By structure-based drug design, Celgene developed a novel KDM4 inhibitor, QC6352 (IC50 = 35−104 nM, for KDM4A–D), which potently suppresses the proliferation, sphere formation, and in vivo tumor growth of breast cancer and also reduces the tumor-initiating cell population in breast cancer [89]. Here, KDM4A is linked to breast cancer.