Lumacaftor/ivacaftor reduces exacerbations in adults homozygous for Phe508del mutation with severe lung disease.

BACKGROUND: Lumacaftor/ivacaftor (LUM/IVA) improves outcomes in cystic fibrosis (CF) patients homozygous for Phe508del with ppFEV1 > 40%. There is limited safety or efficacy data in patients with ppFEV1 < 40%. We determined whether LUM/IVA in patients with ppFEV1 < 40 would reduce the rate of pulmonary exacerbations.

METHODS: This was a case control study performed on patients > 12 years, homozygous for Phe508del CFTR mutation and with ppFEV1 < 40%. Control subjects were matched for age, sex and ppFEV1, and had mutations ineligible for LUM/IVA. We assessed the rate of pulmonary exacerbations requiring intravenous antibiotics, the mean rate of change in ppFEV1 over 12 months and all adverse events.

RESULTS: Data was collected from 7 Australian CF centres on 105 patients; 72 on LUM/IVA and 33 controls. LUM/IVA demonstrated a large reduction in exacerbations with an incident rate ratio of 0.455 (95%CI; 0.306 - 0.676), p <  0.001 after adjusting for the number of exacerbations in the previous 12 months. LUM/IVA prolonged the time to first exacerbation and reduced the rate of decline in ppFEV1 over 12 months. Adverse events were common; chest tightness or dyspnoea was experienced by 55% and resulted in cessation of treatment in 32%.

CONCLUSIONS: Treatment with LUM/IVA resulted in a substantially lower rate of pulmonary exacerbations, prolonged time to first exacerbation and slowed the rate of decline of ppFEV1 in participants with severe lung disease. Adverse reactions to LUM/IVA however were unacceptably frequent, and resulted in a very high discontinuation rate.