Exon 20 YVMA insertion is associated with high incidence of brain metastasis and inferior outcome of chemotherapy in advanced non-small cell lung cancer patients with HER2 kinase domain mutations

Clinical and structural insights into the rare but oncogenic HER2-activating missense mutations in non-small cell lung cancer: a retrospective ATLAS cohort study

BACKGROUND

Unlike human epidermal growth factor receptor 2 (HER2) amplification or exon 20 insertions, missense mutations in the extracellular domain (ECD), transmembrane domain (TMD), and intracellular domain (ICD) of the HER2 protein have been implicated as oncogenic in non-small cell lung cancer (NSCLC). However, their molecular subtypes, structural disparities, and clinical responses to current medical treatments, particularly HER2-targeted tyrosine kinase inhibitors (TKIs), remain unclear in NSCLC and warrant investigation.

METHODS

A real-world observational ATLAS study was conducted to gather and analyze therapeutic outcomes of chemotherapy or TKIs for heterogeneous HER2 missense mutations in NSCLC. Computational models of typical ECD, TMD, and ICD mutations were utilized to explore their structural variances.

RESULTS

We screened 37 eligible patients with HER2-activating missense mutations, of which 35 patients who had received chemotherapy or HER2-targeted TKIs as first-line therapy were available for response assessment. The median progression-free survival (PFS) for chemotherapy was 4.43 months (95% confidence interval [CI], 3.77-5.10), with an objective response rate (ORR) of 26.1% (6/23) and a disease control rate (DCR) of 17/23 (73.9%). The administration of afatinib, dacomitinib, and pyrotinib, HER2-targeted TKIs, achieved a median PFS of 4.65 months, with an ORR of 33.3% (4/12) and a DCR of 83.3% (10/12). Molecular modeling and computational simulations of ECD, TMD, and ICD mutations revealed their distinct structural characteristics.

CONCLUSION

In comparison to chemotherapy, HER2-targeted TKIs demonstrated similar activity and PFS benefits for HER2-activating missense mutations in NSCLC.

The rapidly changing field of predictive biomarkers of non-small cell lung cancer

Lung cancer is a leading cause of cancer-related death worldwide in both men and women, however mortality in the US and EU are recently declining in parallel with the gradual cut of smoking prevalence. Consequently, the relative frequency of adenocarcinoma increased while that of squamous and small cell carcinomas declined. During the last two decades a plethora of targeted drug therapies have appeared for the treatment of metastasizing non-small cell lung carcinomas (NSCLC). Personalized oncology aims to precisely match patients to treatments with the highest potential of success. Extensive research is done to introduce biomarkers which can predict the effectiveness of a specific targeted therapeutic approach. The EGFR signaling pathway includes several sufficient targets for the treatment of human cancers including NSCLC. Lung adenocarcinoma may harbor both activating and resistance mutations of the EGFR gene, and further, mutations of KRAS and BRAF oncogenes. Less frequent but targetable genetic alterations include ALK, ROS1, RET gene rearrangements, and various alterations of MET proto-oncogene. In addition, the importance of anti-tumor immunity and of tumor microenvironment has become evident recently. Accumulation of mutations generally trigger tumor specific immune defense, but immune protection may be upregulated as an aggressive feature. The blockade of immune checkpoints results in potential reactivation of tumor cell killing and induces significant tumor regression in various tumor types, such as lung carcinoma. Therapeutic responses to anti PD1-PD-L1 treatment may correlate with the expression of PD-L1 by tumor cells. Due to the wide range of diagnostic and predictive features in lung cancer a plenty of tests are required from a single small biopsy or cytology specimen, which is challenged by major issues of sample quantity and quality. Thus, the efficacy of biomarker testing should be warranted by standardized policy and optimal material usage. In this review we aim to discuss major targeted therapy-related biomarkers in NSCLC and testing possibilities comprehensively.

A retrospective study of first-line therapy and subsequent pyrotinib treatment in advanced lung adenocarcinoma with HER2 mutations

OBJECTIVES

HER2 is an infrequently mutated driver gene in non-small cell lung cancer (NSCLC). At present, there has been no comprehensive large-scale clinical study to establish the optimal first-line treatment strategy for advanced lung adenocarcinoma (LUAD) with HER2-Mutant. Besides that, the effectiveness and safety of pyrotinib, a pan-HER inhibitor, in the context of NSCLC are still undergoing investigation.

