Treatment-shortening regimens for tuberculosis: updates and future priorities

Structural and mechanistic study of a novel inhibitor analogue of M. tuberculosis cytochrome bc1:aa3

Drug-resistant tuberculosis (TB) continues to challenge treatment options, necessitating the exploration of new compounds of novel targets. The mycobacterial respiratory complex cytochrome bc1:aa3 has emerged as a promising target, exemplified by the success of first-in-class inhibitor Q203 in phase 2 clinical trials. However, to fully exploit the potential of this target and to identify the best-in-class inhibitor more compounds need evaluation. Here, we introduce JNJ-2901, a novel Q203 analogue, that demonstrates activity against multidrug-resistant M. tuberculosis clinical strains at sub-nanomolar concentration and 4-log reduction in bacterial burden in a mouse model of TB infection. Inhibitory studies on purified enzymes validate the nanomolar inhibitions observed in mycobacterial cells. Additionally, cryo-EM structure analysis of cytochrome bc1:aa3 bound to JNJ-2901 reveals the binding pocket at the menaquinol oxidation site (Qp), akin to other substate analogue inhibitors like Q203 and TB47. Validation of the binding site is further achieved by generating and isolating the JNJ-2901 resistant mutations in M. tuberculosis, followed by purification and resistance analysis of the resistant cytochrome bc1:aa3 complex. Our comprehensive work lays the foundation for further clinical validations of JNJ-2901.

Safety and Effectiveness of BPaL-Based Regimens to Treat Multidrug-Resistant TB: First Experience of an Italian Tuberculosis Referral Hospital

Background/Objectives: Tuberculosis (TB) is preventable and curable, but multidrug-resistant TB (MDR-TB) and extensively drug-resistant TB (XDR-TB) pose significant challenges worldwide due to the limited treatment options, lengths of therapies, and high rates of treatment failure. The management of MDR-TB has been revolutionized by all oral anti-TB drug regimens that are likely to improve adherence and treatment outcomes. These regimes include bedaquiline (B), pretomanid (P), and linezolid (L) (BPaL), and moxifloxacin if resistance to fluoroquinolones is not detected (BPaLM). Based on the evidence generated by the TB-PRACTECAL and ZeNix randomized controlled trials, BPaL/BPaLM regimens are recommended over the currently recommended longer regimens in patients with MDR-TB or monoresistance to rifampin (RR). To our knowledge, no data are currently available on the implementation of BPaL/BPaLM regimens in Italy. Results: Seventeen patients completed the BPaL/BPaLM regimen, with a treatment success rate of 90% (17/19), consistent with the literature data. Eleven patients out of the nineteen retained in care (58%) complained about symptoms consistent with adverse events (AEs). No treatment interruption was necessary due to AEs. Methods: Here, we report the real-world experience of a tertiary referral hospital for TB in Italy, from 2022 to 2024, in the management, outcomes, and adverse drug reactions of a cohort of twenty-two MDR/RR patients treated with BPaL and BPaLM regimens. Conclusions: BPaL-containing regimens also serve as promising options for patients with RR/MDR-TB in terms of real-life experience, but further multicentric studies are required in Europe to confirm the efficacy of shorter regimens to eliminate MDR TB.

Pulmonary tuberculosis in non-HIV adults: an evergreen old-fashioned disease in high-income countries. A narrative review

INTRODUCTION

Tuberculosis (TB), an infective air-borne disease with worldwide non-homogeneous distribution, remains a top cause of morbidity and mortality. TB control is linked to early diagnosis and proper treatment of contagious TB cases and infected subjects at high risk of developing TB.

AREAS COVERED

A narrative review of pulmonary TB in non-HIV adults with reference to high-income countries. Modern medicine offers several advancements in diagnostics and therapeutics of TB, but they often remain to be extensively implemented in real life. In high-income countries TB is now relatively uncommon, but it remains a health and socio-economic burden that should not be underestimated.

EXPERT OPINION

Pulmonologists should maintain expertise toward TB for several reasons. First, the lung is the most common and the infectious moiety of TB. Second, TB remains a global issue due to common travels of western people and migrations from areas with high incidence of TB. Third, as TB has heterogenous clinics, its prompt diagnosis may be difficult. Fourth, TB is a curable disease, but its management is complex and predisposes to poor adherence with failures/relapses and selection of drug-resistant strains.

