The significantly down-regulated levels of CYP1A2 (and CYP3A4 and UGT1A1) could explain the altered pharmacokinetics of pibrentasvir, whose area under the concentration–time curve (AUC) differed by 26% or less in patients with Child–Pugh class A or B cirrhosis and increased to 2.1-fold for those with class C [47]. This evidence concerns the gene CYP3A4 and Cirrhosis.