設計與合成瑞樂沙衍生物以對抗流感病毒 之神經胺酸酶

Design and Synthesis of Zanamivir Derivatives against Influenza Virus Neuraminidase

溫文賢(Wen-Hsien Wen)

指導教授 ： 方俊民

國立臺灣大學/理學院/化學研究所/博士(2009年)

https://doi.org/10.6342/NTU.2009.01652

摘要

流感在人類健康的危害上一直都是很嚴重的問題，特別是近幾年世界各地陸續傳出疫情的 H5N1 禽流感以及最近爆發的新型 H1N1 流感 (豬流感)，都有可能造成全球的大傳染。克流感與瑞樂沙是現階段常用來抑制流感的藥物，其主要的抑制目標為流感病毒表面的一種醣蛋白⎯神經胺酸酶。神經胺酸酶可以切斷感染細胞表面受體末端的唾液酸，而使得子代病毒順利的脫離細胞表面而繼續感染其它宿主細胞，不過最近已經發現對此類抑制劑具有抗藥性的病毒株出現，特別是最常用的克流感。雖然瑞樂沙對於抗藥性的病毒株還是具有不錯的抑制能力，但是瑞樂沙最主要的問題是生物利用度不佳，無法口服而用鼻腔噴灑，造成使用上的不便，所以對於修飾瑞樂沙進而增進它的口服性以及療效的研究則持續在進行當中。本論文則是設計與合成一系列的瑞樂沙衍生物進而開發出更有效的抗流感藥物。
第一部份: 由於神經胺酸酶 (N1 group) 其活性中心附近還多了一塊可以參與鍵結的區域 (150−cavity)，此區域提供了開發新型抑制劑的設計平台，於此我們設計並合成出了一系列的瑞樂沙衍生物 12−24，這些衍生物在它們四號位置的 guanidino group 上修飾了一些不同的取代基，在這些化合物之中， 如所預期的，化合物 12 的確可以跟開放式構形 N1 cavity−150 產生新的作用力，其活性 IC50 = 2.15 μM, EC50 = 0.77 μM，為了增進活性我們考慮減低藥物分子本身的熵而設計出新的目標分子 65，不過由於側鏈上碳碳雙鍵的影響，在合成上我們無法順利的獲得。
第二部份: 光動力療法在癌細胞上的應用已非常的廣泛，近幾年來更有關於殺死微生物的報導出現，於是，我們成功的設計並合成出有修飾 Zanamivir 的紫質光敏劑 79−81，這些光敏劑也是四價型的抑制劑，雖然這些抑制劑在抑制 NA 的活性上比單價的 Zanamivir 要來的差ㄧ些些，不過在抗病毒上卻增進了近百倍，除了多價效應的原因外，另一個原因是在病毒表面高濃度的紫質，其在照光下能夠有效地殺死流感病毒，由於這些化合物上所修飾的 Zanamivir 能夠與病毒表面的 NA 產生強大的親和力，才使得紫質可以大量的累積在病毒表面並讓其所產生的單態氧可以順利的對表面的 NA 造成傷害，以更強的光度 (10,000 Lux) 照射30 分鐘下，只要 30 pM 的化合物 81 就可以殺死 95%的病毒，我們也證實了病毒表面的 NA 在自由基的攻擊之下會相互共價鍵結 (cross-linking) 成二聚體或更高分子量的多聚體。
第三部份: 在藥物設計上磷酸根常常用來當作羧酸根的生物等配物 (bioisoster)， 對於 guanidinium ion 的分子間作用力，磷酸根會比羧酸根還來的強，在 2007 年中研院基因體中心所製備出的零流感 (Tamiphosphor) 比克流感有更佳的抑制活性 (Ki = 0.15 nM)，於是我們就利用相同的概念設計出瑞樂沙的磷酸類似物 116，並且去分析此化合物的可能合成路徑，我們嘗試了利用金屬銦或碘分子的方法，不過都無法有效的獲得預期產物，最後我們發現也許可以利用唾液酸的 δ-內酯 134 為起始物，然後在兩種不同的策略下建構出所想要的磷酸衍生物。
第四部份: 我們成功的設計並合成出以 Zanamivir 為鍵結端的感測分子 142、143，化合物 142 的訊號輸出端為 Dansyl 螢光團，化合物 143 的訊號輸出端為生物素。利用感測分子 143，我們可以證實修飾 Zanamivir 的分子都可以有效的聚集在含有 NA 的病毒或細胞表面，這類感測分子除了應用在流感病毒的偵測、純化或分析以及抗流感藥物的高速藥物篩選和 NA 與抑制劑劑的藥物動力學外，如何利用 Zanamivir 與 NA 專一性的親和力，使其應用在細胞生物學的研究與藥物傳導的開發上，也是我們接下來的目標。

