Treatment optimization in patients co-infected with HIV and Mycobacterium tuberculosis infections: focus on drug-drug interactions with rifamycins

Clinical considerations and pharmacokinetic interactions between HIV and tuberculosis therapeutics

INTRODUCTION

Tuberculosis (TB) is a leading infectious disease cause of mortality worldwide, especially for people living with human immunodeficiency virus (PLWH). Treating TB in PLWH can be challenging due to numerous drug interactions.

AREAS COVERED

This review discusses drug interactions between antitubercular and antiretroviral drugs. Due to its clinical importance, initiation of antiretroviral therapy in patients requiring TB treatment is discussed. Special focus is placed on the rifamycin class, as it accounts for the majority of interactions. Clinically relevant guidance is provided on how to manage these interactions. An additional section on utilizing therapeutic drug monitoring (TDM) to optimize drug exposure and minimize toxicities is included.

EXPERT OPINION

Antitubercular and antiretroviral coadministration can be successfully managed. TDM can be used to optimize drug exposure and minimize toxicity risk. As new TB and HIV drugs are discovered, additional research will be needed to assess for clinically relevant drug interactions.

Update on the treatment of tuberculosis

Tuberculosis (TB) affects more than 10 million people each year. We have contested this burden with a paradoxically slow development of treatments, as compared to other infectious diseases. This review aims to update health care professionals on the last developments for the management of TB. The combination of drugs established more than 40years ago is still adequate to cure most people affected by TB. However, with the generalisation of regimens based on rifampicin and isoniazid for (only) 6months, resistance emerged. Resistant cases needed long treatments based on injectable drugs. Now, after an exciting decade of research, we can treat resistant TB with oral regimens based on bedaquiline, nitroimidazoles, and linezolid for (only) 6months, and we may soon break the 6-month barrier for treatment duration. However, these improvements are not enough to end TB without an engagement of people affected and their communities to achieve adherence to treatment, transmission control, and improve socioeconomic determinants of health.

Acquired rifamycin resistance among patients with tuberculosis and HIV in new York City, 2001-2023

Introduction

Acquired rifamycin resistance (ARR) in tuberculosis (TB) has been associated with HIV infection and can necessitate complicated TB treatment regimens, particularly in people living with HIV (PLWH). This work examines clinical characteristics and treatment outcomes of PLWH who developed ARR from 2001 to 2023 in New York City (NYC) to inform best practices for treating these patients.

Methods

PLWH who developed ARR 2001-2023 were identified from the NYC TB registry.

Results

Sixteen PLWH developed ARR; 15 were diagnosed 2001-2009 and the 16th was diagnosed in 2017. Median CD4 count was 48/mm3. On initial presentation, 14 had positive sputum cultures; of these, 12 culture-converted prior to developing ARR. Ten patients completed a course of TB treatment but subsequently relapsed; in six of these cases, ARR was discovered upon relapse, triggering treatment with a non-rifamycin-containing regimen, while in the other four, ARR was discovered during a second round of rifamycin-containing treatment. Three patients were lost to follow-up during their initial course of TB treatment and later returned to care; after being restarted on a rifamycin-containing regimen, ARR was discovered. Finally, three patients culture-converted during their first course of treatment but subsequently had cultures that grew rifamycin-resistant Mycobacterium tuberculosis prior to treatment completion, leading to changes in their treatment regimens. Among the 16 patients, eight died before being cured of TB, seven successfully completed treatment, and one was lost to follow-up.

Conclusions

PLWH should be monitored closely for the development of ARR during treatment for TB, and sputum culture conversion should be interpreted cautiously in this group. Collecting a final sputum sample may be especially important for PLWH, as treatment failure and relapse were common in this population. The decrease in the number of cases of ARR among PLWH during the study period may reflect the decrease in the total number of PLWH diagnosed with TB in NYC in recent years, improved immune status of PLWH due to increased uptake of antiretroviral drugs, and improvements in the way anti-TB regimens are designed for PLWH (such as recommending daily rather than intermittent rifamycin dosing).

Advances in Antiretroviral Therapy for Patients with Human Immunodeficiency Virus-Associated Tuberculosis

Tuberculosis is one of the most common opportunistic infections and a prominent cause of death in patients with human immunodeficiency virus (HIV) infection, in spite of near-universal access to antiretroviral therapy (ART) and tuberculosis preventive therapy. For patients with active tuberculosis but not yet receiving ART, starting ART after anti-tuberculosis treatment can complicate clinical management due to drug toxicities, drug-drug interactions and immune reconstitution inflammatory syndrome (IRIS) events. The timing of ART initiation has a crucial impact on treatment outcomes, especially for patients with tuberculous meningitis. The principles of ART in patients with HIV-associated tuberculosis are specific and relatively complex in comparison to patients with other opportunistic infections or cancers. In this review, we summarize the current progress in the timing of ART initiation, ART regimens, drug-drug interactions between anti-tuberculosis and antiretroviral agents, and IRIS.

Incidence and Predictors of Severe Adverse Drug Reactions among Patients on Antiretroviral Drugs in Harari Regional State, Eastern Ethiopia

Background

The introduction of combination antiretroviral therapy improves the quality and longevity of people living with HIV/AIDS. However, adverse drug reactions associated with antiretroviral therapy compromise the resulting benefits and have been reported differently worldwide, including Ethiopia. Severe adverse drug reactions are one of the major public health concerns for the reason that they can potentially impede the benefit of antiretroviral therapy and put the patient's survival at risk. Despite many successes achieved with the introduction of the combined antiretroviral therapy, the majority of the patients on antiretroviral therapy experience adverse drug reactions associated with the drugs. Consequently, little is known about the problem in the current study area. This is, therefore, to study incidence and predictors of severe adverse drug reactions among patients on antiretroviral drugs in the Harari region, Eastern Ethiopia. The aim of this study was to assess the incidence and predictors of severe adverse drug reactions among patients on antiretroviral therapy from February 25, 2022, to March 25, 2022, in the Harari region, Eastern Ethiopia.

Methods

A hospital-based retrospective cohort study was conducted among 449 randomly selected medical records of people living with HIV on first-line antiretroviral therapy. Collected data were entered into EpiData version 3.1 and exported to STATA version 15 for analysis. Kaplan-Meier survival curve with log-rank test was used to compare survival curves for categorical independent variables. A p value ≤0.05 was declared as significant, and an adjusted hazard ratio was used to report the effect size using the multivariate Cox proportional hazard model.

Result

The overall incidence density of the severe adverse reactions was 7.22 per 1000 months (95% CI: 5.5, 9.6). After adjusting for all potential confounders using multivariable Cox proportional hazard ratio, advanced clinical diseases (AHR = 3.44; 95% CI: 1.54, 7.65), HIV/tuberculosis confections (AHR = 2.38; 95% CI: 1.23, 4.62), and being female (AHR = 3.12; 95% CI: 1.57, 6.18) were significantly associated with the experience of severe adverse drug reactions.

Conclusion

In this study, the incidence of severe adverse reactions was consistent with the previous studies, and advanced World Health Organization (WHO) clinical stage, HIV/TB confection, and being female were the independent predictors of the severe adverse drug reactions.

Pharmacokinetics, Safety, and Tolerability of Once-Daily Darunavir With Cobicistat and Weekly Isoniazid/Rifapentine

BACKGROUND

Once-weekly isoniazid with rifapentine (HP) for 3 months is a recommended treatment for latent tuberculosis infection in persons with HIV. HP reduces exposures of certain antiretroviral medications, resulting in limited options for the concomitant use of these therapies. Here, we examined the pharmacokinetics (PK), safety, and tolerability of darunavir/cobicistat with HP.

