Identification of Existing Drugs That Effectively Target NTRK1 and ROS1 Rearrangements in Lung Cancer

Current treatment and novel insights regarding ROS1-targeted therapy in malignant tumors

BACKGROUND

The proto-oncogene ROS1 encodes an intrinsic type I membrane protein of the tyrosine kinase/insulin receptor family. ROS1 facilitates the progression of various malignancies via self-mutations or rearrangements. Studies on ROS1-directed tyrosine kinase inhibitors have been conducted, and some have been approved by the FDA for clinical use. However, the adverse effects and mechanisms of resistance associated with ROS1 inhibitors remain unknown. In addition, next-generation ROS1 inhibitors, which have the advantage of treating central nervous system metastases and alleviating endogenous drug resistance, are still in the clinical trial stage.

METHOD

In this study, we searched relevant articles reporting the mechanism and clinical application of ROS1 in recent years; systematically reviewed the biological mechanisms, diagnostic methods, and research progress on ROS1 inhibitors; and provided perspectives for the future of ROS1-targeted therapy.

RESULTS

ROS1 is most expressed in malignant tumours. Only a few ROS1 kinase inhibitors are currently approved for use in NSCLC, the efficacy of other TKIs for NSCLC and other malignancies has not been ascertained. There is no effective standard treatment for adverse events or resistance to ROS1-targeted therapy. Next-generation TKIs appear capable of overcoming resistance and delaying central nervous system metastasis, but with a greater incidence of adverse effects.

CONCLUSIONS

Further research on next-generation TKIs regarding the localization of ROS1 and its fusion partners, binding sites for targeted drugs, and coadministration with other drugs is required. The correlation between TKIs and chemotherapy or immunotherapy in clinical practice requires further study.

Comprehensive Review of ROS1 Tyrosine Kinase Inhibitors-Classified by Structural Designs and Mutation Spectrum (Solvent Front Mutation [G2032R] and Central β-Sheet 6 [Cβ6] Mutation [L2086F])

Despite ROS1 fusion-positive NSCLC accounting for approximately 1% to 2% of NSCLC, there is a long list of ROS1 tyrosine kinase inhibitors (TKIs) being developed in addition to three approved ROS1 TKIs, crizotinib, entrectinib and repotrectinib. Here, we categorized ROS1 TKIs by their structures (cyclic versus noncyclic) and inhibitory abilities (active against solvent front mutation G2032R or central β-sheet #6 [Cβ6] mutation L2086F) and summarized their reported clinical activity in order to provide a dashboard on how to use these ROS1 TKIs in various clinical situations. In addition, the less known Cβ6 mutation ROS1 L2086F confer resistances to next-generation ROS1 TKIs (repotrectinib, taletrectinib, and potentially NVL-520) that can be overcome by cabozantinib as documented in published patient reports and potentially by certain L-shaped type I ROS1 TKIs including ceritinib and gilteritinib, which is approved as a FLT3 inhibitor for relapsed refractory FLT3+ acute myeloid leukemia but have published preclinical activites against ROS1 (and ALK). Future clinical trials should investigate cabozantinib and gilteritinib to repurpose them as ROS1 TKIs that can target ROS1 L2086F Cβ6 mutation.

Activity of ceritinib in crizotinib-resistant ROS1-rearranged non-small-cell lung cancer patients

As a second-generation selective oral anaplastic lymphoma kinase inhibitor, ceritinib is an effective first-line treatment for c-ros oncogene 1 (ROS1)-rearranged non-small-cell lung cancer (NSCLC). Its efficacy and safety for the treatment of crizotinib-resistant ROS1-rearranged NSCLC were explored in the study. A retrospective single-center study was conducted to investigate the efficacy of ceritinib in crizotinib-resistant ROS1-rearranged NSCLC. The objective response rate was the primary objective, while the disease control rate, progression-free survival and adverse events were secondary objectives. From December 2015 to October 2021, a total of 246 patients with ROS1-rearranged NSCLC were screened, 12 (4.9%) of whom were treated with ceritinib after the development of crizotinib resistance. Among the 12 crizotinib-resistant patients included, 3 displayed the efficacy of partial response and 3 had the efficacy of stable condition. The objective response rate, disease control rate and median progression-free survival of all patients were 25% (95% confidence interval [CI]: -3.7% to 53.7%; 3 of 12 patients), 50% (95% CI: 16.8% to 83.2%; 6 of 12 patients), and 10.5 months (95% CI, 5.7 to 15.3 months), respectively. In addition, of the 6 patients with brain metastases, an intracranial disease control rate of 66.7% (95% CI:12.5% to 120.9%) was obtained. The research results reveal that ceritinib can be a treatment option for ROS1-rearranged NSCLC patients after the development of crizotinib resistance.

Therapeutical Options in ROS1-Rearranged Advanced Non Small Cell Lung Cancer

ROS proto-oncogene 1 (ROS1) rearrangements occur in 0.9-2.6% of patients with non small cell lung cancer (NSCLC), conferring sensitivity to treatment with specific tyrosine-kinase inhibitors (TKI). Crizotinib, a first-generation TKI, was the first target-therapy approved for the first-line treatment of ROS1-positive NSCLC. Recently, entrectinib, a multitarget inhibitor with an anti-ROS1 activity 40 times more potent than crizotinib and better activity on the central nervous system (CNS), received approval for treatment-naive patients. After a median time-to-progression of 5.5-20 months, resistance mechanisms can occur, leading to tumor progression. Therefore, newer generation TKI with greater potency and brain penetration have been developed and are currently under investigation. This review summarizes the current knowledge on clinicopathological characteristics of ROS1-positive NSCLC and its therapeutic options.

Pre-clinical modelling of ROS1+ non-small cell lung cancer

Non-small cell lung cancer (NSCLC) is a heterogeneous group of diseases which accounts for 80% of newly diagnosed lung cancers. In the previous decade, a new molecular subset of NSCLC patients (around 2%) harboring rearrangements of the c-ros oncogene 1 was defined. ROS1+ NSCLC is typically diagnosed in young, nonsmoker individuals presenting an adenocarcinoma histology. Patients can benefit from tyrosine kinase inhibitors (TKIs) such as crizotinib and entrectinib, compounds initially approved to treat ALK-, MET- or NTRK- rearranged malignancies respectively. Given the low prevalence of ROS1-rearranged tumors, the use of TKIs was authorized based on pre-clinical evidence using limited experimental models, followed by basket clinical trials. After initiating targeted therapy, disease relapse is reported in approximately 50% of cases as a result of the appearance of resistance mechanisms. The restricted availability of TKIs active against resistance events critically reduces the overall survival. In this review we discuss the pre-clinical ROS1+ NSCLC models developed up to date, highlighting their strengths and limitations with respect to the unmet clinical needs. By combining gene-editing tools and novel cell culture approaches, newly developed pre-clinical models will enhance the development of next-generation tyrosine kinase inhibitors that overcome resistant tumor cell subpopulations.

