Topoisomerase I inhibitor
- Prevents topoisomerase-I religation → persistent single-strand breaks stall replication
- Cytotoxic in colorectal and ovarian cancer
- Myelosuppression
- Diarrhea
Drugs with this mechanism (2)
- Irinotecan — Two diarrheas: early cholinergic, late secretory. UGT1A1 matters.
- Topotecan — Topoisomerase-I inhibitor used as salvage chemotherapy; marrow suppression dominates.
Self-check
- Which type of DNA break persists after topoisomerase-I religation is blocked?
Single-strand breaks. - Which GI toxicity accompanies topoisomerase-I inhibition?
Diarrhea.
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