A Phase 4 interventional study of JZP258 (XYWAV) in Idiopathic Hypersomnia and Narcolepsy, sponsored by Jazz Pharmaceuticals. Completed at 32 sites in 2 countries. Open to participants aged 18 Years to 75 Years. Per ClinicalTrials.gov, last updated 2026-08-27.
Sponsored by Jazz Pharmaceuticals · Phase 4, Interventional, and Treatment
This study will assess the safety and efficacy of JZP258 (XYWAV) on sleepiness, polysomnography, and functional outcomes in patients with idiopathic hypersomnia (IH) or narcolepsy.
This prospective, multicenter, single-arm, open-label interventional study will assess the safety and efficacy of JZP258 on sleepiness, polysomnography measurements (eg, sleep stage transitions, sleep patterns, and sleep quality), daytime and nighttime symptoms, pharmacokinetics (in narcolepsy), and patient-reported outcomes that include subjective sleep quality and quality of life in patients with IH or narcolepsy.
52 studies on the registry are indexed under Idiopathic Hypersomnia; 23 are open to participants now.
This study's enrollment of 199 is above the median of 82 across 40 interventional studies indexed under Idiopathic Hypersomnia.
Browse Idiopathic Hypersomnia studies →Jazz Pharmaceuticals is the lead sponsor of 173 studies on the registry; 18 are open to participants now.
Of its 42 completed or terminated interventional studies of FDA-regulated products, 32 (76%) have results posted.
Counted across the registry records on this site, refreshed daily.
Key Inclusion Criteria:
Additional Inclusion Criteria for Participants in the Exploratory Narcolepsy >9-Gram Cohort
Key Exclusion Criteria:
Has recently taken (ie, within 1 month prior to screening), is taking, or plans to take any of the following:
Additional Exclusion Criterion for Participants in the Exploratory Narcolepsy >9-Gram Cohort
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
The American Psychiatric Association’s manual of mental health diagnoses. DSM-5 (2013, revised as DSM-5-TR in 2022) replaced DSM-IV, and some studies still name the older edition. “Meets DSM criteria for …” means diagnosed by that edition’s diagnostic criteria, usually by a clinician in an interview.
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
A planned gap after a treatment, so that its effects can lessen before the study treatment or a study assessment. Ask the study team and the doctor who prescribed it before changing any medicine.
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
DSM diagnostic criteria
The American Psychiatric Association’s manual of mental health diagnoses. DSM-5 (2013, revised as DSM-5-TR in 2022) replaced DSM-IV, and some studies still name the older edition. “Meets DSM criteria for …” means diagnosed by that edition’s diagnostic criteria, usually by a clinician in an interview.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Clinically significant
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Washout period
A planned gap after a treatment, so that its effects can lessen before the study treatment or a study assessment. Ask the study team and the doctor who prescribed it before changing any medicine.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Contraindication
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Participants will self-administer an oral dose of JZP258 (XYWAV) as per label and titrate to an optimal dosage for each participant.
Drug: JZP258 (XYWAV)
Narcolepsy Cohort: Initiate dosage per XYWAV label and titrate to effect. IH Cohort: Initiate dosage per XYWAV label and titrate to effect. Exploratory Narcolepsy \>9-Gram Cohort: XYWAV titrated to a dosage of \>9 to 12 grams.
Change From Baseline in Epworth Sleepiness Scale (ESS) Total Score in Participants With IH and Narcolepsy Treated With XYWAV
The ESS total score (the sum of 8 item scores, each 0 to 3) can range from 0 to 24. Higher ESS total scores are associated with higher sleep propensity in daily life, also referred to as "daytime sleepiness."
Time frame: Baseline up to End of Treatment (approximately 10-36 weeks)
Change From Baseline in Idiopathic Hypersomnia Severity Scale (IHSS) Total Score in Participants With IH Treated With XYWAV
The IHSS is a 14-item self-reported instrument that assesses the severity and functional consequences of IH symptoms. Questions capture symptoms of excessive sleepiness, sleep inertia, and long sleep duration. IHSS total scores range from 0 to 50 with higher score indicating worse clinical outcome.
