Acquired Crizotinib Resistance Research Articles

Activation of IGF-1R pathway and NPM-ALK G1269A mutation confer resistance to crizotinib treatment in NPM-ALK positive lymphoma.

ALK-positive anaplastic large cell lymphoma (ALCL) represents a subset of non-Hodgkin's lymphoma that is treated with crizotinib, a dual ALK/MET inhibitor. Despite the remarkable initial response, ALCLs eventually develop resistance to crizotinib. ALK inhibitor resistance in tumors is a complex and heterogeneous process with multiple underlying mechanisms, including ALK gene amplification, ALK kinase domain mutation, and the activation of various bypass signaling pathways. To overcome resistance, multiple promising next-generation ALK kinase inhibitors and rational combinatorial strategies are being developed. To determine how cancers acquire resistance to ALK inhibitors, we established a model of acquired crizotinib resistance by exposing a highly sensitive NPM-ALK-positive ALCL cell line to increasing doses of crizotinib until resistance emerged. We found that the NPM-ALK mutation was selected under intermediate-concentration drug stress in resistant clones, accompanied by activation of the IGF-1R pathway. In the crizotinib-resistant ALCL cell model, the IGF-1R pathway was activated, and combined ALK/IGF-1R inhibition improved therapeutic efficacy. Furthermore, we also detected the NPM-ALK G1269A mutation, which had previously been demonstrated to result in decreased affinity for crizotinib, in the resistant cell model. Although crizotinib was ineffective against cells harboring the NPM-ALK G1269A mutation, five structurally different ALK inhibitors, alectinib, ceritinib, TAE684, ASP3026 and AP26113, maintained activity against the resistant cells. Thus, we have shown that second-generation ALK tyrosine kinase inhibitors or IGF-1R inhibitors are effective in treating crizotinib-resistant tumors.

Primary resistance to crizotinib treatment in a non-small cell lung cancer patient with an EML4-ALK rearrangement: a case report.

Crizotinib, a small molecular tyrosine kinase inhibitor, manifests dramatic responses in patients with non-small cell lung cancer with echinoderm microtubule associated protein like 4-anaplastic lymphoma kinase (EML4-ALK) rearrangements. ALK gene point mutation is the primary mechanism of acquired crizotinib resistance; however, the intrinsic mechanism is not fully understood. Here, we report a patient with a low mutant allele fraction (MAF) of EML4-ALK rearrangement, who experienced primary resistance to crizotinib treatment. The patient was a 66-year-old Chinese man, who had a history of metastatic lung cancer and was treated with first- and third-generation epidermal growth factor receptor tyrosine kinase inhibitors (EGFR TKIs). After 14 months of osimertinib treatment, his disease progressed, and next-generation sequencing was performed from a liquid biopsy of the patient’s blood. An EML4-ALK rearrangement was found and crizotinib was administered. The patient’s lung lesions continued to progress after one month of crizotinib treatment, and pemetrexed-bevacizumab was initiated. After two cycles of chemotherapy, the metastatic cancers shrunk, and the patient maintained stable disease at his last follow-up. EML4-ALK rearrangements can happen in patients with EGFR-positive NSCLC, after acquired resistance to EGFR TKI treatment. The EGFR T790M and C797G mutations occur in cis is a critical mechanism of resistance to osimertinib therapy. The MAF of EML4-ALK rearrangements in cancer cells might be a predictive factor for crizotinib treatment.

SC11.03 ROS1 as a Therapeutic Target in Advanced NSCLC

SC11.03 ROS1 as a Therapeutic Target in Advanced NSCLC

ED01.03 Insights from TCGA

ED01.03 Insights from TCGA

Abstract 1889: AXL and EGFR signaling mediate resistance to Crizotinib in non-small cell lung cancer cells harboring the ROS1 fusion gene

