The anthracyclines (including daunomycin, doxorubicin, epirubicin and idarubicin) discovered over 25 years ago still remain amongst the most powerful anticancer agents used in the clinic. Primarily they act as topoisomerase II poisons, but can be also activated by formaldehyde leading to the formation of even more cytotoxic anthracycline-DNA adducts.
The next generation of DNA intercalators were synthesised based on the structure on the anthracyclines and this lead to the identification of the synthetic anthracenedione known as mitoxantrone. The mode of action of mitoxantrone mimics the anticancer activity of the anthracyclines. Mitoxantrone is a DNA intercalating topoisomerase II poison that forms lesions in double-stranded DNA resulting in cell death. A novel mechanism was discovered whereby mitoxantrone can also be activated by formaldehyde. Mitoxantrone has lower toxicity when compared to other anthracyclines but still exerts toxic side-effects such as cardiotoxicity and myelosupression. The second generation anthracenedione, pixantrone exhibits great anticancer potency in mice models without cardiotoxicity. It can be activated by formaldehyde resulting in the formation of adducts with DNA specifically at CpG sites, however these DNA adducts are inherently unstable. Currently, pixantrone has passed Phase III clinical trials and it has been approved for the treatments of aggressive non-Hodgkin B-cell lymphomas.
This study focuses on the development of a new class of compounds based upon mitoxantrone and pixantrone. Strategies were employed to overcome challenging steps in the synthesis of these new compounds. The second part of the project focuses on the biological effects of the new compounds. A new assay was developed to adapt an original conventional DNA crosslinking (adduct-detecting) assay to a high throughput system to test the covalent binding characteristics of new compounds. The new assay was then automated to rapidly obtain reliable results. A new compound was identified to form stable DNA crosslinks while also retaining its topoisomerase II poisoning characteristics.