Exatecan Intermediate 4 (compound B) is an intermediary in the synthesis of Exatecan (DX-8951), a chemotherapeutic agent classified as a camptothecin analogue. It acts by interacting with DNA to disrupt the proliferation and division of tumor cells, thereby inhibiting tumor growth. Exatecan is primarily researched for its potential application in the treatment of various cancers, including ovarian, lung, and breast cancer.