Abstract Background: The multi-tyrosine kinase inhibitor (TKI) crizotinib elicits a dramatic response in patients with non-small cell lung cancer (NSCLC) harboring the c-ros oncogene 1 (ROS1) fusion gene (Shaw et al. NEJM 2014); however, these patients inevitably develop resistance to crizotinib within a year, which limits the efficacy of crizotinib. Although reported molecular changes include ROS1 tyrosine kinase mutations, epidermal growth factor receptor (EGFR) activation, and epithelial-to mesenchymal transition, the detailed mechanism of crizotinib resistance has not been elucidated. Methods: To explore the molecular mechanisms of acquired crizotinib resistance in detail, we used a cell line model. HCC78 cells harboring the SLC34A2-ROS1 fusion gene, which are sensitive to crizotinib, were exposed continuously to increasing concentrations of crizotinib in a step-wise manner. A crizotinib-resistant cell line designated HCC78R was established and assessed by MTT assay, Western blotting, a receptor tyrosine kinase (RTK) array, quantitative PCR (RT-PCR), ELISA, and an RNA kinome targeted kinome panel (612 genes) with next-generation sequencing. Results: Crizotinib-resistant HCC78R (50% inhibitory concentration [IC50] 4085.9 nmol/L) was 47-fold more resistant to crizotinib than was parental HCC78 (IC50 85.8 nmol/L) (p = 0.0145) according to MTT assay. The RTK array revealed that EGFR phosphorylation was upregulated in HCC78R cells. Western blotting confirmed the activation of EGFR and its downstream signaling pathways. RT-PCR screening of EGFR ligand family member expression showed increased heparin-binding EGF-like growth factor (HB-EGF) in HCC78R compared with HCC78 cells. Consistently, addition of the HB-EGF or conditioned medium from HCC78R cells rendered the HCC78 parental cells moderately resistant to crizotinib. EGFR overexpression or activating mutations were not detected. Furthermore, RNA kinome sequencing revealed 16-fold higher AXL mRNA expression and 1.68-fold lower ROS1 fusion gene expression in HCC78R compared with HCC78. Overexpression of the AXL protein and downregulation of the ROS1 protein were confirmed by Western blotting. Monotherapy with gefitinib (EGFR-TKI) or R428 (AXL inhibitor) or cabozantinib (AXL inhibitor) moderately inhibited the growth of HCC78R cells, while combined therapy suppressed proliferation more significantly compared with each monotherapy. Conclusions: AXL and EGFR signaling mediate resistance to crizotinib, and combination treatment of an EGFR-TKI and AXL inhibitor may be an alternative strategy in ROS1 fusion gene-driven lung cancer cells. Citation Format: Yuka Kato, Kadoaki Ohashi, Eiki Ichihara, Shuuta Tomida, Hiroe Kayatani, Kenichiro Kudo, Daisuke Minami, Takashi Ninomiya, Toshio Kubo, Toshiyuki Kozuki, Katsuyuki Hotta, Nagio Takigawa, Mitsune Tanimoto, Katsuyuki Kiura. AXL and EGFR signaling mediate resistance to Crizotinib in non-small cell lung cancer cells harboring the ROS1 fusion gene. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1889.

Abstract C82: Induction of resistances to crizotinib in lung patient derived xenograft

Abstract Background. Anaplastic lymphoma kinase (ALK) is a receptor tyrosine kinase, and its mutation, over-expression and gene fusion have been associated with various cancers. EML4-ALK fusion has been confirmed to be an oncogenic driver for a small subset of the lung cancers (∼4% of NSCLC)1, and becomes an excellent drug target that led to the development of the first effective therapy, crizotinib, a tyrosine kinase inhibitor for anaplastic lymphoma kinase, for this disease 2,3. However, like any other cancer therapy so far, the treatment always led to the development of resistance, rendering them ineffective in the end4. Understanding the mechanisms causing these resistances can potentially facilitate overcoming the resistance and extend patients' life5,6. However, lack of experimental model hinders this understanding. Method. We have recently established a large collection of patient derived xenografts (∼350 PDXs)7, and we screened some of them for alk gene fusions. We then tested the positive model for sensitivity to crizothinib, and keep it under several rounds of crizotinib treatments to select resistant model. The induced resistant model was subjected to genomic analysis to identify the changes that might potentially be responsible for the resistance. Results. We identified one model, NSCLC LU1656, containing EML4-ALK fusion with elevated ALK expression. It has also been shown to respond well to crizotinib in vivo. The continued treatment eventually led to the development of resistance to crizotinib (LU2445), a situation that might occur in patients in the clinic under the same treatment. We have performed transcriptome sequencing of the parental sensitive tumor (LU1656) and the selected resistant tumor (LU2445). So far, we found both models expressed similar high levels of expression of ALK, but no additional mutations in ALK gene. There are other alterations either genetically or epigenetically, some seemingly related to the ALK signaling pathways. However, their role in resistance still need to be confirmed. Conclusions. Induced crizotinib resistance in ALK-fusion lung PDX can be useful to investigate crizotinib resistant mechanism and future drugs overcoming the resistance.

