Irinotecan hydrochloride

Irinotecan hydrochloride (CAS No.: 100286-90-6) is a semisynthetic camptothecin derivative and a well-characterized topoisomerase I inhibitor widely employed in biomedical research to investigate DNA damage responses and cell cycle–dependent cytotoxic mechanisms. As a prodrug, it is enzymatically converted by carboxylesterases to the active metabolite SN-38, which exhibits substantially higher potency and exerts its activity by stabilizing the transient cleavable complex formed between topoisomerase I and DNA, thereby preventing religation of single-strand breaks and leading to replication-associated DNA damage and apoptotic cell death. This mechanism confers S-phase specificity, making the compound particularly useful for studying DNA replication stress, checkpoint activation, and apoptosis signaling pathways. In vitro, irinotecan and its active metabolite typically demonstrate inhibitory activity in the nanomolar to low micromolar range depending on the cellular context and enzymatic conversion efficiency. The compound is extensively utilized in cell-based assays and in vivo experimental models to explore tumor biology, including mechanisms of drug resistance, DNA repair pathways, and topoisomerase I–associated genomic instability. Experimental concentrations or dosing regimens vary according to specific study designs and biological systems, supporting its broad applicability in pharmacological profiling and anticancer drug discovery research.