Imidazopyrazines of Formula I and pharmaceutically acceptable salts and mixtures thereof, are provided herein. Pharmaceutical compositions comprising at least one chemical entity and one or more pharmaceutically acceptable vehicle are also provided. Methods of treating patients suffering from certain diseases and disorders responsive to the inhibition of Syk activity, which comprises administering to such patients an amount of at least one chemical entity effective to reduce signs or symptoms of the disease or disorder are disclosed. These diseases include cancer (e.g., B-cell lymphoma and leukemia), autoimmune diseases, inflammatory diseases, acute inflammatory reactions, and allergic disorders. Methods of treatment include administering at least one chemical entity as a single active agent or administering at least one chemical entity in combination with one or more other therapeutic agents. Also provided are methods for determining the presence or absence of Syk kinase in a sample.