This is a phase I study of GBR 900 in healthy volunteers. The purposes of this study are to look at safety, how well the study drug is tolerated, how much of the study drug gets into the blood stream, and how long it takes the body to get rid of it when given to humans. Information about any side effects that may occur will also be collected. Each participant will remain in the study for approximately 3.5 months. This study is for research purposes only and is not intended to treat any medical condition.