Impact of Prior Tuberculosis Treatment With New/Companion Drugs on Clinical Outcomes in Patients Receiving Concomitant Bedaquiline and Delamanid for Multidrug- and Rifampicin-Resistant Tuberculosis

BACKGROUND

There are scarce data on the clinical outcomes of persons retreated with new/companion anti-tuberculosis (TB) drugs for multidrug- and rifampicin-resistant tuberculosis (MDR/RR-TB). We sought to evaluate the efficacy and safety of bedaquiline and delamanid containing regimens among patients with and without prior exposure to the new/companion drugs (bedaquiline, delamanid, linezolid, clofazimine, and fluoroquinolones).

METHODS

We conducted a retrospective cohort study among patients with pulmonary MDR/RR-TB in Georgia who received bedaquiline and delamanid combination as a part of a salvage regimen from November 2017 to December 2020 in a programmatic setting.

RESULTS

Among 106 persons with a median age of 39.5 years, 44 (41.5%) were previously treated with new/companion TB drugs. Patients with prior exposure to new/companion drugs had higher rates of baseline resistance compared to those without exposure to new/companion TB drugs (bedaquiline 15.2% vs 1.8%, linezolid 22.2% vs 16.7%). Sputum culture conversion rates among patients exposed and not exposed to new/companion drugs were 65.9% vs 98.0%, respectively (P < .001). Among patients with and without prior new/companion TB drug use, favorable outcome rates were 41.0% and 82.3%, respectively (P < .001). Treatment adherence in 32 (30.2%) patients was ≤80%. Five of 21 patients (23.8%) who had a baseline and repeat susceptibility test had acquired bedaquiline resistance. QTC/F prolongation (>500 ms) was rare (2.8%).

CONCLUSIONS

Prior exposure to new/companion TB drugs was associated with poor clinical outcomes and acquired drug resistance. Tailoring the TB regimen to each patient's drug susceptibility test results and burden of disease and enhancing adherence support may improve outcomes.

Effectiveness and safety of regimen containing bedaquiline and delamanid in patients with drug-resistant tuberculosis

Background

Bedaquiline and delamanid have been included in the individualized treatment regimen (ITR) to treat patients with drug-resistant tuberculosis (DR-TB).

Objective

The objective of this study is to compare the effectiveness of sputum culture conversion and the safety of ITR containing bedaquiline and delamanid.

Methods

Data were collected retrospectively from medical records of DR-TB patients who received ITR between January 2020 and December 2021. Patients were divided into bedaquiline and bedaquiline-delamanid groups. Sputum culture was evaluated until 6 months of treatment. Measurement of QTc interval, renal and liver function test, and serum potassium were evaluated to assess safety during the study period. We used Chi-square to analyze a difference in cumulative culture conversion; meanwhile, Wilcoxon and Mann-Whitney tests were used to analyze differences in laboratory data for each and between the two groups, respectively.

Results

Fifty-one eligible DR-TB patients met the inclusion criteria, 41 in the bedaquiline and 10 in bedaquiline-delamanid group. 43/51 patients had a positive culture at baseline. After 6 months of treatment, 42/43 DR-TB patients (97.6%) had sputum culture conversion and no difference between the two groups (P ≥ 0.05). QTc interval within normal limit and no patient had a QTc >500 ms during the study period. Creatinine levels significantly differed between the two groups 6 months after treatment (P < 0.05).

Conclusion

DR-TB patients who received all oral ITR containing bedaquiline and or delamanid demonstrated favorable sputum conversion with a tolerable safety profile.

Loss-of-function mutations in ndh do not confer delamanid, ethionamide, isoniazid, or pretomanid resistance in Mycobacterium tuberculosis

Results from clinical strains and knockouts of the H37Rv and CDC1551 laboratory strains demonstrated that ndh (Rv1854c) is not a resistance-conferring gene for isoniazid, ethionamide, delamanid, or pretomanid in Mycobacterium tuberculosis. This difference in the susceptibility to NAD-adduct-forming drugs compared with other mycobacteria may be driven by differences in the absolute intrabacterial NADH concentration.

A four-drug standardized short regimen for highly resistant TB in South-West Nigeria

BACKGROUND

Patients with TB resistant to rifampicin (Rr-TB), and those with additional resistance to fluoroquinolones (pre-XDR-TB), should be treated with bedaquiline-pretomanid-linezolid-moxifloxacin and bedaquiline-pretomanid-linezolid, respectively. However, pretomanid is not yet widely available.

METHODS

This is a pragmatic prospective single-arm study investigating the efficacy and safety of 9 mo of bedaquiline-delamanid-linezolid-clofazimine in patients with pre-XDR-TB or Rr-TB unresponsive to Rr-TB treatment in Nigeria.

RESULTS

From January 2020 to June 2022, 14 of 20 patients (70%) successfully completed treatment, five died and one was lost-to-follow-up. No one experienced a treatment-emergent grade three/four event. Treatment success was higher compared with global pre-XDR-TB treatment outcomes.

CONCLUSIONS

While pretomanid is unavailable, highly resistant TB can be treated with bedaquiline-delamanid-linezolid-clofazimine.

Bedaquiline, Delamanid, Linezolid, Clofazimine, and Capreomycin MIC Distributions for Drug Resistance Mycobacterium tuberculosis in Shanghai, China

Background

New antituberculosis drugs have recently been approved for the treatment of multidrug-resistant tuberculosis TB (MDR-TB). We aimed to describe the distributions of bedaquiline, delamanid, linezolid, clofazimine, and capreomycin MIC values for M. tuberculosis.

Methods

M. tuberculosis clinical isolates were originally isolated from 2020 to 2021 from 1452 different pulmonary tuberculosis patients of the Shanghai Pulmonary Hospital in China. The drug susceptibility testing was performed using the Sensititre custom plates (SHTBMY) (TREK Diagnostic Systems, Thermo Fisher Scientific In., USA) consisting of a 96-well microtitre plate containing 4 (bedaquiline, delamanid, clofazimine, capreomycin) antimicrobial agents. MICs were determined for linezolid using a microdilution method.

Results

Based on the latest definitions, 156 (10.74%) were MDR-TB, 93 (6.40%) were pre-XDR-TB, and 27 (1.86%) were XDR-TB. The rate of BDQ resistance in cases of MDR-TB was 7.69%, while it was observed to be 10.75% in cases of pre-XDR-TB, and significantly higher at 37.04% in cases of XDR-TB. The lowest rate of drug resistance against M. tuberculosis was DLM (0.14%). For LZD, 11 (0.76%) clinical isolates were resistant, based on the CLSI breakpoint of 1μg/mL. The five strains with a MIC value of >32 for LZD resistance were XDR-TB isolates. Among all MDR, pre-XDR, and XDR isolates tested, LZD' MIC50 increased from 0.25 and 0.5 to 1μg/mL. The MIC90 value of LZD against XDR-TB isolates was 32μg/mL. For CFZ, six isolates with elevated MICs of ≥2μg/mL. CFZ's MIC50 and MIC90 values in all isolates were 0.12μg/mL and 0.25μg/mL, respectively.

Conclusion

The study findings indicate that BDQ, DLM, CFZ, and LZD may exhibited excellent in vitro activity against MDR-TB isolates. Detection of resistance to BDQ and LZD was alarming for XDR-TB isolates. It is necessary to perform universal drug sensitivity testing for M. tuberculosis, especially MDR-TB and XDR-TB patients.

