Development of EGFR TKIs and Options to Manage Resistance of Third-Generation EGFR TKI Osimertinib: Conventional Ways and Immune Checkpoint Inhibitors

Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR TKIs) have been first-line therapy in the treatment of non-small cell lung cancer (NSCLC) harboring EGFR sensitive mutations. Progression inevitably happens after 10–14 months of first- or second-generation EGFR TKIs treatment for acquired resistance. Owing to the successful identification of EGFR T790M, third-generation EGFR TKIs such as osimertinib were developed to target such resistance mutation. Nowadays, osimertinib has shown its efficacy both in first-line and second-line after resistance to previous generations of TKI treatment of EGFR-mutant NSCLC. However, drug resistance also emerges on third-generation EGFR TKIs. Multiple mechanisms of acquired resistance have been identified, and some novel strategies were reported to overcome third-generation TKI resistance. Immune checkpoint inhibitors (ICIs) have dramatically changed the prognosis of selected patients. For patients with EGFR-addicted metastatic NSCLC, ICIs have also revealed a potential role. In this review, we will take stock of mechanisms of acquired resistance to third-generation TKIs and discuss current challenges and future perspectives in clinical practice.

Concurrent T790M and L858R mutations in treatment-naïve metastatic non-small-cell lung cancer: A therapeutic challenge – Current treatment strategies and promising therapies of the future in a nutshell

De novo (pretreatment) epidermal growth factor receptor T790M mutation in non-small-cell lung cancer (NSCLC) is rare when detected by standard genotyping methods. We present a case of concurrent de novo T790M and L858R mutations detected by direct sequencing in treatment-naïve metastatic NSCLC. This case is worthy of mention as the presence of this mutation has a bearing on the choice of treatment. This article aims to evaluate the clinical outcome for metastatic NSCLC with de novo T790M mutation and formulate an optimum treatment plan in this clinical scenario. The novel targeted therapy agents have also been reviewed.

Design, synthesis and evaluation of the osimertinib analogue (C-005) as potent EGFR inhibitor against NSCLC

Osimertinib has been approved as a first-line treatment for non-small-cell lung cancer (NSCLC) patients whose tumor carries EGFR activation and / or resistant mutations. To mitigate Osimertinib's toxicity caused by AZ5104, the N-demethylation metabolite of Osimertinib, we designed and synthesized a series of Osimertinib analogs with different headpieces. In vitro and in vivo analysis rendered a potential clinical candidate C-005 which had pyrrolo-pyridine headpiece. Biochemically, C-005 and its main human hepatocyte metabolite showed over 30 fold selectivity of L858R/T790M mutant EGFR over WT EGFR. Such selectivity profile was retained at cellular level. In general, C-005 is 2-14 fold more selective than Osimertinib in a panel of WT EGFR cancer cell lines. Furthermore, C-005 demonstrated robust antitumor efficacy and good tolerability in NCI-H1975, PC-9 and HCC827 xenograft mouse models, making it a potential candidate for human test in clinical.

Structural insights into drug development strategy targeting EGFR T790M/C797S

Treatment of non-small-cell lung cancers (NSCLCs) harboring primary EGFR oncogenic mutations such as L858R and exon 19 deletion delE746_A750 (Del-19) using gefitinib/erlotinib ultimately fails due to the emergence of T790M mutation. Though WZ4002/CO-1686/AZD9291 are effective in overcoming EGFR T790M by targeting Cys797 via covalent bonding, their efficacy is again limited due to the emergence of C797S mutation. New agents effectively inhibiting EGFR T790M without covalent linkage through Cys 797 may solve this problem. We presented here crystal structures of EGFR activating/drug-resistant mutants in complex with a panel of reversible inhibitors along with mutagenesis and enzyme kinetic data. These data revealed a previously un-described hydrophobic clamp structure in the EGFR kinase which may be exploited to facilitate development of next generation drugs targeting EGFR T790M with or without concomitant C797S. Interestingly, mutations in the hydrophobic clamp that hinder drug binding often also weaken ATP binding and/or abolish kinase activity, thus do not readily result in resistance to the drugs.

Current progress and outcomes of clinical trials on using epidermal growth factor receptor-tyrosine kinase inhibitor therapy in non-small cell lung cancer patients with brain metastases

Non-small cell lung cancer (NSCLC) continues to be one of the major causes of cancer-related deaths worldwide, and brain metastases are the major cause of death in NSCLC patients. With recent advances in understanding the underlying molecular mechanism of NSCLC development and progression, mutations in epidermal growth factor receptor (EGFR) have been recognized as a key predictor of therapeutic sensitivity to EGFR tyrosine kinase inhibitors (TKIs). Using EGFR-TKI alone or in combination with standard treatments such as whole-brain radiotherapy and surgery has been an effective strategy for the management of brain metastasis. Particularly, a newer generation of EGFR-TKIs, including osimertinib and AZD3759, has been developed. These new EGFR-TKIs can cross the blood-brain barrier and potentially treat EGFR-TKI resistance and improve prognosis. In this article, current progress and outcomes of clinical trials on the use of EGFR-TKIs for treating NSCLC patients with brain metastasis will be reviewed.

Overall survival in EGFR mutated non-small-cell lung cancer patients treated with afatinib after EGFR TKI and resistant mechanisms upon disease progression

PURPOSE

To determine survival in afatinib-treated patients after treatment with first-generation EGFR tyrosine kinase inhibitors (TKIs) and to study resistance mechanisms in afatinib-resistant tumors.

