Camptothecin

Overview
Camptothecin is a plant secondary metabolite used as an anti-cancer drug that damages DNA, leading to the destruction of the cell.

It comes from Camptotheca acuminata, a deciduous tree found in southern China. Stem woods of Nothopodytes foetida (previously known as Mappia foetida) found in the western ghats of India are an even better source of camptothecin.(2) A close analogue, 9-methoxycamptothecin, is also present in the same source.

Mechanism of action
Camptothecin affects the activity of the enzyme topoisomerase I, whose normal action is to cleave, unwind, and religate DNA.

When camptothecin binds to topoisomerase I, it will be able to cleave but not to religate DNA. Thereby, camptothecin causes single strand breaks in DNA.

Related medications
Since Camptothecin manifested a severe life threatening adverse reaction in the form of cystitis (Inflammation of the urinary bladder and ureters) concerted efforts over years by many research institutions, academic as well as industrial, resulted in chemically related analogues with less toxicity and enhanced therapeutic potency.Topotecan (trade name Hycamtin) and irinotecan {trade name Camptosar, also known as CPT-11) are camptothecin derivatives marketed as anti-cancer drugs by GlaxoSmithKline and Pfizer, respectively. Topotecan is indicated for small cell lung cancer after failure of first-line chemotherapy and metastatic carcinoma of the ovary following failure of initial or subsequent chemotherapy. Irinotecan is indicated for colorectal cancers and is usually taken with other drugs in chemotherapy.