UNASSIGNED: MET overexpression represents the most MET aberration in advanced non-small-cell lung cancer (NSCLC). However, except MET exon 14 (METex14) skipping mutation was recognized as a clinical biomarker, the role of MET overexpression as a predictive factor to MET inhibitor is not clear.
UNASSIGNED: The purpose of the pooled analysis is to explore the safety and efficiency of gumarontinib, a highly selective oral MET inhibitor, in drive-gene negative NSCLC patients with MET overexpression.
UNASSIGNED: NSCLC patients with MET overexpression [immunohistochemistry (IHC) ⩾3+ as determined by central laboratory] not carrying epidermal growth factor receptor mutation, METex14 skipping mutation or other known drive gene alternations who received Gumarontinib 300 mg QD from two single arm studies were selected and pooled for the analysis. The efficacy [objective response rate (ORR), disease control rate (DCR), duration of response, progression-free survival (PFS) and overall survival (OS)] and safety [treatment emergent adverse event (TEAE), treatment related AE (TRAE) and serious AE (SAE) were assessed.
UNASSIGNED: A total of 32 patients with MET overexpression were included in the analysis, including 12 treatment naïve patients who refused or were unsuitable for chemotherapy, and 20 pre-treated patients who received ⩾1 lines of prior systemic anti-tumour therapies. Overall, the ORR was 37.5% [95% confidence interval (CI): 21.1-56.3%], the DCR was 81.3% (95% CI: 63.6-92.8%), median PFS (mPFS) and median OS (mOS) were 6.9 month (95% CI: 3.6-9.7) and 17.0 month (95% CI: 10.3-not evaluable), respectively. The most common AEs were oedema (59.4%), hypoalbuminaemia (40.6%), alanine aminotransferase increased (31.3%).
UNASSIGNED: Gumarontinib showed promising antitumour activity in driver-gene negative locally advanced or metastatic NSCLC patients with MET overexpression, which warranted a further clinical trial.
UNASSIGNED: ClinicalTrials.gov identifier: NCT03457532; NCT04270591.

Precision medicine has helped identify several tumor molecular aberrations to be treated with targeted therapies. These therapies showed substantial improvement in efficacy without excessive toxicity in patients with specific oncogenic drivers with advanced cancers. In metastatic lung cancers, the implementation of broad platforms for molecular tumor sequencing has helped oncology providers identify oncogenic drivers linked with better outcomes when treated upfront with targeted therapies. Mesenchymal-epithelial transition factor (MET) alterations are present in up to 60% of non-small cell lung cancer and are associated with a poor prognosis. Capmatinib and tepotinib are currently the only two approved targeted therapies by the U.S. Food and Drug Administration (FDA) for patients with MET exon 14 skipping mutation. Several agents are being developed to tackle an unmet need in patients with MET alterations. Some of these agents are being used in combination with EGFR targeted therapy to mitigate resistance to EGFR inhibitor. These agents are poised to provide new hope for these patients.

Lung cancer is the leading cause of cancer death, accounting for one-third of all cancer deaths worldwide. The MET (c-MET) gene, as one of the therapeutic target spots of NSCLC, has become increasingly more important. MET amplification/overexpression was divided into primary (intrinsic) and secondary (acquired). Studies indicated that the combination of Osimertinib and Savolitinib was safe and showed promising antitumor effect in NSCLC patients with secondary MET amplification after EGFR mutations. However, NSCLC patients with primary MET amplification/overexpression and EGFR mutations are rare in clinics, and the efficacy of dual-target therapy combined with EGFR-TKI and Savolitinib for them has not been studied yet. Here, we reported two NSCLC patients with primary MET amplification/overexpression and EGFR mutation, who benefited from T+S therapy (the dual-target therapy of EGFR-TKI plus Savolitinib) and achieved a progression-free survival (PFS) of approximately 5 months. The two cases indicated that T+S therapy has an acceptable safety profile and encouraging antitumor efficacy in NSCLC patients harboring concurrent primary MET amplification/overexpression and EGFR mutation. Meanwhile, the observation stresses the importance of genetic testing, and the MET gene needs to be detected at first diagnosis for the best choice of targeted therapies.

