Camptothecin-d 5 is the deuterium labeled Camptothecin. Camptothecin (CPT), a kind of alkaloid, is a DNA topoisomerase I ( Topo I ) inhibitor with an IC50 of 679 nM. Camptothecin (CPT) exhibits powerful antineoplastic activity against colorectal, breast, lung and ovarian cancers, modulates hypoxia-inducible factor-1α ( HIF-1α ) activity by changing microRNAs (miRNA) expression patterns in human cancer cells.