In Vitro: PROTAC BRD4 Degrader-1 (compound 21) (2.5 μM; 24 hours) shows high inhibitory activity against the growth of human monocyte lymphoma cell line THP-1, with the IC50 value of 0.81 μM, and moderate activity against Raji and HL-60 cell lines.PROTAC BRD4 Degrader-1 (1 μM; 24 hours) effectively induces the degradation of BRD4 protein and suppression of c-Myc, while pomalidomide couldn’t degrade BRD4 at the low concentration.