Structural Insight and Development of EGFR Tyrosine Kinase Inhibitors

Lung cancer has a high prevalence, with a growing number of new cases and mortality every year. Furthermore, the survival rate of patients with non-small-cell lung carcinoma (NSCLC) is still quite low in the majority of cases. Despite the use of conventional therapy such as tyrosine kinase inhibitor for Epidermal Growth Factor Receptor (EGFR), which is highly expressed in most NSCLC cases, there was still no substantial improvement in patient survival. This is due to the drug’s ineffectiveness and high rate of resistance among individuals with mutant EGFR. Therefore, the development of new inhibitors is urgently needed. Understanding the EGFR structure, including its kinase domain and other parts of the protein, and its activation mechanism can accelerate the discovery of novel compounds targeting this protein. This study described the structure of the extracellular, transmembrane, and intracellular domains of EGFR. This was carried out along with identifying the binding pose of commercially available inhibitors in the ATP-binding and allosteric sites, thereby clarifying the research gaps that can be filled. The binding mechanism of inhibitors that have been used clinically was also explained, thereby aiding the structure-based development of new drugs.     

Lung Cancer: EGFR Inhibitors with Low Nanomolar Activity against a Therapy‐Resistant L858R/T790M/C797S Mutant

The treatment of non‐small‐cell lung cancer (NSCLC) with epidermal growth factor receptor (EGFR) inhibitors is made challenging by acquired resistance caused by somatic mutations. Third‐generation EGFR inhibitors have been designed to overcome resistance through covalent binding to the Cys 797 residue of the enzyme, and these inhibitors are effective against most clinically relevant EGFR mutants. However, the high dependence of these recent EGFR inhibitors on this particular interaction means that additional mutation of Cys 797 results in poor inhibitory activity, which leads to tumor relapse in initially responding patients. A new generation of irreversible and reversible mutant EGFR inhibitors was developed with strong noncovalent binding properties, and these compounds show high inhibitory activities against the cysteine‐mutated L858R/T790M/C797S EGFR.     

Targeted therapies for advanced non-small cell lung cancer

The incorporation of targeted agents has considerably improved the management of patients with advanced non-small cell lung cancer (NSCLC) over the last years. The main targets include the epidermal growth factor receptor (EGFR) and the vascular endothelial growth factor (VEGF). Currently available agents with established role in NSCLC include the anti-EGFR tyrosine-kinase inhibitors (TKIs) erlotinib/gefitinib and the anti-VEGF monoclonal antibody bevacizumab. Moreover, several other agents targeting critical pathways in lung carcinogenesis are currently under preclinical or clinical evaluation. This review presents an update on the role of targeted agents in advanced NSCLC. In addition, we present the main clinical studies investigating the activity of these agents in NSCLC and we provide recent data with respect to future therapeutic strategies.     

Tumor‐Targeting of EGFR Inhibitors by Hypoxia‐Mediated Activation

The development of receptor tyrosine‐kinase inhibitors (TKIs) was a major step forward in cancer treatment. However, the therapy with TKIs is limited by strong side effects and drug resistance. The aim of this study was the design of novel epidermal growth factor receptor (EGFR) inhibitors that are specifically activated in malignant tissue. Thus, a Co^III‐based prodrug strategy for the targeted release of an EGFR inhibitor triggered by hypoxia in the solid tumor was used. New inhibitors with chelating moieties were prepared and tested for their EGFR‐inhibitory potential. The most promising candidate was coupled to Co^III and the biological activity tested in cell culture. Indeed, hypoxic activation and subsequent EGFR inhibition was proven. Finally, the compound was tested in vivo, also revealing potent anticancer activity.     

