A Rollover Safety Study of Lumacaftor/Ivacaftor in Subjects Aged 2 Years and Older With Cystic Fibrosis, Homozygous for the F508del-CFTR Mutation

Inclusion Criteria: Subjects entering the Treatment Cohort must meet the following criteria: * Completed 24 weeks of LUM/IVA treatment and the Safety Follow-up Visit in Study VX15-809-115 Part B (Study 115B, NCT02797132) * Willing to remain on a stable CF medication regimen through the Safety Follow-up Visit Subjects entering the Observational Cohort must meet 1 of the following criteria: * Completed 24 weeks of LUM/IVA treatment and the Safety Follow-up Visit in Study 115B, but do not want to enroll in the Treatment Cohort. * Received at least 4 weeks of LUM/IVA treatment and completed visits up to Week 24 and the Safety Follow-up Visit, if required, of Study 115B but are not taking LUM/IVA at the end of the Study 115B Treatment Period (i.e., Week 24) because of a drug interruption and either did not receive Vertex approval to enroll in the Treatment Cohort or do not want to enroll in the Treatment Cohort. * Permanently discontinued LUM/IVA in Study 115B after receiving at least 4 weeks of treatment and remained in the study from the time of treatment discontinuation through the Week 24 Visit and Safety Follow-up Visit, if required. Exclusion Criteria (Treatment Cohort Only): * Prematurely discontinued LUM/IVA treatment in Study 115B. * History of any comorbidity or laboratory abnormality that, in the opinion of the investigator, might confound the results of the study or pose an additional risk in administering LUM/IVA to the subject * History of drug intolerance or other serious reactions to LUM/IVA in Study 115B that would pose an additional risk to the subject in the opinion of investigator, and which should be discussed with the Vertex medical monitor. * Subjects with a history of allergy or hypersensitivity to LUM/IVA. * Liver function test (LFT) abnormality meeting criteria for LUM/IVA treatment interruption at the completion of Study 115B, for which no convincing alternative etiology is identified. * QTc value at the completion of Study 115B that would pose an additional risk to the subject in the opinion of investigator, and which should be discussed with the Vertex medical monitor * History of poor compliance with LUM/IVA and/or procedures in Study 115B as deemed by the investigator. * Participation in an investigational drug trial (including studies investigating LUM and/or IVA) other than Study 115B.