Viola W. Zhu

Emergence of Preexisting MET Y1230C Mutation as a Resistance Mechanism to Crizotinib in NSCLC with MET Exon 14 Skipping

Introduction: MET proto‐oncogene, receptor tyrosine kinase gene exon 14 skipping (METex14) alterations represent a unique subset of oncogenic drivers in NSCLC. Preliminary clinical activity of crizotinib against METex14‐positive NSCLC has been reported. The full spectrum of resistance mechanisms to crizotinib in METex14‐positive NSCLC remains to be identified. Methods: Hybrid capture–based comprehensive genomic profiling performed on a tumor specimen obtained at diagnosis, and a hybrid capture–based assay of circulating tumor DNA (ctDNA) at the time of progression during crizotinib treatment was assessed in a pairwise fashion. Results: A METex14 alteration (D1010H) was detected in the pretreatment tumor biopsy specimen, as was MET proto‐oncogene, receptor tyrosine kinase (MET) Y1230C, retrospectively, at very low frequency (0.3%). After a confirmed response during crizotinib treatment for 13 months followed by progression, both MET proto‐oncogene, receptor tyrosine kinase gene Y1230C and D1010H were detected prospectively in the ctDNA. Conclusion: Emergence of the preexisting MET Y1230C likely confers resistance to crizotinib in this case of METex14‐positive NSCLC. Existence of pretreatment MET Y1230C may eventually modulate the response of METex14‐positive NSCLC to type I MET tyrosine kinase inhibitors. Noninvasive plasma‐based ctDNA assays can provide a convenient method to detect resistance mutations in patients with previously known driver mutations.

Impact of EML4-ALK Variant on Resistance Mechanisms and Clinical Outcomes in ALK-Positive Lung Cancer

Purpose Advanced anaplastic lymphoma kinase ( ALK) fusion-positive non-small-cell lung cancers (NSCLCs) are effectively treated with ALK tyrosine kinase inhibitors (TKIs). However, clinical outcomes in these patients vary, and the benefit of TKIs is limited as a result of acquired resistance. Emerging data suggest that the ALK fusion variant may affect clinical outcome, but the molecular basis for this association is unknown. Patients and Methods We identified 129 patients with ALK-positive NSCLC with known ALK variants. ALK resistance mutations and clinical outcomes on ALK TKIs were retrospectively evaluated according to ALK variant. A Foundation Medicine data set of 577 patients with ALK-positive NSCLC was also examined. Results The most frequent ALK variants were EML4-ALK variant 1 in 55 patients (43%) and variant 3 in 51 patients (40%). We analyzed 77 tumor biopsy specimens from patients with variants 1 and 3 who had progressed on an ALK TKI. ALK resistance mutations were significantly more common in variant 3 than in variant 1 (57% v 30%; P = .023). In particular, ALK G1202R was more common in variant 3 than in variant 1 (32% v 0%; P < .001). Analysis of the Foundation Medicine database revealed similar associations of variant 3 with ALK resistance mutation and with G1202R ( P = .010 and .015, respectively). Among patients treated with the third-generation ALK TKI lorlatinib, variant 3 was associated with a significantly longer progression-free survival than variant 1 (hazard ratio, 0.31; 95% CI, 0.12 to 0.79; P = .011). Conclusion Specific ALK variants may be associated with the development of ALK resistance mutations, particularly G1202R, and provide a molecular link between variant and clinical outcome. ALK variant thus represents a potentially important factor in the selection of next-generation ALK inhibitors.