Systematic profiling of chemotherapeutic drug response to EGFR gatekeeper mutation in non-small cell lung cancer

The epidermal growth factor receptor (EGFR) targeted therapy has been established as a routine strategy for treating non-small cell lung cancer (NSCLC). However, the gatekeeper mutation T790M in EGFR active site can confer generic resistance to tyrosine kinase inhibitors (TKIs), largely limiting the clinical applications of chemotherapeutic drugs in NSCLC. Here, a combined method of computational analysis and growth inhibition assay was described to systematically investigate the molecular response profile of wild-type–sparing and mutant-resistant inhibitors to the EGFR T790M mutation. The profile is highly consistent with previous clinical observations; three first-line chemotherapeutic drugs Gefitinib, Erlotinib and Lapatinib are established with acquired resistance upon the mutation. In addition, it was found that the alkaloid compound K252a, a Staurosporine analog isolated from Nocardiopisis sp., can selectively target the EGFR T790M mutant over wild-type kinase (23-fold selectivity), suggesting that the compound is good lead candidate for development of T790M mutant-selective inhibitors. Structural analysis revealed that the mutation-resulting Met790 residue does not induce steric hindrance to the EGFR T790M–K252a complex system, while a number of hydrophobic forces, van der Waals contacts and S⋯π interactions are observed between the aromatic rings of K252a and the sulfhydryl group of Met790, contributing considerable stabilization energy to the system.     

Globally Approved EGFR Inhibitors: Insights into Their Syntheses,Target Kinases,Biological Activities,Receptor Interactions,and Metabolism

Targeting the EGFR with small-molecule inhibitors is a confirmed valid strategy in cancer therapy. Since the FDA approval of the first EGFR-TKI, erlotinib, great efforts have been devoted to the discovery of new potent inhibitors. Until now, fourteen EGFR small-molecule inhibitors have been globally approved for the treatment of different types of cancers. Although these drugs showed high efficacy in cancer therapy, EGFR mutations have emerged as a big challenge for these drugs. In this review, we focus on the EGFR small-molecule inhibitors that have been approved for clinical uses in cancer therapy. These drugs are classified based on their chemical structures, target kinases, and pharmacological uses. The synthetic routes of these drugs are also discussed. The crystal structures of these drugs with their target kinases are also summarized and their bonding modes and interactions are visualized. Based on their binding interactions with the EGFR, these drugs are also classified into reversible and irreversible inhibitors. The cytotoxicity of these drugs against different types of cancer cell lines is also summarized. In addition, the proposed metabolic pathways and metabolites of the fourteen drugs are discussed, with a primary focus on the active and reactive metabolites. Taken together, this review highlights the syntheses, target kinases, crystal structures, binding interactions, cytotoxicity, and metabolism of the fourteen globally approved EGFR inhibitors. These data should greatly help in the design of new EGFR inhibitors.     

Insight into the Inhibition of Drug‐Resistant Mutants of the Receptor Tyrosine Kinase EGFR

Targeting acquired drug resistance represents the major challenge in the treatment of EGFR‐driven non‐small‐cell lung cancer (NSCLC). Herein, we describe the structure‐based design, synthesis, and biological evaluation of a novel class of covalent EGFR inhibitors that exhibit excellent inhibition of EGFR‐mutant drug‐resistant cells. Protein X‐ray crystallography combined with detailed kinetic studies led to a deeper understanding of the mode of inhibition of EGFR‐T790M and provided insight into the key principles for effective inhibition of the recently discovered tertiary mutation at EGFR‐C797S.     

Pharmacophore modelling,molecular docking and virtual screening for EGFR (HER 1) tyrosine kinase inhibitors

A pharmacophore model has been developed using diverse classes of epidermal growth factor receptor (EGFR) tyrosine kinase (TK) inhibitors useful in the treatment of human tumours. Among the top 10 generated hypotheses, the second hypothesis, with one hydrogen bond acceptor, one ring aromatic and three hydrophobic features, was found to be the best on the basis of Cat Scramble validation as well as test set prediction (r _training?=?0.89, r _test?=?0.82). The model also maps well to the external test set molecules as well as clinically active molecules and corroborates the docking studies. Finally, 10 hits were identified as potential leads after virtual screening of ZINC database for EGFR TK inhibition. The study may facilitate the designing and discovery of novel EGFR TK inhibitors.     

利用多克隆抗体有效识别中草药中抗表皮生长因子抑制剂

用一种已知的抗表皮生长因子受体抑制剂 (piceatannol) 作为半抗原与载体牛血清白蛋白 (BSA) 连接后免疫制备相应的多克隆抗体 (PcAb).利用该多克隆抗体来模拟酶制成亲和色谱柱，从一种藏药粗提物中将包括该半抗原在内的几种结构不同的抗表皮生长因子受体抑制剂识别出来.研究采用前沿亲和色谱-质谱联用技术对样品进行分析，可以直接从中药复杂体系中识别出有效成分并进行鉴定，实现中药有效成分的筛选与鉴定一体化技术.     

