Polyclonal on- and off-target resistance mutations in an EML4-ALK positive non-small cell lung cancer patient under ALK inhibition

Treatment of advanced stage anaplastic lymphoma kinase (ALK) positive non-small cell lung cancer (NSCLC) with ALK tyrosine kinase inhibitors (TKIs) has been shown to be superior to standard platinum-based chemotherapy. However, secondary progress of disease frequently occurs under ALK inhibitor treatment. The clinical impact of re-biopsies for treatment decisions beyond secondary progress is, however, still under debate. Here, we report on two novel subsequent polyclonal on- and off-target resistance mutations in a patient with ALK-fused NSCLC under ALK inhibitor treatment. A 63-year-old male patient with an advanced stage EML4-ALK fused pulmonary adenocarcinoma was initially successfully treated with the second-generation ALK inhibitor alectinib and upon progressions subsequently with brigatinib, lorlatinib and chemoimmunotherapy (CIT). Progress to alectinib was associated with a so far undescribed ALK mutation (p.A1200_G1201delinsW) which was, however, tractable by brigatinib. An off-target KRAS-mutation (p.Q61K) occurred in association with subsequent progression under second-line TKI treatment. Third-line lorlatinib showed limited efficacy but chemoimmunotherapy resulted in disappearance of the KRAS mutant clone and clinical tumor control for another eight months. In conclusion, we suggest molecular profiling of progressive tumor disease also for ALK-positive NSCLC to personalize treatment in a subgroup of ALK-positive patients.     

ALK Inhibitors: What Is the Best Way to Treat Patients With ALK+ Non–Small-Cell Lung Cancer?

Genetic insight into the pathogenesis of lung cancer has paved the way for a new era in its treatment. Recently, anaplastic lymphoma kinase (ALK) has been identified as exerting a potent transforming effect through genetic rearrangement in patients with lung cancer. Preclinical and single-arm phase I studies have shown that patients with ALK-rearranged non–small cell lung cancer (NSCLC) can be successfully treated with crizotinib. Furthermore, a phase III randomized study indicated that crizotinib is superior to standard chemotherapy in the treatment of patients with NSCLC harboring the ALK rearrangement who had received 1 previous platinum-based chemotherapy. Despite the excellent efficacy of crizotinib in patients with ALK-positive (ALK⁺) lung cancer, resistance mechanisms—such as secondary mutations in the ALK gene, the activation of other oncogenes, and so on—have been identified as conferring resistance to crizotinib. Second-generation ALK inhibitors, such as alectinib and ceritinib, have been shown to be effective not only in crizotinib-naive patients but also in those resistant to crizotinib. Therefore, although some agents specifically targeting ALK have been developed and their efficacy has been documented, how ALK inhibitors should be administered in the setting of ALK-rearranged NSCLC remains to be fully elucidated. Can second-generation ALK inhibitors replace crizotinib? Is crizotinib just a first-generation ALK inhibitor? Is the sequential use of crizotinib and second-generation ALK inhibitors the best method? In this article, we review the preclinical and clinical results regarding crizotinib and second-generation ALK inhibitors, as well as the resistance mechanisms, and discuss the best methods for treating patients with ALK⁺ NSCLC.     

Identification of a Novel HIP1-ALK Fusion Variant in Non–Small-Cell Lung Cancer (NSCLC) and Discovery of ALK I1171 (I1171N/S) Mutations in Two ALK-Rearranged NSCLC Patients with Resistance to Alectinib

Huntingtin-interacting protein 1 (HIP1) has recently been identified as a new fusion partner fused to anaplastic lymphoma kinase (ALK) in non–small-cell lung cancer (NSCLC). To date, two variants of HIP1-ALK (H21; A20) and (H28; A20) have been identified in NSCLC. However, the response of patients with NSCLC harboring HIP1-ALK to ALK inhibitors and potential resistance mechanisms to such remain unknown. Here, we report a patient with NSCLC harboring a novel HIP1-ALK fusion variant (H30; A20). This patient and another patient with EML4-ALK variant 3a/b initially responded sequentially to crizotinib and then alectinib, a next-generation ALK inhibitor, but developed acquired resistance to alectinib with the presence of a mutation in amino acid residue 1171 (I1171N and I1171S respectively) located in the hydrophobic regulatory spine (R-spine) of the ALK kinase in both the cases as identified by a comprehensive next-generation sequencing-based assay performed on biopsies of new liver metastases that developed during alectinib treatment.     