TPD52L1-ROS1, a new ROS1 fusion variant in lung adenosquamous cell carcinoma identified by comprehensive genomic profiling

Crizotinib was approved for the treatment of ROS1-rearranged non-small cell lung cancer (NSCLC) patients in the US on 11 March, 2016. Interestingly no one companion diagnostic test (CDx) has been approved simultaneously with this approval of crizotinib. Hence, an ideal and adequate CDx will have to be able to identify ROS1 fusions without the knowledge of the fusion partners to ROS1, and as to date there are 13 fusion partners reported for ROS1 in NSCLC. Here we report a novel TPD52L1-ROS1 fusion variant in NSCLC. This novel TPD52L1-ROS1 fusion variant is generated by the fusion of exons 1-3 of TPD52L1 on chromosome 6q22-23 to the exons 33-43 of ROS1 on chromosome 6q22, likely from an intra-chromosomal deletion and subsequent fusion event similar to the generation of EML4-ALK. The predicted TPD52L1-ROS1 protein product contains 655 amino acids comprising of the N-terminal amino acids 1-95 of TPD52L1 and C-terminal amino acids of 1789-2348 of ROS1. In summary, TPD52L1-ROS1 is a novel ROS1 fusion variant in NSCLC identified by comprehensive genomic profiling and should be included in any ROS1 detecting assays that depend on identifying the corresponding fusion partners, such as reverse transcriptase-polymerase chain reaction (RT-PCR).

Dual occurrence of ALK G1202R solvent front mutation and small cell lung cancer transformation as resistance mechanisms to second generation ALK inhibitors without prior exposure to crizotinib. Pitfall of solely relying on liquid re-biopsy?

Development of the acquired ALK G1202R solvent front mutation and small cell lung cancer (SCLC) transformation have both been independently reported as resistance mechanisms to ALK inhibitors in ALK-rearranged (ALK+) non-small cell lung cancer (NSCLC) patients but have not been reported in the same patient. Here we report an ALK+ NSCLC patient who had disease progression after ceritinib and then alectinib where an ALK G1202R mutation was detected on circulating tumor (ct) DNA prior to enrollment onto a trial of another next generation ALK inhibitor, lorlatinib. The patients central nervous system (CNS) metastases responded to lorlatinib together with clearance of ALK G1202R mutation by repeat ctDNA assay. However, the patient developed a new large pericardial effusion. Resected pericardium from the pericardial window revealed SCLC transformation with positive immunostaining for synaptophysin, chromogranin, and ALK (D5F3 antibody). Comprehensive genomic profiling (CGP) of the tumor infiltrating pericardium revealed the retainment of an ALK rearrangement with emergence of an inactivating Rb1 mutation (C706Y) and loss of exons 1-11 in p53 that was not detected in the original tumor tissue at diagnosis. The patient was subsequently treated with carboplatin/etoposide and alectinib, but had rapid clinical deterioration and died. The patient never received crizotinib. This case illustrates that multiple/compound resistance mechanisms to ALK inhibitors can occur and provide supporting information that loss of p53 and Rb1 are important in SCLC transformation. If clinically feasible, tissue-based re-biopsy allowing histological examination and CGP remains the gold standard to assess resistance mechanism(s) and to direct subsequent rational clinical care.

The race to target MET exon 14 skipping alterations in non-small cell lung cancer: The Why, the How, the Who, the Unknown, and the Inevitable.

A number of small molecule tyrosine kinase inhibitors (TKIs) have now been approved for the treatment of non-small cell lung cancers (NSCLC), including those targeted against epidermal growth factor receptor, anaplastic lymphoma kinase, and ROS1. Despite a wealth of agents developed to target the receptor tyrosine kinase, MET, clinical outcomes have as yet been disappointing, leading to pessimism about the role of MET in the pathogenesis of NSCLC. However, in recent years, there has been a renewed interest in MET exon 14 alterations as potential drivers of lung cancer. MET exon 14 alterations, which result in increased MET protein levels due to disrupted ubiquitin-mediated degradation, occur at a prevalence of around 3% in adenocarcinomas and around 2% in other lung neoplasms, making them attractive targets for the treatment of lung cancer. At least five MET-targeted TKIs, including crizotinib, cabozantinib, capmatinib, tepotinib, and glesatinib, are being investigated clinically for patients with MET exon 14 altered-NSCLC. A further two compounds have shown activity in preclinical models. In this article, we review the current clinical and preclinical data available for these TKIs, along with a number of other potential therapeutic options, including antibodies and immunotherapy. A number of questions remain unanswered regarding the future of MET TKIs, but unfortunately, the development of resistance to targeted therapies is inevitable. Resistance is expected to arise as a result of receptor tyrosine kinase mutation or from upregulation of MET ligand expression; potential strategies to overcome resistance are proposed.