Effectiveness and safety of modified fully oral 9-month treatment regimens for rifampicin-resistant tuberculosis: a prospective cohort study

BACKGROUND

In 2020, WHO guidelines prioritised the use of a standard fully oral short treatment regimen (STR) consisting of bedaquiline, levofloxacin or moxifloxacin, ethionamide, ethambutol, high-dose isoniazid, pyrazinamide, and clofazimine for the management of rifampicin-resistant tuberculosis. A high prevalence of resistance to constituent drugs precluded its widespread use by countries in the WHO European region. We evaluated three 9-month fully oral modified STRs (mSTRs) in which ethionamide, ethambutol, isoniazid, and pyrazinamide were replaced by linezolid, cycloserine, or delamanid (or a combination).

METHODS

This multicountry, prospective, single-arm, cohort study examined the effectiveness and safety of mSTRs for fluoroquinolone-susceptible, rifampicin-resistant pulmonary tuberculosis in 13 countries in the WHO European region during 2020-23. We enrolled adults and children of all ages with bacteriologically confirmed rifampicin-resistant, fluoroquinolone-susceptible pulmonary tuberculosis, and children (aged 0-18 years) with clinically diagnosed disease and a confirmed contact with rifampicin-resistant, fluoroquinolone-susceptible tuberculosis. Participants aged 6 years or older received one of two regimens: bedaquiline, linezolid, levofloxacin, clofazimine, and cycloserine; or bedaquiline, linezolid, levofloxacin, clofazimine, and delamanid. Children younger than 6 years received delamanid, linezolid, levofloxacin, and clofazimine. Participants were followed up for 12 months after successful treatment completion to detect recurrence and death. The primary outcome was the cumulative probability of not having an unsuccessful study outcome (defined as treatment failure, on-treatment loss to follow-up, death, or recurrence) before 22 months of study follow-up. The primary safety outcome was the incidence of each adverse event of interest (peripheral neuropathy, optic neuritis, myelosuppression, hepatitis, prolonged QT interval, hypokalaemia, and acute kidney injury) of grade 3 or higher severity during the treatment course.

FINDINGS

Between Aug 28, 2020 and May 26, 2021, 7272 patients were screened and 2636 were included in the treatment cohort. 1966 (74·6%) were male, 670 (25·4%) were female, and median age was 43 years (IQR 33-53). Treatment success was recorded for 2181 (82·7%) participants. The cumulative probability of not having an unsuccessful study outcome 22 months after treatment initiation was 79% (95% CI 78-81). Increasing age (adjusted hazard ratio 2·61 [95% CI 1·70-4·04] for people aged >64 years vs 35-44 years), HIV-positive status (1·53 [1·16-2·01]), presence of bilateral cavities (1·68 [1·29-2·19]), smoking history (1·34 [1·05-1·71]), baseline anaemia (1·46 [1·15-1·86]), unemployment (1·37 [1·04-1·80]), elevated baseline liver enzymes (1·40 [1·13-1·73]), and excessive alcohol use (1·47 [1·14-1·89]) were positively associated with unsuccessful study outcomes. In the safety cohort of 2813 participants who received at least one dose, 301 adverse events of interest were recorded in 252 (9·0%) participants with the most frequent being myelosuppression (139 [4·9%] participants, 157 [52·2%] events).

INTERPRETATION

The high treatment success and good safety results indicate considerable potential for the use of mSTRs in programmatic conditions, especially for individuals not eligible for the current WHO-recommended 6-month regimen and in settings with a need for alternative options.

FUNDING

The Global Fund to Fight AIDS, Tuberculosis and Malaria; United States Agency for International Development; Government of Germany; and WHO.

TRANSLATION

For the Russian translation of the abstract see Supplementary Materials section.

Association between HIV and acquisition of rifamycin resistance with first-line TB treatment: a systematic review and meta-analysis

BACKGROUND

Multi-drug or rifamycin-resistant tuberculosis (MDR/RR-TB) is an important public health concern, including in settings with high HIV prevalence. TB drug resistance can be directly transmitted or arise through resistance acquisition during first-line TB treatment. Limited evidence suggests that people living with HIV (PLHIV) might have an increased risk of acquired rifamycin-resistance (ARR).

METHODS

To assess HIV as a risk factor for ARR during first-line TB treatment, a systematic review and meta-analysis was conducted. ARR was defined as rifamycin-susceptibility at treatment start with rifamycin-resistance diagnosed during or at the end of treatment, or at recurrence. PubMed/MEDLINE, CINAHL, Cochrane Library, and Google Scholar databases were searched from inception to 23 May 2024 for articles in English; conference abstracts were also searched from 2004 to 2021. The Mantel-Haenszel random-effects model was used to estimate the pooled odds ratio of any association between HIV and ARR among individuals receiving first-line TB treatment.

