High-Dose Isoniazid Lacks EARLY Bactericidal Activity Against Isoniazid-resistant Tuberculosis Mediated by katG Mutations: A Randomized, Phase 2 Clinical Trial.

RATIONALE: Observational studies suggest that high-dose isoniazid may be efficacious in treating multidrug-resistant tuberculosis (MDR-TB). However, its activity against Mycobacterium tuberculosis (M.tb) with katG mutations (which typically confer high-level resistance) is not established. OBJECTIVE: To characterize early bactericidal activity (EBA) of high-dose isoniazid in patients with tuberculosis caused by katG-mutated M.tb. METHODS: A5312 was a Phase 2A randomized, open-label trial. Participants with tuberculosis caused by katG-mutated M.tb were randomized to receive 15 or 20 mg/kg isoniazid daily for 7 days. Daily sputum samples were collected for quantitative culture. Intensive PK sampling was performed on day 6. Data were pooled across all A5312 participants for analysis (drug-sensitive, inhA-mutated, and katG-mutated M.tb). EBA was determined using nonlinear mixed-effects modelling. RESULTS: Of 80 treated participants, 21 had katG-mutated M.tb. Isoniazid PK was best described by a two-compartment model with an effect of NAT2 acetylator phenotype on clearance. Model-derived Cmax and AUC in the 15 and 20 mg/kg groups were 15.0 and 22.1 mg/L and 57.6 and 76.8 mg∙h/L, respectively. Isoniazid bacterial kill was described using an effect compartment and a sigmoidal Emax relationship. Isoniazid potency against katG-mutated M.tb was approximately 10-fold lower than against inhA-mutated M.tb. The highest dose (20 mg/kg) did not demonstrate measurable EBA, except in a subset of slow NAT2 acetylators (who experienced the highest concentrations). There were no grade 3 or higher drug-related adverse events. CONCLUSIONS: This study found negligible bactericidal activity of high-dose isoniazid (15-20 mg/kg) in the majority of participants with tuberculosis caused by katG-mutated M.tb. Clinical trial registration available at www. CLINICALTRIALS: gov, ID: NCT01936831.

Pharmacokinetics and safety of twice-daily ritonavir-boosted atazanavir with rifampicin.

BACKGROUND: Critical drug-drug interactions (DDI) and hepatotoxicity complicate concurrent use of rifampicin and protease inhibitors. We investigated whether dose escalation of atazanavir/ritonavir could safely overcome the DDI with rifampicin. METHODS: DERIVE (NCT04121195, EDCTP) was a dose-escalation trial in people with HIV on atazanavir/ritonavir-based ART in Uganda. Four intensive pharmacokinetic (PK) visits were performed: PK1 300/100 mg OD (baseline); PK2 300/100 mg OD with rifampicin 600 mg; PK3 300/100 mg BID with rifampicin 600 mg OD; PK4 300/100 mg BID with rifampicin 1200 mg OD. Dolutegravir 50 mg BID throughout the study period ensured participants remained protected from subtherapeutic atazanavir concentrations. The data was interpreted with noncompartmental analysis. The target minimum concentration was atazanavir's protein-adjusted IC90 (PA-IC90), 0.014 mg/L. RESULTS: We enrolled 26 participants (23 female) with median (range) age 44 (28-61) years and weight 67 (50-75) kg. Compared with PK1, atazanavir Ctau, and AUC were significantly reduced at PK2 by 96% and 85%, respectively. The escalation to BID dosing (PK3) reduced this difference in Ctau, and AUC24 to 18% lower and 8% higher, respectively. Comparable exposures were maintained with double doses of rifampicin. Lowest Ctau during PK1, PK3, and PK4 were 12.7-, 4.8-, and 8.6-fold higher than PA-IC90, respectively, while 65% of PK2 Ctau were below the limit of quantification (0.03 mg/L), hence likely below PA-IC90. No participant developed significant elevation of liver enzymes, reported an SAE, or experienced rebound viraemia. CONCLUSIONS: Twice daily atazanavir/ritonavir during rifampicin co-administration was well-tolerated and achieved plasma concentrations above the target.

