A Switch Study From High-Sodium Oxybate to Xywav to Evaluate Changes in Blood Pressure in Participants With Narcolepsy (XYLO)

April 3, 2026 updated by: Jazz Pharmaceuticals

An Open-Label, Multicenter Switch Study Evaluating Changes in Blood Pressure in Participants With Narcolepsy Switching From High-Sodium Oxybate to Xywav

The aim of this study is to quantify the change in blood pressure when participants with narcolepsy treated with high-sodium oxybate are transitioned to Xywav, a low-sodium oxybate. The results of this study may provide health care providers (HCPs), patients, and payers with important new information regarding BP changes related to differences in sodium content between available oxybates for the treatment of narcolepsy.

Study Overview

Status

Completed

Conditions

Intervention / Treatment

Study Type

Interventional

Enrollment (Actual)

155

Phase

  • Phase 4

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

  • Belgium
      • Edegem, Belgium, 2650
        • Antwerp University Hospital (UZA)
      • Namur, Belgium, 5101
        • Private Practice RESPISOM Namur
  • France
    • Herault
      • Montpellier, Herault, France, 34295
        • Hopital Gui de Chauliac
    • Isere
      • Grenoble, Isere, France, 38043
        • CHU de Grenoble - Hôpital Albert Michallon
    • Loire Atlantique
      • Nantes, Loire Atlantique, France, 44093
        • CHU Nantes - Hotel Dieu
  • Italy
      • Bologna, Italy, 40139
        • IRCCS Istituto de Scienze Neurologiche di Bologna (ISNB)
      • Milan, Italy, 20127
        • Ospedale San Raffaele (San Raffaele Turro)
      • Roma, Italy, 00133
        • Azienda Ospedaliera Universitaria Policlinico Tor Vergata
  • Spain
      • Barcelona, Spain, 08035
        • Hospital Universitari Vall d'Hebrón
      • Castellon, Spain, 12004
        • Hospital General de Castellón
      • Madrid, Spain, 28040
        • Hospital Universitario Clínico San Carlos
    • Alava
      • Vitoria-Gasteiz, Alava, Spain, 01004
        • Hospital Universitario Araba - Sede Santiago
  • United States
    • California
      • Culver City, California, United States, 90230
        • Science 37
      • Encino, California, United States, 91436
        • M3 Wake Research
      • Huntington Beach, California, United States, 92647
        • So Cal Clinical Research
      • Lakewood, California, United States, 90805
        • Long Beach Research Institute
      • Redwood City, California, United States, 94063
        • Stanford School of Medicine
      • San Ramon, California, United States, 94583
        • TriValley Sleep Center
      • Santa Ana, California, United States, 92705
        • SDS Clinical Trials, Inc.
    • Florida
      • Boca Raton, Florida, United States, 33486
        • FWD Clinical Research
      • Brandon, Florida, United States, 33511
        • Meris Clinical Research, LLC
      • Miami, Florida, United States, 33169
        • Ocean Wellness Center
      • Miami, Florida, United States, 33176
        • Serenity Research Center LLC
      • Orlando, Florida, United States, 32804
        • Florida Pediatric Research Institute, LLC
    • Georgia
      • Macon, Georgia, United States, 31210
        • Sleep Practitioners, LLC
    • Idaho
      • Nampa, Idaho, United States, 83686
        • Saltzer Medical Group
    • Kentucky
      • Louisville, Kentucky, United States, 40202
        • University Of Louisville
    • Maryland
      • Baltimore, Maryland, United States, 21201
        • University of Maryland Medical Center
    • Massachusetts
      • Newton, Massachusetts, United States, 02459
        • Neurocare, Inc
    • Michigan
      • Lansing, Michigan, United States, 48911
        • Sparrow Health System
    • Nebraska
      • Lincoln, Nebraska, United States, 68506
        • Bryan Medical Center
    • Nevada
      • Henderson, Nevada, United States, 89052
        • Henderson Clinical Trials LLC
    • North Carolina
      • Huntersville, North Carolina, United States, 28078
        • Advanced Respiratory and Sleep Medicine, PLLC
    • Ohio
      • Cincinnati, Ohio, United States, 45245
        • Intrepid Research, LLC
      • Cleveland, Ohio, United States, 44106
        • University Hospitals Cleveland Medical Center
      • Dublin, Ohio, United States, 43017
        • Ohio Sleep Medicine and Neuroscience
    • Oregon
      • Portland, Oregon, United States, 97239
        • OHSU Hospital
    • Pennsylvania
      • Abington, Pennsylvania, United States, 19001
        • Abington Neurological Associates, LTD
    • South Carolina
      • Columbia, South Carolina, United States, 29201
        • Bogan Sleep Consultants, LLC
      • Greenville, South Carolina, United States, 29615
        • Velocity Clinical Research, Greenville
      • Rock Hill, South Carolina, United States, 29732
        • Clinical Research of Rock Hill
    • Texas
      • Austin, Texas, United States, 78731
        • FutureSearch Trials of Neurology
      • San Antonio, Texas, United States, 78229
        • Sleep Therapy & Research Center

