Experimental antitumor activity and pharmacokinetics of the camptothecin analog irinotecan (CPT-11) in mice

Anticancer Drugs. 1996 Jun;7(4):437-60. doi: 10.1097/00001813-199606000-00010.


Irinotecan (CPT-11) is a semi-synthetic derivative of camptothecin currently in clinical trials. In vitro, CPT-11 presented preferential cytotoxicity toward some solid tumor cells (mouse colon 38 and pancreas 03; human pancreas MIA PaCa-2) as compared to leukemia cells (L1210), whereas SN-38, a metabolite of CPT-11, was not solid tumor selective. In vivo, schedule of administration studies in P388 leukemia and mammary adenocarcinoma 16/C (MA16/C) showed that CPT-11 was not markedly schedule dependent. In order to determine its spectrum of anticancer activity, CPT-11 was evaluated against a variety of mouse and human tumors. The end points used were total log cell kill (Lck) for solid tumors and increase in life span (% ILS) for leukemia. Intravenous CPT-11 was found highly active against both early and advanced stage pancreatic ductal adenocarcinoma 03 (P03), with 60% long-term survivors and 100% complete regressions, respectively. Other responsive tumors included: colon adenocarcinomas 38 and 51 (both 1.0 Lck); MA16/C (3.4 Lck); MA13/C (1.0 Lck); human Calc18 breast adenocarcinoma (2.8 Lck); Glasgow osteogenic sarcoma (1.8 Lck); Lewis lung carcinoma (1.4 Lck); B16 melanoma (1.4 Lck); P388 leukemia (170% ILS) and L1210 leukemia (64% ILS). Of interest, CPT-11 was active against tumors with acquired resistance to vincristine (P388/Vcr), to doxorubicin (P388/Dox) and to docetaxel (Calc18/TXT). CPT-11 was also found highly active after oral administration in mice bearing P03 and MA16/C tumors. Pharmacokinetic evaluations performed i.v. at the highest non-toxic dosage in mice bearing P03 tumors revealed CPT-11 peak plasma concentrations (Cmax) of 8.9 micrograms/ml and a terminal half-life of 0.6 h. The metabolite SN-38 plasma concentrations presented a Cmax of 1.6 micrograms/ml and a terminal half-life of 7.4 h. Although the CPT-11 tumor levels were similar to the plasma concentrations for early time points, drug levels decreased more slowly in the tumor compared to plasma (half-life, 5.0 h). SN-38 tumor levels reached concentrations in the range of 0.32-0.34 micrograms/g and decayed with a half-life of 6.9 h. No significant difference in plasma or tumor pharmacokinetics of either CPT-11 or SN-38 were noted after one or five daily i.v. injections. Overall, these data show that CPT-11 has good activity in experimental models, when administered both by the i.v. and the oral routes. Compared to humans, a similar schedule of administration independence was observed and similar CPT-11 levels could be reached at efficacious dosages although metabolite SN-38 levels were found higher in mice.

MeSH terms

  • Animals
  • Antibiotics, Antineoplastic / pharmacology
  • Antineoplastic Agents, Phytogenic / blood
  • Antineoplastic Agents, Phytogenic / pharmacokinetics*
  • Antineoplastic Agents, Phytogenic / pharmacology*
  • Camptothecin / analogs & derivatives*
  • Camptothecin / blood
  • Camptothecin / pharmacokinetics
  • Camptothecin / pharmacology
  • Docetaxel
  • Doxorubicin / pharmacology
  • Drug Resistance, Multiple
  • Drug Resistance, Neoplasm
  • Drug Screening Assays, Antitumor
  • Female
  • Humans
  • Irinotecan
  • Leukemia, Experimental / drug therapy*
  • Leukemia, Experimental / metabolism*
  • Male
  • Mice
  • Mice, Inbred Strains
  • Neoplasms, Experimental / drug therapy*
  • Neoplasms, Experimental / metabolism*
  • Paclitaxel / analogs & derivatives
  • Paclitaxel / pharmacology
  • Sensitivity and Specificity
  • Taxoids*
  • Vincristine / pharmacology


  • Antibiotics, Antineoplastic
  • Antineoplastic Agents, Phytogenic
  • Taxoids
  • Docetaxel
  • Vincristine
  • Irinotecan
  • Doxorubicin
  • Paclitaxel
  • Camptothecin