Tuberculosis in Spain: An opinion paper

This document is the result of the deliberations of the Committee on Emerging Pathogens and COVID-19 of the Illustrious Official College of Physicians of Madrid (ICOMEM) regarding the current situation of tuberculosis, particularly in Spain. We have reviewed aspects such as the evolution of its incidence, the populations currently most exposed and the health care circuits for the care of these patients in Spain. We have also discussed latent tuberculosis, the reality of extrapulmonary disease in the XXI century and the means available in daily practice for the diagnosis of both latent and active forms. The contribution of molecular biology, which has changed the perspective of this disease, was another topic of discussion. The paper tries to put into perspective both the classical drugs and their resistance figures and the availability and indications of the new ones. In addition, the reality of direct observation in the administration of antituberculosis drugs has been discussed. All this revolution is making it possible to shorten the treatment time for tuberculosis, a subject that has also been reviewed. If everything is done well, the risk of relapse of tuberculosis is small but it exists. On the other hand, many special situations have been discussed in this paper, such as tuberculosis in pediatric age and tuberculosis as a cause for concern in surgery and intensive care. The status of the BCG vaccine and its present indications as well as the future of new vaccines to achieve the old dream of eradicating this disease have been discussed. Finally, the ethical and medicolegal implications of this disease are not a minor issue and our situation in this regard has been reviewed.

A Single-Run HPLC-MS Multiplex Assay for Therapeutic Drug Monitoring of Relevant First- and Second-Line Antibiotics in the Treatment of Drug-Resistant Tuberculosis

The treatment of drug-resistant Mycobacterium tuberculosis relies on complex antibiotic therapy. Inadequate antibiotic exposure can lead to treatment failure, acquired drug resistance, and an increased risk of adverse events. Therapeutic drug monitoring (TDM) can be used to optimize the antibiotic exposure. Therefore, we aimed to develop a single-run multiplex assay using high-performance liquid chromatography-mass spectrometry (HPLC-MS) for TDM of patients with multidrug-resistant, pre-extensively drug-resistant and extensively drug-resistant tuberculosis. A target profile for sufficient performance, based on the intended clinical application, was established and the assay was developed accordingly. Antibiotics were analyzed on a zwitterionic hydrophilic interaction liquid chromatography column and a triple quadrupole mass spectrometer using stable isotope-labeled internal standards. The assay was sufficiently sensitive to monitor drug concentrations over five half-lives for rifampicin, rifabutin, levofloxacin, moxifloxacin, bedaquiline, linezolid, clofazimine, terizidone/cycloserine, ethambutol, delamanid, pyrazinamide, meropenem, prothionamide, and para-amino salicylic acid (PAS). Accuracy and precision were sufficient to support clinical decision making (≤±15% in clinical samples and ±20-25% in spiked samples, with 80% of future measured concentrations predicted to fall within ±40% of nominal concentrations). The method was applied in the TDM of two patients with complex drug-resistant tuberculosis. All relevant antibiotics from their regimens could be quantified and high-dose therapy was initiated, followed by microbiological conversion. In conclusion, we developed a multiplex assay that enables TDM of the relevant first- and second-line anti-tuberculosis medicines in a single run and was able to show its applicability in TDM of two drug-resistant tuberculosis patients.

Evaluation of 2,3-dihydroimidazo[2,1-b]oxazole and imidazo[2,1-b]oxazole derivatives as chemotherapeutic agents

Imidazo[2,1-b]oxazole and 2,3-dihydroimidazo[2,1-b]oxazole ring systems are commonly employed in therapeutically active molecules. In this article, the authors review the utilization of these core scaffolds as chemotherapeutic agents from 2018 to 2022. These scaffolds possess many important biological activities including antimicrobial and anticancer, among others. This review covers their biological activities and structure-activity relationships. One of the most important drugs in this class of compounds is the antitubercular agent delamanid. In this paper, the compounds structure-activity relationship and preclinical and clinical trial data are thoroughly presented.

Advances of new drugs bedaquiline and delamanid in the treatment of multi-drug resistant tuberculosis in children

Tuberculosis (TB) is a major public health problem, with nearly 10 million new cases and millions of deaths each year. Around 10% of these cases are in children, but only a fraction receive proper diagnosis and treatment. The spread of drug-resistant (DR) strain of TB has made it difficult to control, with only 60% of patients responding to treatment. Multi-drug resistant TB (MDR-TB) is often undiagnosed in children due to lack of awareness or under-diagnosis, and the target for children's DR-TB treatment has only been met in 15% of goals. New medications such as bedaquiline and delamanid have been approved for treating DR-TB. However, due to age and weight differences, adults and children require different dosages. The availability of child-friendly formulations is limited by a lack of clinical data in children. This paper reviews the development history of these drugs, their mechanism of action, efficacy, safety potential problems and current use in treating DR-TB in children.

Enteric coating of tablets containing an amorphous solid dispersion of an enteric polymer and a weakly basic drug: a strategy to enhance in vitro release

Recent work has highlighted that amorphous solid dispersions (ASDs) containing delamanid (DLM) and an enteric polymer, hypromellose phthalate (HPMCP), appear to be susceptible to crystallization during immersion in simulated gastric fluids. The goal of this study was to minimize contact of the ASD particles with the acidic media via application of an enteric coating to tablets containing the ASD intermediate, and improve the subsequent drug release at higher pH conditions. DLM ASDs were prepared with HPMCP and formulated into a tablet that was then coated with a methacrylic acid copolymer (Acryl EZE II®). Drug release was studied in vitro using a two-stage dissolution test where the pH of the gastric compartment was altered to reflect physiological variations. The medium was subsequently switched to simulated intestinal fluid. The gastric resistance time of the enteric coating was probed over the pH range of 1.6-5.0. The enteric coating was found to be effective at protecting the drug against crystallization in pH conditions where HPMCP was insoluble. Consequently, the variability in drug release following gastric immersion under pH conditions reflecting different prandial states was notably reduced when compared to the reference product. These findings support closer examination of the potential for drug crystallization from ASDs in the gastric environment where acid-insoluble polymers may be less effective as crystallization inhibitors. Further, addition of a protective enteric coating appears to provide a promising remediation strategy to prevent crystallization at low pH environments, and may mitigate variability associated with prandial state that arises due to pH changes.

Therapeutic Failure and Acquired Bedaquiline and Delamanid Resistance in Treatment of Drug-Resistant TB

New classes of antitubercular drugs, diarylquinolines and nitroimidazoles, have been associated with improved outcomes in the treatment of drug-resistant tuberculosis, but that success is threatened by emerging drug resistance. We report a case of bedaquiline and delamanid resistance in a 55-year-old woman in South Africa with extensively drug-resistant tuberculosis and known HIV.

MDR-TB in children: are the same therapy options available worldwide?

The spread of drug-resistant tuberculosis (TB) encouraged the development of new medicines and the reappraisal of old drugs rarely used in recent years. Providing access for children with drug-resistant TB to appropriate treatments is a cornerstone of strategies to reduce the burden of TB worldwide. Aim of this perspective is to describe the availability of child-friendly medicines to treat drug-resistant TB at the global level. We showed that the development of child-friendly formulations of second-line drugs should be encouraged to promote adherence to recommended treatment regimens and consequently to increase the success rate and to prevent the development of additional mycobacterial resistances. This is even more crucial considering the long duration of anti-tubercular therapies. Importantly, companies and policy-makers are called to more efforts in facilitating their prompt availability in every contest, as drug-resistant pediatric TB is a global medical problem.

Solubility Enhancement and Inhalation Delivery of Cyclodextrin-Based Inclusion Complex of Delamanid for Pulmonary Tuberculosis Treatment

Tuberculosis (TB) is a contiguous airborne disease caused by Mycobacterium tuberculosis (M.tb), primarily affecting the human lungs. The progression of drug-susceptible TB to drug-resistant strains, MDR-TB and XDR-TB, has become a global challenge toward eradicating TB. Conventional TB treatment involves frequent dosing and prolonged treatment regimens predominantly by an oral or invasive route, leading to treatment-related systemic adverse effects and patient's noncompliance. Pulmonary delivery is an attractive option as we could reduce dose, limit systemic side-effects, and achieve rapid onset of action. Delamanid (DLD), an antituberculosis drug, has poor aqueous solubility, and in this study, we aim to improve its solubility using cyclodextrin complexation. We screened different cyclodextrins and found that HP-β-CD resulted in a 54-fold increase in solubility compared to a 27-fold and 13-fold increase by SBE-β-CD and HP-ɣ-CD, respectively. The stability constant (265 ± 15 M^-1) and complexation efficiency (8.5 × 10^-4) suggest the formation of a stable inclusion complex of DLD and HP-β-CD in a 2:1 ratio. Solid-state characterization studies (DSC, PXRD, and NMR) further confirmed successful complexation of DLD in HP-β-CD. The nebulized DLD-CD complex solution showed a mass median aerodynamic diameter of 4.42 ± 0.62 μm and fine particle fraction of 82.28 ± 2.79%, suggesting deposition in the respiratory airways. In bacterial studies, minimum inhibitory concentration of DLD-CD complex was significantly reduced (four-fold) compared to free DLD in M.tb (H37Ra strain). Furthermore, accelerated stability studies confirmed that the inclusion complex was stable for 4 weeks with 90%w/w drug content. In conclusion, we increased the aqueous solubility of DLD through cyclodextrin complexation and improved its efficacy in vitro.