METHODS

This was an open-label, fixed sequence, two-period crossover study in persons without HIV. Participants received darunavir 800 mg/cobicistat 150 mg once-daily alone for 4 days, then continued darunavir/cobicistat once-daily for days 5-19 with HP coadministration on days 5, 12, and 19. Intensive PK assessments were performed on days 4, 14, and 19. PK parameters were determined using noncompartmental methods. Geometric mean ratios with 90% confidence intervals (CIs) were calculated and compared between phases using mixed-effects models.

RESULTS

Thirteen participants were enrolled. Two withdrew after day 4, and one withdrew after day 14. Of the 3 withdrawals, 2 were attributed to drug-related adverse events. Darunavir area under the concentration-time curve, maximum concentrations (Cmax), and concentrations at 24 hours postdose (C24h) were reduced by 71%, 41%, and 96% ∼48-72 hours after HP administration (day 14), respectively, and 36%, 17%, and 89% with simultaneous HP administration (day 19), respectively. On day 14, 45% of the predose and 73% of C24h concentrations were below the darunavir EC50 (0.055 µg/mL).

CONCLUSIONS

Darunavir exposures were significantly decreased with HP coadministration. Temporal relationships between HP coadministration and the extent of induction or mixed inhibition/induction of darunavir metabolism were apparent. Coadministration of darunavir/cobicistat with 3HP should be avoided.

Biktarvy for the treatment of HIV infection: Progress and prospects

Bictegravir (BIC), a second-generation integrase strand-transfer inhibitor (INSTI) with high resilience to INSTI-resistance mutations, is integrated as a key component of Biktarvy® - a fixed-dose once-daily triple-drug regimen of bictegravir (BIC), emtricitabine (FTC) plus tenofovir alafenamide (TAF). Based on the accumulated evidence from HIV clinical trials and real-world studies, the clinical effectiveness of BIC + FTC + TAF has been proven non-inferior to other fixed-dose once-daily combinations such as dolutegravir + FTC + TAF and dolutegravir + abacavir + lamivudine. Biktarvy also shows limited drug-drug interactions and a high barrier to drug resistance. According to recent HIV guidelines, BIC + FTC + TAF is recommended as initial and long-term therapy for the treatment of HIV infection. For the pre-exposure prophylaxis, tenofovir disoproxil fumarate (TDF) or tenofovir alafenamide (TAF) remains advisable, but BIC may be possibly added to TDF or TAF. In the development of a long-acting once-monthly regimen, the novel nano-formulation of BIC + FTC + TAF could be possibly developed in the future.

Innovative Therapeutic Approaches Based on Nanotechnology for the Treatment and Management of Tuberculosis

Tuberculosis (TB), derived from bacterium named Mycobacterium tuberculosis, has become one of the worst infectious and contagious illnesses in the world after HIV/AIDS. Long-term therapy, a high pill burden, lack of compliance, and strict management regimens are disadvantages which resulted in the extensively drug-resistant (XDR) along with multidrug-resistant (MDR) in the treatment of TB. One of the main thrust areas for the current scenario is the development of innovative intervention tools for early diagnosis and therapeutics towards Mycobacterium tuberculosis (MTB). This review discusses various nanotherapeutic agents that have been developed for MTB diagnostics, anti-TB drugs and vaccine. Undoubtedly, the concept of employing nanoparticles (NPs) has strong potential in this therapy and offers impressive outcomes to conquer the disease. Nanocarriers with different types were designed for drug delivery applications via various administration methods. Controlling and maintaining the drug release might be an example of the benefits of utilizing a drug-loaded NP in TB therapy over conventional drug therapy. Furthermore, the drug-encapsulated NP is able to lessen dosage regimen and can resolve the problems of insufficient compliance. Over the past decade, NPs were developed in both diagnostic and therapeutic methods, while on the other hand, the therapeutic system has increased. These "theranostic" NPs were designed for nuclear imaging, optical imaging, ultrasound, imaging with magnetic resonance and the computed tomography, which includes both single-photon computed tomography and positron emission tomography. More specifically, the current manuscript focuses on the status of therapeutic and diagnostic approaches in the treatment of TB.

Care cascade of tuberculosis infection treatment for people living with HIV in the era of antiretroviral therapy scale-up

Testing and treatment of tuberculosis infection (TBI) are recommended for people living with HIV (PLWH). We aimed to evaluate the care cascade of TBI treatment among PLWH in the era of antiretroviral therapy (ART) scale-up. This retrospective study included adult PLWH undergoing interferon-gamma release assay (IGRA)-based TBI screening during 2019–2021. PLWH testing IGRA-positive were advised to receive directly-observed therapy for TBI after active TB disease was excluded. The care cascade was evaluated to identify barriers to TBI management. Among 7951 PLWH with a median age of 38 years and CD4 count of 616 cells/mm³, 420 (5.3%) tested positive and 38 (0.5%) indeterminate for IGRA. The TBI treatment initiation rate was 73.6% (309/420) and the completion rate was 91.9% (284/309). More than 80% of PLWH concurrently received short-course rifapentine-based regimens and integrase strand transfer inhibitor (InSTI)-containing ART. The main barrier to treatment initiation was physicians’ concerns and patients’ refusal (85.6%). The factors associated with treatment non-completion were older age, female, anti-HCV positivity, and higher plasma HIV RNA. Our observation of a high TBI completion rate among PLWH is mainly related to the introduction of short-course rifapentine-based regimens in the InSTI era, which can be the strategy to improve TBI treatment uptake.

Low-Dose Rifabutin Increases Cytotoxicity in Antimitotic-Drug-Treated Resistant Cancer Cells by Exhibiting Strong P-gp-Inhibitory Activity

The cytotoxicity of various antibiotics at low doses in drug-resistant cancer cells was evaluated. Low doses of rifabutin were found to markedly increase the cytotoxicity of various antimitotic drugs, such as vincristine (VIC), to P-glycoprotein (P-gp)-overexpressing antimitotic-drug-resistant KBV20C cells. Rifabutin was also found to exert high levels of P-gp-inhibitory activity at 4 and 24 h posttreatment, suggesting that the cytotoxicity of VIC + rifabutin was mainly due to the direct binding of rifabutin to P-gp and the reduction of VIC efflux by P-gp. The combination of VIC + rifabutin also increased early apoptosis, G2 arrest, and the DNA damaging marker, pH2AX protein. Interestingly, only the combination of VIC + rifabutin induced remarkable levels of cytotoxicity in resistant KBV20C cells, whereas other combinations (VIC + rifampin, VIC + rifapentine, and VIC + rifaximin) induced less cytotoxicity. Such finding suggests that rifabutin specifically increases the cytotoxicity of VIC in KBV20C cells, independent of the toxic effect of the ansamycin antibiotic. Only rifabutin had high P-gp-inhibitory activity, which suggests that its high P-gp-inhibitory activity led to the increased cytotoxicity of VIC + rifabutin. As rifabutin has long been used in the clinic, repositioning this drug for P-gp-overexpressing resistant cancer could increase the availability of treatments for patients with drug-resistant cancer.

