Patients with the rs75527207 AA genotype (two copies of the CFTR G551D variant) and cystic fibrosis may respond to ivacaftor treatment. FDA-approved drug labeling information and CPIC guidelines indicate use of ivacaftor in cystic fibrosis patients with at least one copy of a list of 33 CFTR genetic variants, including G551D. Other genetic and clinical factors may also influence response to ivacaftor.