MATERIALS AND METHODS

In this study, we conducted a retrospective data collection of HER2-Mutated advanced LUAD who received first-line treatment and pyrotinib between May 2014 and June 2023. Patients treated with chemotherapy, chemotherapy + immune checkpoint inhibitors (ICIs), chemotherapy + bevacizumab and pyrotinib in first-line treatment. Furthermore, we collected data on the efficacy and safety of pyrotinib in these patients after disease progression. The main endpoint of the study was progression-free survival (PFS).

RESULTS

In the final analysis, 89 patients were included in the first-line cohort and 30 patients were included in the pyrotinib cohort. In the first-line treatment cohort, chemotherapy + ICIs, chemotherapy + bevacizumab, and pyrotinib exhibited notable survival benefits compared to chemotherapy (median PFS: 9.87 vs. 7.77 vs. 7.10 vs. 5.40 months, p-value < 0.05). Furthermore, patients with a first-line treatment PFS of less than 6 months may potentially benefit from subsequent treatment with pyrotinib (median PFS: 7.467 vs. 3.000, p-value = 0.0490).

CONCLUSIONS

In the first-line treatment of HER2-Mutant LUAD, regimens involving combinations like chemotherapy + ICIs, chemotherapy + bevacizumab, and pyrotinib may confer enhanced survival advantages compared to chemotherapy. Nevertheless, no significant distinctions were observed among these three treatment strategies, underscoring the imperative to identify biomarkers for the discerning selection of suitable therapeutic modalities. Moreover, patients with suboptimal response to first-line treatment may potentially derive more benefit from pyrotinib.

HER2-Altered Non-Small Cell Lung Cancer: A Journey from Current Approaches to Emerging Strategies

For patients diagnosed with advanced HER2-altered non-small cell lung cancer (NSCLC), the current standard of care is represented by a platinum-pemetrexed-based chemotherapy, eventually in combination with immunotherapy. Different pan-HER tyrosine kinase inhibitors have been evaluated in limited phase II trials, yielding generally unsatisfactory outcomes, although certain genotypes demonstrated some clinical benefit. Conversely, antibody-drug conjugates (ADCs) targeting HER2, particularly trastuzumab-deruxtecan, have shown promising results against HER2-mutant disease, including a great intracranial activity in patients with brain metastasis. Based on the results obtained from DESTINY-Lung01 and DESTINY-Lung02 trials, trastuzumab deruxtecan received regulatory approval as the first targeted therapy for pre-treated, HER2-mutant, advanced NSCLC patients. More recently, the Food and Drug Administration (FDA) granted the accelerated approval of trastuzumab deruxtecan for advanced, pre-treated HER2-positive solid tumours with no other treatment options. In this scenario, emerging evidence is increasingly pointing towards the exploration of combination regimens with synergistic effects in the advanced disease. In this review, we provide a detailed summary of current approaches and emerging strategies in the management of HER2-altered NSCLC, also focusing on unmet needs, including the treatment of patients with brain metastases.

Trastuzumab deruxtecan (DS8201) for advanced non-small cell lung cancer with HER2 exon 20 insertion mutation: a case report

An antibody-drug conjugate (ADC) of human epidermal growth factor receptor-2 (HER2) provides effective treatment for patients with HER2-positive non-small cell lung cancer (NSCLC). Exon 20 insertion mutations are the most common among HER2 mutations. This mutant subtype is highly drug-resistant, and patients receiving conventional treatment often have a poor prognosis. Trastuzumab deruxtecan (T-DXd), a novel anti-HER2 ADC, has emerged as a novel treatment option for HER2-positive (mutated, expressed, amplified, alternated) NSCLC, based on several studies and reported results. Herein, we report a case of stage IV NSCLC with HER2 exon 20 mutation in a 52-year-old male patient whose tumor recurred after radical resection of pulmonary carcinoma, who could not tolerate chemotherapy, and presented with bone metastasis. After treatment with T-DXd, the tumor significantly regressed and bone metastasis improved, maintaining a state of no progression for 21 months. This case report evidences the use of T-DXd in the treatment of NSCLC with HER2 exon 20 insertion mutation.

