Fully Human Monoclonal Antibodies to Hepatocyte Growth Factor with Therapeutic Potential against Hepatocyte Growth Factor/c-Met–Dependent Human Tumors

c-Met+ Cytotoxic T Lymphocytes Exhibit Enhanced Cytotoxicity in Mice and Humans In Vitro Tumor Models

CD8+ cytotoxic T lymphocytes (CTLs) play a crucial role in anti-tumor immunity. In a previous study, we identified a subset of murine effector CTLs expressing the hepatocyte growth factor (HGF) receptor, c-Met (c-Met+ CTLs), that are endowed with enhanced cytolytic capacity. HGF directly inhibited the cytolytic function of c-Met+ CTLs, both in 2D in vitro assays and in vivo, leading to reduced T cell responses against metastatic melanoma. To further investigate the role of c-Met+ CTLs in a three-dimensional (3D) setting, we studied their function within B16 melanoma spheroids and examined the impact of cell-cell contact on the modulation of inhibitory checkpoint molecules' expression, such as KLRG1, PD-1, and CTLA-4. Additionally, we evaluated the cytolytic capacity of human CTL clones expressing c-Met (c-Met+) and compared it to c-Met- CTL clones. Our results indicated that, similar to their murine counterparts, c-Met+ human CTL clones exhibited increased cytolytic activity compared to c-Met- CTL clones, and this enhanced function was negatively regulated by the presence of HGF. Taken together, our findings highlight the potential of targeting the HGF/c-Met pathway to modulate CTL-mediated anti-tumor immunity. This research holds promise for developing strategies to enhance the effectiveness of CTL-based immunotherapies against cancer.

Rilotumumab Resistance Acquired by Intracrine Hepatocyte Growth Factor Signaling

Drug resistance is a long-standing impediment to effective systemic cancer therapy and acquired drug resistance is a growing problem for molecularly-targeted therapeutics that otherwise have shown unprecedented successes in disease control. The hepatocyte growth factor (HGF)/Met receptor pathway signaling is frequently involved in cancer and has been a subject of targeted drug development for nearly 30 years. To anticipate and study specific resistance mechanisms associated with targeting this pathway, we engineered resistance to the HGF-neutralizing antibody rilotumumab in glioblastoma cells harboring autocrine HGF/Met signaling, a frequent abnormality of this brain cancer in humans. We found that rilotumumab resistance was acquired through an unusual mechanism comprising dramatic HGF overproduction and misfolding, endoplasmic reticulum (ER) stress-response signaling and redirected vesicular trafficking that effectively sequestered rilotumumab and misfolded HGF from native HGF and activated Met. Amplification of MET and HGF genes, with evidence of rapidly acquired intron-less, reverse-transcribed copies in DNA, was also observed. These changes enabled persistent Met pathway activation and improved cell survival under stress conditions. Point mutations in the HGF pathway or other complementary or downstream growth regulatory cascades that are frequently associated with targeted drug resistance in other prevalent cancer types were not observed. Although resistant cells were significantly more malignant, they retained sensitivity to Met kinase inhibition and acquired sensitivity to inhibition of ER stress signaling and cholesterol biosynthesis. Defining this mechanism reveals details of a rapidly acquired yet highly-orchestrated multisystem route of resistance to a selective molecularly-targeted agent and suggests strategies for early detection and effective intervention.

Targeting HGF/c-MET Axis in Pancreatic Cancer

Pancreatic cancer (pancreatic ductal adenocarcinoma (PDAC/PC)) has been an aggressive disease that is associated with early metastases. It is characterized by dense and collagenous desmoplasia/stroma, predominantly produced by pancreatic stellate cells (PSCs). PSCs interact with cancer cells as well as other stromal cells, facilitating disease progression. A candidate growth factor pathway that may mediate this interaction is the hepatocyte growth factor (HGF)/c-MET pathway. HGF is produced by PSCs and its receptor c-MET is expressed on pancreatic cancer cells and endothelial cells. The current review discusses the role of the MET/HGF axis in tumour progression and dissemination of pancreatic cancer. Therapeutic approaches that were developed targeting either the ligand (HGF) or the receptor (c-MET) have not been shown to translate well into clinical settings. We discuss a two-pronged approach of targeting both the components of this pathway to interrupt the stromal-tumour interactions, which may represent a potential therapeutic strategy to improve outcomes in PC.

