Most compounds showed no significant cytotoxicity in the concentration range of the assay. Only 17a and 17c, both fluorothalidomide-based PROTACs, showed a moderate toxicity with IC50 values of 18.4 and 24.9 M, respectively. Since HDAC6-selective inhibitors usually also demonstrate minimal toxicity and inhibition of other HDAC isoforms was determined to be lower, the results align with our expectations from the HDAC inhibition assays.