Identification of a novel T1151K ALK mutation in a patient with ALK-rearranged NSCLC with prior exposure to crizotinib and ceritinib.

Patients with anaplastic lymphoma kinase (ALK)-rearranged non-small cell lung cancer (NSCLC) derive significant clinic benefit from treatment with ALK inhibitors. Crizotinib was the first approved tyrosine kinase inhibitor (TKI) for this distinct molecular subset of NSCLC. Disease progression on TKI inevitably arises secondary to diverse resistance mechanisms among which emergence of secondary ALK mutations is one of many ways in which tumor cells have adapted to survive. Therefore there is a clinical imperative to identify acquired ALK mutations via repeat tissue biopsy if clinically feasible. If such is present, switching to a different TKI with known clinical activities against the emergent resistance mutation (s) may pose a viable treatment option. Here we report for the first time a novel ALK T1151K mutation in a patient with metastatic ALK-rearranged NSCLC who progressed on crizotinib and then ceritinib. The co-crystal structure of ceritinib/ALK demonstrates a strong interaction between ceritinib and the P-loop which is facilitated by T1151 on the β3 sheet, a feature not present in the alectinib/ALK or lorlatinib/ALK co-crystal structure. It is predicated that the T1151K mutation weakens these interactions leading to drug resistance, or causes conformational changes of the ALK catalytic domain resulting in higher affinity for ATP and therefore diminished inhibitor binding. We conclude that the T1151K ALK mutation confers resistance to ceritinib, which may be rescued by alectinib or lorlatinib as evidenced by this clinical narrative.

Expression of the chitinase family glycoprotein YKL-40 in undifferentiated, differentiated and trans-differentiated mesenchymal stem cells.

The glycoprotein YKL-40 (CHI3L1) is a secreted chitinase family protein that induces angiogenesis, cell survival, and cell proliferation, and plays roles in tissue remodeling and immune regulation. It is expressed primarily in cells of mesenchymal origin, is overexpressed in numerous aggressive carcinomas and sarcomas, but is rarely expressed in normal ectodermal tissues. Bone marrow-derived mesenchymal stem cells (MSCs) can be induced to differentiate into various mesenchymal tissues and trans-differentiate into some non-mesenchymal cell types. Since YKL-40 has been used as a mesenchymal marker, we followed YKL-40 expression as undifferentiated MSCs were induced to differentiate into bone, cartilage, and neural phenotypes. Undifferentiated MSCs contain significant levels of YKL-40 mRNA but do not synthesize detectable levels of YKL-40 protein. MSCs induced to differentiate into chondrocytes and osteocytes soon began to express and secrete YKL-40 protein, as do ex vivo cultured chondrocytes and primary osteocytes. In contrast, MSCs induced to trans-differentiate into neurons did not synthesize YKL-40 protein, consistent with the general absence of YKL-40 protein in normal CNS parenchyma. However, these trans-differentiated neurons retained significant levels of YKL-40 mRNA, suggesting the mechanisms which prevented YKL-40 translation in undifferentiated MSCs remained in place, and that these trans-differentiated neurons differ in at least this way from neurons derived from neuronal stem cells. Utilization of a differentiation protocol containing β-mercaptoethanol resulted in cells that expressed significant amounts of intracellular YKL-40 protein that was not secreted, which is not seen in normal cells. Thus the synthesis of YKL-40 protein is a marker for MSC differentiation into mature mesenchymal phenotypes, and the presence of untranslated YKL-40 mRNA in non-mesenchymal cells derived from MSCs reflects differences between differentiated and trans-differentiated phenotypes.

