抑制腫瘤細胞轉移和成長的分子靶向性先導藥物研發---雜環類先導藥物的演化和多樣式的設計合成(II)

Abstract

本計劃延續之前第二期計畫的成果，發現代號Nstpbp001250 化 合物進入臨床前之抗癌動物實驗，以口服方式給予藥劑，委託汎球公 司(MDL)代為測試，測試結果發現Nstpbp001250 對於VEGFR-3 具有專 一的抑制性，而且沒有一般抗癌藥物強烈細胞的細胞毒性，此藥物可 以有效的抑制癌細胞的淋巴管增生，進而阻止癌細胞藉著利用淋巴管 增生轉移到遠端的器官，這個有機小分子具有一個全新的化學結 構，目前已經申請美國專利(US 11/949,070 PCT/US07/86220)，並希望 能在本次第三期將研究成果落實於產業界中。 組合式化學在前驅藥物的最佳化上，明顯的呈現優勢。利用具生 物活性的先導藥物分子前驅藥為主體，合成各種具有多樣取代基之產 物，藉著改變取代基上的官能基，產生各種不同組合的化合物，進而 有效率的建立化學分子庫，再經由高通量篩選出具有藥理活性的化合 物，提供作為臨床前之測試。目前我們已經利用這種新的策略，找到 全新化學結構的Nstpbp001250 化合物，在本計劃中，將以此先導藥 物做為基本的模板，進行化學分子結構的最佳化，同時進行對於 Nstpbp001250 化合物進行結構和活性之間的關係研究，試圖對其結 構進行最佳化以期望能找出更具有活性和選擇性的結構，去年我們成 功的合成並發現另一有機小分子Nstpbp00194 比Nstpbp001250 有近 4 倍的活性，未來更進一步的，我們將透過與其他結構生物學的實驗 室合作(如同步幅射中心的陳俊榮博士)，嘗試利用Nstpbp001250 化 學小分子和VEGFR-3 蛋白受體的共同結晶來清楚了解受體和藥物之 間的作用機制，並試圖利用其在活性位置的作用機制找尋其他更有效 的抑制抗癌細胞轉移的藥物。另外Nstpbp00194 的水溶性不佳，經過 新傳輸和配方的處理後，活性比原來高約十倍；最近幾個月內，我們 又發現四個全新的化合物(VEGFR3 的抑制率約為85 %) 均比先導 藥物Nstpbp001250 來得高(VEGFR3 的抑制率約為62 %)，這些令人 振奮的結果，都值得繼續往下發展，以期找到最適合，並有效的新藥。

Vascular endothelial growth factors (VEGFs) and their respective family of receptor tyrosine kinases (VEGFRs) are key proteins modulating angiogenesis, the formation of new vasculature from an existing vascular network. Potent, specific, and non-toxic inhibitors of angiogenesis are powerful clinical tools in oncology and ophthalmology. Signal blockade via VEGF receptors such as VEGFR-1 and VEGFR-2 leads to an inhibition of malignant angiogenesis. Recent report (Cancer Res. 2005, 65, 4389) describing small-molecule inhibitors affect VEGFR signaling by directly competing with the ATP-binding site of corresponding intracellular kinase domains. This cause leads to the inhibition of VEGFR phosphorylation and ultimately to the apoptotic death of the aberrant endothelial cells. In addition, VEGF-C played an important role in lymphangiogenesis via a mechanism of activating VEGF receptor 3 (VEGFR-3). VEGFR-3 has been proposed as a specific marker for lymphatic endothelial cells. Recent studies indicated that VEGFR-3 also expressed in a variety of human malignancies, including lung adenocarcinoma, colorectal adenocarcinoma, head and neck carcinoma, neuroblastoma, and Kaposi's sarcoma. The novel compound Nstpbp00194 was designed and identified in our laboratory last year, which is able to compete VEGF-C for VEGFR-3 to act as an antagonist. This compound is found more four times more potent than lead compound Nstpbp001250. Combinatorial chemistry is revolutionizing the process of drug discovery with outstanding properties. While the traditional principle focuses on the synthesis of one compound at a time, the novel combinatorial methodologies aim at the identification of one or a few very promising candidates through the parallel or mixture-based synthesis and screening of a multitude of compounds. Using this technique, we discovered a unique, potent lead molecule-Nstpbp001250 within one year. A general method of rapidly synthesizing analogues of 1250 scaffold would be greatly advantageous and warrants further investigation for drug discovery. In order to improve the antitumor profile of parent molecules, it is necessary to perform various synthetic modifications around the scaffolds. To further application, co-crystallization of VEFGR-3 with #1250 compound will be proceeded. Libraries compose of a diverse set of compounds can be possibly produced according to X-structure of co-crystallization. We will use in vitro screening software such as Cerius and Catalyst from MSI to design more focusing libraries, which exhibit the required diversity because effective design of the libraries could reduce the number of molecules made and tested without reducing their diversity.