Parts of this work were previously presented at the following conference: Chen Y, Liu L, Nguyen K, Monshouwer M, Weller P, and Fretland A (2009) Determination of inter-system extrapolation factors (ISEFs) for scaling recombinant cytochrome P450 data in early reaction phenotyping. 16th Annual ISSX North American Regional Meeting; 2009 Oct 10–15; Baltimore, MD. International Society for the Study of Xenobiotics, Washington, DC.