Correlation of pharmacokinetics of CPT-11 in FOLFIRI with phenotyping of CYP3A4 and UGT1A1 activity.

e13002 Background: CPT-11 has complex PK and PD; genotyping of UGT1A1 is recommended for higher doses in *28 carriers (Caucasian) and *6 carriers (Asian) because of a higher risk of toxicity. Raltegravir is mainly metabolized to raltegravir glucuronide by UGT1A1. CPT-11 is mainly eliminated by cytochrome P450 isoform 3A (CYP3A)-mediated oxidation and by esterase cleavage to form SN-38, which is further conjugated by uridine-diphosphate glucuronosyltransferase (UGT) isozymes to the inactive SN-38 glucuronide. We prospectively explored the correlation of midazolam and raltegravir PK with CPT-11 clearance (CL) and SN-38 levels respectively and toxicity in patients undergoing chemotherapy with CPT-11. Methods: Twenty-five Asian patients with advanced cancer received CPT-11 as a 2-weekly 90-minute infusion (180 mg/m2) as part of the FOLFIRI regimen. Subjects were administered raltegravir 400 mg orally (as a UGT1A1 probe) and intravenous midazolam 1 mg (as a CYP3A4 probe) one day before the first dose of their ...