METHODS

Characteristics and survival of patients treated with afatinib after resistance to erlotinib or gefitinib in two large Dutch centers were collected. Whole exome sequencing (WES) and pathway analysis was performed on available pre- and post-afatinib tumor biopsies and normal tissue.

RESULTS

A total of 38 patients were treated with afatinib. T790M mutations were identified in 22/29 (76%) pre-afatinib treatment tumor samples. No difference in median progression-free-survival (2.8 months (95% CI 2.3-3.3) and 2.7 months (95% CI 0.9-4.6), p = 0.55) and median overall-survival (8.8 months (95% CI 4.2-13.4) and 3.6 months (95% CI 2.3-5.0), p = 0.14) were observed in T790M+ patients compared to T790M- mutations. Somatic mutations in TP53, ADAMTS2, CNN2 and multiple genes in the Wnt and PI3K-AKT pathway were observed in post-afatinib tumors of six afatinib-responding and in one non-responding patient. No new EGFR mutations were found in the post-afatinib samples of the six responding patients. Further analyses of post-afatinib progressive tumors revealed 28 resistant specific mutations in six genes (HLA-DRB1, AQP7, FAM198A, SEC31A, CNTLN, and ESX1) in three afatinib responding patients. No known EGFR-TKI resistant-associated copy number gains were acquired in the post-afatinib samples.

CONCLUSION

No differences in survival were observed in patients with EGFR-T790M treated with afatinib compared to those without T790M. Tumors from patients who had progressive disease during afatinib treatment were enriched for mutations in genes involved in Wnt and PI3K-AKT pathways.

Brigatinib combined with anti-EGFR antibody overcomes osimertinib resistance in EGFR-mutated non-small-cell lung cancer

Osimertinib has been demonstrated to overcome the epidermal growth factor receptor (EGFR)-T790M, the most relevant acquired resistance to first-generation EGFR-tyrosine kinase inhibitors (EGFR-TKIs). However, the C797S mutation, which impairs the covalent binding between the cysteine residue at position 797 of EGFR and osimertinib, induces resistance to osimertinib. Currently, there are no effective therapeutic strategies to overcome the C797S/T790M/activating-mutation (triple-mutation)-mediated EGFR-TKI resistance. In the present study, we identify brigatinib to be effective against triple-mutation-harbouring cells in vitro and in vivo. Our original computational simulation demonstrates that brigatinib fits into the ATP-binding pocket of triple-mutant EGFR. The structure-activity relationship analysis reveals the key component in brigatinib to inhibit the triple-mutant EGFR. The efficacy of brigatinib is enhanced markedly by combination with anti-EGFR antibody because of the decrease of surface and total EGFR expression. Thus, the combination therapy of brigatinib with anti-EGFR antibody is a powerful candidate to overcome triple-mutant EGFR.

New strategies to develop new medications for lung cancer and metastasis

With the advances in cancer and molecular biology and the rapid progress in genomics, significant progress has been made in the treatment of lung cancer in the past decade. Targeted therapies have been developed for nonsmall cell lung cancer (NSCLC), and significant improvement in survival has been achieved. There is still, however, no cure for advanced NSCLC. Resistance to initial therapy is universal, and the lethal outcome of metastatic disease still remains. Approaches to preventing metastases and overcoming resistance to therapy are necessary to ensure long-term survival of patients with advanced lung cancer.

Study of efficacy and safety of pulsatile administration of high-dose gefitinib or erlotinib for advanced non-small cell lung cancer patients with secondary drug resistance: A single center, single arm, phase II clinical trial

Background

The objective of the study was to observe the efficacy and safety of pulsatile administration of high‐dose gefitinib or erlotinib in patients with advanced non‐small cell lung cancer (NSCLC) with secondary drug resistance to standard doses of tyrosine kinase inhibitor (TKI) treatment.

Materials and methods

We recruited 42 NSCLC patients from our hospital, between August 2014 and December 2015, who had experienced drug resistance after one year of conventional treatment with gefitinib or erlotinib. The gefitinib group (29 patients) received one dose of 1000 mg gefitinib every four days. The erlotinib group (13 patients) received one dose of 450 mg erlotinib every three days. Treatments continued until disease progression according to Response Evaluation Criteria In Solid Tumors 1.1 or development of intolerable toxicity.

Results

Median progression‐free survival (PFS) was 30 months (gefitinib vs. erlotinib: 31 vs. 24 months; P > 0.05). After high‐dose pulsatile administration, eight patients achieved a partial response (PR), 11 had stable disease (SD), and 23 had progressive disease (PD; relative risk 19.0%; disease control rate 45.2%; median PFS six months). Patients were categorized based on epidermal growth factor receptor gene mutation: exon 19 (no patients achieved complete response [CR], 4 PR, 6 SD, and 17 PD) and exon 21 mutation groups (no patients achieved CR, 4 PR, 5 SD, and 6 PD).

Conclusion

High‐dose TKI pulsatile treatment is safe, efficient, and can improve prognoses for certain patients with advanced NSCLC.

