Low-Sodium Oxybate Improves Idiopathic Hypersomnia Symptoms Long-Term

During the 6-month open-label extension (OLE), the effectiveness and safety of low-sodium oxybate remained consistent and showed improvement as a long-term treatment option for adults with idiopathic hypersomnia, according to study findings published in the Journal of Clinical Sleep Medicine.

For the study, researchers conducted an open-label extension of a phase 3 trial (ClinicalTrials.gov Identifier: NCT03533114) and reported on the long-term safety and efficacy of low-sodium oxybate in patients with idiopathic hypersomnia.

The researchers utilized a phase 3, double-blind, placebo-controlled, randomized withdrawal design with distinct cohorts. Eligible participants aged 18-75 with a primary diagnosis of idiopathic hypersomnia and average nocturnal total sleep time (TST) ≥7 hours were included. Participants who were either taking medications for idiopathic hypersomnia symptoms or were treatment-naive were eligible.

The study consisted of an open-label titration and optimization period (OLT), a single-blind placebo period (SDP), a double-blind randomized withdrawal period (DBRWP), and an OLE period. After completing the DBRWP, participants entered the OLE phase where all received open-label low-sodium oxybate.

The Epworth Sleepiness Scale (ESS), Idiopathic Hypersomnia Severity Scale (IHSS), and Patient Global Impression of Change (PGIc) were conducted during OLE week 2, week 6, week 14, and the end of OLE. A modified version of the Functional Outcomes of Sleep Questionnaire (FOSQ-10) and the Work Productivity and Activity Impairment Questionnaire: Specific Health Problem (WPAI:SHP) were conducted during OLE week 6, week 14, and the end of OLE.

The baseline characteristics of the safety population in the OLE study were comparable to those of the overall study safety population; with the majority of participants being on average, age 41; women (71%); and White (83%).

A total of 106 patients completed DBRWP and continued on to OLE, however 11 participants did not complete OLE due to reasons of: lack of efficacy, protocol deviation, withdrawal, and loss to follow up.

ESS scores showed improvement during the OLE, with a decrease from study baseline (16.3 [2.8]) to OLE week 2 (6.7 [4.7]) and OLE end (5.3 [3.7]).

IHSS total scores also trended downwards, from study baseline (32.6 [7.3]) to OLE week 2 (16.2 [8.9]) and OLE end (14.8 [8.6]). The paired differences from OLE week 2 to OLE end were -1.0 (range: -20 to 7) for ESS (P =.012) and -1.0 (range: -31 to 19) for IHSS (P =.086).

The percentage of participants who reported “very much improved” PGIc ratings increased from 36.7% at OLE week 2 to 53.8% at OLE end.

FOSQ-10 and WPAI:SHP scores showed no significant changes during OLE.

During the study, mild treatment-emergent adverse events (TEAEs) were reported by 21.7% (23/106) of participants, while 25.5% (27/106) experienced TEAEs of moderate severity or less.

Out of 106 participants in OLE, 50 individuals (47.2%) experienced at least 1 treatment-emergent adverse event (TEAE) during OLE. The occurrence of these TEAEs decreased throughout the duration of OLE.

“These findings support the broad utility of LXB [low-sodium oxybate] as a treatment for idiopathic hypersomnia and provide a more comprehensive picture of the impact of long-term LXB treatment in people with idiopathic hypersomnia,” the researchers concluded.

Study limitations included its open-label nature of low-sodium oxybate treatment during the reported period. Additionally, the OLE population may have been biased towards individuals who responded well and tolerated of low-sodium oxybate, as those who had previously experienced lack of effectiveness or intolerable TEAEs may have dropped out earlier.

Disclosures: Multiple study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.

This article originally appeared on Neurology Advisor