Abstract: The present invention relates to novel substituted indolo[2,3-a]quinolizines and stereoisomeric forms thereof and/or pharmaceutically acceptable salts of these compounds as well as pharmaceutical compositions containing at least one of these substituted indolo[2,3-a]quinolizines together with pharmaceutically acceptable carrier, excipient and/or diluents. Said novel substituted indolo[2,3-a]quinolizines have been identified as useful for the prophylaxis and treatment of cancer by the induction of strong mitotic delays, chromosomal misalignments and mitotic tri- and multipolarization leading to cell cycle stop and apoptosis. Furthermore a synthesis for preparation of the substituted indolo[2,3-a]quinolizines is disclosed in the present invention.