Irinotecan is an antineoplastic enzyme inhibitor primarily used in the treatment of colorectal cancer. Irinotecan is sold under the brand name Camptosar among others. CAMPTOSAR is a topoisomerase inhibitor indicated for:
• First-line therapy in combination with 5-fluorouracil and leucovorin for
patients with metastatic carcinoma of the colon or rectum.
• Patients with metastatic carcinoma of the colon or rectum whose disease
has recurred or progressed following initial fluorouracil-based therapy.
Irinotecan is a derivative of camptothecin. Camptothecins interact specifically with the enzyme
topoisomerase I, which relieves torsional strain in DNA by inducing reversible single-strand
breaks. Irinotecan and its active metabolite SN-38 bind to the topoisomerase I-DNA complex
and prevent religation of these single-strand breaks. Current research suggests that the
cytotoxicity of irinotecan is due to double-strand DNA damage produced during DNA synthesis
when replication enzymes interact with the ternary complex formed by topoisomerase I, DNA,
and either irinotecan or SN-38. Mammalian cells cannot efficiently repair these double-strand
breaks.
CNS Activity
Originator
Approval Year
Doses
AEs
Sourcing
Sample Use Guides
Usual Adult Dose for Colorectal Cancer
Either as a single agent or in combination with fluorouracil and leucovorin:
125 mg/m2 intravenously over 90 minutes once a week for four doses
or
as a single agent:
350 mg/m2 intravenously over 90 minutes every three weeks
or
in combination with fluorouracil and leucovorin:
180 mg/m2 intravenously over 90 minutes every other week for three doses.
Route of Administration:
Intravenous
The sensitivity to CPT-11 (Irinotecan) alone, of 5 human colon-cancer cell lines, expressed as IC50 values, varied between 2.5 and 6.1uM. The anti-proliferative effectsof the active metabolite SN-38 showed IC50 values between 5.6 and 38 nM, 130 to 570 times lower than those measured for CPT-11 alone. The sensitivity to SN-38 was highest in LS174T and COLO320 cells, intermediate in SW1398 cells and lowest in COLO 205 and WiDr cells.
