The present invention provides methods for treating cancer and other pathologicalproliferating conditions by inhibiting mitosis using at least one pyrrolo[2,3-d]pyrimidinehaving the general formula (16): [insert formula here] where X is selected fromthe group consisting of lower alkyls, heteroalkyls, substituted or unsubstitutedaryls or heteroaryls, arylalkyls, and heteroarylalkyls； where R?1#191 is selectedfrom the group consisting of hydrogen, lower alkyls, heteroalkyls, substitutedor unsubstituted aryls or heteroaryls, arylalkyls, and heteroarylalkyls；where R?2#191 is selected from the group consisting of hydrogen, lower alkyls,heteroalkyls, alkoxys, substituted or unsubstituted aryls or heteroaryls；where R?3#191 is selected from the group consisting of zero, lower alkyls, heteroalkyls,alkenyls, and heteroalkenyls； and where R?4#191 is selected from the group consistingof substituted or unsubstituted aryls or heteroaryls, arylalkyls, heteroarylalkyls,and hydrogen. The compound may inhibit mitosis in cells that have developed multidrugresistance due to P-glycoprotein and MRP1, and facilitate the reversal of P-glycoproteinmediated resistance.