From multi-omics data to the cancer druggable gene discovery: a novel machine learning-based approach

The development of targeted drugs allows precision medicine in cancer treatment and optimal targeted therapies. Accurate identification of cancer druggable genes helps strengthen the understanding of targeted cancer therapy and promotes precise cancer treatment. However, rare cancer-druggable genes have been found due to the multi-omics data's diversity and complexity. This study proposes deep forest for cancer druggable genes discovery (DF-CAGE), a novel machine learning-based method for cancer-druggable gene discovery. DF-CAGE integrated the somatic mutations, copy number variants, DNA methylation and RNA-Seq data across ˜10 000 TCGA profiles to identify the landscape of the cancer-druggable genes. We found that DF-CAGE discovers the commonalities of currently known cancer-druggable genes from the perspective of multi-omics data and achieved excellent performance on OncoKB, Target and Drugbank data sets. Among the ˜20 000 protein-coding genes, DF-CAGE pinpointed 465 potential cancer-druggable genes. We found that the candidate cancer druggable genes (CDG) are clinically meaningful and divided the CDG into known, reliable and potential gene sets. Finally, we analyzed the omics data's contribution to identifying druggable genes. We found that DF-CAGE reports druggable genes mainly based on the copy number variations (CNVs) data, the gene rearrangements and the mutation rates in the population. These findings may enlighten the future study and development of new drugs.

Molecular pathways, resistance mechanisms and targeted interventions in non-small-cell lung cancer

Lung cancer is the leading cause of cancer-related mortality worldwide. The discovery of tyrosine kinase inhibitors effectively targeting EGFR mutations in lung cancer patients in 2004 represented the beginning of the precision medicine era for this refractory disease. This great progress benefits from the identification of driver gene mutations, and after that, conventional and new technologies such as NGS further illustrated part of the complex molecular pathways of NSCLC. More targetable driver gene mutation identification in NSCLC patients greatly promoted the development of targeted therapy and provided great help for patient outcomes including significantly improved survival time and quality of life. Herein, we review the literature and ongoing clinical trials of NSCLC targeted therapy to address the molecular pathways and targeted intervention progress in NSCLC. In addition, the mutations in EGFR gene, ALK rearrangements, and KRAS mutations in the main sections, and the less common molecular alterations in MET, HER2, BRAF, ROS1, RET, and NTRK are discussed. The main resistance mechanisms of each targeted oncogene are highlighted to demonstrate the current dilemma of targeted therapy in NSCLC. Moreover, we discuss potential therapies to overcome the challenges of drug resistance. In this review, we manage to display the current landscape of targetable therapeutic patterns in NSCLC in this era of precision medicine.

Understanding gilteritinib resistance to FLT3-F691L mutation through an integrated computational strategy

FMS-like tyrosine kinase 3 (FLT3) serves as an important drug target for acute myeloid leukemia (AML), and gene mutations of FLT3 have been closely associated with AML patients with an incidence rate of ~ 30%. However, the mechanism of the clinically relevant F691L gatekeeper mutation conferred resistance to the drug gilteritinib remained poorly understood. In this study, multiple microsecond molecular dynamics (MD) simulations, end-point free energy calculations, and dynamic correlated and network analyses were performed to investigate the molecular basis of gilteritinib resistance to the FLT3-F691L mutation. The simulations revealed that the resistant mutation largely induced the conformational changes of the activation loop (A-loop), the phosphate-binding loop, and the helix αC of the FLT3 protein. The binding abilities of the gilteritinib to the wild-type and the F691L mutant were different through the binding free energy prediction. The simulation results further indicated that the driving force to determine the binding affinity of gilteritinib was derived from the differences in the energy terms of electrostatic and van der Waals interactions. Moreover, the per-residue free energy decomposition suggested that the four residues (Phe803, Gly831, Leu832, and Ala833) located at the A-loop of FLT3 had a significant impact on the binding affinity of gilteritinib to the F691L mutant. This study may provide useful information for the design of novel FLT3 inhibitors specially targeting the F691L gatekeeper mutant.

The potential and limitation of targeted chromosomal breakpoint sequencing for the ROS1 fusion gene identification in lung cancer

ROS1 fusion genes are rare but important driver genes in lung cancer. Owing to their rarity, many clinicopathological features and treatment responses for each ROS1 fusion variant are still largely unknown and require further investigation. RNA is the preferable template for the ROS1 fusion gene screening, but deterioration of RNA in FFPE often makes the detection challenging. To resolve the difficulty, a targeted chromosomal breakpoint sequencing method was developed for searching the ROS1 fusion gene, and was compared with fluorescence in situ hybridization, immunohistochemistry, RT-qPCR using 260 lung cancer samples of Southern Taiwan. The results showed that ROS1-altered cases were present at low frequencies, did not share distinct clinicopathological features, and often carried other driver mutations. The performance of the targeted sequencing assay was superior to the RT-qPCR in ROS1 fusion gene identification when the cDNAs were from FFPE samples, but long-read DNA sequencing and fresh-frozen samples would be better to revolve all fusion genes. Precise determination of all ROS1 fusion variants and concomitant driver mutations using both genomic DNA and RNA would be required to help improve the treatment of patients with ROS1 alterations.

An updated patent review of small-molecule ROS1 kinase inhibitors (2015-2021)

INTRODUCTION

: C-ros oncogene 1 (ROS1) is the sole member of the ROS1 receptor tyrosine kinase (ROS1-RTK) family, which is involved in the formation of non-small cell lung cancer (NSCLC), gastric adenocarcinoma, colorectal cancer and other malignant tumors. At present, only crizotinib was approved for the treatment of advanced ROS1-positive NSCLC, and there have been reports of ROS1 mutations resulting in drug resistance. Consequently, it is necessary to develop new generations of inhibitors to overcome the existing problems.

AREAS COVERED

This review summarizes the inhibitors with ROS1 inhibitory activity which are undergoing clinical trials and recent advances in patented ROS1 small molecular inhibitors from 2015 to 2021.