Next-Generation Covalent Irreversible Kinase Inhibitors in NSCLC: Focus on Afatinib

First-generation, reversible epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs), erlotinib and gefitinib, represented an important addition to the treatment armamentarium for non-small-cell lung cancer (NSCLC) patients with activating EGFR mutations. However, all patients inevitably develop acquired resistance to these agents, primarily due to secondary EGFR mutations, molecular aberrations affecting other signaling pathways, or transformation to small-cell histology. It was hypothesized that development of second-generation TKIs with broader inhibitory profiles could confer longer-lasting clinical activity and overcome acquired resistance to first-generation inhibitors. Here, we review the development of afatinib, an irreversible ErbB family blocker that potently inhibits signaling of all homodimers and heterodimers formed by the EGFR, human epidermal growth factor receptor (HER)-2, HER3, and HER4 receptors. In two phase III trials in patients with EGFR mutation-positive NSCLC, first-line afatinib significantly improved progression-free survival (PFS) and health-related quality of life versus standard-of-care chemotherapy. Moreover, in preplanned sub-analyses, afatinib significantly improved overall survival in patients harboring EGFR Del19 mutations. Afatinib has also demonstrated clinical activity in NSCLC patients who had progressed on erlotinib/gefitinib, particularly when combined with cetuximab, and offers ‘treatment beyond progression’ benefit when combined with paclitaxel versus chemotherapy alone. Furthermore, a recent phase III study demonstrated that PFS was significantly improved with afatinib versus erlotinib for the second-line treatment of patients with squamous cell carcinoma of the lung. The activity of afatinib in both first-line and relapsed/refractory settings may reflect its ability to irreversibly inhibit all ErbB family members. Afatinib has a well-defined safety profile with characteristic gastrointestinal (diarrhea, stomatitis) and cutaneous (rash/acne) adverse events.

Advances in EGFR as a Predictive Marker in Lung Adenocarcinoma

BACKGROUND

Worldwide, lung cancer is the most common cause of mortality. Toxins from tobacco smoke are known to increase the risk of lung cancer; however, up to 15% of lung cancer-related deaths in men and up to 50% of lung cancer-related deaths in women occur in people who do not smoke. Despite the fact that chemotherapy generally provides a survival benefit for non-small-cell lung cancer, not every patient will respond to therapy and many experience therapy-related adverse events. Thus, predictive markers are used to determine which patients are more likely to respond to a given regimen.

METHODS

We reviewed the current medical literature in English relating to predictive markers that may be positive, such as the presence of an activating EGFR mutation.

RESULTS

The advances in using EGFR as a molecular predictive marker were summarized. This biomarker influences therapeutic response in patients with lung adenocarcinoma. Clinical evidence supporting its value is also reviewed.

CONCLUSIONS

The use of EGFR as a predictive factor in lung adenocarcinoma may help target therapy to individual tumors to achieve the best likelihood for long-term survival and to avoid adverse events from medications unlikely to be effective.

EGFR: The Paradigm of an Oncogene-Driven Lung Cancer

Somatic, activating mutations in EGFR identify a significant minority of patients with non-small cell lung cancer (NSCLC). Although these mutations are associated with an approximately 70% response rate to some EGFR tyrosine kinase inhibitors (gefitinib, erlotinib, and afatinib), patients develop resistance (i.e., "acquired resistance") after a median of 9 to 12 months. In patients with clinical acquired resistance, repeat biopsy of tumors has identified a number of relevant mechanisms of resistance, but by far the most frequent event is the acquisition of EGFR T790M, a mutation in the "gatekeeper" residue that confers resistance to gefitinib, erlotinib, and afatinib. This emphasizes the critical dependence upon EGFR signaling for some tumors, a property that has been exploited therapeutically. Dual EGFR blockade using afatinib and cetuximab led to a 29% radiographic response rate. More recently, drugs that target EGFR T790M (e.g., rociletinib, AZD9291, and others) have entered clinical trials, with impressive results observed in phase I clinical trials. The development of these newer drugs, with efficacy after resistance to first-line EGFR tyrosine kinase inhibitor, has led to exploration of these strategies in multiple disease settings: at resistance, in the first line, and in adjuvant treatment of those with completely resected early-stage disease who would otherwise die of recurrent/metastatic disease. This example of translational research that identifies mechanisms of resistance to first-generation drugs, and then targets those mechanisms yielding clinical benefit, is a paradigm for how targeted therapies can be developed.

Combined Pan-HER and ALK/ROS1/MET Inhibition with Dacomitinib and Crizotinib in Advanced Non-Small Cell Lung Cancer: Results of a Phase I Study

INTRODUCTION

This phase I study investigated the activity of the irreversible pan-human epidermal growth factor receptor inhibitor dacomitinib in combination with the mesenchymal-epithelial transition factor/anaplastic lymphoma kinase/ROS proto-oncogene 1, receptor tyrosine kinase inhibitor crizotinib in advanced non-small cell lung cancer.

METHODS

Patients with progression after at least one line of chemotherapy or targeted therapy received dacomitinib once daily and crizotinib once daily or twice daily, with doses escalated until intolerable toxicity; the expansion cohorts received the maximum tolerated dose of the combination. The primary objective was to define the recommended phase II dose; secondary objectives included assessment of safety and activity of the combination in epidermal growth factor receptor inhibitor-resistant patients and correlation with tumor biomarkers.

RESULTS

Seventy patients were treated in the dose-escalation (n = 33) and expansion phases (n = 37), with the maximum tolerated dose defined as dacomitinib, 30 mg once daily, plus crizotinib, 200 mg twice daily. Grade 3 or 4 treatment-related adverse events were reported in 43% of patients: the most common were diarrhea (16%), rash (7%), and fatigue (6%). There were 16 deaths; none were considered treatment related. One patient (1%) had a partial response; 46% had stable disease. Most of the tumor samples analyzed had activating epidermal growth factor receptor gene (EGFR) mutations (18 of 20 [90%]); 50% (10 of 20) had a concurrent resistance mutation. Only one sample showed MMNG HOS Transforming gene (MET) amplification (the patient had progressive disease), whereas 59% (13 of 22) and 47% (14 of 30) had high levels of expression of epidermal growth factor receptor and mesenchymal-epithelial transition factor on the basis of H-scores, respectively. There was no apparent association between biomarker expression and antitumor activity.

