Trial Outcomes & Findings for A Switch Study From High-Sodium Oxybate to Xywav to Evaluate Changes in Blood Pressure in Participants With Narcolepsy (NCT NCT05869773)

NCT ID: NCT05869773

Last Updated: 2026-04-24

Results Overview

Recruitment status

COMPLETED

Study phase

PHASE4

Target enrollment

155 participants

Primary outcome timeframe

Baseline (Screening) and End of Treatment (EOT) Visit, up to 6 weeks

Results posted on

2026-04-24

Participant Flow

A total of 155 participants is in the enrolled analysis set. The enrolled analysis set includes all participants who provided informed consent for this study.

Participant milestones

Participant milestones
Measure	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. Demographics, adverse events and study outcome measures were not analyzed by dose received.
Screening Period STARTED	155
Screening Period COMPLETED	67
Screening Period NOT COMPLETED	88
Treatment Period STARTED	67
Treatment Period COMPLETED	60
Treatment Period NOT COMPLETED	7

Reasons for withdrawal

Reasons for withdrawal
Measure	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. Demographics, adverse events and study outcome measures were not analyzed by dose received.
Screening Period Screen Failure	88
Treatment Period Lost to Follow-up	1
Treatment Period Protocol Violation	4
Treatment Period Withdrawal by Subject	1
Treatment Period Sponsor decision	1

Baseline Characteristics

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

Baseline characteristics by cohort

Baseline characteristics by cohort
Measure	JZP258 n=67 Participants 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. Demographics, adverse events and study outcome measures were not analyzed by dose received.
Age, Categorical <=18 years	0 Participants n=2 Participants
Age, Categorical Between 18 and 65 years	63 Participants n=2 Participants
Age, Categorical >=65 years	4 Participants n=2 Participants
Sex: Female, Male Female	34 Participants n=2 Participants
Sex: Female, Male Male	33 Participants n=2 Participants
Ethnicity (NIH/OMB) Hispanic or Latino	5 Participants n=2 Participants
Ethnicity (NIH/OMB) Not Hispanic or Latino	60 Participants n=2 Participants
Ethnicity (NIH/OMB) Unknown or Not Reported	2 Participants n=2 Participants
Race (NIH/OMB) American Indian or Alaska Native	0 Participants n=2 Participants
Race (NIH/OMB) Asian	1 Participants n=2 Participants
Race (NIH/OMB) Native Hawaiian or Other Pacific Islander	0 Participants n=2 Participants
Race (NIH/OMB) Black or African American	3 Participants n=2 Participants
Race (NIH/OMB) White	57 Participants n=2 Participants
Race (NIH/OMB) More than one race	1 Participants n=2 Participants
Race (NIH/OMB) Unknown or Not Reported	5 Participants n=2 Participants

PRIMARY outcome

Timeframe: Baseline (Screening) and End of Treatment (EOT) Visit, up to 6 weeks

Population: The study protocol defined that if the primary endpoint was met at the prespecified interim analysis, the study endpoints will be evaluated on the interim analysis population. The interim analysis population are the first 43 participants (75%) that have completed the study. Completion of study participation requires completion of the end of trial (EoT) Visit after 6 weeks of study intervention with a 24-hour BP recording at this visit that met the minimal data standards.

Outcome measures

Outcome measures
Measure	JZP258 n=43 Participants 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. Demographics, adverse events and study outcome measures were not analyzed by dose received.
Change From Baseline to End of Treatment (EOT) Visit on the 24-hour Average Systolic Blood Pressure (SBP) in mmHg	-4.14 mmHg Standard Error 1.348

SECONDARY outcome

Timeframe: Baseline (Screening) and End of Treatment (EOT) Visit, up to 6 weeks

Outcome measures

Outcome measures
Measure	JZP258 n=43 Participants 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. Demographics, adverse events and study outcome measures were not analyzed by dose received.
Change From Baseline to EOT Visit on the Daytime Average SBP in mmHg	-5.08 mmHg Standard Error 1.344

SECONDARY outcome

Timeframe: Baseline (Screening) and End of Treatment (EOT) Visit, up to 6 weeks

Outcome measures

Outcome measures
Measure	JZP258 n=43 Participants 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. Demographics, adverse events and study outcome measures were not analyzed by dose received.
Change From Baseline to EOT Visit on the Seated Resting Average SBP in mmHg	-9.16 mmHg Standard Error 1.337

SECONDARY outcome

Timeframe: Baseline (Screening) and End of Treatment (EOT) Visit, up to 6 weeks

Outcome measures

Outcome measures
Measure	JZP258 n=43 Participants 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. Demographics, adverse events and study outcome measures were not analyzed by dose received.
Change From Baseline to EOT Visit on the Nighttime Average SBP in mmHg	-1.95 mmHg Standard Error 1.679

