Genetic variation in UGT1A1typical of Gilbert syndrome is associated with unconjugated hyperbilirubinemia in patients receiving tocilizumab

Tocilizumab, a monoclonal antibody to interleukin-6 receptor, was recently approved for the treatment of moderate-to-severe rheumatoid arthritis. Two patients during clinical development met laboratory, but not clinical, criteria for Hy's law with bilirubin elevations suspected as a result of genetic variation in uridine diphosphoglucose glucuronosyltransferase (UGT1A1) typical of Gilbert syndrome.