Effectiveness and optimization of low-sodium oxybate in participants with narcolepsy switching from a high-sodium oxybate: data from the SEGUE study.

Abstract

Low-sodium oxybate (LXB; calcium, magnesium, potassium, and sodium oxybates; Xywav) contains the same active moiety as high-sodium oxybates (sodium oxybate [SXB; Xyrem] and fixed-dose sodium oxybate [Lumryz]), with 92% less sodium, and is approved in the US for treatment of cataplexy or excessive daytime sleepiness in patients 7 years of age and older with narcolepsy, and idiopathic hypersomnia in adults. Patients with narcolepsy have increased cardiovascular risk relative to people without narcolepsy. LXB's lower sodium content is recognized by the US FDA in the narcolepsy population as clinically meaningful in reducing cardiovascular morbidity compared with high-sodium oxybates. The Substitution of Equal Grams of Uninterrupted Xyrem to Xywav (SEGUE) study (NCT04794491) examined the transition experience of patients with narcolepsy switching from SXB to LXB. Eligible participants were aged 18 to 80 years with narcolepsy type 1 or 2 on a stable SXB dose/regimen. After 2 weeks, participants transitioned gram-per-gram to LXB for 6 weeks, with opportunity for subsequent titration. Assessments included the Epworth Sleepiness Scale (ESS), Patient Global Impression of Change (PGIc), ease of switching medication scale (EOSMS), and forced preference questionnaire (FPQ). The study enrolled 62 participants at baseline; 60 transitioned to LXB and 54 completed the study. At baseline and end of the LXB intervention/early discontinuation, respectively, mean total doses were 8.0 and 8.0 g/night; mean ESS scores were 9.4 and 8.8. Most participants reported improvement (45%) or no change (48%) in narcolepsy symptoms on the PGIc, reported the transition to LXB was "easy" (easy, extremely easy, not difficult at all; 93%) on the EOSMS, and preferred LXB compared with SXB (79%) on the FPQ, most commonly due to the lower sodium content. Most participants switched from SXB to LXB with minimal modifications of dose/regimen and reported the transition process was easy. Effectiveness of oxybate treatment was maintained on LXB, and most participants preferred LXB to SXB. No new safety or tolerability issues were identified. Registry: ClinicalTrials.gov; Name: An Interventional Safety Switch Study (Segue Study) of XYWAV in Narcolepsy; URL: https://classic.clinicaltrials.gov/ct2/show/NCT04794491; Identifier: NCT04794491.