A Study Evaluating the Long-term Safety and Efficacy of VX-121 Combination Therapy

The purpose of this study is to evaluate the long-term safety, tolerability, and efficacy of VX-121/tezacaftor/deutivacaftor (VX-121/TEZ/D-IVA) in participants with cystic fibrosis.

Key Inclusion Criteria: * Part A: Completed study drug treatment in a parent study VX20-121-102 (NCT05033080) and VX20-121-103 (NCT05076149); or had study drug interruption(s) in a parent study but did not permanently discontinue study drug, and completed study visits up to the last scheduled visit of the Treatment Period in the parent study * Part B: Completed study drug treatment in Part A; or had study drug interruption(s) in Part A, but did not permanently discontinue study drug, and completed study visits up to the last scheduled visit of the Treatment Period of Part A Key Exclusion Criteria: * History of drug intolerance in a parent study * Pregnant or breast-feeding females at the time of enrollment in Part A Other protocol defined Inclusion/Exclusion criteria may apply.