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Rationale: Observational studies suggest that high-dose isoniazid may be efficacious in treating multidrug-resistant tuberculosis. However, its activity against Mycobacterium tuberculosis (M.tb) with katG mutations (which typically confer high-level resistance) is not established. Objectives: To characterize the early bactericidal activity (EBA) of high-dose isoniazid in patients with tuberculosis caused by katG-mutated M.tb. Methods: A5312 was a phase IIA 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 pharmacokinetic 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 modeling. Measurements and Main Results: Of 80 treated participants, 21 had katG-mutated M.tb. Isoniazid pharmacokinetics were best described by a two-compartment model with an effect of NAT2 acetylator phenotype on clearance. Model-derived maximum concentration and area under the concentration–time curve 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 maximum efficacy relationship. Isoniazid potency against katG-mutated M.tb was approximately 10-fold lower than in inhA-mutated M.tb. The highest dose of 20 mg/kg did not demonstrate measurable EBA, except against 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 registered with (NCT01936831). [ABSTRACT FROM AUTHOR]

Rationale: Pretomanid is a new nitroimidazole with proven treatment-shortening efficacy in drug-resistant tuberculosis. Pretomanid-rifamycin-pyrazinamide combinations are potent in mice but have not been tested clinically. Rifampicin, but not rifabutin, reduces pretomanid exposures.Objective: Evaluate the safety and efficacy of pretomanid-rifamycin-pyrazinamide containing regimens among participants with drug-sensitive pulmonary tuberculosis.Methods: Phase 2 twelve-week open-label randomized trial of isoniazid, pyrazinamide, plus (a) pretomanid and rifampicin (Arm 1); (b) pretomanid and rifabutin (Arm 2) or (c) rifampicin and ethambutol (standard of care, Arm 3). Safety labs and sputum cultures were collected at Weeks 1, 2, 3, 4, 6, 8, 10, 12. Time to culture conversion on liquid media was the primary outcome.Results: Among 157 participants, 125 (80%) had cavitary disease. Median time to liquid culture negativity in the modified intention to treat (mITT) population (n=150) was 41 (Arm 1), 28 (Arm 2), and 55 (Arm 3) days (p=0.01)(adjusted hazard ratios of 1.41 (0.93-2.12, p=0.10), Arm 1 vs. Arm 3) and 1.89 (1.24-2.87, p=0.003, Arm 2 vs. Arm 3)). Eight-week liquid culture conversion was 79%, 89%, and 69%, respectively. Grade >3 adverse events occurred in 3/56 (5%), 5/53 (9%), and 2/56 (4%) of participants. Six participants were withdrawn owing to elevated transaminases (5 in Arm 2, 1 in Arm 1).There were 3 serious adverse events (Arm 2) and no deaths.Conclusions: Pretomanid enhanced the microbiologic activity of rifamycin-pyrazinamide containing regimens. Efficacy and hepatic adverse events appeared highest with the pretomanid and rifabutin-containing regimen. Whether this is due to higher pretomanid concentrations merits exploration. Clinical trial registration available at www.Clinicaltrials: gov, ID: NCT02256696. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

An elderly man with refractory Mycobacterium abscessus lung disease previously developed anti-phage neutralizing antibodies while receiving intravenous phage therapy. Subsequent phage nebulization resulted in transient weight gain, decreased C-reactive protein, and reduced Mycobacterium burden. Weak sputum neutralization may have limited the outcomes, but phage resistance was not a contributing factor. [ABSTRACT FROM AUTHOR]

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). [ABSTRACT FROM AUTHOR]

New modalities of Pre-exposure Prophylaxis (PrEP) such as long-acting injectable PrEP (LAI-PrEP) promise increased prevention of HIV transmission; however, similar biomedical interventions have not been met with universal adoption by healthcare providers or populations most affected by HIV. This qualitative study explores healthcare provider considerations for the rollout of LAI-PrEP. Eleven key-informant in-depth interviews were conducted with clinicians who prescribe daily oral PrEP. Participants reviewed a currently proposed LAI regimen and were asked to reflect on its implications for their clinical practice. Interviews were transcribed verbatim and thematically coded, with results organized using the Consolidated Framework for Implementation Research (CFIR). All participants expressed interest in prescribing LAI-PrEP and anticipated that at least some patients would be interested. Participants identified characteristics of the intervention, inner intervention setting, and outer intervention setting that will be influential in bringing LAI-PrEP to scale. Clinicians in the South have unique insights into the challenges of and opportunities for successful rollout of future PrEP regimens. Bringing these insights into a CFIR framework highlights the nuances surrounding LAI-PrEP, including structural concerns such as cost barriers and access to in-person healthcare services. It is critical to address these challenges to ensure successful implementation of new PrEP formulations. [ABSTRACT FROM AUTHOR]

