The invention relates to a clusianon isomer and to the use thereof, in particular as a pharmaceutical or medical active ingredient, in particular for producing medicaments for the prophylactic and/or therapeutic (curative) treatment of tumor or cancer diseases as well as viral diseases. The aforementioned compound can be used in cytostatics and antiviral agents (virostatics). Said compound acts, in particular, as a topoisomerase and telomerase inhibitor and as a regulator in the MAP kinase signal transduction. Said compound can thus intervene at the cellular level in the proliferation mechanism of tumor or cancer cells and viruses.