Background: Congenital diaphragmatic hernia is an orphan disease with high neonatal mortality and significant morbidity. An important cause for this is pulmonary hypertension, for which no effective postnatal therapy is available to date. An innovative strategy aiming at treating or preventing pulmonary hypertension more effectively is urgently needed. Prenatal sildenafil administration to expectant mothers prevented fetal and neonatal vascular changes leading to pulmonary hypertension in several animal models, and is, therefore, a promising approach. Before transferring this antenatal medical approach to the clinic, more information is needed on transplacental transfer and safety of sildenafil in humans. Methods: This is a randomized, investigator-blinded, double-armed, parallel-group, phase I/IIb study with as a primary objective to measure the in-vivo transplacental transfer of sildenafil in women in the second and early third trimester of pregnancy (sub-study 1; weeks: 20.0-32.6) and at term (sub-study 2; weeks: 36.6-40). Participants will be randomized to two different sildenafil doses: 25 or 75 mg. In sub-study 1, a single dose of the investigational product will be administered to women undergoing termination of pregnancy, and maternal and fetal blood samples will be collected for determination of sildenafil concentrations. In sub-study 2, sildenafil will be administered three times daily from 3 days before planned delivery until actual delivery, following which maternal and umbilical cord samples will be collected. Proxies of maternal and fetal tolerance as well as markers of fetal pulmonary vasodilation will also be measured. Discussion: This is the first study evaluating in-vivo transplacental passage of sildenafil in humans. Trial registration: EU Clinical Trials Register 2016-002619-17, validated on 12 August 2016. Trial sponsor: UZ Leuven, Herestraat 49, 3000 Leuven.

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Russo, F.M. (Francesca Maria), Benachi, A. (Alexandra), van Mieghem, T., de Hoon, J. N., van Calsteren, K., Annaert, P., … Deprest, J. (2018). Antenatal sildenafil administration to prevent pulmonary hypertension in congenital diaphragmatic hernia (SToP-PH): Study protocol for a phase I/IIb placenta transfer and safety study 11 Medical and Health Sciences 1114 Paediatrics and Reproductive Medicine. Trials, 19(1). doi:10.1186/s13063-018-2897-8