To monitor residence time, termed the complex half-life t½, the HiBiT-BRD2 and BRD4 CRISPR cells were first incubated with saturating concentrations of SIM1, cis-SIM1 or parent compounds, followed by a competitive BET fluorescent tracer. The NanoBRET signal produced from this displacement can be monitored kinetically, the rate and intensity of which directly correlates to the residence time of the initial compound-bound complex. As controls, JQ1 had a short residence time similar to the monovalent tracer alone, while MT1 showed a longer residence time, both in terms of calculated rate, Kobs (h -1 ) and complex half-life, t½ (h) (Fig. ).