In vivo imaging models of bone and brain metastases and pleural carcinomatosis with a novel human EML4‐ALK lung cancer cell line

EML4‐ALK lung cancer accounts for approximately 3–7% of non‐small‐cell lung cancer cases. To investigate the molecular mechanism underlying tumor progression and targeted drug sensitivity/resistance in EML4‐ALK lung cancer, clinically relevant animal models are indispensable. In this study, we found that the lung adenocarcinoma cell line A925L expresses an EML4‐ALK gene fusion (variant 5a, E2:A20) and is sensitive to the ALK inhibitors crizotinib and alectinib. We further established highly tumorigenic A925LPE3 cells, which also have the EML4‐ALK gene fusion (variant 5a) and are sensitive to ALK inhibitors. By using A925LPE3 cells with luciferase gene transfection, we established in vivo imaging models for pleural carcinomatosis, bone metastasis, and brain metastasis, all of which are significant clinical concerns of advanced EML4‐ALK lung cancer. Interestingly, crizotinib caused tumors to shrink in the pleural carcinomatosis model, but not in bone and brain metastasis models, whereas alectinib showed remarkable efficacy in all three models, indicative of the clinical efficacy of these ALK inhibitors. Our in vivo imaging models of multiple organ sites may provide useful resources to analyze further the pathogenesis of EML4‐ALK lung cancer and its response and resistance to ALK inhibitors in various organ microenvironments.     

Overcoming the resistance to Crizotinib in patients with Non-Small Cell Lung Cancer harboring EML4/ALK translocation

The large knowledge learned in molecular biology specifically in the oncology field during the last ten years has resulted in fruitful results for the treatment of non-small cell lung cancer. The first pathway to be effectively targeted in lung cancer was the epidermal growth factor receptor. The acceptance of epidermal growth factor receptor mutation as a strong predictive biomarker in non-small cell lung carcinoma has encouraged the search for more targets. In 2011, regulatory entities granted conditional approval to an anaplastic lymphoma kinase inhibitor (crizotinib) based on an impressive overall response rate in previously treated non-small cell lung cancer patients whose tumors harbored EML4/ALK translocations. The landmark approval of crizotinib based on early promising clinical data highlights the remarkable success of molecular medicine in lung cancer therapeutics. The cumulative data developed after that approval has confirmed the appropriateness of this decision as recently reported phase III has now demonstrated. Unfortunately, resistance to this agent invariably develops and we now face the challenge of understanding several resistance pathways and overcoming them with new and more potent compounds. New agents in clinical development such as alectinib, LDK378, AP26113, and AUY922 have not only demonstrated promising activity in crizotinib resistant patients, but also crossing new pharmacokinetic boundaries in ALK inhibition as potent CNS penetration.     

Head to head evaluation of second generation ALK inhibitors brigatinib and alectinib as first-line treatment for ALK+ NSCLC using an in silico systems biology-based approach

Around 3–7% of patients with non-small cell lung cancer (NSCLC), which represent 85% of diagnosed lung cancers, have a rearrangement in the ALK gene that produces an abnormal activity of the ALK protein cell signaling pathway. The developed ALK tyrosine kinase inhibitors (TKIs), such as crizotinib, ceritinib, alectinib, brigatinib and lorlatinb present good performance treating ALK+ NSCLC, although all patients invariably develop resistance due to ALK secondary mutations or bypass mechanisms. In the present study, we compare the potential differences between brigatinib and alectinib’s mechanisms of action as first-line treatment for ALK+ NSCLC in a systems biology-based in silico setting.Therapeutic performance mapping system (TPMS) technology was used to characterize the mechanisms of action of brigatinib and alectinib and the impact of potential resistances and drug interferences with concomitant treatments.The analyses indicate that brigatinib and alectinib affect cell growth, apoptosis and immune evasion through ALK inhibition. However, brigatinib seems to achieve a more diverse downstream effect due to a broader cancer-related kinase target spectrum. Brigatinib also shows a robust effect over invasiveness and central nervous system metastasis-related mechanisms, whereas alectinib seems to have a greater impact on the immune evasion mechanism.Based on this in silico head to head study, we conclude that brigatinib shows a predicted efficacy similar to alectinib and could be a good candidate in a first-line setting against ALK+ NSCLC. Future investigation involving clinical studies will be needed to confirm these findings. These in silico systems biology-based models could be applied for exploring other unanswered questions.     

