New data boost efficacy, safety of lower-sodium oxybate for idiopathic hypersomnia

Lower-sodium oxybate – a new oxybate treatment with 92-percent less sodium than sodium oxybate – continued to demonstrate its potential in improving function, productivity, and sleepiness in individuals with idiopathic hypersomnia, according to data presented at AAN 2022.

The study commenced with a 10–14-week open-label titration and optimization phase, comprising 154 eligible participants aged 18–75 years who were started on lower-sodium oxybate treatment. A 2-week open-label, stable-dose period (SDP) ensued thereafter. Following which, a 2-week, double-blind, randomized withdrawal period ensued, wherein participants were assigned to either placebo or to continue lower-sodium oxybate treatment. A 24-week open-label extension (OLE) phase followed. [AAN 2022, abstract P1.003]

At baseline, mean Functional Outcomes of Sleep Questionnaire (FOSQ-10) score was 11.8, while mean Work Productivity and Activity Impairment: Specific Health Problem (WPAI:SHP) measure scores were 7.4, 55.3, 57.2, and 65.2 for absenteeism, presenteeism, absenteeism + presenteeism, and activity impairment, respectively.

At the end of the SDP, the FOSQ-10 score improved (mean, 16.7), as did the WPAI:SHP measure scores (1.8, 22.1, 23.1, and 26.8, respectively). These scores remained stable through week 24 (mean, 17.3 [FOSQ-10] and 5.0, 20.3, 23.5, and 26.2, respectively [WPAI:SHP]).

“[Our findings demonstrate that lower-sodium oxybate use led to] sustained efficacy on functioning and work productivity in adults with IH throughout the OLE period,” said Dr Richard Bogan from the University of South Carolina School of Medicine, Columbia, South Carolina, US, and colleagues.

Another analysis looked at 115 of the participants to evaluate their progress in the Epworth Sleepiness Scale (ESS), Idiopathic Hypersomnia Severity Scale (IHSS), and Patient Global Impression of Change (PGIc). [AAN 2022, abstract P1.004]

At baseline, the respective mean ESS and IHSS scores were 15.7 and 31.6.

The mean ESS score improved at end of SDP, week 2, and week 24 (6.1, 6.5, and 5.3, respectively), as did the IHSS scores (15.3, 16.0, and 14.7, respectively).

Half of the participants (52 percent) reported improvement in PGIc at week 1 (ie, minimally/much/very much) compared with baseline. By end of SDP, nearly all participants (94 percent) have reported improvement, and this was sustained from weeks 2 through 24 (93 percent for both timepoints).

Treatment-emergent adverse events included headache, nausea, dizziness, anxiety, and vomiting which, as per the investigators, aligned with the safety profile of lower-sodium oxybate in patients with narcolepsy.

Idiopathic hypersomnia is a debilitating neurologic sleep disorder characterized by excessive daytime sleepiness. Prolonged night-time sleep and severe sleep inertia are some of its symptoms.

In August 2021, lower-sodium oxybate has gained the US FDA nod for the treatment of idiopathic hypersomnia and cataplexy in narcolepsy in adults.