JIB-04 (E-isomer) is a potent, cell-permeable inhibitor of Jumonji histone demethylases in vitro and in vivo. (In vitro IC50 values are 230, 340, 435, 445, 855 and 1100 nM for JARID1A, JMJD2E, JMJD2B, JMJD2A, JMJD3 and JMJD2C respectively). JIB-04 is not a competitive inhibitor of α-ketoglutarate ; it selectively inhibits viability of several human cancer cell lines with little toxicity towards normal cells, and also diminishes tumor growth in xenograft mouse models. MW: 308.76. Purity ≥98% by HPLC