Discovery of a Highly Potent and Broadly Effective Epidermal Growth Factor Receptor and HER2 Exon 20 Insertion Mutant Inhibitor

Exon 20 insertion (Ex20Ins) mutations are the third most prevalent epidermal growth factor receptor (EGFR) activating mutation and the most prevalent HER2 mutation in non‐small cell lung cancer (NSCLC). Novel therapeutics for the patients with Ex20Ins mutations are urgently needed, due to their poor responses to the currently approved EGFR and HER2 inhibitors. Here we report the discovery of highly potent and broadly effective EGFR and HER2 Ex20Ins mutant inhibitors. The co‐crystal structure of compound 1 b in complex with wild type EGFR clearly revealed an additional hydrophobic interaction of 4‐fluorobenzene ring within a deep hydrophobic pocket, which has not been widely exploited in the development of EGFR and HER2 inhibitors. As compared with afatinib, compound 1 a exhibited superior inhibition of proliferation and signaling pathways in Ba/F3 cells harboring either EGFR or HER2 Ex20Ins mutations, and in the EGFR P772_H773insPNP patient‐derived lung cancer cell line DFCI127. Our study identifies promising strategies for development of EGFR and HER2 Ex20Ins mutant inhibitors.     

Short communication for targeting natural compounds against HER2 kinase domain as potential anticancer drugs applying pharmacophore based molecular modelling approaches- part 2

Breast cancer is one of the common causes of death noticed in women globally. In order to find effective therapeutics, the current investigation has focussed on identifying candidate compounds for EGFR and HER2. Accordingly, the pharmacophore modelling approaches were adapted to identify two prospective compounds and were docked against the target 3RCD that is complexed with TAK-285 a known dual inhibitor. Focussing on the target 3RCD, our results have showed that the compounds have demonstrated a good binding affinity towards the target occupying the binding pocket. They have established key residue interactions with stable molecular dynamics simulation results. The Hit compounds have demonstrated a potential to penetrate the blood brain barrier thereby enriching their therapeutics towards breast cancer brain metastasis. Taken together, our findings propose two candidate compounds as EGFR/HER2 inhibitors that might serve as novel chemical spaces for designing and developing new inhibitors.     

Synthesis,Characterization and Biological Activity of Tetrahydrobenzo[4,5]thieno[2,3-d]pyrimidine Derivatives as Epidermal Growth Factor Receptor Inhibitors

Based on the molecular docking studies, which were performed to position Erlotinib and the target compounds into the active site of the epidermal growth factor receptor(EGFR) to determine the probable binding model, a novel series of 5,6,7,8-tetrahydrobenzo[4,5]thieno[2,3-d]pyrimidine derivatives as the novel potential EGFR kinase inhibitors was designed and synthesized. The antitumor activity of all the target compounds against human pulmonary carcinoma cell line A549 has been screened. Of all the target compounds, 4-[2-(1-piperidyl)carbonylmethoxyl- phenthio]-5,6,7,8-tetrahydrobenzo[4,5]thieno[2,3-d]pyrimidine(7j) demonstrated the most potent antitumor activity. Several of the target compounds exhibited moderate antitumor activity. The preliminary structure-activity relationships of some target compounds were summarized.     

Emerging Therapeutic Agents for Colorectal Cancer

There are promising new therapeutic agents for CRC patients, including novel small-molecule inhibitors and immune checkpoint blockers. We focused on emerging CRC’s therapeutic agents that have shown the potential for progress in clinical practice. This review provides an overview of tyrosine kinase inhibitors targeting VEGF and KIT, BRAF and MEK inhibitors, TLR9 agonist, STAT3 inhibitors, and immune checkpoint blockers (PD1/PDL-1 inhibitors), for which recent advances have been reported. These new agents have the potential to provide benefits to CRC patients with unmet medical needs.     

EGFR酪氨酸激酶抑制剂的药效团模型构建

以80个作用方式相同, 分子结构特征不同的表皮生长因子受体酪氨酸激酶(EGFR TK)竞争性抑制剂为训练集, 利用计算机药物辅助软件Catalyst, 构建不同的药效团模型, 并结合酪氨酸激酶的作用位点等因素, 筛选出一个含有两个芳环中心, 一个疏水中心和一个阳离子基团的具有较好预测能力(RMS=0.438, Correl=0.908, Weight=1.52, Config=17.36)的药效团模型, 为设计和合成新型结构的EGFR TK抑制剂提供参考.     

