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.     

Overcoming crizotinib resistance in ALK-rearranged NSCLC with the second-generation ALK-inhibitor ceritinib

In up to 5% of non-small cell lung cancer (NSCLC) patients, the EML4-ALK translocation drives tumor progression. Treatment with the ALK inhibitor crizotinib is more effective than standard chemotherapy. However, resistance to crizotinib occurs after approximately 8 months. Ceritinib is the first second-generation ALK inhibitor approved for treatment of crizotinib-resistant NSCLC. Ceritinib inhibits two of the most common ALK-mutants that confer resistance to crizotinib: L1196 M and G1269A. Cells with ALK expression are more sensitive to ceritinib than crizotinib (IC₅₀ 25 nM vs. 150 nM, respectively). Alternative second-generation ALK inhibitors such as Alectinib, Brigatinib and PF-06463922 are currently in development, each affecting different crizotinib-resistant ALK target mutations. Genetic identification of crizotinib-resistant mutants is essential for selecting the optimal treatment strategy in NSCLC patients to overcome resistance and to increase progression-free survival.     

ASCEND-8: A Randomized Phase 1 Study of Ceritinib, 450 mg or 600 mg,Taken with a Low-Fat Meal versus 750 mg in Fasted State in Patients with Anaplastic Lymphoma Kinase (ALK)-Rearranged Metastatic Non–Small Cell Lung Cancer (NSCLC)

IntroductionCeritinib, 750 mg fasted, is approved for treatment of patients with ALK receptor tyrosine kinase gene (ALK)-rearranged (ALK-positive) NSCLC previously treated with crizotinib. Part 1 of the ASCEND-8 study determined whether administering ceritinib, 450 mg or 600 mg, with a low-fat meal may enhance gastrointestinal (GI) tolerability versus 750 mg fasted in patients with ALK-positive NSCLC while maintaining similar exposure.MethodsASCEND-8 is a multicenter, randomized, open-label, phase 1 study. Part 1 investigated the steady-state pharmacokinetics (PK) and safety of ceritinib, 450 mg or 600 mg, taken with a low-fat meal versus 750 mg fasted in patients with advanced ALK-positive NSCLC who were either treatment naive or pretreated with chemotherapy and/or crizotinib. Part 2 will assess efficacy and safety of ceritinib in treatment-naive patients.ResultsAs of June 16, 2016, 137 patients were randomized (450 mg fed [n = 44], 600 mg fed [n = 47], and 750 mg fasted [n = 46]); 135 patients received ceritinib. Median follow-up duration was 4.14 months. At steady state, relative to 750 mg fasted, 450 mg with food demonstrated comparable PK as assessed by maximum (peak) concentration of drug in plasma and area under the plasma concentration–time curve from time zero to 24 hours, whereas 600 mg with food demonstrated approximately 25% higher PK. Relative to 750 mg fasted, 450 mg with food was associated with a lower proportion of patients with GI toxicities, mostly grade 1 (diarrhea [43.2%], nausea [29.5%], and vomiting [18.2%]); there were no grade 3 or 4 events, study drug discontinuations, or serious AEs due to GI toxicities.ConclusionCeritinib, 450 mg with food, had similar exposure and a more favorable GI safety profile than ceritinib, 750 mg in fasted patients with ALK-positive NSCLC.     

Osimertinib Overcomes Alectinib Resistance Caused by Amphiregulin in a Leptomeningeal Carcinomatosis Model of ALK-Rearranged Lung Cancer

IntroductionLeptomeningeal carcinomatosis (LMC) occurs frequently in anaplastic lymphoma kinase (ALK)–rearranged NSCLC and develops acquired resistance to ALK tyrosine kinase inhibitors (ALK TKIs). This study aimed to clarify the resistance mechanism to alectinib, a second-generation ALK TKI, in LMC and test a novel therapeutic strategy.MethodsWe induced alectinib resistance in an LMC mouse model with ALK-rearranged NSCLC cell line, A925LPE3, by continuous oral alectinib treatment, established A925L/AR cells. Resistance mechanisms were analyzed using several assays, including Western blot and receptor tyrosine kinase array. We also measured amphiregulin (AREG) concentrations in cerebrospinal fluid from patients with ALK-rearranged NSCLC with alectinib-refractory LMC by enzyme-linked immunosorbent assay.ResultsA925L/AR cells were moderately resistant to various ALK TKIs, such as alectinib, crizotinib, ceritinib, and lorlatinib, compared with parental cells in vitro. A925L/AR cells acquired the resistance by EGFR activation resulting from AREG overexpression caused by decreased expression of microRNA-449a. EGFR TKIs and anti-EGFR antibody resensitized A925L/AR cells to alectinib in vitro. In the LMC model with A925L/AR cells, combined treatment with alectinib and EGFR TKIs, such as erlotinib and osimertinib, successfully controlled progression of LMC. Mass spectrometry imaging showed accumulation of the EGFR TKIs in the tumor lesions. Moreover, notably higher AREG levels were detected in cerebrospinal fluid of patients with alectinib-resistant ALK-rearranged NSCLC with LMC (n = 4), compared with patients with EGFR-mutated NSCLC with EGFR TKI–resistant LMC (n = 30), or patients without LMC (n = 24).ConclusionsThese findings indicate the potential of novel therapies targeting both ALK and EGFR for the treatment of ALK TKI–resistant LMC in ALK-rearranged NSCLC.     

