Compassionate and optimum use of new tuberculosis drugs

Unraveling Dilemmas and Lacunae in the Escalating Drug Resistance of Mycobacterium tuberculosis to Bedaquiline, Delamanid, and Pretomanid

Delamanid, bedaquiline, and pretomanid have been recently added in the anti-tuberculosis (anti-TB) treatment regimens and have emerged as potential solutions for combating drug-resistant TB. These drugs have proven to be effective in treating drug-resistant TB when used in combination. However, concerns have been raised about the eventual loss of these drugs due to evolving resistance mechanisms and certain adverse effects such as prolonged QT period, gastrointestinal problems, hepatotoxicity, and renal disorders. This Perspective emphasizes the properties of these first-in-class drugs, including their mechanism of action, pharmacokinetics/pharmacodynamics profiles, clinical studies, adverse events, and underlying resistance mechanisms. A brief coverage of efforts toward the generation of best-in-class leads in each class is also provided. The ongoing clinical trials of new combinations of these drugs are discussed, thus providing a better insight into the use of these drugs while designing an effective treatment regimen for resistant TB cases.

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.

Polymorphisms in drug metabolism genes as a risk factor for first-line anti-tuberculosis drug-induced liver injury

BACKGROUND

Anti-tuberculosis drug-induced liver injury (AT-DILI) is one of the most common side effects in TB patients during treatment. The prime cause of liver injury during TB treatment is reported to be isoniazid and its metabolites. Different factors influenced the development of AT-DILI, and genetic factors are one of the major factors.

METHODS AND RESULTS

Polymorphisms in drug metabolism genes like NAT2, CYP2E1, PXR, and GST have been reported to be associated with AT-DILI, and they are one of the major areas of focus at present. Attempts are met in this review to analyse the different markers in these drug metabolism genes for their association with AT-DILI.

CONCLUSION

A better understanding of the polymorphisms in these genes and their functional effects will give better insights into the development of AT-DILI, and it could facilitate in designing and developing more effective personalized treatment for TB.

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.

Examples of bedaquiline introduction for the management of multidrug-resistant tuberculosis in five countries

BACKGROUND

For the first time in almost 50 years, there are new drugs available for the treatment of tuberculosis (TB), including bedaquiline (BDQ) and delamanid (DLM). The rate of introduction, however, has not kept pace with patient needs. It is estimated that as many as 23% of multidrug-resistant TB (MDR-TB) patients have an indication for receiving BDQ. As this is the first time the MDR-TB community is introducing new medications, it is important to understand how implementation can be developed in a variety of settings.

METHODS

A qualitative assessment of country TB programs in which more than 5% of MDR-TB patients were started on BDQ under program conditions.

RESULTS

National TB programs in Belarus, France, Georgia, South Africa, and Swaziland all started sizeable cohorts of patients on BDQ in 2015. Common factors observed in these programs included experience with compassionate use/expanded access, support from implementing partners, and adequate national or donor-supported budgets. Barriers to introduction included restriction of BDQ to the in-patient setting, lack of access to companion drugs, and the development of systems for pharmacovigilance.

CONCLUSION

The five countries in this paper are examples of the introduction of new therapeutic options for the treatment of TB.

New and Repurposed Drugs for Pediatric Multidrug-Resistant Tuberculosis. Practice-based Recommendations

It is estimated that 33,000 children develop multidrug-resistant tuberculosis (MDR-TB) each year. In spite of these numbers, children and adolescents have limited access to the new and repurposed MDR-TB drugs. There is also little clinical guidance for the use of these drugs and for the shorter MDR-TB regimen in the pediatric population. This is despite the fact that these drugs and regimens are associated with improved interim outcomes and acceptable safety profiles in adults. This review fills a gap in the pediatric MDR-TB literature by providing practice-based recommendations for the use of the new (delamanid and bedaquiline) and repurposed (linezolid and clofazimine) MDR-TB drugs and the new shorter MDR-TB regimen in children and adolescents.

