Cumulative Fraction of Response for Once- and Twice-Daily Delamanid in Patients with Pulmonary Multidrug-Resistant Tuberculosis

Model-Informed Once-Daily Dosing Strategy for Bedaquiline and Delamanid in Children, Adolescents and Adults with Tuberculosis

The complexity of the currently registered dosing schedules for bedaquiline and delamanid is a barrier to uptake in drug-resistant tuberculosis treatment across all ages. A simpler once-daily dosing schedule is critical to ensure patient-friendly regimens with good adherence. We assessed expected drug exposures with proposed once-daily doses for adults and compared novel model-informed once-daily dosing strategies for children with current World Health Organization (WHO) recommended dosing. A reference individual and virtual pediatric population were generated to simulate exposures in adults and children, respectively. Published population models characterizing the exposures of bedaquiline and its metabolite M2, delamanid, and its metabolite DM-6705 were utilized. During simulation, child growth during treatment along with several CYP3A4 ontogeny profiles was accounted for. Exposures in children were compared with simulated adult targets to assess the expected treatment efficacy and safety. In adults, the proposed bedaquiline once-daily dosing (400 mg daily for 2 weeks followed by 100 mg daily for 22 weeks) yielded 14% higher exposures of bedaquiline and M2 compared to the labeled dosing scheme at 24 weeks; for delamanid and DM-6705, the suggested 300 mg daily dose provided 13% lower exposures at steady state. For children, the cumulative proportions of exposures of both drugs showed < 5% difference between WHO-recommended and proposed once-daily dosing. This study demonstrated the use of model-informed approaches to propose rational and simpler regimens for bedaquiline and delamanid in adults and children. The new once-daily dosing strategies will be tested in the PARADIGM4TB and IMPAACT 2020 trials in adults and children, respectively.

Pharmacology of emerging drugs for the treatment of multi-drug resistant tuberculosis

Mycobacterium tuberculosis (TB) remains the leading cause of infection-related mortality worldwide. Drug resistance, need for multiple antimycobacterial agents, prolonged treatment courses, and medication-related side effects are complicating factors to TB cure. The introduction of treatment regimens containing the novel agents bedaquiline, pretomanid, and linezolid, with or without moxifloxacin (BPaL-M or BPaL, respectively) have substantially reduced TB-related morbidity and mortality and are associated with favorable rates of treatment completion and cure. This review summarizes key information on the pharmacology and treatment principles for moxifloxacin, bedaquiline, delamanid, pretomanid, linezolid, and tedizolid in the treatment of multi-drug resistant TB, with recommendations provided to address and attenuate common adverse effects during treatment.

Safety, pharmacokinetics, and early bactericidal activity of quabodepistat in combination with delamanid, bedaquiline, or both in adults with pulmonary tuberculosis: a randomised, active-controlled, open-label trial

BACKGROUND

Quabodepistat (formerly OPC-167832) showed potent activity in preclinical studies and in the first stage of an early bactericidal activity study in adults with smear-positive, drug-susceptible pulmonary tuberculosis. Stage 2 of this study was designed to evaluate the safety, tolerability, pharmacokinetics, and early bactericidal activity of quabodepistat in combination with delamanid, bedaquiline, or both versus rifampicin, isoniazid, ethambutol, and pyrazinamide combination therapy for 14 days.

