Design, synthesis, and biological evaluation of Pyrido[1,2-a]pyrimidin-4-one derivatives as novel allosteric SHP2 inhibitors.

SHP2 (Src homology-2-containing protein tyrosine phosphatase 2) plays an important role in cell proliferation, survival, migration by affecting RAS-ERK, PI3K-AKT, JAK-STAT signaling pathways and so on. Overexpression or gene mutation of SHP2 is closely linked with a variety of cancers, making it a potential therapeutic target for cancer disease. In this paper, 30 target compounds bearing pyrido[1,2-a]pyrimidin-4-one core were synthesized via two-round design strategy by means of scaffold hopping protocol. It was evaluated the in vitro enzymatic inhibition and cell antiproliferation assay of these targets. 13a, designed in the first round, presented relatively good inhibitory activity, but its molecular rigidity might limit further improvement by hindering the formation of the desired "bidentate ligand", as revealed by molecular docking studies. In our second-round design, S atom as a linker was inserted into the core and the 7-aryl group to enhance the flexibility of the structure. The screening result revealed that 14i could exhibit high enzymatic activity against full-length SHP2 (IC50 = 0.104 µM), while showing low inhibitory effect on SHP2-PTP (IC50 > 50 µM). 14i also demonstrated high antiproliferative activity against the Kyse-520 cells (IC50 = 1.06 µM) with low toxicity against the human brain microvascular endothelial cells HBMEC (IC50 = 30.75 µM). 14i also displayed stronger inhibitory activities on NCI-H358 and MIA-PaCa2 cells compared to that of SHP099. Mechanistic studies revealed that 14i could induce cell apoptosis, arrest the cell cycle at the G0/G1 phase and downregulate the phosphorylation levels of Akt and Erk1/2 in Kyse-520 cells. Molecular docking and molecular dynamics studies displayed more detailed information on the binding mode and binding mechanism of 14i and SHP2. These data suggest that 14i has the potential to be a promising lead compound for our further investigation of SHP2 inhibitors.

Absence of the Klotho Function Causes Cornea Degeneration with Specific Features Resembling Fuchs Endothelial Corneal Dystrophy and Bullous Keratopathy.

The Klotho loss-of-function mutation is known to cause accelerated senescence in many organs, but its effects on the cornea have not been published. The present study aims to investigate the effects of the Klotho null mutation on cornea degeneration and to characterize the pathological features. Mouse corneas of Klotho homozygous, heterozygous, and wild-type mice at 8 weeks of age for both genders were subject to pathological and immunohistological examinations. The results show an irregular topography on the corneal surface with a Klotho null mutation. Histological examinations revealed a reduced corneal epithelial cell density, endothelial cell-shedding, and decreased cornea stromal layer thickness in the absence of the Klotho function. Furthermore, guttae formation and the desquamation of wing cells were significantly increased, which was comparable to the characteristics of Fuchs endothelial corneal dystrophy and bullous keratopathy. The mechanism analysis showed multi-fold abnormalities, including oxidative stress-induced cornea epithelium apoptosis and inflammation, extracellular matrix remodeling in the stroma, and a disruption of epithelial repair, presumably through the epithelial-mesenchymal transition. In conclusion, cornea degeneration was observed in the Klotho loss-of-function mutant mice. These pathological features support the use of Klotho mutant mice for investigating age-related cornea anomalies, including Fuchs endothelial corneal dystrophy, bullous keratopathy, and dry eye diseases.