Delamanid and bedaquiline to treat multidrug-resistant and extensively drug-resistant tuberculosis in children: a systematic review

The new drugs delamanid and bedaquiline are increasingly used to treat multidrug-resistant (MDR-) and extensively drug-resistant tuberculosis (XDR-TB). As evidence is lacking, the World Health Organization recommends their use under specific conditions in adults, delamanid only being recommended in children ≥6 years of age. No systematic review has yet evaluated the efficacy, safety and tolerability of the new drugs in children. A search of peer-reviewed, scientific evidence was performed, to evaluate the efficacy/effectiveness, safety, and tolerability of delamanid or bedaquiline-containing regimens in children with confirmed M/XDR-TB. We used PubMed and Embase to identify any relevant manuscripts in English until 31 December 2016, excluding editorials and reviews. Three out of 96 manuscripts retrieved satisfied the inclusion criteria, while 93 were excluded because dealing exclusively with adults (12: 4 on delamanid and 8 on bedaquiline), being recommendations or guidelines (8 manuscripts), reviews (17 papers) or other studies (56 papers). One of the studies retrieved reported evidence on 19 M/XDR-TB children, 16 of them treated under compassionate use with delamanid (13 achieving consistent bacteriological conversion) and 3 candidates for the drug. Two studies reported details on the first paediatric case treated (and cured) with a delamanid-containing regimen. Eight trials including children were also retrieved (clinicaltrials.gov). Although the methodology used in the study was rigorous, the results are limited by the paucity of the studies available in the literature on the use of new anti-TB drugs in children. In conclusion, more evidence is needed on the use of delamanid and bedaquiline in paediatric patients.

Combined Use of Delamanid and Bedaquiline to Treat Multidrug-Resistant and Extensively Drug-Resistant Tuberculosis: A Systematic Review

The new drugs delamanid and bedaquiline are increasingly being used to treat multidrug-resistant (MDR-) and extensively drug-resistant tuberculosis (XDR-TB). The World Health Organization, based on lack of evidence, recommends their use under specific conditions and not in combination. No systematic review has yet evaluated the efficacy, safety, and tolerability of delamanid and bedaquiline used in combination. A search of peer-reviewed, scientific evidence was carried out, aimed at evaluating the efficacy/effectiveness, safety, and tolerability of delamanid and bedaquiline-containing regimens in individuals with pulmonary/extrapulmonary disease, which were bacteriologically confirmed as M/XDR-TB. We used PubMed to identify any relevant manuscripts in English up to the 23 December 2016, excluding editorials and reviews. Three out of 75 manuscripts retrieved satisfied the inclusion criteria, whilst 72 were excluded for dealing with only one drug (three studies), being recommendations (one study) or identifying need for their use (one study), focusing on drug resistance aspects (six studies) or being generic reviews/other studies (61 papers). The studies retrieved reported two XDR-TB cases observed for six months and achieving consistent sputum smear and culture conversion. Case 2 experienced a short break of bedaquiline, which was re-started after introducing verapamil. After a transient and symptom-free increase of the QT interval from week 5 to 17, it then decreased below the 500 ms threshold.

Recent developments in the diagnosis and management of tuberculosis

Tuberculosis (TB) is a major public health issue worldwide, with ~9.6 million new incident cases and 1.5 million deaths in 2014. The End-TB Strategy launched by the World Health Organization in the context of the post-2015 agenda aims to markedly abate the scourge of TB towards global elimination, by improving current diagnostic and therapeutic practices, promoting preventative interventions, stimulating government commitment and increased financing, and intensifying research and innovation. The emergence and spread of multidrug-resistant strains is currently among the greatest concerns, which may hinder the achievement of future goals. It is crucial that primary healthcare providers are sufficiently familiar with the basic principles of TB diagnosis and care, to ensure early case detection and prompt referral to specialised centres for treatment initiation and follow-up. Given their special relationship with patients, they are in the best position to promote educational interventions and identify at-risk individuals as well as to improve adherence to treatment.

