As an alternative to PROTACs based on hydroxamic acids to target HDACs we have been investigating HDAC1-3 selective benzamides as the HDAC binding ligand in PROTACs.54,58 PROTACs 4 and 5 were identified as degraders of HDAC1 and HDAC2 in the colorectal carcinoma HCT116 cell line. This evidence concerns the gene HDAC1 and colorectal carcinoma.