Coinfection of Tuberculosis in an Undiagnosed HIV, AIDS Patient Presenting With Shortness of Breath, Constitutional Symptoms and Lymphadenopathy

Tuberculosis (TB) has long been known as an acquired immunodeficiency syndrome (AIDS) defining illness in human immunodeficiency virus (HIV) patients, causing reciprocal advantage for both pathogens throughout the course of the disease, not just constituting a burden for the patient, but also impacting public health globally. We report a case of a 42-year-old man who presented with shortness of breath, generalized lymphadenopathy and weight loss. Subsequently diagnosed with HIV/AIDS and generalized ganglionar TB. Initial computed tomography (CT) of the chest showed extensive mediastinal involvement with large right loculated pleural effusion, with growth of acid-fast bacilli (AFB) on culture. Biopsy of lymph nodes confirmed pathologic changes correlating with M. tuberculosis (Caseating granulomatous inflammation), ruling out the possibility of lymphoproliferative disorder. Multiple factors contribute to the immune system decline in AIDS patients, moreover the rapid depletion of Tuberculosis antigen-specific CD4+ T before generalized CD4+T cells. Early assessment for the presence of co-infection and guidance of targeted therapy is critical for management and an important factor in the expected recovery of such patients. Therefore, understanding the pathogenesis of the co-infection, diagnostic approach, possible complications, and the action of concurrent therapy highly active antiretroviral therapy (HAART)/anti-Tuberculosis treatment as well as drug cytotoxicity is paramount.

Disputed rpoB Mutations in Mycobacterium tuberculosis and Tuberculosis Treatment Outcomes

Discordant results between genotypic drug susceptibility testing (gDST) and phenotypic DST (pDST) for Mycobacterium tuberculosis isolates with disputed (discordance between gDST and pDST results) mutations affect rifampin (RIF)-resistant (RR) and multidrug-resistant (MDR) tuberculosis (TB) treatments due to a lack of practical clinical guidelines. To investigate the role of disputed rpoB mutations in M. tuberculosis and TB treatment outcomes, initial isolates of 837 clinical RR- or MDR-TB cases confirmed during 2014 to 2018 were retested using agar-based RIF pDST and rpoB gene sequencing. MICs were determined for isolates with disputed rpoB mutations. Disputed rpoB mutations were identified in 77 (9.2%) M. tuberculosis isolates, including 50 (64.9%) and 14 (18.2%) phenotypically RIF- and rifabutin (RFB)-resistant isolates, respectively. The predominant single mutations were those encoding L533P (a change of L to P at position 533) (44.2%) and L511P (20.8%). Most of the isolates harboring mutations encoding L511P (87.5%), H526N (100%), D516Y (70.0%), and L533P (63.6%) had MICs of ≤1 mg/liter, whereas isolates harboring the mutation encoding H526L (75%) had a MIC of >1 mg/liter. Of the 63 cases with treatment outcomes available, 11 (17.5%) cases died, 1 (1.6%) case transferred out, and 51 (81%) cases had favorable outcomes, including 8 and 20 cases treated with standard-dose RIF- and RFB-containing regimens, respectively. Excluding cases that transferred out or received no or 1-day treatment, we observed statistically significant differences between the outcomes using active and inactive fluoroquinolones (FQs) (P = 0.008, odds ratio = 0.05 [95% confidence interval, 0.01 to 0.38]) in 57 cases (where active means a case susceptible to the drug and inactive means a case resistant to the drug or drug not used). We concluded that disputed rpoB mutations are not rare. Depending on the resources available, sequencing and/or MIC testing is recommended for better management of RR- and MDR-TB cases.

Advancing our understanding of HIV co-infections and neurological disease using the humanized mouse

Humanized mice have become an important workhorse model for HIV research. Advances that enabled development of a human immune system in immune deficient mouse strains have aided new basic research in HIV pathogenesis and immune dysfunction. The small animal features facilitate development of clinical interventions that are difficult to study in clinical cohorts, and avoid the high cost and regulatory burdens of using non-human primates. The model also overcomes the host restriction of HIV for human immune cells which limits discovery and translational research related to important co-infections of people living with HIV. In this review we emphasize recent advances in modeling bacterial and viral co-infections in the setting of HIV in humanized mice, especially neurological disease, and Mycobacterium tuberculosis and HIV co-infections. Applications of current and future co-infection models to address important clinical and research questions are further discussed.

Factors Associated With and Characteristic of HIV/Tuberculosis Co-Infection: A Retrospective Analysis of SECOND-LINE Clinical Trial Participants

BACKGROUND

Tuberculosis (TB) is a common infection in people living with HIV. However, the risk factors for HIV/TB co-infection in second-line HIV therapy are poorly understood. We aimed to determine the incidence and risk factors for TB co-infection in SECOND-LINE, an international randomized clinical trial of second-line HIV therapy.

METHODS

We did a cohort analysis of TB cases in SECOND-LINE. TB cases included any clinical or laboratory-confirmed diagnoses and/or commencement of treatment for TB after randomization. Baseline factors associated with TB were analyzed using Cox regression stratified by site.

RESULTS

TB cases occurred at sites in Argentina, India, Malaysia, Nigeria, South Africa, and Thailand, in a cohort of 355 of the 541 SECOND-LINE participants. Overall, 20 cases of TB occurred, an incidence rate of 3.4 per 100 person-years (95% CI: 2.1 to 5.1). Increased TB risk was associated with a low CD4+-cell count (≤200 cells/μL), high viral load (>200 copies/mL), low platelet count (<150 ×109/L), and low total serum cholesterol (≤4.5 mmol/L) at baseline. An increased risk of death was associated with TB, adjusted for CD4, platelets, and cholesterol. A low CD4+-cell count was significantly associated with incident TB, mortality, other AIDS diagnoses, and virologic failure.

DISCUSSION

The risk of TB remains elevated in PLHIV in the setting of second-line HIV therapy in TB endemic regions. TB was associated with a greater risk of death. Finding that low CD4+ T-cell count was significantly associated with poor outcomes in this population supports the value of CD4+ monitoring in HIV clinical management.

A Systematic Review on the Effect of HIV Infection on the Pharmacokinetics of First-Line Tuberculosis Drugs

Introduction

Contrasting findings have been published regarding the effect of human immunodeficiency virus (HIV) on tuberculosis (TB) drug pharmacokinetics (PK).

Objectives

The aim of this systematic review was to investigate the effect of HIV infection on the PK of the first-line TB drugs (FLDs) rifampicin, isoniazid, pyrazinamide and ethambutol by assessing all published literature.

Methods

Searches were performed in MEDLINE (through PubMed) and EMBASE to find original studies evaluating the effect of HIV infection on the PK of FLDs. The included studies were assessed for bias and clinical relevance. PK data were extracted to provide insight into the difference of FLD PK between HIV-positive and HIV-negative TB patients. This systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement and its protocol was registered at PROSPERO (registration number CRD42017067250).

Results

Overall, 27 studies were eligible for inclusion. The available studies provide a heterogeneous dataset from which consistent results could not be obtained. In both HIV-positive and HIV-negative TB groups, rifampicin (13 of 15) and ethambutol (4 of 8) peak concentration (C_max) often did not achieve the minimum reference values. More than half of the studies (11 of 20) that included both HIV-positive and HIV-negative TB groups showed statistically significantly altered FLD area under the concentration–time curve and/or C_max for at least one FLD.

Conclusions

HIV infection may be one of several factors that reduce FLD exposure. We could not make general recommendations with respect to the role of dosing. There is a need for consistent and homogeneous studies to be conducted.

Hepatocytic transcriptional signatures predict comparative drug interaction potential of rifamycin antibiotics

Current strategies to treat tuberculosis (TB) and co-morbidities involve multidrug combination therapies. Rifamycin antibiotics are a key component of TB therapy and a common source of drug–drug interactions (DDIs) due to induction of drug metabolizing enzymes (DMEs). Management of rifamycin DDIs are complex, particularly in patients with co-morbidities, and differences in DDI potential between rifamycin antibiotics are not well established. DME profiles induced in response to tuberculosis antibiotics (rifampin, rifabutin and rifapentine) were compared in primary human hepatocytes. We identified rifamycin induced DMEs, cytochrome P450 (CYP) 2C8/3A4/3A5, SULT2A, and UGT1A4/1A5 and predicted lower DDIs of rifapentine with 58 clinical drugs used to treat co-morbidities in TB patients. Transcriptional networks and upstream regulator analyses showed FOXA3, HNF4α, NR1I2, NR1I3, NR3C1 and RXRα as key transcriptional regulators of rifamycin induced DMEs. Our study findings are an important resource to design effective medication regimens to treat common co-conditions in TB patients.

