Dolutegravir Pharmacokinetics Among HIV/TB Coinfected Children Receiving Standard 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.