METHODS

Stage 2 of this open-label, active-controlled, randomised, parallel-group study was conducted at two research sites in South Africa in adults (aged 18-64 years) with drug-susceptible pulmonary tuberculosis. Eligible participants had a BMI of 16-32 kg/m2 and the ability to produce an adequate volume of sputum (≥10 mL overnight) and were excluded if they had drug-resistant tuberculosis or previous treatment for Mycobacterium tuberculosis within the past 3 years. Participants were centrally randomly assigned via interactive web response technology system, with no stratification, into four treatment groups in a ratio of 14:14:14:4 (quabodepistat 30 mg plus delamanid 300 mg, quabodepistat 30 mg plus bedaquiline 400 mg, or quabodepistat 30 mg plus delamanid 300 mg plus bedaquiline 400 mg orally once daily for 14 days, or rifampicin, isoniazid, ethambutol, and pyrazinamide combination therapy [control] according to local standard of care for 20 days). The primary outcomes were safety and tolerability during and after 14 days of treatment in all participants who received any study medication and pharmacokinetics at day 1 and day 14 in participants in the quabodepistat groups with adequate data for deriving pharmacokinetics parameters. The main secondary outcome was bactericidal activity from baseline to day 14 in all eligible participants who were quantitatively culture-positive at baseline. The study was not powered for formal statistical hypothesis testing; therefore, data were summarised by treatment group with descriptive statistics. This study is registered with ClinicalTrials.gov (NCT03678688) and is closed to new participants.

FINDINGS

98 participants were screened for entry into stage 2 of the trial between Feb 1, 2021, and Jan 27, 2022, of whom 46 were randomly assigned (14 to each quabodepistat group, 4 to the control group) and 44 received at least one dose of study medication (one patient excluded from the quabodepistat plus delamanid and quabodepistat plus bedaquiline groups). 32 (73%) of 44 participants had at least one treatment-emergent adverse event. Most events (30/32 [94%]) were mild or moderate; the most common treatment-emergent adverse events (≥2 participants; not related to study drugs) were headache (4/44 [9%]), dizziness (3/44 [7%]), abdominal pain (2/44 [5%]), pruritus (2/44 [5%]), and nausea (2/44 [5%]). Two serious adverse events were reported in two participants in the quabodepistat and bedaquiline cohort (anal abscess [n=1], pneumothorax [n=1]); both were deemed not related to study drug. Quabodepistat exposure was minimally affected by coadministration of delamanid or bedaquiline, with lower exposure in the quabodepistat and bedaquiline cohorts (maximum plasma concentration for quabodepistat plus delamanid 208 ng/mL [SD 61; n=11]; quabodepistat plus bedaquiline 175 ng/mL [31; n=10]; quabodepistat plus delamanid plus bedaquiline 183 ng/mL [52; n=11]). Maximum quabodepistat concentrations were achieved approximately 3 h after administration in all combinations. Mean elimination half-life was shorter in combinations with bedaquiline than without bedaquiline (12·3-14·5 h vs 15·2 h). Mean changes from baseline to day 14 of sputum log10 colony-forming units per mL were -2·73 (SD 1·51) for quabodepistat plus delamanid plus bedaquiline (n=12) and -2·71 (SD 0·92) for control (n=19); mean change was -2·17 (SD 1·83) in the quabodepistat plus delamanid cohort (n=11) and -1·97 (SD 1·29) in the quabodepistat plus bedaquiline cohort (n=11).

INTERPRETATION

In this 14-day trial, quabodepistat plus delamanid plus bedaquiline, a novel three-drug combination, appeared to be safe, well tolerated, and provided robust early bactericidal activity in adults with drug-susceptible pulmonary tuberculosis. Further evaluation is warranted.

FUNDING

Otsuka Pharmaceutical Development & Commercialization and the Bill & Melinda Gates Foundation.

Therapeutic drug monitoring in tuberculosis

PURPOSE

Therapeutic drug monitoring (TDM) is a standard clinical procedure that uses the pharmacokinetic and pharmacodynamic parameters of the drug in the body to determine the optimal dose. The pharmacokinetic variability of the drug(s) is a significant contributor to poor treatment outcomes, including the development of acquired drug resistance. TDM aids in dose optimization and improves outcomes while lessening drug toxicity. TDM is used to manage patients with tuberculosis (TB) who exhibit a slow response to therapy, despite good compliance and drug-susceptible organisms. Additional indications include patients at risk of malabsorption or delayed absorption of TB drugs and patients with drug-drug interaction and drug toxicity, which confirm compliance with therapy. TDM usually requires two blood samples: the 2 h and the 6 h post-dose. This narrative review will discuss the pharmacokinetics and pharmacodynamics of TB drugs, determinants of poor response to therapy, indications of TDM, methods of performing TDM, and its interpretations.

