Physiologic endpoints for clinical studies for cystic fibrosis

The cystic fibrosis (CF) drug development pipeline promises many exciting new treatments for patients with CF, all which will require clinical studies to prove their benefits on CF lung disease. Historically many pivotal CF studies have used the Forced Expiratory Volume in 1 s (FEV1) as the primary outcome measure, and after demonstrating significant improvements in the treatment group relative to placebo have led to regulatory approval of therapies for routine clinical care. Widespread implementation of these therapies has subsequently led to significant improvements in outcomes for patients with CF. While preserving lung function has obvious benefits to CF patients, as more patients maintain FEV1 in the normal range, it has become increasingly difficult to conduct clinical trials using FEV1 as the primary outcome measure. With multiple concurrent trials competing to enroll from the same pool of patients, there is a need for novel approaches to study end points as well as new physiological outcomes for CF therapeutic trials. In this review we will discuss some of the limitations of FEV1 in the current era of CF care, describe alternative physiological endpoints and outline areas for further research.