CONCLUSION

The combination of dacomitinib and crizotinib showed limited antitumor activity in patients with advanced non-small cell lung cancer and was associated with substantial toxicity.

Beyond "second-line" in non-small cell lung cancer: therapy and supportive care

Although there once was a single algorithm for the treatment of patients with advanced lung cancer, the modern treatment of advanced lung cancer has multiple treatment pathways that depend on multiple factors, including histology and molecular subtype of disease. New molecular targets, targeted agents, and modes of therapy for patients, including immunotherapy, are being identified at an accelerating pace. These advances are changing outcomes and the treatment landscape, but they also highlight situations with inadequate data to support the use of cytotoxic chemotherapy. In this article, we provide an overview of data regarding cytotoxic chemotherapy and targeted therapy and their value after second line, review the critical role of supportive care and palliative care, and emphasize the importance of advance care planning with our patients. Although this article focuses primarily on NSCLC, the comments about palliative care and advanced care planning also apply to patients with small cell lung cancer.

Advances in molecular biology of lung disease: aiming for precision therapy in non-small cell lung cancer

Lung cancer is the principal cause of cancer-related mortality in the developed world, accounting for almost one-quarter of all cancer deaths. Traditional treatment algorithms have largely relied on histologic subtype and have comprised pragmatic chemotherapy regimens with limited efficacy. However, because our understanding of the molecular basis of disease in non-small cell lung cancer (NSCLC) has improved exponentially, it has become apparent that NSCLC can be radically subdivided, or molecularly characterized, based on recurrent driver mutations occurring in specific oncogenes. We know that the presence of such mutations leads to constitutive activation of aberrant signaling proteins that initiate, progress, and sustain tumorigenesis. This persistence of the malignant phenotype is referred to as "oncogene addiction." On this basis, a paradigm shift in treatment approach has occurred. Rational, targeted therapies have been developed, the first being tyrosine kinase inhibitors (TKIs), which entered the clinical arena > 10 years ago. These were tremendously successful, significantly affecting the natural history of NSCLC and improving patient outcomes. However, the benefits of these drugs are somewhat limited by the emergence of adaptive resistance mechanisms, and efforts to tackle this phenomenon are ongoing. A better understanding of all types of oncogene-driven NSCLC and the occurrence of TKI resistance will help us to further develop second- and third-generation small molecule inhibitors and will expand our range of precision therapies for this disease.

Resistance to Therapy

Identification of driver mutations in adenocarcinoma of the lung has revolutionized the treatment of this disease. It is now standard of care to look for activating mutations in epidermal growth factor receptor (EGFR), and translocations in anaplastic lymphoma kinase (ALK) or ROS1 in all newly diagnosed adenocarcinoma of the lung, and in many patients with squamous cell carcinoma as well. Recognition of multiple other lung cancer driver mutations has also expanded treatment options. Targeted treatments of these mutations lead to rapid and prolonged responses, but resistance inevitably develops. Until recently, traditional chemotherapy was the only alternative at that time, but better understanding of resistance mechanisms has lead to additional therapeutic options. These mechanisms of resistance and treatments are the focus of this chapter. Understanding of mechanisms of chemotherapy resistance is touched upon, along with a brief discussion of immune checkpoint inhibitors.

Noncovalent Mutant Selective Epidermal Growth Factor Receptor Inhibitors: A Lead Optimization Case Study

Because of their increased activity against activating mutants, first-generation epidermal growth factor receptor (EGFR) kinase inhibitors have had remarkable success in treating non-small-cell lung cancer (NSCLC) patients, but acquired resistance, through a secondary mutation of the gatekeeper residue, means that clinical responses only last for 8-14 months. Addressing this unmet medical need requires agents that can target both of the most common double mutants: T790M/L858R (TMLR) and T790M/del(746-750) (TMdel). Herein we describe how a noncovalent double mutant selective lead compound was optimized using a strategy focused on the structure-guided increase in potency without added lipophilicity or reduction of three-dimensional character. Following successive rounds of design and synthesis it was discovered that cis-fluoro substitution on 4-hydroxy- and 4-methoxypiperidinyl groups provided synergistic, substantial, and specific potency gain through direct interaction with the enzyme and/or effects on the proximal ligand oxygen atom. Further development of the fluorohydroxypiperidine series resulted in the identification of a pair of diastereomers that showed 50-fold enzyme and cell based selectivity for T790M mutants over wild-type EGFR (wtEGFR) in vitro and pathway knock-down in an in vivo xenograft model.

What is the best strategy for targeting EGF receptors in non-small-cell lung cancer?

EGF receptors (EGFRs) are often overexpressed or constitutively activated in non-small-cell lung cancer, and are an important therapeutic target. EGFR signaling can be blocked with tyrosine kinase inhibitors (TKIs) and anti-EGFR antibodies. Three EGFR-TKIs are approved as initial monotherapies in patients with EGFR-activating mutations, and erlotinib has a role as maintenance and second-line therapy. Investigational anti-EGFR monoclonal antibodies plus standard first-line therapy improve survival in patients with advanced non-small-cell lung cancer, especially in tumors with high EGFR expression. Anti-EGFR antibodies inhibit EGFR signaling and have the potential to stimulate antibody-dependent cell-mediated cytotoxicity. Multikinase TKIs are investigational as first- and second-line therapies, as monotherapies and in combination with chemotherapy. This article summarizes the available clinical data for EGFR-targeted therapies.