EXPERT OPINION

ROS1 rearrangements have been found in approximately 1%-2% of patients with NSCLC. Since the approval of crizotinib as multi-targeted ALK/MET/ROS1 kinase inhibitor for ALK-mutated NSCLC therapy, the researchers are focusing on ROS1-mutated tumors, especially NSCLC. However, drug-resistant mutations have already been found in clinical application. Therefore, it is still urgent to develop new generation of ROS1 inhibitors.

Bilateral optic disc edema as a possible complication of cabozantinib use-a case report

INTRODUCTION

Cabozantinib, which was approved by the Food and Drug Administration (FDA) in 2012, is a tyrosine kinase inhibitor widely used in the treatment of metastatic renal cell carcinoma (RCC) and medullary thyroid carcinoma. To date, no ocular adverse events have been reported by the FDA or on the package label. Here, we described a patient with metastatic RCC who developed bilateral optic disc edema after a 4-month course of cabozantinib.

CASE DESCRIPTION

A 55-year-old ethnic Chinese male with RCC with multiple metastases presented to our department with progressive blurred vision in both eyes for 1 month. He started taking cabozantinib 60 mg once daily 5 months prior to this presentation. Poor visual acuity and bilateral disc edema were then noted. Cabozantinib was discontinued after that, and 3-day pulse steroid therapy with methylprednisolone 1 g/day was given. The optic disc edema subsided gradually with limited improvement in visual acuity.

CONCLUSION

Bilateral optic edema should be considered as a complication associated with cabozantinib. We propose discontinuation of the treatment in cases such as that, and pulse steroid therapy should be considered if there is no contraindication.

Utility of the Ba/F3 cell system for exploring on-target mechanisms of resistance to targeted therapies for lung cancer

Molecular targeted therapies are the standard of care for front‐line treatment of metastatic non‐small‐cell lung cancers (NSCLCs) harboring driver gene mutations. However, despite the initial dramatic responses, the emergence of acquired resistance is inevitable. Acquisition of secondary mutations in the target gene (on‐target resistance) is one of the major mechanisms of resistance. The mouse pro‐B cell line Ba/F3 is dependent on interleukin‐3 for survival and proliferation. Upon transduction of a driver gene, Ba/F3 cells become independent of interleukin‐3 but dependent on the transduced driver gene. Therefore, the Ba/F3 cell line has been a popular system to generate models with oncogene dependence and vulnerability to specific targeted therapies. These models have been used to estimate oncogenicity of driver mutations or efficacies of molecularly targeted drugs. In addition, Ba/F3 models, together with N‐ethyl‐N‐nitrosourea mutagenesis, have been used to derive acquired resistant cells to investigate on‐target resistance mechanisms. Here, we reviewed studies that used Ba/F3 models with EGFR mutations, ALK/ROS1/NTRK/RET fusions, MET exon 14 skipping mutations, or KRAS G12C mutations to investigate secondary/tertiary drug resistant mutations. We determined that 68% of resistance mutations reproducibly detected in clinical cases were also found in Ba/F3 models. In addition, sensitivity data generated with Ba/F3 models correlated well with clinical responses to each drug. Ba/F3 models are useful to comprehensively identify potential mutations that induce resistance to molecularly targeted drugs and to explore drugs to overcome the resistance.

Research progress of omics technology in the field of tumor resistance: From singleomics to multiomics combination application

Drug resistance is the main obstacle in the treatment of many cancers. It is of great clinical significance to study the mechanism of drug resistance and find new targets. Multi-omics mainly includes genomics, epigenomics, transcriptomics, proteomics, metabolomics, and radiomics. In recent years, the research of tumor resistance has made rapid development, which has significantly accelerated the discovery of new targets.

Targeting Infrequent Driver Alterations in Non-Small Cell Lung Cancer

The discovery of oncogenic driver mutations led to the development of targeted therapies with non-small cell lung cancer (NSCLC) being a paradigm for precision medicine in this setting. Nowadays, the number of clinical trials focusing on targeted therapies for uncommon drivers is growing exponentially, emphasizing the medical need for these patients. Unfortunately, similar to what is observed with most targeted therapies directed against a driver oncogene, the clinical response is almost always temporary and acquired resistance to these drugs invariably emerges. Here, we review the biology of infrequent genomic actionable alterations in NSCLC as well as the current and emerging therapeutic options for these patients. Mechanisms leading to acquired drug resistance and future challenges in the field are also discussed.

Overcoming TKI resistance in fusion-driven NSCLC: new generation inhibitors and rationale for combination strategies

During the last several years, multiple gene rearrangements with oncogenic potential have been described in NSCLC, identifying specific clinic-pathological subgroups of patients that benefit from a targeted therapeutic approach, including anaplastic lymphoma kinase (ALK), c-ros protooncogene 1 (ROS1) and, more recently, REarranged during Transfection (RET) and neurotrophic tyrosine receptor kinases (NTRK) genes. Despite initial impressive antitumor activity, the use of targeted therapies in oncogene-addicted NSCLC subgroups is invariably associated with the development of acquired resistance through multiple mechanisms that can include both on-target and off-target mechanisms. However, the process of acquired resistance is a rapidly evolving clinical scenario that constantly evolves under the selective pressure of tyrosine kinase inhibitors. The development of increasingly higher selective and potent inhibitors, traditionally used to overcome resistance to first generation inhibitors, is associated with the development of novel mechanisms of resistance that encompass complex resistance mutations, highly recalcitrant to available TKIs, and bypass track mechanisms. Herein, we provide a comprehensive overview on the therapeutic strategies for overcoming acquired resistance to tyrosine kinase inhibitors (TKIs) targeting the most well-established oncogenic gene fusions in advanced NSCLC, including ALK, ROS1, RET, and NTRK rearrangements.

Clinical activity of brigatinib in ROS1-rearranged non-small cell lung cancer

BACKGROUND

Brigatinib is a potent ROS1 inhibitor. The existing data on its clinical activity in ROS1-rearranged non-small cell lung cancer (NSCLC) are limited to four cases.

METHODS

Six patients with ROS1-rearranged advanced NSCLC treated with brigatinib were identified through search of the internal databases of four participating cancer centers. Four additional patients were selected by PubMed and Google Scholar search. The objective response rate (ORR), progression-free survival (PFS) (RECIST v.1.1), duration of treatment (DOT), and safety were assessed.