Pharmacokinetic study of two different rifabutin doses co-administered with lopinavir/ritonavir in African HIV and tuberculosis co-infected adult patients

Background

This study aimed to assess the pharmacokinetic profile of 150 mg rifabutin (RBT) taken every other day (every 48 h) versus 300 mg RBT taken every other day (E.O.D), both in combination with lopinavir/ritonavir (LPV/r), in adult patients with human immunodeficiency virus (HIV) and tuberculosis (TB) co-infection.

Methods

This is a two-arm, open-label, pharmacokinetic, randomised study conducted in Burkina Faso between May 2013 and December 2015. Enrolled patients were randomised to receive either 150 mg RBT EOD (arm A, 9 subjects) or 300 mg RBT EOD (arm B, 7 subjects), both associated with LPV/r taken twice daily. RBT plasma concentrations were evaluated after 2 weeks of combined HIV and TB treatment. Samples were collected just before drug ingestion and at 1, 2, 3, 4, 6, 8, and 12 h after drug ingestion to measure plasma drug concentration using an HPLC-MS/MS assay.

Results

The Cmax and AUC_0–12h medians in arm A (Cmax = 296 ng/mL, IQR: 205–45; AUC_0–12h = 2528 ng.h/mL, IQR: 1684–2735) were lower than those in arm B (Cmax = 600 ng/mL, IQR: 403–717; AUC_0–12h = 4042.5 ng.h/mL, IQR: 3469–5761), with a statistically significant difference in AUC_0–12h (p = 0.044) but not in Cmax (p = 0.313). No significant differences were observed in Tmax (3 h versus 4 h). Five patients had a Cmax below the plasma therapeutic limit (< 300 ng/mL) in the 150 mg RBT arm, while the Cmax was above this threshold for all patients in the 300 mg RBT arm. Additionally, at 48 h after drug ingestion, all patients had a mycobacterial minimum inhibitory concentration (MIC) above the limit (> 64 ng/mL) in the 300 mg RBT arm, while 4/9 patients had such values in the 150 mg RBT arm.

Conclusion

This study confirmed that the 150 mg dose of rifabutin ingested EOD in combination with LPV/r is inadequate and could lead to selection of rifamycin-resistant mycobacteria.

Trial registration

PACTR201310000629390, 28th October 2013.

Twice-Daily Doravirine Overcomes the Interaction Effect from Once-Weekly Rifapentine and Isoniazid in Healthy Volunteers

Doravirine (DOR) is a non‐nucleoside reverse transcriptase inhibitor indicated for the treatment of HIV‐1. Its use in combination with rifapentine (RPT), an antituberculosis (TB) antibiotic, may reduce the exposure of DOR compromising viral suppression in those living with HIV‐1 co‐infected with TB. We conducted a prospective, phase I, open label, two‐period, fixed sequence, drug interaction study to evaluate the effect of once‐weekly RPT and isoniazid (INH) on the pharmacokinetics (PKs) of DOR in healthy volunteers. DOR 100 mg was administered alone twice‐daily for 4 days in period 1. In period 2, once‐weekly RPT + INH were co‐administered with multiple doses of DOR 100 mg twice‐daily for study days 7, 14, and 21. Plasma was obtained for DOR PKs when given alone and co‐administered with RPT + INH. Eleven healthy volunteers enrolled and completed the study. The geometric mean ratios and 90% confidence intervals for DOR area under the concentration‐time curve from zero to 12 hours (AUC_0–12) and C₁₂ in the presence of RPT + INH compared with DOR alone were 0.71 (0.60–0.85) and 0.69 (0.54–0.89), respectively. Although exposures were moderately reduced in the presence of RPT + INH, trough DOR values were within the concentration range associated with virological suppression. These results demonstrate that a modest decrease in DOR exposure would unlikely be clinically relevant in a virally suppressed patient co‐administered once‐weekly RPT + INH.

Pharmacokinetics of plasma lopinavir and ritonavir in tuberculosis-HIV co-infected African adult patients also receiving rifabutin 150 or 300 mg three times per week

BACKGROUND

To evaluate the pharmacokinetic of plasma lopinavir (LPV) and ritonavir (RTV) when co-administered with three times weekly (TPW) rifabutin (RBT) at a dose of either 150 or 300 mg in African tuberculosis (TB) and HIV co-infected adult patients.

METHODS

This is a pharmacokinetic study conducted in Ouagadougou among patients treated with a standard dosage of LPV/RTV 400/100 mg twice daily and RBT 150 mg TPW (arm A = 9 patients) or rifabutin 300 mg TPW (arm B = 7 patients) based regimens. Patients were recruited from the Bogodogo and Kossodo district hospitals in Ouagadougou from May 2013 to December 2015. Study inclusion criteria were that the patients were between 18 and 60 years of age, HIV-1 infected with pulmonary tuberculosis confirmed or suspected. Subsequent blood samples for pharmacokinetic monitoring were collected at 1, 2, 3, 4, 6, 8 and 12 h after combined drug ingestion for plasma drug monitoring using HPLC/MS assays.

RESULTS

The medians LPV C_max and T_max were respectively, 20 μg/mL and 4 h for the RBT 150 mg group (arm A) and 7.7 μg/mL and 3 h for the RBT 300 mg group (arm B). The AUC_0-12 of LPV was 111.8 μg h/mL in patients belonging to arm A versus 69.9 μg/mL for those in arm B (p = 0.313). The C₀ of LPV was lower than 4 μg/mL in three patients receiving RBT 300 mg. Of note, the RTV plasma concentrations were nearly halved among patients on RBT 300 mg compared to those on lower RBT doses. The AUC_0-12 of RTV in arm A was 12.7 μg h/mL versus 6.6 μg h/ml in arm B (p = 0.313).

CONCLUSION

In our study, the pharmacokinetic of LPV and RTV was found to be highly variable when coadministrated with RBT 150 mg or 300 mg three times per week. There is a need for specific large study to verify clinical and virological effects of this variation, especially when coadministrated with RBT of 300 mg TPW, and to prevent viral resistance in response to under-dosing of LPV. Trial registration PACTR201310000629390. Registered 28 October 2013, http://www.pactr.org/.

A drug interaction study investigating the effect of Rifabutin on the pharmacokinetics of Maraviroc in healthy subjects

Effects of steady-state rifabutin on the pharmacokinetics of steady-state maraviroc were investigated in fourteen healthy adult female and male volunteers. Maraviroc 300 mg twice daily (BID) was given orally with food for fifteen days. On day six, rifabutin 300 mg once daily (QD, P.O.) was added to the regimen. Formal pharmacokinetic (PK) sampling was performed on days five and fifteen. Individual plasma drug concentration-time data for maraviroc, and rifabutin on day fifteen, were obtained using validated High Performance Liquid Chromatography (HPLC) tandem Mass Spectrometry (MS/MS). Rifabutin steady state exposure was comparable to data in the literature. Maraviroc area under the curve (AUC) and minimum plasma concentration (C_last or C_min) were reduced by 17% and 30% respectively when co-administered with rifabutin. No unexpected or serious adverse eventsoccurred. Based on the reduced exposure of maraviroc observed in this study, increasing the dose of maraviroc may be studied to normalize its moderately reduced exposure following rifabutin co-administration, a moderate inducer of CYP3A4.