Key drivers of biomedical innovation in cancer drug discovery

Discovery and translational research has led to the identification of a series of “cancer drivers”—genes that, when mutated or otherwise misregulated, can drive malignancy. An increasing number of drugs that directly target such drivers have demonstrated activity in clinical trials and are shaping a new landscape for molecularly targeted cancer therapies. Such therapies rely on molecular and genetic diagnostic tests to detect the presence of a biomarker that predicts response. Here, we highlight some of the key discoveries bringing precision oncology to cancer patients. Large-scale “omics” approaches as well as modern, hypothesis-driven science in both academic and industry settings have significantly contributed to the field. Based on these insights, we discuss current challenges and how to foster future biomedical innovation in cancer drug discovery and development.

[Is chemotherapy still an option in oncogene-addicted non-small cell lung cancer? No]

With the emergence of molecular targeted therapies in the management of non-small cell lung cancer, the role of conventional chemotherapy can be questioned. This article presents the key arguments against the use of cytotoxics in presence of a targetable alteration.

Progression-Free and Overall Survival in ALK-Positive NSCLC Patients Treated with Sequential Crizotinib and Ceritinib

PURPOSE

Anaplastic lymphoma kinase (ALK) rearrangements are important therapeutic targets in non-small cell lung cancer (NSCLC) that confer sensitivity to the ALK inhibitors crizotinib and ceritinib. To determine the outcome of sequential treatment with crizotinb and ceritinib, we retrospectively evaluated a cohort of ALK-positive patients treated with both agents.

EXPERIMENTAL DESIGN

We identified 73 ALK-positive NSCLC patients treated with crizotinib followed by ceritinib at four institutions. Medical records were reviewed to determine overall survival (OS) and progression-free survival (PFS) on crizotinib and ceritinib.

RESULTS

Among 73 ALK-positive patients, the median PFS (mPFS) on crizotinib was 8.2 months [95% confidence interval (CI), 7.4-10.6]. The median interval from crizotinib discontinuation to initiation of ceritinib was 25 days (range, 1-694). The mPFS on ceritinib was 7.8 months (6.5-9.1). Among 53 patients with no interval therapies between crizotinib and ceritinib, the mPFS on ceritinib was similar at 7.8 months (5.4-9.8). The median combined PFS for sequential treatment with crizotinib and ceritinib was 17.4 months (15.5-19.4). Among 23 patients who underwent post-crizotinib/pre-ceritinib biopsies, there was no difference in PFS on ceritinib between patients with or without ALK resistance mutations (mPFS 5.8 vs. 6.5 months, respectively; P = 0.510). In the overall study population, median OS was 49.4 months (35.5-63.1).

CONCLUSIONS

Ceritinib has significant antitumor activity in ALK-positive NSCLC-even when crizotinib immediately precedes treatment with ceritinib (median combined PFS 17.0 months). Additional studies are necessary to further define the impact of specific ALK resistance mutations on duration of response to ceritinib.

Strategies to overcome resistance to tyrosine kinase inhibitors in non-small-cell lung cancer

The use of molecularly targeted agents has dramatically improved the prognosis of defined subsets of patients with non-small-cell lung cancer harboring somatically activated oncogenes, such as mutant EGFR or rearranged ALK. However, after initial marked responses to EGFR or ALK tyrosine kinase inhibitors (TKIs), almost all patients inevitably progress due to development of acquired resistance. Multiple molecular mechanisms of resistance have been identified; the best characterized are secondary mutations in the tyrosine kinase domain of the oncogene, such as T790M in EGFR and L1196M in ALK, which prevent target inhibition by the corresponding TKI. Other mechanisms include copy number gain of the ALK fusion gene and the activation of bypass signaling pathways that can maintain downstream proliferation and survival signals despite inhibition of the original drug target. Here, the authors provide an overview of the known mechanisms of resistance to TKIs and outline the therapeutic strategies, including new investigational agents and targeted therapies combinations, that have been developed to overcome resistance.

Non-small-cell lung cancer

Lung cancer is one of the most frequently diagnosed cancers and is the leading cause of cancer-related death worldwide. Non-small-cell lung cancer (NSCLC), a heterogeneous class of tumours, represents approximately 85% of all new lung cancer diagnoses. Tobacco smoking remains the main risk factor for developing this disease, but radon exposure and air pollution also have a role. Most patients are diagnosed with advanced-stage disease owing to inadequate screening programmes and late onset of clinical symptoms; consequently, patients have a very poor prognosis. Several diagnostic approaches can be used for NSCLC, including X-ray, CT and PET imaging, and histological examination of tumour biopsies. Accurate staging of the cancer is required to determine the optimal management strategy, which includes surgery, radiochemotherapy, immunotherapy and targeted approaches with anti-angiogenic monoclonal antibodies or tyrosine kinase inhibitors if tumours harbour oncogene mutations. Several of these driver mutations have been identified (for example, in epidermal growth factor receptor (EGFR) and anaplastic lymphoma kinase (ALK)), and therapy continues to advance to tackle acquired resistance problems. Also, palliative care has a central role in patient management and greatly improves quality of life. For an illustrated summary of this Primer, visit: http://go.nature.com/rWYFgg.