Role of STK11 in ALK-positive non-small cell lung cancer

Anaplastic lymphoma kinase (ALK) inhibitors have been shown to be effective in treating patients with ALK-positive non-small cell lung cancer (NSCLC), and crizotinib, ceritinib and alectinib have been approved as clinical first-line therapeutic agents. The availability of these inhibitors has also largely changed the treatment strategy for advanced ALK-positive NSCLC. However, patients still inevitably develop resistance to ALK inhibitors, leading to tumor recurrence or metastasis. The most critical issues that need to be addressed in the current treatment of ALK-positive NSCLC include the high cost of targeted inhibitors and the potential for increased toxicity and resistance to combination therapy. Recently, it has been suggested that the serine/threonine kinase 11 (STK11) mutation may serve as one of the biomarkers for immunotherapy in NSCLC. Therefore, the main purpose of this review was to summarize the role of STK11 in ALK-positive NSCLC. The present review also summarizes the treatment and drug resistance studies in ALK-positive NSCLC and the current status of STK11 research in NSCLC.     

W‘ALK’ Into the Next Stage

In 2007, the rearrangement of anaplastic lymphoma kinase (ALK) was identified to be associated with the pathogenesis of a subset of patients with non–small-cell lung cancer (NSCLC). Surprisingly, approximately 4 years after the discovery of ALK rearrangement in lung cancer, the first-in-class ALK inhibitor (ALKi), crizotinib, was approved for metastatic ALK-rearranged NSCLC by the US Food and Drug Administration. Subsequently, next-generation ALKis, such as alectinib and ceritinib, have been developed, and some of them have been applied in the clinical setting. Furthermore, various resistance mechanisms against ALKis have been gradually elucidated, and treatment strategies according to such resistance have been proposed. In addition, novel ALKis exhibit good antitumor efficacy for brain metastases. Thus, we now know much about ALK-rearranged NSCLC; however, is it enough? Several concerns, such as the optimal sequence of ALKis, significance of antiangiogenic therapy, immune checkpoint therapy, and cytotoxic chemotherapy in ALK-rearranged NSCLC, should be clearly addressed, which would lead to the establishment of optimal treatment strategies and a more prolonged survival in patients with ALK rearrangement. Thus, we should w‘ALK’ into the next stage.     

The Current Landscape of Anaplastic Lymphoma Kinase (<Emphasis Type="Italic">ALK</Emphasis>) in Non-Small Cell Lung Cancer: Emerging Treatment Paradigms and Future Directions

Tumorigenic rearrangements in anaplastic lymphoma kinase (ALK) account for 3–7% of all non-small cell lung cancers (NSCLC). Treatment with targeted tyrosine kinase inhibitors (TKIs) has shown impressive clinical responses. Crizotinib was the first agent approved for front-line therapy of ALK-rearranged NSCLC after it demonstrated superiority to chemotherapy in response rate, duration of response, and progression-free survival. However, eventually all patients progress on crizotinib therapy, with the central nervous system (CNS) being the most common site, which served as the impetus for the development of more potent next-generation ALK inhibitors. Currently, ceritinib, alectinib, and brigatinib are all approved for second-line therapy after progression on or intolerance to crizotinib. Investigations into whether the initiation of a second-generation ALK inhibitor as first-line therapy is the superior treatment paradigm has resulted in the approval of ceritinib as initial therapy. Alectinib has also shown impressive results as front-line therapy, as recently reported in two large randomized studies that compared it to crizotinib. There is a significant need to better understand the drivers of and mechanisms underlying resistance to ALK inhibitors. While specific mutations have been identified, there is currently only limited evidence that the identification of specific mutations should impact selection of the next ALK inhibitor. The best treatment option for patients who become TKI refractory is also unclear, though there is some evidence to suggests that these patients are not responsive to checkpoint inhibitors and may respond better to chemotherapy. Combination therapy with other classes of agents may help to overcome resistance mechanisms and should be investigated further.

