BackgrounddBET6 is a highly potent, selective and cell-permeable degrader of BET based on PROTAC, with an IC50 of 14 nM, and has antitumor activity.dBET6 is a highly potent, selective and cell-permeable degrader of BET with an IC50 of 14 nM. dBET6 (100 nM) exhibits antitumor activity against T cell acute lymphoblastic leukemia (T-ALL) lines via degradation of BRD4.dBET6 (7.5 mg/kg, p.o., BID) reduces the leukemic burden in a disseminated mouse model of T-ALL.