Novel compounds having a fused bicyclic heteroaromatic ring system substituted with a heteroaryl five-membered ring are disclosed. The compounds inhibit growth of a variety of types of cancer cells, and are thus useful for treating cancer. Efficacy of these compounds is demonstrated with a system for monitoring cell growth/migration, which shows they are potent inhibitors of growth and/or migration of cancer cells. In addition, compounds of the invention were shown to stop growth of tumors in vivo, and to reduce the size of tumors in vivo. Compositions comprising these compounds, and methods to use these compounds and compositions for treatment of cancers, are disclosed.