METHODS

This is a narrative review. We searched PubMed, Embase, and the CINAHL from inception to April 2024. We used the following search terms: tuberculosis, therapeutic drug monitoring, anti-TB drugs, pharmacokinetics, pharmacodynamics, limited sample strategies, diabetes and TB, HIV and TB, and multidrug-resistant TB. All types of articles were selected.

RESULTS

TDM is beneficial in managing TB, especially in patients with slow responses, drug-resistance TB, recurrent TB, and comorbidities such as diabetes mellitus and human immunodeficiency virus infection.

CONCLUSION

TDM is beneficial for improving outcomes, reducing the risk of acquired drug resistance, and avoiding side effects.

Omadacycline pharmacokinetics/pharmacodynamics and efficacy against multidrug-resistant Mycobacterium tuberculosis in the hollow fiber system model

Seventy-five years ago, first-generation tetracyclines demonstrated limited efficacy in the treatment of tuberculosis but were more toxic than efficacious. We performed a series of pharmacokinetic/pharmacodynamic (PK/PD) experiments with a potentially safer third-generation tetracycline, omadacycline, for the treatment of multidrug-resistant tuberculosis (MDR-TB). Mycobacterium tuberculosis (Mtb) H37Rv and an MDR-TB clinical strain (16D) were used in the minimum inhibitory concentration (MIC) and static concentration-response studies in test tubes, followed by a PK/PD study using the hollow fiber system model of TB (HFS-TB) that examined six human-like omadacycline doses. The inhibitory sigmoid maximal effect (Emax) model and Monte Carlo experiments (MCEs) were used for data analysis and clinical dose-finding, respectively. The omadacycline MIC for both Mtb H37Rv and MDR-TB clinical strain was 16 mg/L but dropped to 4 mg/L with daily drug supplementation to account for omadacycline degradation. The Mycobacteria Growth Indicator Tube MIC was 2 mg/L. In the test tubes, omadacycline killed 4.39 log10 CFU/mL in 7 days. On Day 28 of the HFS-TB study, the Emax was 4.64 log10 CFU/mL, while exposure mediating 50% of Emax (EC50) was an area under the concentration-time curve to MIC (AUC0-24/MIC) ratio of 22.86. This translates to PK/PD optimal exposure or EC80 as AUC0-24/MIC of 26.93. The target attainment probability of the 300-mg daily oral dose was 90% but fell at MIC ≧4 mg/L. Omadacycline demonstrated efficacy and potency against both drug-susceptible and MDR-TB. Further studies are needed to identify the omadacycline effect in combination therapy for the treatment of both drug-susceptible and MDR-TB.

Determining the Delamanid Pharmacokinetics/Pharmacodynamics Susceptibility Breakpoint Using Monte Carlo Experiments

Antimicrobial susceptibility testing, based on clinical breakpoints that incorporate pharmacokinetics/pharmacodynamics (PK/PD) and clinical outcomes, is becoming a new standard in guiding individual patient therapy as well as for drug resistance surveillance. However, for most antituberculosis drugs, breakpoints are instead defined by the epidemiological cutoff values of the MIC of phenotypically wild-type strains irrespective of PK/PD or dose. In this study, we determined the PK/PD breakpoint for delamanid by estimating the probability of target attainment for the approved dose administered at 100 mg twice daily using Monte Carlo experiments. We used the PK/PD targets (0- to 24-h area under the concentration-time curve to MIC) identified in a murine chronic tuberculosis model, hollow fiber system model of tuberculosis, early bactericidal activity studies of patients with drug-susceptible tuberculosis, and population pharmacokinetics in patients with tuberculosis. At the MIC of 0.016 mg/L, determined using Middlebrook 7H11 agar, the probability of target attainment was 100% in the 10,000 simulated subjects. The probability of target attainment fell to 25%, 40%, and 68% for PK/PD targets derived from the mouse model, the hollow fiber system model of tuberculosis, and patients, respectively, at the MIC of 0.031 mg/L. This indicates that an MIC of 0.016 mg/L is the delamanid PK/PD breakpoint for delamanid at 100 mg twice daily. Our study demonstrated that it is feasible to use PK/PD approaches to define a breakpoint for an antituberculosis drug.

