Since the FDA approval of Lyrica and Cymbalta for the treatment of fibromyalgia, a number of additional medications are also being tested as potential FM treatments. One of those, sodium oxybate (JZP-6), has shown positive preliminary results in the first of two Phase III clinical trials. The randomized, double-blind, placebo-controlled study achieved its primary endpoints, demonstrating that sodium oxybate significantly decreased pain and fatigue, and improved daily function, in patients with fibromyalgia.
The 14-week study included 548 adult patients with fibromyalgia randomized to one of three treatment arms: sodium oxybate 4.5 g/night, sodium oxybate 6 g/night or placebo. In the top-line results, a significant number of patients treated with sodium oxybate achieved 30 percent or greater improvement in their pain compared to patients treated with placebo. Of those patients receiving sodium oxybate treatment, 46.2 percent of patients on 4.5 g/night and 39.3 percent of patients on 6 g/night reported this level of pain relief, compared with 27.3 percent of patients on placebo. These results were highly statistically significant.
Patients' physical functioning and ability to perform daily tasks, as measured by the Fibromyalgia Impact Questionnaire (FIQ), were significantly different from placebo for the 4.5 g/night dose and approached significance for the 6 g/night dose. Patients receiving sodium oxybate also reported significant improvement in fatigue, another common symptom of fibromyalgia, at both active dosage levels.
Adverse events were similar to those seen in previous experience with sodium oxybate. The most common adverse events, with incidence greater than or equal to 5 percent and at least twice the rate of placebo, were headache, nausea, dizziness, vomiting, diarrhea, anxiety, and sinusitis. Sodium oxybate was generally well tolerated, with the majority of adverse events reported being mild to moderate in nature.
About Sodium Oxybate
Sodium oxybate is currently marketed as Xyrem® and is approved by the FDA for the treatment of excessive daytime sleepiness and cataplexy (the sudden loss of muscle tone) in adult patients with narcolepsy. It is the sodium salt form of gamma-hydroxybutyrate, an endogenous neurotransmitter and metabolite of GABA.
What Comes Next
Only primary efficacy and safety data have been reviewed at this time. Further analyses will be undertaken to examine the full results, including secondary endpoints, in greater detail. The sodium oxybate Phase III clinical trial program also includes a second randomized, double blind, placebo-controlled study, which is continuing at sites in the U.S. and Europe. More than 90% of the subjects have been enrolled in this second Phase III trial.
The sodium oxybate clinical trials are being conducted by Jazz Pharmaceuticals and UCB, a Belgian biopharmaceutical company. Jazz Pharmaceuticals anticipates submitting a New Drug Application for sodium oxybate as a fibromyalgia treatment to the FDA by the end of 2009. UCB anticipates filing in the EU shortly thereafter.
Published On: December 01, 2008