Chemical genomic and proteomic methods for determining kinase inhibitor selectivity

The clinical success of the Bcr-Abl tyrosine kinase inhibitor Gleevec((R)) and the recent clinical approval of a number of small molecule drugs that target protein kinases have intensified the search for novel protein kinase inhibitors. Since most small molecule kinase inhibitors target the highly conserved ATP-binding pocket of this enzyme family, the target selectivity of these molecules is a major concern. Due to the large size of the human kinome, it is a formidable challenge to determine the absolute specificity of a given protein kinase inhibitor, but recent technological developments have made substantial progress in achieving this goal. This review summarizes some of the most recent experimental techniques that have been developed for the determination of protein kinase inhibitor selectivity. Special emphasis is placed on the results of these screens and the general insights that they provide into kinase inhibitor target selectivity.     

Molecular dynamics and pharmacophore modelling studies of different subtype (ALK and EGFR (T790M)) inhibitors in NSCLC

Extensively validated 3D pharmacophore models for ALK (anaplastic lymphoma kinase) and EGFR (T790M) (epithelial growth factor receptor with acquired secondary mutation) were developed. The pharmacophore model for ALK (r² = 0.96, q² = 0.692) suggested that two hydrogen bond acceptors and three hydrophobic groups arranged in 3-D space are essential for the binding affinity of ALK inhibitors. Similarly, the pharmacophore model for EGFR (T790M) (r² = 0.92, q² = 0.72) suggested that the presence of a hydrogen bond acceptor, two hydrogen bond donors and a hydrophobic group plays vital role in binding of an inhibitor of EGFR (T790M). These pharmacophore models allowed searches for novel ALK and EGFR (T790M) dual inhibitors from multiconformer 3D databases (Asinex, Chembridge and Maybridge). Finally, the eight best hits were selected for molecular dynamics simulation, to study the stability of their complexes with both proteins and final binding orientations of these molecules. After molecular dynamics simulations, one hit has been predicted to possess good binding affinity for both ALK and EGFR (T790M), which can be further investigated for its experimental in-vitro/in-vivo activities.     

4-苯胺喹唑啉类化合物合成研究进展

4-苯胺喹唑啉类化合物是一类具有广泛药理活性的喹唑啉类生物碱,在酪氨酸激酶受体(EGFR)抑制剂的研发中具有重要的作用。已经上市的此类药物有吉非替尼(gefitinib)和厄洛替尼(erlotinib)等。此类化合物的合成都是经过喹唑啉酮中间体或直接环合成4-苯胺喹唑啉。苯甲醛及其衍生物被用作反应原料,两种合成路线都要经历对苯甲醛的硝化及硝基的还原两步反应。笔者经查阅资料,设计并验证了以苯胺为原料、经靛红中间体得到4-苯胺喹唑啉类化合物的新的合成路线。本文依据这两种合成策略综述了4-苯胺喹唑啉类化合物的合成方法,并对各种方法的优缺点进行了总结,为进一步研究4-苯胺喹唑啉合成及设计具有药理活性的新化合物提供参考。     

用作HIV-1融合抑制剂的多肽及其类似物

HIV-1通过其包膜糖蛋白跨膜亚基gp41介导的病毒-细胞膜融合进入和感染靶细胞.HIV-1融合抑制剂以gp41为靶点,通过阻断病毒与宿主细胞膜的融合,在感染的初始环节切断HIV-1的复制周期.2003年,首个多肽类融合抑制剂T-20获美国食品药物管理局（FDA）批准上市,但其易被体内蛋白酶降解、临床剂量大、耐受性差,且耐药性HIV-1毒株也很快出现.针对这些缺点,近年来在融合抑制剂的作用机制研究和新融合抑制剂的研发等方面取得了重要进展.以gp41不同功能区为靶点,具有高活性和更好代谢性质的多肽及多肽类似物候选分子不断被发现,成为抗HIV药物研究领域的热点之一.本文综述了多肽和类肽类融合抑制剂的研究进展,为相关的药物开发和基础研究提供参考.