Virtual Screening-Accelerated Discovery of a Phosphodiesterase 9 Inhibitor with Neuroprotective Effects in the Kainate Toxicity In Vitro Model

The therapeutic potential of phosphodiesterase 9 (PDE9) inhibitors: a patent review (2018-present)

INTRODUCTION

Phosphodiesterase 9 (PDE9) has been demonstrated as a potential target for neurological disorders and cardiovascular diseases, such as Alzheimer's disease and heart failure. For the last few years, a series of PDE9 inhibitors with structural diversities have been developed and patented by researchers and pharmaceutical companies, providing insights into first-in-class therapies of PDE9 drug candidates.

AREA COVERED

This review provides an overview of PDE9 inhibitors in patents from 2018 to the present.

EXPERT OPINION

Only a few of the current PDE9 inhibitors are highly selective over other PDEs, which limits their application in pharmacological and clinical research. The design and development of highly selective PDE9 inhibitors remain the top priority in future research. The advantages of targeting PDE9 rather than other PDEs in treating neurodegenerative diseases need to be explained thoroughly. Besides, application of PDE9 inhibitor-based combination therapies sheds light on treating diabetes and refractory heart diseases. Finally, PDE9 inhibitors should be further explored in clinical indications beyond neurological disorders and cardiovascular diseases.

Opportunities and perspectives of small molecular phosphodiesterase inhibitors in neurodegenerative diseases

Phosphodiesterase (PDE) is a superfamily of enzymes that are responsible for the hydrolysis of two second messengers: cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP). PDE inhibition promotes the gene transcription by activating cAMP-response element binding protein (CREB), initiating gene transcription of brain-derived neurotrophic factor (BDNF). The procedure exerts neuroprotective profile, and motor and cognitive improving efficacy. From this point of view, PDE inhibition will provide a promising therapeutic strategy for treating neurodegenerative disorders. Herein, we summarized the PDE inhibitors that have entered the clinical trials or been discovered in recent five years. Well-designed clinical or preclinical investigations have confirmed the effectiveness of PDE inhibitors, such as decreasing Aβ oligomerization and tau phosphorylation, alleviating neuro-inflammation and oxidative stress, modulating neuronal plasticity and improving long-term cognitive impairment.

In Silico Analysis of Selected Glycyrrhiza glabra (Licorice) Constituents: Exploring Their Modulatory Effects on Human Superoxide Dismutase, Human Phosphodiesterase-9 and Human Dipeptidyl Peptidase-4

Background Glycyrrhiza glabra (Licorice) has been known for its various biological activities. In the current investigation, we aimed to evaluate 11 (10 natural and one synthetic) selected constituents of G. glabra as potent modulatory agents of human superoxide dismutase (hSOD), human phosphodiesterase-9 (hPDE 9) and human dipeptidyl peptidase-4 (hDPP 4) using in silico method. Methodology The 11 selected constituents of G. glabra (Licorice) were investigated on the docking behaviour of hSOD, hPDE 9 and hDPP 4 by using the PatchDock method. In addition to docking, toxicity analysis was also carried out using the pkCSM free online server (University of Melbourne, Melbourne, AUS). Results Toxicity analysis has shown that four ligands (36%) of G. glabra (Licorice) are predicted to have human ether-a-go-go-related gene-2 (hERG 2) inhibition activity. The docking analysis showed that glabridin (-224.13 kcal/mol) has shown the highest atomic contact binding energy with the hSOD enzyme, whereas carbenoxolone has shown the maximum atomic contact binding energy with both the hPDE 9 and hDPP 4 enzymes (-239.57 and -173.50 kcal/mol) respectively. Conclusion Thus the present finding provides new information about 11 selected ligands of G. glabra (Licorice) as potent modulatory agents of hSOD, hPDE 9 and hDPP 4.