The use of micro-patterned co-cultured hepatocytes for human hepatic clearance predictions has previously been demonstrated using drugs metabolized by cytochrome P450 enzymes. The present study evaluates the in vitro to in vivo extrapolation (IVIVE) performance for UDP-glucuronosyltransferase (UGT) substrates. In vitro intrinsic clearances for 13 drugs mainly cleared by UGTs were determined using HepatoPac and suspended hepatocytes. The in vivo intrinsic clearance was predicted from in vitro intrinsic clearance and compared with weighted mean in vivo intrinsic clearance estimated from several clinical studies. A conventional scaling methodology accounting for protein binding in plasma and incubation medium was used for the IVIVE assuming that only free drug is accessible at the site of metabolism. The in vivo hepatic intrinsic clearance was predicted within threefold error for six and nine out of thirteen drugs using suspended hepatocytes and HepatoPac, respectively. A reduced under-estimation of hepatic intrinsic clearance was observed in the average fold error (AFE) in HepatoPac (AFE, 0.69) compared with the suspended hepatocytes (AFE, 0.37). The current study shows reasonable performance of hepatic clearance prediction of drugs mainly metabolized by UGT enzymes using HepatoPac with a similar under-prediction bias as obtained in the reported IVIVEs for cytochrome P450 substrates. This study provides a validation of the approach for drugs cleared via UGT conjugation mechanisms and discusses potential causes for outlier behavior considering pharmacokinetic or physicochemical properties.
Keywords: Drug metabolism; Hepatocytes; IVIVE; In vitro; UGT.