This is a two-part, multi-center, prospective longitudinal, exploratory study of highly effective cystic fibrosis transmembrane conductance regulator (CFTR) modulators and their impact in children with cystic fibrosis (CF) on endocrine growth factors and height, gastrointestinal function and gut microbiome, lung function and respiratory microbiome, liver and pancreatic function, sweat chloride, inflammatory markers, and bone health.~Total duration of the study is expected to be 6 years. Part A will be a prospective cross-sequential study to describe the natural history of hormonal growth factors in early childhood and assess the feasibility of additional measurements. In Part A, subjects will have up to 6 visits over a period of up to 3 years.~Part B will be a prospective longitudinal study to observe the effects of administration of either ivacaftor or elexacaftor/tezacaftor/ivacaftor (elex/tez/iva) on growth. In Part B, subjects will have one before ivacaftor or elex/tez/iva visit within 30 days before initiation of the therapy and five after ivacaftor or elex/tez/iva visits over a 24-month follow-up period.
This is a two-part, multi-center, prospective longitudinal, exploratory study of highly effective cystic fibrosis transmembrane conductance regulator (CFTR) modulators and their impact on children with cystic fibrosis (CF).