A Randomized, Double-blind, Placebo-controlled, Parallel Group, Dose Ranging Study to Assess the Effect of Repeat Doses of GSK962040 on the Pharmacokinetics of L-DOPA in Subjects With Parkinson's Disease Exhibiting Delayed Gastric Emptying

Gastric emptying is the end-result of a complex and carefully regulated series of events which follow the ingestion of a meal, each of which is dependent on the other and subject to neurohormonal control. Motilin is an endogenous peptide, produced mainly in the duodenum, whose physiological action is mediated by motilin receptors located on enteric neurons, peripheral terminals of the vagus, and on the smooth muscle of the gut. Motilin and non-peptide agonists at motilin receptors increases the gastric emptying rate and therefore provide a potential approach to the treatment of a range of clinical conditions in which delayed gastric emptying is thought to be part of the physiopathology and may be contributory to symptoms. Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by degeneration of nigrostriatal dopaminergic neurones. It affects 1.5% of the global population over 65 years of age. Cardinal symptoms comprise bradykinesia, rigidity, resting tremors and postural instability. Gastrointestinal dysfunction, including gastroparesis, is a frequent feature of PD affecting approximately 90% of patients, and is caused by autonomic dysfunction as well as an adverse effect of antiparkinsonian drug therapy. The therapeutic mainstay for PD treatment is the neutral amino acid L-3,4-dihydroxyphenylalanine (L-DOPA), a dopamine prodrug, as it provides the most rapid and effective symptomatic control of motor impairment in PD. The primary determinant of L-DOPA bioavailability is gastric emptying (GE); delays in GE slow delivery of L-DOPA to its proximal small intestinal absorption sites, increasing the extent of presystemic metabolism, and leading to slowed and diminished absorption.