Management of HER2 alterations in non-small cell lung cancer - The past, present, and future

HER2 mutations, which account for 2-4% of non-small cell lung cancer (NSCLC), are distinct molecular alterations identified via next generation sequencing (NGS). Previously, treatment outcomes in HER2-mutant metastatic NSCLC were dismal, showing limited clinical benefit with platinum-based chemotherapy with or without immunotherapy. In contrast to HER2-altered breast and gastric cancer, HER2-mutant NSCLC does not benefit from HER2 targeting agents such as trastuzumab or TDM1. HER2 mutations are also inherently different from HER2 overexpression and amplification. Currently, trastuzumab deruxtecan, a HER2 targeting antibody drug conjugate (ADC) is the first and only approved treatment option for patients with HER2-mutant metastatic NSCLC after failure with standard treatment. In this review, we summarized the biology of HER2 and detection of HER2 overexpression, amplification and mutations, as well as general landscape of landmark and ongoing clinical trials encompassing from chemotherapy to targeted agents, including tyrosine kinase inhibitors (TKIs), ADCs and investigational agents.

Immunotherapy and brain metastasis in lung cancer: connecting bench side science to the clinic

Brain metastases (BMs) are the most common form of intracranial malignant neoplasms in adults, with a profound impact on quality of life and traditionally associated with a dismal prognosis. Lung cancer accounts for approximately 40%-50% of BM across different tumors. The process leading to BMs is complex and includes local invasion, intravasation, tumor cells circulation into the bloodstream, disruption of the blood-brain barrier, extravasation of tumor cells into the brain parenchyma, and interaction with cells of the brain microenvironment, among others. Once the tumor cells have seeded in the brain parenchyma, they encounter different glial cells of the brain, as well as immune cells. The interaction between these cells and tumor cells is complex and is associated with both antitumoral and protumoral effects. To overcome the lethal prognosis associated with BMs, different treatment strategies have been developed, such as immunotherapy with immune checkpoint inhibitors, particularly inhibitors of the PD-1/PD-L1 axis, which have demonstrated to be an effective treatment in both non-small cell lung cancer and small cell lung cancer. These antibodies have shown to be effective in the treatment of BM, alone or in combination with chemotherapy or radiotherapy. However, many unsolved questions remain to be answered, such as the sequencing of immunotherapy and radiotherapy, the optimal management in symptomatic BMs, the role of the addition of anti-CTLA-4 antibodies, and so forth. The complexity in the management of BMs in the era of immunotherapy requires a multidisciplinary approach to adequately treat this devastating event. The aim of this review is to summarize evidence regarding epidemiology of BM, its pathophysiology, current approach to treatment strategies, as well as future perspectives.

Immunotherapy as a later-line option for HER2-altered advanced non-small-cell lung cancer: taxane might be a favorable partner

Aim: To assess the effectiveness of different types of taxanes, including nab-paclitaxel, paclitaxel and docetaxel, and further compare the effectiveness of taxane-based chemotherapy, taxane-based chemotherapy plus angiogenesis inhibitors or taxane-based chemotherapy plus immune checkpoint inhibitors in HER2-altered non-small-cell lung cancer in the second- or third-line setting. Materials & methods: A total of 52 patients were included in the study. Progression-free survival was compared between subgroups. Results: A clinically meaningful improvement in progression-free survival was observed among patients in the nab-paclitaxel group compared with the docetaxel group. Taxane-based chemotherapy plus immune checkpoint inhibitors achieved longer progression-free survival than taxane-based chemotherapy. There was no difference between taxane-based chemotherapy plus immune checkpoint inhibitors and taxane-based chemotherapy plus angiogenesis inhibitors. Conclusion: Nab-paclitaxel appears to be a reasonable alternative to docetaxel. Chemotherapy plus immune checkpoint inhibitors might yield more survival benefits than chemotherapy alone.

Exploration on the first-line treatment of ERBB2-altered advanced non-small cell lung cancer: A multicenter retrospective study

BACKGROUND

Although the treatment of ERBB2-altered non-small cell lung cancer (NSCLC) has been studied for many years, there are no comprehensive studies to evaluate the benefits of various therapies as first-line treatment. Through the development of immunotherapy, more and more different combination treatments were applicated in clinical practice, therefore, we conducted a multicenter retrospective study to evaluate the efficacy of different treatments.

METHODS

We enrolled patients with ERBB2-altered NSCLC who had undergone at least one-line systemic anticancer treatment to evaluate the efficacy of first-line chemotherapy alone (Chemo), anti-ERBB2 tyrosine kinase inhibitor (TKI), chemotherapy plus immunotherapy (Chemo + Immuno), chemotherapy plus anti-angiogenesis therapy (Chemo + Antiangio) and chemotherapy combined with immunotherapy and anti-angiogenesis therapy (Chemo + Immuno + Antiangio). The clinical outcomes included objective response rate (ORR), disease control rate (DCR), median progression-free survival (mPFS), one-year and three-year survival rate.

