Such therapeutic approaches have been successful for CFTR in cystic fibrosis (43), clinically tested for enzyme deficiencies (44), and explored for norepinephrine, dopamine, and serotonin transporters NET/SLC6A2, DAT/SLC6A3, and SERT/SLC6A4 (45). This evidence concerns the gene SLC6A4 and cystic fibrosis.