Brigatinib in Patients With Alectinib-Refractory ALK-Positive NSCLC

Introduction: The second‐generation anaplastic lymphoma kinase (ALK) inhibitor alectinib recently showed superior efficacy compared to the first‐generation ALK inhibitor crizotinib in advanced ALK‐rearranged NSCLC, establishing alectinib as the new standard first‐line therapy. Brigatinib, another second‐generation ALK inhibitor, has shown substantial activity in patients with crizotinib‐refractory ALK‐positive NSCLC; however, its activity in the alectinib‐refractory setting is unknown. Methods: A multicenter, retrospective study was performed at three institutions. Patients were eligible if they had advanced, alectinib‐refractory ALK‐positive NSCLC and were treated with brigatinib. Medical records were reviewed to determine clinical outcomes. Results: Twenty‐two patients were eligible for this study. Confirmed objective responses to brigatinib were observed in 3 of 18 patients (17%) with measurable disease. Nine patients (50%) had stable disease on brigatinib. The median progression‐free survival was 4.4 months (95% confidence interval [CI]: 1.8–5.6 months) with a median duration of treatment of 5.7 months (95% CI: 1.8–6.2 months). Among 9 patients in this study who underwent post‐alectinib/pre‐brigatinib biopsies, 5 had an ALK I1171X or V1180L resistance mutation; of these, 1 had a confirmed partial response and 3 had stable disease on brigatinib. One patient had an ALK G1202R mutation in a post‐alectinib/pre‐brigatinib biopsy, and had progressive disease as the best overall response to brigatinib. Conclusions: Brigatinib has limited clinical activity in alectinib‐refractory ALK‐positive NSCLC. Additional studies are needed to establish biomarkers of response to brigatinib and to identify effective therapeutic options for alectinib‐resistant ALK‐positive NSCLC patients.

Safety of alectinib for the treatment of metastatic ALK-rearranged non-small cell lung cancer

ABSTRACT Introduction: Patients with anaplastic lymphoma kinase (ALK)-rearranged non-small cell lung cancer (NSCLC) may derive significant clinical benefit from targeted therapies against this driver mutation, but progression is virtually inevitable. Alectinib is a next-generation ALK inhibitor that provides a novel treatment option for this group of patients. Areas covered: In this review, we summarize the overall safety and tolerability of alectinib. Specifically, we cover cardiovascular, gastrointestinal, hepatic, musculoskeletal, and respiratory adverse events. The safety profile of alectinib is also described in special populations and in comparison with other ALK inhibitors. Expert opinion: Alectinib is a well-tolerated tyrosine kinase inhibitor and should be considered for patients with ALK-rearranged NSCLC. The question then arises as to how to choose a next-generation ALK inhibitor in the second-line setting. Understanding acquired resistant mechanisms has become essential. Whether or not to use alectinib in the first-line setting is extremely controversial, but we anticipate its approval for this indication and availability in more countries in the near future.

ASCEND-2: a canary in a coal mine for descending to second-line treatment for ALK -rearranged non-small cell lung cancer

The discovery of oncogenic driver mutations has revolutionized the management of non-small cell lung cancer (NSCLC) for the past decade. The prevalence of anaplastic lymphoma kinase ( ALK ) rearrangement in NSCLC is estimated to be 2–7% (1). Crizotinib, a tyrosine kinase inhibitor (TKI), which targets ALK as well as ROS1 and c-MET, was approved by the U.S. Food and Drug Administration (FDA) in 2011 for the treatment of metastatic ALK -rearranged NSCLC. Several studies have demonstrated a median progression-free survival (PFS) of approximately 8 to 11 months and response rates of 65% to 75% (2,3). However, as with other targeted therapies, patients eventually progress due to the emergence of acquired resistance via the activation or inhibition of alternative signaling pathways, secondary ALK mutations, or amplification of the ALK fusion gene.