Placental transfer of the novel endothelin-1 receptor antagonist aprocitentan

RATIONALE: The vasoconstrictor endothelin-1 is elevated in preeclampsia, making endothelin receptor antagonists (ERAs) a logical therapeutic strategy. Here we evaluated the placental transfer of the novel ERA aprocitentan, which has recently been approved for hypertension treatment. MATERIALS AND METHODS: Dual-sided placental cotyledon perfusion was used to study transfer of aprocitentan, added maternally at a clinically relevant concentration of 150 ng/mL. Subsequently, these placentas were fetally exposed to endothelin-1. Antipyrine, which freely transfers to the fetal compartment, and fluorescein isothiocyanate [FITC]-dextran, which does not transfer, were used as comparator substances. RESULTS: After 3 h of perfusion, the fetal-to-maternal ratio for total (free + protein-bound) aprocitentan was 0.25 ± 0.04, while for free aprocitentan it was 0.42 ± 0.08. The fetal aprocitentan concentrations were too low to block the contractile effects of endothelin-1 in the fetal compartment, although experiments in isolated chorionic plate arteries confirmed that aprocitentan can block these effects when given at higher concentrations. After perfusion, 50-60% of aprocitentan was recovered in the maternal and fetal fluid compartments. Around 20-30% was present in tissue, as intact aprocitentan or as its hydrolysis product ACT-080803. Since the recovery of maternally applied antipyrine and FITC-dextran was 85-90%, while fetally applied FITC-dextran was fully recovered, the missing 10-15% is likely present in the intervillous space. DISCUSSION: Aprocitentan transfers across the human placental barrier, although its fetal levels following maternal application of 150 ng/mL were insufficient to block endothelin-1. Drug studies in isolated cotyledons should consider the intervillous space when calculating recovery.