To identify the best degrader, concentration-dependent profiling at 4h treatments using immunoblots evidenced much lower DC50 values of 0.7 -9.5nM for SIM1-SIM3 compared to MZ1 (DC50 values of 25 -920nM) across all the BET proteins (Fig. and Extended Data Fig. ). To confirm greater potency of VHL-based degraders, we evaluated growth inhibition profiles of BET-sensitive cancer cell lines MV4;11 (Fig. ), A549, and HL-60 (Extended Data Fig. ) with SIM1-6 treatments. SIM1-SIM3 consistently showed more potent activity relative to SIM4-SIM6 and bivalent molecules MZ1 and MT1 (Fig. and Extended Data Fig. ). In both these experiments, SIM1 emerged as the most potent of the three VHL-based degraders.