We developed a new HDAC inhibitor, CN133, which has been approved in performing clinical trials as the PET imaging tracer in brain disorders such as Alzheimer’s disease and schizophrenia [10, 11], which presented a higher class I HDAC binding affinity and selectivity in this study when compared to classic HDACIs SAHA and entinostat. Here, HDAC9 is linked to Alzheimer disease.