DUET Trial: Low-Sodium Oxybate Significantly Consolidates Nighttime Sleep Architecture in Narcolepsy

New research from the phase 4 DUET study (NCT05875974) demonstrates that low-sodium oxybate (LXB; Xywav; Jazz Pharmaceuticals) significantly improves both objective nighttime sleep architecture and subjective daytime symptoms in patients with narcolepsy type 1 (NT1) and type 2 (NT2).¹ While the pivotal phase 3 trials for LXB focused primarily on daytime outcomes like excessive daytime sleepiness and cataplexy,² this prospective, open-label study provides new insights into the medication's impact on disrupted nighttime sleep, which is a core but often underaddressed symptom of the narcolepsy symptom pentad.¹

Study Design and Patient-Centric Methodology

The DUET study was designed as a patient-centric, multicenter trial to evaluate LXB in a real-world clinical setting. The narcolepsy cohort included 55 enrolled participants, with 34 completing the full 8-day end-of-treatment (EOT) assessment period (NT1, n = 16; NT2, n = 18). Participants underwent an 8-day baseline period off LXB, followed by a 2- to 8-week dose titration and optimization phase and a 2-week stable-dose period.

A key feature of the study was the use of nocturnal polysomnography (PSG) at both baseline and EOT to empirically measure changes in sleep architecture. Effectiveness was further assessed through the Epworth Sleepiness Scale (ESS), the Narcolepsy Severity Scale (NSS), and Patient Global Impression of Severity (PGI-S) and Change (PGI-C).

LXB Significantly Improves Sleep Quality

The study met all of its prespecified primary and secondary end points related to sleep quality and architecture. Objective PSG data revealed significant improvements in the stability of nighttime sleep:

• Deep Sleep (N3) Duration: Participants experienced a least-squares mean (LSM) increase of 45.0 minutes in N3 sleep duration from baseline to EOT (P < .0001).
• Sleep Transitions: The total number of transitions from deeper to lighter sleep stages or wakefulness decreased by an LSM of 13.1 (P < .0001).
• Nocturnal Awakenings: The frequency of nightly awakenings (≥ 2 consecutive wake epochs) was reduced by an LSM of 3.2 (P = .0013).

According to the study, these findings confirm that LXB effectively consolidates sleep and increases the time spent in restorative slow-wave sleep, addressing the sleep fragmentation that characterizes narcolepsy.

Daytime Symptom Relief and Patient Perspectives

Improvements in nighttime sleep were accompanied by a marked reduction in daytime symptoms. The primary end point, the ESS score, showed a significant LSM decrease of 7.7 points (P < .0001). Notably, even though over half of the participants were taking concomitant alerting agents at study entry, their mean baseline ESS scores still indicated severe sleepiness (> 16), which normalized after optimized LXB treatment.

Patient-reported outcomes mirrored these objective findings:

• Overall Severity: On the PGI-S, the proportion of participants reporting their narcolepsy as being moderately severe to extremely severe dropped from 79.4% at baseline to 23.5% at EOT (P < .0001).
• Global Improvement: 93.3% of participants reported that their overall condition was minimally, much, or very much improved on the PGI-C.
• Sleep Quality: The percentage of participants rating their sleep quality as very good or good rose from 15.0% to 70.0%.

Study Limitations: Open-Label, No Control

The DUET study's findings are tempered by several important limitations, most notably its open-label design and lack of a control group. These factors introduce the possibility of expectancy effects, making it difficult to definitively attribute all observed improvements solely to LXB. Furthermore, the primary analyses were restricted to a completer analysis set—participants who reached a stable dosage of up to 9.0 g/night—which may not accurately reflect the experiences of all patients who initiate treatment. Finally, the study's variable treatment duration (ranging from 5 to 12 weeks), caused by individualized titration periods, may have influenced the consistency of the results. To mitigate some of these issues, researchers utilized centralized polysomnography scoring as an objective safeguard.

LXB: Safe, Low-Sodium Narcolepsy Relief

The safety profile of LXB in this phase 4 study was consistent with previous trials. Treatment-emergent adverse events (TEAEs) occurred in 61.8% of participants, with the most common being nausea, dizziness, headache, somnolence, and vomiting. All TEAEs were mild or moderate, and no serious adverse events were reported.

For clinicians, these results underscore the value of LXB in managing the complex symptom profile of narcolepsy, the authors noted. By providing 92% less sodium than traditional sodium oxybate, LXB offers a therapeutic option that addresses both the nighttime sleep instability and daytime hypersomnolence of the disorder while minimizing long-term sodium-related cardiovascular risks. The DUET study reinforces that LXB is an effective treatment across the narcolepsy spectrum, providing meaningful clinical benefits for patients with both NT1 and NT2.

References

1. Nichols DA, Schneider LD, Ruoff CM, et al. Effectiveness and safety of low-sodium oxybate in participants with narcolepsy: primary results from the DUET study. Neurol Ther. Published online April 30, 2026. doi:10.1007/s40120-026-00921-3
2. Grossi G. Low-sodium oxybate reduces excessive sleep time in idiopathic hypersomnia. AJMC^®. February 11, 2026. Accessed May 7, 2026. https://www.ajmc.com/view/low-sodium-oxybate-reduces-excessive-sleep-time-in-idiopathic-hypersomnia