Doxorubicin has antimitotic and cytotoxic activity through a number of proposed mechanisms of action: Doxorubicin forms complexes with DNA by intercalation between base pairs, and it inhibits topoisomerase II activity by stabilizing the DNA-topoisomerase II complex, preventing the religation portion of the ligation-religation reaction that topoisomerase II catalyzes.
Doxorubicin is an antineoplastic in the anthracycline class. General properties of drugs in this class include: interaction with DNA in a variety of different ways including intercalation (squeezing between the base pairs), DNA strand breakage and inhibition with the enzyme topoisomerase II. Most of these compounds have been isolated from natural sources and antibiotics. However, they lack the specificity of the antimicrobial antibiotics and thus produce significant toxicity. The anthracyclines are among the most important antitumor drugs available. Doxorubicin is widely used for the treatment of several solid tumors while daunorubicin and idarubicin are used exclusively for the treatment of leukemia. Doxorubicin may also inhibit polymerase activity, affect regulation of gene expression, and produce free radical damage to DNA. Doxorubicin possesses an antitumor effect against a wide spectrum of tumors, either grafted or spontaneous. The anthracyclines are cell cycle-nonspecific.
Doxorubicin is capable of undergoing 3 metabolic routes: one-electron reduction, two-electron reduction, and deglycosidation. However, approximately half of the dose is eliminated from the body unchanged. Two electron reduction yields doxorubicinol, a secondary alcohol. This pathway is considered the primary metabolic pathway. The one electron reduction is facilitated by several oxidoreductases to form a doxirubicin-semiquinone radical. These enzymes include mitochondrial and cystolic NADPH dehydrogenates, xanthine oxidase, and nitric oxide synthases. Deglycosidation is a minor metabolic pathway (1-2% of the dose undergoes this pathway). The resultant metabolites are deoxyaglycone or hydroxyaglycone formed via reduction or hydrolysis respectively. Enzymes that may be involved with this pathway include xanthine oxidase, NADPH-cytochrome P450 reductase, and cytosolic NADPH dehydrogenase.
LD50=21800 ug/kg (rat, subcutaneous)