Highlights of This Issue

TCR-gene T-cell therapy has been studied in refractory melanoma and sarcoma patients, and the regimens usually include lymphodepleting preconditioning. Kageyama and colleagues treated 10 MAGE-A4+ recurrent esophageal cancer patients with wild-type TCR-gene transduced T-cell transfer. They show that the transferred T cells persisted long, trafficked to tumor sites, and maintained tumor-specific reactivity and that 3 of 10 patients who had minimal disease long-remained free from disease progression. All the patients did not encounter any serious toxicity. Wild-type TCRs with physiologically high avidity may represent a safe approach in clinical use.The development of novel anticancer agents is central to improving cancer treatment. Lolkema and colleagues present a study exploring a novel selective C-Met inhibitor and report unexpected renal toxicity in humans. Extensive preclinical analysis showed that species-specific metabolism of quinoline ring structures causes the renal toxicity. This integrated clinical and preclinical analysis elucidated the mechanism of toxicity allowing future quinoline ring structure containing drugs to be tested for species specific metabolism.Cell-penetrating peptides represent a promising class of anticancer drugs; however, these agents have had limited applicability because of poor pharmacologic and intracellular delivery properties. Hasegawa and colleagues report that these challenges can be circumvented when targeting the widely overexpressed MUC1-C oncoprotein by encapsulating the GO-203 inhibitor peptide in novel biodegradable PLA-PEG-PPG-PEG tetrablock nanoparticles (NPs). They show that these NPs are highly effective for inhibiting MUC1-C by the sustained intracellular delivery of GO-203 in diverse carcinoma cells growing in vitro and in vivo. This NP-based approach may be functional for the targeting of other intracellular oncoproteins with peptide drugs.Crizotinib showed marked antitumor activity against ROS1-rearranged NSCLC. Despite the efficacy of crizotinib, development of resistance is inevitable. Song and colleagues discerned the mechanisms of crizotinib resistance in ROS1-rearranged NSCLC using samples from two patients and crizotinib-resistant cell lines. ROS1 kinase mutations (G2032R and L2155S), EGFR activation, and epithelial-to-mesenchymal transition were associated with acquired crizotinib resistance. Secondary ROS1-mutant NSCLC cells were sensitive to foretinib. In addition, EGFR/ROS1-activated NSCLC cells were inhibited by irreversible EGFR inhibitors. These might define subsequent treatment strategies in patients with ROS1-rearraged NSCLC who showed acquired resistance to crizotinib.

Molecular Changes Associated with Acquired Resistance to Crizotinib in ROS1-Rearranged Non-Small Cell Lung Cancer.