Relative bioavailability of delamanid 50 mg tablets dispersed in water in healthy adult volunteers

AIM

Delamanid is a novel drug for the treatment of drug-resistant tuberculosis, manufactured as 50-mg solid and 25-mg dispersible tablets. We evaluated the effects of dispersing the 50-mg tablet, focusing on the relative bioavailability.

METHODS

Delamanid, 50-mg tablets administered dispersed vs swallowed whole, was investigated in a phase I, four-period, crossover study. Two of three dose strengths of delamanid (25, 50 or 100 mg) were given to healthy adult participants, in both whole and dispersed forms, with a 7-day washout period. Blood samples were collected over 168 h after each dose. Delamanid and its metabolite DM-6705 were analysed with a validated liquid chromatography tandem mass spectrometry assay. The pharmacokinetics of both analytes were analysed using nonlinear mixed-effect modelling. Palatability and acceptability were determined using a standardized questionnaire.

RESULTS

Twenty-four participants completed the study. The bioavailability of dispersed tablets was estimated to be 107% of whole tablets, with a 90% confidence interval of 99.7-114%, fulfilling bioequivalence criteria. The two formulations were not significantly different regarding either bioavailability or its variability. Bioavailability increased at lower doses, by 34% (26-42%) at 50 mg and by 74% (64-86%) at 25 mg, relative to 100 mg. The majority of participants (93%) found the dispersed formulation acceptable in palatability across all delamanid doses.

CONCLUSIONS

Dispersed 50-mg delamanid tablets have similar bioavailability to tablets swallowed whole in adult volunteers. This can be an option for children and other patients who cannot swallow whole tablets, improving access to treatment.

Favorable outcome of individual regimens containing bedaquiline and delamanid in drug-resistant tuberculosis: A systematic review

Background

Drug-resistant tuberculosis (DR-TB) is a public health concern that is difficult to treat, requiring long and complex treatment with highly effective drugs. Bedaquiline and/or delamanid have already shown promising outcomes in patients with DR-TB, increasing the rate of culture conversion and lowering TB-related mortality.

Methods

We comprehensively searched and evaluated the effectiveness of individual regimens containing bedaquiline and delamanid on culture conversion and treatment success. We assessed for quality either observational or experimental studies.

Results

We identified 14 studies that met the inclusion criteria using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses flowchart with 12 observational and 2 experimental studies. Of 1691 DR-TB patients enrolled in the included studies, 1407 of them concomitantly received regimens containing bedaquiline and delamanid. Overall multidrug resistant (MDR), preextensively drug resistant (XDR), and XDR-TB were seen in 21.4%, 44.1%, and 34.5%, respectively. Of 14 studies, 8 of them reported favorable outcomes including sputum culture conversion and cure rate at the end of treatment, meanwhile 6 studies only reported sputum culture conversion. Sputum culture conversion at the end of the 6^th month was 63.6%-94.7% for observational studies, and 87.6%-95.0% for experimental studies. The favorable outcome at the end of treatment was 67.5%-91.4%. With high pre-XDR and XDR cases among DR-TB patients with limited treatment options, regimens containing bedaquiline and delamanid provide successful treatment.

Conclusion

In DR-TB patients receiving regimens containing bedaquiline and delamanid, favorable outcomes were high including sputum conversion and cure rate.

Treatment options for children with multi-drug resistant tuberculosis

INTRODUCTION

According to the latest report from the World Health Organization (WHO), approximately 10.0 million people fell ill with tuberculosis (TB) in 2020, 12% of which were children aged under 15 years. There is very few experience on treatment of multi-drug resistant (MDR)-TB in pediatrics.

AREAS COVERED

The aim of this review is to analyze and summarize therapeutic options available for children experiencing MDR-TB. We also focused on management of MDR-TB prophylaxis.

EXPERT OPINION

The therapeutic management of children with MDR-TB or MDR-TB contacts is complicated by a lack of knowledge, and the fact that many potentially useful drugs are not registered for pediatric use and there are no formulations suitable for children in the first years of life. Furthermore, most of the available drugs are burdened by major adverse events that need to be taken into account, particularly in the case of prolonged therapy. A close follow-up with a standardized timeline and a comprehensive assessment of clinical, laboratory, microbiologic and radiologic data is extremely important in these patients. Due to the complexity of their management, pediatric patients with confirmed or suspected MDR-TB should always be referred to a specialized center.

The ddn Trp20Stop Mutation and Its Association with Lineage 4.5 and Resistance to Delamanid and Pretomanid in Mycobacterium tuberculosis

High-confidence resistance mutations for new and repurposed anti-TB drugs, such as delamanid (DLM) and pretomanid (Pa), are rare and more data are needed in order to correctly interpret the results generated by genotypic drug susceptibility testing. In this study performed on clinical Mycobacterium tuberculosis complex isolates, we report that in the Swedish strain collection the ddn mutation Trp20Stop is found exclusively among DLM and Pa resistant (Pa MIC >16 mg/L) isolates assigned to lineage 4.5.

Spontaneous Mutational Patterns and Novel Mutations for Delamanid Resistance in Mycobacterium tuberculosis

Delamanid (DLM) and pretomanid (PTM) are recent additions to the anti-tuberculosis (TB) drug armamentarium, and they offer more effective options for drug-resistant TB treatment. In particular, DLM is included in Group C, which is recommended for use in longer multidrug-resistant (MDR)-TB regimens. Previous studies have shown that resistance to DLM/PTM is caused by mutations in the ddn, fgd1, fbiA, fbiB, fbiC, and fbiD genes, which are related to the F₄₂₀-dependent bioactivation pathway. Herein, we conduct in vitro selection of DLM-resistant strains using clinical Mycobacterium tuberculosis (MTB) isolates with various drug resistance profiles. The spontaneous resistance frequency of drug-susceptible (DS) MTB (1.14 × 10^-6 to 1.04 × 10^-4) to DLM was similar to that of H37Rv (8.88 × 10^-6 to 9.96 × 10^-6) but higher than those of multidrug-resistant MTB (2.03 × 10^-7 to 3.18 × 10^-6) and extensively drug-resistant (XDR) MTB (4.67 × 10^-8 to 3.60 × 10^-6). Of the 100 independently selected DLM-resistant MTB mutants, 65% harbored mutations in genes associated with either DLM prodrug activation (ddn, 39.73%; fgd1, 16.44%) or the F₄₂₀ biosynthetic pathway (fbiA, 16.44%; fbiB, 5.48%; fbiC, 21.92%). Of the 45 mutations we identified, 38 were not previously reported. A structure analysis revealed that several point mutations affected the ligand binding or structural stability of enzymes related to DLM resistance, which would block the enzyme activity required for prodrug activation. Our results elucidate the in vitro spontaneous DLM-resistance patterns of different clinical strains, which could improve the understanding of the causes of DLM resistance in clinical strains and of the effects on drug resistance of different mutations in genes that are related to the DLM activation pathway.

Delamanid-containing regimens and multidrug-resistant tuberculosis: A systematic review and meta-analysis

INTRODUCTION

Multidrug-resistant tuberculosis (MDR-TB) is a life-threatening condition needing long poly-chemotherapy regimens. As no systematic reviews/meta-analysis is available to comprehensively evaluate the role of delamanid (DLM), we evaluated its effectiveness and safety.

