An Open-label, Non-randomized [11C]Carfentanil PET Study in Healthy Male Subjects to Investigate Brain Mu-opioid Receptor Occupancy, Pharmacokinetics, and Pharmacodynamics of Single Oral Doses of GSK1521498 and Naltrexone.

The purpose of this study is to determine whether GSK1521498 attaches to sites in the brain called mu-opioid receptors that are involved in the liking reactions to palatable high fat and high sugar foods. We hope that blocking these receptors may modify certain behaviours that may lead to obesity.