RESULTS

Of eight patients evaluable for response assessment (crizotinib naive-1, crizotinib resistant -7), three patients demonstrated a partial response (ORR-37%). One crizotinib-naive patient had an ongoing response at 21.6 months. Of seven crizotinib-resistant patients, two patients demonstrated a partial response (ORR-29%), and one patient (14%) had stable disease. PFS, available in four crizotinib-resistant patients, was 7.6 + , 2.9, 2.0, and 0.4 months. In crizotinib-resistant patients, DOT was 9.7 + , 7.7 + , 7.6 + , 4.0, 2.0, 1.1, 0.4 months, and was not reported in two patients. Genomic profiling in one responder revealed no ROS1 alteration, suggesting that the response was attributable to "off-target" brigatinib activity. In two patients with progressive disease, genomic profiling demonstrated a cMET exon 14 mutation + KRAS G12A mutation in one case, and a persisting ROS1-CD74 fusion + TP53 K139N, FGFR2 E250G, ATM G2695D, and NF1 R2258Q mutations in the other. No grade 3-5 toxicity was observed.

CONCLUSION

Brigatinib demonstrated modest activity in crizotinib-resistant ROS1-rearranged NSCLC. Its intracranial and systemic activity should be assessed in correlation with the underlying molecular mechanism of crizotinib resistance.

The Road Less Traveled: A Guide to Metastatic ROS1-Rearranged Non-Small-Cell Lung Cancer

Over the past decade, significant advances have been achieved in the diagnostic testing, treatment, and prognosis of advanced non-small-cell lung cancer (NSCLC). One of the most significant developments was the identification of specific gene alterations that define subsets of NSCLC. In 2007, ROS1 rearrangements were first described and observed in approximately 1%-2% of patients with NSCLC. Currently, crizotinib remains the therapy of choice for advanced ROS1-rearranged NSCLC without CNS metastases, while entrectinib has emerged as the preferred option for those with CNS metastases. The next-generation inhibitors under development are more potent, have better CNS efficacy, and can overcome important resistance mutations. In this review, we focus on the management of patients with advanced NSCLC harboring a ROS1 rearrangement. We aim to provide insight into the diagnosis, treatment approach, and emerging treatments in this subgroup of NSCLC.

Later-Line Treatment with Lorlatinib in ALK- and ROS1-Rearrangement-Positive NSCLC: A Retrospective, Multicenter Analysis

In clinical practice, patients with anaplastic lymphoma kinase (ALK)-rearrangement–positive non–small-cell lung cancer commonly receive sequential treatment with ALK tyrosine kinase inhibitors. The third-generation agent lorlatinib has been shown to inhibit a wide range of ALK resistance mutations and thus offers potential benefit in later lines, although real-world data are lacking. This multicenter study retrospectively investigated later-line, real-world use of lorlatinib in patients with advanced ALK- or ROS1-positive lung cancer. Fifty-one patients registered in a compassionate use program in Austria, who received second- or later-line lorlatinib between January 2016 and May 2020, were included in this retrospective real-world data analysis. Median follow-up was 25.3 months. Median time of lorlatinib treatment was 4.4 months for ALK-positive and 12.2 months for ROS-positive patients. ALK-positive patients showed a response rate of 43.2%, while 85.7% percent of the ROS1-positive patients were considered responders. Median overall survival from lorlatinib initiation was 10.2 and 20.0 months for the ALK- and ROS1-positive groups, respectively. In the ALK-positive group, lorlatinib proved efficacy after both brigatinib and alectinib. Lorlatinib treatment was well tolerated. Later-line lorlatinib treatment can induce sustained responses in patients with advanced ALK- and ROS1-positive lung cancer.

Focus on ROS1-Positive Non-Small Cell Lung Cancer (NSCLC): Crizotinib, Resistance Mechanisms and the Newer Generation of Targeted Therapies

Simple Summary

Genetic rearrangements of the ROS1 gene account for up to 2% of NSCLC patients who sometimes develop brain metastasis, resulting in poor prognosis. This review discusses the tyrosine kinase inhibitor crizotinib plus updates and preliminary results with the newer generation of tyrosine kinase inhibitors, which have been specifically conceived to overcome crizotinib resistance, including brigatinib, cabozantinib, ceritinib, entrectinib, lorlatinib and repotrectinib. After introducing each agent’s properties, we provide suggestions on the best approaches to identify resistance mechanisms at an early stage, and we speculate on the most appropriate second-line therapies for patients who reported disease progression following crizotinib administration.

Abstract

The treatment of patients affected by non-small cell lung cancer (NSCLC) has been revolutionised by the discovery of druggable mutations. ROS1 (c-ros oncogene) is one gene with druggable mutations in NSCLC. ROS1 is currently targeted by several specific tyrosine kinase inhibitors (TKIs), but only two of these, crizotinib and entrectinib, have received Food and Drug Administration (FDA) approval. Crizotinib is a low molecular weight, orally available TKI that inhibits ROS1, MET and ALK and is considered the gold standard first-line treatment with demonstrated significant activity for lung cancers harbouring ROS1 gene rearrangements. However, crizotinib resistance often occurs, making the treatment of ROS1-positive lung cancers more challenging. A great effort has been undertaken to identify a new generation or ROS1 inhibitors. In this review, we briefly introduce the biology and role of ROS1 in lung cancer and discuss the underlying acquired mechanisms of resistance to crizotinib and the promising new agents able to overcome resistance mechanisms and offer alternative efficient therapies.

Treatment of ALK-rearranged non-small-cell lung cancer with brigatinib as second or later lines: real-world observations from a single institution

The second-generation ALK tyrosine kinase inhibitor brigatinib has recently been approved in the European Union for use after crizotinib treatment in patients with EML4-ALK-rearranged lung cancer. In the current study, brigatinib was investigated as second-line or later-line treatment in 35 patients who had developed resistance to crizotinib, ceritinib, or alectinib. Most patients (68.6%) received brigatinib as second or third line (range: second to 12th line). In the total cohort, complete and partial responses were obtained for 9.1 and 75.8%, respectively. Overall median progression-free survival was 9.9 months, whereas the largest treatment cohort (brigatinib after crizotinib failure) showed a median progression-free survival of 8.4 months. Fifty-four percent of patients with baseline brain metastases responded to brigatinib treatment. Brigatinib was highly effective after crizotinib and ceritinib failure. Six patients had received alectinib as monotherapy, second-line, or third line before brigatinib; of these, four experienced partial responses and two progressed responses. Brigatinib treatment was well tolerated.