Pharmacokinetics and pharmacodynamics of anti-tuberculosis drugs: An evaluation of in vitro, in vivo methodologies and human studies

There has been an increased interest in pharmacokinetics and pharmacodynamics (PKPD) of anti-tuberculosis drugs. A better understanding of the relationship between drug exposure, antimicrobial kill and acquired drug resistance is essential not only to optimize current treatment regimens but also to design appropriately dosed regimens with new anti-tuberculosis drugs. Although the interest in PKPD has resulted in an increased number of studies, the actual bench-to-bedside translation is somewhat limited. One of the reasons could be differences in methodologies and outcome assessments that makes it difficult to compare the studies. In this paper we summarize most relevant in vitro, in vivo, in silico and human PKPD studies performed to optimize the drug dose and regimens for treatment of tuberculosis. The in vitro assessment focuses on MIC determination, static time-kill kinetics, and dynamic hollow fibre infection models to investigate acquisition of resistance and killing of Mycobacterium tuberculosis populations in various metabolic states. The in vivo assessment focuses on the various animal models, routes of infection, PK at the site of infection, PD read-outs, biomarkers and differences in treatment outcome evaluation (relapse and death). For human PKPD we focus on early bactericidal activity studies and inclusion of PK and therapeutic drug monitoring in clinical trials. Modelling and simulation approaches that are used to evaluate and link the different data types will be discussed. We also describe the concept of different studies, study design, importance of uniform reporting including microbiological and clinical outcome assessments, and modelling approaches. We aim to encourage researchers to consider methods of assessing and reporting PKPD of anti-tuberculosis drugs when designing studies. This will improve appropriate comparison between studies and accelerate the progress in the field.

Delamanid Added to an Optimized Background Regimen in Children with Multidrug-Resistant Tuberculosis: Results of a Phase I/II Clinical Trial

Delamanid has been demonstrated to be safe and effective for treatment of adult multidrug-resistant tuberculosis (MDR-TB) and has been approved by the European Commission for treatment of pediatric MDR-TB patients at least 10 kg in weight, making the drug no longer limited to adults. A 10-day phase I age deescalation study was conducted, followed by a 6-month phase II extension study, to assess the pharmacokinetics, safety, tolerability, and preliminary efficacy of delamanid when combined with optimized background regimen (OBR) in children (birth to 17 years) with MDR-TB. Delamanid administered at 100 mg twice-daily (BID), 50 mg BID, and 25 mg BID resulted in exposures in 12- to 17- (n = 7), 6- to 11- (n = 6), and 3- to 5-year-olds (n = 12), respectively, comparable with those in adults at the approved adult dosage (100 mg BID). Exposures in 0- to 2-year-olds (n = 12) following a weight-based dosing regimen (5 mg once daily [QD] to 10 mg BID) were lower than predicted from pharmacokinetic modeling of the older three age groups and below target exposures in adults. Overall, the safety profile of delamanid in children 0 to 17 years of age was similar to the adult profile. At 24 months after the first delamanid dose, 33/37 children (89.2%) had favorable treatment outcomes, as defined by the World Health Organization (15/37 [40.5%] cured and 18/37 [48.6%] completed treatment). A new pediatric delamanid formulation used in 0- to 2-year-olds and 3- to 5-year-olds was palatable per child/parent and nurse/investigator reports. Data from initial phase I/II studies inform our understanding of delamanid use in children and support its further assessment in the setting of pediatric MDR-TB. (This study has been registered at ClinicalTrials.gov under identifiers NCT01856634 [phase I trial] and NCT01859923 [phase II trial].).

