Linezolid for extensively drug-resistant tuberculosis

Linezolid for drug-resistant pulmonary tuberculosis

BACKGROUND

Linezolid was recently re-classified as a Group A drug by the World Health Organization (WHO) for treatment of multi-drug resistant tuberculosis (MDR-TB) and extensively drug-resistant tuberculosis (XDR-TB), suggesting that it should be included in the regimen for all patients unless contraindicated. Linezolid use carries a considerable risk of toxicity, with the optimal dose and duration remaining unclear. Current guidelines are mainly based on evidence from observational non-comparative studies.

OBJECTIVES

To assess the efficacy of linezolid when used as part of a second-line regimen for treating people with MDR and XDR pulmonary tuberculosis, and to assess the prevalence and severity of adverse events associated with linezolid use in this patient group.

SEARCH METHODS

We searched the following databases: the Cochrane Infectious Diseases Specialized Register; CENTRAL; MEDLINE; Embase; and LILACS up to 13 July 2018. We also checked article reference lists and contacted researchers in the field.

SELECTION CRITERIA

We included studies in which some participants received linezolid, and others did not. We included randomized controlled trials (RCTs) of linezolid for MDR and XDR pulmonary tuberculosis to evaluate efficacy outcomes. We added non-randomized cohort studies to evaluate adverse events.Primary outcomes were all-cause and tuberculosis-associated death, treatment failure, and cure. Secondary outcomes were treatment interrupted, treatment completed, and time to sputum culture conversion. We recorded frequency of all and serious adverse events, adverse events leading to drug discontinuation or dose reduction, and adverse events attributed to linezolid, particularly neuropathy, anaemia, and thrombocytopenia.

DATA COLLECTION AND ANALYSIS

Two review authors (BS and DC) independently assessed the search results for eligibility and extracted data from included studies. All review authors assessed risk of bias using the Cochrane 'Risk of bias' tool for RCTs and the ROBINS-I tool for non-randomized studies. We contacted study authors for clarification and additional data when necessary.We were unable to perform a meta-analysis as one of the RCTs adopted a study design where participants in the study group received linezolid immediately and participants in the control group received linezolid after two months, and therefore there were no comparable data from this trial. We deemed meta-analysis of non-randomized study data inappropriate.

MAIN RESULTS

We identified three RCTs for inclusion. One of these studies had serious problems with allocation of the study drug and placebo, so we could not analyse data for intervention effect from it. The remaining two RCTs recruited 104 participants. One randomized 65 participants to receive linezolid or not, in addition to a background regimen; the other randomized 39 participants to addition of linezolid to a background regimen immediately, or after a delay of two months. We included 14 non-randomized cohort studies (two prospective, 12 retrospective), with a total of 1678 participants.Settings varied in terms of income and tuberculosis burden. One RCT and 7 out of 14 non-randomized studies commenced recruitment in or after 2009. All RCT participants and 38.7% of non-randomized participants were reported to have XDR-TB.Dosing and duration of linezolid in studies were variable and reported inconsistently. Daily doses ranged from 300 mg to 1200 mg; some studies had planned dose reduction for all participants after a set time, others had incompletely reported dose reductions for some participants, and most did not report numbers of participants receiving each dose. Mean or median duration of linezolid therapy was longer than 90 days in eight of the 14 non-randomized cohorts that reported this information.Duration of participant follow-up varied between RCTs. Only five out of 14 non-randomized studies reported follow-up duration.Both RCTs were at low risk of reporting bias and unclear risk of selection bias. One RCT was at high risk of performance and detection bias, and low risk for attrition bias, for all outcomes. The other RCT was at low risk of detection and attrition bias for the primary outcome, with unclear risk of detection and attrition bias for non-primary outcomes, and unclear risk of performance bias for all outcomes. Overall risk of bias for the non-randomized studies was critical for three studies, and serious for the remaining 11.One RCT reported higher cure (risk ratio (RR) 2.36, 95% confidence interval (CI) 1.13 to 4.90, very low-certainty evidence), lower failure (RR 0.26, 95% CI 0.10 to 0.70, very low-certainty evidence), and higher sputum culture conversion at 24 months (RR 2.10, 95% CI 1.30 to 3.40, very low-certainty evidence), amongst the linezolid-treated group than controls, with no differences in other primary and secondary outcomes. This study also found more anaemia (17/33 versus 2/32), nausea and vomiting, and neuropathy (14/33 versus 1/32) events amongst linezolid-receiving participants. Linezolid was discontinued early and permanently in two of 33 (6.1%) participants who received it.The other RCT reported higher sputum culture conversion four months after randomization (RR 2.26, 95% CI 1.19 to 4.28), amongst the group who received linezolid immediately compared to the group who had linezolid initiation delayed by two months. Linezolid was discontinued early and permanently in seven of 39 (17.9%) participants who received it.Linezolid discontinuation occurred in 22.6% (141/624; 11 studies), of participants in the non-randomized studies. Total, serious, and linezolid-attributed adverse events could not be summarized quantitatively or comparatively, due to incompleteness of data on duration of follow-up and numbers of participants experiencing events.