Receptor Tyrosine Kinases: Principles and Functions in Glioma Invasion

Protein tyrosine kinases are enzymes that are capable of adding a phosphate group to specific tyrosines on target proteins. A receptor tyrosine kinase (RTK) is a tyrosine kinase located at the cellular membrane and is activated by binding of a ligand via its extracellular domain. Protein phosphorylation by kinases is an important mechanism for communicating signals within a cell and regulating cellular activity; furthermore, this mechanism functions as an "on" or "off" switch in many cellular functions. Ninety unique tyrosine kinase genes, including 58 RTKs, were identified in the human genome; the products of these genes regulate cellular proliferation, survival, differentiation, function, and motility. Tyrosine kinases play a critical role in the development and progression of many types of cancer, in addition to their roles as key regulators of normal cellular processes. Recent studies have revealed that RTKs such as epidermal growth factor receptor (EGFR), platelet-derived growth factor receptor (PDGFR), c-Met, Tie, Axl, discoidin domain receptor 1 (DDR1), and erythropoietin-producing human hepatocellular carcinoma (Eph) play a major role in glioma invasion. Herein, we summarize recent advances in understanding the role of RTKs in glioma pathobiology, especially the invasive phenotype, and present the perspective that RTKs are a potential target of glioma therapy.

A Biparatopic Antibody That Modulates MET Trafficking Exhibits Enhanced Efficacy Compared with Parental Antibodies in MET-Driven Tumor Models

PURPOSE

Recent clinical data demonstrate that tumors harboring MET genetic alterations (exon 14 skip mutations and/or gene amplification) respond to small-molecule tyrosine kinase inhibitors, validating MET as a therapeutic target. Although antibody-mediated blockade of the MET pathway has not been successful in the clinic, the failures are likely the result of inadequate patient selection strategies as well as suboptimal antibody design. Thus, our goal was to generate a novel MET blocking antibody with enhanced efficacy.

EXPERIMENTAL DESIGN

Here, we describe the activity of a biparatopic MET×MET antibody that recognizes two distinct epitopes in the MET Sema domain. We use a combination of in vitro assays and tumor models to characterize the effect of our antibody on MET signaling, MET intracellular trafficking, and the growth of MET-dependent cells/tumors.

RESULTS

In MET-driven tumor models, our biparatopic antibody exhibits significantly better activity than either of the parental antibodies or the mixture of the two parental antibodies and outperforms several clinical-stage MET antibodies. Mechanistically, the biparatopic antibody inhibits MET recycling, thereby promoting lysosomal trafficking and degradation of MET. In contrast to the parental antibodies, the biparatopic antibody fails to activate MET-dependent biological responses, consistent with the observation that it recycles inefficiently and induces very transient downstream signaling.

CONCLUSIONS

Our results provide strong support for the notion that biparatopic antibodies are a promising therapeutic modality, potentially having greater efficacy than that predicted from the properties of the parental antibodies.

Preparation of a Novel One-Armed Anti-c-Met Antibody with Antitumor Activity Against Hepatocellular Carcinoma

Introduction

Antibody-based c-mesenchymal–epithelial transition factor (c-Met) inhibition is a promising strategy for hepatocellular carcinoma (HCC) treatment, but the intrinsic agonistic activity of the anti-c-Met antibody limits its application in drug development. Constructing a monovalent one-armed antibody has been reported to be an effective way to create an inhibitory anti-c-Met antibody.

Materials and methods

In the present study, a novel monovalent one-armed anti-c-Met antibody was constructed using the knobs-into-holes technology, and its inhibitory effects against HCC and the underlying mechanisms were explored.