MET alterations, including MET exon 14 skipping variants, MET amplification, MET overexpression, and MET fusion, play pivotal roles in primary tumorigenesis and acquired resistance to targeted therapies, especially EGFR tyrosine kinase inhibitors. They represent important diagnostic, prognostic, and predictive biomarkers in many solid tumor types. However, the detection of MET alterations is challenging due to the complexity of MET alterations and the diversity of platform technologies. Therefore, techniques with high sensitivity, specificity, and reliable molecular detection accuracy are needed to overcome such hindrances and aid in biomarker-guided therapies. The current review emphasizes the role of MET alterations as oncogenic drivers in a variety of cancers and their involvement in the development of resistance to targeted therapies. Moreover, our review provides an overview of and recommendations on the selection of various cross-platform technologies for the detection of MET exon 14 skipping variants, MET amplification, MET overexpression, and MET fusion. Furthermore, challenges and hurdles underlying these common detection platforms are discussed.

Non-Small-Cell Lung Cancer (NSCLC) can harbour different MET alterations, such as MET overexpression (MET OE), MET gene amplification (MET AMP), or MET gene mutations. Retrospective studies of surgical series of patients with MET-dysregulated NSCLC have shown worse clinical outcomes irrespective of the type of specific MET gene alteration. On the other hand, earlier attempts failed to identify the \'druggable\' molecular gene driver until the discovery of MET exon 14 skipping mutations (METex14). METex14 are rare and amount to around 3% of all NSCLCs. Patients with METex14 NSCLC attain modest results when they are treated with immune checkpoint inhibitors (ICIs). New selective MET inhibitors (MET-Is) showed a long-lasting clinical benefit in patients with METex14 NSCLC and modest activity in patients with MET AMP NSCLC. Ongoing clinical trials are investigating new small molecule tyrosine kinase inhibitors, bispecific antibodies, or antibodies drug conjugate (ADCs). This review focuses on the prognostic role of MET, the summary of pivotal clinical trials of selective MET-Is with a focus on resistance mechanisms. The last section is addressed to future developments and challenges.

Targeting the MET pathway in advanced NSCLC has been of particular interest due to its role as both a primary oncogenic driver and secondary oncogenic driver of acquired resistance. Activation of the MET pathway can occur through several mechanisms, which can complicate the diagnostic and treatment approach. Recently, several MET-directed therapies have been developed with promising results. In this narrative review, we summarize the biology and mechanism of MET as a clinically relevant driver mutation, distinct MET alterations including diagnostic challenges, significance in the setting of acquired resistance, and novel treatment strategies in advanced NSCLC.

BACKGROUND: Mesenchymal epithelial transition (MET) overexpression has been reported in approximately 50-60% of epidermal growth factor receptor (EGFR)-mutant non-small-cell lung cancers. However, the prognostic significance of MET overexpression has not been established in advanced lung adenocarcinoma (ADC) patients with EGFR-sensitive mutations.
METHODS: A retrospective study was performed on a total of 406 treatment-naïve advanced ADC patients with EGFR mutation detection and MET expression information. EGFR mutations were detected by next-generation sequencing or amplification refractory mutation system-polymerase chain reaction. Immuno-histochemistry staining of MET expression was evaluated by H-score and overexpression was defined as an H-score ≥ 200. Overall survival (OS) and progression-free survival (PFS) were analyzed according to MET expression.
RESULTS: Among the 406 patients, 208 patients had EGFR mutations, including 102 exon 19_del mutations, 94 L858R mutations and 12 other types of mutations. Of 110 patients with concomitant EGFR mutations and MET overexpression, 61 (59.8%) patients had 19_del mutations, 44 (46.8%) patients had L858R mutations and five (41.7%) patients had others. Patients with MET overexpression had a markedly shorter PFS and OS than patients with MET H-score < 200 in the EGFR L858R mutation subgroup (median PFS: 12 versus 26 months, p = 0.001; median OS: 24 versus 32 months, p = 0.038), whereas no significant difference was observed in 19_del mutation subgroup. Multivariate Cox analysis showed that MET overexpression was an independent poor prognostic factor for PFS and OS in patients with the L858R mutations (HR = 3.064, 95% CI 1.705-5.507, p < 0.001; HR = 2.043, 95% CI 1.000-4.172; p = 0.049), rather than 19_del.
CONCLUSIONS: MET overexpression is a poor prognostic factor for advanced ADC patients with the EGFR L858R mutation.