AUTHORS' CONCLUSIONS

We found some evidence of efficacy of linezolid for drug-resistant pulmonary tuberculosis from RCTs in participants with XDR-TB but adverse events and discontinuation of linezolid were common. Overall, there is a lack of comparative data on efficacy and safety. Serious risk of bias and heterogeneity in conducting and reporting non-randomized studies makes the existing, mostly retrospective, data difficult to interpret. Further prospective cohort studies or RCTs in high tuberculosis burden low-income and lower-middle-income countries would be useful to inform policymakers and clinicians of the efficacy and safety of linezolid as a component of drug-resistant TB treatment regimens.

Efficacy and safety profile of linezolid in the treatment of multidrug-resistant (MDR) and extensively drug-resistant (XDR) tuberculosis: a systematic review and meta-analysis

Background

Treatment options for drug-resistant tuberculosis are still limited. Linezolid has been recommended for treatment of patients with multidrug-resistant (MDR) or extensively-drug-resistant (XDR) tuberculosis, although uncertainties remain regarding its safety and tolerability in these circumstances.

Objective

To systematically evaluate the existing evidence regarding the efficacy and tolerability of linezolid in the treatment of MDR or XDR tuberculosis.

Methods

We conducted a systematic review and meta-analysis in accordance with the PRISMA guidelines. Searches were conducted in PubMed, Web of Science and EMBASE followed by direct search of abstracts in the International Journal of Tuberculosis and Lung Disease to retrieve primary studies published between January 2000 and January 2016 assessing linezolid efficacy and safety in the treatment of drug-resistant TB. We evaluated the occurrence of outcomes including culture conversion, treatment success and incidence of adverse events such as myelosuppression and neuropathy.

Results

Twenty-three (23) studies conducted in fourteen (14) countries and involving 507 patients were retrieved. Only 1 randomized controlled trial was identified and none of the identified studies involved participants from Africa. The pooled proportion for treatment success was 77.36 % (95 % CI = 71.38–82.83 %, I² = 37.6 %) with culture conversion rate determined as 88.45 % (95 % CI = 83.82–92.38 %, I² = 45.4 %). There was no strong evidence for both culture conversion (p = 0.0948) and treatment success (p = 0.0695) between linezolid daily doses ≤ 600 and > 600 mg. Only myelosuppression showed a strong statistical significance (p < 0.0001) between dose comparisons. The incidence of neuropathy and other adverse events leading to permanent discontinuation of linezolid also showed no significance upon dose comparisons (p = 0.3213, p = 0.9050 respectively).

Conclusion

Available evidence presents Linezolid as a viable option in the treatment of MDR/XDR TB although patients ought to be monitored closely for the incidence of major adverse events such as myelosuppression and neuropathy. Additionally, highly powered randomized controlled trials including participants from endemic regions are urgently needed to better inform the magnitude and significance of Linezolid treatment effect in MDR and XDR TB patients.

Electronic supplementary material

The online version of this article (doi:10.1186/s12941-016-0156-y) contains supplementary material, which is available to authorized users.

Discovery of novel bis-oxazolidinone compounds as potential potent and selective antitubercular agents

A variety of new mono-oxazolidinone molecules by modifying the C-ring of Linezolid, a marketed antibiotic for MRSA, were synthesized and tested for their in vitro antibacterial activities against several Staphylococcus aureus, Mycobacterium smegmatis and two Gram-negative bacteria strains (Escherichia coli and Pseudomonas aeruginosa). Among them, compounds 4-7 displayed moderate antimicrobial activities. After development of a second oxazolidinone ring in the western part of the mono-oxazolidinone compounds 4-7 by a ring closure reaction with N,N'-carbonyldiimidazole (CDI), we found thus obtained bis-oxazolidinone compounds 22-25 possess excellently inhibitory activities against H37Rv but poor or no effects on other test bacteria. Among them, bis-oxazolidinone compound 22 and 24 are the most potent two compounds with a same MIC value of 0.125μg/mL against H37Rv virulent strain. Compound 22 also exhibited extremely low cytotoxicity on monkey kidney Vero cells with a selective index (IC50/MIC) over 40,000, which suggested bis-oxazolidinone compound 22 is a promising lead compound for subsequent investigation in search of new antitubercular agents.