Unexpectedly low drug exposures among Ugandan patients with TB and HIV receiving high-dose rifampicin.

We characterized the pharmacokinetics of standard- and high-dose rifampicin in Ugandan adults with tuberculosis and HIV taking dolutegravir- or efavirenz-based antiretroviral therapy. A liver model with saturable hepatic extraction adequately described the data, and the increase in exposure between high and standard doses was 4.7-fold. This was lower than what previous reports of dose-exposure nonlinearity would predict and was ascribed to 38% lower bioavailability of the rifampicin-only top-up formulation compared to the fixed-dose combination.

Dolutegravir pharmacokinetics in Ugandan patients with TB and HIV receiving standard- versus high-dose rifampicin.

Higher rifampicin doses may improve tuberculosis treatment outcomes. This could however exacerbate the existing drug interaction with dolutegravir. Moreover, the metabolism of dolutegravir may also be affected by polymorphism of UGT1A1, a gene that codes for uridine diphosphate glucuronosyltransferase. We used population pharmacokinetic modeling to compare the pharmacokinetics of dolutegravir when coadministered with standard- versus high-dose rifampicin in adults with tuberculosis and HIV, and investigated the effect of genetic polymorphisms. Data from the SAEFRIF trial, where participants were randomized to receive first-line tuberculosis treatment with either standard- 10 mg/kg or high-dose 35 mg/kg rifampicin alongside antiretroviral therapy, were used. The dolutegravir model was developed with 211 plasma concentrations from 44 participants. The median (interquartile range) rifampicin area under the curve (AUC) in the standard- and high-dose arms were 32.3 (28.7-36.7) and 153 (138-175) mg·h/L, respectively. A one-compartment model with first-order elimination and absorption through transit compartments best described dolutegravir pharmacokinetics. For a typical 56 kg participant, we estimated a clearance, absorption rate constant, and volume of distribution of 1.87 L/h, 1.42 h-1, and 12.4 L, respectively. Each 10 mg·h/L increase in the AUC of coadministered rifampicin from 32.3 mg·h/L led to a 2.3 (3.1-1.4) % decrease in dolutegravir bioavailability. Genetic polymorphism of UGT1A1 did not significantly affect dolutegravir pharmacokinetics. Simulations of trough dolutegravir concentrations show that the 50 mg twice-daily regimen attains both the primary and secondary therapeutic targets of 0.064 and 0.3 mg/L, respectively, regardless of the dose of coadministered rifampicin, unlike the once-daily regimen.

Decreased Dolutegravir and Efavirenz Concentrations With Preserved Virological Suppression in Patients With Tuberculosis and Human Immunodeficiency Virus Receiving High-Dose Rifampicin.

BACKGROUND: Higher doses of rifampicin may improve treatment outcomes and reduce the duration of tuberculosis (TB) therapy. However, drug-drug interactions with antiretroviral therapy (ART) and safety in people with human immunodeficiency virus (HIV) have not been evaluated. METHODS: This was a randomized, open-label trial where newly diagnosed TB patients were randomized to higher (35 mg/kg) or standard (10 mg/kg) daily-dose rifampicin. ART treatment-naive patients were randomized to dolutegravir- or efavirenz-based ART. At week 6, trough dolutegravir or mid-dose efavirenz plasma concentrations were assayed. HIV viral load was measured at week 24. RESULTS: Among 128 patients randomized, the median CD4 count was 191 cells/mm3. The geometric mean ratio (GMR) for trough dolutegravir concentrations on higher- vs standard-dose rifampicin was 0.57 (95% confidence interval [CI], .34-.97; P = .039) and the GMR for mid-dose efavirenz was 0.63 (95% CI, .38-1.07; P = .083). There was no significant difference in attainment of targets for dolutegravir trough or efavirenz mid-dose concentrations between rifampicin doses. The incidence of HIV treatment failure at week 24 was similar between rifampicin doses (14.9% vs 14.0%, P = .901), as was the incidence of drug-related grade 3-4 adverse events (9.8% vs 6%). At week 8, fewer patients remained sputum culture positive on higher-dose rifampicin (18.6% vs 37.0%, P = .063). CONCLUSIONS: Compared with standard-dose rifampicin, high-dose rifampicin reduced dolutegravir and efavirenz exposures, but HIV suppression was similar across treatment arms. Higher-dose rifampicin was well tolerated among people with HIV and associated with a trend toward faster sputum culture conversion. CLINICAL TRIALS REGISTRATION: NCT03982277.

