Identification of Pyrido[3,4-d]pyrimidine derivatives as RIPK3-Mediated necroptosis inhibitors.

Necroptosis executed by RIPK3-mediated phosphorylation of MLKL is a programmed necrotic cell death and implicated with various diseases such as sterile inflammation. We designed and synthesized pyrido[3,4-d]pyrimidine derivatives as novel necroptosis inhibitors capable of suppressing the phosphorylation of MLKL. Our SAR studies reveal that 20 possesses comparable inhibitory activity against RIPK3-mediated pMLKL in HT-29 cells relative to GSK872 (2), a representative selective RIPK3 inhibitor. Based on biochemical kinase assay results, 20 is comparable to GSK872 (2) with regard to activity against RIPK3 and less potent against RIPK1 than GSK872, indicating selectivity of 20 towards RIPK3 over RIPK1 is higher than that of GSK872. In HT-29 cells, 20 inhibits necroptosis via MLKL oligomerization impediment. Moreover, 20 suppresses migration and invasion of AsPC-1 cells by necroptosis induced- CXCL5 secretion downregulation. Significantly, 20 could relieve the TNFα-induced systemic inflammatory response syndrome in vivo. Taken together, this study would provide a useful insight into the design of novel necroptosis inhibitors possessing RIPK3-mediated pMLKL inhibitory activity.

Design, synthesis and anti-tumor activity studies of novel pyrido[3, 4-d]pyrimidine derivatives.

In order to find high-efficiency and low-toxic anti-tumor drugs, 29 pyrido[3,4-d]pyrimidine compounds were designed, synthesized and evaluated by MTT assay in vitro. The results presented that most of the compounds had good antitumor activities, among which compound 30 had the best anti-tumor activity on MGC803 cells (IC50 = 0.59 µM). Mechanistic studies exhibited that compound 30 inhibited migration of MGC803 and induced apoptosis. It was proved that compound 30 up-regulated expression of Bid and PARP, down-regulated expression of CycD1 by western blot experiments. This study indicated that compound 30 might be served as a lead agent for the treatment of human gastric cancers.

Identification of novel chemotypes as CXCR2 antagonists via a scaffold hopping approach from a thiazolo[4,5-d]pyrimidine.

The chemokine receptor CXCR2 and its ligands mediate neutrophil migration to the inflammation site, function as growth factors in many tumor cells and are involved in angiogenesis. Moreover, CXCR2 mediated recruitment of myeloid-derived suppressor cells results in tumor immunosuppression. Consequently, CXCR2 antagonism is a promising strategy for cancer immunotherapy and treatment of inflammatory disorders. Over a decade ago, several thiazolo[4,5-d]pyrimidines were reported as potent CXCR2 antagonists. Optimization of this scaffold focused mainly on the ring substituents, while the aromatic core was mostly unexplored. In this study, a scaffold hopping strategy was applied to the unsubstituted thiazolo moiety. Fourteen novel bicyclic heteroaromatic and cycloaliphatic systems were prepared and evaluated for CXCR2 antagonism using binding and calcium mobilization assays. This study revealed that the triazolo[4,5-d]pyrimidine, the isoxazolo[5,4-d]pyrimidine and the pyrido[3,4-d]pyrimidine scaffolds were endowed with IC50 values below 1 µM in both assays and therefore are promising skeletons for further optimization.

Studies of Interaction Mechanism between Pyrido [3,4-d] Pyrimidine Inhibitors and Mps1.

Monopolar spindle 1 (Mps1), a dual-specific kinase, is related to the proper execution of chromosome biorientation and mitotic checkpoint signaling. The overexpression of Mps1 promotes the occurrence of cancer or the survival of aneuploid cancer cells, in other words, the reduction of Mps1 will severely reduce the viability of human cancer cells. Therefore, Mps1 is a potential target for cancer treatment. Recently, a series of novel pyrido [3,4-d] pyrimidine derivatives targeting Mps1 with high biological activity were synthesized. The crystal structure of Mps1 in complex with pyrido [3,4-d] pyrimidine derivatives was also reported, but there were no specific mechanism studies for this series of small molecule inhibitors. In this study, complexes binding modes were probed by molecular docking and further validated by molecular dynamics simulations and the molecular mechanics/generalized Born surface area (MM/GBSA) method. The results indicated that the van der Waals interactions and the nonpolar solvation energies were responsible to the basis for favorable binding free energies, all inhibitors interacted with residues I531, V539, M602, C604, N606, I607, L654, I663, and P673 of Mps1. By analyzing the hydrogen bonds, we found the residues G605 and K529 in Mps1 formed stable hydrogen bonds with compounds, it was more conducive to activities of Mps1 inhibitors. According to the above analysis, we further designed five new compounds. We found that compounds IV and V were better potential Mps1 inhibitors through docking and ADMET prediction. The obtained new insights not only were helpful in understanding the binding mode of inhibitors in Mps1, but also provided important references for further rational design of Mps1 inhibitors.