Receptor ligand-triggered resistance to alectinib and its circumvention by Hsp90 inhibition in EML4-ALK lung cancer cells

Alectinib is a new generation ALK inhibitor with activity against the gatekeeper L1196M mutation that showed remarkable activity in a phase I/II study with echinoderm microtubule associated protein-like 4 (EML4) - anaplastic lymphoma kinase (ALK) non-small cell lung cancer (NSCLC) patients. However, alectinib resistance may eventually develop. Here, we found that EGFR ligands and HGF, a ligand of the MET receptor, activate EGFR and MET, respectively, as alternative pathways, and thereby induce resistance to alectinib. Additionally, the heat shock protein 90 (Hsp90) inhibitor suppressed protein expression of ALK, MET, EGFR, and AKT, and thereby induced apoptosis in EML4-ALK NSCLC cells, even in the presence of EGFR ligands or HGF. These results suggest that Hsp90 inhibitors may overcome ligand-triggered resistance to new generation ALK inhibitors and may result in more successful treatment of NSCLC patients with EML4-ALK.     

Elucidation of Resistance Mechanisms to Second-Generation ALK Inhibitors Alectinib and Ceritinib in Non–Small Cell Lung Cancer Cells

Crizotinib is the first anaplastic lymphoma kinase (ALK) inhibitor to have been approved for the treatment of non–small cell lung cancer (NSCLC) harboring an ALK fusion gene, but it has been found that, in the clinic, patients develop resistance to it. Alectinib and ceritinib are second-generation ALK inhibitors which show remarkable clinical responses in both crizotinib-naive and crizotinib-resistant NSCLC patients harboring an ALK fusion gene. Despite their impressive activity, clinical resistance to alectinib and ceritinib has also emerged. In the current study, we elucidated the resistance mechanisms to these second-generation ALK inhibitors in the H3122 NSCLC cell line harboring the EML4-ALK variant 1 fusion in vitro. Prolonged treatment of the parental H3122 cells with alectinib and ceritinib led to two cell lines which are 10 times less sensitive to alectinib and ceritinib than the parental H3122 cell line. Although mutations of ALK in its kinase domain are a common resistance mechanism for crizotinib, we did not detect any ALK mutation in these resistant cell lines. Rather, overexpression of phospho-ALK and alternative receptor tyrosine kinases such as phospho-EGFR, phospho-HER3, and phospho-IGFR-1R was observed in both resistant cell lines. Additionally, NRG1, a ligand for HER3, is upregulated and responsible for resistance by activating the EGFR family pathways through the NRG1-HER3-EGFR axis. Combination treatment with EGFR inhibitors, in particular afatinib, was shown to be effective at overcoming resistance. Our study provides new mechanistic insights into adaptive resistance to second-generation ALK inhibitors and suggests a potential clinical strategy to combat resistance to these second-generation ALK inhibitors in NSCLC.     

Dual ALK and EGFR inhibition targets a mechanism of acquired resistance to the tyrosine kinase inhibitor crizotinib in ALK rearranged lung cancer

Introduction

The multitargeted tyrosine kinase inhibitor (TKI) crizotinib is active against ALK translocated non-small-cell lung cancer (NSCLC); however acquired resistance invariably develops over time. ALK mutations have previously been implicated in only a third of resistant tumors. We sought to evaluate alternative mechanisms of resistance and preclinical strategies to overcome these in a cell line driven by EML4-ALK.

Methods

We selected the NSCLC cell line NCI-H3122 (H3122: EML4-ALK E13;A20) and derived resistant variants that were able to grow in the presence of 1 μM crizotinib. These were analyzed for ALK mutations, sensitivity to crizotinib in combination with other TKIs, and for activation of alternative tyrosine kinases.