METHODS

We reviewed the relevant scientific literature published up to January 20, 2022. The pooled success treatment rate with 95% confidence intervals (CI) was assessed using a random-effect model. We assessed studies for quality and bias, and considered P<0.05 to be statistically significant.

RESULTS

After reviewing 626 records, we identified 25 studies that met the inclusion criteria, 22 observational and 3 experimental, with 1276 and 411 patients, respectively. In observational studies the overall pooled treatment success rate of DLM-containing regimens was 80.9% (95% CI 72.6-87.2) with no evidence of publication bias (Begg's test; P >0.05). The overall pooled treatment success rate in DLM and bedaquiline-containing regimens was 75.2% (95% CI 68.1-81.1) with no evidence of publication bias (Begg's test; P >0.05). In experimental studies the pooled treatment success rate of DLM-containing regimens was 72.5 (95% CI 44.2-89.8, P <0.001, I²: 95.1%) with no evidence of publication bias (Begg's test; P >0.05).

CONCLUSIONS

In MDR-TB patients receiving DLM, culture conversion and treatment success rates were high despite extensive resistance with limited adverse events.

Scoping review: QT interval prolongation in regimen containing bedaquiline and delamanid in patients with drug-resistant tuberculosis

Background

A regimen containing bedaquiline-delamanid is recommended in management of drug-resistant tuberculosis (DR TB) to increase a success rate. However, this regimen was rare in a clinical setting due to a potential risk of QT prolongation. Several studies have reported the incidence of QT prolongation after administration of this regimen, but the results are inconsistent due to different sample size, study design, and covariate. The aim of this review is to summarize and analyze the published articles related to QT prolongation of bedaquiline and delamanid in PubMed and ScienceDirect databases using a scoping review.

Methods

This scoping review was conducted under PRISMA for scoping review. The outcomes of this review were incidence of QT prolongation and death. We found 8 articles to be included in this review.

Results

The incidence of QT prolongation was higher for DR TB patients who received a regimen containing bedaquiline and delamanid. However, this review found no clinical symptoms, such as cardiac arrhythmias, torsade de pointes, or even death. DR TB patients, especially the elderly, were at risk for QT prolongation. Special consideration in patients with HIV and low level of potassium should be closely monitored for QT interval.

Conclusion

The regular measurement of electrocardiography was highly recommended to evaluate QT interval. Generally, the use of individualized regimen containing bedaquiline and delamanid is relatively safe in DR TB patients.

Molecular dynamic assisted investigation on impact of mutations in deazaflavin dependent nitroreductase against pretomanid: a computational study

In the past decade, TB drugs belonging to the nitroimidazole class, pretomanid and delamanid, have been authorised to treat MDR-TB and XDR-TB. With a novel inhibition mechanism and a reduction in the span of treatment, it is now being administered in various combinations. This approach is not the ultimate remedy since the target protein Deazaflavin dependent nitroreductase (Ddn) has a high mutation frequency, and already pretomanid resistant clinical isolates are reported in various studies. Ddn is essential for M.tuberculosis to emerge from hypoxia, and point mutations in critical residues confer resistance to Nitro-imidazoles. Among the pool of available mutants, we have selected seven mutants viz Ddn^L49P, Ddn^Y65S, Ddn^S78Y, Ddn^K79Q, Ddn^W88R, Ddn^Y133C, and Ddn^Y136S, all of which exhibited resistance to pretomanid. To address this issue, through computational study primarily by MD simulation, we attempted to elucidate these point mutations' impact and investigate the resistance mechanism. Hence, the Ddn^WT and mutant (MT) complexes were subjected to all-atom molecular dynamics (MD) simulations for 100 ns. Interestingly, we observed the escalation of the distance between cofactor and ligand in some mutants, along with a significant change in ligand conformation relative to the Ddn^WT. Moreover, we confirmed that mutations rendered ligand instability and were ejected from the binding pocket as a result. In conclusion, the results obtained provide a new structural insight and vital clues for designing novel inhibitors to combat nitroimidazole resistanceCommunicated by Ramaswamy H. Sarma.

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].).

Novel Regimens of Bedaquiline-Pyrazinamide Combined with Moxifloxacin, Rifabutin, Delamanid and/or OPC-167832 in Murine Tuberculosis Models

A recent landmark trial showed a 4-month regimen of rifapentine, pyrazinamide, moxifloxacin, and isoniazid (PZMH) to be noninferior to the 6-month standard of care. Here, two murine models of tuberculosis were used to test whether novel regimens replacing rifapentine and isoniazid with bedaquiline and another drug would maintain or increase the sterilizing activity of the regimen. In BALB/c mice, replacing rifapentine in the PZM backbone with bedaquiline (i.e., BZM) significantly reduced both lung CFU counts after 1 month and the proportion of mice relapsing within 3 months after completing 1.5 months of treatment. The addition of rifabutin to BZM (BZMRb) further increased the sterilizing activity. In the C3HeB/FeJ mouse model characterized by caseating lung lesions, treatment with BZMRb resulted in significantly fewer relapses than PZMH after 2 months of treatment. A regimen combining the new DprE1 inhibitor OPC-167832 and delamanid (BZOD) also had superior bactericidal and sterilizing activity compared to PZM in BALB/c mice and was similar in efficacy to PZMH in C3HeB/FeJ mice. Thus, BZM represents a promising backbone for treatment-shortening regimens. Given the prohibitive drug-drug interactions between bedaquiline and rifampin or rifapentine, the BZMRb regimen represents the best opportunity to combine, in one regimen, the treatment-shortening potential of the rifamycin class with that of BZM and deserves high priority for evaluation in clinical trials. Other 4-drug BZM-based regimens and BZOD represent promising opportunities for extending the spectrum of treatment-shortening regimens to rifamycin- and fluoroquinolone-resistant tuberculosis.

Early mortality during rifampicin-resistant TB treatment

BACKGROUND: Data suggest that treatment with newer TB drugs (linezolid [LZD], bedaquiline [BDQ] and delamanid [DLM]), used in Khayelitsha, South Africa, since 2012, reduces mortality due to rifampicin-resistant TB (RR-TB).METHODS: This was a retrospective cohort study to assess 6-month mortality among RR-TB patients diagnosed between 2008 and 2019.RESULTS: By 6 months, 236/2,008 (12%) patients died; 12% (78/651) among those diagnosed in 2008-2011, and respectively 8% (49/619) and 15% (109/738) with and without LZD/BDQ/DLM in 2012-2019. Multivariable analysis showed a small, non-significant mortality reduction with LZD/BDQ/DLM use compared to the 2008-2011 period (aOR 0.79, 95% CI 0.5-1.2). Inpatient treatment initiation (aOR 3.2, 95% CI 2.4-4.4), fluoroquinolone (FQ) resistance (aOR 2.7, 95% CI 1.8-4.2) and female sex (aOR 1.5, 95% CI 1.1-2.0) were also associated with mortality. When restricted to 2012-2019, use of LZD/BDQ/DLM was associated with lower mortality (aOR 0.58, 95% CI 0.39-0.87).CONCLUSIONS: While LZD/BDQ/DLM reduced 6-month mortality between 2012 and 2019, there was no significant effect overall. These findings may be due to initially restricted LZD/BDQ/DLM use for those with high-level resistance or treatment failure. Additional contributors include increased treatment initiation among individuals who would have otherwise died before treatment due to universal drug susceptibility testing from 2012, an effect that also likely contributed to higher mortality among females (survival through to care-seeking).

