To further characterize degrader activity, we performed quantitative analysis of live-cell kinetic degradation of the CRISPR HiBiT-BET family members treated with SIM1 titrations over more than 6-log-order concentration range (10pM-30µM) (Fig. and Extended Data Fig. ). All BET family members showed complete degradation across a 4 log concentration range (3nM-30µM). A slight slowing of the initial rate of degradation (due to the hook effect) was manifested only at the highest concentrations (3-30µM) with BRD3 and BRD4, and to a much lesser extent BRD2 (Extended Data Fig. ). From the kinetic analyses, degradation rates and Dmax values were calculated and plotted versus concentration to obtain λmax and Dmax50 (Fig. ). SIM1 exhibited Dmax50 values of 60-400pM and BET family degradation preference of BRD2>BRD4>BRD3 on both λmax and Dmax50 (Fig. ). This differs from MZ1 which has preference for BRD4 (Fig. and 1e) .