Phase I/II Study of HSP90 Inhibitor AUY922 and Erlotinib for EGFR-Mutant Lung Cancer With Acquired Resistance to Epidermal Growth Factor Receptor Tyrosine Kinase Inhibitors

PURPOSE

AUY922 is an HSP90 inhibitor that causes degradation of HSP chaperones and their client proteins, including epidermal growth factor receptor. We conducted a phase I/II trial to evaluate AUY922 and erlotinib for patients with EGFR-mutant lung cancer and disease progression during erlotinib treatment.

PATIENTS AND METHODS

All patients had developed acquired resistance after treatment with erlotinib and underwent repeat tumor biopsies before study entry to assess for EGFR T790M. In phase I, 18 patients were treated with AUY922 intravenously once per week and erlotinib once per day in 28-day cycles using a 3 + 3 dose-escalation design. In phase II, 19 additional patients were treated at the maximum-tolerated dose. The primary end point of the phase II trial was complete plus partial response rate.

RESULTS

In phase I (n = 18), three patients were treated in each cohort, except the highest-dose cohort (AUY922 70 mg and erlotinib 150 mg), which expanded to six patients because of a dose-limiting toxicity (ie, junctional cardiac rhythm). Common drug-related adverse events were diarrhea, skin rash, hyperglycemia, and night blindness. All patients treated at maximum-tolerated dose (n = 25) were evaluable for response. The partial response rate was 16% (four of 25 patients; 95% CI, 5% to 36%) and was independent of tumor T790M status.

CONCLUSION

Partial responses were observed, but the duration of treatment with AUY922 and erlotinib was limited by toxicities, especially night blindness. This phase II study of AUY922 and erlotinib did not meet its primary end point.

Fighting cancer drug resistance: Opportunities and challenges for mutation-specific EGFR inhibitors

Multiple mutations in the EGFR gene are a major cause for the failure of Erlotinib and Gefitinib in the treatment of patients harboring non-small-cell lung cancer (NSCLC) who initially responded to this therapy. The development of these tyrosine kinase inhibitors (TKIs) is going back to the early 90s, where cancer was widely considered and fully treated as a disease of an organ. Fundamental gain of knowledge in cell biology in general and cancer genetics in particular led us to where we currently stand: cancer is a disease that originates in the genome. Fast and affordable gene sequencing paved the way and opened our eyes for the genetic instability of many cancers, particularly EGFR driven NSCLC. This might allow highly rational and personal therapies by aiming at a very particular wild type and mutant kinase pattern. However, the paradigm "one disease - one target - one drug" is currently challenged. Both activating and deactivating EGFR mutations are known to render the development of novel targeted drugs difficult. Among all lung adenocarcinomas, only 20% are driven by EGFR and only a subpopulation has an activating mutation (e.g. L858R), making them sensitive to first generation EGFR inhibitors. Unfortunately, most of them acquire second deactivating mutations (e.g. T790M) during treatment, leading to a complete loss of response. Are specific inhibitors of the double EGFR mutant L858R/T790M the magic bullet? Much scientific evidence but also high expectations justify this approach. Structural biology of EGFR mutants constitutes the basis for highly rational approaches. Second generation pan EGFR inhibitors inhibiting wild type (WT) and mutant EGFR like Afatinib suffer from dose-limiting adverse effects. Inhibition of WT EGFR is considered to be the culprit. Third generation EGFR inhibitors follow two strategies. Mutant selectivity and improved target residential time. These inhibitors display high mutant selectivity and irreversible binding patterns while sparing WT EGFR activity, hence enhancing tumor selectivity while minimizing adverse effects. Third generation EGFR inhibitors are still undergoing preclinical and clinical evaluation. The most advanced are Rociletinib and AZD9291 which displayed encouraging preliminary clinical phase II data regarding response and adverse effects. In the current review we show both a medicinal chemists' approach toward the design of third generation EGFR inhibitors as well as a detailed overview of the development of EGFR inhibitors over the last decade. High interdisciplinary approaches, such as structural biology and time-resolved tumor genetics pave the way toward the development of drugs that target EGFR mutants. This might lead to highly effective targeted and personalized therapies with enhanced response rates for a minor cohort of patients which have to undergo continuous gene sequencing, hence enabling therapies with tailor-made TKIs.

Refining the treatment of NSCLC according to histological and molecular subtypes

In the past decade, the characterization of non-small-cell lung cancer (NSCLC) into subtypes based on genotype and histology has resulted in dramatic improvements in disease outcome in select patient subgroups. In particular, molecularly targeted agents that inhibit EGFR or ALK are approved for the treatment of NSCLC harbouring genetic alterations in the genes encoding these proteins. Although acquired resistance usually limits the duration of response to these therapies, a number of new agents have proven effective at tackling specific resistance mechanisms to first-generation inhibitors. Large initiatives are starting to address the role of biomarker-driven targeted therapy in squamous lung cancers, and in the adjuvant setting. Immunotherapy undeniably holds great promise and our understanding of subsets of NSCLC based on patterns of immune response is continuing to evolve. In addition, efforts are underway to identify rare genomic subsets through genomic screening, functional studies, and molecular characterization of exceptional responders. This Review provides an overview of the key developments in the treatment of NSCLC, and discusses potential strategies to further optimize therapy by targeting disease subtypes.

