An Open-label Extension Study Evaluating the Long-term Safety, Tolerability, Efficacy, Pharmacokinetics, and Pharmacodynamics of VX-670 in Adult Subjects With Myotonic Dystrophy Type I

Key Inclusion Criteria: • Completed study drug treatment in parent study VX23-670-001 (NCT06185764) Key Exclusion Criteria: • History of any illness or any clinical condition as pre-specified in the protocol Other protocol defined Inclusion/Exclusion criteria may apply.