Sep. 8, 2009 (Business Wire) -- XenoPort, Inc. (Nasdaq:XNPT) announced today preliminary results from a Phase 2 clinical trial that evaluated the safety and tolerability of arbaclofen placarbil (AP), also known as XP19986, when administered without titration to patients with acute back spasms. All doses of AP were safe and generally well tolerated.
This randomized, double-blind, placebo-controlled, Phase 2 clinical trial in patients with acute moderate to severe muscle spasms in the lumbar region was conducted at 17 sites in the United States. Subjects were randomized into one of four treatment arms (placebo, 20 mg BID, 30 mg BID or 40 mg BID administered without titration; 1:1:1:1 ratio) and were treated for ten days, followed by a dose-dependent taper schedule of up to four days. Evaluations of safety, tolerability and efficacy were conducted in those subjects (n=151) who received at least one dose of study medication.
The primary objective of this study was to evaluate the safety and tolerability of AP administered without titration to patients with acute back spasms. AP was safe and generally well tolerated at all dose levels. There were no drug-related serious adverse events. Six subjects in the AP dose groups withdrew from the study due to adverse events (one in each of the 20 mg and 30 mg BID groups and four in the 40 mg BID group). The most common adverse events (reported more frequently in any AP group than in the placebo group) were somnolence, dizziness and nausea. The highest incidence of any adverse event was 19% for somnolence in the 40 mg BID group compared to 12% for the placebo group. Adverse event rates for the 20 mg BID and 30 mg BID groups were comparable to the placebo group, with the exception of dizziness for the 30 mg BID group (14% versus 5% for placebo). All adverse events were rated as mild to moderate in intensity.
Several secondary efficacy measures were assessed, including pain severity score. Efficacy measures in subjects in all treatment groups were highly variable, and no differences between AP doses and placebo on these secondary efficacy measures were observed.
“We are pleased with the safety and tolerability of AP observed in this trial, especially since this was the first study in which we have administered AP without titration,” said Ronald W. Barrett, Ph.D., XenoPort’s chief executive officer. “We believe that this important result could impact the dosing regimen used in future trials evaluating AP for the potential treatment of gastroesophageal reflux disease and spasticity.”
Dr. Barrett continued, “Given the high variability in efficacy measures observed in this trial, we will not be pursuing further development of AP for patients with acute back spasms at this time. We intend to focus on the two indications where we have generated encouraging efficacy and tolerability data in Phase 2 trials.
