Rubitecan

Rubitecan (RFS 2000), a camptothecin derivative, is an orally active topoisomerase I inhibitor with broad antitumor activity, and induces protein-linked DNA single-strand breaks, thereby blocking DNA and RNA synthesis in dividing cells[1][2][3].
Rubitecan is a pyranoindolizinoquinoline that is camptothecin in which the hydrogen at position 9 has been replaced by a nitro group. It is a prodrug for 9-aminocamptothecin. It has a role as an antineoplastic agent, an EC 5.99.1.2 (DNA topoisomerase) inhibitor and a prodrug. It is a pyranoindolizinoquinoline, a C-nitro compound, a semisynthetic derivative, a tertiary alcohol and a delta-lactone.|Rubitecan is a semisynthetic agent related to camptothecin with potent antitumor and antiviral properties. Rubitecan binds to and inhibits the enzyme topoisomerase I and induces protein-linked DNA single-strand breaks, thereby blocking DNA and RNA synthesis in dividing cells; this agent also prevents repair of reversible single-strand DNA breaks. (NCI04)
Rubitecan, marketed by Supergen as Orathecin, is a promising oral treatment for solid melanoma, prostate, breast, ovarian, and other cancers, as well as leukemia. It is a derivative of camptothecin, a topoisomerase inhibitor known from Chinese Traditional Medicine. It selectively targets the critical S-stage of cellular reproduction – particularly in acidic environments, as in many cancer cells – relaxing DNA supercoiling and generating lethal breaks in the DNA. Due to insolubility, its biological delivery mechanism is not yet effective, and it has not been approved for clinical use.
Rubitecan is a DNA topoisomerase I inhibitor. It inhibits DNA topoisomerase I and increases the fraction of supercoiled DNA in a cell-free assay in a concentration-dependent manner. Rubitecan inhibits the growth of A121 ovarian and H460 lung cancer cells (IC50s = 4 and 2 nM, respectively). It also inhibits the growth of doxorubicin-susceptible and -resistant MCF-7 breast cancer cells (IC50s = 2 and 3 nM, respectively). Rubitecan (4 mg/kg twice per week) reduces tumor growth in a U937 leukemia mouse xenograft model.
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