The present invention relates to methods of using the compound, N-(4-((3-(2-amino-4-pyrimidinyl)-2-pyridinyl)oxy)phenyl)-4-(4-methyl-2-thienyl)-1-phthalazinamine or a pharmaceutically acceptable salt thereof, to treat cancers, including solid tumors, which have become resistant to treatment with chemotherapeutic agents, including anti-mitotic agents such as taxanes, and/or other anti-cancer agents, including aurora kinase inhibiting agents. The invention also includes methods of treating cancers refractory to such treatments by administering a pharmaceutical composition, comprising the compound to a cancer subject.
