The CFTR stop mutations imply a “stop” signal in the CFTR protein synthesis, that turns out to be incomplete and it is eliminated by the cell’s quality control system. This research group, thanks a previous project (FFC#3/2017), has developed three molecules which are capable of effectively overcoming the DNA’s stop signal (due to several mutations) in vitro, thus allowing the complete protein’s synthesis. The new project intends to launch a preclinical study in transgenic mouse model containing the UGA-stop signal in the DNA, in order to evaluate the molecules’ efficacy in vivo. Furthermore, it is within the goals of the present project to evaluate the distribution of those substances in vivo, in the animal model organism, so to study also the molecules’ mechanism of action.