Placental transfer of enfuvirtide in the ex vivo human placenta perfusion model

OBJECTIVE: The objective of the study was to determine the placental transfer of the antiretroviral fusion inhibitor, enfuvirtide (Fuzeon). STUDY DESIGN: Human cotyledons were perfused for 90 minutes in an open dual circuit with enfuvirtide, and fetal venous samples were collected every 5 minutes. Three perfusion experiments were validated using antipyrine. RESULTS: Enfuvirtide was not detected in the fetal compartment in any of the 3 experiments. The mean concentration of the drug measured in the maternal compartment was 12,400 ng/mL (range, 6500-16,200 ng/mL), which is 2.5 times the maximum concentration recommended for patients treated with enfuvirtide. CONCLUSION: Even at maternal concentrations twice above therapeutic levels, no placental transfer of enfuvirtide was observed. The high molecular weight of the molecule (4492 kDa) and its ionized state may account for the lack of placental transfer. This result suggests that enfuvirtide could be used in HIV-infected pregnant women without causing fetal exposure.