30,31 In subjects with persistent heartburn despite PPI treatment,

RAD001 doses of up to 20 mg trice daily have been used.31 In addition to its effect on TLESR rate, baclofen appears to be also effective in attenuating pain-associated responses using an experimental rodent model.32 This effect, which appears to be mediated by central mechanisms, could be also used in treating refractory GERD patients, where esophageal hypersensitivity is the leading underlying mechanism. Because the drug crosses the blood–brain barrier, a variety of central nervous system (CNS)-related side-effects have been reported. They primarily include somnolence, confusion, dizziness, lightheadedness, drowsiness, weakness, and trembling. The side-effects are likely an important limiting factor in the routine usage of baclofen in clinical practice.

Arbaclofen placarbil (also known as XP19986) is a novel transported pro-drug of the pharmacologically active R-isomer of baclofen. The drug is currently in clinical development for the treatment of refractory GERD. Arbaclofen placarbil was designed to be efficiently http://www.selleckchem.com/products/avelestat-azd9668.html absorbed in the gastrointestinal tract and rapidly metabolized to release R-baclofen after absorption. Unlike baclofen, arbaclofen placarbil is well absorbed from the colon, allowing the drug to be delivered in a sustained release formulation that may allow less frequent dosing and thus reduced fluctuations in plasma exposure. This in turn may lead to potentially improved efficacy through a combination of greater duration of action, subject’s convenience, and better safety profile compared with baclofen.33,34 A recent study demonstrated that arbaclofen significantly reduced the total number of reflux episodes over 12 h in 44 patients with GERD.34 The most efficacious dose of arbaclofen (60 mg) significantly reduced acid reflux episodes by 35% and heartburn

episodes associated with reflux by 49%. Arbaclofen had a favorable 3-mercaptopyruvate sulfurtransferase tolerability and safety profile across the evaluated doses with no significant difference compared with placebo. Recently, the makers of arbaclofen placarbil halted further development due to lack of clinical efficacy in a phase 2B trial. Lesogaberan, a new GABAB agonist, with a better CNS safety profile was developed in order to overcome the side-effects of baclofen. The physiological effects of lesogaberan were evaluated in a small group of patients with persistent GERD-related symptoms despite PPI therapy.35 In this placebo-controlled, cross-over study, lesogaberan significantly decreased the rate of TLESRs, increased basal Lower Esophageal Sphincter (LES) pressure, decreased esophageal acid exposure and decreased the number of postprandial reflux episodes. Furthermore, a decrease in the proximal extent of gastroesophageal reflux events was also demonstrated. However, there was no difference in the number of reflux symptom episodes between the two arms of the study.