XenoPort has reported unsuccessful preliminary top-line results from a Phase IIb clinical trial evaluating arbaclofen placarbil as an adjunctive therapy in patients with gastroesophageal reflux disease.

The study results revealed that none of the arbaclofen placarbil doses showed statistically significant improvements over the placebo in the analysis of the primary endpoint.

Analyses of key secondary endpoints did not demonstrate consistent results when arbaclofen placarbil doses were compared to the placebo.

The randomised, double-blind and placebo-controlled trial enrolled 460 patients who experienced gastroesophageal reflux disease symptoms despite proton pump inhibitor therapy.

The patients were randomised to receive a proton pump inhibitor plus placebo, or a proton pump inhibitor plus one of four arbaclofen placarbil dose regimens (20mg or 40mg dosed once daily, or 20mg or 30 mg, dosed twice daily) for six weeks.

The trial was conducted at 58 sites in the US and Canada.

The primary efficacy endpoint was percent change from baseline in heartburn events per week, with the primary analysis assessing percent change from baseline in heartburn events at week six.