Although ROS1-rearranged non-small cell lung cancer (NSCLC) is sensitive to crizotinib, development of resistance is inevitable. Here, we identified molecular alterations in crizotinib-resistant tumors from two NSCLC patients with the CD74-ROS1 rearrangement, and in HCC78 cells harboring SLC34A2-ROS1 that showed resistance to crizotinib (HCC78CR cells). ROS1 kinase domain mutations were examined in fresh tumor tissues from two NSCLC patients and HCC78CR1-3 cells by direct sequencing. Ba/F3 cells expressing ROS1 secondary mutations were constructed to evaluate resistance to crizotinib. An upregulated pathway was identified using phospho-receptor tyrosine kinase array, EGFR signaling antibody array, and RNA sequencing (RNA-seq). Cell proliferation and ROS1 downstream signaling pathways were compared between HCC78 and HCC78CR1-3 cells. The ROS1 G2032R mutation was identified in crizotinib-resistant tumors from one patient. Furthermore, HCC78CR1 and CR2 cells harbored a novel ROS1 L2155S mutation (73.3% and 76.2%, respectively). ROS1 G2032R and L2155S mutations conferred resistance to crizotinib in Ba/F3 cells. Evidence of epithelial-to-mesenchymal transition with downregulated E-cadherin and upregulated vimentin was observed in HCC78CR1-2 cells and in the other patient. RNA-seq and EGFR signaling antibody array revealed that the EGFR pathway was significantly upregulated in HCC78CR3 versus HCC78 cells. Cells with the ROS1 mutation and upregulated EGFR were sensitive to foretinib, an inhibitor of c-MET, VEGFR2, and ROS1 and irreversible EGFR tyrosine kinase inhibitors plus crizotinib, respectively. Molecular changes associated with acquired crizotinib resistance in ROS1-rearranged NSCLC are heterogeneous, including ROS1 tyrosine kinase mutations, EGFR activation, and epithelial-to-mesenchymal transition.

Primary signet-ring cell carcinoma of the lung treated with crizotinib: A case report.

Primary signet-ring cell adenocarcinoma (SRCA) of the lung is an extremely rare subtype of lung adenocarcinoma with a poor prognosis. The presence of an SRC component is considered to be a prominent clinicopathological characteristic of EML4-ALK-positive non-small cell lung cancer (NSCLC). Crizotinib, an anaplastic lymphoma kinase inhibitor, has been approved for the treatment of EML4-ALK NSCLC by previous studies, but its effect on SRCA, an extremely rare subtype of lung adenocarcinoma, has yet to be elucidated. Therefore, the present study aimed to evaluate the clinical response of SRCA to crizotinib, and examine the potential use of crizotinib as a treatment for the carcinoma. A 43-year-old male was admitted to the Qingdao Municipal Hospital (Qingdao, China) with dyspnea. Chest computed tomography (CT) revealed a mass in the middle lobe of the right lung. Transbronchial lung biopsies revealed the presence of SRCA (70%) mixed with poorly-differentiated adenocarcinoma (30%). Immunohistochemically, the SRCA cells were positive for cytokeratin (CK)7 and thyroid transcription factor-1, and negative for CK20. An inversion of the EML4-ALK gene was detected by fluorescence in situ hybridization and crizotinib was injected by nasogastric tube. The patient was highly responsive to crizotinib. The symptoms of dyspnea were relieved and the volumes of pericardial and pleural effusion were gradually reduced. A CT scan revealed lung tumor regression. The overall response was a partial response. Therefore, crizotinib exists an attractive therapeutic option for patients with SRCA. However, in the present study, acquired drug resistance to crizotinib developed after only one month of treatment. It would consequently be valuable to investigate the mechanisms underlying acquired crizotinib resistance in future studies.

152P - Epidermal Growth Factor Receptor Signaling Conferred Acquired Crizotinib Resistance to a Non-Small Cell Lung Cancer Cell Line Harboring the Slc34A2-Ros1 Fusion Gene