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Precision medicine against <Emphasis Type="Italic">ALK</Emphasis>-positive non-small cell lung cancer: beyond crizotinib

Anaplastic lymphoma kinase (ALK) rearrangements represent the molecular driver of a subset of non-small cell lung cancers (NSCLCs). Despite the initial response, virtually all ALK-positive patients develop an acquired resistance to the ALK inhibitor crizotinib, usually within 12 months. Several next-generation ALK inhibitors have been developed in order to overcome crizotinib limitation, providing an unprecedented survival for this subset of patients. The aim of this review to summarize the current knowledge on ALK tyrosine kinase inhibitors (TKIs) in the treatment of advanced ALK-positive NSCLC, focusing on the role of novel ALK inhibitors in this setting. In addition, we will discuss their role in the pharmacological management of ALK-positive brain metastasis. Next-generation ALK inhibitors showed an impressive clinical activity in ALK-positive NSCLC, also against the sanctuary site of CNS. Sequential therapy with ALK TKIs appears to be effective in patients who fail a first ALK TKI and translates in clinically meaningful benefit. However, these agents display different activity profiles against crizotinib resistance mutation; therefore re-genotyping the disease at progression in order to administer the right TKI to the right patient is going to be necessary to correctly tailor the treatment. To avoid repeated invasive procedure, noninvasive methods to detect and monitor ALK rearrangement are under clinical investigation.     

A Sensitive ALK Immunohistochemistry Companion Diagnostic Test Identifies Patients Eligible for Treatment with Crizotinib

IntroductionThe availability of high-quality, rigorously validated diagnostic tests that can be broadly implemented is necessary to efficiently identify patients with anaplastic lymphoma kinase (ALK)-positive NSCLC who can potentially benefit from treatment with crizotinib. Here we present data on the recently approved Ventana ALK (D5F3) CDx Assay (Ventana Medical Systems, Tucson, AZ), the only immunohistochemistry (IHC)-based assay linked to treatment outcome.MethodsNSCLC specimens prospectively tested for anaplastic lymphoma receptor tyrosine kinase gene (ALK) status by flourescent in situ hybridization (FISH) in the PROFILE 1014 clinical trial of crizotinib versus chemotherapy (N = 1018, including 179 ALK-positive and 754 ALK-negative specimens) were evaluated using the ALK (D5F3) CDx assay. Hazard ratios for progression-free survival comparing crizotinib and chemotherapy for ALK IHC–positive patients and ALK FISH–positive patients, as well as for concordance with the enrollment ALK FISH assay, were determined.ResultsResults from both assays were obtained for 933 cases. Percent positive, negative, and overall agreement rates were 86.0% , 96.3%, and 94.3%, respectively. There were 53 discrepant cases, of which 25 were ALK FISH–positive/ALK IHC–negative and 28 were ALK FISH–negative/ALK IHC–positive. The hazard ratios using observed outcomes were 0.401 for ALK FISH–positive/ALK IHC–positive cases and 0.407 for all ALK FISH–positive cases tested with ALK IHC versus 0.454 for all ALK FISH–positive cases enrolled in the trial. Outcome data for ALK FISH–negative/ALK IHC–positive cases were not available for analysis. Between-reader agreement rates for ALK IHC involving three independent laboratories exceeded 98%.ConclusionsThe ALK (D5F3) CDx assay is a stand-alone companion diagnostic test for identification of patients for treatment with crizotinib. This automated assay provides an effective option to accurately and rapidly identify patients with ALK-positive NSCLC. The simple binary scoring algorithm results in high reader-to-reader precision.     