關鍵字

流感病毒 ； 神經胺酸酶瑞樂沙 ； 光動力療法

並列摘要

Influenza remains a major health problem. The worldwide occurrences of the fatal H5N1 avian flu and the recent outbreak of the new type H1N1 flu (swine flu) have increased public awareness of the potential global influenza pandemics. Oseltamivir phosphate and zanamivir are popular drugs for the treatment of influenza. Both drugs inhibit influenza virus propagation by cleaving the linkage between the progeny virus from the surface sialo-receptor of host cells. However, the emergence of drug-resistant influenza viruses has also caused another problem in medical treatment. In comparison, oseltamivir phosphate is more susceptible to the newly evolved resistant viruses than zanamivir. However, zanamivir is made in powder for administration by nasospray in low bioavailability, thus modification of zanamivir to improve its therapeutic use has been pursued. In this thesis, we designed and synthesized novel zanamivir derivertives to improve activities against influenza virus.
Part I: Based on the report that N1 neuraminidase contains a cavity adjacent to their active site that closes on ligand binding, we designed and synthesized a series of zanamivir derivatives 12−24 possessing substituents on 4-guanidino groups. Among these compounds, compound 12 exhibited the best inhibitoin against influenza (IC50 = 2.15 μM, EC50 = 0.77 μM). In order to improve the activity, we designed 65, an analog of 12 with reduced entropy, as a new inhibitor. So far, we have been unable to synthesize 65 due to its highly reactive carbon−carbon double bond.
Part II: We prepared several zanamivir analogs 79−81 by conjugation of zanamivir with porphyrin in a ratio of 4:1. These analogs in general are less potent than zanamivir in inhibition of influenza virus neuraminidase, but they are significantly more potent than zanamivir in inhibition of the proliferation of influenza viruses. The enhanced anti-influenza properties of these analogs are thought to be due to the synergistic effect on neuraminidase inhibition and viral inactivation. The influenza virus inactivation is contributable to porphyrin, which is brought to close proximity of viral particle by the binding of Zanamivir with neuraminidase, to generate cytotoxic singlet oxygen to destruct the virus on irradiation (850 Lux). After illumination of influenza viruses for 0.5 h by stronger LED light (10,000 Lux), in the presence of 81 at 30 pM, the influenza virus titer is reduced by 95%. We also confirm that influenza virus neuraminidase undergoes cross-linking to generate dimeric or aggregate of high molecular weight by photo-sensitization of 81.
Part III: The phosphonate group is generally used as a bioisoster of carboxylate in drug design. In comparison with the carboxylate−guanidinium ion pair, a phosphonate ion exhibits stronger electrostatic interactions with the guanidinium ion. In 2007, Shie and coworkers has synthesized Tamiphosphor, the phosphonate congener of Tamiflu , to show better anti-influenza activity than GS4071. We thus aim to synthesize a target compound 116, which is a phosphonate analog of zanamivir by different approaches. So far, synthesis of 116 using indium-mediated allylation or iodine-promoted phosphorylation is unsatisfactory. On the other hand, using sialo-lactone 134 as a precursor may be a better strategy to prepare the target compound 116.
Part IV: We have successfully prepared the zanamivir−dansyl conjugate 142 and zanamvir−biotin conjugate 143 as novel sensor molecules. We have demonstrated that 143 has high affinity with influenza virus neuraminidase and is localized on the surface of virus-infected cells. Conjugates 142 and 143 may be used in detection, purification, analysis and high-throughtput screening of neuraminidase as well as in neuraminidase kinetic study. Furthermore, we believe that the high affinity between zanamivir conjugate and neuraminidase may be applied to study the subjects in cell biology and drug delivery.

並列關鍵字

influenza virus ； neuraminidase ； zanamivir ； PDT

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