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

Mind the Gaps: Pharmacokinetic Research to Advance Pediatric HIV/TB Cotreatment and TB Prevention

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.

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