Results

All H3122 crizotinib resistant (CR) clones lacked amplification or mutations in the kinase domain of ALK. To evaluate if possible alternative kinases functioned as “bypass” tracks for downstream signaling activation in these resistance cells, we performed of phosho-receptor tyrosine kinase array that demonstrated that CR clones had higher phospho-EGFR signals than H3122 cells before and after exposure to crizotinib. A functional approach of dual ALK TKI (with crizotinib) with combinatory TKI inhibition was used as a secondary screen for possible targets. Crizotinib + erlotinib (reversible EGFR TKI) and crizotinib + afatinib (irreversible EGFR/ERBB2 TKI) were able to inhibit the growth of H3122 CR clones, confirming EGFR activation as a mechanism of resistance. The removal of crizotinib from the culture media re-sensitized CR cells to crizotinib.

Conclusions

We identified activation of EGFR as a mechanism of resistance to crizotinib in preclinical models of ALK translocated NSCLC. If EGFR activation is confirmed as a predominant mechanism of ALK TKI-induced resistance in patient-derived tumors, the use of ALK plus EGFR TKIs could be explored for this important cohort of NSCLCs.     

Antitumor activity of the selective ALK inhibitor alectinib in models of intracranial metastases

Purpose

The clinical efficacy of the anaplastic lymphoma kinase (ALK) inhibitor crizotinib has been demonstrated in ALK fusion-positive non-small cell lung cancer (NSCLC); however, brain metastases are frequent sites of initial failure in patients due to poor penetration of the central nervous system by crizotinib. Here, we examined the efficacy of a selective ALK inhibitor alectinib/CH5424802 in preclinical models of intracranial tumors.

Methods

We established intracranial tumor implantation mouse models of EML4–ALK-positive NSCLC NCI-H2228 and examined the antitumor activity of alectinib in this model. Plasma distribution and brain distribution of alectinib were examined by quantitative whole-body autoradiography administrating a single oral dose of ¹⁴C-labeled alectinib to rats. The drug permeability of alectinib was evaluated in Caco-2 cell.

Results

Alectinib resulted in regression of NCI-H2228 tumor in mouse brain and provided a survival benefit. In a pharmacokinetic study using rats, alectinib showed a high brain-to-plasma ratio, and in an in vitro drug permeability study using Caco-2 cells, alectinib was not transported by P-glycoprotein efflux transporter that is a key factor in blood–brain barrier penetration.

Conclusions

We established intracranial tumor implantation models of EML4–ALK-positive NSCLC. Alectinib showed potent efficacy against intracranial EML4–ALK-positive tumor. These results demonstrated that alectinib might provide therapeutic opportunities for crizotinib-treated patients with brain metastases.     

The accelerated path of ceritinib: Translating pre-clinical development into clinical efficacy

The discovery of anaplastic lymphoma kinase (ALK)-rearranged non–small-cell lung cancer (NSCLC) in 2007 led to the development and subsequent approval of the ALK inhibitor crizotinib in 2011. However, despite its clinical efficacy, resistance to crizotinib invariably develops. There is now a next generation of ALK inhibitors, including two that have been approved—ceritinib and alectinib—and others that are in development—brigatinib, lorlatinib and X-396. Ceritinib and the other next-generation ALK inhibitors are more potent than crizotinib and can overcome tumor cell resistance mechanisms. Ceritinib gained US Food and Drug Administration approval in 2014 following accelerated review for the treatment of patients with ALK-positive (ALK+) metastatic NSCLC who have progressed on or are intolerant to crizotinib. In pre-clinical studies, it demonstrated more potent inhibition of ALK than crizotinib in enzymatic assays, more durable responses in xenograft models and the ability to potently overcome crizotinib resistance mutations in vitro (including the gatekeeper mutation). There is also evidence for ceritinib penetration across the blood-brain barrier. In clinical trials, ceritinib has demonstrated durable responses and progression-free survival in ALK-inhibitor–pre-treated and –naïve NSCLC patients, including high overall and intracranial response rates in those with central nervous system metastases. Selective gastrointestinal toxicity of ceritinib, such as diarrhea, nausea and vomiting is generally manageable with prophylactic medication and prompt dose reduction or interruption. Future progress in treating ALK+ NSCLC will focus on determining the optimal sequencing of therapies and strategies to overcome acquired resistance, an ongoing challenge in treating ALK-mutation–driven tumors.     

