9LBA Antitumor activity of ASP8273, an irreversible mutant selective EGFR-TKI, in NSCLC patients with tumors harboring EGFR activating mutations and T790M resistance mutation

The Resistance to EGFR-TKIs in Non-Small Cell Lung Cancer: From Molecular Mechanisms to Clinical Application of New Therapeutic Strategies

Almost 17% of Western patients affected by non-small cell lung cancer (NSCLC) have an activating epidermal growth factor receptor (EGFR) gene mutation. Del19 and L858R are the most-common ones; they are positive predictive factors for EGFR tyrosine kinase inhibitors (TKIs). Currently, osimertinib, a third-generation TKI, is the standard first-line therapy for advanced NSCLC patients with common EGFR mutations. This drug is also administered as a second-line treatment for those patients with the T790M EGFR mutation and previously treated with first- (erlotinib, gefitinib) or second- (afatinib) generation TKIs. However, despite the high clinical efficacy, the prognosis remains severe due to intrinsic or acquired resistance to EGRF-TKIs. Various mechanisms of resistance have been reported including the activation of other signalling pathways, the development of secondary mutations, the alteration of the downstream pathways, and phenotypic transformation. However, further data are needed to achieve the goal of overcoming resistance to EGFR-TKIs, hence the necessity of discovering novel genetic targets and developing new-generation drugs. This review aimed to deepen the knowledge of intrinsic and acquired molecular mechanisms of resistance to EGFR-TKIs and the development of new therapeutic strategies to overcome TKIs' resistance.

Osimertinib in patients with advanced epidermal growth factor receptor T790M mutation-positive non-small cell lung cancer: rationale, evidence and place in therapy

The identification of epidermal growth factor receptor (EGFR) mutations represented a fundamental step forward in the treatment of advanced non-small cell lung cancer (NSCLC) as they define a subset of patients who benefit from the administration of specifically designed targeted therapies. The inhibition of mutant EGFR through EGFR-tyrosine kinase inhibitors (TKIs), either reversible, first-generation gefitinib and erlotinib, or irreversible, second-generation afatinib, has dramatically improved the prognosis of patients harboring this specific genetic alteration, leading to unexpected clinical benefit. Unfortunately, virtually all patients who initially respond to treatment develop acquired resistance to EGFR-TKIs within 9-14 months. The EGFR T790M secondary mutation has emerged as a cause of treatment failure in approximately 60% of resistant cases. To date, several compounds designed with the aim to overcome T790M-mediated resistance are under clinical investigation. The aim of this review is to discuss emerging data regarding the third-generation EGFR-TKI, osimertinib, for the treatment of EGFR T790M mutant advanced NSCLC.

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.

Generations of Epidermal Growth Factor Receptor Tyrosine Kinase Inhibitors: Perils and Progress

OPINION STATEMENT

Epidermal growth factor receptor (EGFR) mutations have been detected in approximately 10 % of North American patients diagnosed with non-small cell lung cancer (NSCLC). Approximately 90 % of these mutations are exon 19 deletions or exon 21 L858R point mutations. First- and second-generation EGFR tyrosine kinase inhibitors (TKIs) are approved as first-line therapy based on clinical trials demonstrating superior response rates, progression free survival (PFS), and overall survival (OS) compared to chemotherapy in patients with EGFR mutation-positive NSCLC treated with an EGFR TKI prior to chemotherapy. However, the majority of patients treated with an EGFR TKI develop resistance to therapy within about 12 months, approximately 50 % of patients due to a second site mutation, the T790M mutation occurring within exon 20. At the time of progression, the EGFR TKI is most commonly discontinued and a different systemic therapy is initiated. However, oncogene addiction persists and recent exciting data with third-generation EGFR TKIs suggests that acquired resistance may be surmountable. The newest EGFR TKIs have shown activity against EGFR-mutant NSCLC after progression on first-generation TKIs, including those with T90M, while sparing wild-type EGFR and hence appear to be both well tolerated and efficacious. At this time, it appears that third-generation EGFR TKIs are effective following first-generation therapy, and determining the most appropriate sequence to maximize overall survival is a matter of ongoing investigation. As the arsenal of active agents in EGFR mutant NSCLC grows, future research into potential combinations, optimal timing, and resistance mechanisms of these new treatments, as well as their possible role in the adjuvant, post-chemoradiation, and neoadjuvant settings holds great promise for this group of patients.

Mechanisms of resistance to EGFR-targeted drugs: lung cancer

Despite the improvement in clinical outcomes derived by the introduction of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (EGFR-TKIs) in the treatment of patients with advanced non-small cell lung cancer (NSCLC) whose tumours harbour EGFR-activating mutations, prognosis remains unfavourable because of the occurrence of either intrinsic or acquired resistance. We reviewed the published literature and abstracts of oral and poster presentations from international conferences addressing EGFR-TKIs resistance mechanisms discovered in preclinical models and in patients with NSCLC. The molecular heterogeneity of lung cancer has several implications in terms of possible mechanisms of either intrinsic or acquired resistance to EGFR-targeted inhibitors. Several mechanisms of resistance have been described to EGFR-TKIs, such as the occurrence of secondary mutation (T790M, C797S), the activation of alternative signalling (Met, HGF, AXL, Hh, IGF-1R), the aberrance of the downstream pathways (AKT mutations, loss of PTEN), the impairment of the EGFR-TKIs-mediated apoptosis pathway (BCL2-like 11/BIM deletion polymorphism) and histological transformation. Although some of the mechanisms of resistance have been identified, much additional information is needed to understand and overcome resistance to EGFR-TKI agents. The majority of resistance mechanisms described are the result of a selection of pre-existing clones; thus, studies on the mechanisms by which subclonal alterations have an impact on tumour biology and influence cancer progression are extremely important in order to define the best treatment strategy.

Treatment approaches for EGFR-inhibitor-resistant patients with non-small-cell lung cancer

Discovery of activating mutations in EGFR and their use as predictive biomarkers to tailor patient therapy with EGFR tyrosine kinase inhibitors (TKIs) has revolutionised treatment of patients with advanced EGFR-mutant non-small-cell lung cancer (NSCLC). At present, first-line treatment with EGFR TKIs (gefitinib, erlotinib, and afatinib) has been approved for patients harbouring exon 19 deletions or exon 21 (Leu858Arg) substitution EGFR mutations. These agents improve response rates, time to progression, and overall survival. Unfortunately, patients develop resistance, limiting patient benefit and posing a challenge to oncologists. Optimum treatment after progression is not clearly defined. A more detailed understanding of the biology of EGFR-mutant NSCLC and the mechanisms of resistance to targeted therapy mean that an era of treatment approaches based on rationally developed drugs or therapeutic strategies has begun. Combination approaches-eg, dual EGFR blockade-to overcome resistance have been trialled and seem to be promising but are potentially limited by toxicity. Third-generation EGFR-mutant-selective TKIs, such as AZD9291 or rociletininb, which target Thr790Met-mutant tumours, the most common mechanism of EGFR TKI resistance, have entered clinical trials, and exciting, albeit preliminary, efficacy data have been reported. In this Review, we summarise the scientific literature and evidence on therapy options after EGFR TKI treatment for patients with NSCLC, aiming to provide a guide to oncologists, and consider how to maximise therapeutic advances in outcomes in this rapidly advancing area.