To quantitate time-dependent loss of cMyc, a known downstream effect of BET-induced degradation, cMyc was endogenously tagged with HiBiT in MV4;11 and protein levels were monitored in cell lysates at varying times with different concentrations of SIM1, cis-SIM1, and MT1 (Fig. , left and Extended Data Fig. ). Rapid and complete loss of cMyc was observed with 1nM SIM1 concentration (Fig. , left) whereas similar levels of cMyc loss with MT1 or cis-SIM1 were not achieved until 50-100nM treatments (Extended Data Fig. ). Cell viability assays revealed that, at 1nM treatment, only SIM1 (but not cis-SIM1 or MT1) resulted in measurable cellular death after 6h (Fig. , right). Similarly, at higher concentrations SIM1 was found to be significantly more cytotoxic than control compounds (Extended Data Fig. )