PT3: A Novel Benzamide Class Histone Deacetylase 3 Inhibitor Improves Learning and Memory in Novel Object Recognition Mouse Model.

The importance of HDAC3 in transcriptional regulation of genes associated with long-term memory is well established. Here, we report a novel HDAC3 inhibitor, PT3, with an excellent blood-brain barrier permeability and ability to enhance long-term memory in mouse model of novel object recognition (NOR). PT3 exhibited higher selectivity for HDAC3 over HDAC1, HDAC6, and HDAC8 compared to the reference compound CI994. PT3 has significant distribution into the brain tissue with Cmax at 0.5 h and t1/2 of 2.5 h. Treatment with PT3 significantly improved the discrimination index in C57/BL6 mice in the NOR model. Brain tissue analysis of mice treated with PT3 for NOR test showed significant increase in H3K9 acetylation in hippocampus. Gene expression analysis by RT-qPCR of the hippocampus tissue revealed upregulation of CREB 1, BDNF, TRKB, Nr4a2, c-fos, PKA, GAP 43, PSD 95 and MMP9 expression in mice treated with PT3. Similar to the phenotype observed in the in vivo experiment, we found upregulation of H3K9 acetylation, CREB 1, BDNF, TRKB, Nr4a2, c-fos, PKA, GAP 43 and MMP9 expression in mouse neuronal (N2A) cells treated with PT3. Thus, our preclinical studies identify PT3 as a potential HDAC3 selective inhibitor that crosses the blood-brain barrier and improves the long-term memory formation in C57/BL6 mice. We propose PT3 as a candidate with therapeutic potential to treat age-related memory loss as well as other disorders with declined memory function like Alzheimer's disease.