CFTR and cystic fibrosis: This drug is a potentiator of the channel activity of an P-gp homolog, the cystic fibrosis transmembrane conductance regulator CFTR/ABCC7 [24], and ivacaftor is now widely used in the clinic, both on its own as well as in combination with CFTR-corrector compounds such that roughly 90% of CF patients may now be treatable [25,26].