Chronicles of EGFR Tyrosine Kinase Inhibitors: Targeting EGFR C797S Containing Triple Mutations

Epidermal growth factor receptor (EGFR) is a receptor tyrosine kinase widely expressed in many cancers such as non-small cell lung cancer (NSCLC), pancreatic cancer, breast cancer, and head and neck cancer. Mutations such as L858R in exon 21, exon 19 truncation (Del19), exon 20 insertions, and others are responsible for aberrant activation of EGFR in NSCLC. First-generation EGFR tyrosine kinase inhibitors (TKIs) such as gefitinib and erlotinib have clinical benefits for EGFR-sensitive (L858R and Del19) NSCLC patients. However, after 10-12 months of treatment with these inhibitors, a secondary T790M mutation at the gatekeeper position in the kinase domain of EGFR was identified, which limited the clinical benefits. Second-generation EGFR irreversible inhibitors (afatinib and dacomitinib) were developed to overcome this T790M mutation. However, their lack of selectivity toward wild-type EGFR compromised their clinical benefits due to serious adverse events. Recently developed third-generation irreversible EGFR TKIs (osimertinib and lazertinib) are selective toward driving mutations and the T790M mutation, while sparing wild-type EGFR activity. The latest studies have concluded that their efficacy was also compromised by additional acquired mutations, including C797S, the key residue cysteine that forms covalent bonds with irreversible inhibitors. Because second- and third-generation EGFR TKIs are irreversible inhibitors, they are not effective against C797S containing EGFR triple mutations (Del19/T790M/C797S and L858R/T790M/C797S). Therefore, there is an urgent unmet medical need to develop next-generation EGFR TKIs that selectively inhibit EGFR triple mutations via a non-irreversible mechanism.     

The epidermal growth factor receptor gene family as a target for therapeutic intervention in numerous cancers: what's genetics got to do with it?

Over the past 30 years, a relatively simple growth factor and its cognate receptor have provided seminal insights into the understanding of the genetic basis of cancer, as well as growth factor signalling. The epidermal growth factor (EGF), its cognate receptor (EGFR) and related family members have been shown to be important in normal, as well as the malignant growth of many cell types including: glioblastomata, astrocytomas, medulloblastomata, non-small cell lung carcinoma (NSCLC) and breast cancer. This review summarises the history of the EGFR gene and the v-ErbB oncogene, as well as diverse approaches developed to inhibit EGFR activity. The two most advanced therapies use either small-molecule cell membrane permeable kinase inhibitors or antibodies which prevent receptor activation. Recent clinical trials indicate that certain NSCLC patients have mutations in the EGFR gene which makes them more responsive to kinase inhibitors. These mutations appear to enhance the ability of the ligand to activate EGFR activity and also prolong the binding of the EGFR inhibitor to the kinase domain. Evidence to date suggests that these EGFR mutations in NSCLC occur more frequently in Japan than in the western hemisphere. Although these mutations are correlated with enhanced efficacy to the inhibitors in NSCLC, they can not explain or predict the sensitivity of many other cancer patients to the beneficial effects of the EGFR kinase inhibitors or antibody mediated therapy. As with as other small-molecule kinase inhibitors and susceptible diseases (e.g., imatinib and chronic myeloid leukaemia), resistance to EGFR inhibitors has been reported recently, documenting the requirement for development of multi-pronged therapeutic approaches. EGFR kinase inhibitors are also being evaluated as adjuvants in hormonal therapy of breast cancer - especially those which overexpress EGFR. Genetically engineered antibodies specific for the EGFR family member ErbB2 have been developed which show efficacy in the treatment of primary, and prevent the relapse of, breast cancer. Clearly, the EGF/EGFR signalling cascade has, and continues to play, an important role in the development of novel anticancer targeted therapies.     

Recent understanding of the molecular mechanisms for the efficacy and resistance of EGF receptor-specific tyrosine kinase inhibitors in non-small cell lung cancer

