CFTR and cystic fibrosis: 43 patients (n = 6 < 18 years), treated with highly effective CFTR-modulator therapy with elexacaftor–tezacaftor–ivacaftor (ELX/TEZ/IVA) were included, as were 20 controls with cystic fibrosis but without CFTR-modulator therapy (n = 6 < 18 years).