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A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the Degree of Doctor of Philosophy Submitted June 2016. / The work detailed in this PhD involves two distinct, separate areas of research. The first project involved an investigation into the synthesis, characterisation and metal-chelation of pyrido-imidazo[1,2-a]pyridines in the search for new compounds for the treatment of cancer. Previously in our laboratories at the University of the Witwatersrand a small library of imidazo[1,2-a]pyridines were synthesized that showed significant activity (IC50 values between 6.57-21.98 μM) against Caco-2 and HT-29 colorectal cancer cell lines while showing little cytotoxicity towards white blood cells; significantly less than camptothecin the ‘golden standard’. In an attempt to improve the overall activity of the imidazo[1,2-a]pyridines methodology was developed to coordinate zinc, copper and platinum to the imidazo[1,2-a]pyridines to generate novel metal-imidazo[1,2-a]pyridine complexes. These novel compounds were characterised by NMR spectroscopy (where possible) and Single Crystal X-ray Diffraction (SCXRD) and tested against colorectal (Caco-2 and HT-29), leukemic (K562 and HL-60) and breast (MCF-7 and MDA-MB231) cancer cell lines, where the copper-containing compounds showed the most significant activity. A library of 11 copper complexes screened showed excellent activity in all the cell lines tested, some of which were more active than camptothecin. The second part of this PhD involved a detailed investigation into novel methodology to synthesize xanthones and related diones, for example such as 4a-methoxy-2H-xanthene-2,9(4aH)-dione, discovered in our laboratory. Initially this reaction was reported to be mediated by ceric ammonium nitrate (CAN), however it was determined during the course of this investigation that the novel reaction was actually mediated by ceric ammonium sulfate (CAS) and that different products were isolated depending on which reagent (CAN or CAS) was used. In this thesis, the mechanism of the reaction was probed and it was determined that the electronic nature of the starting benzophenone (e.g. (2-hydroxyphenyl)(2,4,6-trimethoxyphenyl)methanone) plays a crucial role in the outcome of the reaction. In addition to the furnishing of xanthones (e.g. 4-methoxy-9H-xanthen-9-one) and spirofurans (such as 2',6'-dimethoxy-3H-spiro[benzofuran-2,1'-cyclohexa[2,5]diene]-3,4'-dione) using this CAS-mediated reaction, novel biaryl-fused dimers (e.g. (4,4'-dihydroxy-[1,1'-biphenyl]-3,3'-diyl)bis((2,4-dimethoxyphenyl)methanone)) were also isolated and these results were explained by the mechanisms detailed in this work. Reliable methodology was developed using a sodium dithionite-mediated method for the conversion of dione products (such as 4a-methoxy-2H-xanthene-2,9(4aH)-dione) to hydroxy-containing xanthones (such as 7-hydroxy-9H-xanthen-9-one). iv Finally, as a proof of concept, this novel CAS-mediated methodology was extended to the synthesis of the nitrogen-containing derivatives, the acridones, and a single acridone, 10-benzyl-2-methoxyacridin-9(10H)-one, was successfully synthesized using CAS as the reagent, albeit in a low yield. / LG2017

University of Macau / Faculty of Health Sciences

University of Macau / Institute of Chinese Medical Sciences

University of Macau / Faculty of Health Sciences

University of Macau / Faculty of Health Sciences

published_or_final_version / Medical Sciences / Master / Master of Medical Sciences

