The present invention provides protein kinase inhibitors comprising imidazo[1,2-b]pyridazine and pyrazolo[1,5-a]pyrimidine compounds of the following structure (I) and (II): or a stereoisomer, prodrug or pharmaceutically acceptable salt thereof, wherein R, R1, R2 and X are as defined herein. Compositions and methods for using the same in the treatment of cancer and other Pim kinase-associated conditions are also disclosed.