Raw research findings for this medication. Mostly single studies, not curated or confirmed robust.
Irinotecan is a topoisomerase I inhibitor: it traps the enzyme that relieves tension in DNA as it is copied, so breaks build up and cancer cells die. It is given by drip for advanced bowel cancer, often in FOLFIRI or FOLFIRINOX, and in a liposomal form for pancreatic cancer. Diarrhoea and low white cell counts are its main side effects. It is sold as Camptosar, among other names.
Irinotecan is turned into SN-38, its active and toxic form, and the liver enzyme UGT1A1 inactivates SN-38. People with two low-activity copies, *28/*28 (the Gilbert's syndrome genotype, about 1 in 10 people of European ancestry) or *6, more common in East Asian populations, clear SN-38 slowly and are more likely to have severe neutropenia and diarrhoea. DPWG has published a guideline on UGT1A1 and irinotecan, and the US label discusses UGT1A1*28. Studies have also looked at SLCO1B1, ABCC2 and ABCG2, with weaker evidence.
Clinical guidelines that name a gene for Irinotecan. They sort people into groups by the gene copies they carry.
US FDA: UGT1A1. *28/*28 · *80+*28/*80+*28 · *6/*6 · *6/*28 · *1/*80+*28 · *1/*6 · *1/*28. 2024.
Every published finding on gene variants and Irinotecan. Upload your DNA file to see which of these rows apply to you.
PharmGKB weighs all studies of a variant and rates how strong the evidence is, from 1A (strongest) to 4.
UGT1A1 UGT1A1*1, UGT1A1*28: Level 1A · replicated. Toxicity: Neutropenia. 33.
UGT1A1 UGT1A1*1, UGT1A1*28: Level 1A · replicated. Dosage. 10.
UGT1A1 UGT1A1*1, UGT1A1*6, UGT1A1*28: Level 1B · replicated. Toxicity: Diarrhea. 24.
UGT1A1 UGT1A1*1, UGT1A1*6: Level 1B · replicated. Toxicity: Neutropenia. 15.
Studies of how quickly the body processes this medication.
Studies of how well it worked in people carrying a variant.
Studies of how much of the drug people needed or tolerated.
Studies of side effects in people carrying a variant.
Study findings and evidence levels: PharmGKB (CC BY-SA 4.0). Guidelines: CPIC and DPWG, as bundled in PharmCAT. Most studies were done mainly in people of European ancestry.
More drugs from the same category
Hycamtin (Topoisomerase Inhibitors)
VePesid (Topoisomerase Inhibitors)
XK469 (Topoisomerase Inhibitors)
Not a prescribing recommendation. This page is educational information about pharmacogenomic research and clinical guidelines - it is not medical or dosing advice, and not a prediction of how any medication will work for you. Never start, stop, or change a medication or dose based on it; talk to your doctor or pharmacist, who can order clinical-grade testing if appropriate.
Content updated September 2026.
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