Ceritinib: a Review in ALK-Positive Advanced NSCLC

Ceritinib (Zykadia?) is an oral, selective inhibitor of the anaplastic lymphoma kinase (ALK), a receptor tyrosine kinase which, after genetic rearrangement, acts as an oncogenic driver in a proportion of non-small cell lung cancers (NSCLCs). The drug is approved in several countries worldwide for the treatment of patients with ALK-positive, advanced NSCLC who have previously received the first-generation ALK inhibitor crizotinib (indication details may vary by country). Approval was based on its clinical benefit in this setting in the phase I and II trials known as ASCEND-1 and ?2. Across these noncomparative studies, 36–56 % of patients achieved a response with ceritinib (at the recommended dosage of 750 mg once daily) and the responses were durable, lasting up to a median of 10 months. Patients survived free from progression for a median of up to 7 months and had a median overall survival of up to 17 months. Moreover, efficacy outcomes in patients with brain metastases were generally consistent with those of the overall study populations. Ceritinib has an acceptable tolerability profile, with gastrointestinal issues, fatigue and liver test abnormalities being the most common adverse reactions. Thus, ceritinib is a valuable treatment option for patients with ALK-positive advanced NSCLC who have already received crizotinib therapy.     

Expanded Circulating Tumor Cells from a Patient with ALK-Positive Lung Cancer Present with EML4-ALK Rearrangement Along with Resistance Mutation and Enable Drug Sensitivity Testing: A Case Study

The emergence of liquid biopsy using circulating tumor cells (CTCs) as a resource to identify genomic alterations in cancer presents new opportunities for diagnosis, therapy, and surveillance. We identified EML4-ALK gene rearrangement in expanded CTCs from a patient with ALK-positive lung adenocarcinoma. At the time of radiographic progression, CTCs obtained from the patient revealed a drug resistance mutation (i.e., L1196M on the ALK gene). CTCs were expanded ex vivo and drug sensitivity testing was performed using two ALK inhibitors, crizotinib and ceritinib. The half maximal inhibitory concentration of ceritinib was 1664 nM compared with crizotinib (2268 nM), showing that ceritinib was a more potent ALK inhibitor. We show that it is feasible to detect serial genetic alterations in expanded CTCs and perform in vitro drug screening. These findings support the clinical utility of CTCs not only for diagnosis, but also a potential tool for drug sensitivity testing in distinct subsets of lung cancer and for personalized precision medicine.     

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.     

Sequential Use of Anaplastic Lymphoma Kinase Inhibitors in Japanese Patients With ALK-Rearranged Non–Small-Cell Lung Cancer: A Retrospective Analysis

Background

Second-generation anaplastic lymphoma kinase (ALK) inhibitors, such as alectinib and ceritinib, have recently been approved for treatment of ALK-rearranged non–small-cell lung cancer (NSCLC). An optimal strategy for using 2 or more ALK inhibitors has not been established. We sought to investigate the clinical impact of sequential use of ALK inhibitors on these tumors in clinical practice.

Selective ALK inhibitor alectinib with potent antitumor activity in models of crizotinib resistance

The clinical efficacy of the ALK inhibitor crizotinib has been demonstrated in ALK fusion-positive NSCLC; however, resistance to crizotinib certainly occurs through ALK secondary mutations in clinical use. Here we examined the efficacy of a selective ALK inhibitor alectinib/CH5424802 in models of crizotinib resistance. Alectinib led to tumor size reduction in EML4-ALK-positive xenograft tumors that failed to regress fully during the treatment with crizotinib. In addition, alectinib inhibited the growth of some EML4-ALK mutant-driven tumors, including the G1269A model. These results demonstrated that alectinib might provide therapeutic opportunities for crizotinib-treated patients with ALK secondary mutations.     

Chromoplectic TPM3–ALK rearrangement in a patient with inflammatory myofibroblastic tumor who responded to ceritinib after progression on crizotinib

BackgroundInflammatory myofibroblastic tumors (IMTs) are rare sarcomas that can occur at any age. Surgical resection is the primary treatment for patients with localized disease; however, these tumors frequently recur. Less commonly, patients with IMTs develop or present with metastatic disease. There is no standard of care for these patients and traditional cytotoxic therapy is largely ineffective. Most IMTs are associated with oncogenic ALK, ROS1 or PDGFRβ fusions and may benefit from targeted therapy.Patient and methodsWe sought to understand the genomic abnormalities of a patient who presented for management of metastatic IMT after progression of disease on crizotinib and a significant and durable partial response to the more potent ALK inhibitor ceritinib.ResultsThe residual IMT was resected based on the recommendations of a multidisciplinary tumor sarcoma tumor board and analyzed by whole-genome mate pair sequencing. Analysis of the residual, resected tumor identified a chromoplectic TPM3–ALK rearrangement that involved many other known oncogenes and was confirmed by rtPCR.ConclusionsIn our analysis of the treatment-resistant, residual IMT, we identified a complex pattern of genetic rearrangements consistent with chromoplexy. Although it is difficult to know for certain if these chromoplectic rearrangements preceded treatment, their presence suggests that chromoplexy has a role in the oncogenesis of IMTs. Furthermore, this patient's remarkable response suggests that ceritinib should be considered as an option after progression on crizotinib for patients with metastatic or unresectable IMT and ALK mutations.     

