Design, Synthesis, and Evaluation of Dihydropyranopyrazole Derivatives as Novel PDE2 Inhibitors for the Treatment of Alzheimer's Disease.

Phosphodiesterase 2 (PDE2) has been regarded as a novel target for the treatment of Alzheimer's disease (AD). In this study, we obtained (R)-LZ77 as a hit compound with moderate PDE2 inhibitory activity (IC50 = 261.3 nM) using a high-throughput virtual screening method based on molecular dynamics. Then, we designed and synthesized 28 dihydropyranopyrazole derivatives as PDE2 inhibitors. Among them, compound (+)-11h was the most potent PDE2 inhibitor, with an IC50 value of 41.5 nM. The molecular docking of PDE2-(+)-11h reveals that the 4-(trifluoromethyl)benzyl)oxyl side chain of the compound enters the H-pocket and forms strong hydrophobic interactions with L770/L809/F862, which improves inhibitory activity. The above results may provide insight for further structural optimization of highly potent PDE2 inhibitors and may lay the foundation for their use in the treatment of AD.

Discovery of Potent, Selective, and Orally Bioavailable Inhibitors against Phosphodiesterase-9, a Novel Target for the Treatment of Vascular Dementia.

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.

Screening, synthesis, crystal structure, and molecular basis of 6-amino-4-phenyl-1,4-dihydropyrano[2,3-c]pyrazole-5-carbonitriles as novel AKR1C3 inhibitors.

AKR1C3 is a promising therapeutic target for castration-resistant prostate cancer. Herein, an evaluation of in-house library discovered substituted pyranopyrazole as a novel scaffold for AKR1C3 inhibitors. Preliminary SAR exploration identified its derivative 19d as the most promising compound with an IC50 of 0.160 µM among the 23 synthesized molecules. Crystal structure studies revealed that the binding mode of the pyranopyrazole scaffold is different from the current inhibitors. Hydroxyl, methoxy and nitro group at the C4-phenyl substituent together anchor the inhibitor to the oxyanion site, while the core of the scaffold dramatically enlarges but partially occupies the SP pockets with abundant hydrogen bond interactions. Strikingly, the inhibitor undergoes a conformational change to fit AKR1C3 and its homologous protein AKR1C1. Our results suggested that conformational changes of the receptor and the inhibitor should both be considered during the rational design of selective AKR1C3 inhibitors. Detailed binding features obtained from molecular dynamics simulations helped to finally elucidate the molecular basis of 6-amino-4-phenyl-1,4-dihydropyrano[2,3-c]pyrazole-5-carbonitriles as AKR1C3 inhibitors, which would facilitate the future rational inhibitor design and structural optimization.

Discovery of Novel Pyrazolopyrimidinone Derivatives as Phosphodiesterase 9A Inhibitors Capable of Inhibiting Butyrylcholinesterase for Treatment of Alzheimer's Disease.

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 IC50 values against PDE9A (6c, 14 nM; 6f, 17 nM) together with the considerable inhibition against BuChE (IC50, 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.

Discovery of Novel Phosphodiesterase-2A Inhibitors by Structure-Based Virtual Screening, Structural Optimization, and Bioassay.

Phosphodiesterase-2A (PDE2A) is a potential therapeutic target for treatment of Alzheimer's disease and pulmonary hypertension. However, most of the current PDE2A inhibitors have moderate selectivity over other PDEs. In the present study, we described the discovery of novel PDE2A inhibitors by structure-based virtual screening combining pharmacophore model screening, molecular docking, molecular dynamics simulations, and bioassay validation. Nine hits out of 30 molecules from the SPECS database (a hit rate of 30%) inhibited PDE2A with affinity less than 50 µM. Optimization of compound AQ-390/10779040 (IC50 = 4.6 µM) from the virtual screening, which holds a novel scaffold of benzo[cd]indol-2(1H)-one among PDE inhibitors, leads to discovery of a new compound LHB-8 with a significant improvement of inhibition (IC50 = 570 nM). The modeling studies demonstrated that LHB-8 formed an extra hydrogen bond with Asp808 and a hydrophobic interaction with Thr768, in addition to the common interactions with Gln859 and Phe862 of PDE2A. The novel scaffolds discovered in the present study can be used for rational design of PDE2A inhibitors with high affinity.