OUP accepted manuscript

Given the low treatment success rates of drug-resistant tuberculosis (TB), novel TB drugs are urgently needed. The landscape of TB treatment has changed considerably over the last decade with the approval of three new compounds: bedaquiline, delamanid and pretomanid. Of these, delamanid and pretomanid belong to the same class of drugs, the nitroimidazoles. In order to close the knowledge gap on how delamanid and pretomanid compare with each other, we summarize the main findings from preclinical research on these two compounds. We discuss the compound identification, mechanism of action, drug resistance, in vitro activity, in vivo pharmacokinetic profiles, and preclinical in vivo activity and efficacy. Although delamanid and pretomanid share many similarities, several differences could be identified. One finding of particular interest is that certain Mycobacterium tuberculosis isolates have been described that are resistant to either delamanid or pretomanid, but with preserved susceptibility to the other compound. This might imply that delamanid and pretomanid could replace one another in certain regimens. Regarding bactericidal activity, based on in vitro and preclinical in vivo activity, delamanid has lower MICs and higher mycobacterial load reductions at lower drug concentrations and doses compared with pretomanid. However, when comparing in vivo preclinical bactericidal activity at dose levels equivalent to currently approved clinical doses based on drug exposure, this difference in activity between the two compounds fades. However, it is important to interpret these comparative results with caution knowing the variability inherent in preclinical in vitro and in vivo models.

Improving the Drug Development Pipeline for Mycobacteria: Modelling Antibiotic Exposure in the Hollow Fibre Infection Model

Mycobacterial infections are difficult to treat, requiring a combination of drugs and lengthy treatment times, thereby presenting a substantial burden to both the patient and health services worldwide. The limited treatment options available are under threat due to the emergence of antibiotic resistance in the pathogen, hence necessitating the development of new treatment regimens. Drug development processes are lengthy, resource intensive, and high-risk, which have contributed to market failure as demonstrated by pharmaceutical companies limiting their antimicrobial drug discovery programmes. Pre-clinical protocols evaluating treatment regimens that can mimic in vivo PK/PD attributes can underpin the drug development process. The hollow fibre infection model (HFIM) allows for the pathogen to be exposed to a single or a combination of agents at concentrations achieved in vivo-in plasma or at infection sites. Samples taken from the HFIM, depending on the analyses performed, provide information on the rate of bacterial killing and the emergence of resistance. Thereby, the HFIM is an effective means to investigate the efficacy of a drug combination. Although applicable to a wide variety of infections, the complexity of anti-mycobacterial drug discovery makes the information available from the HFIM invaluable as explored in this review.

Population Pharmacokinetic and Concentration-QTc Analysis of Delamanid in Pediatric Participants with Multidrug-Resistant Tuberculosis

A population pharmacokinetic analysis of delamanid and its major metabolite DM-6705 was conducted to characterize the pharmacokinetics of delamanid and DM-6705 in pediatric participants with multidrug-resistant tuberculosis (MDR-TB). Data from participants between the ages of 0.67 and 17 years, enrolled in 2 clinical trials, were utilized for the analysis. The final data set contained 634 delamanid and 706 DM-6705 valid plasma concentrations from 37 children. A transit model with three compartments best described the absorption of delamanid. Two-compartment models for each component with linear elimination were selected to characterize the dispositions of delamanid and DM-6705, respectively. The covariates included in the model were body weight on the apparent volume of distribution and apparent clearance (for both delamanid and DM-6705); formulation (dispersible versus film-coated tablet) on the mean absorption time; age, formulation, and dose on the bioavailability of delamanid; and age on the fraction of delamanid metabolized to DM-6705. Based on the simulations, doses for participants within different age/weight groups that result in delamanid exposure comparable to that in adults following the approved adult dose were calculated. By concentration-QTc (QTcB [QT corrected by Bazett’s formula]) analysis, a significant positive correlation was detected with concentrations of DM-6705. However, the model-predicted upper bounds of the 90% confidence intervals of ΔQTc values were <10 ms at the simulated maximum concentration (C_max) of DM-6705 following the administration of the maximum doses simulated. This suggests that the effect on the QT interval following the proposed dosing is unlikely to be clinically meaningful in children with MDR-TB who receive delamanid.