Establishment of a Conditional Transgenic Mouse Model Recapitulating EML4-ALK–Positive Human Non–Small Cell Lung Cancer

BackgroundAnaplastic lymphoma receptor tyrosine kinase gene (ALK) fusion is a distinct molecular subclassification of NSCLC that is targeted by anaplastic lymphoma kinase (ALK) inhibitors. We established a transgenic mouse model that expresses tumors highly resembling human NSCLC harboring echinoderm microtubule associated protein like 4 gene (EML)-ALK fusion. We aimed to test an EML4-ALK transgenic mouse model as a platform for assessing the efficacy of ALK inhibitors and examining mechanisms of acquired resistance to ALK inhibitors.MethodsTransgenic mouse lines harboring LoxP-STOP-LoxP-FLAGS–tagged human EML4-ALK (variant 1) transgene was established by using C57BL/6N mice. The transgenic mouse model with highly lung-specific, inducible expression of echinoderm microtubule associated protein like 4–ALK fusion protein was established by crossing the EML4-ALK transgenic mice with mice expressing Cre–estrogen receptor fusion protein under the control of surfactant protein C gene (SPC). Expression of EML4-ALK transgene was induced by intraperitoneally injecting mice with tamoxifen. When the lung tumor of the mice treated with the ALK inhibitor crizotinib for 2 weeks was measured, tumor shrinkage was observed.ResultsEML4-ALK tumor developed after 1 week of tamoxifen treatment. Echinoderm microtubule associated protein like 4–ALK was strongly expressed in the lung but not in other organs. ALK and FLAGS expressions were observed by immunohistochemistry. Treatment of EML4-ALK tumor–bearing mice with crizotinib for 2 weeks induced dramatic shrinkage of tumors with no signs of toxicity. Furthermore, prolonged treatment with crizotinib led to acquired resistance in tumors, resulting in regrowth and disease progression. The resistant tumor nodules revealed acquired ALK G1202R mutations.ConclusionsAn EML4-ALK transgenic mouse model for study of drug resistance was successfully established with short duration of tumorigenesis. This model should be a strong preclinical model for testing efficacy of ALK TKIs, providing a useful tool for investigating the mechanisms of acquired resistance and pursuing novel treatment strategies in ALK-positive lung cancer.     

Amphiregulin triggered epidermal growth factor receptor activation confers in vivo crizotinib‐resistance of EML4‐ALK lung cancer and circumvention by epidermal growth factor receptor inhibitors

Crizotinib, a first‐generation anaplastic lymphoma kinase (ALK) tyrosine‐kinase inhibitor, is known to be effective against echinoderm microtubule‐associated protein‐like 4 (EML4)‐ALK‐positive non‐small cell lung cancers. Nonetheless, the tumors subsequently become resistant to crizotinib and recur in almost every case. The mechanism of the acquired resistance needs to be deciphered. In this study, we established crizotinib‐resistant cells (A925LPE3‐CR) via long‐term administration of crizotinib to a mouse model of pleural carcinomatous effusions; this model involved implantation of the A925LPE3 cell line, which harbors the EML4‐ALK gene rearrangement. The resistant cells did not have the secondary ALK mutations frequently occurring in crizotinib‐resistant cells, and these cells were cross‐resistant to alectinib and ceritinib as well. In cell clone #2, which is one of the clones of A925LPE3‐CR, crizotinib sensitivity was restored via the inhibition of epidermal growth factor receptor (EGFR) by means of an EGFR tyrosine‐kinase inhibitor (erlotinib) or an anti‐EGFR antibody (cetuximab) in vitro and in the murine xenograft model. Cell clone #2 did not have an EGFR mutation, but the expression of amphiregulin (AREG), one of EGFR ligands, was significantly increased. A knockdown of AREG with small interfering RNAs restored the sensitivity to crizotinib. These data suggest that overexpression of EGFR ligands such as AREG can cause resistance to crizotinib, and that inhibition of EGFR signaling may be a promising strategy to overcome crizotinib resistance in EML4‐ALK lung cancer.     