Mechanism of Action, Resistance, Synergism, and Clinical Implications of Delamanid Against Multidrug-Resistant Mycobacterium tuberculosis

Multidrug-resistant (MDR) isolates of Mycobacterium tuberculosis (MTB) remain a primary global threat to the end of tuberculosis (TB) era. Delamanid (DLM) is a nitro-dihydro-imidazooxazole derivative utilized to treat MDR-TB. DLM has distinct mechanism of action, inhibiting methoxy- and keto-mycolic acid (MA) synthesis through the F420 coenzyme mycobacteria system and generating nitrous oxide. While DLM resistance among MTB strains is uncommon, there are increasing reports in Asia and Europe, and such resistance will prolong the treatment courses of patients infected with MDR-TB. In this review, we address the antimycobacterial properties of DLM, report the global prevalence of DLM resistance, discuss the synergism of DLM with other anti-TB drugs, and evaluate the documented clinical trials to provide new insights into the clinical use of this antibiotic.

The pharmacotherapeutic management of pulmonary tuberculosis: an update of the state-of-the-art

INTRODUCTION

Pulmonary tuberculosis (TB) remains an important global health challenge of the 21st century, and the emerging resistance against anti-TB drugs is still a growing concern. And while there was a significant cumulative reduction in the incidence of TB between 2015 and 2019, 2.8% of all TB cases in 2019 were reported to be drug resistant.

AREA COVERED

This review provides the reader with an update on pharmacotherapy for patients with TB susceptible or resistant to drug therapy. The authors also include promising investigational drugs herein. Finally, the authors share with the reader their expert opinions on the current state of the art and their future perspectives.

EXPERT OPINION

The current pharmacotherapeutic management aims to enhance favorable treatment outcomes and reduce treatment-related adverse events. One approach is to use shorter and all-oral regimens for eligible patients. Traditional longer regimens for most patients are also optimized to lower incidence of treatment failure and serious adverse events.

Prediction of Human Pharmacokinetic Profiles of the Antituberculosis Drug Delamanid from Nonclinical Data: Potential Therapeutic Value against Extrapulmonary Tuberculosis

Delamanid has been studied extensively and approved for the treatment of pulmonary multidrug-resistant tuberculosis; however, its potential in the treatment of extrapulmonary tuberculosis remains unknown. We previously reported that, in rats, delamanid was broadly distributed to various tissues in addition to the lungs. In this study, we simulated human plasma concentration-time courses (pharmacokinetic profile) of delamanid, which has a unique property of metabolism by albumin, using two different approaches (steady-state concentration of plasma-mean residence time [C_ss-MRT] and physiologically based pharmacokinetic [PBPK] modeling). In C_ss-MRT, allometric scaling predicted the distribution volume at steady state based on data from mice, rats, and dogs. Total clearance was predicted by in vitro-in vivo extrapolation using a scaled albumin amount. A simulated human pharmacokinetic profile using a combination of human-predicted C_ss and MRT was almost identical to the observed profile after single oral administration, which suggests that the pharmacokinetic profile of delamanid could be predicted by allometric scaling from these animals and metabolic capacity in vitro. The PBPK model was constructed on the assumption that delamanid was metabolized by albumin in circulating plasma and tissues, to which the simulated pharmacokinetic profile was consistent. Moreover, the PBPK modeling approach demonstrated that the simulated concentrations of delamanid at steady state in the lung, brain, liver, and heart were higher than the in vivo effective concentration for Mycobacterium tuberculosis. These results indicate that delamanid may achieve similar concentrations in various organs to that of the lung and may have the potential to treat extrapulmonary tuberculosis.

QT effects of bedaquiline, delamanid, or both in patients with rifampicin-resistant tuberculosis: a phase 2, open-label, randomised, controlled trial

BACKGROUND

Bedaquiline and delamanid are the first drugs of new classes registered for tuberculosis treatment in 40 years. Each can prolong the QTc interval, with maximum effects occurring weeks after drug initiation. The cardiac safety and microbiological activity of these drugs when co-administered are not well-established. Our aim was to characterise the effects of bedaquiline, delamanid, or both on the QTc interval, longitudinally over 6 months of multidrug treatment, among patients with multidrug-resistant or rifampicin-resistant tuberculosis taking multidrug background therapy.

METHODS

ACTG A5343 is a phase 2, open-label, randomised, controlled trial in which adults with multidrug-resistant or rifampicin-resistant tuberculosis receiving multidrug background treatment were randomly assigned 1:1:1 by centrally, computer-generated randomisation, by means of permuted blocks to receive bedaquiline, delamanid, or both for 24 weeks. Participants were enrolled at TASK in Cape Town and the South African Tuberculosis Vaccine Initiative in Worcester, both in South Africa, and Hospital Maria Auxiliadora in Peru. Individuals with QTc greater than 450 ms were excluded. HIV-positive participants received dolutegravir-based antiretroviral therapy. Clofazimine was disallowed, and levofloxacin replaced moxifloxacin. ECG in triplicate and sputum cultures were done fortnightly. The primary endpoint was mean QTcF change from baseline (averaged over weeks 8-24); cumulative culture conversation at week 8-24 was an exploratory endpoint. Analyses included all participants who initiated study tuberculosis treatment (modified intention-to-treat population). This trial is registered with ClinicalTrials.gov, NCT02583048 and is ongoing.

FINDINGS

Between Aug 26, 2016 and July 13, 2018, of 174 screened, 84 participants (28 in each treatment group, and 31 in total with HIV) were enrolled. Two participants did not initiate study treatment (one in the delamanid group withdrew consent and one in the bedaquiline plus delamanid group) did not meet the eligibility criterion). Mean change in QTc from baseline was 12·3 ms (95% CI 7·8-16·7; bedaquiline), 8·6 ms (4·0-13·1; delamanid), and 20·7 ms (16·1-25·3) (bedaquiline plus delamanid). There were no grade 3 or 4 adverse QTc prolongation events and no deaths during study treatment. Cumulative culture conversion by week 8 was 21 (88%) of 24 (95% CI 71-97; bedaquiline), 20 (83%) of 24 (65-95; delamanid), and 19 (95%) of 20 (79-100; bedaquiline plus delamanid) and was 92% (77-99) for bedaquiline, 91% (76-99), for delamanid, and 95% (79-100) for bedaquiline plus delamanid at 24 weeks.

INTERPRETATION

Combining bedaquiline and delamanid has a modest, no more than additive, effect on the QTc interval, and initial microbiology data are encouraging. This study provides supportive evidence for use of these agents together in patients with multidrug-resistant or rifampicin-resistant tuberculosis with normal baseline QTc values.

FUNDING

Division of AIDS, National Institutes of Health.

Treatment of Multidrug-Resistant and Extensively Drug-Resistant Tuberculosis in Children: The Role of Bedaquiline and Delamanid

Multidrug-resistant (MDR) tuberculosis (TB) has been emerging at an alarming rate over the last few years. It has been estimated that about 3% of all pediatric TB is MDR, meaning about 30,000 cases each year. Although most children with MDR-TB can be successfully treated, up to five years ago effective treatment was associated with a high incidence of severe adverse effects and patients with extensively drug-resistant (XDR) TB had limited treatment options and no standard regimen. The main objective of this manuscript is to discuss our present knowledge of the management of MDR- and XDR-TB in children, focusing on the characteristics and available evidence on the use of two promising new drugs: bedaquiline and delamanid. PubMed was used to search for all of the studies published up to November 2020 using key words such as "bedaquiline" and "delamanid" and "children" and "multidrug-resistant tuberculosis" and "extensively drug-resistant tuberculosis". The search was limited to articles published in English and providing evidence-based data. Although data on pediatric population are limited and more studies are needed to confirm the efficacy and safety of bedaquiline and delamanid, their use in children with MDR-TB/XDR-TB appears to have good tolerability and efficacy. However, more evidence on these new anti-TB drugs is needed to better guide their use in children in order to design effective shorter regimens and reduce adverse effects, drug interactions, and therapeutic failure.

Outcomes of Children Born to Pregnant Women With Drug-resistant Tuberculosis Treated With Novel Drugs in Khayelitsha, South Africa: A Report of Five Patients

This brief report presents a series of 5 pregnant women treated for rifampicin-resistant tuberculosis with the novel drugs bedaquiline, delamanid, and linezolid as part of an optimized backbone regimen and reviews the outcomes of the children born to them. Although the case series is small, all children had excellent birth outcomes suggesting pregnant women should not be denied access to novel therapies for RR-TB.