Clinical management of adults and children with multidrug-resistant and extensively drug-resistant tuberculosis

BACKGROUND

Globally there is a burgeoning epidemic of drug monoresistant tuberculosis (TB), multidrug-resistant TB (MDR-TB) and extensively drug-resistant TB (XDR-TB). Almost 20% of all TB strains worldwide are resistant to at least one major TB drug, including isoniazid. In several parts of the world there is an increasing incidence of MDR-TB, and alarmingly, almost a third of MDR-TB cases globally are resistant to either a fluoroquinolone or aminoglycoside. This trend cannot be ignored because drug-resistant TB is associated with greater morbidity compared to drug-susceptible TB, accounts for almost 25% of global TB mortality, is extremely costly to treat, consumes substantial portions of budgets allocated to national TB programmes in TB-endemic countries and is a major threat to healthcare workers, who are already in short supply in resource-poor settings. Even more worrying is the growing epidemic of resistance beyond XDR-TB, including resistance to newer drugs such as bedaquiline and delamanid, as well as the increasing prevalence of programmatically incurable TB in countries like South Africa, Russia, India and China. These developments threaten to reverse the gains already made against TB.

SOURCES

Articles related to MDR-TB and XDR-TB found on PubMed in all languages up to September 2016, published reviews, and files of the authors.

AIM AND CONTENT

To review the clinical management of adults and children with MDR- and XDR-TB with a particular emphasis on the utility of newer and repurposed drugs such as linezolid, bedaquiline and delamanid, as well as management of MDR- and XDR-TB in special situations such as in HIV-infected persons and in children.

IMPLICATIONS

This review informs on the prevention, diagnosis, and clinical management of MDR-TB and XDR-TB.

WHO strategies for the programmatic management of drug-resistant tuberculosis

INTRODUCTION

Adequate management of drug-resistant tuberculosis (TB), including multidrug- (MDR) and extensively drug-resistant (XDR-) TB are within the priorities of the newly launched World Health Organization's End TB and Elimination Strategies.

AREAS COVERED

This manuscript presents the evidence on the MDR- /XDR-TB epidemiology and discusses how the five recommended priority actions can be applied at the programmatic level to tackle the epidemic: 1) prevent development of MDR-TB thorough high quality treatment of drug- susceptible TB; 2) expand rapid testing and detection of drug-resistant TB; 3) provide immediate access to effective treatment and proper care; 4) prevent transmission through infection control; 5) increase political commitment and financing. A non-systematic review using Pubmed was carried out in addition to additional relevant information taken from the abstracts of international scientific conferences. Expert commentary: Current and future control of MDR-TB significantly relies on the correct use of new diagnostics and new drugs from one side, and on the consistent application of the five core interventions at the programmatic level. In addition, it is mandatory to tackle the social determinants and socio-economic barriers favouring the MDR-TB, otherwise it will not be possible to reach the planned goals as well as TB Elimination.

New Antituberculosis Drugs: From Clinical Trial to Programmatic Use

Treatment of multidrug-resistant tuberculosis (MDR-TB) cases is challenging because it relies on second-line drugs that are less potent and more toxic than those used in the clinical management of drug-susceptible TB. Moreover, treatment outcomes for MDR-TB are generally poor compared to drug sensitive disease, highlighting the need for of new drugs. For the first time in more than 50 years, two new anti-TB drugs were approved and released. Bedaquiline is a first-in-class diarylquinoline compound that showed durable culture conversion at 24 weeks in phase IIb trials. Delamanid is the first drug of the nitroimidazole class to enter clinical practice. Similarly to bedaquiline results of phase IIb studies showed increased sputum-culture conversion at 2 months and better final treatment outcomes in patients with MDR-TB. Among repurposed drugs linezolid and carbapenems may represent a valuable drug to treat cases of MDR and extensively drug-resistant TB. The recommended regimen for MDR-TB is the combination of at least four drugs to which M. tuberculosis is likely to be susceptible for the duration of 20 months. Drugs are chosen with a stepwise selection process through five groups on the basis of efficacy, safety, and cost. Clinical phase III trials on new regimen are ongoing that could prove transformative against MDR-TB, by being shorter (six months), simpler (an all-oral regimen) and safer than current standard therapy. It is fundamental that the adoption of the new drugs is done responsibly to avoid inappropriate use. Concentration of in-patient MDR-TB treatment in specialized centers could be considered in countries with low numbers of cases in order to provide appropriate clinical case management and to prevent emergence of drug resistance.

Compassionate use of new drugs in children and adolescents with multidrug-resistant and extensively drug-resistant tuberculosis: early experiences and challenges

The World Health Organization (WHO) estimated that 480 000 new multidrug-resistant (MDR) tuberculosis (TB) cases occurred globally in 2014, with 190 000 deaths. Limited data are available on the burden of MDR-TB in children. A recent systematic review estimated that 32 000 children acquire MDR-TB annually; of these, very few are correctly diagnosed and provided with appropriate treatment [1].

