Lowered Rilpivirine Exposure During the Third Trimester of Pregnancy in Human Immunodeficiency Virus Type 1-Infected Women

Background. The use of antiretroviral therapy during pregnancy is important for control of maternal human immunodeficiency virus (HIV) disease and the prevention of perinatal HIV transmission. Physiological changes during pregnancy can reduce antiretroviral exposure. We studied the pharmacokinetics of rilpivirine 25 mg once daily in HIV-1-infected women during late pregnancy. Methods. We conducted a nonrandomized, open-label, multicenter, phase 4 study. HIV-infected pregnant women receiving rilpivirine 25 mg once daily were included. Intensive 24-hour pharmacokinetic sampling was performed in the third trimester and at least 2 weeks postpartum. Pharmacokinetic parameters were calculated by noncompartmental analysis. Results. Sixteen subjects were included. Geometric mean ratios of third trimester vs postpartum were 0.55 (90% confidence interval [CI],.46-.66) for the 24-hour area under the concentration- time curve (AUC(0-24h)); 0.65 (90% CI,.55-.76) for the maximum concentration; and 0.51 (90% CI,.41-.63) for the minimum observed concentration (C-min). Four of 16 (25%) subjects had C-min below the target concentration (0.04 mg/L) in the third trimester of pregnancy. No subtherapeutic levels were observed postpartum. No detectable viral loads were observed in this study. All newborns tested negative for HIV. No birth defects were reported. The median (range, n = 5) rilpivirine cord-to-maternal plasma concentration ratio was 0.50 (range,.35-.81). Conclusions. Rilpivirine exposure is substantially lowered during late pregnancy. Despite lower exposure, virologic suppression was maintained and no perinatal transmission was observed. Overall, these results suggest that rilpivirine 25 mg once daily may be an alternative treatment option for HIV-1-infected pregnant women who are virologically suppressed, in settings where therapeutic drug monitoring and/or close viral load monitoring are feasible to detect suboptimal antiretroviral therapy.