4SC-207 is a novel, orally available cellcycle blocker (CCB) for the treatment of tumours resistant to chemotherapy. This anti-mitotic compound inhibits the division of actively proliferating tumour cells. In preclinical testing, apoptosis was observed in dividing cancer cells only, rather than in non-proliferating cells. A prominent characteristic of 4SC-207 is its resistance breaking activity. 4SC-207 also affects cancer cells that have built up resistance to taxanes and alkaloids. This resistance to chemotherapy is one of the most important causes for the lack of activity of first-line therapies following a relapse.