NarcolepsyPhase 4XYLONCT05869773
A Switch Study From High-Sodium Oxybate to Xywav to Evaluate Changes in Blood Pressure in Participants With Narcolepsy
A Phase 4 study testing JZP258 in people with Narcolepsy, run by Jazz Pharmaceuticals at 43 sites in 5 countries.
Trial summary
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. Read more about this study
- Who is it for?
- Ages 18 to 70 years
- Conditions the study is for
- Narcolepsy
- What is being tested?
- JZP258
- Type of treatment
- Pill or oral medicine
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 155 participants
- Where
- 43 sitesin 5 countries
- Study dates
- 26 Jun 2023to 10 Mar 2025
- Phase
- Phase 4
- Are there results?
- Yes, posted in the registrySummary in the doctors' view
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 70 years
- All sexes
- No healthy volunteers
- Adult, Older adult
Who may be able to join
- 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.
Who cannot join
- 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.
Trial locations and contacts
43 sites in 5 countries.
43 sites in 5 countries
United States31 sites
Abington Neurological Associates, LTD
Abington, Pennsylvania, 19001
FutureSearch Trials of Neurology
Austin, Texas, 78731
University of Maryland Medical Center
Baltimore, Maryland, 21201
FWD Clinical Research
Boca Raton, Florida, 33486
Meris Clinical Research, LLC
Brandon, Florida, 33511
Intrepid Research, LLC
Cincinnati, Ohio, 45245
University Hospitals Cleveland Medical Center
Cleveland, Ohio, 44106
Bogan Sleep Consultants, LLC
Columbia, South Carolina, 29201
Science 37
Culver City, California, 90230
Ohio Sleep Medicine and Neuroscience
Dublin, Ohio, 43017
M3 Wake Research
Encino, California, 91436
Velocity Clinical Research, Greenville
Greenville, South Carolina, 29615
Henderson Clinical Trials LLC
Henderson, Nevada, 89052
Advanced Respiratory and Sleep Medicine, PLLC
Huntersville, North Carolina, 28078
So Cal Clinical Research
Huntington Beach, California, 92647
Long Beach Research Institute
Lakewood, California, 90805
Sparrow Health System
Lansing, Michigan, 48911
Bryan Medical Center
Lincoln, Nebraska, 68506
University of Louisville
Louisville, Kentucky, 40202
Sleep Practitioners, LLC
Macon, Georgia, 31210
Ocean Wellness Center
Miami, Florida, 33169
Serenity Research Center LLC
Miami, Florida, 33176
Saltzer Medical Group
Nampa, Idaho, 83686
Neurocare, Inc
Newton, Massachusetts, 02459
Florida Pediatric Research Institute, LLC
Orlando, Florida, 32804
OHSU Hospital
Portland, Oregon, 97239
Stanford School of Medicine
Redwood City, California, 94063
Clinical Research of Rock Hill
Rock Hill, South Carolina, 29732
Sleep Therapy & Research Center
San Antonio, Texas, 78229
TriValley Sleep Center
San Ramon, California, 94583
SDS Clinical Trials, Inc.
Santa Ana, California, 92705
Spain4 sites
Hospital Universitari Vall d'Hebron
Barcelona, 08035
Hospital General de Castellon
Castellon, 12004
Hospital Universitario Clinico San Carlos
Madrid, 28040
Hospital Universitario Araba - Sede Santiago
Vitoria-Gasteiz, Alava, 01004
France3 sites
CHU de Grenoble - Hôpital Albert Michallon
Grenoble, Isere, 38043
Hopital Gui de Chauliac
Montpellier, Herault, 34295
CHU Nantes - Hôtel Dieu
Nantes, Loire Atlantique, 44093
Italy3 sites
IRCCS Istituto de Scienze Neurologiche di Bologna (ISNB)
Bologna, 40139
Ospedale San Raffaele (San Raffaele Turro)
Milan, 20127
Azienda Ospedaliera Universitaria Policlinico Tor Vergata
Roma, 00133
Belgium2 sites
Antwerp University Hospital (UZA)
Edegem, 2650
Private Practice RESPISOM Namur
Namur, 5101
About this study
Official title: 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.
- Conditions
- Narcolepsy
- Being tested
- JZP258
- Keywords
- Narcolepsy Type 1, Narcolepsy Type 2, JZP258, Oxybate, Xywav
- Medical subject headings
- Narcolepsy
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
JZP258Drug
Also called Xywav
0.5 g/ml calcium, magnesium, potassium, and sodium oxybates oral solution
| Study group | Role | What they receive |
|---|---|---|
| JZP258 | Experimental | 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. Receives: Drug: JZP258 |
What is being measured
The primary outcome is the main question the study is designed to answer.
Change From Baseline to End of Treatment (EOT) Visit on the 24-hour Average Systolic Blood Pressure (SBP) in mmHg
Measured: Baseline (Screening) and End of Treatment (EOT) Visit, up to 6 weeks
Secondary outcomes (3)
Change From Baseline to EOT Visit on the Daytime Average SBP in mmHg
Measured: 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
Measured: 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
Measured: Baseline (Screening) and End of Treatment (EOT) Visit, up to 6 weeks
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted22 May 2023
- Study start26 Jun 2023
- Primary completion25 Feb 2025
- Study completion10 Mar 2025
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Posted resultsParticipant flow, outcome measures and adverse events reported by the sponsor.
