CFTR and cystic fibrosis: Thus, the primary objective of this study was to assess the cost-effectiveness of lumacaftor and ivacaftor combination for the treatment of 12 year-old patients with CF homozygous for F508del CFTR gene compared to usual care in the US from a payer’s perspective at a willingness to pay (WTP) threshold of $150,000 per quality adjusted life year (QALY) gained over a time horizon of two, four, six, eight and ten years.