Pharmacokinetics of standard versus high-dose isoniazid for treatment of multidrug-resistant tuberculosis.

BACKGROUND: The WHO-endorsed shorter-course regimen for MDR-TB includes high-dose isoniazid. The pharmacokinetics of high-dose isoniazid within MDR-TB regimens has not been well described. OBJECTIVES: To characterize isoniazid pharmacokinetics at 5-15 mg/kg as monotherapy or as part of the MDR-TB treatment regimen. METHODS: We used non-linear mixed-effects modelling to evaluate the combined data from INHindsight, a 7 day early bactericidal activity study with isoniazid monotherapy, and PODRtb, an observational study of patients on MDR-TB treatment including terizidone, pyrazinamide, moxifloxacin, kanamycin, ethionamide and/or isoniazid. RESULTS: A total of 58 and 103 participants from the INHindsight and PODRtb studies, respectively, were included in the analysis. A two-compartment model with hepatic elimination best described the data. N-acetyltransferase 2 (NAT2) genotype caused multi-modal clearance, and saturable first-pass was observed beyond 10 mg/kg dosing. Saturable isoniazid kinetics predicted an increased exposure of approximately 50% beyond linearity at 20 mg/kg dosing. Participants treated with the MDR-TB regimen had a 65.6% lower AUC compared with participants on monotherapy. Ethionamide co-administration was associated with a 29% increase in isoniazid AUC. CONCLUSIONS: Markedly lower isoniazid exposures were observed in participants on combination MDR-TB treatment compared with monotherapy. Isoniazid displays saturable kinetics at doses >10 mg/kg. The safety implications of these phenomena remain unclear.

Bedaquiline exposure in pregnancy and breastfeeding in women with rifampicin-resistant tuberculosis.

AIMS: We aimed to explore the effect of pregnancy on bedaquiline pharmacokinetics (PK) and describe bedaquiline exposure in the breast milk of mothers treated for rifampicin-resistant tuberculosis (TB), where there are no human data available. METHODS: We performed a longitudinal PK study in pregnant women treated for rifampicin-resistant TB to explore the effect of pregnancy on bedaquiline exposure. Pharmacokinetic sampling was performed at 4 time-points over 6 hours in the third trimester, and again at approximately 6 weeks postpartum. We obtained serial breast milk samples from breastfeeding mothers, and a single plasma sample taken from breastfed and nonbreastfed infants to assess bedaquiline exposure. We used liquid chromatography-tandem mass spectrometry to perform the breast milk and plasma bedaquiline assays, and population PK modelling to interpret the bedaquiline concentrations. RESULTS: We recruited 13 women, 6 of whom completed the ante- and postpartum PK sampling. All participants were HIV-positive on antiretroviral therapy. We observed lower ante- and postpartum bedaquiline exposures than reported in nonpregnant controls. Bedaquiline concentrations in breast milk were higher than maternal plasma (milk to maternal plasma ratio: 14:1). A single random plasma bedaquiline and M2 concentration was available in 4 infants (median age: 6.5 wk): concentrations in the 1 breastfed infant were similar to maternal plasma concentrations; concentrations in the 3 nonbreastfed infants were detectable but lower than maternal plasma concentrations. CONCLUSION: We report low exposure of bedaquiline in pregnant women treated for rifampicin-resistant TB. Bedaquiline significantly accumulates in breast milk; breastfed infants receive mg/kg doses of bedaquiline equivalent to maternal doses.