Background There is currently no single treatment that mitigates all harms caused by severe acute respiratory syndrome coronavirus 2 infection. Tocilizumab, an interleukin-6 antagonist, may have a role as an adjunctive immune-modulating therapy. Methods This was an observational retrospective study of hospitalized adult patients with confirmed coronavirus disease 2019 (COVID-19). The intervention group comprised patients who received tocilizumab; the comparator arm was drawn from patients who did not receive tocilizumab. The primary outcome was all-cause mortality censored at 28 days; secondary outcomes were all-cause mortality at discharge, time to clinical improvement, and rates of secondary infections. Marginal structural Cox models via inverse probability treatment weights were applied to estimate the effect of tocilizumab. A time-dependent propensity score–matching method was used to generate a 1:1 match for tocilizumab recipients; infectious diseases experts then manually reviewed these matched charts to identify secondary infections. Results This analysis included 90 tocilizumab recipients and 1669 controls. Under the marginal structural Cox model, tocilizumab was associated with a 62% reduced hazard of death (adjusted hazard ratio [aHR], 0.38; 95% CI, 0.21 to 0.70) and no change in time to clinical improvement (aHR, 1.13; 95% CI, 0.68 to 1.87). The 1:1 matched data set also showed a lower mortality rate (27.8% vs 34.4%) and reduced hazards of death (aHR, 0.47; 95% CI, 0.25 to 0.88). Elevated inflammatory markers were associated with reduced hazards of death among tocilizumab recipients compared with controls. Secondary infection rates were similar between the 2 groups. Conclusions Tocilizumab may provide benefit in a subgroup of patients hospitalized with COVID-19 who have elevated biomarkers of hyperinflammation, without increasing the risk of secondary infection. [ABSTRACT FROM AUTHOR]

Purpose of Review: Despite broad uptake of antiretroviral therapy (ART), tuberculosis (TB) incidence and mortality among people with HIV remain unacceptably high. Short-course regimens for TB, incorporating both novel and established drugs, offer the potential to enhance adherence and completion rates, thereby reducing the global TB burden. This review will outline short-course regimens for TB among patients with HIV. Recent Findings: After many years without new agents, there is now active testing of many novel drugs to treat TB, both for latent infection and active disease. Though not all studies have included patients with HIV, many have, and there are ongoing trials to address key implementation challenges such as potent drug-drug interactions with ART. Summary: The goal of short-course regimens for TB is to enhance treatment completion without compromising efficacy. Particularly among patients with HIV, studying these shortened regimens and integrating them into clinical care are of urgent importance. There are now multiple short-course regimens for latent infection and active disease that are safe and effective among patients with HIV. [ABSTRACT FROM AUTHOR]

Rationale: High-dose isoniazid is recommended in short-course regimens for multidrug-resistant tuberculosis (TB). The optimal dose of isoniazid and its individual contribution to efficacy against TB strains with inhA or katG mutations are unknown.Objectives: To define the optimal dose of isoniazid for patients with isoniazid-resistant TB mediated by inhA mutations.Methods: AIDS Clinical Trials Group A5312 is a phase 2A, open-label trial in which individuals with smear-positive pulmonary TB with isoniazid resistance mediated by an inhA mutation were randomized to receive isoniazid 5, 10, or 15 mg/kg daily for 7 days (inhA group), and control subjects with drug-sensitive TB received the standard dose (5 mg/kg/d). Overnight sputum cultures were collected daily. The 7-day early bactericidal activity (EBA) of isoniazid was estimated as the average daily change in log10 cfu on solid media (EBAcfu0-7) or as time to positivity (TTP) in liquid media in hours (EBATTP0-7) using nonlinear mixed-effects models.Measurements and Main Results: Fifty-nine participants (88% with cavitary disease, 20% HIV-positive, 16 with isoniazid-sensitive TB, and 43 with isoniazid-monoresistant or multidrug-resistant TB) were enrolled at one site in South Africa. The mean EBAcfu0-7 at doses of 5, 10, and 15 mg/kg in the inhA group was 0.07, 0.17, and 0.22 log10 cfu/ml/d, respectively, and 0.16 log10 cfu/ml/d in control subjects. EBATTP0-7 patterns were similar. There were no drug-related grade ≥3 adverse events.Conclusions: Isoniazid 10-15 mg/kg daily had activity against TB strains with inhA mutations similar to that of 5 mg/kg against drug-sensitive strains. The activity of high-dose isoniazid against strains with katG mutations will be explored next.Clinical trial registered with www.clinicaltrials.gov (NCT01936831). [ABSTRACT FROM AUTHOR]