Irinotecan is an antineoplastic enzyme inhibitor primarily used in the treatment of colorectal cancer. Irinotecan is sold under the brand name Camptosar among others. CAMPTOSAR is a topoisomerase inhibitor indicated for: • First-line therapy in combination with 5-fluorouracil and leucovorin for patients with metastatic carcinoma of the colon or rectum. • Patients with metastatic carcinoma of the colon or rectum whose disease has recurred or progressed following initial fluorouracil-based therapy. Irinotecan is a derivative of camptothecin. Camptothecins interact specifically with the enzyme topoisomerase I, which relieves torsional strain in DNA by inducing reversible single-strand breaks. Irinotecan and its active metabolite SN-38 bind to the topoisomerase I-DNA complex and prevent religation of these single-strand breaks. Current research suggests that the cytotoxicity of irinotecan is due to double-strand DNA damage produced during DNA synthesis when replication enzymes interact with the ternary complex formed by topoisomerase I, DNA, and either irinotecan or SN-38. Mammalian cells cannot efficiently repair these double-strand breaks.

10-Hydroxycamptothecin (10-HCPT), an indole alkaloid isolated from a Chinese tree, Camptotheca acuminate, inhibits the activity of topoisomerase I and has a broad spectrum of anticancer activity in vitro and in vivo. However, its use has been limited due to its water-insolubility and toxicity with i.v. administration. Prolonged elimination of 10-HCPT in vivo may have a significant impact on its therapeutic effects. 10-HCPT is metabolized to its carboxylate form and glucuronides.It was investigated that relatively low dose of 10-HCPT is able to inhibit the growth of colon cancer, facilitating the development of a new protocol of human trials with this anticancer drug.

Mureletecan is a water-soluble prodrug, consisting of camptothecin covalently linked to polymeric backbone methacryloylglycynamide, with potential antineoplastic activity. After entering tumor cells, the active moiety camptothecin is slowly released from mureletecan via hydrolysis of the ester linkage. Camptothecin, the active moiety, is an alkaloid isolatable from the Chinese tree Camptotheca acuminata. Camptothecin itself suffers from poor solubility, which is why it is often investigated with a solubilizing conjugate; such as in Mureletecan. Camptothecin binds to and stabilizes the topoisomerase I-DNA covalent complex producing potentially lethal double-stranded DNA breaks when encountered by DNA replication machinery. Camptothecin has also been shown to inhibit HIF1a. Camptothecin has been investigated with a number of solubilizing conjugates as a potential treatment in various forms of cancer.

Tenifatecan (also known as SN2310 or tocopherol succinate-SN38), camptothecin, is an injectable emulsion composed of vitamin E, a succinate derivative, as well as 7-ethyl-10-hydroxycamptothecin (SN-38), the active metabolite of irinotecan. It is known that SN-38 binds to and inhibits topoisomerase I by stabilizing the cleavable complex between topoisomerase I and DNA, resulting in DNA breaks, inhibition of DNA replication, and apoptosis. Tenifatecan successfully completed phase I clinical trial in patients with advanced solid tumors. Achieve Life Sciences, the company that is developing this drug, are currently exploring options to out-license tenifatecan.