Results

The one-armed anti-c-Met antibody blocked the hepatocyte growth factor (HGF)/c-Met interaction and the subsequent signal transduction, including phosphorylation of c-Met, Grb2-associated binding protein 1(Gab-1), extracellular regulated protein kinases 1/2(Erk1/2), and Akt, also referred to as protein kinase B (PKB) in HCC cell line HepG2. Furthermore, the autocrine stimulation of HepG2 cell proliferation and HGF-induced HCC cell migration were strongly inhibited by the one-armed anti-c-Met antibody. In addition, the antibody also reduced the HGF-induced proliferation and tube formation of human umbilical vein endothelial cells (HUVECs). Treating HepG2-bearing mice with the one-armed anti-c-Met antibody significantly inhibited the tumor growth in the xenograft nude mouse model.

Conclusion

The one-armed anti-c-Met antibody derived from the full-length bivalent anti-c-Met antibody might serve as a potential antitumor agent against HCC.

MET in glioma: signaling pathways and targeted therapies

Gliomas represent the most common type of malignant brain tumor, among which, glioblastoma remains a clinical challenge with limited treatment options and dismal prognosis. It has been shown that the dysregulated receptor tyrosine kinase (RTK, including EGFR, MET, PDGFRα, ect.) signaling pathways have pivotal roles in the progression of gliomas, especially glioblastoma. Increasing evidence suggests that expression levels of the RTK MET and its specific stimulatory factors are significantly increased in glioblastomas compared to those in normal brain tissues, whereas some negative regulators are found to be downregulated. Mutations in MET, as well as the dysregulation of other regulators of cross-talk with MET signaling pathways, have also been identified. MET and its ligand hepatocyte growth factor (HGF) play a critical role in the proliferation, survival, migration, invasion, angiogenesis, stem cell characteristics, and therapeutic resistance and recurrence of glioblastomas. Therefore, combined targeted therapy for this pathway and associated molecules could be a novel and attractive strategy for the treatment of human glioblastoma. In this review, we highlight progress made in the understanding of MET signaling in glioma and advances in therapies targeting HGF/MET molecules for glioma patients in recent years, in addition to studies on the expression and mutation status of MET.

Pharmacologic Characterization of ALD1910, a Potent Humanized Monoclonal Antibody against the Pituitary Adenylate Cyclase-Activating Peptide

Migraine is a debilitating disease that affects almost 15% of the population worldwide and is the first cause of disability in people under 50 years of age, yet its etiology and pathophysiology remain incompletely understood. Recently, small molecules and therapeutic antibodies that block the calcitonin gene-related peptide (CGRP) signaling pathway have reduced migraine occurrence and aborted acute attacks of migraine in clinical trials and provided prevention in patients with episodic and chronic migraine. Heterogeneity is present within each diagnosis and patient's response to treatment, suggesting migraine as a final common pathway potentially activated by multiple mechanisms, e.g., not all migraine attacks respond to or are prevented by anti-CGRP pharmacological interventions. Consequently, other unique mechanisms central to migraine pathogenesis may present new targets for drug development. Pituitary adenylate cyclase-activating peptide (PACAP) is an attractive novel target for treatment of migraines. We generated a specific, high-affinity, neutralizing monoclonal antibody (ALD1910) with reactivity to both PACAP38 and PACAP27. In vitro, ALD1910 effectively antagonizes PACAP38 signaling through the pituitary adenylate cyclase-activating peptide type I receptor, vasoactive intestinal peptide receptor 1, and vasoactive intestinal peptide receptor 2. ALD1910 recognizes a nonlinear epitope within PACAP and blocks its binding to the cell surface. To test ALD1910 antagonistic properties directed against endogenous PACAP, we developed an umbellulone-induced rat model of neurogenic vasodilation and parasympathetic lacrimation. In vivo, this model demonstrates that the antagonistic activity of ALD1910 is dose-dependent, retaining efficacy at doses as low as 0.3 mg/kg. These results indicate that ALD1910 represents a potential therapeutic antibody to address PACAP-mediated migraine.

