Overall, our results demonstrated that Q1291H/F508del CFTR resulted in reduced baseline CFTR activity, and that this individual had minimal response to IVA, ELX/TEZ and ETI therapy in vitro. Variability in the clinical presentation of CF and response to modulators highlight a need for personalized drug response testing as it is known that drug response is heterogenous between different individuals, even those of the same mutation. This evidence concerns the gene CFTR and cystic fibrosis.