ABSTRACT Aim: The ROS1 inhibitor crizotinib produces a remarkable response in patients with non-small cell lung cancer (NSCLC) harboring the ROS1 fusion gene (J Clin Oncol 2013 abstr 8032); however, acquired crizotinib resistance is inevitable, but the mechanism is unclear. Methods: HCC78 cells harboring the SLC34A2-ROS1 gene alteration were used to model acquired crizotinib resistance to explore alternative molecular mechanisms. The resistant cell line (HCC78R) was established from HCC78 cells after continuous exposure to crizotinib for 4 months in vitro. Results: The 50% inhibitory concentration (IC50) of crizotinib in HCC78R cells (4085.9 nM) was 47-fold larger than the IC50 in parental HCC78 cells (85.8 nM) (p = 0.0145). The expression of ROS1 protein was decreased significantly in HCC78R cells, as compared to HCC78 cells. Crizotinib inhibited the phosphorylation of AKT or ERK and downstream ROS1 signaling in HCC78 cells, but did not inhibit this in HCC78R. A receptor tyrosine kinas array showed that there was no increased tyrosine kinase activation in HCC78R cells, as compared to HCC78 cells. Interestingly, however, the phosphorylation of EGFR was maintained under 2,000 nM crizotinib exposure in HCC78R cells, but inhibited in parental HCC78 cells. Therefore, we hypothesize that the EGFR signaling pathway plays a role in HCC78R cells. Expectedly, HCC78R cells were very sensitive to EGFR-TKI in a cell proliferation assay (IC50: 117 nM vs. > 10,000 nM for HCC78R vs. HCC78 cells). Consistently, the addition of EGF to the culture medium rendered the parental HCC78 cells resistant to crizotinib. No activation of EGFR mutations were found in HCC78R cells. Finally, foretinib, a multi-kinase inhibitor of ROS1 and EGFR, effectively inhibited the proliferation of both HCC78R and HCC78 cells. Conclusions: These studies suggest that EGFR signaling plays a role in crizotinib resistance in lung cancer cells harboring ROS1 fusion genes. Disclosure: All authors have declared no conflicts of interest.

Co-Clinical Trials Demonstrate Superiority of Crizotinib to Chemotherapy in ALK-Rearranged Non–Small Cell Lung Cancer and Predict Strategies to Overcome Resistance

To extend the results of a phase III trial in patients with non-small cell lung cancer with adenocarcinomas harboring EML4-ALK fusion. We conducted a co-clinical trial in a mouse model comparing the ALK inhibitor crizotinib to the standard-of-care cytotoxic agents docetaxel or pemetrexed. Concordant with the clinical outcome in humans, crizotinib produced a substantially higher response rate compared with chemotherapy, associated with significantly longer progression-free survival. Overall survival was also prolonged in crizotinib- compared with chemotherapy-treated mice. Pemetrexed produced superior overall survival compared with docetaxel, suggesting that this agent may be the preferred chemotherapy in the ALK population. In addition, in the EML4-ALK-driven mouse lung adenocarcinoma model, HSP90 inhibition can overcome both primary and acquired crizotinib resistance. Furthermore, HSP90 inhibition, as well as the second-generation ALK inhibitor TAE684, demonstrated activity in newly developed lung adenocarcinoma models driven by crizotinib-insensitive EML4-ALK L1196M or F1174L. Our findings suggest that crizotinib is superior to standard chemotherapy in ALK inhibitor-naïve disease and support further clinical investigation of HSP90 inhibitors and second-generation ALK inhibitors in tumors with primary or acquired crizotinib resistance.

Concomitant occurrence of EGFR (epidermal growth factor receptor) and KRAS (V-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog) mutations in an ALK (anaplastic lymphoma kinase)-positive lung adenocarcinoma patient with acquired resistance to crizotinib: a case report

BackgroundAnaplastic lymphoma kinase-positive non-small cell lung carcinoma patients are generally highly responsive to the dual anaplastic lymphoma kinase and MET tyrosine kinase inhibitor crizotinib. However, they eventually acquire resistance to this drug, preventing the anaplastic lymphoma kinase inhibitors from having a prolonged beneficial effect. The molecular mechanisms responsible for crizotinib resistance are beginning to emerge, e.g., in some anaplastic lymphoma kinase-positive non-small cell lung carcinomas the development of secondary mutations in this gene has been described. However, the events behind crizotinib-resistance currently remain largely uncharacterized. Thus, we report on an anaplastic lymphoma kinase-positive non-small cell lung carcinoma patient with concomitant occurrence of epidermal growth factor receptor and V-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog mutations upon development of crizotinib-resistance.Case presentationA 61-year-old Caucasian never-smoking male was diagnosed with anaplastic lymphoma kinase -positive pulmonary adenocarcinoma, stage T4N3M1b. Treatment with crizotinib initially resulted in complete objective response in the thorax and partial response in the abdomen, but after 8 months of therapy the patient acquired resistance and progressed. Biopsies from new metastases revealed development of epidermal growth factor receptor and V-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog mutations concomitant with the original anaplastic lymphoma kinase gene rearrangement and without signs of anaplastic lymphoma kinase fusion gene amplification or secondary anaplastic lymphoma kinase mutations.ConclusionTo our knowledge, this is the first report of an anaplastic lymphoma kinase-positive pulmonary adenocarcinoma, which upon emergence of crizotinib resistance acquired 2 new somatic mutations in the epidermal growth factor receptor and V-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog genes, respectively, concomitant with the original anaplastic lymphoma kinase rearrangement. Thus, these 3 driver mutations, usually considered mutually exclusive, may coexist in advanced non-small cell lung carcinoma that becomes resistant to crizotinib, presumably because heterogeneous tumor clones utilize epidermal growth factor receptor and/or V-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog signaling to circumvent the inhibition of anaplastic lymphoma kinase-mediated signaling by crizotinib. The identification of new targetable somatic mutations by tumor re-biopsy may help clarify the mechanism behind the development of the acquired crizotinib resistance and pave the way for combined strategies involving multiple targeted therapies.