Time frame: Baseline up to End of Treatment (approximately 10-21 weeks)
Change From Baseline in Number of Stage Shifts of Sleep in Participants With Narcolepsy Treated With XYWAV
Stage shifts of sleep are defined as the count of transitions of bouts of sleep from deeper to lighter stages of sleep/wake (ie from N3/N2/N1/REM to wake and from N3/N2/REM to N1).
Time frame: Baseline up to End of Treatment (approximately 10-36 weeks)
Change From Baseline in Duration of Sleep Stages in Participants With Narcolepsy Treated With XYWAV
Duration of sleep stages is measured in minutes (ie N1/N2/N3/REM) and is recorded from sleep onset to awakening during the nocturnal polysomnograph.
Time frame: Baseline up to End of Treatment (approximately 10-36 weeks)
Change From Baseline in Number of Nocturnal Awakenings and Nocturnal Arousals in Participants With Narcolepsy Treated With XYWAV
Time frame: Baseline up to End of Treatment (approximately 10-36 weeks)
Change From Baseline in Percentage of Sleep Stages in Participants With Narcolepsy Treated With XYWAV
The percentage of sleep stages is measured as minutes of each sleep stage (N3/N2/N1/REM) per hour of sleep time from sleep onset to awakening in the nocturnal polysomnograph.
Time frame: Baseline up to End of Treatment (approximately 10-36 weeks)
Patient Global Impression of Change (PGI-C) in Participants With IH and Narcolepsy Treated With XYWAV (Overall, Sleep Inertia, and Fatigue)
The PGI-C is a single-item 7-point, Likert-type scale for rating change in disease or symptom severity. Responses for each question ranged from 1 (very much improved) to 7 (very much worse) relative to baseline. Participants rated the change from baseline in their overall (IH or narcolepsy) symptoms, sleep inertia (difficulty waking in the morning), and fatigue (extreme tiredness resulting from mental or physical exertion).
Time frame: End of Treatment (approximately 10-36 weeks)
Level of Rested or Refreshed Upon Awakening in Participants With IH and Narcolepsy Treated With XYWAV (Sleep Diary)
The participant was asked "How rested or refreshed did you feel when you woke up for the day?"
Time frame: Baseline up to End of Treatment (approximately 10-36 weeks)
Patient Global Impression of Severity (PGI-S) Score in Participants With IH and Narcolepsy Treated With XYWAV (Overall, Sleep Inertia, and Fatigue)
The PGI-S is a single-item, 7-point, Likert-type scale for rating disease or symptom severity. Responses ranged from 0 (not present) to 7 (extremely severe). Participants rated the severity of their overall (IH or narcolepsy) symptoms, sleep inertia, and fatigue. Higher scores indicate worse clinical outcome.
Time frame: Baseline up to End of Treatment (approximately 10-36 weeks)
Pharmacokinetic Parameter Maximum Plasma Concentration (Cmax) In a Subset of Participants With Narcolepsy Treated With XYWAV
Blood samples were processed to obtain plasma samples and then analyzed for oxybate concentrations using a validated bioanalytical method.
Time frame: PK: Predose, 0.5 hour, 0.75 hour, 1 hour, 1.5 hour post-first dose and post-second dose, 6 hour post-first dose, 8 hour post-first dose
Pharmacokinetic Parameter Area Under the Concentration-Time Curve From Time 0 to Infinity (AUC0-inf) In a Subset of Participants With Narcolepsy Treated With XYWAV
Blood samples were processed to obtain plasma samples and then analyzed for oxybate concentrations using a validated bioanalytical method.
Time frame: PK: Predose, 0.5 hour, 0.75 hour, 1 hour, 1.5 hour post-first dose and post-second dose, 6 hour post-first dose, 8 hour post-first dose
The Enrolled Analysis Set included n=66 Idiopathic Hypersomnia; n=68 Narcolepsy; n=65 \> 9-g Narcolepsy. Each cohort has a cohort-specific ICF and a unique set of protocol specified assessments/procedures. Participants in the \>9-g Narcolepsy cohort were either already taking 9 g/night of Xywav at screening or had titrated to 9 g of Xywav while in the Narcolepsy cohort, discontinued from this cohort, and signed a new ICF to begin the \>9-g Narcolepsy cohort (referred to as "transfer participants").
