Design,Synthesis And Preliminary Activity Study Of4-aminonaphthalen-1-ols As Abl And Akt1Protein Kinase Inhibitors

Objective:Aberrant angiogenesis, involving the proliferation of endothelial cells (ECs) and the migration of these endothelial cells to the tumor site to form new capillaries, is a critical step for tumor cell proliferation, invasion and metastasis. Abl and Akt (proteinkinase B, PKB) protein kinases are two important signaling pathway nodes in tumor cells and endothelial cells, they can modulate many important physiological processes by phosphorylation of downstream substrates, including cell survival, proliferation, migration and angiogenesis, etc.There are three kinds of protein kinase inhibitors according to the difference in binding cites of kinases:protein kinase inhibitors acting on the ATP-binding site, protein kinase inhibitors acting in the regulatory region and allosteric substrate competitive protein kinase inhibitors. Up to now, a large number of small-molecule angiogenesis inhibitors have been reported. Among them, the approval of multi-kinase inhibitors, Sunitinib, Pazopanib and Sorafenib, boosts the optimism of antiangiogenic agents as an effective way to control tumor growth. However, severe drug resistance and on-target adverse events such as hypertension, proteinuria, hemorrhage and hypothyroidism are observed during treatment with these angiogenesis inhibitors, indicating persistent effort required in this research field. With the the deepening of research of Bcr-Abl and Akt related signaling pathways, Abl and Akt have become hotspots in anticancer research.Methods:In this study, Hit6a, showing obvious antiangiogenic activity, was discovered by a computer-aided drug design (CADD) process. In the subsequent kinase screening test, Hit6a can selectively inhibit Abl kinase Aktl kinase. Then we designed and synthesized five series of4-aminonaphthalen-l-ols based on the structure of Hit6a. And we have tested the in vitro anti-proliferation activity, in vitro anti-angiogenesis activity and in vitro kinase inhibition activity of all synthesized compounds for SAR studies and for seeking more potent lead compound than Hit6a.Results:In this study, five series of81target compounds were synthesized, and all the structures were identified by ESI-MS, HRMS and1H-NMR. Most of the compounds were novel and have not been reported in the literature. We have tested the in vitro anti-proliferation activity, in vitro anti-angiogenesis activity and in vitro kinase inhibition activity of all synthesized compounds. Experimental results show that the regularities of synthesized compounds in inhibiting Abl and Akt proteins are highly consistent with their anti-proliferation activity and anti-angiogenic activity. The anti-angiogenic activity is not related with inhibiting VEGF/VEGFR. We speculated that4-aminonaphthalen-l-ols can supress the tumor proliferation and tumor-induced angiogenesis by inhibiting the activities of Abl and Aktl proteins.The SAR study indicated that the naphthol ring of Hit6a may interacte with the hydrophobic region of active sites of protein kinase by a combination of hydrophobic interaction and π-π stacking. Triazole structure can stretch to DFG motif and form hydrogen bond with aspartate. The-SO2NH-group can also form hydrogen bonds with amino acid residues from Hinge, G-loop or P-loop to enhance the adhesion with the kinase. Besides, the-SO2NH-group can make the compound form an easy combination with the active sites. Different aromatic groups of R show a certain regularity in inhibiting the kinase activity.Based on the SAR studies, we kept the naphthol ring,-SO2NH-group and triazole structure unchanged, and introduced two methoxy groups to the6and7position of the naphthalene ring to enhance the hydrophobic interaction with the protein, and then to improve the kinase inhibition ability and selectivity. Compounds26a-26g exhibited better kinase inhibition activities than any other compounds of seriess A-D, with the IC50values all below1μM. Compound26g was found to be the most potent compound, of which the IC50values to Abl and Akt1were0.16and0.46μM, respectively, about tenfold better than Hit6a. But the introduction of the methoxy groups resulted in poor water-solublility. In order to improve the water-solublility of compound26g, we introduced a propyl morpholine to the oxygen atom of position6and gained the compound33a.33a can effectively inhibit the Abl and Aktl with the IC50values being0.13and0.28μM, respectively. So compound33a is a promising both Abl and Aktl kinase inhibitor with good water-solubility.Conclusions:Based on the crystal structure of Abl and Akt1, the interaction model Hit6a with Abl and Aktl and the previous work of our lab, five series of81target small molecule peptidomimetics were designed and synthesized as Abl and Aktl inhibitors. By preliminary in vitro bioactivity assay, we found several potencial compounds such as compounds26g and33a, which need to be further developed in the future. The QSAR and binding models of these compounds were also stutied, which would be beneficial for further design and development of novel small molecule Abl and Aktl inhibitors in the future.It has been proven that the strategy, inhibiting endothelial cell proliferation and tumor angiogenesis through the blockade of the key proteins Abl and Akt in cell signaling pathway, contributes more in tumor treatment.