ALK inhibition for non-small cell lung cancer: from discovery to therapy in record time

It was only 3 years ago that an acquired translocation of EML4 with ALK leading to the expression of an EML4-ALK oncoprotein in non-small cell lung cancer (NSCLC) was reported. Tumor cells expressing EML4-ALK are "addicted" to its continued function. Now, crizotinib, an oral ALK inhibitor, is demonstrated to provide dramatic clinical benefit with little toxicity in patients having such advanced NSCLC, and a mechanism of clinical resistance to crizotinib is identified. Such therapy "targeted" at oncogenic proteins provides "personalized" medicine and prompts genome-wide mutation analysis of human tumors to find other therapeutic targets.     

NPM/ALK mutants resistant to ASP3026 display variable sensitivity to alternative ALK inhibitors but succumb to the novel compound PF-06463922

ALK is involved in the onset of several tumors. Crizotinib (Xalkori^TM), a potent ALK inhibitor, represents the current front-line treatment for ALK+ NSCLC and shows great clinical efficacy. However, resistant disease often develops after initial response. ASP3026 is a novel second-generation ALK inhibitor with activity on crizotinib-resistant ALK-L1196M gatekeeper mutant. As resistance is likely to be a relevant hurdle for any drug, we sought to determine the resistance profile of ASP3026 in the context of NPM/ALK+ ALCL. We selected six ASP3026-resistant cell lines by culturing human ALCL cells in the presence of increasing concentrations of drug. The established resistant cell lines carry several point mutations in the ALK kinase domain (G1128S, C1156F, I1171N/T, F1174I, N1178H, E1210K and C1156F/D1203N were the most frequent) that are shown to confer resistance to ASP3026 in the Ba/F3 cell model. All mutants were profiled for cross-resistance against a panel of clinically relevant inhibitors including ceritinib, alectinib, crizotinib, AP26113 and PF-06463922. Finally, a genetically heterogeneous ASP3026-resistant cell line was exposed to second-line treatment simulations with all inhibitors. The population evolved according to relative sensitivity of its mutant subclones to the various drugs. Compound PF-06463922 did not allow the outgrowth of any resistant clone, at non-toxic doses.     

ALK Mutation Status Before and After Alectinib Treatment in Locally Advanced or Metastatic ALK-Positive NSCLC: Pooled Analysis of Two Prospective Trials

IntroductionThe effectiveness of ALK receptor tyrosine kinase (ALK) inhibitors can be limited by the development of ALK resistance mutations. This exploratory analysis assessed the efficacy of alectinib in patients with NSCLC and ALK point mutations using pooled data from two single-arm phase II studies.MethodsStudies NP28673 and NP28761 enrolled adults with locally advanced/metastatic ALK-positive NSCLC who had progressed on crizotinib. ALK mutation analysis was conducted on cell-free DNA from 187 patients post-crizotinib/pre-alectinib, and from 49 of these patients who subsequently progressed on alectinib.ResultsBaseline characteristics were generally balanced across patient subgroups. At baseline, 34 distinct ALK mutations were identified in 48 of 187 patients (25.7%). Median investigator-assessed progression-free survival was longer in patients without ALK single-nucleotide variants (n = 138) versus those with (n = 48): 10.2 months (95% confidence interval [CI]: 8.1–14.3) versus 5.6 months (95% CI: 4.5–10.9), respectively. Sixteen of 32 patients (50%) with ALK resistance mutations to crizotinib achieved an investigator-assessed response to alectinib (all partial responses); most of these ALK mutations were known to be sensitive to alectinib. Analysis of plasma samples obtained post-progression on alectinib revealed that 26 of 49 (53%) samples harbored 16 distinct ALK mutations, with known alectinib-resistance mutations, I1171 T/N/S, G1202R, and V1180L, observed in 15 of 49 (31%) tumors.ConclusionsAlectinib appears clinically active against ALK rearrangements and mutations, as well as several ALK variants that can cause resistance to crizotinib. The use of cell-free DNA in plasma samples may be an alternative noninvasive method for monitoring resistance mutations during therapy.     

