An Open-label Extension Safety Study of MELAS Patients Who Completed TIS6463-203 (PRIZM)

April 30, 2026 updated by: Tisento Therapeutics

An Open-label Extension Study Evaluating the Safety of Zagociguat in Participants With MELAS Who Completed TIS6463-203

The goal of this clinical trial is to evaluate the long-term safety and tolerability of zagociguat in patients with MELAS who completed study medication treatment in the lead-in study TIS6463-203. TIS6463-204 is evaluating zagociguat in an open-label extension study at the daily dose of 15mg. The study medication is a once daily oral table and will be provided at the clinic and/or shipped to the participant's home. Study assessments will be conducted during clinic visits which will occur at three months and then at six months. Thereafter, clinic visits will occur every six months.

Study Overview

Status

Enrolling by invitation

Conditions

Intervention / Treatment

Detailed Description

On Screening Visit Day -1 (which corresponds to Period 2 Week 12 Visit from lead-in study TIS6463-203), participants will sign the informed consent form, be confirmed eligible for this open-label extension study and undergo Screening Visit assessments. Eligible participants will begin dosing the next day on Day 1 (there is no Day 0) at home. Participants will have a 3-month visit and 6-month study visit at the clinic and thereafter will have a clinic visit every 6 months. Participants should have a Follow-up Visit 4 (+1) weeks after zagociguat discontinuation.

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
    • New South Wales
      • Sydney, New South Wales, Australia, NSW 2031
        • Neuroscience Research Australia
    • Victoria
      • Melbourne, Victoria, Australia, 3052
        • Royal Melbourne Hospital
  • Germany
      • Munich, Germany, 80336
        • LMU Klinikum, Friedrich-Baur-Institute, Department of Neurology
  • Italy
      • Milan, Italy, 20133
        • Neurologic Institute Carlo Besta of Milan
      • Rome, Italy, 00168
        • Fondazione Policlinico Universitario Agostino Gemelli
  • United Kingdom
      • London, United Kingdom, WC1N 3BG
        • University College London Hospital. The National Hospital for Neurology and Neurosurgery, Centre for Neuromuscular Diseases
      • Newcastle upon Tyne, United Kingdom, NE14LP
        • The Newcastle upon Tyne NHS Foundation Trust
  • United States
    • California
      • La Jolla, California, United States, 92037
        • UC San Diego - Altman Clinical and Translational Research Institute
    • Colorado
      • Aurora, Colorado, United States, 80045
        • Children's Hospital of Colorado
    • Georgia
      • Atlanta, Georgia, United States, 30329
        • Rare Disease Research
    • Massachusetts
      • Boston, Massachusetts, United States, 02114
        • Massachusetts General Hospital
    • New York
      • New York, New York, United States, 10029
        • Mount Sinai - Ichan School of Medicine
    • Ohio
      • Akron, Ohio, United States, 44308
        • Akron Children's Hospital
    • Pennsylvania
      • Philadelphia, Pennsylvania, United States, 19104
        • Children's Hospital of Philadelphia
    • Texas
      • Houston, Texas, United States, 77030
        • Baylor College of Medicine
      • Houston, Texas, United States, 77030
        • UT Health Houston

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

  • Child
  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  1. Signed an Institutional Review Board (IRB)/Independent Ethics Committee (IEC)-approved informed consent form (ICF).
  2. Completed TIS6463-203 treatment through the Period 2 Week 12 Visit.
  3. Agrees to follow lifestyle restrictions.
  4. Other criteria per the protocol.

Exclusion Criteria:

1. Any medical condition or clinical finding that, per investigator judgement, would preclude safe study participation and/or completion of all trial requirements.

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: Zagociguat 15mg
Participants receive zagociguat 15 mg once a day (QD) for the duration of the study.
Drug: zagociguat 15mg
once daily oral tablets
Other Names:
  • CY6463
  • IW-6463

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Incidence of Treatment-emergent Adverse Events (TEAEs)
Time Frame: Day 1 through the Follow-up for treatment period 4 weeks after last dose of study medication.
TEAEs are any untoward event that may or may not be related to study medication.
Day 1 through the Follow-up for treatment period 4 weeks after last dose of study medication.

Collaborators and Investigators

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

Sponsor

Tisento Therapeutics

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)

August 18, 2025

Primary Completion (Estimated)

July 1, 2028

Study Completion (Estimated)

July 1, 2028

Study Registration Dates

First Submitted

April 28, 2025

First Submitted That Met QC Criteria

May 6, 2025

First Posted (Actual)

May 7, 2025

Study Record Updates

Last Update Posted (Actual)

May 4, 2026

Last Update Submitted That Met QC Criteria

April 30, 2026

Last Verified

March 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • TIS6463-204

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

Yes

Studies a U.S. FDA-regulated device product

No

product manufactured in and exported from the U.S.

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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