Abstract: The present invention relates to a method of treating cellular proliferative diseases, in particular cancer, which comprises administering a modulator of the activity of the mitotic kinesin KSP, wherein the activity of the KSP modulator is dependent on the presence of microtubules. It is believed that the KSP modulators utilized in the instant method bind to the KSP protein in a previously unreported manner, since the compounds do not bind competitively with respect to either microtubules or ATP, the substrates of KSP. The modulators useful in the instant methods are furthermore not active against the non-microtubule stimulated activity of KSP. Cellular proliferative diseases that may be treated using the method disclosed herein are, for example cancer, hyperplasias, restenosis, cardiac hypertrophy, immune disorders and inflammation.