Pharmacokinetics of Atazanavir Boosted With Cobicistat in Pregnant and Postpartum Women With HIV

Background: This study evaluated atazanavir and cobicistat pharmacokinetics during pregnancy compared with postpartum and in infant washout samples. Setting: A nonrandomized, open-label, parallel-group, multicenter prospective study of atazanavir and cobicistat pharmacokinetics in pregnant women with HIV and their children. Methods: Intensive steady-state 24-hour pharmacokinetic profiles were performed after administration of 300 mg of atazanavir and 150 mg of cobicistat orally in fixed-dose combination once daily during the second trimester, third trimester, and postpartum. Infant washout samples were collected after birth. Atazanavir and cobicistat were measured in plasma by validated high-performance liquid chromatography-ultraviolet and liquid chromatography-tandem mass spectrometry assays, respectively. A 2-tailed Wilcoxon signed-rank test (alpha = 0.10) was used for paired within-participant comparisons. Results: A total of 11 pregnant women enrolled in the study. Compared with paired postpartum data, atazanavir AUC(0)(-24) was 26% lower in the second trimester [n = 5, P = 0.1875, geometric mean of ratio (GMR) = 0.739, 90% CI: 0.527 to 1.035] and 54% lower in the third trimester (n = 6, GMR = 0.459, P = 0.1563, 90% CI: 0.190 to 1.109), whereas cobicistat AUC(0-24) was 35% lower in the second trimester (n = 5, P = 0.0625, GMR = 0.650, 90% CI: 0.493 to 0.858) and 52% lower in the third trimester (n = 7, P = 0.0156, GMR = 0.480, 90% CI: 0.299 to 0.772). The median (interquartile range) 24-hour atazanavir trough concentration was 0.21 mu g/mL (0.16-0.28) in the second trimester, 0.21 mu g/mL (0.11-0.56) in the third trimester, and 0.61 mu g/mL (0.42-1.03) in postpartum. Placental transfer of atazanavir and cobicistat was limited. Conclusions: Standard atazanavir/cobicistat dosing during pregnancy results in lower exposure which may increase the risk of virologic failure and perinatal transmission.