With the recent advances in the knowledge of hepato-carcinogenesis, there has been encouraging development in the molecular targeted therapy for patients with advanced hepatocellular carcinoma (HCC). Sorafenib, an anti-angiogenic multi-targeted receptor tyrosine kinase inhibitor, has become the standard of treatment in HCC patients with Child-Pugh A cirrhosis. Nevertheless, the benefits and safety profile of sorafenib in the majority of the unselected advanced HCC patients and other patient subgroups are still unclear. More importantly, the survival benefit associated with sorafenib use is generally modest in Asian population. Therefore, an unmet medical need remains for more effective therapeutic agents. This thesis studied the impact of molecular targeted therapy in the treatment of advanced HCC patients and it contains 10 original studies divided into six sections. The first section provides a concise overview of the epidemiology, risk factors, and current treatment options for HCC patients. Also, the molecular biology and opportunity for the use of targeted therapy in advanced HCC were discussed. The second section is about a new prognostic score system that we developed — Advanced Liver Cancer Prognostic System (ALCPS). Our study results showed that ALCPS was able to objectively estimate the 3-month survival probability of advanced HCC patients and thus could enhance patient selection for targeted therapy or clinical trials. The third section is about the use of sorafenib in the treatment of advanced HCC patients. The results of our single centre phase II study showed that sorafenib had good efficacy and acceptable tolerability in treating advanced HCC patients in hepatitis B endemic area. Furthermore, our retrospective study results confirmed that the overall survival benefits and overall treatment-related adverse events of sorafenib were comparable in elderly and young advanced HCC patients. More importantly, our other retrospective analysis showed that Child-Pugh (CP) A and CP B patients tolerated sorafenib similarly and derived similar clinical and progression-free survival benefit. Among CP B patients, most benefits were observed in patients with score 7. Nevertheless, CP B patients were more susceptible to developing cirrhotic complications. Last but not least, our study also demonstrated that drop in serum alpha-fetoprotein level > 20% in the first 6 weeks of sorafenib treatment was a useful early surrogate endpoint for evaluating antitumor response and survival benefits. All these results are instrumental in guiding future rational use of sorafenib in advanced HCC population. The fourth section is about the role of targeted therapies in treating sorafenib-refractory advanced HCC patients. In a single arm phase II study, we showed that bevacizumab and erlotinib combination was not effective in treating advanced HCC patients who had failed prior sorafenib treatment. The fifth section of the thesis comprises results of four early phase novel clinical trials that may potentially improve the therapeutic outcomes in advanced HCC patients. First, our phase I/II study demonstrated that another anti-angiogenic agent — PTK787 had encouraging and possible synergistic activity when combined with intravenous doxorubicin in treating advanced HCC patients. Second, our multi-center phase II study results demonstrated promising activity with good tolerability of a novel combination — sorafenib together with capecitabine and oxaliplatin (SECOX) in the treatment of advanced HCC patients. Third, in a phase I study, we showed that pazopanib, a novel anti-angiogenic agent, had a manageable safety profile and preliminary activity in advanced HCC patients. Moreover, pazopanib reduced tumor vessel leakage, as shown by contrast-enhanced magnetic resonance imaging indicating a direct effect on HCC vasculature that might be associated with its antitumor activity. Lastly, in another phase I study, we evaluated safety, pharmacological parameters, and potential antitumor activity of pegylated recombinant human arginase 1 (peg-rhArg1) in advanced HCC patients. Our results illustrated that arginine depletion in humans can be achieved safely with peg-rhAgr1 in a dose-response manner and peg-rhArg1 had manageable safety profile and preliminary evidence of activity in advanced HCC patients. In the last section, the future perspectives about the use of molecular targeted therapy in the treatment of advanced HCC patients were discussed. / published_or_final_version / Medicine / Master / Doctor of Medicine

Hepatocellular Carcinoma (HCC) the fifth most common cancer and the third leading cause of death among cancer worldwide. Curative treatments such as liver resection and liver transplantation are generally used in treating early-stage HCC patients. However, only 10% to 30% of HCC patients are eligible for the surgery, which is due to the asymptomatic characteristic of HCC, most HCC patients are diagnosed at late stage. Palliative treatment such as TAE, TACE and Sorafenib provide them options to maintain their quality of life and extend their survival. Nevertheless, current treatments provides limited benefits to them as efficacy remains unsatisfactory. Therefore, there is a great need to develop new palliative treatments and explore new agents for the treatment of HCC. The aim of this study is to investigate the efficacy of a new therapeutic agent, Ombrabulin, in the treatment of HCC. Angiogenesis in HCC has been well-studied for many years as many studies proved that angiogeneisis plays an important role in the progression and development of HCC. Angiogenesis can also affect the prognosis and efficacy of treatments in HCC. As a result, antiangiogenesis and vascular disrupting agents have become new target in the therapaies of HCC. Ombrabulin is a synthetic vascular disrupting agent, which can inhibit tubulin polymerization in endothelial cells, causing cytoskeleton disorganization in endothelial cells. Endothelial cells will then detach from the basement membrane and eventually lead to vascular shutdown. This study demonstrated for the first time that Ombrabulin could selectively inhibit human umbilical vein endothelial cell (HUVEC) growth in vitro; particularly the early-form of HUVEC, which represent immature endothelial cell in neovasculature. Furthermore, this study also demonstrated the antiangiogenic effect of Ombrabulin on endothelial cells. By F-actin staining, it was shown that Ombrabulin caused changes in HUVECs morphology, which supported that Ombrabulin could lead to distortion in cytoskeleton. In vivo study demonstrated the early effect and long term effect of Ombrabulin. For the first part of the in vivo study, Nude mice were treated with single-dose of Ombrabulin for one week. Hoechst 33342, anti-CD34 staining and PCNA staining were carried out to study the functional effect of Ombrabulin and the combination effect with Sorafenib in vivo. Mice treated with Ombrabulin resulted in decreased blood perfusion, microvessel density and tumor cell proliferation, and tumor necrosis was also observed. In the combination with Sorafenib, it did not show synergistic effect in both tumor cell proliferation and microvessel density. For the second part of the in vivo study, nod scid mice were treated with multiple doses of Ombrabulin for three weeks to study the long term effect of Ombrabulin. Mice treated with Ombrabulin resulted in significantly smaller tumor size, demonstrating its antitumor efficacy in HCC. Furthermore, combination treatment of Sorafenib and Ombrabulin in vivo could enhance the efficacy of the treatment of HCC. In conclusion, Ombrabulin has vascular disrupting and antitumor effects, which could efficiently suppress HCC tumor growth in vivo. These results suggest that Ombrabulin could be a promising vascular disrupting agent in treating HCC. Combination with sorafenib should be further explored in clinical studies to demonstrate the synergistic antitumor effects in HCC patients. / published_or_final_version / Surgery / Master / Master of Philosophy

abstract / Anatomy / Doctoral / Doctor of Philosophy