Mycobacterium tuberculosis infections in solid organ transplantation: Guidelines from the infectious diseases community of practice of the American Society of Transplantation

These updated guidelines from the Infectious Diseases Community of Practice of the American Society of Transplantation review the diagnosis, prevention, and management of tuberculosis in the pre- and post-transplant period. The challenges of screening for both latent and active TB in the setting of transplantation are reviewed. The use of interferon gamma release assays for detection of latent tuberculosis is discussed and compared to tuberculin skin testing. Given the limitations of both testing modality, it is important to consider exposure history and chest imaging. The clinical manifestations of active tuberculosis in transplantation are covered. New recommendations for treatment of latent tuberculosis and active tuberculosis are included.

rpoB Mutations Causing Discordant Rifampicin Susceptibility in Mycobacterium tuberculosis: Retrospective Analysis of Prevalence, Phenotypic, Genotypic, and Treatment Outcomes

Background

Discordant genotypic/phenotypic rifampicin susceptibility testing in Mycobacterium tuberculosis is a significant challenge, yet there are limited data on its prevalence and how best to manage such patients. Whether to treat isolates with rpoB mutations not conferring phenotypic resistance as susceptible or multidrug-resistant tuberculosis (MDR-TB) is unknown. We describe phenotypic and genotypic characteristics of discordant isolates and clinical characteristics and treatment outcomes of affected patients in KwaZulu-Natal, South Africa.

Methods

We analyzed clinical isolates showing rifampicin resistance on GenoType MTBDRplus while susceptible on 1% agar proportion method. We measured rifampicin minimum inhibitory concentrations (MICs) using Middlebrook 7H10 agar dilution and BACTEC MGIT 960. Sensititre MYCOTB plates were used for drug-susceptibility testing, and rpoB gene sequencing was performed on all isolates. Local MDR-TB program data were reviewed for clinical information and patient outcomes.

Results

Discordant isolates constituted 4.6% (60) of 1302 rifampicin-resistant cases over the study period. Of these, 62% remained susceptible to isoniazid and 98% remained susceptible to rifabutin. Rifampicin MICs were close to the critical concentration of 1 µg/mL (0.5–2 µg/mL) for 83% of isolates. The most frequent rpoB mutations were Q513P (25.3%), D516V (19.2%), and D516Y (13.3%). Whereas 70% were human immunodeficiency virus infected, the mean CD4 count was 289 cells/mm³ and 87% were receiving antiretroviral therapy. Standard therapy for MDR-TB was used and 53% achieved successful treatment outcomes.

Conclusions

Rifampicin-discordant TB is not uncommon and sequencing is required to confirm results. The high susceptibility to rifabutin and isoniazid and poor treatment outcomes with the current regimen suggest a potential utility for rifabutin-based therapy.

Tuberculosis-HIV treatment with rifampicin or rifabutin: are the outcomes different?

BACKGROUND

Rifamycins are a group of antibiotics mainly used in the treatment of tuberculosis (TB), however they interact with antiretroviral therapy (ART). Rifabutin allows more regimens options for concomitant imunodeficiency virus (HIV) treatment compared to rifampicin.

OBJECTIVE

Compare the outcomes of TB-HIV co-infected patients who used rifampicin or rifabutin.

METHODS

We analysed data from a prospective cohort study at National Institute of Infectious Diseases Evandro Chagas, Rio de Janeiro (RJ), Brazil. Patients who were treated for TB and HIV with rifampicin or rifabutin, from February 2011 to September 2016 were included.

FINDINGS

There were 130 TB-HIV patients, of whom 102 were treated with rifampicin and 28 with rifabutin. All patients in the rifabutin-treated group and 55% of the rifampicin-treated group patients were ART-experienced. Patients treated with rifampicin had similar abandon and cure rates, interruptions in treatment due to adverse reactions, immune reconstitution inflammatory syndrome and a similar mortality rate as those treated with rifabutin. However, rifampicin-treated patients had higher CD4 counts and more frequently undetectable HIV viral load by the end of treatment (67% versus 18%, p < 0.001) compared to rifabutin-treated patients, even when only ART-experienced patients were evaluated (66,6% versus 36,3%, p = 0.039).

CONCLUSIONS

Patients who used rifabutin had worst immune and virological control. This group had more ART-experienced patients. New and simpler regimens are needed for patients who do not respond to previous antiretroviral therapies.

The potential use of rifabutin for treatment of patients diagnosed with rifampicin-resistant tuberculosis

Background

Use of the Xpert MTB/RIF assay has increased the number of people diagnosed with rifampicin-resistant tuberculosis (RR-TB), especially in South Africa where Xpert is now the initial diagnostic for individuals with TB symptoms. We hypothesized that a proportion of RR-TB patients determined by Xpert can be treated with a rifabutin-containing regimen.

Methods

Rifabutin susceptibility by rpoB mutation was assessed in 349 individuals from South Africa and 172 from Belgium. rpoB polymorphisms were identified by Sanger sequencing. Rifampicin and rifabutin susceptibility was assessed phenotypically. A systematic review was performed to comprehensively collate information on rifabutin susceptibility by rpoB polymorphism. Rifabutin susceptibility was assigned to rpoB polymorphisms based on their positive likelihood ratios and ORs.

Results

One hundred and twelve rpoB polymorphisms (67.9% from literature) were identified from all 2045 RR-TB patients, of which 17 polymorphisms could be classified as susceptible/resistant to rifabutin. Eleven polymorphisms were associated with rifabutin susceptibility. The 516GTC mutation was the most common, representing 70% (South Africa) and 76% (Belgium) of all rifabutin-susceptible isolates. At a population level, the 11 polymorphisms associated with rifabutin susceptibility occurred in 33.2% and 16.6% of all South African and Belgian patients diagnosed with RR-TB, respectively.

Conclusions

Identification of the exact rpoB polymorphism leading to the diagnosis of RR-TB has the potential to allow inclusion of rifabutin in the treatment regimen of a substantial proportion of RR-TB patients. A randomized controlled trial evaluating the efficacy of a rifabutin-containing TB treatment regimen in these selected patients is needed to provide the evidence required for a change in policy.

HIV-associated opportunistic CNS infections: pathophysiology, diagnosis and treatment

Nearly 30 years after the advent of antiretroviral therapy (ART), CNS opportunistic infections remain a major cause of morbidity and mortality in HIV-positive individuals. Unknown HIV-positive disease status, antiretroviral drug resistance, poor drug compliance, and recreational drug abuse are factors that continue to influence the morbidity and mortality of infections. The clinical and radiographic pattern of CNS opportunistic infections is unique in the setting of HIV infection: opportunistic infections in HIV-positive patients often have characteristic clinical and radiological presentations that can differ from the presentation of opportunistic infections in immunocompetent patients and are often sufficient to establish the diagnosis. ART in the setting of these opportunistic infections can lead to a paradoxical worsening caused by an immune reconstitution inflammatory syndrome (IRIS). In this Review, we discuss several of the most common CNS opportunistic infections: cerebral toxoplasmosis, progressive multifocal leukoencephalopathy (PML), tuberculous meningitis, cryptococcal meningitis and cytomegalovirus infection, with an emphasis on clinical pearls, pathological findings, MRI findings and treatment. Moreover, we discuss the risk factors, pathophysiology and management of IRIS. We also summarize the challenges that remain in management of CNS opportunistic infections, which includes the lack of phase II and III clinical trials, absence of antimicrobials for infections such as PML, and controversy regarding the use of corticosteroids for treatment of IRIS.

Antiretroviral Therapy in HIV-Infected Children With Tuberculosis: A Systematic Review

BACKGROUND

Tuberculosis (TB) is the major cause of mortality in HIV-infected children globally. Current guidelines about the management of antiretroviral therapy in children with TB are based on a limited number of nonrandomized studies involving small numbers of participants. The aim of the study was to systematically retrieve and critically appraise available evidence on the efficacy and safety of different antiretroviral regimens in children with HIV infection who are receiving treatment for active TB.