- Publications (1)Papers the sponsor has linked to this study.
- Other trials for NarcolepsyStudies of the same condition, open and under way.
- More trials run by Jazz PharmaceuticalsThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase 4
- Primary purpose
- Treatment
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Enrolment
- 155 participants (actual)
Sponsor and investigators
- Lead sponsor
- Jazz Pharmaceuticals
- Sponsor type
- Industry (pharma, biotech, devices)
- Responsible party
- Sponsor
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT05869773
- Sponsor's protocol ID
- JZP258-406
- Acronym
- XYLO
- Status last verified
- Apr 2026
- First submitted
- 12 May 2023
- Last updated
- 24 Apr 2026
- Results posted
- Yes, on ClinicalTrials.gov
- FDA-regulated drug
- Yes
- FDA-regulated device
- No
- Individual data sharing
- Yes: 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.
Publications
White WB, Kovacs RJ, Alexander JK, Baranak C, Nichols DA, Fuller DS, Dai J, Whalen M, Ajayi A, Hutchinson B, Dauvilliers Y, Somers VK. Effects of High- Versus Low-Sodium Oxybate on Blood Pressure in Patients With Narcolepsy. Hypertension. 2025 Dec;82(12):2162-2171. doi: 10.1161/HYPERTENSIONAHA.125.25730. Epub 2025 Oct 15.
PubMed 41090230
Study at a glance
From the registry record, last updated by the sponsor on 24 Apr 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- An Open-Label, Multicenter Switch Study Evaluating Changes in Blood Pressure in Participants With Narcolepsy Switching From High-Sodium Oxybate to Xywav
- ClinicalTrials.gov ID
- NCT05869773
- Acronym / sponsor ID
- XYLO / JZP258-406
- Conditions
- Narcolepsy
- Keywords
- Narcolepsy Type 1, Narcolepsy Type 2, JZP258, Oxybate, Xywav
- Phase
- Phase 4
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 155 participants (actual)
- Lead sponsor
- Jazz PharmaceuticalsIndustry (pharma, biotech, devices)
- Study start
- 26 Jun 2023 (actual)
- Primary completion
- 25 Feb 2025 (actual)
- Study completion
- 10 Mar 2025 (actual)
- First posted
- 22 May 2023 (actual)
- Results
- Posted 24 Apr 2026
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
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 design
- Primary purpose
- Treatment
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Number of arms
- 1
| Arm | Type | Receives |
|---|---|---|
| JZP258 | Experimental | Drug: JZP258Eligible 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. |
Who may qualify
- Ages
- 18 to 70 years
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (6 listed)
- 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
Key exclusion criteria (4 listed)
- 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.
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| JZP258Also: Xywav0.5 g/ml calcium, magnesium, potassium, and sodium oxybates oral solution | Drug | JZP258 |
Primary outcome
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
3 secondary outcomes
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
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
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
Results and safety
Loading the posted results from ClinicalTrials.gov…
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 24 Apr 2026.
- Posted resultsParticipant flow, baseline, all outcome measures and adverse events.
- Derived from this study: PubMed 41090230White WB, Kovacs RJ, Alexander JK, Baranak C, Nichols DA, Fuller DS, Dai J, Whalen M, Ajayi A, Hutchinson B, Dauvilliers Y, Somers VK. Effects of High- Versus Low-Sodium Oxybate on Blood Pressure in Patients With Narcolepsy. Hypertension. 2025 Dec;82(12):2162-2171. doi: 10.1161/HYPERTENSIONAHA.125.25730. Epub 2025 Oct 15.
- Individual participant dataSharing planned: Yes. 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.
Related trials for Narcolepsy
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A Long-Term Study of ALKS 2680 in Subjects With Narcolepsy and Idiopathic Hypersomnia
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RecruitingPhase 3
A Study Evaluating the Efficacy and Safety of Xywav Expanded Dosing vs Placebo in Participants With Narcolepsy or IH
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RecruitingPhase 2
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RecruitingPhase 3
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
The record lists no contact. Use the official record to reach the sponsor.
43 sites in 5 countries: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 4 study testing JZP258 in people with Narcolepsy, run by Jazz Pharmaceuticals at 43 sites in 5 countries.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 6 inclusion and 4 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: finished, as of the sponsor's last update on 24 Apr 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 43 sites in United States, Spain, France, Italy, Belgium. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this phase mean?
Phase 4 studies take place after a treatment is approved, to learn more about its long-term benefits and risks in everyday use.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
Yes. Results are posted in the registry (first posted 24 Apr 2026). A summary is in the For doctors view, and the full results are on ClinicalTrials.gov.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
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). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
On the ClinicalTrials.gov record for NCT05869773, which also lists 1 linked publication.
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 24 Apr 2026.