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

描述（由申请人提供）：我们建议比较传统的高通量筛选（HTS）方法与一种新的集成配体设计策略的有效性，该策略使用计算建模，生物物理核磁共振研究和生化分析。我们将比较这两种方法对两种靶标的有效性，一种是常规激酶（B-Raf），另一种是K-Ras和B-Raf之间具有挑战性的蛋白-蛋白相互作用。K-Ras是一种在癌症生物学中至关重要的癌蛋白。Ras癌蛋白（K-Ras, H-Ras, N-Ras）是在30多年前发现的，但对小分子药物的直接靶向具有耐药性。因此，尽管KRAS基因在约20%的肿瘤中发生突变，在约60%的胰腺癌中发生突变，但目前还没有治疗突变KRAS肿瘤的方法。K-Ras激活效应蛋白（Raf蛋白、PI3K蛋白和Ral-GDS等）是通过K-Ras上的开关I区介导的，该开关I区与B- Raf和其他效应蛋白的ras结合域形成延伸的β片。一种破坏这种蛋白-蛋白相互作用的抗体可以逆转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一种有用的治疗含有突变KRAS的肿瘤的药物。如果我们证明与标准HTS相比，这种新设计方法的有效性有所提高，它将对发现针对目前无法药物的靶蛋白的小分子抑制剂的可能性产生深远的影响。因此，该项目可能会导致首个针对突变K-Ras肿瘤的小分子疗法，并可能为小分子抑制开辟大量不可药物的靶点。

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.