The Balance between the Safety of Mother, Fetus, and Newborn Undergoing Cystic Fibrosis Transmembrane Conductance Regulator Treatments during Pregnancy

The recent development of modulators of cystic fibrosis transmembrane conductance regulator (CFTR) has allowed the life expectancy of cystic fibrosis patients to increase substantially resulting in more women with cystic fibrosis reaching child-bearing age. This however raises the issue of whether long-term use of CFTR modulators during pregnancy and breastfeeding is safe for the fetus and newborn, especially for their developing brain. A very limited number of case reports available so far has shown that the fetus or breastfed newborn is likely to be exposed to maternally administered CFTR modulators. Potential impacts of drug exposure on the developing brain are of particular importance as the consequences might not be immediately noticeable upon birth but may manifest later in life as permanent neurobehavioral problems. In order for drugs in maternal circulation to enter the fetal brain, they must overcome the placental barrier followed by a series of brain barriers, each consisting of cellular components and physiological mechanisms such as efflux transporters. The extent of protection they offer during development will provide valuable insights into the potential entry and the effects of CFTR modulators in the developing brain. This review aims to explore the current understanding of the safety of CFTR modulators, especially ivacaftor, during pregnancy and breastfeeding, characterize the pharmacokinetics and pharmacodynamics of ivacaftor, both under normal conditions and during pregnancy, to provide context for its potential impact on the developing brain. Finally, we discuss the determinants that need to be taken into consideration when investigating the entry of drugs into the fetus and newborn.