INTRODUCTION: The epidermal growth factor receptor (EGFR) and its family members are involved in many aspects of tumor biological processes. Aberrant activation of the EGFR tyrosine kinase by mutations or protein overexpression is observed in various types of human cancer, including lung cancer. EGFR tyrosine kinase inhibitors (EGFR-TKIs), such as gefitinib and erlotinib, are highly effective in lung cancer patients who harbor active mutations in the EGFR gene. However, patients who are initially sensitive to EGFR-TKIs eventually relapse within few years. AREAS COVERED: Non-small cell lung cancer (NSCLC) is the most common type of lung cancer and is associated with a high frequency of EGFR mutations. This review describes the EGFR mutations that determine the sensitivity to EGFR-TKIs and the current understanding of the molecular mechanisms of acquired resistance to EGFR-TKIs in NSCLC. Furthermore, the authors describe recent strategies developed to overcome acquired resistance using second-generation EGFR-TKIs and combination therapies with several molecular-targeting drugs. EXPERT OPINION: Although recent findings have contributed to our understanding of the mechanism of acquired resistance and helped the development of novel strategies to overcome such resistance, the underlying mechanisms are complex and additional research is necessary to develop effective therapeutic strategies for individual patients with lung cancer.     

The epidermal growth factor receptor gene family as a target for therapeutic intervention in numerous cancers: what’s genetics got to do with it?

Over the past 30 years, a relatively simple growth factor and its cognate receptor have provided seminal insights into the understanding of the genetic basis of cancer, as well as growth factor signalling. The epidermal growth factor (EGF), its cognate receptor (EGFR) and related family members have been shown to be important in normal, as well as the malignant growth of many cell types including: glioblastomata, astrocytomas, medulloblastomata, non-small cell lung carcinoma (NSCLC) and breast cancer. This review summarises the history of the EGFR gene and the v-ErbB oncogene, as well as diverse approaches developed to inhibit EGFR activity. The two most advanced therapies use either small-molecule cell membrane permeable kinase inhibitors or antibodies which prevent receptor activation. Recent clinical trials indicate that certain NSCLC patients have mutations in the EGFR gene which makes them more responsive to kinase inhibitors. These mutations appear to enhance the ability of the ligand to activate EGFR activity and also prolong the binding of the EGFR inhibitor to the kinase domain. Evidence to date suggests that these EGFR mutations in NSCLC occur more frequently in Japan than in the western hemisphere. Although these mutations are correlated with enhanced efficacy to the inhibitors in NSCLC, they can not explain or predict the sensitivity of many other cancer patients to the beneficial effects of the EGFR kinase inhibitors or antibody mediated therapy. As with as other small-molecule kinase inhibitors and susceptible diseases (e.g., imatinib and chronic myeloid leukaemia), resistance to EGFR inhibitors has been reported recently, documenting the requirement for development of multi-pronged therapeutic approaches. EGFR kinase inhibitors are also being evaluated as adjuvants in hormonal therapy of breast cancer – especially those which overexpress EGFR. Genetically engineered antibodies specific for the EGFR family member ErbB2 have been developed which show efficacy in the treatment of primary, and prevent the relapse of, breast cancer. Clearly, the EGF/EGFR signalling cascade has, and continues to play, an important role in the development of novel anticancer targeted therapies.     

Everolimus restores gefitinib sensitivity in resistant non-small cell lung cancer cell lines

The epidermal growth factor receptor (EGFR) is a validated target for therapy in non-small cell lung cancer (NSCLC). Most patients, however, either do not benefit or develop resistance to specific inhibitors of the EGFR tyrosine kinase activity, such as gefitinib or erlotinib. The mammalian target of rapamycin (mTOR) is a key intracellular kinase integrating proliferation and survival pathways and has been associated with resistance to EGFR tyrosine kinase inhibitors. In this study, we assessed the effects of combining the mTOR inhibitor everolimus (RAD001) with gefitinib on a panel of NSCLC cell lines characterized by gefitinib resistance and able to maintain S6K phosphorylation after gefitinib treatment.Everolimus plus gefitinib induced a significant decrease in the activation of MAPK and mTOR signaling pathways downstream of EGFR and resulted in a growth-inhibitory effect rather than in an enhancement of cell death. A synergistic effect was observed in those cell lines characterized by high proliferative index and low doubling time. These data suggest that treatment with everolimus and gefitinib might be of value in the treatment of selected NSCLC patients that exhibit high tumor proliferative activity.     

Is there a role for dacomitinib,a second-generation irreversible inhibitor of the epidermal-growth factor receptor tyrosine kinase,in advanced non-small cell lung cancer?

ABSTRACT

Introduction

Non-small cell lung cancer (NSCLC) is a highly lethal disease. During the past 20 years, the epidermal growth factor receptor (EGFR) has been a relevant target for anticancer drug-design, and a large family of EGFR tyrosine kinase inhibitors (TKI) were designed, which improved therapeutic outcomes compared to conventional chemotherapy in NSCLC patients with specific EGFR mutations. However, resistance to these inhibitors occurs; therefore, the debate on which inhibitor should be used first is still open. Dacomitinib was approved in 2018 for the first-line treatment of NSCLC with EGFR activating mutations.     

