Impact of Discontinuing Dornase Alfa in People With CF on Highly Effective CFTR Modulator Therapy-A SIMPLIFY Sub-Study

Despite the increasingly common use of cystic fibrosis transmembrane conductance regulator (CFTR) modulator therapies in treating cystic fibrosis (CF), it is still largely unknown whether or not other chronic therapies can be safely stopped. This SIMPLIFY sub-study is being done to test whether or not it is safe to stop taking dornase alfa (Dnase) in those people that are also taking elexacaftor/tezacaftor/ivacaftor (ETI). ETI is a combination CFTR modulator therapy that was approved by the Food and Drug Administration for people with CF who have at least one F508del mutation. The three drugs that make up ETI work together to allow many more chloride ions to move into and out of the cells, improving the balance of salt and water in the lungs. These changes result in better clearance of mucus from the lungs and improvements in lung function. Dornase alfa (Dnase) also improves clearance of mucus from the lungs to support lung function and has been available to people with CF for many years. Dnase is considered to be relatively burdensome and it is not known whether Dnase can improve or maintain lung function above what is already gained through ETI use. The goal of this SIMPLIFY sub-study is to get information about whether or not it is safe to stop Dnase by testing if there is a change in lung function in participants with cystic fibrosis (CF) who are assigned to stop taking Dnase as compared to those who are assigned to keep taking Dnase while continuing to take ETI. This is a sub study of master protocol SIMPLIFY-IP-19, NCT04378153. The sub study investigating the impact of discontinuing and continuing hypertonic saline is registered under NCT06350461.