Population Pharmacokinetics of Antimalarial Naphthoquine in Combination with Artemisinin in Tanzanian Children and Adults: Dose Optimization.

The combination antimalarial therapy of artemisinin-naphthoquine (ART-NQ) was developed as a single-dose therapy, aiming to improve adherence relative to the multiday schedules of other artemisinin combination therapies. The pharmacokinetics of ART-NQ has not been well characterized, especially in children. A pharmacokinetic study was conducted in adults and children over 5 years of age (6 to 10, 11 to 17, and ≥18 years of age) with uncomplicated malaria in Tanzania. The median weights for the three age groups were 20, 37.5, and 55 kg, respectively. Twenty-nine patients received single doses of 20 mg/kg of body weight for artemisinin and 8 mg/kg for naphthoquine, and plasma drug concentrations were assessed at 13 time points over 42 days from treatment. We used nonlinear mixed-effects modeling to interpret the data, and allometric scaling was employed to adjust for the effect of body size. The pharmacokinetics of artemisinin was best described by one-compartment model and that of naphthoquine by a two-compartment disposition model. Clearance values for a typical patient (55-kg body weight and 44.3-kg fat-free mass) were estimated as 66.7 L/h (95% confidence interval [CI], 57.3 to 78.5 L/h) for artemisinin and 44.2 L/h (95% CI, 37.9 to 50.6 L/h) for naphthoquine. Nevertheless, we show via simulation that patients weighing ≥70 kg achieve on average a 30% lower day 7 concentration compared to a 48-kg reference patient at the doses tested, suggesting dose increases may be warranted to ensure adequate exposure. (This study has been registered at ClinicalTrials.gov under identifier NCT01930331.).

A Semimechanistic Model of the Bactericidal Activity of High-Dose Isoniazid against Multidrug-Resistant Tuberculosis: Results from a Randomized Clinical Trial.

Rationale: There is accumulating evidence that higher-than-standard doses of isoniazid are effective against low-to-intermediate-level isoniazid-resistant strains of Mycobacterium tuberculosis, but the optimal dose remains unknown. Objectives: To characterize the association between isoniazid pharmacokinetics (standard or high dose) and early bactericidal activity against M. tuberculosis (drug sensitive and inhA mutated) and N-acetyltransferase 2 status. Methods: ACTG (AIDS Clinical Trial Group) A5312/INHindsight is a 7-day early bactericidal activity study with isoniazid at a normal dose (5 mg/kg) for patients with drug-sensitive bacteria and 5, 10, and 15 mg/kg doses for patients with inhA mutants. Participants with pulmonary tuberculosis received daily isoniazid monotherapy and collected sputum daily. Colony-forming units (cfu) on solid culture and time to positivity in liquid culture were jointly analyzed using nonlinear mixed-effects modeling. Measurements and Main Results: Fifty-nine adults were included in this analysis. A decline in sputum cfu was described by a one-compartment model, whereas an exponential bacterial growth model was used to interpret time-to-positivity data. The model found that bacterial kill is modulated by isoniazid concentration using an effect compartment and a sigmoidal Emax relationship (a model linking the drug concentration to the observed effect). The model predicted lower potency but similar maximum kill of isoniazid against inhA-mutated compared with drug-sensitive isolates. Based on simulations from the pharmacokinetics-pharmacodynamics model, to achieve a drop in bacterial load comparable to 5 mg/kg against drug-sensitive tuberculosis, 10- and 15-mg/kg doses are necessary against inhA-mutated isolates in slow and intermediate N-acetyltransferase 2 acetylators, respectively. Fast acetylators underperformed even at 15 mg/kg. Conclusions: Dosing of isoniazid based on N-acetyltransferase 2 acetylator status may help patients attain effective exposures against inhA-mutated isolates. Clinical trial registered with www.clinicaltrials.gov (NCT01936831).

Pharmacokinetics and Target Attainment of SQ109 in Plasma and Human-Like Tuberculosis Lesions in Rabbits.