ROS1-dependent cancers - biology, diagnostics and therapeutics

The proto-oncogene ROS1 encodes a receptor tyrosine kinase with an unknown physiological role in humans. Somatic chromosomal fusions involving ROS1 produce chimeric oncoproteins that drive a diverse range of cancers in adult and paediatric patients. ROS1-directed tyrosine kinase inhibitors (TKIs) are therapeutically active against these cancers, although only early-generation multikinase inhibitors have been granted regulatory approval, specifically for the treatment of ROS1 fusion-positive non-small-cell lung cancers; histology-agnostic approvals have yet to be granted. Intrinsic or extrinsic mechanisms of resistance to ROS1 TKIs can emerge in patients. Potential factors that influence resistance acquisition include the subcellular localization of the particular ROS1 oncoprotein and the TKI properties such as the preferential kinase conformation engaged and the spectrum of targets beyond ROS1. Importantly, the polyclonal nature of resistance remains underexplored. Higher-affinity next-generation ROS1 TKIs developed to have improved intracranial activity and to mitigate ROS1-intrinsic resistance mechanisms have demonstrated clinical efficacy in these regards, thus highlighting the utility of sequential ROS1 TKI therapy. Selective ROS1 inhibitors have yet to be developed, and thus the specific adverse effects of ROS1 inhibition cannot be deconvoluted from the toxicity profiles of the available multikinase inhibitors. Herein, we discuss the non-malignant and malignant biology of ROS1, the diagnostic challenges that ROS1 fusions present and the strategies to target ROS1 fusion proteins in both treatment-naive and acquired-resistance settings.

Entrectinib for the treatment of metastatic NSCLC: safety and efficacy

Introduction: Gene fusions are strong driver alterations in various cancers, increasingly diagnosed with multiple testing techniques. ROS1 fusions can be found in 1-2% of non-small cell lung cancer (NSCLC) and several tyrosine kinase inhibitors (TKIs) have been tested in this oncogene-driven disease. NTRK fusions are characteristic of a few rare types of cancer, also infrequently seen in some common cancers including NSCLC. Entrectinib is a newer ROS1 and NTRK inhibitor developed across different tumor types harboring rearrangements in these genes. Entrectinib was granted FDA accelerated approval in August 2019 for the treatment of ROS1+ NSCLC and NTRK-driven solid tumors.Areas covered: This review covers the mechanism of action, safety, and efficacy of entrectinib in patients with metastatic NSCLC.Expert opinion: Entrectinib is an orally bioavailable TKI of TrkA, TrkB, TrkC, and ROS1, with the ability to cross the blood-brain barrier. Entrectinib was effective and well-tolerated in patients harboring ROS1- or NTRK-rearranged NSCLC treated within phase I and II studies. Entrectinib appears to be the most appropriate treatment choice for TKIs-naïve patients, especially in those presenting brain metastasis. Conversely, in case of systemic progression with the evidence of acquired resistance mutations in ROS1 or Trk proteins, a sequential therapy with entrectinib could not be successful.

Effective Treatment with Cabozantinib in an Advanced Non-Small-Cell Lung Cancer Patient Harboring a CD74-ROS1 Fusion: A Case Report

Cabozantinib has been shown to have potent anti-ROS1 activity in many solid malignancies, particularly against those with solvent-front resistance mutations following crizotinib therapy. With regard to the most common CD74-ROS1 fusion, the efficacy of cabozantinib has only been demonstrated in vitro. Therefore, we evaluate the efficacy of cabozantinib in a patient with advanced non-small-cell lung cancer (NSCLC) harboring a CD74-ROS1 fusion in the present study. A 40-year-old female patient presented with 1-month history of cough, white sputum and chest pain. Chest CT scan revealed a consolidation in the middle lobe of the right lung together with multiple cavity lesions spreading in both lungs. Histopathological analysis of biopsy samples from the lesion in the middle lobe of the right lung suggested lung adenocarcinoma. After two lines of chemotherapy and EGFR-TKI therapy, a CD74-ROS1 rearrangement was detected and the patient was administered with cabozantinib for 1.5 years. Since cabozantinib resistance developed, crizotinib therapy was applied and demonstrated clinical effectiveness until now. Together, we report the first case of cabozantinib effectiveness in treating a CD74-ROS1-positive advanced NSCLC patient. Crizotinib remained as an effective therapeutic option following the acquisition of cabozantinib resistance.

Turning liabilities into opportunities: Off-target based drug repurposing in cancer

Targeted drugs and precision medicine have transformed the landscape of cancer therapy and significantly improved patient outcomes in many cases. However, as therapies are becoming more and more tailored to smaller patient populations and acquired resistance is limiting the duration of clinical responses, there is an ever increasing demand for new drugs, which is not easily met considering steadily rising drug attrition rates and development costs. Considering these challenges drug repurposing is an attractive complementary approach to traditional drug discovery that can satisfy some of these needs. This is facilitated by the fact that most targeted drugs, despite their implicit connotation, are not singularly specific, but rather display a wide spectrum of target selectivity. Importantly, some of the unintended drug "off-targets" are known anticancer targets in their own right. Others are becoming recognized as such in the process of elucidating off-target mechanisms that in fact are responsible for a drug's anticancer activity, thereby revealing potentially new cancer vulnerabilities. Harnessing such beneficial off-target effects can therefore lead to novel and promising precision medicine approaches. Here, we will discuss experimental and computational methods that are employed to specifically develop single target and network-based off-target repurposing strategies, for instance with drug combinations or polypharmacology drugs. By illustrating concrete examples that have led to clinical translation we will furthermore examine the various scientific and non-scientific factors that cumulatively determine the success of these efforts and thus can inform the future development of new and potentially lifesaving off-target based drug repurposing strategies for cancers that constitute important unmet medical needs.

TrkA overexpression in non-tumorigenic human breast cell lines confers oncogenic and metastatic properties

BACKGROUND/PURPOSE

TrkA overexpression occurs in over 20% of breast cancers, including triple-negative breast cancers (TNBC), and has recently been recognized as a potential driver of carcinogenesis. Recent clinical trials of pan-Trk inhibitors have demonstrated targeted activity against tumors harboring NTRK fusions, a relatively rare alteration across human cancers. Despite this success, current clinical trials have not investigated TrkA overexpression as an additional therapeutic target for pan-Trk inhibitors. Here, we evaluate the cancerous phenotypes of TrkA overexpression relative to NTRK1 fusions in human cells and assess response to pharmacologic Trk inhibition.

EXPERIMENTAL DESIGN/METHODS

To evaluate the clinical utility of TrkA overexpression, a panel of TrkA overexpressing cells were developed via stable transfection of an NTRK1 vector into the non-tumorigenic breast cell lines, MCF10A and hTERT-IMEC. A panel of positive controls was generated via stable transfection with a CD74-NTRK1 fusion vector into MCF10A cells. Cells were assessed via various in vitro and in vivo analyses to determine the transformative potential and targetability of TrkA overexpression.

