By contrast, most (96.3%) of the 33 patients in the KIWI study (36), a 24-week single-arm study of ivacaftor in children aged 2–5 years with a CFTR gating mutation, had inadequate FE-1 levels at baseline, and by week 24, more than 25% of them displayed an elevation above the clinical cutoff for exocrine pancreatic insufficiency (200 μg/g). The gene discussed is CFTR; the disease is exocrine pancreatic insufficiency.