RESULTS

We enroll 36 patients harboring ERBB2 mutation and 29 with ERBB2 amplification. The overall ORR was 30.8%, DCR was 69.2% and mPFS was 5.7 months. Chemo + Immuno and Chemo + Antiangio both achieved longer mPFS than TKI (7.8 vs 3.6 months, HR: 0.24, 95 %CI: 0.09-0.64, P = 0.002; 5.9 vs 3.6 months, HR: 0.36, 95 %CI: 0.15-0.88, P = 0.019; respectively), while there was no significant difference in mPFS between Chemo + Immuno or Chemo + Antiangio and Chemo (both P > 0.05), the mPFS of the first two was longer. For ERBB2-mutant patients, the mPFS was 5.9 months, and Chemo + Immuno and Chemo + Antiangio both achieved longer mPFS than TKI (12.9 vs 2.9 months, HR: 0.15, 95 %CI: 0.03-0.68, P = 0.005; 7.1 vs 2.9 months, HR: 0.50, 95 %CI: 0.29-0.88, P = 0.009, respectively). In the same therapies, patients with ERBB2 mutation or ERBB2 amplification showed no statistical significance in PFS (both P > 0.05).

CONCLUSIONS

In the first-line treatment of ERBB2-altered NSCLC, chemotherapy combined with immunotherapy or anti-angiogenesis therapy may have greater survival benefits than ERBB2-target therapy, but the efficacy may not be better than that of chemotherapy.

"A Review of HER2 overexpression and somatic mutations in cancers"

The Human Epidermal Growth Factor Receptor (HER) proteins family, which includes HER2, are membrane-bound receptors that activate many intracellular pathways associated with growth and development. When there are mutations in HER2, or when it becomes overexpressed, it can cause oncogenesis and offer differential prognosis and treatment across almost all cancer types. Both mutations in HER2 and its overexpression have distinct mechanisms by which they can cause these effects in cancers. This review outlines how HER2's normal pathway is altered in both overexpression and mutation and compiles all the well-known mechanisms by which HER2 can cause oncogenesis. Finally, this review briefly outlines how HER2 mutants and HER2 overexpression is detected, and how their detection can lead to different prognosis and treatment in cancers.

Genomics of Breast Cancer Brain Metastases: A Meta-Analysis and Therapeutic Implications

Breast cancer brain metastases are a challenging daily practice, and the biological link between gene mutations and metastatic spread to the brain remains to be determined. Here, we performed a meta-analysis on genomic data obtained from primary tumors, extracerebral metastases and brain metastases, to identify gene alterations associated with metastatic processes in the brain. Articles with relevant findings were selected using Medline via PubMed, from January 1999 up to February 2022. A critical review was conducted according to the Preferred Reporting Items for Systematic Review and Meta-analysis statement (PRISMA). Fifty-seven publications were selected for this meta-analysis, including 37,218 patients in all, 11,906 primary tumor samples, 5541 extracerebral metastasis samples, and 1485 brain metastasis samples. We report the overall and sub-group prevalence of gene mutations, including comparisons between primary tumors, extracerebral metastases and brain metastases. In particular, we identified six genes with a higher mutation prevalence in brain metastases than in extracerebral metastases, with a potential role in metastatic processes in the brain: ESR1, ERBB2, EGFR, PTEN, BRCA2 and NOTCH1. We discuss here the therapeutic implications. Our results underline the added value of obtaining biopsies from brain metastases to fully explore their biology, in order to develop personalized treatments.

Evolving Treatment Landscape of HER2-mutant Non-Small Cell Lung Cancer: Trastuzumab Deruxtecan and Beyond

Successful targeting of HER2-activating mutations in DESTINY-Lung02 phase II study has led to the approval of the antibody-drug conjugate (ADC) trastuzumab deruxtecan (T-DXd) as second-line treatment in patients with non-small cell lung cancer (NSCLC). Despite the impressive results, several matters need to be addressed, including the clinical activity of T-DXd in patients with disease in the central nervous system as well as the role of T-DXd in the context of HER2 overexpression. Additionally, data regarding novel agents used to target HER2 continue to accumulate. This review highlights the challenges and unanswered questions that have emerged after the approval of T-DXd in patients with HER2-mutant NSCLC.

