['To investigate the effect of treatment with ivacaftor on insulin secretion in patients with cystic fibrosis (CF) (ΔF508\\S549R) having CFRD/impaired insulin secretion.', 'A standard OGTT was performed before and after 16weeks of treatment with ivacaftor in 2 sibling patients with CF carrying the S549R gating mutation. The area under the curve (AUC) for glucose and insulin was calculated using the trapezoidal estimation.', 'Before treatment, the OGTT of case 1 showed indeterminate glycemia; the OGTT of case 2 indicated CFRD. After ivacaftor treatment the OGTT demonstrated improved insulin secretion pattern mainly by increased first phase early insulin secretion, resulting in reduction of the AUC of glucose in both cases.'] Does cFTR potentiator therapy ameliorate impaired insulin secretion in CF patients with a gating mutation?