A retrospective analysis of the prevalence of EGFR or KRAS mutations in patients (pts) with crizotinib-naïve and crizotinib-resistant, ALK-positive non-small cell lung cancer (NSCLC).

8083 Background: Anaplastic lymphoma kinase (ALK) gene rearrangements define a distinct molecular subset of NSCLC. Recently, several studies have reported that ALK+ pts occasionally harbor concomitant mutations in other oncogenic drivers. Methods: We retrospectively analyzed tumor genotyping data from 1,683 pts with NSCLC seen at 3 U.S. centers from 2009 – 2012 to determine rates of overlapping alterations in EGFR, KRAS and ALK. Mutations in EGFR and KRAS were mainly identified using the SNaPshot multiplexed assay (>95% of cases). ALK FISH was performed in all cases. To determine if this prevalence is impacted by crizotinib, we also updated our earlier analysis (Katayama et al., Sci Transl Med, 2012) of a series of repeat biopsy specimens from 34 crizotinib-resistant, ALK+ pts. Resistant specimens were examined using ALK FISH, SNaPshot, and direct sequencing of the ALK tyrosine kinase domain (TKD). Results: Screening identified 301 (17.8%) EGFR mutations, 465 (27.6%) KRAS mutations, and 75 (4.4%) ALK rearrangements. EGFR mutations and ALK rearrangements were mutually exclusive. 4 pts with KRAS mutations also had abnormal ALK FISH patterns, involving isolated 5’ green probes (3/4 cases) and an isolated 3’ red probe that was unusually small (1/4 cases). Sufficient tissue was available for confirmatory ALK immunohistochemistry (clone 5A4, Novacastra, UK) in 3 of these cases, all of which were negative for ALK expression. Among pts with ALK+ NSCLC and acquired crizotinib resistance, repeat biopsy specimens remained ALK fusion positive in 28/28 (100%) cases. Secondary mutations in the ALK TKD (1151Tins, L1196M, G1202R, S1206Y, and G1269A) were identified in 7/34 (20.6%) cases. L1196M was the most common secondary mutation (3/34, 8.8% cases). ALK gene amplification was present in 3/28 (10.71%) pts. No EGFR or KRAS mutations were identified in 23 crizotinib-resistant, ALK+ pts with sufficient tissue for testing. Conclusions: Functional ALK rearrangements were mutually exclusive with EGFR and KRAS mutations in a large Western patient population. This lack of overlap was also observed in ALK+ pts with acquired resistance to crizotinib.

Abstract 5655: AP26113 possesses pan-inhibitory activity versus crizotinib-resistant ALK mutants and oncogenic ROS1 fusions.

