Dolutegravir Pharmacokinetics Among HIV/TB Coinfected Children Receiving Standard and High-dose Rifampicin

Dolutegravir Pharmacokinetics Among HIV/TB Coinfected Children Receiving Standard and High-dose Rifampicin

Tuberculosis (TB) is the leading cause of death among children with HIV, yet insufficient data are available on the pharmacokinetics of newer HIV/TB cotreatment strategies in children. Current WHO-recommended rifampicin dosages result in low concentrations in most children, and high-dose rifampicin may improve outcomes and shorten treatment duration. Yet the impact of high-dose rifampicin on dolutegravir exposures has not been examined in children. This study aims to evaluate the safety and pharmacokinetics of dolutegravir twice daily among HIV/TB coinfected children receiving standard-dose and high-dose rifampicin.

This study is a prospective, single-arm, open-label, intensive and sparse pharmacokinetic (PK) and safety study to evaluate steady-state dolutegravir (DTG) concentrations among 20 HIV/TB coinfected children 4 weeks to <6 years of age requiring concurrent TB treatment. Ten patients will be recruited into each of two age cohorts: 4 weeks to <2 years and ≥2 years to <6 years. Children will be recruited from two large pediatric HIV clinics in Nigeria. Children in this study will receive HIV/TB cotreatment that is considered standard of care consisting of DTG twice daily during rifampicin (RIF)-containing TB treatment. For this portion of the study, the primary intervention is additional blood sampling for drug concentration determination and biomarker assessment. Additionally, during a two week period (study weeks 20-21), the RIF dose will be increased from standard-dose to high-dose RIF, during which two-way PK and toxicity monitoring will occur. Clinical and laboratory monitoring for toxicity during HIV/TB cotreatment is consistent with routine care. PK sampling for drug concentration determination will occur at three time points during the 48-week study. Specifically, PK sampling will occur at week-20 to evaluate DTG twice daily during standard-dose RIF, week-22 to evaluate DTG twice daily during high-dose RIF, and at week-30 to evaluate DTG once daily after TB treatment is complete. Additionally, the endogenous biomarker of CYP3A4 activity, 4-beta-hydroxycholesterol to cholesterol ratio, will be evaluated to advance understanding of underlying mechanisms of drug action. Blood sampling to quantify this biomarker will occur at either 4 (among ART-experienced children) or 5 (ART-naive) time points during the 48-week study.

This is a single arm study: all patients are started on HIV/TB cotreatment considered standard of care and then for two weeks (study weeks 20-21) high-dose rifampicin is given during which safety and pharmacokinetics are examined.

Patients will receive standard TB and HIV treatment, however, for two weeks (study weeks 20-21) the dose of rifampicin will be increased from standard-dose to high-dose to assess pharmacokinetics and safety

Dolutegravir area under the concentration time curve (AUC) will be compared to therapeutic ranges established in the adult and pediatric literature

Dolutegravir AUC will be compared against therapeutic ranges established in the literature and during standard-dose rifampicin

Rifampicin Cmax will be determined during high-dose rifampicin and compared to that observed during standard-dose rifampicin

Laboratory and clinical toxicities are monitored at 8 time points throughout the study and the proportion of children experiencing severe adverse events will be determined

Inclusion Criteria: ART-naïve or ART-experienced HIV-infected children between 4 weeks and <6 years of age Active TB diagnosis Weight of at least 3 kilograms Consent of the parent or legal guardian Exclusion Criteria: Baseline labs with evidence of ≥grade 3 abnormalities: ALT, total bilirubin, absolute neutrophil count (ANC), platelets, or creatinine Suspected TB meningitis or presenting with acute respiratory distress or decompensation Receipt of a medication that has drug-drug interactions with dolutegravir or rifampicin