Synthesis of novel 6,7-dimethoxy-4-anilinoquinolines as potent c-Met inhibitors

HGF/c-Met signalling pathway plays an important role in the development of cancers. A series of 6,7-dimethoxy-4-anilinoquinolines possessing benzimidazole moiety were synthesised and identified as potent inhibitors of the tyrosine kinase c-Met. Their in vitro biological activities against three cancer cell lines (A549, MCF-7, and MKN-45) were also evaluated. Most of these compounds exhibited moderate to remarkable potency. Among them, compound 12n showed the most potent inhibitory activity against c-Met with IC₅₀ value of 0.030 ± 0.008 µM and it also showed excellent anticancer activity against the tested cancer cell lines at low micromolar concentration. Molecular docking verified the results and revealed the possible binding mode of the most promising compound 12n into the ATP-binding site of c-Met kinase.

A review of soft-tissue sarcomas: translation of biological advances into treatment measures

Soft-tissue sarcomas are rare malignant tumors arising from connective tissues and have an overall incidence of about five per 100,000 per year. While this diverse family of malignancies comprises over 100 histological subtypes and many molecular aberrations are prevalent within specific sarcomas, very few are therapeutically targeted. Instead of utilizing molecular signatures, first-line sarcoma treatment options are still limited to traditional surgery and chemotherapy, and many of the latter remain largely ineffective and are plagued by disease resistance. Currently, the mechanism of sarcoma oncogenesis remains largely unknown, thus necessitating a better understanding of pathogenesis. Although substantial progress has not occurred with molecularly targeted therapies over the past 30 years, increased knowledge about sarcoma biology could lead to new and more effective treatment strategies to move the field forward. Here, we discuss biological advances in the core molecular determinants in some of the most common soft-tissue sarcomas - liposarcoma, angiosarcoma, leiomyosarcoma, rhabdomyosarcoma, Ewing's sarcoma, and synovial sarcoma - with an emphasis on emerging genomic and molecular pathway targets and immunotherapeutic treatment strategies to combat this confounding disease.

Immunotherapies: Exploiting the Immune System for Cancer Treatment

Cancer is a condition that has plagued humanity for thousands of years, with the first depictions dating back to ancient Egyptian times. However, not until recent decades have biological therapeutics been developed and refined enough to safely and effectively combat cancer. Three unique immunotherapies have gained traction in recent decades: adoptive T cell transfer, checkpoint inhibitors, and bivalent antibodies. Each has led to clinically approved therapies, as well as to therapies in preclinical and ongoing clinical trials. In this review, we outline the method by which these 3 immunotherapies function as well as any major immunotherapeutic drugs developed for treating a variety of cancers.

Rilotumumab plus epirubicin, cisplatin, and capecitabine as first-line therapy in advanced MET-positive gastric or gastro-oesophageal junction cancer (RILOMET-1): a randomised, double-blind, placebo-controlled, phase 3 trial

BACKGROUND

Rilotumumab is a fully human monoclonal antibody that selectively targets the ligand of the MET receptor, hepatocyte growth factor (HGF). We aimed to assess the efficacy, safety, and pharmacokinetics of rilotumumab combined with epirubicin, cisplatin, and capecitabine, and to assess potential biomarkers, in patients with advanced MET-positive gastric or gastro-oesophageal junction adenocarcinoma.

METHODS

This multicentre, randomised, double-blind, placebo-controlled, phase 3 study was done at 152 centres in 27 countries. We recruited adults (aged ≥18 years) with unresectable locally advanced or metastatic gastric or gastro-oesophageal junction adenocarcinoma, an Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1, MET-positive tumours (≥25% of tumour cells with membrane staining of ≥1+ staining intensity), and evaluable disease, who had not received previous systemic therapy. Eligible patients were randomly assigned (1:1) via a computerised voice response system to receive rilotumumab 15 mg/kg intravenously or placebo in combination with open-label chemotherapy (epirubicin 50 mg/m² intravenously; cisplatin 60 mg/m² intravenously; capecitabine 625 mg/m² orally twice daily) in 21-day cycles for up to ten cycles. After completion of chemotherapy, patients continued to receive rilotumumab or placebo monotherapy until disease progression, intolerability, withdrawal of consent, or study termination. Randomisation was stratified by disease extent and ECOG performance status. Both patients and physicians were masked to study treatment assignment. The primary endpoint was overall survival, analysed by intention to treat. We report the final analysis. This study is registered with ClinicalTrials.gov, number NCT01697072.

