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

August 6, 2026 updated by: Vertex Pharmaceuticals Incorporated

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

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).

Study Overview

Status

Enrolling by invitation

Conditions

Intervention / Treatment

Study Type

Interventional

Enrollment (Estimated)

44

Phase

  • Phase 2

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • Australia
      • Auchenflower, Australia
        • Wesley Research Institute
      • Melbourne, Australia
        • Neuroscience Clinical Trials Unit, Alfred Brain
  • Belgium
      • Leuven, Belgium
        • Universitaire Ziekenhuizen Leuven - Campus Gasthuisberg - Pulmonology
  • Canada
      • Montreal, Canada
        • Altasciences Montreal
      • Montreal, Canada
        • Montreal Neurological Institute-Hospital
      • Ottawa, Canada
        • University of Ottawa
      • Québec, Canada
        • Universite Laval - Neurology
  • Germany
      • München, Germany
        • Friedrich Baur Institute
  • Netherlands
      • Maastricht, Netherlands
        • Maastricht UMC
  • Spain
      • Valencia, Spain
        • Hospital Universitario y Politecnico La Fe - Neurology
  • United Kingdom
      • Glasgow, United Kingdom
        • Queen Elizabeth University Hospital - Neurology
      • London, United Kingdom
        • Leonard Wolfson Experimental Neurology Centre CRF
      • Sheffield, United Kingdom
        • Royal Hallamshire Hospital - Neurology
  • United States
    • Missouri
      • St Louis, Missouri, United States, 63110
        • St. Louis Children's Hospital - Neurology
    • Virginia
      • Richmond, Virginia, United States, 23298
        • Virginia Commonwealth University - Sanger Hall

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Description

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.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: N/A
  • Interventional Model: Single Group Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: VX-670
Participants will receive multiple doses of VX-670.
Drug: VX-670
Solution for intravenous administration.

What is the study measuring?

Primary Outcome Measures

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

Secondary Outcome Measures

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

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Vertex Pharmaceuticals Incorporated

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

April 28, 2025

Primary Completion (Estimated)

January 30, 2029

Study Completion (Estimated)

January 30, 2029

Study Registration Dates

First Submitted

April 10, 2025

First Submitted That Met QC Criteria

April 10, 2025

First Posted (Actual)

April 14, 2025

Study Record Updates

Last Update Posted (Actual)

August 10, 2026

Last Update Submitted That Met QC Criteria

August 6, 2026

Last Verified

August 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • VX24-670-101
  • 2024-517983-47-00 (Other Identifier: EU CT Number)

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

IPD Plan Description

Details on Vertex data sharing criteria and process for requesting access can be found at: https://www.vrtx.com/our-science/clinical-trials-data-sharing/

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

Yes

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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