UGT1A9 and Hyperbilirubinemia: These observations suggest that nilotinib-associated hyperbilirubinemia is very likely the result of inhibition of UGT1A1 activity, combined with genetic defects in UGT1A1. Although, UGT1A9 is also an enzyme of the glucuronidation pathway that transforms small lipophilic molecules, such as steroids, bilirubin, hormones, and drugs, into water-soluble, excretable metabolites, we are not aware of any reports indicating that nilotinib-induced hyperbilirubinemia is related to the UGT1A9 I399C/C genotype.