Substrate degradation is associated with binding to CRBN. (A-D) 293T cells were transiently cotransfected with vectors carrying CRBN fused to NanoLuciferase and indicated substrate proteins fused to HaloTag. They were then treated with serial dilutions of decreasing doses of drug or vehicle for 6 hours and then the BRET signal was measured and the level in the vehicle-treated sample was normalized to 1. Data are mean ± SEM (n ≥ 4 replicates). Curves represent the logistic regression.