Cardiac toxicity of antineoplastic anthracyclines

Anthracyclines play a major role in the treatment of solid malignancies, but their clinical use is limited by acute or chronic cardiac toxicity. This is not due to the same molecular action involved in the antineoplastic effect, i.e. topoisomerase II inhibition, but can be attributed to different mechanisms: free radical generation, stimulation of sarcoplasmic reticulum calcium release, binding to anionic phospholipids, alteration of sphingolipid metabolism, modulation of gene expression. Anthracycline metabolites, particularly 13-hydroxy derivatives, might contribute to impair iron and calcium homeostasis. Unresolved issues are the relative importance of such injurious mechanisms and the relationship between acute and chronic toxicity. Attempts to reduce anthracycline toxicity have been focused on the development of new derivatives, on the adoption of peculiar delivery systems, and on the association with substances able to interfere with the mechanism responsible for cardiotoxicity. Many anthracyclines have been synthesized and screened, but no major improvement in therapeutic index has been obtained. A possible exception might be represented by the new disaccharidic derivatives, which have provided promising results in preclinical studies. Liposome encapsulation and association with the iron chelator dexrazoxane have also proved to be useful. Novel approaches are targeted at the effects of anthracyclines on nitric monoxide metabolism and on sphingolipid metabolism.