Pharmacological characterization of a novel potent, selective, and orally active phosphodiesterase 2A inhibitor, PDM-631

Recently, we identified a novel phosphodiesterase 2 A (PDE2A) inhibitor, PDM-631 ((S)-3-cyclopropyl-6-methyl-1-(1-(4-(trifluoromethoxy)phenyl)propan-2-yl)-1,5-dihydro-4H-pyrazolo[3,4-d]pyrimidin-4-one). PDM-631 showed potent inhibitory activities for human and rat PDE2A with IC50 values of 1.5 and 4.2 nM, respectively and more than 2000-fold selectivity against other phosphodiesterases. In rat studies, PDM-631 showed oral bioavailability and good brain penetration, and increased the cGMP levels in the cortex. These data indicate that PDM-631 is a potent, selective, orally active, and brain-penetrable PDE2A inhibitor. In behavioral studies using rat models, PDM-631 (3-30 mg/kg) resulted in better discrimination between a novel object and a familiar one 48 h after the acquisition phase in the novel object recognition test, thus indicating that PDM-631 increased object recognition memory. In contrast, PDM-631 did not attenuate the conditioned avoidance response at the same dose range (3-30 mg/kg) in rats, indicating that PDM-631 did not show an antipsychotic-like effect. In test for extrapyramidal side effect, PDM-631 had no effect on catalepsy at the effective doses (10 and 30 mg/kg) in the novel object recognition test, while haloperidol caused catalepsy at a dose of 3 mg/kg. Our results suggest that PDM-631 is a good pharmacological tool that can be used to investigate the role of PDE2A and may have therapeutic potential for the treatment of cognitive impairments associated with schizophrenia and neurodegenerative disorders, without any extrapyramidal side effects.