Crizotinib for the Treatment of ALK‐Rearranged Non‐Small Cell Lung Cancer: A Success Story to Usher in the Second Decade of Molecular Targeted Therapy in Oncology

Crizotinib, an ALK/MET/ROS1 inhibitor, was approved by the U.S. Food and Drug Administration for the treatment of anaplastic lymphoma kinase (ALK)‐rearranged non‐small cell lung cancer (NSCLC) in August 2011, merely 4 years after the first publication of ALK‐rearranged NSCLC. The crizotinib approval was accompanied by the simultaneous approval of an ALK companion diagnostic fluorescent in situ hybridization assay for the detection of ALK‐rearranged NSCLC. Crizotinib continued to be developed as an ALK and MET inhibitor in other tumor types driven by alteration in ALK and MET. Crizotinib has recently been shown to be an effective ROS1 inhibitor in ROS1‐rearranged NSCLC, with potential future clinical applications in ROS1‐rearranged tumors. Here we summarize the heterogeneity within the ALK‐ and ROS1‐rearranged molecular subtypes of NSCLC. We review the past and future clinical development of crizotinib for ALK‐rearranged NSCLC and the diagnostic assays to detect ALK‐rearranged NSCLC. We highlight how the success of crizotinib has changed the paradigm of future drug development for targeted therapies by targeting a molecular‐defined subtype of NSCLC despite its rarity and affected the practice of personalized medicine in oncology, emphasizing close collaboration between clinical oncologists, pathologists, and translational scientists.     

Targeting ALK: a promising strategy for the treatment of non-small cell lung cancer, non-Hodgkin’s lymphoma, and neuroblastoma

Anaplastic lymphoma kinase (ALK) is a tyrosine kinase receptor that affects a number of biological and biochemical functions through normal ligand-dependent signaling. It has oncogenic functions in a number of tumors including non-small cell lung cancer (NSCLC), anaplastic large cell lymphoma, and neuroblastoma when altered by translocation or amplification or mutation. On August 2011, a small molecule inhibitor against ALK, crizotinib, was approved for therapy against NSCLC with ALK translocations. As we determine the molecular heterogeneity of tumors, the potential of ALK as a relevant therapeutic target in a number of malignancies has become apparent. This review will discuss some of the tumor types with oncogenic ALK alterations. The activity and unique toxicities of crizotinib are described, along with potential mechanisms of resistance and new therapies beyond crizotinib.     

Sequential Therapy with Crizotinib and Alectinib in ALK-Rearranged Non–Small Cell Lung Cancer—A Multicenter Retrospective Study

IntroductionAlectinib and crizotinib have been approved for the therapy of NSCLC caused by anaplastic lymphoma kinase gene (ALK) rearrangement. The effect of alectinib or crizotinib on overall survival (OS) in patients with ALK-rearranged NSCLC remains unknown.MethodsA multicenter retrospective study was conducted to compare OS between patients receiving alectinib and crizotinib and between patients treated with alectinib and those treated sequentially with crizotinib and then alectinib after crizotinib failure. The time to treatment failure (TTF), progression-free survival (PFS), and OS were compared.ResultsSixty-one patients with ALK-rearranged NSCLC were enrolled. Forty-six patients were treated with anaplastic lymphoma kinase (ALK) inhibitors (31 with crizotinib, 28 with alectinib, and 13 with both ALK inhibitors). The response rate was 66.7% for the crizotinib-treated group and 80.8% for the alectinib-treated group. Among all patients, TTF and PFS were significantly prolonged in the alectinib-treated group compared with in the crizotinib-treated group. Subgroup analyses revealed significantly prolonged TTF for alectinib compared with crizotinib therapy in the ALK inhibitor–naive population. OS was significantly longer in the alectinib-treated group than in the crizotinib-treated group. The TTF and OS of patients treated sequentially with crizotinib and then with alectinib after crizotinib failure tended to be longer than those of patients treated with alectinib alone.ConclusionsTherapy with alectinib alone was significantly superior to therapy with crizotinib alone in terms of TTF, PFS, and OS, and sequential therapy with crizotinib and alectinib after crizotinib failure tended to provide a better OS benefit than did therapy with alectinib alone in patients with ALK-positive NSCLC. However, large-scale prospective studies are needed to confirm these observations.     

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.     

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.