Topixantrone (BBR 3576) is a hetero-analog of the anthrapyrazole class of compounds. The mechanism of action of BBR 3576 is similar to that of mitoxantrone in terms of DNA intercalation, DNA affinity, topoisomerase II interaction and formation of single-strand breaks. BBR 3576 showed curative antitumor activity at the maximum tolerated dose (MTD) with a number of long-term survivors and showed greater activity than mitoxantrone and doxorubicin in preclinical studies. BBR 3576 retained a high level of activity across a wide range of doses. In human xenograft studies, equivalent antitumor activity was observed when compared with doxorubicin and mitoxantrone. The compound showed reduced cardiotoxicity when repeatedly administered in rodent models. Topixantrone has a manageable toxicity profile on a 4-week schedule.