SQ109 is a novel well-tolerated drug candidate in clinical development for the treatment of drug-resistant tuberculosis (TB). It is the only inhibitor of the MmpL3 mycolic acid transporter in clinical development. No SQ109-resistant mutant has been directly isolated thus far in vitro, in mice, or in patients, which is tentatively attributed to its multiple targets. It is considered a potential replacement for poorly tolerated components of multidrug-resistant TB regimens. To prioritize SQ109-containing combinations with the best potential for cure and treatment shortening, one must understand its contribution against different bacterial populations in pulmonary lesions. Here, we have characterized the pharmacokinetics of SQ109 in the rabbit model of active TB and its penetration at the sites of disease-lung tissue, cellular and necrotic lesions, and caseum. A two-compartment model with first-order absorption and elimination described the plasma pharmacokinetics. At the human-equivalent dose, parameter estimates fell within the ranges published for preclinical species. Tissue concentrations were modeled using an "effect" compartment, showing high accumulation in lung and cellular lesion areas with penetration coefficients in excess of 1,000 and lower passive diffusion in caseum after 7 daily doses. These results, together with the hydrophobic nature and high nonspecific caseum binding of SQ109, suggest that multiweek dosing would be required to reach steady state in caseum and poorly vascularized compartments, similar to bedaquiline. Linking lesion pharmacokinetics to SQ109 potency in assays against replicating, nonreplicating, and intracellular M. tuberculosis showed SQ109 concentrations markedly above pharmacokinetic-pharmacodynamic targets in lung and cellular lesions throughout the dosing interval.

Pharmacokinetics and Drug-Drug Interactions of Isoniazid and Efavirenz in Pregnant Women Living With HIV in High TB Incidence Settings: Importance of Genotyping.

The World Health Organization guidelines recommend that individuals living with HIV receive ≥ 6 months of isoniazid preventive therapy, including pregnant women. Yet, plasma isoniazid exposure during pregnancy, in the antiretroviral therapy era, has not been well-described. We investigated pregnancy-induced and pharmacogenetic-associated pharmacokinetic changes and drug-drug interactions between isoniazid and efavirenz in pregnant women. Eight hundred forty-seven women received isoniazid for 28 weeks, either during pregnancy or at 12 weeks postpartum, and 786 women received efavirenz. After adjusting for NAT2 and CYP2B6 genotype and weight, pregnancy increased isoniazid and efavirenz clearance by 26% and 15%, respectively. Isoniazid decreased efavirenz clearance by 7% in CYP2B6 normal metabolizers and 13% in slow and intermediate metabolizers. Overall, both isoniazid and efavirenz exposures were reduced during pregnancy, but the main determinants of drug concentration were NAT2 and CYP2B6 genotypes, which resulted in a five-fold difference for both drugs between rapid and slow metabolizers.

Effects of Pregnancy and Isoniazid Preventive Therapy on Mycobacterium tuberculosis Interferon Gamma Response Assays in Women With HIV.

BACKGROUND: Pregnancy is accompanied by immune suppression. We hypothesized that Mycobacterium tuberculosis-specific inflammatory responses used to identify latent tuberculosis infection (LTBI) lose positivity during pregnancy. We also hypothesized that isoniazid preventive therapy (IPT) may revert LTBI diagnoses because of its sterilizing activity. METHODS: 944 women with human immunodeficiency virus infection (HIV) participating in a randomized, double-blind, placebo-controlled study comparing 28 weeks of IPT antepartum versus postpartum, were tested by QuantiFERON-gold-in-tube (QGIT) antepartum and by QGIT and tuberculin skin test (TST) at delivery and postpartum. Serial QGIT positivity was assessed by logistic regression using generalized estimating equations. RESULTS: From entry to delivery, 68 (24%) of 284 QGIT-positive women reverted to QGIT-negative or indeterminate. Of these, 42 (62%) recovered QGIT positivity postpartum. The loss of QGIT positivity during pregnancy was explained by decreased interferon gamma (IFNγ) production in response to TB antigen and/or mitogen. At delivery, LTBI was identified by QGIT in 205 women and by TST in 113 women. Corresponding numbers postpartum were 229 and 122 women. QGIT and TST kappa agreement coefficients were 0.4 and 0.5, respectively. Among QGIT-positive women antepartum or at delivery, 34 (12%) reverted to QGIT-negative after IPT. There were no differences between women who initiated IPT antepartum or postpartum. CONCLUSIONS: Decreased IFNγ responses in pregnancy reduced QGIT positivity, suggesting that this test cannot reliably rule out LTBI during pregnancy. TST was less affected by pregnancy, but had lower positivity compared to QGIT at all time points. IPT was associated with loss of QGIT positivity, the potential clinical consequences of which need to be investigated.

