Pulmonary arterial hypertension (PAH)
causes pathological increase
in pulmonary vascular resistance, leading to right-heart failure and
eventual death. Previously, phosphodiesterase-10 (PDE10) was reported
to be a promising target for PAH based on the studies with a nonselective
PDE inhibitor papaverine, but little progress has been made to confirm
the practical application of PDE10 inhibitors. To validate whether
PAH is ameliorated by PDE10 inhibition rather than other PDE isoforms,
here we report an integrated strategy to discover highly selective
PDE10 inhibitors as chemical probes. Structural optimization resulted
in a PDE10 inhibitor 2b with subnanomolar affinity and
good selectivity of >45 000-fold against other PDEs. The
cocrystal
structure of the PDE10–2b complex revealed an
important H-bond interaction between 2b and Tyr693. Finally,
compound 2b significantly decreased the arterial pressure
in PAH rats and thus validated the potential of PDE10 as a novel anti-PAH
target. These findings suggest that PDE10 inhibition may be a viable
treatment option for PAH.
Phosphodiesterase 5 (PDE5) inhibitors have been used as clinical agents to treat erectile dysfunction and pulmonary arterial hypertension (PAH). Herein, we detail the discovery of a novel series of chromeno[2,3-c]pyrrol-9(2H)-one derivatives as selective and orally bioavailable inhibitors against phosphodiesterase 5. Medicinal chemistry optimization resulted in 2, which exhibits a desirable inhibitory potency of 5.6 nM with remarkable selectivity as well as excellent pharmacokinetic properties and an oral bioavailability of 63.4%. In addition, oral administration of 2 at a dose of 5.0 mg/kg caused better pharmacodynamics effects on both mPAP (mean pulmonary artery pressure) and RVHI (index of right ventricle hypertrophy) than sildenafil citrate at a dose of 10.0 mg/kg. These activities along with its reasonable druglike properties, such as human liver microsomal stability, cytochrome inhibition, hERG inhibition, and pharmacological safety, indicate that 2 is a potential candidate for the treatment of PAH.
To identify phosphodiesterase-9 (PDE9) as a novel target for the treatment of vascular dementia (VaD), a series of pyrazolopyrimidinone analogues were discovered based on a hit 1. Hit-to-lead optimization resulted in a potent inhibitor 2 with excellent selectivity and physicochemical properties to enable in vivo studies. Oral administration of 2 (5.0 mg/kg) caused notable therapeutic effects in the VaD mouse model, providing a promising lead or chemical probe for investigating the biological functions of PDE9 inhibition.
Discovery of multitarget-directed ligands (MTDLs), targeting different factors simultaneously to control the complicated pathogenesis of Alzheimer's disease (AD), has become an important research area in recent years. Both phosphodiesterase 9A (PDE9A) and butyrylcholinesterase (BuChE) inhibitors could participate in different processes of AD to attenuate neuronal injuries and improve cognitive impairments. However, research on MTDLs combining the inhibition of PDE9A and BuChE simultaneously has not been reported yet. In this study, a series of novel pyrazolopyrimidinone-rivastigmine hybrids were designed, synthesized, and evaluated in vitro. Most compounds exhibited remarkable inhibitory activities against both PDE9A and BuChE. Compounds 6c and 6f showed the best IC values against PDE9A (6c, 14 nM; 6f, 17 nM) together with the considerable inhibition against BuChE (IC, 6c, 3.3 μM; 6f, 0.97 μM). Their inhibitory potencies against BuChE were even higher than the anti-AD drug rivastigmine. It is worthy mentioning that both showed moderate selectivity for BuChE over acetylcholinesterase (AChE). Molecular docking studies revealed their binding patterns and explained the influence of configuration and substitutions on the inhibition of PDE9A and BuChE. Furthermore, compounds 6c and 6f exhibited negligible toxicity, which made them suitable for the further study of AD in vivo.
The pathological processes of Alzheimer's disease and type 2 diabetes mellitus have been demonstrated to be linked together. Both PDE9 inhibitors and PPARγ agonists such as rosiglitazone exhibited remarkable preclinical and clinical treatment effects for these two diseases. In this study, a series of PDE9 inhibitors combining the pharmacophore of rosiglitazone were discovered. All the compounds possessed remarkable affinities towards PDE9 and four of them have the IC50 values <5 nmol/L. In addition, these four compounds showed low cell toxicity in human SH-SY5Y neuroblastoma cells. Compound 11a, the most effective one, gave the IC50 of 1.1 nmol/L towards PDE9, which is significantly better than the reference compounds PF-04447943 and BAY 73-6691. The analysis of putative binding patterns and binding free energy of the designed compounds with PDE9 may explain the structure—activity relationships and provide evidence for further structural modifications.
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