STC-15 is an orally active RNA methyltransferase METTL3 inhibitor with the activity of activating anti-tumor immunity and reshaping the tumor microenvironment. STC-15 inhibits tumor growth by activating anti-cancer immune responses associated with increased interferon signaling and synergizes with T-cell checkpoint blockade. STC-15 can be used in the study of proliferative diseases such as cancer and autoimmune diseases.