Camptothecin is a potent DNA enzyme topoisomerase I (topo I) inhibitor with an IC50 and IC70 of 50 nM and 0.225 μM for breast cancer cell line MDA-MB-231.

Topotecan is an inhibitor of topoisomerase I and the IC50 values in cancer cells are less than 6 μM.

Betulinic acid, a pentacyclic triterpene isolated and purified from the herbs of Ziziphus jujuba, selectively induces apoptosis in tumor cells, also is an inhibitor of HIV-1 with EC50 of 1.4 μ M.

Irinotecan HCl inhibits topoisomerase 1 and prevent DNA from unwinding.

SN-38 is an active metabolite of CPT-11 that inhibits DNA topoisomerase I, DNA synthesis and causes frequent DNA single-strand breaks.

Ellagic acid is a potent and cell permeable casein kinase 2 (CK2) inhibitor with Ki of 20 nM, acts as a potent antioxidant and anti-mutagenic.

β-Lapachone is a naturally occurring quinone obtained from the bark of the lapacho tree (Tabebuia avellanedae) with cancer chemopreventive properties and a potent inhibitor of IDO1 (IC50=0.44 μM).

(S)-10-hydroxycamptothecin is an inhibitor of DNA topoisomerase I with antitumor activity.