Irinotecan is an antineoplastic enzyme inhibitor primarily used in the treatment of colorectal cancer. It is a derivative of camptothecin that inhibits the action of topoisomerase i.irinotecan prevents religation of the dna strand by binding to topoisomerase i-dna complex, and causes double-strand dna breakage and cell death. It is a derivative of camptothecin. Irinotecan was approved for the treatment of advanced pancreatic cancer in october, 2015 (irinotecan liposome injection, trade name onivyde).