Delamanid Resistance: Update and Clinical Management

Delamanid, a-first-in-class bicyclic nitroimidazole, was recently approved for multidrug-resistant tuberculosis treatment. Pitted against the hope for improving treatment outcomes is the threat of the rapid resistance emergence. This review provides information on the mechanisms of action, resistance emergence, and drug susceptibility testing (DST) for delamanid. Delamanid resistance has already been reported in both in vitro experiments and clinical settings. Although mutations conferring delamanid resistance have been identified in fbiA, fbiB, fbiC, ddn, and fgd1 genes of Mycobacterium tuberculosis, knowledge about the molecular resistance mechanisms is limited, and there remains no standardized DST method. The rapid acquisition of delamanid resistance emphasizes the need for optimal use of new drugs, the need for drug resistance surveillance, and a comprehensive understanding of drug resistance mechanisms. Further studies are necessary to investigate genetic and phenotypic changes that determine clinically relevant delamanid resistance to help develop a rapid delamanid DST.

Radical Releasing Anti-Tuberculosis Agents and the Treatment of Mycobacterial Tuberculosis Infections - An Overview

The treatment and management of tuberculosis (TB) is a major global concern. Approved drugs for the treatment of TB to date displayed various modes of action which can be grouped into radical releasing and non-radical releasing anti TB agents. Radical releasing agents are of special interest because they diffuse directly into the mycobacterium cell wall, interact with the host cell DNA causing DNA strand breakages and fatal destabilization of the DNA helix inhibiting nucleic acid synthase. As a therapeutic agent with aforementioned activity, nitroimidazoles and most especially bicyclic nitroimidazoles are currently in clinical use for the treatment of tuberculosis. However, the approved drugs, pretomanid (PR) and delamanid (DE) are limited in their nitric oxide radical (NO•) releasing abilities to cause effective bactericidity. It is believed that their bactericidal activity can be improved by harnessing alternative strategies to increase NO• release. The last decade has witness the strategic inclusion of NO-donors into native drugs to improve their activities and/or reverse resistance. The rationale behind this strategy is the targeting of NO• release at specific therapeutic sites. This review therefore aims to highlight various radical releasing agents that may be effective in the treatment of TB. The review also investigates various structural modification to PR and DE and suggests alternative strategies to improve NO• release as well as some applications where NO-donor hybrid drugs have been used with good therapeutic effect.

The Prospective Synergy of Antitubercular Drugs With NAD Biosynthesis Inhibitors

Given the upsurge of drug-resistant tuberculosis worldwide, there is much focus on developing novel drug combinations allowing shorter treatment duration and a lower toxicity profile. Nicotinamide adenine dinucleotide (NAD) biosynthesis targeting is acknowledged as a promising strategy to combat drug-susceptible, drug-resistant, and latent tuberculosis (TB) infections. In this review, we describe the potential synergy of NAD biosynthesis inhibitors with several TB-drugs in prospective novel combination therapy. Despite not directly targeting the essential NAD cofactor's biosynthesis, several TB prodrugs either require a NAD biosynthesis enzyme to be activated or form a toxic chemical adduct with NAD(H) itself. For example, pyrazinamide requires the action of nicotinamidase (PncA), often referred to as pyrazinamidase, to be converted into its active form. PncA is an essential player in NAD salvage and recycling. Since most pyrazinamide-resistant strains are PncA-defective, a combination with downstream NAD-blocking molecules may enhance pyrazinamide activity and possibly overcome the resistance mechanism. Isoniazid, ethionamide, and delamanid form NAD adducts in their active form, partly perturbing the redox cofactor metabolism. Indeed, NAD depletion has been observed in Mycobacterium tuberculosis (Mtb) during isoniazid treatment, and activation of the intracellular NAD phosphorylase MbcT toxin potentiates its effect. Due to the NAD cofactor's crucial role in cellular energy production, additional synergistic correlations of NAD biosynthesis blockade can be envisioned with bedaquiline and other drugs targeting energy-metabolism in mycobacteria. In conclusion, future strategies targeting NAD metabolism in Mtb should consider its potential synergy with current and other forthcoming TB-drugs.

Treatment Outcomes Among Pediatric Patients With Highly Drug-Resistant Tuberculosis: The Role of New and Repurposed Second-Line Tuberculosis Drugs

BACKGROUND

Among pediatric patients with multidrug-resistant tuberculosis (MDR-TB), limited data exist regarding treatment outcomes in the context of the new and repurposed second-line TB drugs (SLDs). We aimed to describe the treatment outcomes among pediatric MDR-TB patients receiving new and repurposed SLDs including the proportion who achieved favorable outcomes.

METHODS

We conducted a retrospective cohort study among pediatric patients (age ≤18 years) treated for MDR-TB in the country of Georgia from 2009 to 2016. A "new and repurposed" SLD regimen was defined as a regimen that included linezolid, bedaquiline, and/or delamanid. Favorable treatment outcome was defined by treatment completion or documented microbial "cure" status at the end of treatment. We assessed the association between the use of the new and repurposed SLDs with MDR-TB treatment outcomes using bivariate analyses and log-binomial regression.

RESULTS

There were 124 pediatric MDR-TB patients (median age: 13.7; interquartile range: 4.6-16.0) initiating treatment; 119 (96.0%) had a treatment outcome recorded and were included in our analyses. Eighteen (15.1%) patients received new and repurposed SLDs from 2015 or later. After adjusting for potential confounders, the proportion achieving favorable MDR-TB treatment outcomes was higher among patients treated with SLD regimens that included new and/or repurposed drugs when compared with those treated without (adjusted risk ratio: 1.17; 95% confidence interval: 0.51-2.72).

CONCLUSIONS

We observed a high proportion of favorable treatment outcomes among pediatric patients with MDR-TB receiving the new and repurposed SLDs. Further studies to evaluate the efficacy and children's tolerability of the new and repurposed SLDs are still warranted.

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.

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

Pharmacokinetic (PK) and pharmacodynamic (PD) analyses were conducted to determine the cumulative fraction of response (CFR) for 100 mg twice-daily (BID) and 200 mg once-daily (QD) delamanid in patients with multidrug-resistant tuberculosis (MDR-TB), using a pharmacodynamic target (PDT) that achieves 80% of maximum efficacy. First, in the mouse model of chronic TB, the PK/PD index for delamanid efficacy was determined to be area under the drug concentration-time curve over 24 h divided by MIC (AUC_0–24/MIC), with a PDT of 252.

Pharmacokinetic (PK) and pharmacodynamic (PD) analyses were conducted to determine the cumulative fraction of response (CFR) for 100 mg twice-daily (BID) and 200 mg once-daily (QD) delamanid in patients with multidrug-resistant tuberculosis (MDR-TB), using a pharmacodynamic target (PDT) that achieves 80% of maximum efficacy. First, in the mouse model of chronic TB, the PK/PD index for delamanid efficacy was determined to be area under the drug concentration-time curve over 24 h divided by MIC (AUC_0–24/MIC), with a PDT of 252. Second, in the hollow-fiber system model of tuberculosis, plasma-equivalent PDTs were identified as an AUC_0–24/MIC of 195 in log-phase bacteria and 201 in pH 5.8 cultures. Third, delamanid plasma AUC_0–24/MIC and sputum bacterial decline data from two early bactericidal activity trials identified a clinical PDT of AUC_0–24/MIC of 171. Finally, the CFRs for the currently approved 100-mg BID dose were determined to be above 95% in two MDR-TB clinical trials. The CFR for the 200-mg QD dose, evaluated in a trial in which delamanid was administered as 100 mg BID for 8 weeks plus 200 mg QD for 18 weeks, was 89.3% based on the mouse PDT and >90% on the other PDTs. QTcF (QTc interval corrected for heart rate by Fridericia’s formula) prolongation was approximately 50% lower for the 200 mg QD dose than the 100 mg BID dose. In conclusion, while CFRs of 100 mg BID and 200 mg QD delamanid were close to or above 90% in patients with MDR-TB, more-convenient once-daily dosing of delamanid is feasible and likely to have less effect on QTcF prolongation.

