Another notable structure-degradation relationship was observed for the tubastatin A-based degraders AP1 and AP4 which demonstrated stronger degradation potency toward class IIb HDACs than the corresponding bicyclic derivative-based degraders (see AP1 vs. AP3 and AP4 vs. AP6; see Table and). When comparing the degradation efficacy of the pomalidomide-based degraders with the phenylglutarimides, it is evident that the phenylglutarimides have lower DC50 values (see AP1 vs. AP4 and AP3 vs. AP6; see Table and). However, this improvement comes at the expense of a prominent "hook effect".