The Food and Drug Administration (FDA) has granted Priority Review to the supplemental New Drug Application (sNDA) for XywavTM (calcium, magnesium, potassium, and sodium oxybates; Jazz Pharmaceuticals) oral solution for the treatment of idiopathic hypersomnia in adults.

Xywav is an oxybate product believed to exert its therapeutic effects through GABAB during sleep. It contains the same oxybate concentration as Xyrem (sodium oxybate; Jazz Pharmaceuticals), but with a unique composition of cations resulting in 92% less sodium (approximately 1000 to 1500mg/night).

The sNDA is supported by data from a multicenter, randomized withdrawal, double-blind, placebo-controlled phase 3 study ( NCT03533114) that assessed the efficacy and safety of Xywav in adults with idiopathic hypersomnia. The study included an open-label titration period followed by a randomized withdrawal period, which included 115 patients who received either Xywav or placebo for 2 weeks. 

Findings showed that treatment with Xywav led to clinically meaningful improvements in Epworth Sleepiness Scale (ESS) score during the open-label titration period (primary endpoint; P <.0001). Xywav was also associated with significant improvements in Patient Global Impression of Change (PGIc) (P <.0001) and Idiopathic Hypersomnia Severity Scale (IHSS) (P <.0001) compared with placebo (secondary endpoints). Moreover, Xywav demonstrated clinically meaningful maintenance of efficacy for ESS, PGIc and IHSS during the randomized withdrawal period. 

A Prescription Drug User Fee Act (PDUFA) target date of August 12, 2021 has been set for the application.

Xywav is currently approved for the treatment of cataplexy or excessive daytime sleepiness in patients 7 years of age and older with narcolepsy.


Jazz Pharmaceuticals Announces FDA acceptance and Priority Review of supplemental New Drug Application for Xywav™ (calcium, magnesium, potassium, and sodium oxybates) oral solution in idiopathic hypersomnia. [press release]. Dublin, Ireland: Jazz Pharmaceuticals plc; April 12, 2021.