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:

  • Participants must be 18 to 70 years of age inclusive, at the time of signing the informed consent.
  • Participants have a documented diagnosis of Type 1 or Type 2 narcolepsy that meets International Classification of Sleep Disorders (ICSD)-3 or Diagnostic and Statistical Manual of Mental Disorders (DSM)-5 criteria.
  • Participants must have been receiving a total dose of high-sodium oxybate (eg, XYREM) of 6 to 9 g/night (inclusive) with twice-nightly dosing for a minimum of 6 consecutive weeks prior to screening.
  • If currently treated with stimulants and/or alerting agents or other medications known to affect BP, participant must have been taking the same dosing regimen for at least 2 months prior to screening and agree to take the same dose throughout the study.
  • If currently taking stable doses of antihypertensive therapies, participant must maintain these treatments at the same dose throughout the study unless otherwise advised by their medical care
  • Participant is male or female. A female participant is eligible to participate if she is not pregnant or breastfeeding, if she is a woman of nonchildbearing potential or is a woman of childbearing potential and using a contraceptive method that is highly effective.

Key Exclusion Criteria:

  • History or presence of any acutely unstable medical condition, behavioral or psychiatric disorder (including active suicidal ideation), or surgical history that could affect the safety of the participant or interfere with study assessments or the ability of the participant to complete the study based on the judgment of the investigator.
  • Presence of significant cardiovascular disease or cardiovascular condition that in the investigator's opinion may jeopardize participant safety in the study, including screening ECG results.
  • Presence of atrial fibrillation detected on screening electrocardiogram (ECG).
  • Presence of resistant hypertension.

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: JZP258
Eligible participants will be switched, on a gram-for-gram basis, from their prescribed twice-nightly high-sodium oxybate (such as xyrem) to Xywav. Participants who, in the opinion of the investigator, require an adjustment to their Xywav dosing, can increase or decrease their dose by 1.5 grams per night as long as the participant's total nightly dose is between 6 to 9 grams per night.
Drug: JZP258
0.5 g/ml calcium, magnesium, potassium, and sodium oxybates oral solution
Other Names:
  • Xywav

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Time Frame
Change From Baseline to End of Treatment (EOT) Visit on the 24-hour Average Systolic Blood Pressure (SBP) in mmHg
Time Frame: Baseline (Screening) and End of Treatment (EOT) Visit, up to 6 weeks
Baseline (Screening) and End of Treatment (EOT) Visit, up to 6 weeks

Secondary Outcome Measures

Outcome Measure
Time Frame
Change From Baseline to EOT Visit on the Daytime Average SBP in mmHg
Time Frame: Baseline (Screening) and End of Treatment (EOT) Visit, up to 6 weeks
Baseline (Screening) and End of Treatment (EOT) Visit, up to 6 weeks
Change From Baseline to EOT Visit on the Seated Resting Average SBP in mmHg
Time Frame: Baseline (Screening) and End of Treatment (EOT) Visit, up to 6 weeks
Baseline (Screening) and End of Treatment (EOT) Visit, up to 6 weeks
Change From Baseline to EOT Visit on the Nighttime Average SBP in mmHg
Time Frame: Baseline (Screening) and End of Treatment (EOT) Visit, up to 6 weeks
Baseline (Screening) and End of Treatment (EOT) Visit, up to 6 weeks

Collaborators and Investigators

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

Sponsor

Jazz Pharmaceuticals

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

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)

June 26, 2023

Primary Completion (Actual)

February 25, 2025

Study Completion (Actual)

March 10, 2025

Study Registration Dates

First Submitted

May 12, 2023

First Submitted That Met QC Criteria

May 12, 2023

First Posted (Actual)

May 22, 2023

Study Record Updates

Last Update Posted (Actual)

April 24, 2026

Last Update Submitted That Met QC Criteria

April 3, 2026

Last Verified

April 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • JZP258-406

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

YES

IPD Plan Description

In accordance with ICMJE requirements, Jazz Pharmaceuticals may provide qualified external researchers access to individual participant data (IPD) and clinical trial data that underlie the results of this trial upon request. Qualified researchers can submit a request on https://www.jazzpharma.com/science/clinical-trial-data-sharing/ as outlined. Jazz Pharmaceuticals reserves the right not to consider a request. For inquiries about Jazz's data sharing policy contact clinicaldatasharing@jazzpharma.com.

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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