The use of ivacaftor in CFTR mutations resulting in residual functioning protein

INTRODUCTION Ivacaftor, a cystic fibrosis transmembrane regulator (CFTR) potentiator is currently approved for use in individuals with class III gating mutations and the R117H mutation, a non-gating mutation with residual functioning CFTR. Nevertheless, ivacaftor may also be effective in individuals who have CF mutations giving rise to a residual functioning protein. However, aside from case reports involving a single patient, little data exist on the use of ivacaftor in such individuals. METHODS A real life pragmatic report wherein seven adults with mutations resulting in a CFTR with residual function were prescribed ivacaftor. Four individuals with similar mutations acted as comparison. We assessed lung function, body mass index, sweat chloride; the number of acute respiratory exacerbations and health related quality of life. RESULTS Patients with residual functioning CFTR showed significant improvement or stabilization in all parameters up to 3 years following the start of ivacaftor. Those with similar mutations and who did not receive ivacaftor worsened. CONCLUSION We report the use of ivacaftor in seven adults with various Class IV and V non-gating CFTR mutation with residual functioning protein and we demonstrate improvement in several clinical parameters.