Anti- tumor aktiviteten af topotecan involverer hæmning af topoisomerase- I, et enzym tæt involveret i DNA replikation, da den eliminerer den torsionale belastning, der opstår foran den bevægelige repli - kationsgaffel.
31 The anti-tumour activity of topotecan involves the inhibition of topoisomerase-I, an enzyme intimately involved in DNA replication as it relieves the torsional strain introduced ahead of the moving replication fork.