Forecasting US ivacaftor outcomes and cost in cystic fibrosis patients with the G551D mutation

Abstract

Ivacaftor, a breakthrough treatment for cystic fibrosis (CF) patients with the G551D genetic mutation, lacks long-term clinical and cost projections. This study forecasted outcomes and cost by comparing ivacaftor plus usual care versus usual care alone.A lifetime Markov model was conducted from a US payer perspective. The model consisted of five health states: 1) forced expiratory volume in 1 s (FEV1) % pred ≥70%, 2) 40%≤ FEV1 % pred <70%, 3) FEV1 % pred <40%, 4) lung transplantation and 5) death. All inputs were extracted from published literature. Budget impact was also estimated. We estimated ivacaftor's improvement in outcomes compared with a non-CF referent population.Ivacaftor was associated with 18.25 (95% credible interval (CrI) 13.71–22.20) additional life-years and 15.03 (95% CrI 11.13–18.73) additional quality-adjusted life-years (QALYs). Ivacaftor was associated with improvements in survival and QALYs equivalent to 68% and 56%, respectively, for the survival and QALY gaps between CF usual care and their non-CF peers. The incremental lifetime cost was $3 374 584. The budget impact was $0.087 per member per month.Ivacaftor increased life-years and QALYs in CF patients with the G551D mutation, and moved morbidity and mortality closer to that of their non-CF peers. Ivacaftor costs much more than usual care, but comes at a relatively limited budget impact.