipated driver of pandemic diseases. It remains an imminent issue accounting for about 1.4 million deaths annually across the world. Since the evolution of human entity drug susceptible tuberculosis was managed through potent first line therapies. Unfortunately, the emergence of newer multitude strains refractory amongst available drugs in Drug resistant TB has led to an emergence MDR-TB and XDR-TB. Moreover, the increasing incidence of drug susceptible TB in developing countries paved way to development of new guidelines for treating various form of tuberculosis. Furthermore, newer regimens are warranted to combat resistance that preferably cause a reduction in mortality. Until now, various ongoing trials are being carried in order to potentially evaluate the suitable novel drug candidates, repurposed drugs and host directed therapies that will optimistically be safe, easy to tolerate, cost effective and non-toxic that will modify the prospects for treating drug resistant TB and latent TB. In context, the current scenario seems to impose a significant challenge on health care researchers in the field of drug discovery owing to complexities, prolong treatment duration, and is cumbersome. Pretomanid is a novel drug with potent bactericidal properties emerging a key advancement used in combination along with other drug therapies This review details the role of pretomanid in treating tuberculosis and the clinical trials in adultsd.

Fully weekly antituberculosis regimen: a proof-of-concept study

BACKGROUND

The World Health Organization recommends supervising the treatment of tuberculosis. Intermittent regimens have the potential to simplify the supervision and improve compliance. Our objective was to analyse the sterilising activity of once-weekly regimens based on drugs with a long half-life, bedaquiline and rifapentine, in a murine model of tuberculosis.

METHODS

300 Swiss mice were infected intravenously infected with ×10^-6 CFU Mycobacterium tuberculosis H37Rv. Mice were treated once weekly with regimens containing: 1) bedaquiline, rifapentine and pyrazinamide (BPZ); 2) BPZ plus moxifloxacin (BPZM); 3) BPZM plus clofazimine (BPZMC); 4) the standard daily regimen of tuberculosis. All regimens were given for 4 or 6 months. Bactericidal and sterilising activity were assessed.

RESULTS

After 2 months of treatment, the mean count in lungs was 0.76±0.60 log₁₀ CFU in mice treated with the daily control regimen and negative in all mice treated with once-weekly regimens (p<0.05 compared to the daily control). All mice had negative lung cultures on completion of either 4 or 6 months of treatment, whereas 3 months after 4 and 6 months of treatment, respectively, the relapse rate was 64% and 13% in the standard daily regimen, 5% and 0% in BPZ, 0% and 0% in BPMZ and 0% and 5% in BPMZC (p<0.05 for all once-weekly regimens versus 4-month daily control; p>0.05 for all once-weekly regimens versus 6-month daily control).

CONCLUSIONS

BPZ-based once-weekly regimens have higher sterilising activity than the standard daily regimen and could greatly simplify treatment administration and possibly shorten the duration of tuberculosis treatment.

Identification of pyrvinium pamoate as an anti-tuberculosis agent in vitro and in vivo by SOSA approach amongst known drugs

Tuberculosis (TB), caused by Mycobacterium tuberculosis (M.tb) bacteria, is a leading infectious cause of mortality worldwide. The emergence of drug-resistant M. tb has made control of TB more difficult. The selective optimization of side activities (SOSA) approach uses old drugs for new pharmacological targets. In the present study by using SOSA approach, we have successfully identified pyrvinium pamoate (PP) which is capable of inhibiting the growth of mycobacteria, including M. tb H37Rv, Mycobacterium smegmatis, Bacille Calmette-Guérin (BCG), M. tb H37Ra, and drug-resistant M. tb clinical isolates in vitro from 1280 known drugs library. The MIC₉₉ of PP, the minimum inhibitory concentration that inhibits more than 99% of M. tb H37Rv and the drug-resistant M. tb clinical isolates, ranges from 1.55 to 4.8 µg/mL. Importantly, PP could reduce the bacterial colony-forming units (CFUs) in lung, spleen and liver tissues, and effectively inhibit inflammatory response in M. tb H37Rv, multidrug-resistant (MDR) M. tb and extensively drug-resistant (XDR) M.tb-infected mice. Our results clearly show that the PP has the potential application for treatment of TB.