| Milestone | Idiopathic Hypersomnia (IH) | Narcolepsy | Exploratory > 9-g Narcolepsy |
|---|---|---|---|
| Started | 66 | 68 | 65 |
| Completed | 46 | 55 | 51 |
| Not completed | 20 | 13 | 14 |
| Withdrew: Screen failures | 20 | 13 | 14 |
| Milestone | Idiopathic Hypersomnia (IH) | Narcolepsy | Exploratory > 9-g Narcolepsy |
|---|---|---|---|
| Started | 46 | 55 | 48 |
| Transferred from narcolepsy cohort and received >9g treatment | 0 | 0 | 11 |
| Completed | 40 | 34 | 44 |
| Not completed | 6 | 21 | 4 |
| Withdrew: Adverse event | 1 | 2 | 2 |
| Withdrew: Physician decision | 2 | 0 | 0 |
| Withdrew: Protocol deviation | 1 | 1 | 0 |
| Withdrew: Withdrawal by subject | 2 | 3 | 1 |
| Withdrew: Pregnancy | 0 | 1 | 0 |
| Withdrew: Sponsor request | 0 | 1 | 0 |
| Withdrew: Noncompliance with study schedule | 0 | 0 | 1 |
| Withdrew: Transferred to > 9-g narcolepsy cohort | 0 | 13 | 0 |
The ESS total score (the sum of 8 item scores, each 0 to 3) can range from 0 to 24. Higher ESS total scores are associated with higher sleep propensity in daily life, also referred to as "daytime sleepiness."
| score on a scale | Idiopathic Hypersomnia (IH) | Narcolepsy |
|---|---|---|
| Change From Baseline in Epworth Sleepiness Scale (ESS) Total Score in Participants With IH and Narcolepsy Treated With XYWAV | -8.38 ± 0.695 | -7.68 ± 0.931 |
The IHSS is a 14-item self-reported instrument that assesses the severity and functional consequences of IH symptoms. Questions capture symptoms of excessive sleepiness, sleep inertia, and long sleep duration. IHSS total scores range from 0 to 50 with higher score indicating worse clinical outcome.
| score on a scale | Idiopathic Hypersomnia (IH) |
|---|---|
| Change From Baseline in Idiopathic Hypersomnia Severity Scale (IHSS) Total Score in Participants With IH Treated With XYWAV | -15.53 ± 1.490 |
Stage shifts of sleep are defined as the count of transitions of bouts of sleep from deeper to lighter stages of sleep/wake (ie from N3/N2/N1/REM to wake and from N3/N2/REM to N1).
| stage shifts | Narcolepsy |
|---|---|
| Change From Baseline in Number of Stage Shifts of Sleep in Participants With Narcolepsy Treated With XYWAV | -13.06 ± 2.908 |
Duration of sleep stages is measured in minutes (ie N1/N2/N3/REM) and is recorded from sleep onset to awakening during the nocturnal polysomnograph.
| minutes | Narcolepsy |
|---|---|
| Stage N1 Sleep Duration: Full Night, Visit 4 (End of Treatment) | -8.12 ± 3.303 |
| Stage N2 Sleep Duration: Full Night, Visit 4 (End of Treatment) | 1.5 ± 12.343 |
| Stage N3 Sleep Duration: Full Night, Visit 4 (End of Treatment) | 45.01 ± 8.822 |
| Stage REM Sleep Duration: Full Night, Visit 4 (End of Treatment) | -39.18 ± 5.716 |
| awakenings/arousals | Narcolepsy |
|---|---|
| Number of awakenings: Full Night, Visit 4 (End of Treatment) | -3.18 ± 0.903 |
| Total number of all arousals: Full Night, Visit 4 (End of Treatment | -23.88 ± 7.564 |
The percentage of sleep stages is measured as minutes of each sleep stage (N3/N2/N1/REM) per hour of sleep time from sleep onset to awakening in the nocturnal polysomnograph.