Ultra-Sensitive Detection of the Pretreatment EGFR T790M Mutation in Non-Small Cell Lung Cancer Patients with an EGFR-Activating Mutation Using Droplet Digital PCR

PURPOSE

The resistance to the EGFR tyrosine kinase inhibitors (TKI) is a major concern in non-small cell lung cancer (NSCLC) treatment. T790M mutation in EGFR accounts for nearly 50% of the acquired resistance to EGFR-TKIs. Earlier studies suggested that T790M mutation was also detected in TKI-naïve NSCLCs in a small cohort. Here, we use an ultra-sensitive droplet digital PCR (ddPCR) technique to address the incidence and clinical significance of pretreatment T790M in a larger cohort.

EXPERIMENTAL DESIGN

ddPCR was established as follows: wild-type or T790M mutation-containing DNA fragments were cloned into plasmids. Candidate threshold was identified using wild-type plasmid, normal human genomic DNA, and human A549 cell line DNA, which expresses wild type. Surgically resected tumor tissues from 373 NSCLC patients with EGFR-activating mutations were then examined for the presence of T790M using ddPCR.

RESULTS

Our data revealed a linear performance for this ddPCR method (R(2) = 0.998) with an analytical sensitivity of approximately 0.001%. The overall incidence of the pretreatment T790M mutation was 79.9% (298/373), and the frequency ranged from 0.009% to 26.9%. The T790M mutation was detected more frequently in patients with a larger tumor size (P = 0.019) and those with common EGFR-activating mutations (P = 0.022), as compared with the others.

CONCLUSIONS

The ultra-sensitive ddPCR assay revealed that pretreatment T790M was found in the majority of NSCLC patients with EGFR-activating mutations. ddPCR should be utilized for detailed assessment of the impact of the low frequency pretreatment T790M mutation on treatment with EGFR-TKIs.

Precision Therapy for Lung Cancer: Tyrosine Kinase Inhibitors and Beyond

For patients with advanced cancers there has been a concerted effort to transition from a generic treatment paradigm to one based on tumor-specific biologic, and patient-specific clinical characteristics. This approach, known as precision therapy has been made possible owing to widespread availability and a reduction in the cost of cutting-edge technologies that are used to study the genomic, proteomic, and metabolic attributes of individual tumors. This review traces the evolution of precision therapy for lung cancer from the identification of molecular subsets of the disease to the development and approval of tyrosine kinase, as well as immune checkpoint inhibitors for lung cancer therapy. Challenges of the precision therapy era including the emergence of acquired resistance, identification of untargetable mutations, and the effect on clinical trial design are discussed. We conclude by highlighting newer applications for the concept of precision therapy.

Multiple oncogenic mutations related to targeted therapy in nasopharyngeal carcinoma

INTRODUCTION

An increasing number of targeted drugs have been tested for the treatment of nasopharyngeal carcinoma (NPC). However, targeted therapy-related oncogenic mutations have not been fully evaluated. This study aimed to detect targeted therapy-related oncogenic mutations in NPC and to determine which targeted therapy might be potentially effective in treating NPC.

METHODS

By using the SNaPshot assay, a rapid detection method, 19 mutation hotspots in 6 targeted therapy-related oncogenes were examined in 70 NPC patients. The associations between oncogenic mutations and clinicopathologic factors were analyzed.

RESULTS

Among 70 patients, 12 (17.1%) had mutations in 5 oncogenes: 7 (10.0%) had v-kit Hardy-Zuckerman 4 feline sarcoma viral oncogene homolog (KIT) mutation, 2 (2.8%) had epidermal growth factor receptor (EGFR) mutation, 1 (1.4%) had phosphatidylinositol-4,5-bisphosphate 3-kinase, catalytic subunit alpha (PIK3CA) mutation, 1 (1.4%) had Kirsten rat sarcoma viral oncogene homolog (KRAS) mutation, and 1 (1.4%) had simultaneous EGFR and v-Raf murine sarcoma viral oncogene homolog B1 (BRAF) mutations. No significant differences were observed between oncogenic mutations and clinicopathologic characteristics. Additionally, these oncogenic mutations were not associated with tumor recurrence and metastasis.

CONCLUSIONS

Oncogenic mutations are present in NPC patients. The efficacy of targeted drugs on patients with the related oncogenic mutations requires further validation.

The anticipated next season of EGFR inhibitors

EGFR-directed therapy in lung cancer is here to stay, with new drugs targeting T790M-mediated resistance coming quickly and the field continuing to advance. With greater access to sophisticated tools for interrogating both the somatic and germline genome, and with widespread acceptance of the scientific and clinical value of obtaining serial repeated biopsies from patients with oncogene-addicted tumors, the field is poised to answer more nuanced questions.

New insights into the molecular profile of lung adenocarcinoma and implications for therapy

Lung cancer is a molecularly heterogeneous disease. The advent of next-generation sequencing techniques has significantly advanced our understanding of the complex molecular underpinnings of lung cancer. Furthermore, the development of targeted therapies has significantly altered the landscape of lung cancer therapy over the past decade. There is hence an increasing interest in developing a classification system that guides clinical management and also incorporates relevant genomic information. Here, we highlight the molecular features of lung adenocarcinoma as highlighted by several independent groups, and more recently The Cancer Genome Atlas and discuss their potential clinical significance.

Detecting resistance in EGFR-mutated non-small-cell lung cancer after clonal selection through targeted therapy

Tumor heterogeneity plays an important role in the development of treatment-resistance, especially in the current era of targeted therapies. Although tumor heterogeneity is a widely recognized phenomenon, it is at present unclear how this knowledge should be incorporated into daily clinical practice. In this report, we describe an innovative nuclear imaging method that may play a role in detecting tumor heterogeneity in the future.

