Results from IVA targeting G551D mutation [36] were considered the benchmark for the development of following CFTR modulators: accordingly, LUM/IVA and TEZ/IVA showed a modest clinical benefit, while ELX/TEZ/IVA was recognized as the standard of care for genotypes carrying at least one F508del mutation, namely the most frequent allelic variant in CF: with slight geographical differences, current CFTR modulators could target on average 70–80% of CF patients [40, 41]. The gene discussed is CFTR; the disease is cystic fibrosis.