| percentage of sleep stages | Narcolepsy |
|---|---|
| Stage N1 Sleep/Total Sleep Time: Full Night, Visit 4 (End of Treatment) | -2.18 ± 0.696 |
| Stage N2 Sleep/Total Sleep Time: Full Night, Visit 4 (End of Treatment) | 0.03 ± 1.923 |
| Stage N3 Sleep/Total Sleep Time: Full Night, Visit 4 (End of Treatment) | 10.28 ± 1.890 |
| Stage REM Sleep/Total Sleep Time: Full Night, Visit 4 (End of Treatment) | -8.13 ± 1.242 |
The PGI-C is a single-item 7-point, Likert-type scale for rating change in disease or symptom severity. Responses for each question ranged from 1 (very much improved) to 7 (very much worse) relative to baseline. Participants rated the change from baseline in their overall (IH or narcolepsy) symptoms, sleep inertia (difficulty waking in the morning), and fatigue (extreme tiredness resulting from mental or physical exertion).
| Participants | Idiopathic Hypersomnia (IH) | Narcolepsy |
|---|---|---|
| Very much improved | 8 | 4 |
| Much improved | 18 | 19 |
| Minimally improved | 9 | 5 |
| No change | 1 | 2 |
| Minimally worse | 1 | 0 |
| Much worse | 0 | 0 |
| Very much worse | 0 | 0 |
The participant was asked "How rested or refreshed did you feel when you woke up for the day?"
| Participants | Idiopathic Hypersomnia (IH) | Narcolepsy |
|---|---|---|
| Baseline, Sleep Quality Very poor | 4 | 3 |
| Baseline, Sleep Quality Poor | 12 | 14 |
| Baseline, Sleep Quality Fair | 13 | 10 |
| Baseline, Sleep Quality Good | 7 | 5 |
| Baseline, Sleep Quality Very Good | 0 | 0 |
| Visit 4 End of Treatment, Sleep Quality Very poor | 0 | 0 |
| Visit 4 End of Treatment, Sleep Quality Poor | 2 | 0 |
| Visit 4 End of Treatment, Sleep Quality Fair | 11 | 6 |
| Visit 4 End of Treatment, Sleep Quality Good | 12 | 11 |
| Visit 4 End of Treatment, Sleep Quality Very Good | 5 | 3 |
| Baseline, Not at all rested | 11 | 4 |
| Baseline, Slightly rested | 17 | 13 |
| Baseline, Somewhat rested | 6 | 11 |
| Baseline, Well rested | 2 | 4 |
| Baseline, Very well rested | 0 | 0 |
| Visit 4 End of Treatment, Not at all rested | 6 | 0 |
| Visit 4 End of Treatment, Slightly rested | 2 | 2 |
| Visit 4 End of Treatment, Somewhat rested | 12 | 7 |
| Visit 4 End of Treatment, Well rested | 8 | 9 |
| Visit 4 End of Treatment, Very well rested | 2 | 2 |
The PGI-S is a single-item, 7-point, Likert-type scale for rating disease or symptom severity. Responses ranged from 0 (not present) to 7 (extremely severe). Participants rated the severity of their overall (IH or narcolepsy) symptoms, sleep inertia, and fatigue. Higher scores indicate worse clinical outcome.
| score on a scale | Idiopathic Hypersomnia (IH) | Narcolepsy |
|---|---|---|
| Baseline | 5.3 ± 0.92 | 5.4 ± 1.07 |
| Visit 4, End of Treatment | 3.8 ± 1.33 | 3.6 ± 1.40 |
Blood samples were processed to obtain plasma samples and then analyzed for oxybate concentrations using a validated bioanalytical method.
| ug/mL | Narcolepsy |
|---|---|
| Pharmacokinetic Parameter Maximum Plasma Concentration (Cmax) In a Subset of Participants With Narcolepsy Treated With XYWAV | 107.61 ± 1.534 |
Blood samples were processed to obtain plasma samples and then analyzed for oxybate concentrations using a validated bioanalytical method.
| h*µg/mL | Narcolepsy |
|---|---|
| Pharmacokinetic Parameter Area Under the Concentration-Time Curve From Time 0 to Infinity (AUC0-inf) In a Subset of Participants With Narcolepsy Treated With XYWAV | 474.00 ± NA |
Collected over Adverse events were collected from Screening up to Safety Follow Up visit, approximately 14 weeks.. Non-serious events are listed at a 5% frequency threshold.