Adverse Events

JZP258-406 Screening Period

Serious events: 0 serious events

Other events: 0 other events

Deaths: 0 deaths

JZP258-406 Treatment Period

Serious events: 1 serious events

Other events: 11 other events

Deaths: 0 deaths

Serious adverse events

Serious adverse events
Measure	JZP258-406 Screening Period n=155 participants at risk Includes all participants who signed the informed consent form throughout the screening period prior to initiation of study intervention	JZP258-406 Treatment Period n=67 participants at risk Includes all participants who received at least 1 dose of study intervention. This period begins after the first dose of study intervention until the last study visit (end of follow up visit)
Surgical and medical procedures Hospitalisation	0.00% 0/155 • Baseline (Screening) up to 11 weeks Adverse Events (AEs) and all-cause mortality were assessed during the screening and treatment periods. During the screening period, non-serious AEs reported were recorded as medical history. During the treatment period, both non-serious and serious AEs were collected. AEs were not analyzed by dose level received.	1.5% 1/67 • Baseline (Screening) up to 11 weeks Adverse Events (AEs) and all-cause mortality were assessed during the screening and treatment periods. During the screening period, non-serious AEs reported were recorded as medical history. During the treatment period, both non-serious and serious AEs were collected. AEs were not analyzed by dose level received.

Other adverse events

Other adverse events
Measure	JZP258-406 Screening Period n=155 participants at risk Includes all participants who signed the informed consent form throughout the screening period prior to initiation of study intervention	JZP258-406 Treatment Period n=67 participants at risk Includes all participants who received at least 1 dose of study intervention. This period begins after the first dose of study intervention until the last study visit (end of follow up visit)
Gastrointestinal disorders Nausea	— 0/0 • Baseline (Screening) up to 11 weeks Adverse Events (AEs) and all-cause mortality were assessed during the screening and treatment periods. During the screening period, non-serious AEs reported were recorded as medical history. During the treatment period, both non-serious and serious AEs were collected. AEs were not analyzed by dose level received.	3.0% 2/67 • Baseline (Screening) up to 11 weeks Adverse Events (AEs) and all-cause mortality were assessed during the screening and treatment periods. During the screening period, non-serious AEs reported were recorded as medical history. During the treatment period, both non-serious and serious AEs were collected. AEs were not analyzed by dose level received.
Gastrointestinal disorders Vomiting	— 0/0 • Baseline (Screening) up to 11 weeks Adverse Events (AEs) and all-cause mortality were assessed during the screening and treatment periods. During the screening period, non-serious AEs reported were recorded as medical history. During the treatment period, both non-serious and serious AEs were collected. AEs were not analyzed by dose level received.	3.0% 2/67 • Baseline (Screening) up to 11 weeks Adverse Events (AEs) and all-cause mortality were assessed during the screening and treatment periods. During the screening period, non-serious AEs reported were recorded as medical history. During the treatment period, both non-serious and serious AEs were collected. AEs were not analyzed by dose level received.
Infections and infestations Upper respiratory tract infection	— 0/0 • Baseline (Screening) up to 11 weeks Adverse Events (AEs) and all-cause mortality were assessed during the screening and treatment periods. During the screening period, non-serious AEs reported were recorded as medical history. During the treatment period, both non-serious and serious AEs were collected. AEs were not analyzed by dose level received.	4.5% 3/67 • Baseline (Screening) up to 11 weeks Adverse Events (AEs) and all-cause mortality were assessed during the screening and treatment periods. During the screening period, non-serious AEs reported were recorded as medical history. During the treatment period, both non-serious and serious AEs were collected. AEs were not analyzed by dose level received.
Infections and infestations Gastroenteritis	— 0/0 • Baseline (Screening) up to 11 weeks Adverse Events (AEs) and all-cause mortality were assessed during the screening and treatment periods. During the screening period, non-serious AEs reported were recorded as medical history. During the treatment period, both non-serious and serious AEs were collected. AEs were not analyzed by dose level received.	3.0% 2/67 • Baseline (Screening) up to 11 weeks Adverse Events (AEs) and all-cause mortality were assessed during the screening and treatment periods. During the screening period, non-serious AEs reported were recorded as medical history. During the treatment period, both non-serious and serious AEs were collected. AEs were not analyzed by dose level received.
Nervous system disorders Dysgeusia	— 0/0 • Baseline (Screening) up to 11 weeks Adverse Events (AEs) and all-cause mortality were assessed during the screening and treatment periods. During the screening period, non-serious AEs reported were recorded as medical history. During the treatment period, both non-serious and serious AEs were collected. AEs were not analyzed by dose level received.	3.0% 2/67 • Baseline (Screening) up to 11 weeks Adverse Events (AEs) and all-cause mortality were assessed during the screening and treatment periods. During the screening period, non-serious AEs reported were recorded as medical history. During the treatment period, both non-serious and serious AEs were collected. AEs were not analyzed by dose level received.

Additional Information

Clinical Trial Disclosure & Transparency

Jazz Pharmaceuticals Inc.

Phone: 215-832-3750

Email: [email protected]

Results disclosure agreements

Principal investigator is a sponsor employee
Publication restrictions are in place