MZ1 is a non-covalent, reversible VHL-based BRD2 degrader which can be washed out (Fig. and Supplementary Fig. ) . In contrast, in the presence of  unsaturated indolinone 9 under the same washout conditions BRD2 levels did not recover (Fig. ). Direct binding to DCAF11 was proven by means of BODIPY-labelled analog 17 (Fig. ). This fluorescent compound binds to DCAF11 in concentration-and time-dependent manner, and binding is prevented by addition of non-labelled monovalent indolinone 2 (Fig. , e and Supplementary Fig. ). In conclusion, the data is consistent with a covalent attachment of the  -unsaturated compounds to DCAF11.