RESULTS

Ten studies that included data collected between 1990 and 2014 were identified: five from the United States, two from South Africa and one each from Uganda, India and Moldova. A total of 97,564 individuals were included across all studies, with 13,359 (13.7%) PLHIV. Overall, 312 (0.32%) acquired rifamycin-resistance, among whom 115 (36.9%) were PLHIV. The weighted odds of ARR were 4.57 (95% CI, 2.01-10.42) times higher among PLHIV compared to HIV-negative individuals receiving first-line TB treatment.

CONCLUSION

The available data, suggest that PLHIV have an increased ARR risk during first-line TB treatment. Further research is needed to clarify specific risk factors, including advanced HIV disease and TB disease severity. Given the introduction of shorter, 4-month rifamycin-based regimens, there is an urgent need for additional data on ARR, particularly for PLHIV.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42022327337.

Tuberculosis treatment-shortening

Tuberculosis (TB) presents a significant global health concern, with ∼10 million people developing TB and 1.3 million people dying from the disease each year. The standard treatment regimen for drug-susceptible TB was between 6 and 9 months until recently, presenting a prolonged therapeutic duration compared with other infectious diseases. This is a long time for patients to adhere to the medication, consequently increasing the risk of developing drug-resistant Mycobacterium tuberculosis - a significant challenge in TB management globally. Therefore, the primary objective of contemporary TB drug development research is to shorten the treatment duration. This review comprehensively explores the strategies aimed at shortening TB treatment.

TB drug susceptibility testing in high fluoroquinolone resistance settings

BACKGROUND

The insurgence of resistance to key drugs of the BPaLM (bedaquiline + pretomanid + moxifloxacin) regimen is a major concern. In settings with widespread resistance to fluoroquinolones (FQs), like Pakistan, new technologies, such as Xpert® MTB/XDR, may ensure drug resistance upfront screening. This study aims to assess MTB/XDR's performance in detecting FQs and isoniazid resistance, proposing a renewed diagnostic algorithm for drug-resistant TB (DR-TB).

METHODS

This cross-sectional prospective study, approved by the local ethical committee, collected samples from people newly and previously diagnosed with TB over 6 months. Xpert® MTB/RIF Ultra, MTB/XDR, Genotype® MTBDRplus, Genotype® MTBDRsl, culture, and phenotypic drug susceptibility testing (pDST) for relevant drugs (including bedaquiline and levofloxacin) were performed. Next-generation sequencing (NGS) resolved discordances between MTB/XDR and pDST results.

RESULTS

The analysis showed that MTB/XDR has 91.5% and 88.2% sensitivity and 99.5% and 97.7% specificity in detecting respectively isoniazid (INH) and resistance to FQs, demonstrating that MTB/XDR meets the WHO targets for INH resistance detection at the peripheral level. NGS effectively resolved discordances between MTB/XDR and pDST results.

CONCLUSIONS

The obtained results allowed designing the proposed diagnostic algorithm for rapid identification of DR-TB, ensuring rapid and equitable access to drug susceptibility testing for TB, ultimately improving TB care and control.

A Comprehensive Review on Long vs. Short Regimens in Multidrug-Resistant Tuberculosis (MDR-TB) Under Programmatic Management of Drug-Resistant Tuberculosis (PMDT)

This comprehensive review delves into the intricate landscape of multidrug-resistant tuberculosis (MDR-TB) treatment within the programmatic management of drug-resistant tuberculosis (PMDT) framework. MDR-TB poses a substantial global health threat, necessitating targeted approaches for effective management. The analysis explores the historical evolution, efficacy, safety profiles, and implementation challenges associated with long and short regimens. The findings underscore the importance of individualized clinical practices, considering patient-specific factors, and the need for ongoing monitoring within PMDT programs. Recommendations advocate for integrating advanced diagnostics, continuous surveillance, and training for healthcare professionals. The review concludes with a nuanced outlook on long versus short regimens, emphasizing a balanced approach and the imperative role of collaborative efforts in shaping the future of MDR-TB treatment. This synthesis contributes to the ongoing discourse, providing valuable insights for healthcare practitioners, policymakers, and researchers working toward optimizing outcomes for individuals afflicted with MDR-TB.