Abstract: In one embodiment, a method of treating cancer in a patient comprises administering cGAMP or cGAsMP to a patient having cancer and allowing the cGAMP or cGAsMP to treat the cancer. In another embodiment, a method for en2ymatically synthesizing and purifying cGAMP or cGAsMP comprises providing cGAS; combining cGAS with ATP or ATP phosphorothioate, respectively, and GTP to produce cGAMP or cGAsMP; separating cGAMP or cGAsMP from the cGAS and DNA by ultrafiltration; and purifying cGAMP or cGAsMP using ion exchange chromatography and optionally gel filtration chromatography.