XenoPort announced preliminary results from a Phase 2b clinical trial of arbaclofen placarbil (AP) as adjunctive therapy in patients with gastroesophageal reflux disease (GERD) who do not experience complete relief of GERD symptoms while being treated with a proton pump inhibitor (PPI). The trial, a multicenter, randomized, double-blind, placebo-controlled study, was designed to assess the efficacy and safety of AP as adjunctive therapy to PPIs. The trial demonstrated that AP doses did not show statistically significant improvements over placebo in the analysis of the primary endpoint. Analyses of key secondary endpoints did not yield consistent results when AP doses were compared with placebo.

Arbaclofen placarbil is a Transported Prodrug of R-baclofen that is designed to engage natural nutrient transport mechanisms found on intestinal cell membranes, thereby gaining efficient entrance into the bloodstream. AP is then rapidly converted by high-capacity enzymes to R-baclofen and natural substances that have well-studied, favorable safety characteristics. R-baclofen is an agonist of a target known as the gamma amino-butyric acid(B), or GABA(B), receptor. Racemic baclofen (a mixture of R and S isomers) has been approved for the treatment of spasticity and has been shown in clinical studies to have efficacy in a number of other therapeutic indications, including GERD.

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