METHODS

We conducted a systematic review of the literature according to Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines. Records were retrieved through March 2016 from Medline, Embase and manual screening of key conference proceedings. Four specific research questions assessing available treatment options were defined.

RESULTS

Although 4 independent searches were conducted (1 for each Population, Intervention, Comparator, Outcomes question), results were elaborated and interpreted together because of significant overlap among the retrieved records. Six observational studies were selected for qualitative synthesis while meta-analysis could not be performed.

CONCLUSION

Evidence for optimal treatment options for HIV/TB coinfected children is limited. As the global community strives to reach the fast-track HIV treatment targets and eliminate childhood TB deaths, it must ensure that coinfected children are included in key treatment studies and expand this neglected but crucial area of research.

Modalities to monitor the treatment response in tuberculosis

Considering the global epidemic of drug resistance in Mycobacterium tuberculosis, early and accurate diagnosis as well as prompt initiation of antitubercular therapy (ATT) forms the mainstay of tuberculosis control programs. Patients on ATT may develop treatment failure due to diverse reasons including emergence of drug resistance in the host during the course of therapy. Monitoring the timely response to treatment in such cases has a significant role in rapid identification of drug resistant strains and institution of change of regimen to further decrease the morbidity and mortality associated with the disease. Furthermore, availability of faster surrogate end points to assess treatment efficacy, disease activity, cure, and relapse is one of the crucial requirements for undertaking innovative clinical trials related to TB. The article presents here the compilation of currently available methods for monitoring the treatment response in pulmonary as well as extrapulmonary TB.

New antituberculous drugs derived from natural products: current perspectives and issues in antituberculous drug development

Tuberculosis is one of the most common and challenging infectious diseases worldwide. Especially, the lack of effective chemotherapeutic drugs for tuberculosis/human immunodeficiency virus co-infection and prevalence of multidrug-resistant and extensively drug-resistant tuberculosis remain to be serious clinical problems. Development of new drugs is a potential solution to fight tuberculosis. In this decade, the development status of new antituberculous drugs has been greatly advanced by the leading role of international organizations such as the Global Alliance for Tuberculosis Drug Development, Stop Tuberculosis Partnership and Global Health Innovative Technology Fund. In this review, we introduce the development status of new drugs for tuberculosis, focusing on those derived from natural products.The Journal of Antibiotics advance online publication, 1 November 2017; doi:10.1038/ja.2017.126.

Antiretroviral Therapy With Efavirenz Accentuates Pregnancy-Associated Reduction of Dihydroartemisinin-Piperaquine Exposure During Malaria Chemoprevention

Dihydroartemisinin (DHA)-piperaquine is promising for malaria chemoprevention in pregnancy. We assessed the impacts of pregnancy and efavirenz-based antiretroviral therapy on exposure to DHA and piperaquine in pregnant Ugandan women. Intensive sampling was performed at 28 weeks gestation in 31 HIV-uninfected pregnant women, in 27 HIV-infected pregnant women receiving efavirenz, and in 30 HIV-uninfected nonpregnant women. DHA peak concentration and area under the concentration time curve (AUC0-8hr ) were 50% and 47% lower, respectively, and piperaquine AUC0-21d was 40% lower in pregnant women compared to nonpregnant women. DHA AUC0-8hr and piperaquine AUC0-21d were 27% and 38% lower, respectively, in pregnant women receiving efavirenz compared to HIV-uninfected pregnant women. Exposure to DHA and piperaquine were lower among pregnant women and particularly in women on efavirenz, suggesting a need for dose modifications. The study of modified dosing strategies for these populations is urgently needed.

The Role of Efflux Pumps in Tuberculosis Treatment and Their Promise as a Target in Drug Development: Unraveling the Black Box

Insight into drug transport mechanisms is highly relevant to the efficacious treatment of tuberculosis (TB). Major problems in TB treatment are related to the transport of antituberculosis (anti-TB) drugs across human and mycobacterial membranes, affecting the concentrations of these drugs systemically and locally. Firstly, transporters located in the intestines, liver, and kidneys all determine the pharmacokinetics and pharmacodynamics of anti-TB drugs, with a high risk of drug-drug interactions in the setting of concurrent use of antimycobacterial, antiretroviral, and antidiabetic agents. Secondly, human efflux transporters limit the penetration of anti-TB drugs into the brain and cerebrospinal fluid, which is especially important in the treatment of TB meningitis. Finally, efflux transporters located in the macrophage and Mycobacterium tuberculosis cell membranes play a pivotal role in the emergence of phenotypic tolerance and drug resistance, respectively. We review the role of efflux transporters in TB drug disposition and evaluate the promise of efflux pump inhibition from a novel holistic perspective.

Role of the Health Department in Tuberculosis Prevention and Control-Legal and Public Health Considerations

Because tuberculosis is caused by an infectious organism that is spread from person to person through the air, public health measures are essential to control the disease. There are three priority strategies for tuberculosis prevention and control in the United States: (i) identifying and treating persons who have tuberculosis disease; (ii) finding persons exposed to infectious tuberculosis patients, evaluating them for Mycobacterium tuberculosis infection and disease, and providing subsequent treatment, if appropriate; and (iii) testing populations at high risk for latent tuberculosis infection (LTBI) and treating those persons who are infected to prevent progression to disease. These strategies for prevention and control of tuberculosis are discussed in a framework containing the following important topics: historical and epidemiological context of tuberculosis control, organization of public health tuberculosis control programs, legal basis for public health authority, conducting overall planning and development of policy, identifying persons who have clinically active tuberculosis, evaluation of immigrants, managing persons who have or who are suspected of having disease, medical consultation, interjurisdictional referrals, identifying and managing persons infected with Mycobacterium tuberculosis, providing laboratory and diagnostic services, collecting and analyzing data, and providing training and education. This chapter describes the role of the health department in the context of these components. This discussion is primarily applicable to tuberculosis prevention and control programs in the United States.

Interaction of Rifampin and Darunavir-Ritonavir or Darunavir-Cobicistat In Vitro

Treatment of HIV-infected patients coinfected with Mycobacterium tuberculosis is challenging due to drug-drug interactions (DDIs) between antiretrovirals (ARVs) and antituberculosis (anti-TB) drugs. The aim of this study was to quantify the effect of cobicistat (COBI) or ritonavir (RTV) in modulating DDIs between darunavir (DRV) and rifampin (RIF) in a human hepatocyte-based in vitro model. Human primary hepatocyte cultures were incubated with RIF alone or in combination with either COBI or RTV for 3 days, followed by coincubation with DRV for 1 h. The resultant DRV concentrations were quantified by high-performance liquid chromatography with UV detection, and the apparent intrinsic clearance (CL_int.app.) of DRV was calculated. Both RTV and COBI lowered the RIF-induced increases in CL_int.app. in a concentration-dependent manner. Linear regression analysis showed that log₁₀ RTV and log₁₀ COBI concentrations were associated with the percent inhibition of RIF-induced elevations in DRV CL_int.app., where β was equal to -234 (95% confidence interval [CI] = -275 to -193; P < 0.0001) and -73 (95% CI = -89 to -57; P < 0.0001), respectively. RTV was more effective in lowering 10 μM RIF-induced elevations in DRV CL_int.app. (half-maximal [50%] inhibitory concentration [IC₅₀] = 0.025 μM) than COBI (IC₅₀ = 0.223 μM). Incubation of either RTV or COBI in combination with RIF was sufficient to overcome RIF-induced elevations in DRV CL_int.app., with RTV being more potent than COBI. These data provide the first in vitro experimental insight into DDIs between RIF and COBI-boosted or RTV-boosted DRV and will be useful to inform physiologically based pharmacokinetic (PBPK) models to aid in optimizing dosing regimens for the treatment of patients coinfected with HIV and M. tuberculosis.