Abstract AP26113 is a potent, reversible inhibitor of ALK fusions and mutant (but not native) EGFR. To overcome mutation-based resistance, AP26113 was designed to maintain activity against crizotinib-resistant ALK variants such as the gatekeeper ALK mutant L1196M. In an ongoing phase 1 dose-escalation study, AP26113 has achieved steady-state trough concentrations in excess of 1 μM and demonstrated promising clinical activity in both crizotinib-resistant and naïve ALK-positive NSCLC patients and preliminary evidence of activity in patients with mutant EGFR (#439O, ESMO 2012). To further assess the activity of AP26113 against crizotinib-resistant ALK mutants, and the structurally related ROS1 fusions recently identified in NSCLC, we engineered Ba/F3 cells to express the appropriate oncogenic drivers and evaluated their sensitivities to crizotinib and AP26113. Ba/F3 cell lines expressing clinically-identified EML4-ALK mutants (T1151T insertion, S1206Y, D1203N, L1196M, G1202R, F1174C and C1156Y) had substantially reduced sensitivity to crizotinib (viability IC50= 363-1296 nM) compared with native EML4-ALK (IC50= 137 nM). These data are consistent with the identification of these mutants in patients with acquired crizotinib resistance. AP26113 potently inhibited both native (IC50= 21 nM) and crizotinib-resistant ALK mutants (IC50= 26-254 nM) at concentrations substantially below the clinically achievable trough levels of AP26113 (1 μM), suggesting it may possess a pan-ALK inhibitory profile. AP26113 also effectively inhibited the viability of Ba/F3 cells expressing CD74-ROS1 (IC50= 18 nM), FIG-ROS1 (IC50= 31 nM), SDC4-ROS1 (IC50= 16 nM) and EZR-ROS1 (IC50= 41 nM) thus demonstrating that it is an equipotent inhibitor of ALK and ROS1. In a Ba/F3 CD74-ROS1 xenograft model, AP26113 inhibited tumor growth in a dose-dependent manner, with 50 mg/kg AP26113 inducing substantial tumor regression. Since ROS1 and ALK are structurally related and similarly sensitive to crizotinib, we reasoned that acquired drug resistance in ROS1-driven tumors may also occur via mutation. We therefore generated Ba/F3 cells driven by L2026M gatekeeper mutant forms of CD74-ROS1 and FIG-ROS1 and tested their drug sensitivity. Interestingly, the inhibitory capacity of AP26113 was unaffected by L2026M. In contrast, crizotinib potencies were reduced approximately 4-fold. In conclusion, we have demonstrated that AP26113 inhibits clinically relevant crizotinib- resistant ALK mutants and oncogenic ROS1 fusions recently identified in NSCLC irrespective of the fusion partner. Importantly, since AP26113 maintains potent activity against mutant forms of ALK and ROS1 at concentrations substantially below its human trough concentrations these data suggest that AP26113 may be able to prevent the emergence of drug-resistant mutants in NSCLC patients. Citation Format: Rachel M. Squillace, Rana Anjum, David Miller, Sadanand Vodala, Lauren Moran, Frank Wang, Tim Clackson, Andrew P. Garner, Victor M. Rivera. AP26113 possesses pan-inhibitory activity versus crizotinib-resistant ALK mutants and oncogenic ROS1 fusions. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5655. doi:10.1158/1538-7445.AM2013-5655

Heterogeneity of Genetic Changes Associated with Acquired Crizotinib Resistance in ALK-Rearranged Lung Cancer

Anaplastic lymphoma kinase (ALK)-rearranged non-small-cell lung cancer (NSCLC) is markedly sensitive to the ALK inhibitor crizotinib. However, acquired resistance to crizotinib is inevitable through several mechanisms. Therefore, this study was conducted to identify genetic alterations associated with crizotinib resistance. Tumor samples were derived from seven ALK-positive NSCLC patients who showed acquired resistance to crizotinib, and these patients were analyzed for ALK, EGFR, and KRAS mutations and ALK and EGFR gene amplifications. In vitro cytotoxicity of crizotinib and ALK downstream signals were compared between crizotinib-naive and -resistant NSCLC cells. After a median duration of 6 months (range, 4-12 months), seven ALK-positive NSCLC patients developed acquired resistance to crizotinib. Three patients harbored secondary ALK mutations, including one patient with both mutations: L1196M (n = 2) and G1269A (n = 2). Of note, one patient displayed ALK gene copy number gain (4.1-fold increase compared with the pre-crizotinib specimen) and EGFR L858R mutation with high polysomy. The amphiregulin concentration was high in the supernatant fluid from five patients with malignant pleural effusion (116.4-18934.0 pg/ml). SNU-2535 cells derived from a patient who harbored the G1269 mutation were resistant to crizotinib treatment similar to H3122 CR1 cells. L1196M and G1269A mutant clones were less sensitive to crizotinib and ALK downstream signals were ineffectively suppressed in these clones. Genetic changes associated with crizotinib resistance are heterogeneous in ALK-rearranged NSCLC patients who respond to crizotinib and subsequently develop resistance.

