The authors assessed the impact of severe hepatic impairment on the disposition of fingolimod--a sphingosine-1-phosphate receptor immunomodulator primarily metabolized by CYP4F2--in 6 patients and 6 matched healthy controls who received a single 5-mg oral dose. Compared with healthy controls, severe hepatic-impaired subjects had a doubled area under the concentration time curve (AUC) and 50% prolonged elimination half-life but a similar peak blood concentration. When these data were combined with those from a previous study in mild and moderate hepatic-impaired subjects, there were significant positive correlations between fingolimod AUC versus bilirubin (r = 0.683) and prothrombin time (r = 0.777) and a significant negative correlation versus albumin (r = 0.578), confirming the importance of liver function for fingolimod clearance. For patients with severe hepatic impairment (Child-Pugh class C), a standard first dose of fingolimod could be given followed by a maintenance dose that is reduced by half from the normal maintenance dose.