The cursed duet today: Tuberculosis and HIV-coinfection

The tuberculosis (TB) and HIV syndemic continues to rage and are a major public health concern worldwide. This deadly association raises complexity and represent a significant barrier towards TB elimination. TB continues to be the leading cause of death amongst HIV-infected people. This paper reports the challenges that lay ahead and outlines some of the current and future strategies that may be able to address this co-epidemic efficiently. Improved diagnostics, cheaper and more effective drugs, shorter treatment regimens for both drug-sensitive and drug-resistant TB are discussed. Also, special topics on drug interactions, TB-IRIS and TB relapse are also described. Notwithstanding the defeats and meagre investments, diagnosis and management of the two diseases have seen significant and unexpected improvements of late. On the HIV side, expansion of ART coverage, development of new updated guidelines aimed at the universal treatment of those infected, and the increasing availability of newer, more efficacious and less toxic drugs are an essential element to controlling the two epidemics. On the TB side, diagnosis of MDR-TB is becoming easier and faster thanks to the new PCR-based technologies, new anti-TB drugs active against both sensitive and resistant strains (i.e. bedaquiline and delamanid) have been developed and a few more are in the pipeline, new regimens (cheaper, shorter and/or more effective) have been introduced (such as the "Bangladesh regimen") or are being tested for MDR-TB and drug-sensitive-TB. However, still more resources will be required to implement an integrated approach, install new diagnostic tests, and develop simpler and shorter treatment regimens.

Prediction of area under the concentration-time curve for lopinavir from peak or trough lopinavir concentrations in patients receiving lopinavir-ritonavir therapy

PURPOSE

A "single time point" strategy for predicting the area under the concentration-time curve (AUC) for lopinavir in patients receiving ritonavir-boosted lopinavir therapy was investigated.

METHODS

Linear regression equations describing the relationships of lopinavir peak and trough concentrations to lopinavir AUC values were established using pharmacokinetic data from published studies of patients or healthy subjects receiving lopinavir and ritonavir at standard dosages. The resulting "trough-AUC model" and "peak-AUC model" were used to predict lopinavir AUC values in the evaluated study populations (total n = 479); those values were then compared with reported AUC values.

RESULTS

Lopinavir peak or trough concentrations were strongly correlated with lopinavir AUC values (r = 0.9947 and r = 0.9541, respectively). For about 94% of calculations using the peak-AUC model and 87% of calculations using the trough-AUC model, differences between predicted and observed AUC values were in the range of 0.76-1.5 fold; the associated r values were 0.9514 (p < 0.001) and 0.9345 (p < 0.001), respectively. The mean absolute predictive error was less than 6% with the use of either the peak-AUC model or the trough-AUC model, with corresponding values for root-mean-square error of 17.6% and 23.5%, respectively.

CONCLUSION

Equations incorporating lopinavir peak and trough concentrations were found to satisfactorily predict lopinavir AUC values in data sets describing patients receiving lopinavir with ritonavir boosting. Variability in predictions was higher with use of the trough-AUC model.

Correlation of rpoB Mutations with Minimal Inhibitory Concentration of Rifampin and Rifabutin in Mycobacterium tuberculosis in an HIV/AIDS Endemic Setting, South Africa

Treatment of tuberculosis (TB) and HIV co-infections is often complicated by drug-to-drug interactions between anti-mycobacterial and anti-retroviral agents. Rifabutin (RFB) is an alternative to rifampin (RIF) for TB regimens and is recommended for HIV patients concurrently receiving protease inhibitors because of reduced induction of CYP3A4. This study sought to determine the proportion of RFB susceptible isolates among RIF-resistant strains in a high HIV prevalence setting in South Africa. In addition, the study explored the association between rpoB mutations and minimum inhibitory concentrations (MIC) of RIF and RFB. A total of 189 multidrug resistant (MDR) Mycobacterium tuberculosis isolates from the Centre for Tuberculosis repository were analyzed. The MICs were determined using a MYCOTB Sensititre plate method and the rpoB gene was sequenced. Of the 189 MDR isolates, 138 (73%) showed resistance to both RIF and RFB, while 51 (27%) isolates were resistant to RIF but retained susceptibility to RFB. The S531L was the most frequent rpoB point mutation in 105/189 (56%) isolates, followed by H526Y in 27/189 (14%) isolates. Resistance to both RIF and RFB was found predominantly in association with mutations S531L (91/105, 87%), H526Y (20/27, 74%), and H526D (15/19, 79%), while D516V (15/17, 88%), and L533P (3/4, 75%) were found in RIF-resistant, RFB-susceptible isolates. This study has shown that up to 27% of MDR-TB patients in South Africa may benefit from a treatment regimen that includes RFB.

Rifapentine for the treatment of latent tuberculosis

INTRODUCTION

The goal of this article is to review the use of rifapentine in the treatment of latent tuberculosis infection (LTBI). Controlling LTBI is an important part of the global strategy to end the spread of tuberculosis. Rifapentine's potent sterilizing effect against Mycobacterium tuberculosis combined with its long half-life make it an attractive LTBI treatment option. Areas covered: A systematic literature search of Pubmed using the terms 'rifapentine' and 'tuberculosis' was performed. Articles identified were cross-referenced for other relevant publications. The mechanisms of action and resistance, pharmacokinetic and pharmacodynamics, potential drug interactions and side effects are discussed. Expert commentary: Rifapentine in combination with isoniazid for twelve weeks is the best available option for treating latent TB in the majority of patients in the United States due to its favorable safety profile and the increased likelihood of completing therapy. Currently, rifapentine is not registered or available in other countries.

Rifamycins, Alone and in Combination

Rifamycins inhibit RNA polymerase of most bacterial genera. Rifampicin remains part of combination therapy for treating tuberculosis (TB), and for treating Gram-positive prosthetic joint and valve infections, in which biofilms are prominent. Rifabutin has use for AIDS patients in treating mycobacterial infections TB and Mycobacterium avium complex (MAC), having fewer drug-drug interactions that interfere with AIDS medications. Rifabutin is occasionally used in combination to eradicate Helicobacter pylori (peptic ulcer disease). Rifapentine has yet to fulfill its potential in reducing time of treatment for TB. Rifaximin is a monotherapeutic agent to treat gastrointestinal (GI) disorders, such as hepatic encephalopathy, irritable bowel syndrome, and travelers' diarrhea. Rifaximin is confined to the GI tract because it is not systemically absorbed on oral dosing, achieving high local concentrations, and showing anti-inflammatory properties in addition to its antibacterial activity. Resistance issues are unavoidable with all the rifamycins when the bioburden is high, because of mutations that modify RNA polymerase.

Population pharmacokinetic drug-drug interaction pooled analysis of existing data for rifabutin and HIV PIs

OBJECTIVES

Extensive but fragmented data from existing studies were used to describe the drug-drug interaction between rifabutin and HIV PIs and predict doses achieving recommended therapeutic exposure for rifabutin in patients with HIV-associated TB, with concurrently administered PIs.

METHODS

Individual-level data from 13 published studies were pooled and a population analysis approach was used to develop a pharmacokinetic model for rifabutin, its main active metabolite 25-O-desacetyl rifabutin (des-rifabutin) and drug-drug interaction with PIs in healthy volunteers and patients who had HIV and TB (TB/HIV).

