JC Viremia in Natalizumab-Treated Patients with Multiple Sclerosis

Abstract

Ivacaftor, an oral potentiator of the cystic fibrosis transmembrane conductance regulator (CFTR) protein, has been shown to be efficacious in patients heterozygous for the G551D mutation in CFTR. This letter describes the effect of ivacaftor in a patient homozygous for this mutation.To the Editor: Recent studies provide support for the usefulness of the oral potentiator ivacaftor in patients with cystic fibrosis who are heterozygous for the G551D mutation.(1) The possibility of an increased response in persons who are homozygous for the mutation is unknown because of its low prevalence. Ivacaftor potentiates the open-channel probability of the G551D-cystic fibrosis transmembrane conductance regulator (CFTR) protein.(1) The most common cystic fibrosis mutation, F508del, results in little or no CFTR reaching the cell surface, whereas with the G551D-CFTR mutation, there are potentially normal levels of nonfunctional CFTR channels at the cell surface.(2) Therefore, we postulate ...