RESULTS

TrkA overexpressing cells demonstrated transformative phenotypes similar to Trk fusions, indicating increased oncogenic potential. TrkA overexpressing cells demonstrated growth factor-independent proliferation, increased PI3Kinase and MAPKinase pathway activation, anchorage-independent growth, and increased migratory capacity. These phenotypes were abrogated by the addition of the pan-Trk inhibitor, larotrectinib. In vivo analysis demonstrated increased tumorgenicity and metastatic potential of TrkA overexpressing breast cancer cells.

CONCLUSIONS

Herein, we demonstrate TrkA overexpressing cells show increased tumorgenicity and are sensitive to pan-Trk inhibitors. These data suggest that TrkA overexpression may be an additional target for pan-Trk inhibitors and provide a targeted therapy for breast cancer patients.

Current progress and future perspectives of polypharmacology : From the view of non-small cell lung cancer

A pre-eminent subtype of lung carcinoma, Non-small cell lung cancer accounts for paramount causes of cancer-associated mortality worldwide. Undeterred by the endeavour in the treatment strategies, the overall cure and survival rates for NSCLC remain substandard, particularly in metastatic diseases. Moreover, the emergence of resistance to classic anticancer drugs further deteriorates the situation. These demanding circumstances culminate the need of extended and revamped research for the establishment of upcoming generation cancer therapeutics. Drug repositioning introduces an affordable and efficient strategy to discover novel drug action, especially when integrated with recent systems biology driven stratagem. This review illustrates the trendsetting approaches in repurposing along with their numerous success stories with an emphasize on the NSCLC therapeutics. Indeed, these novel hits, in combination with conventional anticancer agents, will ideally make their way the clinics and strengthen the therapeutic arsenal to combat drug resistance in the near future.

Design, synthesis and biological evaluations of 2-amino-4-(1-piperidine) pyridine derivatives as novel anti crizotinib-resistant ALK/ROS1 dual inhibitors

ALK and ROS1 kinases have become promising therapeutic targets since Crizotinib was used to treat non-small-cell lung cancer clinically. Aiming to explore new potent inhibitors, a series of 2-amino-4-(1-piperidine) pyridine derivatives that stabilized a novel DFG-shifted conformation in the kinase domain of ALK were designed and synthesized on the base of lead compound A. Biological evaluation highlighted that most of these new compounds could also potently inhibit ROS1 kinase, leading to the promising inhibitors against both ROS1 and ALK. Among them, the representative compound 2e stood out potent anti-proliferative activity against ALK-addicted H3122 and ROS1-addicted HCC78 cell lines (IC₅₀ = 6.27 μM and 10.71 μM, respectively), which were comparable to that of Crizotinib. Moreover, 2e showed impressive enzyme activity against clinically Crizotinib-resistant ALK^L1196M with an IC₅₀ value of 41.3 nM, which was about 2-fold more potent than that of Crizotinib. 2e also showed potent inhibitory activity in about 6-fold superior to Crizotinib (IC₅₀: 104.7 nM vs. 643.5 nM) in Ba/F3 cell line harboring ROS1^G2032R. Furthermore, molecular modeling disclosed that all the representative inhibitors could dock into the active site of ALK and ROS1, which gave a probable explanation of anti Crizotinib-resistant mutants. These results indicated that our work has established a path forward for the generation of anti Crizotinib-resistant ALK/ROS1 dual inhibitors.

ROS1-ADGRG6: a case report of a novel ROS1 oncogenic fusion variant in lung adenocarcinoma and the response to crizotinib

BACKGROUND

ROS1 rearrangements are validated drivers in lung cancer, which have been identified in a small subset (1-2%) of patients with non-small cell lung cancer (NSCLC). To date, 18 fusion genes of ROS1 have been identified in NSCLC. The ALK inhibitor (crizotinib) exhibits therapeutic effect against ROS1-rearranged NSCLC. Next-generation sequencing (NGS) technology represents a novel tool for ROS1 detection that covers many fusion genes.

CASE PRESENTATION

A 55-year-old female with EGFR mutation (L858R) was diagnosed with lung adenocarcinoma, who was responsive to first-generation EGFR-tyrosine kinase inhibitor (TKI). Afterwards, she developed acquired resistance accompanied with a ROS1 rearrangement. A NGS assay showed that the tumor had a novel ROS1-ADGRG6 rearrangement generated by the fusion of exons of 1-33 of ROS1 on chr6: q22.1 to exons of 2-26 of ADGRG6 on chr6: q24.2. The patient was obviously responsive to crizotinib.

CONCLUSION

We firstly identified ROS1-ADGRG6 fusion variant in NSCLC by NGS, which should be considered in further ROS1 detecting assays.

Entrectinib resistance mechanisms in ROS1-rearranged non-small cell lung cancer

Entrectinib is a pan-tyrosine-kinase inhibitor that targets oncogenic rearrangements in NTRK, ROS1 and ALK. The combined results of two clinical trials demonstrated the efficacy of entrectinib in ROS1-rearranged NSCLC. Because the development of drug resistance is inevitable, it would be helpful to determine the mechanisms of entrectinib resistance in a ROS1-rearranged tumor model so that future therapeutic strategies can be developed. Here, we characterized the molecular basis of resistance in entrectinib-resistant ROS1-rearranged HCC78 cells (HCC78ER cells). These cells were analyzed by next-generation sequencing and genetic profiling, which revealed the acquisition of KRAS G12C and the amplification of KRAS and FGF3. However, there were no secondary mutations in the ROS1 kinase domain. We also found that sustained ERK activation was involved in entrectinib resistance, and that combined treatment with selumetinib resensitized HCC78ER cells to entrectinib in cell viability and colony formation assays. Our data suggest that activation of the RAS signaling pathway can cause entrectinib resistance in ROS1-rearranged NSCLC, and is unlikely to be overcome by sequential single agent ROS1-targeting strategies against such tumors. Instead, co-targeting ROS1 and MEK may be an effective strategy for overcoming entrectinib resistance in ROS1-rearranged NSCLC.

Efficacy and Safety of Lorlatinib in Korean Non-Small-Cell Lung Cancer Patients With ALK or ROS1 Rearrangement Whose Disease Failed to Respond to a Previous Tyrosine Kinase Inhibitor

INTRODUCTION

Non-small-cell lung cancer (NSCLC) patients harboring ALK or ROS1 rearrangements invariably acquire resistance to the first- and second-generation tyrosine kinase inhibitors (TKIs), most notably ALK G1202R and ROS1 G2032R. Lorlatinib, a novel third-generation TKI, produced remarkable results from the first-in-man phase 1 trial: an overall response rate of 46% and 50% for previously treated ALK- and ROS1-positive patients, respectively. However, the efficacy of lorlatinib has not been widely validated in Asian patients.