RESULTS

Key parameters of rifabutin affected by drug-drug interaction in TB/HIV were clearance to routes other than des-rifabutin (reduced by 76%-100%), formation of the metabolite (increased by 224% in patients), volume of distribution (increased by 606%) and distribution to the peripheral compartment (reduced by 47%). For des-rifabutin, clearance was reduced by 35%-76% and volume of distribution increased by 67%-240% in TB/HIV. These changes resulted in overall increased exposure to rifabutin in TB/HIV patients by 210% because of the effects of PIs and 280% with ritonavir-boosted PIs.

CONCLUSIONS

Given together with non-boosted or ritonavir-boosted PIs, rifabutin at 150 mg once daily results in similar or higher exposure compared with rifabutin at 300 mg once daily without concomitant PIs and may achieve peak concentrations within an acceptable therapeutic range. Although 300 mg of rifabutin every 3 days with boosted PI achieves an average equivalent exposure, intermittent doses of rifamycins are not supported by current guidelines.

HIV-Associated TB Syndemic: A Growing Clinical Challenge Worldwide

The association of tuberculosis (TB) with human immunodeficiency virus (HIV) infection and acquired immune deficiency syndrome over the past several years has become an emerging syndemic. Approximately 10% of people living with HIV (PLHIV) with latent TB infection will develop active TB disease each year. In this review, we highlight that this phenomenon is not limited to high endemic regions, such as Afro-Asian nations, but globalization/migration is causing increased case detection even in developed nations, such as the United States. Active screening should be performed for TB in PLHIV. A high degree of clinical suspicion for TB is warranted in PLHIV presenting with fever, cough, and unintentional weight loss. HIV-Mycobacterium tuberculosis (MTB) coinfection is often paucibacillary, precluding diagnosis by conventional diagnostics and/or smear microscopy/culture. Improved detection of pulmonary and extrapulmonary TB is now possible by incorporation of the GeneXPERT MTB/RIF assay (Cepheid Inc., Sunnyvale, CA, USA). The World Health Organization recommends instituting immediate therapy for MTB, in conjunction with ongoing or newly introduced anti-retroviral therapy. Vigilance is required to detect drug-induced organ injuries, and early-treatment-induced immune reconstitution inflammatory syndrome. Collaborating MTB and HIV activities in concentrated HIV epidemic settings should become a high public health priority.

Role of MRP transporters in regulating antimicrobial drug inefficacy and oxidative stress-induced pathogenesis during HIV-1 and TB infections

Multi-Drug Resistance Proteins (MRPs) are members of the ATP binding cassette (ABC) drug-efflux transporter superfamily. MRPs are known to regulate the efficacy of a broad range of anti-retroviral drugs (ARV) used in highly active antiretroviral therapy (HAART) and antibacterial agents used in Tuberculus Bacilli (TB) therapy. Due to their role in efflux of glutathione (GSH) conjugated drugs, MRPs can also regulate cellular oxidative stress, which may contribute to both HIV and/or TB pathogenesis. This review focuses on the characteristics, functional expression, and modulation of known members of the MRP family in HIV infected cells exposed to ARV drugs and discusses their known role in drug-inefficacy in HIV/TB-induced dysfunctions. Currently, nine members of the MRP family (MRP1-MRP9) have been identified, with MRP1 and MRP2 being the most extensively studied. Details of the other members of this family have not been known until recently, but differential expression has been documented in inflammatory tissues. Researchers have found that the distribution, function, and reactivity of members of MRP family vary in different types of lymphocytes and macrophages, and are differentially expressed at the basal and apical surfaces of both endothelial and epithelial cells. Therefore, the prime objective of this review is to delineate the role of MRP transporters in HAART and TB therapy and their potential in precipitating cellular dysfunctions manifested in these chronic infectious diseases. We also provide an overview of different available options and novel experimental strategies that are being utilized to overcome the drug resistance and disease pathogenesis mediated by these membrane transporters.

Factors Associated with the Development of Drug Resistance Mutations in HIV-1 Infected Children Failing Protease Inhibitor-Based Antiretroviral Therapy in South Africa

OBJECTIVE

Limited data are available from the developing world on antiretroviral drug resistance in HIV-1 infected children failing protease inhibitor-based antiretroviral therapy, especially in the context of a high tuberculosis burden. We describe the proportion of children with drug resistance mutations after failed protease inhibitor-based antiretroviral therapy as well as associated factors.

METHODS

Data from children initiated on protease inhibitor-based antiretroviral therapy with subsequent virological failure referred for genotypic drug resistance testing between 2008 and 2012 were retrospectively analysed. Frequencies of drug resistance mutations were determined and associations with these mutations identified through logistic regression analysis.

RESULTS

The study included 65 young children (median age 16.8 months [IQR 7.8; 23.3]) with mostly advanced clinical disease (88.5% WHO stage 3 or 4 disease), severe malnutrition (median weight-for-age Z-score -2.4 [IQR -3.7;-1.5]; median height-for-age Z-score -3.1 [IQR -4.3;-2.4]), high baseline HIV viral load (median 6.04 log10, IQR 5.34;6.47) and frequent tuberculosis co-infection (66%) at antiretroviral therapy initiation. Major protease inhibitor mutations were found in 49% of children and associated with low weight-for-age and height-for-age (p = 0.039; p = 0.05); longer duration of protease inhibitor regimens and virological failure (p = 0.001; p = 0.005); unsuppressed HIV viral load at 12 months of antiretroviral therapy (p = 0.001); tuberculosis treatment at antiretroviral therapy initiation (p = 0.048) and use of ritonavir as single protease inhibitor (p = 0.038). On multivariate analysis, cumulative months on protease inhibitor regimens and use of ritonavir as single protease inhibitor remained significant (p = 0.008; p = 0.033).

CONCLUSION

Major protease inhibitor resistance mutations were common in this study of HIV-1-infected children, with the timing of tuberculosis treatment and subsequent protease inhibitor dosing strategy proving to be important associated factors. There is an urgent need for safe, effective, and practicable HIV/tuberculosis co-treatment in young children and the optimal timing of treatment, optimal dosing of antiretroviral therapy, and alternative tuberculosis treatment strategies should be urgently addressed.

Pharmacokinetic and Pharmacodynamic Comparison of Once-Daily Efavirenz (400 mg vs. 600 mg) in Treatment-Naïve HIV-Infected Patients: Results of the ENCORE1 Study

Daily efavirenz 400 mg (EFV400) was virologically noninferior to 600 mg (EFV600) at 48 weeks in treatment‐naïve patients. We evaluated EFV400 and EFV600 pharmacokinetics (NONMEM v. 7.2), assessing patient demographics and genetic polymorphisms (CYP2B6, CYP2A6, CYP3A4, NR1I3) as covariates and explored relationships with efficacy (plasma HIV‐RNA (pVL) <200 copies/mL) and safety outcomes at 48 weeks in 606 randomized ENCORE1 patients (female = 32%, African = 37%, Asian = 33%; EFV400 = 311, EFV600 = 295). CYP2B6 516G>T/983T>C/CYP2A6*9B/*17 and weight were associated with efavirenz CL/F. Exposure was significantly lower for EFV400 (geometric mean ratio, GMR; 90% confidence interval, CI: 0.73 (0.68–0.78)) but 97% (EFV400) and 98% (EFV600) of evaluable pVL was <200 copies/mL at 48 weeks (P = 0.802). Four of 20 patients with mid‐dose concentrations <1.0 mg/L had pVL ≥200 copies/mL (EFV400 = 1; EFV600 = 3). Efavirenz exposure was similar between those with and without efavirenz‐related side effects (GMR; 90% CI: 0.95 (0.88–1.02)). HIV suppression was comparable between doses despite significantly lower EFV400 exposure. Comprehensive evaluation of efavirenz pharmacokinetics/pharmacodynamics revealed important limitations in the accepted threshold concentration.