The purpose of this study evaluates the efficacy and safety of VX-121/tezacaftor/deutivacaftor (VX-121/TEZ/D-IVA) in CF participants who were heterozygous for F508del and a minimal function mutation (F/MF participants).
Key Inclusion Criteria: * Heterozygous for F508del and a minimal function mutation (F/MF genotype) * Forced expiratory volume in 1 second (FEV1) value \>=40% and \<=90% of predicted mean for age, sex, and height for participants currently receiving ELX/TEZ/IVA therapy; FEV1 \>=40% and \<=80% for participants not currently receiving ELX/TEZ/IVA Key Exclusion Criteria: * History of solid organ or hematological transplantation * Hepatic cirrhosis with portal hypertension, moderate hepatic impairment (Child Pugh Score 7 to 9), or severe hepatic impairment (Child Pugh Score 10 to 15) * Lung infection with organisms associated with a more rapid decline in pulmonary status * Pregnant or breast-feeding females Other protocol defined Inclusion/Exclusion criteria may apply