Although 17c is an unselective HDAC inhibitor, its selective degradation of HDAC6 is rather unexpected. In previous studies, we and other groups found selective degradation of HDAC6 mediated by CRBN-recruiting non-selective HDAC ligand-containing PROTACs. 17c represents such a degrader, since HDAC assays showed a non-selective HDAC inhibition profile similar to that of A6.