Figure 3.

Free irinotecan shows rapid metabolism and elimination in vivo. LC-MS/MS was used to measure the concentration of irinotecan and its metabolites, SN38 and SN38G, in tumors and tissues. High dose (50 mg/kg) and low dose (2 mg/kg) equivalent to that used in thMBs (Figure 2) was delivered intravenously. Free drug was rarely detected after 24 h with only one kidney and one spleen of the three mice in this group showing detectable levels at 72 h using a high-dose of irinotecan. Data from a single injection of irinotecan per time point per mouse are shown except for 72 h where n = 3.