Carefully constructed PK/PD models together with biomarker identification and pharmacogenomic profiling for CF are becoming more and more indispensable for various reasons: Firstly, by anticipating how a subset of patients e.g. CFTR mutation and cytochrome status, might react to CFTR modulator treatment, better clinical trials stratifying the patient subset, can be designed to evaluate patient outcomes. This evidence concerns the gene CFTR and cystic fibrosis.