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Enrolling by invitationNCT06926621Updated Aug 10, 2026

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

A Phase 2 interventional study of VX-670 in Myotonic Dystrophy Type 1 (DM1), sponsored by Vertex Pharmaceuticals Incorporated. Enrolling by invitation at 15 sites in 8 countries. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-08-10.

Sponsored by Vertex Pharmaceuticals Incorporated · Phase 2, Interventional, and Treatment

Phase
Phase 2
Study type
Interventional
Enrollment
44
Allocation
Not applicable
Ages
18 Years and older
Sex
All
01

Study 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).

02

Conditions studied

  • 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
03

Who can participate

Ages eligible
18 Years and older
Sexes eligible
All
Accepts healthy volunteers
No

Eligibility 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/Exclusion criteria may apply.

04

Study design

Phase
Phase 2
Primary purpose
Treatment
Allocation
Not applicable
Intervention model
Single group
Masking
None (open label)
Enrollment
44 participants (estimated)

Study arms

  • Experimental
    VX-670

    Participants will receive multiple doses of VX-670.

    Drug: VX-670

Interventions

  • DrugVX-670

    Solution for intravenous administration.

05

What researchers measure

Primary outcomes

  1. 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

Secondary outcomes

  1. Maximum Observed Concentration (Cmax) of VX-670 and its Active Component in Plasma

    Time frame: From Day 1 up to Week 96

  2. 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

06

Study locations

15 sites
  • St. Louis Children's Hospital - Neurology
    St Louis, Missouri 63110, United States
  • Virginia Commonwealth University - Sanger Hall
    Richmond, Virginia 23298, United States
  • Wesley Research Institute
    Auchenflower, Australia
  • Neuroscience Clinical Trials Unit, Alfred Brain
    Melbourne, Australia
  • Universitaire Ziekenhuizen Leuven - Campus Gasthuisberg - Pulmonology
    Leuven, Belgium
  • Altasciences Montreal
    Montreal, Canada
  • Montreal Neurological Institute-Hospital
    Montreal, Canada
  • University of Ottawa
    Ottawa, Canada
  • Universite Laval - Neurology
    Québec, Canada
  • Friedrich Baur Institute
    München, Germany
  • Maastricht UMC
    Maastricht, Netherlands
  • Hospital Universitario y Politecnico La Fe - Neurology
    Valencia, Spain
  • Queen Elizabeth University Hospital - Neurology
    Glasgow, United Kingdom
  • Leonard Wolfson Experimental Neurology Centre CRF
    London, United Kingdom
  • Royal Hallamshire Hospital - Neurology
    Sheffield, United Kingdom
07

References and documents

Individual participant data

Plan to share: No — 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/

No publications or documents are linked to this record.

08

Registry details

Key details

Study ID
NCT06926621
Lead sponsor
Vertex Pharmaceuticals Incorporated
Responsible party
Sponsor
First posted
Apr 14, 2025
Start date
Apr 28, 2025
Primary completion
Jan 30, 2029 (estimated)
Completion
Jan 30, 2029 (estimated)
Last update
Aug 10, 2026

Oversight

FDA-regulated drug
Yes
FDA-regulated device
No
View the source record on ClinicalTrials.gov ↗

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