Pharmacokinetics of bedaquiline, delamanid and clofazimine in patients with multidrug-resistant tuberculosis

BACKGROUND

Pharmacokinetic data are needed for newly implemented anti-tuberculosis drugs to help optimize their use.

OBJECTIVES

To help fill existing knowledge gaps, we evaluated the pharmacokinetic parameters of novel and repurposed anti-tuberculosis drugs among patients with drug-resistant pulmonary tuberculosis.

METHODS

A prospective cohort study among patients ≥16 years with confirmed pulmonary drug-resistant TB was conducted in Tbilisi, Georgia. Patients receiving bedaquiline, delamanid and/or clofazimine were included. Blood samples were collected 4-6 weeks after drug initiation, and serum concentrations were measured using validated liquid chromatography tandem mass spectrometry assays. A non-compartmental analysis was performed, and the association of exposure parameters with covariates was explored.

RESULTS

Among 99 patients, the average age and weight were 40 years and 65 kg, respectively. The median Cmin was 0.68 mg/L for bedaquiline, 0.17 mg/L for delamanid, and 0.52 mg/L for clofazimine. The median AUC0-24 was 30.6 mg·h/L for bedaquiline, 16.1 mg·h/L for clofazimine, and the AUC0-12 was 2.9 mg·h/L for delamanid. Among the significant covariates associated with drug exposure parameters were weight and sex for bedaquiline, alcohol use for delamanid, and weight for clofazimine.

CONCLUSIONS

We found a strong association of weight with bedaquiline and clofazimine exposure parameters, suggesting the need for weight-based dosing for those agents.

Population Pharmacokinetic Analysis of Delamanid in Patients with Pulmonary Multidrug-Resistant Tuberculosis

A population pharmacokinetic (PopPK) model of delamanid in patients with pulmonary multidrug-resistant tuberculosis (MDR-TB) was developed using data from four delamanid clinical trials. The final PopPK data set contained 20,483 plasma samples from 744 patients with MDR-TB receiving an optimized background regimen (OBR). Delamanid PK was adequately described for all observed dosing regimens and subpopulations by a two-compartment model with first-order elimination and absorption, an absorption lag time, and decreased relative bioavailability with increasing dose. Relative bioavailabilities of 200-mg and higher doses (250 and 300 mg) were 76% and 58% of a 100-mg dose, respectively. Relative bioavailability was 26% higher after evening doses than morning doses and 9% higher in outpatient settings than inpatient settings. The rate of absorption was higher, and lag time was shorter, following a morning dose than an evening dose. Relative bioavailabilities in patients in Northeast Asian and Southeast Asian regions were 53% and 40% higher, respectively, than in patients in non-Asian regions. Apparent clearance was higher (to the power of -0.892) in patients with hypoalbuminemia (albumin levels of <3.4 g/dl). Coadministration of efavirenz in patients with HIV increased delamanid clearance by 35%. Delamanid exposure was not affected by age (18 to 64 years), mild or moderate renal impairment, anti-TB antibiotic resistance status, HIV status, or markers of hepatic dysfunction or by concomitant administration of OBR, lamivudine, tenofovir, pyridoxine, CYP3A4 inhibitors and inducers, or antacids. Model evaluation suggested reasonable model fit and predictive power, indicating that the model should prove reliable to derive PK metrics for subsequent PK/PD analyses.