De-ethylflavopereirine, a pharmaceutically acceptable salt thereof, a solvate or a hydrate thereof, or a pharmaceutically acceptable salt of a solvate or a hydrate thereof may be used as cancer therapy (i.e., prevention and/or treatment) in a subject in need thereof, including a pathological condition such as inflammation, especially chronic, or cancer (e.g., a carcinoma, a sarcoma, a melanoma, a leukemia, a lymphoma), especially a solid tumor and/or a metastasis thereof. In particular, systemic administration of such improved anti-cancer agents in effective amounts may selectively destroy cancer cells (including cancer stem cells) in a solid tumor and/or at a site of metastasis. They are well-tolerated by the subject, even at large systemic doses and their resulting high concentrations in the circulation, and provide safe and effective anti-cancer agents.
