The purpose of this study is to compare the pharmacokinetics (PK) of preladenant after administration of a single 5 mg oral dose of preladenant in participants with hepatic impairment and healthy volunteers. Part 1 of this study compares healthy volunteers with participants with mild hepatic impairment. Part 2 compares healthy volunteers with participants with moderate hepatic impairment. Healthy volunteers in each part of this study are to be matched with participants with hepatic impairment by race, age, gender, and body mass index (BMI). The primary hypotheses are that in participants with mild or moderate HI, the area under the concentration-time curve from time 0 extrapolated to time of the last quantifiable concentration (AUC0-t) of preladenant is similar to that observed in matched healthy volunteers, so that the mean ratio of hepatic impaired/healthy is contained within the interval [0.50, 2.00].