A study of the pharmacokinetics, safety, and efficacy of bictegravir/emtricitabine/tenofovir alafenamide in virologically suppressed pregnant women with HIV.

Objective: The objective of this study was to assess the pharmacokinetics, safety, and efficacy and confirm the dose of once-daily bictegravir/emtricitabine/tenofovir alafenamide (BIC/FTC/TAF; B/F/TAF) during pregnancy.

Design: An open-label, multicenter, single-arm, phase 1b study (NCT03960645) was conducted in 33 virologically suppressed pregnant women with HIV-1.

Methods: Participants received B/F/TAF (50/200/25 mg) from the second or third trimester through ∼16 weeks postpartum. Steady-state maternal plasma pharmacokinetic samples were collected at the second and third trimesters and 6 and 12 weeks postpartum for BIC, FTC, and TAF. Neonates ( n  = 29) were followed from birth to 4-8 weeks with sparse washout pharmacokinetic sampling for BIC and TAF. The proportion of participants with HIV-1 RNA less than 50 copies/ml at delivery (missing = excluded) was evaluated.

Results: Mean areas under the concentration-time curve over the dosing interval (AUC tau ) for BIC, FTC, and TAF were lower during pregnancy versus postpartum but were closer to AUC tau values for nonpregnant adults with HIV reported in other studies. Geometric least-squares mean ratios for BIC, FTC, and TAF AUC tau during pregnancy versus postpartum ranged from 41 to 45%, 64 to 69% and 57 to 78%, respectively. Mean BIC trough concentrations during pregnancy were more than 6.5-fold greater than the protein-adjusted 95% effective concentration. In neonates, the median BIC half-life was 43 h. Virologic suppression was maintained in all adult participants throughout the study, with no virologic failure or treatment-emergent resistance to HIV-1, no discontinuations because of adverse events, and no perinatal transmission.

Conclusion: Exposures to BIC, FTC, and TAF were lower during pregnancy than postpartum. However, mean BIC trough concentrations were maintained at levels indicative of efficacious exposure, and FTC/TAF data were concordant with published literature in this population. Pharmacokinetic and safety data, combined with maintenance of robust virologic suppression, suggest that once-daily B/F/TAF without dose adjustment is appropriate during pregnancy.