PATIENTS AND METHODS

Patients with advanced NSCLC with ALK or ROS1 rearrangements who initiated lorlatinib therapy between November 2016 and July 2018 were retrospectively analyzed.

RESULTS

Twelve consecutive patients were included. The median age was 55 years (range, 36-76 years). Ten (83%) had ALK-positive NSCLC and 2 (17%) had ROS1-positive NSCLC. All patients had a history of first- or second-generation ALK TKI receipt. Two ALK-positive patients and one ROS1-positive patient had the G1202R and G2032R mutations, respectively. The overall response rate was 64% and the disease control rate was 91%. Of the 3 ALK-positive patients with intracranial target lesions, 1 (33%) had a complete response and 2 (67%) a partial response, producing an intracranial objective response of 100%. The median progression-free survival was 6.5 months (range, 1.0-16.5 months). The most common adverse event was hypercholesterolemia (83%), and no adverse event-related dose reductions or treatment discontinuations were reported.

CONCLUSION

This study is the first to report that lorlatinib is an important novel therapeutic option for Asian patients who have advanced NSCLC harboring ALK/ROS1 mutations whose disease progressed during treatment with first- and second-generation TKIs.

Analysis of NTRK Alterations in Pan-Cancer Adult and Pediatric Malignancies: Implications for NTRK-Targeted Therapeutics

Purpose

Fusions that involve neurotrophic-tropomyosin receptor kinase (NTRK) genes are known drivers of oncogenesis. Therapies that target these ultra-rare, constitutionally active NTRK fusions have been remarkably effective. Herein, we analyze the prevalence of the full array of NTRK alterations-fusions, mutations, copy number alterations, and increased transcript expression-in diverse adult and pediatric tumor types to understand the landscape of NTRK aberrations in cancer.

Methods

We assessed 13,467 samples available from The Cancer Genome Atlas (adult tumors) and the St Jude PeCan database (pediatric tumors) for the prevalence of NTRK fusions, as well as associated genomic and transcriptomic co-aberrations in different tumor types.

Results

NTRK fusions were observed in 0.31% of adult tumors and in 0.34% of pediatric tumors. The most common gene partners were NTRK3 (0.16% of adult tumors) followed by NTRK1 (0.14% of pediatric tumors). NTRK fusions were found more commonly in pediatric melanoma (11.1% of samples), pediatric glioma (3.97%), and adult thyroid cancers (2.34%). Additional genomic and transcriptomic NTRK alterations- mutation, amplification, and mRNA overexpression-occurred in 14.2% of samples, whereas the frequency of alterations that implicated NTRK ligands and the NTRK co-receptor (p75NTR) ranged from 3.8% to 5.4%. Among 31 adult samples carrying NTRK fusions, co-alterations occurred often and usually involved the downstream phosphoinositide-3-kinase signaling pathway, cell-cycle machinery, other tyrosine-kinase receptors, and mitogen-activated protein kinase signals.

Conclusion

Whereas NTRK fusions are exceedingly rare, other NTRK abnormalities affect 14% of patients with cancer. Affecting these alterations has not yet been achievable in cancer. Genomic co-alterations occur frequently with NTRK fusions, but it is not known if co-targeting them can attenuate primary or secondary resistance to NTRK inhibitors.

Oncogene addicted non-small-cell lung cancer: current standard and hot topics

Lung cancer is the leading cause of cancer mortality worldwide. Activating mutations in the EGFR and rearrangements in the anaplastic lymphoma kinase (ALK) or ROS proto-oncogene 1 receptor tyrosine kinase (ROS1) genes have been identified as oncogenic drivers in non-small-cell lung cancer. Development of specific small-molecule tyrosine kinase inhibitors, able to interfere with tumor growth and metastatic spread, dramatically changed the natural history of oncogene-addicted non-small-cell lung cancer. However, despite advances in targeted therapies, all patients inevitably develop acquired resistance to tyrosine kinase inhibitors. Novel promising and effective treatments are under investigations.

Targeting oncogenic drivers in lung cancer: Recent progress, current challenges and future opportunities

Targeted therapies have changed the landscape of treatments for non-small cell lung cancer (NSCLC). Specific targeted therapies have been approved for NSCLC patients harboring genetic alterations in four oncogenes, and agents targeting additional oncogenic drivers are under investigation. Standard first-line chemotherapy has been supplanted by these targeted therapies due to superior efficacy and lower toxicity. Despite excellent response rates and durable responses in some cases, most patients experience relapse within a few years due to the development of acquired drug resistance. Next generation targeted therapies are being developed to overcome drug resistance and extend the duration of therapy. In this review, we summarize the current treatment strategies for the major targetable oncogenic mutations/alterations in NSCLC and discuss the mechanisms leading to acquired drug resistance.

Personalized therapy for lung cancer: striking a moving target

Molecular targeted therapy heralded a new era for the treatment of patients with oncogene-driven advanced-stage non-small-cell lung cancer (NSCLC). Molecular testing at the time of diagnosis guides therapy selection, and targeted therapies in patients with activating mutations in EGFR, BRAF, and rearrangements in anaplastic lymphoma kinase (ALK) and ROS1 have become part of routine care. These therapies have extended the median survival from a mere few months to greater than 3 years for patients with stage 4 disease. However, despite the initial success, these treatments are eventually met with molecular resistance. Selective pressure leads to cellular adaption to maintain cancer growth, making resistance complex and the treatment challenging. This review focuses on recent advances in targeted therapy, mechanisms of resistance, and therapeutic strategies to overcome resistance in patients with lung cancer.