Review. EGFR mutations in non-small cell lung cancer--clinical implications

The epidermal growth factor receptor (EGFR) family members seem to play a critical role in lung tumourigenesis and are overexpressed in 40-80% of non-small cell lung carcinoma (NSCLC) tumours. EGFR activation results in a series of downstream signaling events that mediate cancer cell growth, proliferation, motility, adhesion, invasion, apoptosis inhibition and metastasis as well as resistance to chemotherapy. Therefore, EGFR inhibitors seem to be an effective therapy for some patients with previously treated NSCLC. A thorough investigation of EGFR, its major signaling pathways, its identification and biology in NSCLC and the responsiveness to gefitinib, erlotinib and cetuximab in connection to EGFR mutations as well as the possible mechanisms of resistance to tyrosine kinase inhibitors is the scope of this review.     

Second-generation epidermal growth factor tyrosine kinase inhibitors in non-small cell lung cancer

Inhibiting the tyrosine kinase activity of the epidermal growth factor receptor (EGFR) has an established role in the treatment of advanced non-small cell lung cancer. The first-generation EGFR inhibitors erlotinib and gefitinib have been approved for treatment in the second- and third-line setting. Second-generation EGFR tyrosine kinase inhibitors are now in development aiming to improve efficacy and overcome primary and secondary resistance to the first-generation drugs. The two most common strategies being used to achieve these aims are irreversible binding of drug to target and kinase multi-targeting. This is an overview of the early clinical development of selected second-generation tyrosine kinase inhibitors focusing on the treatment of non-small cell lung cancer.     

EGFR基因靶向治疗非小细胞肺癌的研究进展

非小细胞肺癌(Non-small cell lung cancer,NSCLC)是现阶段临床发现的肺癌患者中发病率最高的一种类型,治疗手段匮乏,效果不甚理想,目前临床中研究热点是EGFR基因在NSCLC靶向治疗中的作用。表皮生长因子受体酪氨酸激酶抑制剂(EGFR-TKIs)是基于EGFR基因作用而开发出来,用于治疗EGFR基因突变阳性的NSCLC患者。本文综述了EGFR基因靶向治疗非小细胞肺癌的研究进展。     

HER2基因突变晚期非小细胞肺癌治疗进展

肺癌是全球范围内一种高发病率和高死亡率的恶性肿瘤,非小细胞肺癌（NSCLC）是最常见的亚型,发生率约85%。人表皮生长因子受体2（HER2）是受体酪氨酸激酶（RTK）的重要成员之一,NSCLC中HER2基因主要表现为HER2突变、HER2扩增和HER2过表达三种形式。目前,靶向HER2突变的酪氨酸激酶抑制剂、单克隆抗体和抗体偶联药物在HER2突变的NSCLC中显示出一定的临床疗效,但相关免疫治疗疗效有限。本文就HER2突变相关NSCLC的治疗进展进行综述,以期为进一步完善HER2突变晚期NSCLC临床诊疗策略提供理论依据。     

Molecularly-targeted therapies for non-small cell lung cancer

Targeting cell-signalling pathways that confer survival advantage to cancer cells has become a major focus of investigation for the treatment of various malignancies. Non-small cell lung cancer (NSCLC), a disease with wide molecular heterogeneity, has become a main testing ground for the evaluation of various targeted agents. Inhibition of the epidermal growth factor pathway with erlotinib results in improved survival and symptom control for patients with advanced NSCLC who progressed following one or two prior chemotherapy regimens. Gefitinib, the first epidermal growth factor receptor (EGFR) inhibitor to be approved by the FDA, failed to demonstrate survival advantage over placebo in a large Phase III trial for patients with advanced NSCLC. The results of this study have raised several important clinical and biological issues that may be relevant for the development of other targeted agents. Recent identification of mutations in the ATP-binding pocket of the EGFR is the first step towards proper patient selection for therapy with an EGFR tyrosine kinase inhibitor. In addition, predictive potential has also been seen with EGFR gene amplification. It is unclear whether monoclonal antibodies against the EGFR may be active independent of the EGFR mutation, as the site of action is different from tyrosine kinase inhibitors. A recent randomised clinical trial that combined the antiangiogenic agent bevacizumab with chemotherapy has demonstrated survival advantage over chemotherapy alone for certain subsets of patients with advanced NSCLC. The exciting results of this study represent an important advance in the treatment of patients with advanced NSCLC.     

