A Phase 2 Study to Evaluate Efficacy and Safety of VX-561 in Subjects Aged 18 Years and Older With Cystic Fibrosis

The purpose of this study is to evaluate the efficacy, safety, pharmacodynamic (PD) and pharmacokinetic (PK) effect of VX-561.

Key Inclusion Criteria:

* Must have 1 of the following 9 CFTR mutations on at least 1 allele: G551D, G178R, S549N, S549R, G551S, G1244E, S1251N, S1255P, or G1349D
* On ivacaftor therapy
* FEV1 value ≥40% and ≤100% of predicted mean for age, sex, and height

Key Exclusion Criteria:

* History of clinically significant cirrhosis with or without portal hypertension
* History of solid organ or hematological transplantation
* Lung infection with organisms associated with a more rapid decline in pulmonary status

Other protocol defined Inclusion/Exclusion criteria may apply