Deciphering the Impact of HER2 Alterations on Non-Small-Cell Lung Cancer: From Biological Mechanisms to Therapeutic Approaches

Despite the recent increase in the number of types of treatments, non-small-cell lung cancer (NSCLC) remains the major cause of death from cancer worldwide. So, there is an urgent need to develop new therapeutic strategies. The HER2 gene codes for tyrosine kinase receptor whose alterations are known to drive carcinogenesis. HER2 alterations, including amplification, mutations, and overexpression, have been mainly described in breast and gastric cancers, but up to 4% of NSCLC harbor actionable HER2 mutations. HER2-targeted therapy for NSCLC with trastuzumab, pertuzumab, and trastuzumab emtansine has failed to demonstrate an improvement in survival. Nevertheless, recent data from phase II trials have shed light on promising specific therapies for HER2-mutant NSCLC such as trastuzumab deruxtecan. Herein, we aimed to provide an updated review on the biology, epidemiology, molecular testing, and therapeutic strategies for NSCLC with HER2 molecular alterations.

HER2 in Non-Small Cell Lung Cancer: A Review of Emerging Therapies

Simple Summary

There are growing data on targeting HER2 alterations, which include gene mutations, gene amplifications, and protein overexpression, for non-small cell lung cancer (NSCLC). Currently, there are limited targeted therapies approved for NSCLC patients with HER2 alterations, and this remains an unmet clinical need. There has been an influx of research on antibody–drug conjugates, monoclonal antibodies, and tyrosine kinase inhibitors. This review discusses the diagnostic challenges of HER2 alterations in NSCLC and summarizes recent progress in HER2 targeted drugs for both clinicians and researchers treating this patient population.

Abstract

Human epidermal growth factor receptor 2 (HER2), a member of the ERBB family of tyrosine kinase receptors, has emerged as a therapeutic target of interest for non-small cell lung cancer (NSCLC) in recent years. Activating HER2 alterations in NSCLC include gene mutations, gene amplifications, and protein overexpression. In particular, the HER2 exon 20 mutation is now a well clinically validated biomarker. Currently, there are limited targeted therapies approved for NSCLC patients with HER2 alterations. This remains an unmet clinical need, as HER2 alterations are present in 7–27% of de novo NSCLC and may serve as a resistance mechanism in up to 10% of EGFR mutated NSCLC. There has been an influx of research on antibody–drug conjugates (ADCs), monoclonal antibodies, and tyrosine kinase inhibitors (TKIs) with mixed results. The most promising therapies are ADCs (trastuzumab-deruxtecan) and novel TKIs targeting exon 20 mutations (poziotinib, mobocertinib and pyrotinib); both have resulted in meaningful anti-tumor efficacy in HER2 mutated NSCLC. Future studies on HER2 targeted therapy will need to define the specific HER2 alteration to better select patients who will benefit, particularly for HER2 amplification and overexpression. Given the variety of HER2 targeted drugs, sequencing of these agents and optimizing combination therapies will depend on more mature efficacy data from clinical trials and toxicity profiles. This review highlights the challenges of diagnosing HER2 alterations, summarizes recent progress in novel HER2-targeted agents, and projects next steps in advancing treatment for the thousands of patients with HER2 altered NSCLC.

HER2-Altered Non-Small Cell Lung Cancer: Biology, Clinicopathologic Features, and Emerging Therapies

Multiple oncogenic molecular alterations have been discovered that serve as potential drug targets in non-small cell lung cancer (NSCLC). While the pathogenic and pharmacological features of common targets in NSCLC have been widely investigated, those of uncommon targets are still needed to be clarified. Human epidermal growth factor receptor 2 (HER2, ERBB2)-altered tumors represent a highly heterogeneous group of diseases, which consists of three distinct situations including mutation, amplification and overexpression. Compared with breast and gastric cancer, previous studies have shown modest and variable results of anti-HER2 treatments in lung cancers with HER2 aberrations, thus effective therapies in these patients represent an unmet medical need. By far, encouraging efforts towards novel treatment strategies have been made to improve the clinical outcomes of these patients. In this review, we describe the biological and clinicopathological characteristics of HER2 alterations and systematically sum up recent studies on emerging therapies for this subset of patients.

First-line immunotherapy or angiogenesis inhibitor plus chemotherapy for HER2-altered NSCLC: a retrospective real-world POLISH study

Background:

There have been no comprehensive large-scale studies that have evaluated the benefits of chemotherapy-based regimens in addressing HER2-altered advanced non-small-cell lung cancer (NSCLC) in a first-line setting. Data on HER2 alteration subtypes and concomitant alterations are also limited. Accordingly, our retrospective, real-world POLISH study assesses the efficacy of first-line chemotherapy alone (C) as well as combinations with immune checkpoint inhibitors (C + I) or angiogenesis inhibitors (C + A) for HER2-altered NSCLC; molecular features are also reported.