Clinical Outcomes Among Patients With Drug-resistant Tuberculosis Receiving Bedaquiline- or Delamanid-Containing Regimens

BACKGROUND

Bedaquiline and delamanid are newly available drugs for treating multidrug-resistant tuberculosis (MDR-TB); however, there are limited data guiding their use and no comparison studies.

METHODS

We conducted a prospective, observational study among patients with MDR-TB in Georgia who were receiving a bedaquiline- or delamanid-based treatment regimen. Monthly sputum cultures, minimal inhibitory concentration testing, and adverse event monitoring were performed. Primary outcomes were culture conversion rates and clinical outcomes. Targeted maximum likelihood estimation and super learning were utilized to produce a covariate-adjusted proportion of outcomes for each regimen.

RESULTS

Among 156 patients with MDR-TB, 100 were enrolled and 95 were receiving a bedaquiline-based (n = 64) or delamanid-based (n = 31) regimen. Most were male (82%) and the median age was 38 years. Rates of previous treatment (56%) and cavitary disease (61%) were high. The most common companion drugs included linezolid, clofazimine, cycloserine, and a fluoroquinolone. The median numbers of effective drugs received among patients on bedaquiline-based (4; interquartile range [IQR], 4-4) and delamanid-based (4; IQR, 3.5-5) regimens were similar. Rates of acquired drug resistance were significantly higher among patients receiving delamanid versus bedaquiline (36% vs 10%, respectively; P < .01). Adjusted rates of sputum culture conversion at 2 months (67% vs 47%, respectively; P = .10) and 6 months (95% vs 74%, respectively; P < .01), as well as more favorable clinical outcomes (96% vs 72%, respectively; P < .01), were higher among patients receiving bedaquiline versus delamanid.

CONCLUSIONS

Among patients with MDR-TB, bedaquiline-based regimens were associated with higher rates of sputum culture conversion, more favorable outcomes, and a lower rate of acquired drug resistance versus delamanid-based regimens.

Characterization of Genomic Variants Associated with Resistance to Bedaquiline and Delamanid in Naive Mycobacterium tuberculosis Clinical Strains

The role of mutations in genes associated with phenotypic resistance to bedaquiline (BDQ) and delamanid (DLM) in Mycobacterium tuberculosis complex (MTBc) strains is poorly characterized. A clear understanding of the genetic variants' role is crucial to guide the development of molecular-based drug susceptibility testing (DST). In this work, we analyzed all mutations in candidate genomic regions associated with BDQ- and DLM-resistant phenotypes using a whole-genome sequencing (WGS) data set from a collection of 4,795 MTBc clinical isolates from six countries with a high burden of tuberculosis (TB). From WGS analysis, we identified 61 and 163 unique mutations in genomic regions potentially involved in BDQ- and DLM-resistant phenotypes, respectively. Importantly, all strains were isolated from patients who likely have never been exposed to these medicines. To characterize the role of mutations, we calculated the free energy variation upon mutations in the available protein structures of Ddn (DLM), Fgd1 (DLM), and Rv0678 (BDQ) and performed MIC assays on a subset of MTBc strains carrying mutations to assess their phenotypic effect. The combination of structural and phenotypic data allowed for cataloguing the mutations clearly associated with resistance to BDQ (n = 4) and DLM (n = 35), only two of which were previously described, as well as about a hundred genetic variants without any correlation with resistance. Significantly, these results show that both BDQ and DLM resistance-related mutations are diverse and distributed across the entire region of each gene target, which is of critical importance for the development of comprehensive molecular diagnostic tools.

Natural Polymorphisms in Mycobacterium tuberculosis Conferring Resistance to Delamanid in Drug-Naive Patients

Mutations in the genes of the F420 signaling pathway of Mycobacterium tuberculosis complex, including dnn, fgd1, fbiA, fbiB, fbiC, and fbiD, can lead to delamanid resistance. We searched for such mutations among 129 M. tuberculosis strains from Asia, South America, and Africa using whole-genome sequencing; 70 (54%) strains had at least one mutation in one of the genes. For 10 strains with mutations, we determined the MIC of delamanid. We found one strain from a delamanid-naive patient carrying the natural polymorphism Tyr29del (ddn) that was associated with a critical delamanid MIC.

Recent Progress in the Discovery and Development of 2-Nitroimidazooxazines and 6-Nitroimidazooxazoles to Treat Tuberculosis and Neglected Tropical Diseases

Nitroimidazole drugs have a long history as therapeutic agents to treat bacterial and parasitic diseases. The discovery in 1989 of a bicyclic nitroimidazole lead, displaying in vitro and in vivo antitubercular activity, spurred intensive exploration of this and related scaffolds, which led to the regulatory approval of pretomanid and delamanid as a new class of tuberculosis drugs. Much of the discovery work related to this took place over a 20-year period ending in 2010, which is covered in a number of cited reviews. This review highlights subsequent research published over the 2011–August 2020 timeframe, and captures detailed structure–activity relationship studies and synthetic strategies directed towards uncovering newer generation drugs for both tuberculosis and selected neglected tropical diseases. Additionally, this review presents in silico calculations relating to the drug-like properties of lead compounds and clinical agents, as well as chemical development and manufacturing processes toward providing bulk drug supplies.

Multi-drug resistant tuberculosis with simultaneously acquired-drug resistance to bedaquiline and delamanid

This study is the first to report a clinical case of simultaneously acquired resistance to bedaquiline (BDQ) and delamanid (DLM). Whole genome sequencing revealed two nucleotide insertions (Rv0678 and fbiC) in the Mycobacterium tuberculosis isolate. The minimum inhibitory concentrations for BDQ and DLM were 0.25 µg/ml and >2.0 µg/ml, respectively.

An Experience with Delamanid in an XDR TB Case - Case Report

INTRODUCTION

Tuberculosis is an endemic infection and a serious public health problem in India. India constitutes one-fourth of the global TB population. The emerging drug resistance is a major threat to global tuberculosis care and control.

CASE REPORT

We present a case of newly diagnosed microbiologically confirmed, extremely drugresistant primary pulmonary tuberculosis which was treated with Delamanid and was found to be cured of tuberculosis.

DISCUSSION

Delamanid is a new anti-tubercular drug, which is thought to primarily inhibit the synthesis of methoxy-mycolic, and keto-mycolic acid, which are components of the mycobacterial cell wall. In our patient who was a newly diagnosed case of MDR-TB converted to XDR-TB in little course of time and we were successful in treating him with Delamanid therapy. His sputum culture conversion was achieved in 20 days. Even though the patient did not tolerate well because of the side effects of the drug, still he became microbiologically negative for tuberculosis.

CONCLUSION

Delamanid fulfills many target criteria for new TB drugs and may be particularly useful for the treatment of MDR-TB. It can be administered orally and its bactericidal properties make it suitable in regimens designed to shorten treatment duration. Clinical efficacy data, while limited, are reassuring.

Culture Conversion at 6 Months in Patients Receiving Delamanid-containing Regimens for the Treatment of Multidrug-resistant Tuberculosis

Delamanid should be effective against highly resistant strains of Mycobacteriumtuberculosis, but uptake has been slow globally. In the endTB (expand new drug markets for TB) Observational Study, which enrolled a large, heterogeneous cohorts of patients receiving delamanid as part of a multidrug regimen, 80% of participants experienced sputum culture conversion within 6 months. Clinical Trials Registration. NCT02754765.