Lung cancer in never smokers-the East Asian experience

Approximately one third of all lung cancer patients in East Asia are never-smokers. Furthermore, the proportion of lung cancer in never smokers (LCINS) has been increasing over time. Never-smokers are more often diagnosed with adenocarcinoma in East Asia, a subtype largely defined by oncogenic drivers. In this subgroup of patients, as high as 90% of patients have been found to harbor well-known oncogenic mutations and can be successfully managed with targeted therapies inhibiting specific oncogenic mutant kinases. EGFR tyrosine kinase inhibitor (EGFR-TKI) treatment has been the most important targeted therapy in lung adenocarcinoma from East Asian never-smokers as approximately 70% of these patients have the opportunity to receive EGFR-TKI treatment. Lung squamous cell carcinoma (SQCC) and small cell lung cancer (SCLC) are two common histologic types of smoking-related non-small cell lung cancer (NSCLC). The proportion of never-smokers with SQCC and SCLC in East Asian patients seems to be higher than that in Caucasian patients. Recent studies also suggest that lung SQCC and SCLC in never-smokers may be distinct subtypes. Therefore, better understanding of the biologic characteristics of these subtypes of patients may provide new insights for the treatment. In this review, we will provide an overview of East Asian experience in the treatment of advanced, never-smoking lung cancer, focusing on etiologic factors in the development of LCINS, targeted therapy for never-smokers with adenocarcinoma, distinct characteristics of never-smokers with lung SQCC and SCLC, and the role of immunotherapy in never-smokers with NSCLC.

An Update on Predictive Biomarkers for Treatment Selection in Non-Small Cell Lung Cancer

It is now widely established that management of lung cancer is much more complex and cannot be centered on the binary classification of small-cell versus non-small cell lung cancer (NSCLC). Lung cancer is now recognized as a highly heterogeneous disease that develops from genetic mutations and gene expression patterns, which initiate uncontrolled cellular growth, proliferation and progression, as well as immune evasion. Accurate biomarker assessment to determine the mutational status of driver mutations such as EGFR, ALK and ROS1, which can be targeted by specific tyrosine kinase inhibitors, is now essential for treatment decision making in advanced stage NSCLC and has shifted the treatment paradigm of NSCLC to more individualized therapy. Rapid advancements in immunotherapeutic approaches to NSCLC treatment have been paralleled by development of a range of potential predictive biomarkers that can enrich for patient response, including PD-L1 expression and tumor mutational burden. Here, we review the key biomarkers that help predict response to treatment options in NSCLC patients.

Rapidly changing treatment algorithms for metastatic nonsquamous non-small-cell lung cancer

Background

The treatment paradigm for metastatic nonsquamous non-small-cell lung cancer (nsclc) continues to change. Algorithms published only 6 months ago are outdated today and are dramatically different from those published a few years ago. New driver mutations continue to be identified, and the development of therapies to inhibit oncogenic addiction is ongoing. Patient survival is improving as treatments become more personalized and effective.

Methods

This review looks at the outcomes of recent trials and discusses treatment options for patients with metastatic nsclc of nonsquamous histology. Algorithms continue to change quickly, and an attempt is made to keep the paradigm current and applicable into the near future.

Results

Treatment algorithms for nsclc tumours with EGFR mutations, ALK rearrangements, and ROS1 rearrangements, and for wild-type tumours are presented. A future algorithm based on new immunotherapy data is proposed.

Conclusions

The treatment algorithm for EGFR mutation is changing with the proven efficacy of osimertinib for the acquired T790M mutation. All patients taking first- or second-generation epidermal growth factor receptor tyrosine kinase inhibitors must be tested. The treatment algorithm for ALK rearrangement has changed with the proven superiority of alectinib compared with crizotinib in the first-line setting. The approval of crizotinib for ROS1 rearrangements now means that patients also must be tested for that mutation. The biomarker for checkpoint inhibitors continues to be PD-L1 by immunohistochemistry stain, but whether testing will be necessary for patient selection if chemotherapy combinations are implemented will be determined soon.

3D culture system containing gellan gum restores oncogene dependence in ROS1 rearrangements non-small cell lung cancer

The ROS1 fusion gene has been identified in approximately 1% of non-small cell lung cancer (NSCLC) cases. Several clinical studies have highlighted ROS1 as a promising therapeutic target because crizotinib, a multi-targeted drug against ROS1, ALK, and the MET proto-oncogene, has elicited remarkable responses in ROS1-rearrangements NSCLC. However, acquired resistance mediated by ROS1 kinase domain mutations has been identified and a system to assess ROS1 inhibitors for these resistant mutations is necessary for the promotion of drug development. Publicly available NSCLC cell lines harboring the ROS1 fusion gene are limited to only HCC78 cells carrying SLC34A2-ROS1. This cell line exhibits resistance to ROS1 inhibitors through activation of the EGFR pathway, although the cells were established from ROS1-TKI naïve pleural effusion. Here, we demonstrate that 3D culture with gellan gum can restore the ROS1 oncogene dependence of HCC78 cells by upregulating the expression of the ROS1 fusion gene and reducing the activity of the EGFR pathway. Moreover, we established the HCC78xe3 cell line, a subclone of the HCC78 cell line, by repeated in vitro cultures from tumor xenografts and created xenograft tumors three times using in vitro cultured cells. This eventually enabled us to engraft and stably grow the cells in vivo, and subsequently evaluate various ROS1 inhibitors against HCC78xe3 cells by overexpressing crizotinib-resistant mutations in the ROS1 kinase domain including G2032R and D2033 N. We newly found that lorlatinib, a next generation ROS1/ALK inhibitor, remain the activity against D2033 N mutation. Furthermore, we demonstrated that HCC78xe3 cells expressing SLC34A2-ROS1 G2032R, and D2033 N, but not wild type (WT) cells, were resistant to crizotinib in vivo. Taken together, our data suggested that 3D cultures of HCC78 might reflect the features in patients and this new system will be a useful tool for evaluating ROS1 inhibitors.

Beyond EGFR and ALK: targeting rare mutations in advanced non-small cell lung cancer

Lung cancer remains the leading cause of cancer-related death in men and women, despite its constantly declining rates in incidence and mortality in the developed world. The past decade has witnessed an unprecedented rise in the development of molecular targeted therapies in various types of tumors. In non-small cell lung cancer (NSCLC), the greatest paradigm shift is the implementation of EGFR and ALK tyrosine kinase inhibitors in the first line and subsequent lines of therapy, with impressive results. Though less frequent than the molecular alterations in the aforementioned genes, a number of aberrations in potential oncogenic drivers has been discovered, namely mutations in the genes KRAS, BRAF, HER2, PI3KCA and DDR2, ROS1 and RET rearrangements and MET, HER2 and FGFR1 gene amplifications. A great number of clinical trials are currently underway, evaluating agents specifically designed to target these alterations, with mixed results so far. The greatest cumulative benefit offered by these trials is that, despite their success or failure in their objective goals, they have provided us with a better understanding of the complexity of the molecular intracellular processes, necessitating thus the accurate interpretation of the preclinical data in order to appropriately select the patients that may derive benefit from targeted treatment strategies.