The Effect of Frequent Exposure to P. falciparum, HIV-Infection and Other Co-Morbidities on Development of Severe Malaria in Malawian Adults.

AIM: Plasmodium falciparum malaria predominantly affects children residing in endemic areas. However, recently a significant number of Malawian adults, who otherwise should have attained some malaria-specific immunity, have been observed to succumb to either uncomplicated malaria (UM) or severe malaria (SM). In addition, it is still unknown whether HIV is a contributing factor to SM in Malawian non-pregnant adults. We conducted this study to determine clinical and demographic features that characterize Malawian adults presenting with UM or SM. METHODS: Study participants were recruited when they presented at Queen Elizabeth Central Hospital (QECH), Blantyre, Malawi with UM or SM and had their demographic details recorded after consenting to participate in the study. Malaria infection was confirmed by Malaria Rapid Diagnostic Test (MRDT) and malaria slide microscopy. A venous blood sample was collected before treatment for various analyses. RESULTS: Both HIV-infected and HIV-uninfected participants were at risk of presenting with either UM or SM although there were more (37%) SM cases among those who were HIV-infected compared to those who were HIV-uninfected (28%) but the difference was not significant but similar numbers of UM cases (61% for HIV-uninfected and 60% for HIV-infected). Previous visit to areas of high malaria transmission was not associated with presenting with either UM or SM. HIV/malaria co-infected participants were more likely to be found with a positive blood culture result (Diphtheriods, Stenotophomonas maltophilia, Salmonella typhimurium and Staphylococcus aureus) and were at a higher risk of dying compared to HIV-uninfected malaria patients. CONCLUSION: Although HIV-infection was associated with high mortality in those co-infected with HIV and malaria, recurrent malaria episodes and having other diseases co-existing with malaria infection were the main factors associated with the development of SM in this study cohort. Further studies need to be done to determine how the host immunity is affected in those co-infected with HIV and malaria.

HIV infection has a profound effect on hematological factors but not on electrolyte profile of Malawian adults presenting with uncomplicated malaria and severe malaria.

AIM: Although malaria and HIV infections independently affect the electrolyte and hematologic profiles, little is known of how these profiles are affected in individuals coinfected with malaria and HIV. We therefore conducted this study to investigate the electrolyte and hematologic profiles of Malawian adults presenting with either uncomplicated malaria (UM), severe malaria (SM), and those presenting with HIV and UM or HIV and SM. METHODS: Study participants were recruited at Queen Elizabeth Central Hospital, and malaria infection was confirmed by rapid diagnostic test and malaria slides, and full blood count, HIV, and wet chemistries were analyzed. RESULTS: Sodium, potassium, calcium, and chloride levels of all 4 study groups were similar to those of healthy controls. Both HIV-infected groups (UM and SM) had lower red blood cell counts and lower hemoglobin concentration than the reference range. Platelet counts were lower in both HIV-uninfected SM cases (64×109/L) and in the HIV-infected SM cases (66×109/L) compared to the reference range (115-290×109/L). HIV- UM cases had higher proportion and absolute counts of neutrophils and white blood cell counts compared to the HIV+ UM cases. CONCLUSION: HIV infection did not affect the electrolyte profile of Malawian adults presenting with UM or SM but had an effect on red blood cells, Hb concentration, neutrophils, and platelet counts.