Previous studies of these researchers (projects FFC#26/2011 and FFC#6/2013) showed the possibility to evaluate CFTR function in peripheral blood cells. The assay relies on the Iodine-dependent change of fluorescence of a reporter protein. Iodine can in fact be effectively transported by CFTR channel instead of chloride ions. The aim of the new project is to evaluate the capability of this approach to measure the effect of new drugs targeting the CFTR basic defect. CF patients with class III (responsive to Ivacaftor), and class I (responsive to PTC124) mutations included in clinical trials will be tested. Additional patients carrying other gating mutations will be also evaluated. This approach might represent an innovative and convenient CFTR functional assay.