Methods:

HER2-altered NSCLC patients who received a first-line treatment between November 2015 and September 2021 were screened. Patients treated with C, C + I, or C + A were included in our final efficacy analysis. Progression-free survival (PFS) was compared between the subgroups. A Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis was performed to evaluate concomitant alterations.

Results:

A total of 293 patients were screened, with an identification of HER2 amplification and 37 distinct HER2 mutations, and 210 cases treated with C, C + I, or C + A were ultimately included. C + A achieved longer PFS than C (5.63 vs 4.03 months, hazard ratio: 0.64, 95% confidence interval [CI]: 0.46–0.88, p = 0.006). C + I did not improve median PFS compared to C + A or C (both p > 0.05), despite the programmed cell death ligand-1 (PD-L1) expression or tumor mutational burden. KEGG analysis revealed that concomitant upregulation of PI3 K/AKT pathway signaling was common in HER2-altered NSCLC.

Conclusion:

Chemotherapy plus angiogenesis inhibitors may yield a greater survival benefit than chemotherapy alone in a first-line setting for HER2-altered NSCLC, whereas an immune-based combination therapy may not be superior to a sole chemotherapy regimen. Activation of PI3 K/AKT signaling may mediate immunosuppression in HER2-altered NSCLC.

Consensus for HER2 alterations testing in non-small-cell lung cancer

Human epidermal growth factor receptor 2 (HER2) is a transmembrane glycoprotein receptor with intracellular tyrosine kinase activity. Its alterations, including mutation, amplification and overexpression, could result in oncogenic potential and have been detected in many cancers such as non-small-cell lung cancer (NSCLC). Such alterations are, in general, considered markers of poor prognosis. Anti-HER2 antibody-drug conjugates, e.g. trastuzumab deruxtecan (T-DXd, DS-8201) and disitamab vedotin (RC48), were recently approved for HER2-positive breast and gastric cancers. Meanwhile, several HER2-targeted drugs, such as T-DXd, neratinib, afatinib, poziotinib and pyrotinib, have been evaluated in patients with advanced NSCLC, with several of them demonstrating clinical benefit. Therefore, identifying HER2 alterations is pivotal for NSCLC patients to benefit from these targeted therapies. Recent guidelines on HER2 testing were developed for breast and gastric cancer, however, and have not been fully established for NSCLC. The expert group here reached a consensus on HER2 alteration testing in NSCLC with the focus on clinicopathologic characteristics, therapies, detection methods and diagnostic criteria for HER2-altered NSCLC patients. We hope this consensus could improve the clinical management of NSCLC patients with HER2 alterations.

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Human epidermal growth factor receptor 2 (HER2) alterations lead to poor prognosis in non-small-cell lung cancer (NSCLC).

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Identifying HER2 alterations is pivotal to guide the anti-HER2-targeted therapies in NSCLC.

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The requirements for HER2 mutation, amplification or expression testing are distinct in NSCLC.

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This consensus fills the gap in the criteria for HER2 alteration testing in NSCLC.

EGFR and HER2 exon 20 insertions in solid tumours: from biology to treatment

Protein tyrosine kinases of the human epidermal growth factor receptor family, including EGFR and HER2, have emerged as important therapeutic targets in non-small-cell lung, breast and gastroesophageal cancers, and are of relevance for the treatment of various other malignancies (particularly colorectal cancer). Classic activating EGFR exon 19 deletions and exon 21 mutations, and HER2 amplification and/or overexpression, are predictive of response to matched molecularly targeted therapies, translating into favourable objective response rates and survival outcomes. By comparison, cancers with insertion mutations in exon 20 of either EGFR or HER2 are considerably less sensitive to the currently available tyrosine kinase inhibitors and antibodies targeting these receptors. These exon 20 insertions are structurally distinct from other EGFR and HER2 mutations, providing an explanation for this lack of sensitivity. In this Review, we first discuss the prevalence and pan-cancer distribution of EGFR and HER2 exon 20 insertions, their biology and detection, and associated responses to current molecularly targeted therapies and immunotherapies. We then focus on novel approaches that are being developed to more effectively target tumours driven by these non-classic EGFR and HER2 alterations.