First experience and challenges of compassionate use of new anti-TB drugs to treat MDR- and XDR-TB in childrenhttp://ow.ly/SWXF300a0UX

First case of extensively drug-resistant tuberculosis treated with both delamanid and bedaquiline

The European Respiratory Journal has recently discussed delamanid and bedaquiline and their use in difficult-to-treat cases affected by multidrug-resistant tuberculosis (MDR-TB) or extensively drug-resistant (XDR-TB) [1–4]. The use of delamanid or bedaquiline is particularly important when four active drugs cannot be identified and included in a regimen, as per World Health Organization (WHO) guidelines [1–6]. Recently a debate has been initiated around the report of a severe, almost untreatable, XDR-TB case who could not access both new drugs simultaneously [7–10] due to concerns about possible additive toxicity (cardiotoxicity), as well as the lack of evidence and specific guidance on their combined use [10–13].

Report of the first case, concerns and challenges of treatment of severe XDR-TB with both delamanid and bedaquilinehttp://ow.ly/WzeB3004Cmo

Comparison of effectiveness and safety of imipenem/clavulanate-versusmeropenem/clavulanate-containing regimens in the treatment of MDR- and XDR-TB

No large study to date has ever evaluated the effectiveness, safety and tolerability of imipenem/clavulanateversusmeropenem/clavulanate to treat multidrug- and extensively drug-resistant tuberculosis (MDR- and XDR-TB). The aim of this observational study was to compare the therapeutic contribution of imipenem/clavulanateversusmeropenem/clavulanate added to background regimens to treat MDR- and XDR-TB cases.

84 patients treated with imipenem/clavulanate-containing regimens showed a similar median number of antibiotic resistances (8versus8) but more fluoroquinolone resistance (79.0%versus48.9%, p<0.0001) and higher XDR-TB prevalence (67.9%versus49.0%, p=0.01) in comparison with 96 patients exposed to meropenem/clavulanate-containing regimens. Patients were treated with imipenem/clavulanate- and meropenem/clavulanate-containing regimens for a median (interquartile range) of 187 (60–428)versus85 (49–156) days, respectively.

Statistically significant differences were observed on sputum smear and culture conversion rates (79.7%versus94.8%, p=0.02 and 71.9%versus94.8%, p<0.0001, respectively) and on success rates (59.7%versus77.5%, p=0.03). Adverse events to imipenem/clavulanate and meropenem/clavulanate were reported in 5.4% and 6.5% of cases only.

Our study suggests that meropenem/clavulanate is more effective than imipenem/clavulanate in treating MDR/XDR-TB patients.

Carbapenems to Treat Multidrug and Extensively Drug-Resistant Tuberculosis: A Systematic Review

BACKGROUND

Carbapenems (ertapenem, imipenem, meropenem) are used to treat multidrug-resistant (MDR-) and extensively drug-resistant tuberculosis (XDR-TB), even if the published evidence is limited, particularly when it is otherwise difficult to identify the recommended four active drugs to be included in the regimen. No systematic review to date has ever evaluated the efficacy, safety, and tolerability of carbapenems.

METHODS

A search of peer-reviewed, scientific evidence was carried out, aimed at evaluating the efficacy/effectiveness, safety, and tolerability of carbapenem-containing regimens in individuals with pulmonary/extra-pulmonary disease which was bacteriologically confirmed as M/XDR-TB. We used PubMed to identify relevant full-text, English manuscripts up to the 20 December 2015, excluding editorials and reviews.

RESULTS

Seven out of 160 studies satisfied the inclusion criteria: two on ertapenem, one on imipenem, and four on meropenem, all published between 2005 and 2016. Of seven studies, six were retrospective, four were performed in a single center, two enrolled children, two had a control group, and six reported a proportion of XDR-TB cases higher than 20%. Treatment success was higher than 57% in five studies with culture conversion rates between 60% and 94.8%.

CONCLUSIONS

The safety and tolerability is very good, with the proportion of adverse events attributable to carbapenems below 15%.