Molecularly-targeted therapies for non-small cell lung cancer

Targeting cell-signalling pathways that confer survival advantage to cancer cells has become a major focus of investigation for the treatment of various malignancies. Non-small cell lung cancer (NSCLC), a disease with wide molecular heterogeneity, has become a main testing ground for the evaluation of various targeted agents. Inhibition of the epidermal growth factor pathway with erlotinib results in improved survival and symptom control for patients with advanced NSCLC who progressed following one or two prior chemotherapy regimens. Gefitinib, the first epidermal growth factor receptor (EGFR) inhibitor to be approved by the FDA, failed to demonstrate survival advantage over placebo in a large Phase III trial for patients with advanced NSCLC. The results of this study have raised several important clinical and biological issues that may be relevant for the development of other targeted agents. Recent identification of mutations in the ATP-binding pocket of the EGFR is the first step towards proper patient selection for therapy with an EGFR tyrosine kinase inhibitor. In addition, predictive potential has also been seen with EGFR gene amplification. It is unclear whether monoclonal antibodies against the EGFR may be active independent of the EGFR mutation, as the site of action is different from tyrosine kinase inhibitors. A recent randomised clinical trial that combined the antiangiogenic agent bevacizumab with chemotherapy has demonstrated survival advantage over chemotherapy alone for certain subsets of patients with advanced NSCLC. The exciting results of this study represent an important advance in the treatment of patients with advanced NSCLC.     

Erlotinib in non-small-cell lung cancer

Epidermal growth factor receptor (EGFR) plays an essential role in normal cell growth and differentiation, and is involved in tumour proliferation and survival. EGFR overexpression is a common feature in solid malignancies, including non-small-cell lung cancer (NSCLC), and is associated with poor clinical prognosis. Erlotinib is a small-molecule inhibitor of EGFR tyrosine kinase, showing a significant improvement in median survival, quality of life and related symptoms in an unselected population of advanced NSCLC patients in the second- or third-line setting. Erlotinib is well tolerated (with common toxicities including rash and diarrhoea) when administered at a standard oral daily dose of 150 mg. Further investigations are ongoing to contribute to our understanding of the role of erlotinib in NSCLC treatment.     

EGFR突变的非小细胞肺癌耐药机制及其克服新策略

表皮生长因子受体（EGFR）突变的非小细胞肺癌（NSCLC）已被列为一个与临床相关的、独特的肺癌亚群。虽然EGFR突变的肿瘤患者增加了对酪氨酸激酶抑制剂（TKI）的敏感性,但其耐药仍然是一个主要的临床问题。针对原发和获得性耐药不同的分子机制,包括应用第2代或第3代TKI,以及与EGFR下游信号通路抑制剂的组合用药等多项临床试验已经在启动和计划中。本文综述了近年来EGFR突变的NSCLC耐药机制的新进展和克服耐药的新策略。     

Erlotinib in non-small-cell lung cancer

Epidermal growth factor receptor (EGFR) plays an essential role in normal cell growth and differentiation, and is involved in tumour proliferation and survival. EGFR overexpression is a common feature in solid malignancies, including non-small-cell lung cancer (NSCLC), and is associated with poor clinical prognosis. Erlotinib is a small-molecule inhibitor of EGFR tyrosine kinase, showing a significant improvement in median survival, quality of life and related symptoms in an unselected population of advanced NSCLC patients in the second- or third-line setting. Erlotinib is well tolerated (with common toxicities including rash and diarrhoea) when administered at a standard oral daily dose of 150 mg. Further investigations are ongoing to contribute to our understanding of the role of erlotinib in NSCLC treatment.     

Optimal management of patients with non-small cell lung cancer and epidermal growth factor receptor mutations

In recent years, the epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs), gefitinib and erlotinib, which have promising activity and a favourable toxicity profile, have been used in the management of advanced non-small cell lung cancer (NSCLC). The knowledge that EGFR-activating mutations confer sensitivity to EGFR TKIs has led to the design and analysis of phase II and III studies of gefitinib or erlotinib treatment in various clinical scenarios. We review the important NSCLC clinical trials of the efficacy of EGFR TKIs in the context of EGFR-activating mutations. In all phase II single-arm studies or phase III randomized comparative studies, EGFR TKIs as monotherapy were superior to combination chemotherapy in terms of response rate and progression-free survival in patients with activating EGFR mutations. EGFR TKIs have contributed to the superior overall survival time in NSCLC patients with EGFR mutations compared with those patients without EGFR mutations. The results of these studies have led to a paradigm shift in the treatment of patients with advanced NSCLC. NSCLC with EGFR mutations constitutes a new entity requiring different personalized treatment strategies.     

