Due to the published in vitro and in vivo results with the pimelic diphenylamide HDAC inhibitors in cell and mouse models of FRDA and HD, we evaluated the HDAC isoform selectivity, cellular activity, in vitro and in vivo ADME properties of the preclinical prototype compound HDACi 4b to validate and extend previous findings and assess its therapeutic potential for HD. Here, HDAC9 is linked to Huntington disease.