Comparing HTS with Fragment-Based Design for B-Raf and the Ras-Raf Interaction

描述（由申请人提供）：我们建议使用计算建模、生物物理NMR研究和生物化学测定来比较常规高通量筛选（HTS）方法与新的集成配体设计策略的有效性。我们将比较这两种方法对两个目标的有效性-一个传统的激酶（B-Raf）和K-Ras和B-Raf之间具有挑战性的蛋白质-蛋白质相互作用。K-Ras是癌症生物学中最重要的癌蛋白。Ras癌蛋白（K-Ras、H-Ras、N-Ras）在30多年前被发现，但对小分子药物的直接靶向具有抗性。因此，尽管KRAS基因在约20%的所有肿瘤和>60%的胰腺癌中突变，但没有治疗突变KRAS肿瘤的疗法。效应蛋白（Raf蛋白、PI 3 K蛋白和Ral-GDS等）的K-Ras活化通过K-Ras上的开关I区介导，其与B- Raf和其他效应蛋白的Ras结合结构域形成延伸的β折叠。破坏这种蛋白质-蛋白质相互作用的抗体逆转Ras诱导的动物肿瘤形成。因此，这种相互作用的小分子抑制剂可能是含有突变KRAS的肿瘤的有用治疗剂。如果我们证明这种新的设计方法与标准HTS相比更有效，它将对发现针对目前不可用药的靶蛋白的小分子抑制剂的可能性产生深远的影响。因此，该项目可能导致第一种小分子疗法用于靶向具有突变K-Ras的肿瘤，并可能为小分子抑制开辟大量不可药物化的靶点。

DESCRIPTION (provided by applicant): We propose to compare the effectiveness of the conventional high-throughput screening (HTS) approach with a new integrated ligand design strategy using computational modeling, biophysical NMR studies and biochemical assays. We will compare the effectiveness of these two approaches against two targets-a conventional kinase (B-Raf) and a challenging protein-protein interaction between K-Ras and B-Raf. K-Ras is an oncoprotein of paramount importance of cancer biology. The Ras oncoproteins (K-Ras, H-Ras, N-Ras) were discovered over 30 years ago, but have been resistant to direct targeting with small molecule drugs. Thus, despite the fact that the KRAS gene is mutated in ~20% of all tumors, and >60% of pancreatic cancers, there is no therapy for treating mutant KRAS tumors. K-Ras activation of effector proteins (Raf proteins, PI3K proteins, and Ral-GDS, among others) is mediated through the switch I region on K-Ras, which forms an extended beta sheet with the Ras-binding domain of B- Raf and other effector proteins. An antibody that disrupts this protein-protein interaction reverses Ras-induced tumor formation in animals. Thus, a small molecule inhibitor of this interaction is likely to be a useful therapeutic for tumors containing mutant KRAS. If we demonstrate increased effectiveness of this new design approach compared to standard HTS, it will have a profound effect on the likelihood of small molecule inhibitor discovery against currently undruggable target proteins. This project could thus lead to the first small molecule therapeutics for targeting tumors with mutant K-Ras and may open up a large number of undruggable targets to small molecule inhibition.