Design, Synthesis And Antitumor Activities Of Small Molecule Tubulin Inhibitors

Cancer has severely threatened human health and life. Although great progress has been made in the research and application of antitumor drugs, there are still some drawbacks, such as low curative effect, high toxicity and inducing multidrug resistance. So the need remains for development of new antitumor drugs to prevent and treat tumor.Microtubules are the key components of the cytoskeleton. They are crucial in the development and maintenance of cell shape, in cell division and mitosis, in cell signaling and in the transport of components throughout cells. Their importance in mitosis and cell division makes microtubules an important target for antitumor drugs. Tubulin inhibitors which act on microtubules have also become a class of effective antitumor drugs.Indibulin is a novel synthetic tubulin inhibitor which destabilizes microtubules and blocks cell cycle transition specifically at G2-M phase. It exerts significant antitumor activity in both in vitro and in vivo studies. Indibulin also has a number of superior properties, such as being easy to synthesize, oral applicability and efficacy toward MDR tumor cells, so it has been evaluated in PhaseⅠclinical trials as a drug candidate. Based on the above results, indibulin was selected as the lead compound for antitumor activity and 39 substituted indol-3-yl-2-oxoacetamides were synthesized according to the theories of bioisosterism, etc. In order to further study their structure-activity relationships (SAR) and get the novel antitumor compounds, we synthesized 4 2-hydroxy-(2-indol-3-yl)acetamides,21 2-(imidazol-1-yl)-2-(indol-3-yl)acetamides and 9 2-indolyl-2-(1,2,4-triazol-1-yl)acetamides. Furthermore,4 2-hydroxy-2-(indol-3-yl)-N-(pyridin-4-yl)acetamide borane complexes and 14 bis(indolyl)acetamides were also synthesized. The structures of all the above compounds have been confirmed by MS and 1H NMR. Among them, 88 compounds have not been reported in the literature.In order to obtain the antitumor agents which are more potent, less toxic and effective against multidrug resistance,7 4α/4β-(imidazol-1-yl)-4-desoxypodophyllotoxin derivatives and an 4-O-[(imidazol-1-yl)carbonyl]podophyllotoxin derivative have been designed and synthesized for antitumor agents based on the relevant literature reports. All the above compounds have not been reported in the literature and the structures of these compounds have been confirmed by HRMS,1H NMR,13C NMR and IR.All the indibulin derivatives were evaluated for their cytotoxic activitiy against three tumor cell lines that comprise HeLa, SKOV3 and MCF-7. using indibulin as reference compound by the standard MTT method. The result showed that 25 compounds exhibited promising antitumor potency and 6 compounds including SH-5, SH-9 and SH-10, etc. demonstrated cytotoxicity at a concentration below 1μM. The primary structure-activity relationships of the compounds were investigated, which laid the foundation for further research.All the podophyllotoxin derivatives were evaluated for their cytotoxic activitiy against three tumor cell lines that comprise HeLa, K562 and K562/A02, using etoposide as reference compound by the standard MTT method. The result showed that coumpond G-8 displayed the most potent cytotoxicity against all tumor cells lines, which was superior to that of etoposide. The cytotoxicity of coumpond G-8 against K562/A02 cell line has shown its positive result against etoposide resistant malignancies. Compound G-8 induced apoptosis in K562/A02 cell line and its influence on cell cycle was detected by flow cytometry. Flow cytometry suggested that G-8 could block cell cycle transition specifically at G2-M phase and induce apoptosis in a dose-dependent manner.We developed a facile method for the preparation of bis(indolyl)acetamides mediated by H2SO4 or HNO3 in THF. A reasonable mechanism for the above reaction is proposed.With microtubules as a target, several classes of small molecule tubulin inhibitors were designed and synthesised. The pharmacological results showed that some compounds exhibited promising antitumor potency. Among them, compounds SH-5, SH-9, SH-10 and G-8 displayed significant antitumor activity, and so they warrant the pursuit of additional research. The primary structure-activity relationships of the compounds were investigated, which laid the foundation for further research. Furthermore, We developed a facile method for the preparation of bis(indolyl)acetamides and a reasonable mechanism for this reaction is proposed.