Active Motif's JIB-04 is a novel specific inhibitor of the Jumonji family of histone demethylases in vitro, in cancer cells and in tumors in vivo. IC50 = 230, 340, 435, 445, 855 and 1100 nM for JARID1A, JMJD2E, JMJD2B, JMJD2A, JMJD3 and JMJD2C respectively. JIB-04 reduces tumor burden and prolongs life in a mouse model. It suppresses translation initiation and enhances mTOR inhibitor sensitivity. It also inhibits the growth of temozolomide-resistant glioblastoma cells and crosses the blood brain barrier.