[A new drug in thoracic oncology: MetMab (onartuzumab)]

Met pathway is activated in many solid cancers. In advanced non-small cell lung cancer (NSCLC), Met amplification is involved in 5 to 20% of acquired resistance to EGFR tyrosine kinase inhibitors (TKI) in tumors with initially sensitive EGFR mutation. MetMab (onartuzumab) is a monoclonal single-arm humanized anti-Met antibody. Its fixation on the Met receptor prevents the binding of the ligand (Hepatocyte Growth factor [HGF]) and the signal transduction. After promising results in preclinical and phase I trials, a randomized phase II trial has been conducted in advanced NSCLC in 2nd or 3rd line treatment. One hundred and twenty-eight patients have been randomized between an association of erlotinib+placebo and erlotinib+MetMab (15mg/kg IV every 3 weeks) until progression or toxicity. Patients with overexpression of Met in immunohistochemistry (IHC) had a progression-free survival (PFS) and an overall survival (OS) two-fold (median 1.5 versus 2.9 months; HR=0.53; P=0.04) and three-fold (median 3.8 versus 12.6 months; HR=0.37; P=0.002) longer, respectively, than patients with negative IHC score. The erlotinib+MetMab association had a worse effect on SSP and OS than the control arm in patients with negative IHC. The toxicity profile of MetMab is very good, and the main adverse effect is the occurrence of peripheral edemas, most of the time of low grade. A randomized phase III is on going to validate these results.

MET as a possible target for non-small-cell lung cancer

Lung cancer is a heterogeneous group of disorders that is now being subdivided into molecular subtypes with dedicated targeted therapies. The MET receptor tyrosine kinase has been identified as aberrantly overexpressed, potentially having activating mutations, and amplified in certain subsets of lung cancers. The ligand hepatocyte growth factor (HGF) can also be overexpressed in lung cancer or expressed in stroma, and both the MET receptor and the HGF ligand can be targets for therapeutics, especially in lung cancer. Activation of MET leads to a plethora of biochemical and biologic changes both in normal and cancerous cells. Preclinically, it has been shown that silencing or inactivating MET leads to decreased viability of cancer cells. There are a number of compounds against MET/HGF in clinical trials that have been shown to be active in lung cancers. This review will summarize the biology of MET as well as its therapeutic inhibition in lung cancer.

High MET expression is an adverse prognostic factor in patients with triple-negative breast cancer

Background:

The mesenchymal–epithelial transition (MET) pathway is frequently altered in tumours. The purpose of our study was to determine the prognostic value of tumour MET expression levels in patients with triple-negative breast cancer (TNBC), in order to strengthen the rationale for targeted therapy of TNBC using MET inhibitors.

Methods:

We determined expression of MET in formalin-fixed paraffin-embedded surgical specimens of TNBC by immunohistochemistry. Recurrence-free and overall survival was analysed with Cox models adjusted for clinical and pathological factors.

Results:

Immunostaining for MET was classified as high in 89 of 170 (52%) tumours. MET expression was more frequently observed in G3 carcinomas (P=0.02) but was not significantly associated to any of the other clinical or pathological parameters. High MET expression predicted shorter survival of the patients. Multivariate Cox proportional hazards regression analyses identified MET to be an independent prognostic factor for recurrence (adjusted hazard ratio (HR) for recurrence 3.43; 95% confidence interval (CI) 1.65–7.12; P=0.001) and death (adjusted HR for death 3.74; 95% CI 1.65–8.46; P=0.002).

Conclusion:

These results provide further evidence that the MET pathway could be exploited as a target for TNBC.

In the clinic: ongoing clinical trials evaluating c-MET-inhibiting drugs

The c-MET (mesenchymal-epithelial transition factor) pathway is dysregulated in many human cancers and promotes tumor growth, invasion and dissemination. The c-MET receptor tyrosine kinase can be activated via gene mutation, gene amplification, protein overexpression and/or a ligand-dependent autocrine/paracrine loop. Abnormalities in c-MET signaling have been reported to correlate with poor clinical outcomes and drug resistance in patients with cancer. Significant progress has been made in advancement of c-MET pathway inhibitors through to clinical trials. A robust pipeline of high-quality inhibitors targeting different aspects of c-MET activation is currently being explored in phase I, II and III clinical trials across multiple tumor types. Preliminary data demonstrate promising clinical activity with these agents, along with an acceptable toxicity profile. In this manuscript, the pharmacological profile of drugs targeting the c-MET pathway and available data from ongoing clinical trials of these drugs are discussed.

Targeting the hepatocyte growth factor-cMET axis in cancer therapy

The hepatocyte growth factor (HGF) and its receptor, the transmembrane tyrosine kinase cMET, promote cell proliferation, survival, motility, and invasion as well as morphogenic changes that stimulate tissue repair and regeneration in normal cells but can be co-opted during tumor growth. MET overexpression, with or without gene amplification, has been reported in a variety of human cancers, including breast, lung, and GI malignancies. Furthermore, high levels of HGF and/or cMET correlate with poor prognosis in several tumor types, including breast, ovarian, cervical, gastric, head and neck, and non-small-cell lung cancers. Gene amplification and protein overexpression of cMET drive resistance to epidermal growth factor receptor family inhibitors, both in preclinical models and in patients. It is increasingly apparent that the HGF-cMET axis signaling network is complex, and rational combinatorial therapy is needed for optimal clinical efficacy. Better understanding of HGF-cMET axis signaling and the mechanism of action of HGF-cMET inhibitors, along with the identification of biomarkers of response and resistance, will lead to more effective targeting of this pathway for cancer therapy.