Design, Synthesis And Antitumor Activity Of HDACs-based Multi-target Inhibitors

The occurrence of cancer is the physiological activities of a complex process of multitargets and multicellular participate together. Thus, there are many limitations for the inhibition of single target in the treatment of cancer. Histone deacetylase is an anti-tumor drug target, which attracts broad interest in antitumor drug discovery. HDACs regulates acetylation process of many histone and non-histone proteins. Moreover, they also palyed important roles in the regulation of gene, transcription and cell proliferation, differentiation and death. HDACs have been recognized as an important family of targets for the treatment of cancer. Inhibition of HDACs can inhibit the growth and differentiation of cancer cells, and promote cancer cell apoptosis.Previous studies indicated that the mechanism of HDACs is involved in inducing acetylation of histone and promoting expression of P21. HDAC inhibitors have the synergistic effect with other antitumor inhibitors, which can effectively enhance the antitumor activity, such as tubulin, Hsp90, EGFR and topoisomerase inhibitors.Therefore, it is highly desirable to design and synthesis of novel HDACs-based multi-targeting antitumor drugs. This thesis is mainly divided into three parts:(1) Based on synergistic effects of HDACs and topoisomerase inhibitors, we discovered a kind of novel topoisomerase Ⅰ/Ⅱ/HDACs multi-target inhibitors; (2) Based on the novel Nampt inhibitor NCRC07392 derived from high-throughput screening, its structure-activity relationship and antitumor activity was investigated; (3) On the basis of the SAR of Nampt inhibitors, novel HDAC/Nampt dual-target inhibitors were designed, synthesized and assayed.1. Discovery of novel multi-target of topoisomerase Ⅰ/Ⅱ and HDACs inhibitorsThere is a synergistic antitumor effect on HDACs inhibitors and topoisomerase inhibitors. In our previous studies, novel Top1/Top2 dual inhibitors were designed and synthesized. Among them,3-amino -10-hydroxy evodiamine (B45) had excellent antitumor activity both in vitro and in vivo. Based on the pharmacophores of SAHA (a HDAC inhibitor) and B45, a total of 11 hybrid compounds were rationally designed. Biological assay confirmed that they were first-in-class triple HDAC1/Top1/Top2 inhibitors. The activity of several compounds is superior to that of positive drugs. Among them, compound 8C showed the best activity with IC50 value of 0.41μM for HCT116 colon cancer cell line. Moreover, it can effectively induce cell apoptosis with apoptosis rate of 79.1% at the concentration of 5 μM. In addition, Western blot assayed displayed that compound 8C significantly increased tumor cell histone acetylation levels.2. Design, synthesis and antitumor activity of nampt inhibitorsPreviously, our group identified the new nicotinamide phosphoribosyltransferase (Nampt) inhibitor NCRC07392 by high throughput screening. To optimize the structure of NCRC07392, we rationally designed and synthesized a class of NCRC07392 derivatives. As a result, a total of 15 new compounds were obtained, whose structures were confirmed by mass spectrometry and nuclear magnetic spectra. In vitro activity assay showed that most of them had moderate to good antitumor activity for three kinds of tumor cell lines. Among them, compounds 9 and 10 showed the strongest antitumor activity in vitro. However, Namptinhibition assay showed that most of the compounds were less active than the lead compound NCRC07392. Even though, the present work expanded the structure-activity relationship of the lead compound and lay the foundation for the future study.3. Design and synthesis of novel dual-inhibitors of Nampt and HDACsNampt is a kind of metabolic target. There is a cross way in the pathways of HDACs and Nampt. Nampt inhibitors and HDACs inhibitors have a synergistic effect in the treatment of tumor. Designing HDAC/Nampt dual-target inhibitors can effectively avoid the disadvantages of single-target inhibitor, which is expected to improve the antitumor activity.On the basis of the structural features of diaminobenzene HDAC inhibitor and triazole-containing Nampt inhibitors, a series of novel Nampt-HDAC dual-target inhibitors were designed, synthesized and assayed. First, novel dual inhibitors were designed by combing the diaminobenzene pharmacophore in theHDAC inhibitosr, the pyridine head groups of the Nampt inhibitors and the triazole linker groups. Compounds 5a showed the best Nampt and HDAC inhibitory activity with IC50 values of 15 nM and 18.6 nM, respectively. Further, we investigated the structure-activity relationships and found the pyridine ring and aminobenzene were favorable for the activity. Second, the terminal diaminobenzene group was further optimized. The result showed that para-substitution of the free amine group led to the decrease of the activity. Compounds 5a (Nampt IC50 = 18.6 nM, HDAC1 IC50 =15 nM) and 10a (Nampt IC50 = 41 nM, HDAC1 IC50 = 40 nM) showed excellent activity against both Nampt and HDAC1. Also, they showed potent in vitro antitumor activity.Notably, compound 5a showed balanced inhibitory activity for both enzymes and reprsents a promising HDAC-Nampt dual-target lead compound for further structural optimization to improve the antitumor activity.