Pyridin[1,2-a]pyrimidinyl compounds, pharmaceutically acceptable salts, and prodrugs thereof; compositions that include a pharmaceutically acceptable carrier and one or more of the pyridino[1,2-a]pyrimidinyl compounds, either alone or in combination with at least one additional therapeutic agent. Methods of using the pyridino[1,2-a]pyrimidinyl compounds, either alone or in combination with at least one additional therapeutic agent, in the prophylaxis or treatment of proliferative diseases.