These pre‐clinical data suggest that the inhibition of class I HDAC isoforms could be an avenue for the treatment of neurodegenerative disease54; similarly, our unpublished data showed that inhibition of HDAC1, 2 or 8 activity by compound 13 effectively mitigated CCH‐induced cognitive impairment. Here, HDAC9 is linked to columnar cell hyperplasia of the breast.