Discovery of potent epidermal growth factor receptor (EGFR) degraders by proteolysis targeting chimera (PROTAC).

Epidermal growth factor receptor (EGFR), a member of the HER family, is closely related to the development of multiple cancers. Herein, we report the discovery of small molecule EGFR degraders based on the proteolysis targeting chimera (PROTAC) strategy. In the present study, 13 EGFR degraders containing pyrido[3,4-d] pyrimidine moiety were designed and synthesized. Promising PROTACs 2 and 10 induced degradation of EGFR in HCC827 cells with the DC50 values of 45.2 and 34.8 nM, respectively. Cellular protein-controlling machinery ubiquitin proteasome system (UPS) was involved in the degradation process. Furthermore, the degraders 2 and 10 could significantly induce the apoptosis of HCC827 cells and arrest the cells in G1 phase. These findings demonstrated that compounds 2 and 10 could serve as effective EGFRdel19-targeting degraders in HCC827 cells. v.

Synthesis and biological evaluation of irreversible EGFR tyrosine kinase inhibitors containing pyrido[3,4-d]pyrimidine scaffold.

In the present study, a new class of compounds containing pyrido[3,4-d]pyrimidine scaffold with an acrylamide moiety was designed as irreversible EGFR-TKIs to overcome acquired EGFR-T790M resistance. The most promising compound 25h inhibited HCC827 and H1975 cells growth with the IC50 values of 0.025 µM and 0.49 µM, respectively. Meanwhile, 25h displayed potent inhibitory activity against the EGFRL858R (IC50 = 1.7 nM) and EGFRL858R/T790M (IC50 = 23.3 nM). 25h could suppress EGFR phosphorylation in HCC827 and H1975 cell lines and significantly induce the apoptosis of HCC827 cells. Additionally, compound 25h could remarkably inhibit cancer growth in established HCC827 xenograft mouse model at 50 mg/kg in vivo. These results indicated that the 2,4-disubstituted 6-(5-substituted pyridin-2-amino)pyrido[3,4-d]pyrimidine derivatives can serve as effective EGFR inhibitors and potent anticancer agents.

Discovery of 2,4,6-trisubstitued pyrido[3,4-d]pyrimidine derivatives as new EGFR-TKIs.

Targeting acquired drug resistance is the major challenge in the treatment of EGFR-driven non-small cell lung cancer (NSCLC). In this study, a novel class of compounds containing pyrido[3,4-d]pyrimidine scaffold was designed as new generation EGFR-TKIs to overcome this challenge. The most promising compound B30 inhibited HCC827 and H1975 cells growth with the IC50 values of 0.044 µM and 0.40 µM, respectively. Meanwhile, B30 displayed potent inhibitory activity against the EGFRL858R (IC50 = 1.1 nM) and EGFRL858R/T790M/C797S (IC50 = 7.2 nM). B30 could suppress EGFR phosphorylation in a dose-dependent manner in HCC827 cell line and significantly induce the apoptosis of HCC827 cells. Molecular docking indicated that the hydroxyl in B30 could form additional hydrogen bond with mutant Ser797. These findings strongly support our assumption that 2,4,6-trisubstitued pyrido[3,4-d] pyrimidine derivatives can serve as EGFR-TKIs. The predicted hydrogen bond interaction formed by a small molecule inhibitor with mutant Ser797 is available to design the fourth-generation EGFR-TKIs.

18F-Labeled Pyrido[3,4-d]pyrimidine as an Effective Probe for Imaging of L858R Mutant Epidermal Growth Factor Receptor.

In nonsmall-cell lung carcinoma patients, L858R mutation of epidermal growth factor receptor (EGFR) is often found, and molecular target therapy using EGFR tyrosine kinase inhibitors is effective for the patients. However, the treatment frequently develops drug resistance by secondary mutation, of which approximately 50% is T790M mutation. Therefore, the ability to predict whether EGFR will undergo secondary mutation is extremely important. We synthesized a novel radiofluorinated 4-(anilino)pyrido[3,4-d]pyrimidine derivative ([18F]APP-1) and evaluated its potential as a positron emission tomography (PET) imaging probe to discriminate the difference in mutations of tumors. EGFR inhibition assay, cell uptake, and biodistribution study showed that [18F]APP-1 binds specifically to the L858R mutant EGFR but not to the L858R/T790M mutant. Finally, on PET imaging study using [18F]APP-1 with tumor-bearing mice, the H3255 tumor (L858R mutant) was more clearly visualized than the H1975 tumor (L858R/T790M mutant).