Adduct Formation of Delamanid with NAD in Mycobacteria

Delamanid (DLM), a nitro-dihydroimidazooxazole derivative currently approved for pulmonary multidrug-resistant tuberculosis (TB) therapy, is a prodrug activated by mycobacterial 7,8-didemethyl-8-hydroxy 5-deazaflavin electron transfer coenzyme (F₄₂₀)-dependent nitroreductase (Ddn). Despite inhibiting the biosynthesis of a subclass of mycolic acids, the active DLM metabolite remained unknown. Comparative liquid chromatography-mass spectrometry (LC-MS) analysis of DLM metabolites revealed covalent binding of reduced DLM with a nicotinamide ring of NAD derivatives (oxidized form) in DLM-treated Mycobacterium tuberculosis var. Bacille de Calmette et Guérin. Isoniazid-resistant mutations in the type II NADH dehydrogenase gene (ndh) showed a higher intracellular NADH/NAD ratio and cross-resistance to DLM, which were restored by complementation of the mutants with wild-type ndh Our data demonstrated for the first time the adduct formation of reduced DLM with NAD in mycobacterial cells and its importance in the action of DLM.

State-of-the-art treatment strategies for nontuberculous mycobacteria infections

INTRODUCTION

Non-tuberculous Mycobacteria (NTM) are a group of organisms whose importance in medicine seems to be increasing in recent times. The increasing number of patients susceptible to these diseases make it necessary to expand our knowledge of therapeutic options and to explore future possibilities for the development of a therapeutic arsenal.

AREAS COVERED

In this review, the authors provide a brief introduction about the present importance of NTM and describe the present recommendations of the available guidelines for their treatment. They include a description of the future options for the management of these patients, especially focusing on new antibiotics. The authors also look at possibilities for future therapeutic options, such as antibiofilm strategies.

EXPERT OPINION

No actual changes have been made to the current recommendations for the management of most NTM infections (except perhaps the availability of nebulized amikacin). However, it is also true that we have increased the number of available antibiotic treatment options with good in vitro activity against NTM. The use of these drugs in selected cases could increase the therapeutic possibilities. However, some problems are still present, such as the knowledge of the actual meaning of a NTM isolate, and will probably be a key part of future research.

Compassionate drug use: Current status in India

The World Health Organization defines compassionate use (CU) as a “program that is intended to provide potentially life-saving experimental treatments to patients suffering from a disease for which no satisfactory authorized therapy exists and/or who cannot enter a clinical trial. For many patients, these programs represent their last hope.” Over the years, an increasing number of requests and isolated cases have paved the way for more robust CU programs by pharmaceutical companies and guidelines by eminent regulatory bodies globally. In India, although there is no formal mention of the term “Compassionate Use” by the Central Drugs Standard Control Organization, there are provisions in the Drugs and Cosmetics Act 1940 and Rules 1945 to allow drugs to be imported as and when necessary. Such applications can be submitted to the Drug Controller General of India by a hospital, patient, or a pharmaceutical company. The evidence of such use of drugs is underlined by the availability of bedaquiline and delamanid for extensively drug-resistant tuberculosis (TB) and multidrug-resistant TB patients, respectively. CU is in its nascent stage in India owing to the lack of policies and laws needed to govern it. There is a need for regulatory bodies and pharmaceutical companies to work together to extend the spectrum of CU of drugs for the betterment of needy patients.

Current and Future Prospects of Nitro-compounds as Drugs for Trypanosomiasis and Leishmaniasis

Interest in nitroheterocyclic drugs for the treatment of infectious diseases has undergone a resurgence in recent years. Here we review the current status of monocyclic and bicyclic nitroheterocyclic compounds as existing or potential new treatments for visceral leishmaniasis, Chagas' disease and human African trypanosomiasis. Both monocyclic (nifurtimox, benznidazole and fexinidazole) and bicyclic (pretomanid (PA-824) and delamanid (OPC-67683)) nitro-compounds are prodrugs, requiring enzymatic activation to exert their parasite toxicity. Current understanding of the nitroreductases involved in activation and possible mechanisms by which parasites develop resistance is discussed along with a description of the pharmacokinetic / pharmacodynamic behaviour and chemical structure-activity relationships of drugs and experimental compounds.

Delamanid Central Nervous System Pharmacokinetics in Tuberculous Meningitis in Rabbits and Humans

Central nervous system tuberculosis (TB) is devastating and affects vulnerable populations. Multidrug-resistant (MDR) and extensively drug-resistant (XDR) tuberculous meningitis (TBM) specifically are nearly uniformly fatal, with little information being available to guide the treatment of these patients. Delamanid (DLM), a nitro-dihydro-imidazooxazole, is a new, well-tolerated anti-TB drug with a low MIC (1 to 12 ng/ml) against Mycobacterium tuberculosis It is used for the treatment of pulmonary MDR-TB, but pharmacokinetic (PK) data for DLM in the central nervous system (CNS) of patients with TBM are not available. In the present study, we measured DLM concentrations in the brain and cerebrospinal fluid (CSF) of six rabbits with and without experimentally induced TBM receiving single-dose DLM. We report the steady-state CSF concentrations from three patients receiving DLM as part of multidrug treatment who underwent therapeutic drug monitoring. Drug was quantified using liquid chromatography-tandem mass spectrometry. In rabbits and humans, mean concentrations in CSF (in rabbits, 1.26 ng/ml at 9 h and 0.47 ng/ml at 24 h; in humans, 48 ng/ml at 4 h) were significantly lower than those in plasma (in rabbits, 124 ng/ml at 9 h and 14.5 ng/ml at 24 h; in humans, 726 ng/ml at 4 h), but the estimated free CSF/plasma ratios were generally >1. In rabbits, DLM concentrations in the brain were 5-fold higher than those in plasma (means, 518 ng/ml at 9 h and 74.0 ng/ml at 24 h). All patients with XDR-TBM receiving DLM experienced clinical improvement and survival. Collectively, these results suggest that DLM achieves adequate concentrations in brain tissue. Despite relatively low total CSF drug levels, free drug may be sufficient and DLM may have a role in treating TBM. More studies are needed to develop a fuller understanding of its distribution over time with treatment and clinical effectiveness.

In Vitro Activity of Bedaquiline and Delamanid against Nontuberculous Mycobacteria, Including Macrolide-Resistant Clinical Isolates

We evaluated the in vitro activities of the antimicrobial drugs bedaquiline and delamanid against the major pathogenic nontuberculous mycobacteria (NTM). Delamanid showed high MIC values for all NTM except Mycobacterium kansasii However, bedaquiline showed low MIC values for the major pathogenic NTM, including Mycobacterium avium complex, Mycobacterium abscessus subsp. abscessus, M. abscessus subsp. massiliense, and M. kansasii Bedaquiline also had low MIC values with macrolide-resistant NTM strains and warrants further investigation as a potential antibiotic for NTM treatment.

In Vitro Activities of Bedaquiline and Delamanid against Nontuberculous Mycobacteria Isolated in Beijing, China

Due to the natural resistance of nontuberculous mycobacteria (NTM) against multiple antibiotics, treatment of infections caused by them is often long-course and less successful. The main objective of our study was the evaluation of in vitro susceptibility of 209 isolates consisting of different NTM species against bedaquiline and delamanid. Furthermore, reference strains of 33 rapidly growing mycobacterium (RGM) species and 19 slowly growing mycobacterium (SGM) species were also tested. Bedaquiline exhibited strong in vitro activity against both reference strains and clinical isolates of different SGM species, as the majority of the strains demonstrated MICs far below 1 μg/ml. Bedaquiline (Bdq) also exhibited potent activity against the recruited RGM species. A total of 29 out of 33 reference RGM strains had MICs lower than 1 μg/ml. According to the MIC distributions, the tentative epidemiological cutoff (ECOFF) values, and the pharmacokinetic data, a uniform breakpoint of 2 μg/ml was temporarily proposed for NTM's Bdq susceptibility testing. Although delamanid (Dlm) was not active against most of the tested reference strains and clinical isolates of RGM species, it exhibited highly variable antimicrobial activities against the 19 tested SGM species. Eleven species had MICs lower than 0.25 μg/ml, and 7 species had MICs greater than 32 μg/ml. Large numbers of M. kansasii (39/45) and M. gordonae (6/10) clinical isolates had MICs of ≤0.125 μg/ml. This study demonstrated that bedaquiline had potent activity against different NTM species in vitro, and delamanid had moderate activity against certain species of SGM. The data provided important insights on the possible clinical application of Bdq and Dlm to treat NTM infections.