Management of EGFR mutated nonsmall cell lung carcinoma patients

Tyrosine kinase inhibitors (TKIs) targeting the epidermal growth factor receptor (EGFR) are common in the therapeutic armentarium of lung cancer today. Initially tested in an unselected population, they have been of limited usefulness until the identification EGFR gene mutations. Activating mutations generate conformational changes that result in a shift toward an active state of the catalytic domain and are associated with sensitivity to first generation EGFR TKI. Other mutations have been associated with resistance to these drugs, but for rare mutations there is limited data concerning their role in predicting response to EGFR TKI. To date, four molecules have been approved for the treatment of EGFR mutated lung cancer. Gefitinib and/or erlotinib are available in almost all countries. Afatinib has been approved by the US Food and Drug Administration and by the European Medicines Agency, and icotinib has been approved only in China. Other, more active, third generation agents with a higher binding affinity for the receptor, or that are directed against specific mutations, are under development. EGFR TKIs have a favourable impact on progression-free survival when given as first line treatment in mutated patients, but may also have a moderate effect as a salvage therapy and in maintenance in an unselected population.

Phase II study of afatinib, an irreversible ErbB family blocker, in demographically and genotypically defined lung adenocarcinoma

OBJECTIVES

Afatinib, an oral irreversible ErbB family blocker, has demonstrated efficacy in patients with epidermal growth factor receptor (EGFR) mutation-positive advanced lung adenocarcinoma. Other potential biomarkers predicting response to afatinib, such as human epidermal growth factor receptor-2 (HER2) mutations and EGFR gene amplification, have not been validated yet. This phase II study investigated whether afatinib conferred clinical benefit in cohorts of adenocarcinoma patients with: (1) EGFR mutation and failing on erlotinib/gefitinib; or (2) increased copy number of EGFR by fluorescence in situ hybridization (FISH); or (3) HER2 mutation.

MATERIALS AND METHODS

Patients started daily afatinib 50mg monotherapy. Upon disease progression, patients could continue, at the investigator's discretion, afatinib (40mg) with the addition of paclitaxel (80mg/m(2) weekly for 3 weeks/4-week cycle). Endpoints included confirmed objective response (OR), progression-free survival (PFS), disease control, and safety.

RESULTS

Of 41 patients treated (cohort 1: n=32; cohort 2: n=2; cohort 3: n=7), 33 received afatinib monotherapy; eight subsequently received afatinib plus paclitaxel. With afatinib monotherapy, one patient achieved a confirmed OR (partial response [PR]; cohort 2). Two further patients achieved unconfirmed PRs (one each in cohort 1 and cohort 3). Disease control was achieved by 17/32 (53%), 2/2 (100%) and 5/7 (71%) patients in cohorts 1, 2 and 3, respectively. In patients receiving combination therapy (median PFS: 6.7 weeks), one (cohort 3) had confirmed PR of 41.9 weeks. The most common afatinib-related adverse events were diarrhea (95%) and rash/acne (80%).

CONCLUSION

Afatinib demonstrated signs of clinical activity in heavily pretreated patients with activating HER2 or EGFR mutations or EGFR FISH-positive tumors.

Molecularly targeted therapies in non-small-cell lung cancer annual update 2014

There have been significant advances in the understanding of the biology and treatment of non-small-cell lung cancer (NSCLC) during the past few years. A number of molecularly targeted agents are in the clinic or in development for patients with advanced NSCLC. We are beginning to understand the mechanisms of acquired resistance after exposure to tyrosine kinase inhibitors in patients with oncogene addicted NSCLC. The advent of next-generation sequencing has enabled to study comprehensively genomic alterations in lung cancer. Finally, early results from immune checkpoint inhibitors are very encouraging. This review summarizes recent advances in the area of cancer genomics, targeted therapies, and immunotherapy.

Developing biomarker-specific end points in lung cancer clinical trials

In cancer-drug development, a number of different end points have been used to establish efficacy and support regulatory approval, such as overall survival, progression-free survival (PFS), and radiographic response rate. However, these traditional end points have important limitations. For example, in lung cancer clinical trials, evaluating overall survival end points is a protracted process and these end points are most reliable when crossover to the investigational therapy is not permitted. Furthermore, although radiographic surrogate end points, such as PFS and response rate, generally correlate with clinical benefit in the setting of cytotoxic chemotherapy and molecular targeted therapies, novel immunotherapies might have atypical response kinetics, which confounds radiographic interpretation. In this Review, we discuss the need to develop alternative or surrogate end points for lung cancer clinical trials, and focus on several new biomarkers that could serve as surrogate end points, including functional imaging biomarkers, circulating factors (tumour proteins, DNA, and cells), and pharmacodynamic tumour markers. By enabling the size, duration, and complexity of cancer trials to be reduced, biomarker end points hold the promise to accelerate drug development and improve patient outcomes.

Monitoring cancer through the blood

Tumor biopsies remain the gold standard for the evaluation of genetic changes in tumors either at diagnosis or after treatment with targeted therapies. However, this is not always feasible and can seldom be performed more than once. Noninvasive techniques that measure the allelic burden in blood have the potential to realize genotype‐directed cancer therapy. These technologies can potentially be used for noninvasive tumor genotyping and also provide an opportunity for disease monitoring. Several non‐invasive genotyping technologies are currently under development and being evaluated in patients treated with targeted therapies.