BACKGROUND: Thyroid cancer dedifferentiation is an unusual observation among young patients and is poorly understood, although a recent correlation to DICER1 gene mutations has been proposed.
METHODS: A 28-year old patient presented with a sub-centimeter cytology-verified primary papillary thyroid carcinoma (PTC) and a synchronous lateral lymph node metastasis. Following surgery, histopathology confirmed a 9 mm oxyphilic PTC and a synchronous metastasis of poorly differentiated thyroid carcinoma (PDTC). Extensive molecular examinations of both lesions revealed wildtype DICER1 sequences, but identified a somatic ETV6-NTRK3 gene fusion and a MET germline variant (c.1076G > A, p.Arg359Gln). MET is an established oncogene known to be overexpressed in thyroid cancer, and this specific alteration was not reported as a single nucleotide polymorphism (SNP), suggestive of a mutation. Both the primary PTC and the metastatic PDTC displayed strong MET immunoreactivity. A validation cohort of 50 PTCs from young patients were analyzed using quantitative real-time PCR, revealing significantly higher MET gene expression in tumors than normal thyroid controls, a finding which was particularly pronounced in BRAF V600E mutated cases. No additional tumors apart from the index case harbored the p.Arg359Gln MET mutation. Transfecting PTC cell lines MDA-T32 and MDA-T41 with a p.Arg359Gln MET plasmid construct revealed no obvious effects on cellular migratory or invasive properties, whereas overexpression of wildtype MET stimulated invasion.
CONCLUSIONS: The question of whether the observed MET mutation in any way influenced the dedifferentiation of a primary PTC into a PDTC metastasis remains to be established. Moreover, our data corroborate earlier studies, indicating that MET is aberrantly expressed in PTC and may influence the invasive behavior of these tumors.

Introduction: The MET gene and its pathway normally plays a crucial role in cell homeostasis, motility, and apoptosis. However, when the MET gene is altered, there is an imbalance toward cell proliferation and invasion commonly seen in numerous different types of cancers. The heterogeneous group of MET alterations that includes MET amplification, MET exon 14 skipping mutation, and MET fusions has been difficult to diagnose and treat. Currently, treatments are focused on tyrosine kinase inhibitors but now there is emerging data on novel MET-targeted therapies including monoclonal antibodies and antibody-drug conjugates that have emerged.Areas covered: We introduce new emerging data on MET alterations in non-small cell lung cancer (NSCLC) that has contributed to advances in MET targeted therapeutics. We offer our perspective and examine new information on the mechanisms of the MET alterations in this review.Expert opinion: Given the trends currently involving the targeting of MET altered malignancies, there will most likely be a continued rapid expansion of testing, novel tyrosine kinase inhibitors and potent antibody approaches. Combination treatments will be necessary to optimize management of advanced and early disease.

This study was conducted to investigate the expression of MET in Chinese gastric adenocarcinoma cohort, the correlation between MET overexpression and clinical pathological features, HER2 expression and MET gene amplification. A total of 816 gastric adenocarcinoma patients were included and MET and HER2 immunohistochemical (IHC) staining were performed. IHC and dual-color silver in situ hybridization analysis were performed in the tissue microarrays, constructed from the 240 patients who were randomly selected. MET overexpression (IHC 3+) was observed in 6.0% (49/816) of the cohort. MET overexpression rate was higher in patients with poor prognostic factors, such as clinical stages III/IV (p =0.012) and pathologic stages T3/T4 (p =0.027). The HER2 overexpression (IHC 3+) rate was 8.8% (72/816) and MET overexpression rate was higher in HER2 positive patients (9.7%, 7/72). A high concordance rate (94.6%) between MET overexpression and gene amplification was demonstrated. Therefore, MET overexpression could serve as a prognostic biomarker and a potential therapeutic target for gastric cancer.