| Group | Deaths | Serious | Other |
|---|---|---|---|
| Idiopathic Hypersomnia (IH) | 0/46 (0%) | 1/46 (2.2%) | 34/46 (73.9%) |
| Narcolepsy | 0/55 (0%) | 0/55 (0%) | 34/55 (61.8%) |
| > 9-g Narcolepsy | 0/48 (0%) | 1/48 (2.1%) | 36/48 (75%) |
| Event | Idiopathic Hypersomnia (IH) | Narcolepsy | > 9-g Narcolepsy |
|---|---|---|---|
| HypoxiaRespiratory, thoracic and mediastinal disorders | 1/46 | 0/55 | 0/48 |
| SyncopeNervous system disorders | 0/46 | 0/55 | 1/48 |
| Event | Idiopathic Hypersomnia (IH) | Narcolepsy | > 9-g Narcolepsy |
|---|---|---|---|
| NauseaGastrointestinal disorders | 9/46 | 13/55 | 6/48 |
| DizzinessNervous system disorders | 8/46 | 8/55 | 0/48 |
| HeadacheNervous system disorders | 8/46 | 7/55 | 5/48 |
| VomitingGastrointestinal disorders | 5/46 | 6/55 | 6/48 |
| SomnolenceNervous system disorders | 3/46 | 6/55 | 4/48 |
| Middle insomniaPsychiatric disorders | 4/46 | 2/55 | 0/48 |
| EnuresisPsychiatric disorders | 3/46 | 3/55 | 4/48 |
| AnxietyPsychiatric disorders | 3/46 | 4/55 | 2/48 |
| Nasal congestionRespiratory, thoracic and mediastinal disorders | 2/46 | 4/55 | 2/48 |
| Oropharyngeal painRespiratory, thoracic and mediastinal disorders | 0/46 | 4/55 | 1/48 |
Baseline and demographic characteristics were assessed in the Safety Analysis Set.
| Age, Continuous(years) | Idiopathic Hypersomnia (IH) | Narcolepsy | Exploratory > 9-g Narcolepsy | Total |
|---|---|---|---|---|
| IH and Narcolepsy cohorts | 38.1 ± 11.77 | 33.4 ± 12.87 | — | 35.6 ± 12.5 |
| Exploratory >9-g Narcolepsy cohort | — | — | 39.2 ± 10.92 | 39.2 ± 10.92 |
| Sex/Gender, Customized(Participants) | Idiopathic Hypersomnia (IH) | Narcolepsy | Exploratory > 9-g Narcolepsy | Total |
|---|---|---|---|---|
| IH and Narcolepsy cohorts — Male (at birth) | 9 | 15 | — | 24 |
| IH and Narcolepsy cohorts — Female (at birth) | 37 | 40 | — | 77 |
| Exploratory >9-g Narcolepsy cohort — Male (at birth) | — | — | 18 | 18 |
| Exploratory >9-g Narcolepsy cohort — Female (at birth) | — | — | 30 | 30 |
| Race/Ethnicity, Customized(Participants) | Idiopathic Hypersomnia (IH) | Narcolepsy | Exploratory > 9-g Narcolepsy | Total |
|---|---|---|---|---|
| IH and Narcolepsy cohorts — Asian | 2 | 2 | — | 4 |
| IH and Narcolepsy cohorts — Black or African American | 3 | 7 | — | 10 |
| IH and Narcolepsy cohorts — Native Hawaiian or Other Pacific Islander | 1 | 0 | — | 1 |
| IH and Narcolepsy cohorts — White | 39 | 44 | — | 83 |
| IH and Narcolepsy cohorts — Multiple | 1 | 1 | — | 2 |
| IH and Narcolepsy cohorts — Unknown | 0 | 1 | — | 1 |
| Exploratory >9-g Narcolepsy cohort — Asian | — | — | 1 | 1 |
| Exploratory >9-g Narcolepsy cohort — Black or African American | — | — | 7 | 7 |
| Exploratory >9-g Narcolepsy cohort — Native Hawaiian or Other Pacific Islander | — | — | 0 | 0 |
| Exploratory >9-g Narcolepsy cohort — White | — | — | 37 | 37 |
| Exploratory >9-g Narcolepsy cohort — Multiple | — | — | 1 | 1 |
| Exploratory >9-g Narcolepsy cohort — Unknown | — | — | 2 | 2 |
PDFs hosted by the registry, ClinicalTrials.gov.
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Studies of the drug tested here: JZP258