Interactions of protease inhibitors atazanavir and ritonavir with ABCB1, ABCG2, and ABCC2 transporters: Effect on transplacental disposition in rats.

Atazanavir and ritonavir are preferred protease inhibitors frequently used in combination antiretroviral therapy for prevention of HIV mother-to-child transmission. Although their use is associated with higher risk of congenital anomalies, factors affecting atazanavir and ritonavir placental transfer are not known. This study is the first attempt to evaluate whether the placental drug efflux ATP-binding cassette (ABC) transporters, p-glycoprotein (ABCB1), breast cancer resistance protein (ABCG2), and/or multidrug resistance-associated proteins 2 (ABCC2), affect placental pharmacokinetics of atazanavir or ritonavir. Transport experiments across MDCKII cells expressing respective human ABC carrier showed that atazanavir is a substrate of ABCB1 and dual perfusion studies in a rat placenta confirmed this finding. In conclusion, we suggest that placental ABCB1 might reduce ATV maternal-to-fetal transfer and therefore represent a site for pharmacokinetic drug-drug interactions of ATV. Further studies in human placenta models are necessary to provide additional data closer to clinical environment.