Clinical experience with erlotinib in non-small-cell lung cancer

Lung cancer is the leading cause of cancer death worldwide. Despite the introduction of more- effective chemotherapeutic agents, it appears that a survival plateau has been reached, so new treatment strategies are clearly needed. One innovative therapeutic cancer strategy is the introduction of biological agents that target specific intracellular pathways related to the distinctive properties of cancer cells. Among these agents, epidermal growth factor receptor (EGFR)-targeting agents have received particular attention in lung cancer. Numerous EGFR blockers have been evaluated, including monoclonal antibodies to the receptor and small-molecule tyrosine kinase inhibitors. The present review focuses on the tyrosine kinase inhibitor erlotinib. Preclinical studies have shown that erlotinib blocks the growth of human non-small-cell lung cancer (NSCLC) cell lines in vitro by inhibiting the receptor and the downstream protein phosphorylation. In a randomized study conducted by the National Cancer Institute of Canada (BR.21) in second- and third-line NSCLC treatment, erlotinib significantly prolonged overall survival and decreased symptoms compared with placebo. A crucial aspect of the clinical development of molecular-targeted therapies is to understand which patients will obtain clinical benefit from their use. Sensitivity to erlotinib has been associated with EGFR mutations, most commonly deletions of four to six amino acids in exon 19 or a point mutation (L858R) in exon 21. Increased EGFR gene copy number has also been pointed out as a good predictive marker for erlotinib response. Intense research activity is ongoing to validate known predictive markers and to discover new tools which maximize clinical benefit using erlotinib. However, there is no conclusive evidence, as yet, linking response to survival.     

表皮生长因子受体酪氨酸激酶抑制剂在肿瘤治疗中的应用

表皮生长因子受体 (EGFR)酪氨酸激酶 ,是细胞外信号传递到细胞内的重要枢纽 ,它在信号传导、细胞增殖、分化以及各种调节机制中发挥重要作用 ,在多种癌细胞中过度表达。许多研究表明 ,抑制EGFR酪氨酸激酶活性 ,可抑制肿瘤生长。目前 ,已有几种EGFR酪氨酸激酶抑制剂进入了临床试验。本文对几种EGFR酪氨酸激酶小分子抑制剂在肿瘤治疗中的研究进展做一综述。     

EGFR-TKIs在NSCLC中的耐药机制及治疗策略研究进展

表皮生长因子受体（EGFR）抑制剂是目前临床治疗非小细胞肺癌（NSCLC）的一线小分子靶向药物,随着EGFR酪氨酸激酶抑制剂（EGFR-TKI）的广泛使用,其耐药现象也日趋明显,已成为其治疗NSCLC的巨大挑战。本文总结了EGFR-TKIs在NSCLC中的主要耐药机制,并对相关逆转策略的研究进展进行综述。     

Epidermal growth factor receptor tyrosine kinase inhibitors in late stage clinical trials

The epidermal growth factor receptor (EGFR) is a cell membrane receptor that plays a key role in cancer development and progression. Ligand-activated EGFR-dependent signalling is involved in cell proliferation, apoptosis, angiogenesis and metastatic spread. Targeting the EGFR, therefore, represents a promising molecular approach in cancer treatment. Several anti-EGFR agents are in clinical development. Three drugs are currently in Phase II and III development as single agents, or in combination with other anticancer modalities: IMC-225 (cetuximab/Erbitux?; ImClone), a chimaeric human–mouse monoclonal IgG₁ antibody, which blocks ligand binding and functional activation of the EGFR; OSI-774 (erlotinib/Tarceva?; Genentech/OSI/Roch) and ZD1839 (gefitinib/Iressa^®; AstraZeneca), two small molecule EGFR-selective inhibitors of tyrosine kinase enzymatic activity, which prevent EGFR autophosphorylation and activation. Iressa is the first EGFR-targeting agent to be registered as an anticancer drug in Japan, in Australia and in the US for the third-line treatment of chemoresistant non-small cell lung cancer (NSCLC) patients. This review will focus on the preclinical background and on the results from the first series of clinical trials with these drugs. Furthermore, continuing clinical trials and a series of open clinical issues for the development of optimal strategies of using EGFR-targeting agents will be discussed.