A Study of Long-term Safety and Efficacy of VX-670 in Participants With Myotonic Dystrophy Type I

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

Status

Enrolling by invitation

Phases

Phase 2

Study type

Interventional

Source

ClinicalTrials.gov

Registry ID

NCT06926621

Enrollment

Registered

2025-04-14

Start date

2025-04-28

Completion date

2029-01-30

Last updated

2026-08-10

For informational purposes only — not medical advice. Sourced from public registries and may not reflect the latest updates. Terms

Conditions

Myotonic Dystrophy Type 1 (DM1)

Keywords

DM 1, Myotonic Dystrophy 1, Myotonic Dystrophy Type 1 (DM1), VX-670, Myotonic Dystrophy, DM, Myotonia, Dystrophy Myotonic, Myotonic Disorders, Steinert Disease, Vertex, Entrada, PMO, ASO, Myotonic Muscular Dystrophy, Muscular Disorders, Atrophic, Muscular Diseases, Musculoskeletal Diseases, Neuromuscular Diseases, Nervous System Diseases, Genetic Diseases, Inborn, Heredodegenerative Disorders, Nervous System, Neurodegenerative Diseases, Muscular Dystrophies

Brief summary

The purpose of the study is to evaluate the long-term safety and tolerability, efficacy and pharmacokinetics of VX-670 in participants with Myotonic Dystrophy Type I (DM1).

Interventions

DRUGVX-670

Solution for intravenous administration.

Study design

Allocation

Intervention model

SINGLE_GROUP

Primary purpose

TREATMENT

Masking

NONE

Eligibility

Sex/Gender

ALL

Age

18 Years to No maximum

Healthy volunteers

Inclusion criteria

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/

Design outcomes

Primary

Measure	Time frame
Safety and Tolerability as Assessed by Number of Participants With Adverse Events (AEs) and Serious Adverse Events (SAEs)	From Day 1 up to Week 108

Secondary

Measure	Time frame
Maximum Observed Concentration (Cmax) of VX-670 and its Active Component in Plasma	From Day 1 up to Week 96
Area Under the Concentration Versus Time Curve (AUC) of VX-670 and its Active Component in Plasma	From Day 1 up to Week 96

Countries

Australia, Belgium, Canada, Germany, Netherlands, Spain, United Kingdom, United States

Outcome results

None listed

Source: ClinicalTrials.gov · Data processed: Aug 11, 2026