153 Heterogeneity of Genetic Changes Associated with Acquired Crizotinib Resistance in Anaplastic Lymphoma Kinase-Rearranged Lung Cancer

153 Heterogeneity of Genetic Changes Associated with Acquired Crizotinib Resistance in Anaplastic Lymphoma Kinase-Rearranged Lung Cancer

Detection of Anaplastic Lymphoma Kinase (ALK) Gene Rearrangement in Non-Small Cell Lung Cancer and Related Issues in ALK Inhibitor Therapy

Anaplastic lymphoma kinase (ALK) encodes a receptor tyrosine kinase, and ALK gene rearrangement (ALK+) is implicated in the oncogenesis of non-small cell lung carcinomas (NSCLCs), especially adenocarcinomas. The ALK inhibitor crizotinib was approved in August 2011 by the US Food and Drug Administration (FDA) for treating late-stage NSCLCs that are ALK+, with a companion fluorescent in situ hybridization (FISH) test using the Vysis ALK Break Apart FISH Probe Kit. This review covers pertinent issues in ALK testing, including approaches to select target patients for the test, pros and cons of different detection methods, and mechanisms as well as monitoring of acquired crizotinib resistance in ALK+ NSCLCs.

Abstract 5593: Mechanisms of acquired crizotinib resistance in ALK-rearranged lung cancers

Abstract ALK fusion oncogenes represent a novel molecular target in a small subset of non-small cell lung cancers (NSCLC). The vast majority of patients with ALK-positive NSCLC are highly responsive to ALK tyrosine kinase inhibitor (TKI) therapy. However, these patients invariably relapse, typically within one year, due to the development of resistance. Herein, we report findings from the first series of patients with acquired resistance to the ALK TKI crizotinib. In approximately one-third of patients, we identified a diverse array of secondary mutations distributed throughout the ALK TK domain. We also identified aberrant activation of other kinases as alternative mechanisms of crizotinib resistance. Additionally, we generated laboratory models of acquired crizotinib resistance which closely recapitulate the diversity of resistance mechanisms observed in patients. Our results highlight the marked heterogeneity of TKI resistance mechanisms in ALK-positive NSCLC, and provide the rationale for pursuing combinatorial therapeutic strategies in patients who relapse on crizotinib. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5593. doi:1538-7445.AM2012-5593

Mechanisms of Acquired Crizotinib Resistance in ALK-Rearranged Lung Cancers

Most anaplastic lymphoma kinase (ALK)-positive non-small cell lung cancers (NSCLCs) are highly responsive to treatment with ALK tyrosine kinase inhibitors (TKIs). However, patients with these cancers invariably relapse, typically within 1 year, because of the development of drug resistance. Herein, we report findings from a series of lung cancer patients (n = 18) with acquired resistance to the ALK TKI crizotinib. In about one-fourth of patients, we identified a diverse array of secondary mutations distributed throughout the ALK TK domain, including new resistance mutations located in the solvent-exposed region of the adenosine triphosphate-binding pocket, as well as amplification of the ALK fusion gene. Next-generation ALK inhibitors, developed to overcome crizotinib resistance, had differing potencies against specific resistance mutations. In addition to secondary ALK mutations and ALK gene amplification, we also identified aberrant activation of other kinases including marked amplification of KIT and increased autophosphorylation of epidermal growth factor receptor in drug-resistant tumors from patients. In a subset of patients, we found evidence of multiple resistance mechanisms developing simultaneously. These results highlight the unique features of TKI resistance in ALK-positive NSCLCs and provide the rationale for pursuing combinatorial therapeutics that are tailored to the precise resistance mechanisms identified in patients who relapse on crizotinib treatment.