Brigatinib Versus Crizotinib in ALK Inhibitor–Naive Advanced ALK-Positive NSCLC: Final Results of Phase 3 ALTA-1L Trial

IntroductionIn the phase 3 study entitled ALK in Lung cancer Trial of brigAtinib in 1st Line (ALTA-1L), which is a study of brigatinib in ALK inhibitor–naive advanced ALK-positive NSCLC, brigatinib exhibited superior progression-free survival (PFS) versus crizotinib in the two planned interim analyses. Here, we report the final efficacy, safety, and exploratory results.MethodsPatients were randomized to brigatinib 180 mg once daily (7-d lead-in at 90 mg once daily) or crizotinib 250 mg twice daily. The primary end point was a blinded independent review committee–assessed PFS. Genetic alterations in plasma cell-free DNA were assessed in relation to clinical efficacy.ResultsA total of 275 patients were enrolled (brigatinib, n = 137; crizotinib, n = 138). At study end, (brigatinib median follow-up = 40.4 mo), the 3-year PFS by blinded independent review committee was 43% (brigatinib) versus 19% (crizotinib; median = 24.0 versus 11.1 mo, hazard ratio [HR] = 0.48, 95% confidence interval [CI]: 0.35–0.66). The median overall survival was not reached in either group (HR = 0.81, 95% CI: 0.53–1.22). Posthoc analyses suggested an overall survival benefit for brigatinib in patients with baseline brain metastases (HR = 0.43, 95% CI: 0.21–0.89). Detectable baseline EML4-ALK fusion variant 3 and TP53 mutation in plasma were associated with poor PFS. Brigatinib exhibited superior efficacy compared with crizotinib regardless of EML4-ALK variant and TP53 mutation. Emerging secondary ALK mutations were rare in patients progressing on brigatinib. No new safety signals were observed.ConclusionsIn the ALTA-1L final analysis, with longer follow-up, brigatinib continued to exhibit superior efficacy and tolerability versus crizotinib in patients with or without poor prognostic biomarkers. The suggested survival benefit with brigatinib in patients with brain metastases warrants future study.     

非小细胞肺癌中EML4-ALK融合基因的生物学特性及其治疗

在非小细胞肺癌(non-small cell lung cancer,NSCLC)中已发现棘皮动物微管相关蛋白样4(echinoderm microtubule-associated protein-like 4,EML4)和间变性淋巴瘤激酶(anaplastic lymphoma kinase,ALK)的融合基因.在不吸烟的NSCLC患者中大多可检测出EML4-ALK,其具有独特的病理学特征.EML4-ALK在体内外均有致癌性.ALK抑制剂(crizotinib)在EML4-ALK阳性的NSCLC患者中已取得较好的治疗效果.本综述重点阐述NSCLC中EML4-ALK的生物学特性、临床特征和治疗.     

Anaplastic lymphoma kinase as a new target for the treatment of non-small-cell lung cancer

The anaplastic lymphoma kinase (ALK) gene rearrangement identifies a distinct molecular subset in non-small-cell lung cancer (NSCLC) populations susceptible to targeted inhibition. It consists of a small inversion in the short arm of chromosome 2 between exon 20 of the ALK gene and different exons of the echinoderm microtubule-associated protein-like (EML4) gene. This translocation leads to a chimeric protein with constitutive activation of ALK that possesses an oncogenic activity demonstrated both in vitro and in vivo. Other rare translocation partners for ALK other than EML4 may be found in lung cancers, including TRK-fused gene (TFG) and kinesin family member 5B (KIF5B). ALK-positive patients represent 5–6% of all NSCLCs and they seem to have particular clinicopathological and molecular features. Recently, Phase I–II trial results of crizotinib, a potent dual c-MET and ALK inhibitor, demonstrated its dramatic efficacy in ALK-positive patients with advanced NSCLC. This article will present knowledge on the characteristics of ALK-positive patients, discuss the different methods of ALK rearrangement detection and focus on clinical results of crizotinib.