A Study to Evaluate Safety, Efficacy, and Tolerability of TEZ/IVA in Orkambi® (Lumacaftor/Ivacaftor) -Experienced Subjects With Cystic Fibrosis (CF)

Inclusion Criteria:

• Willing and able to comply with scheduled visits, treatment plan, study restrictions,laboratory tests, contraceptive guidelines, and other study procedures.

• Prior discontinuation of Orkambi, with at least 1 respiratory sign or symptomconsidered related to therapy.

• Resolution or stabilization of qualifying event(s) >28 days prior to Screening.

• Discontinuation of Orkambi therapy must have occurred within approximately 12 weeksfrom the first dose of Orkambi.

• Homozygous for F508del mutation in the CFTR gene as documented in the subject'smedical record. If genotype documentation is not available in the medical record,genotyping will be performed during screening.

• FEV1 ≥25% and ≤90% of predicted normal for age, sex, and height.

• Stable CF disease as judged by the investigator.

• Other protocol defined inclusion criteria could apply.

Exclusion Criteria:

• History of any comorbidity that, in the opinion of the investigator, might confoundthe results of the study or pose an additional risk in administering study drug to thesubject.

• Recent rapid or progressive deterioration in respiratory status.

• Receiving continuous oxygen at >2L/min or on face-mask ventilation.

• Any protocol-defined exclusionary laboratory values at Screening.

• Child-Pugh Class B or C hepatic impairment.

• An acute upper or lower respiratory infection, pulmonary exacerbation, or change intherapy for pulmonary disease within 28 days before Day 1.

• Documentation of colonization with organisms associated with a more rapid decline inpulmonary status.

• History of lung transplantation since most recent initiation of Orkambi.

• History of alcohol or drug abuse in the past year as deemed by the investigator.

• Participation in an investigational drug study or use of a CFTR modulator within 28days or 5 terminal half-lives of the investigational drug or modulator (whichever islonger).

• Use of restricted medications or foods within the specified window before the firstdose of study drug, or an anticipated need or use of restricted medication or foodsafter the first dose of study drug.

• Pregnant or nursing females: Females of child-bearing potential must have a negativepregnancy test at Screening and Day 1.

• Other protocol defined exclusion criteria could apply.