FINDINGS

Between Nov 7, 2012, and Nov 21, 2014, 609 patients were randomly assigned to rilotumumab plus epirubicin, cisplatin, and capecitabine (rilotumumab group; n=304) or placebo plus epirubicin, cisplatin, and capecitabine (placebo group; n=305). Study treatment was stopped early after an independent data monitoring committee found a higher number of deaths in the rilotumumab group than in the placebo group; all patients in the rilotumumab group subsequently discontinued all study treatment. Median follow-up was 7·7 months (IQR 3·6-12·0) for patients in the rilotumumab group and 9·4 months (5·3-13·1) for patients in the placebo group. Median overall survival was 8·8 months (95% CI 7·7-10·2) in the rilotumumab group compared with 10·7 months (9·6-12·4) in the placebo group (stratified hazard ratio 1·34, 95% CI 1·10-1·63; p=0·003). The most common grade 3 or worse adverse events in the rilotumumab and placebo groups were neutropenia (86 [29%] of 298 patients vs 97 [32%] of 299 patients), anaemia (37 [12%] vs 43 [14%]), and fatigue (30 [10%] vs 35 [12%]). The frequency of serious adverse events was similar in the rilotumumab and placebo groups (142 [48%] vs 149 [50%]). More deaths due to adverse events occurred in the rilotumumab group than the placebo group (42 [14%] vs 31 [10%]). In the rilotumumab group, 33 (11%) of 298 patients had fatal adverse events due to disease progression, and nine (3%) had fatal events not due to disease progression. In the placebo group, 23 (8%) of 299 patients had fatal adverse events due to disease progression, and eight (3%) had fatal events not due to disease progression.

INTERPRETATION

Ligand-blocking inhibition of the MET pathway with rilotumumab is not effective in improving clinical outcomes in patients with MET-positive gastric or gastro-oesophageal adenocarcinoma.

FUNDING

Amgen.

Tumor Inhibitory Effect of IRCR201, a Novel Cross-Reactive c-Met Antibody Targeting the PSI Domain

Hepatocyte growth factor receptor (HGFR, c-Met) is an essential member of the receptor tyrosine kinase (RTK) family that is often dysregulated during tumor progression, driving a malignant phenotypic state and modulating important cellular functions including tumor growth, invasion, metastasis, and angiogenesis, providing a strong rationale for targeting HGF/c-Met signaling axis in cancer therapy. Based on its protumorigenic potentials, we developed IRCR201, a potent antagonistic antibody targeting the plexin-semaphorin-integrin (PSI) domain of c-Met, using synthetic human antibody phage libraries. We characterized and evaluated the biochemical properties and tumor inhibitory effect of IRCR201 in vitro and in vivo. IRCR201 is a novel fully-human bivalent therapeutic antibody that exhibits cross-reactivity against both human and mouse c-Met proteins with high affinity and specificity. IRCR201 displayed low agonist activity and rapidly depleted total c-Met protein via the lysosomal degradation pathway, inhibiting c-Met-dependent downstream activation and attenuating cellular proliferation in various c-Met-expressing cancer cells. In vivo tumor xenograft models also demonstrated the superior tumor inhibitory responsiveness of IRCR201. Taken together, IRCR201 provides a promising therapeutic agent for c-Met-positive cancer patients through suppressing the c-Met signaling pathway and tumor growth.

Characterization and structural determination of a new anti-MET function-blocking antibody with binding epitope distinct from the ligand binding domain

The growth and motility factor Hepatocyte Growth Factor/Scatter Factor (HGF/SF) and its receptor, the product of the MET proto-oncogene, promote invasion and metastasis of tumor cells and have been considered potential targets for cancer therapy. We generated a new Met-blocking antibody which binds outside the ligand-binding site, and determined the crystal structure of the Fab in complex with its target, which identifies the binding site as the Met Ig1 domain. The antibody, 107_A07, inhibited HGF/SF-induced cell migration and proliferation in vitro and inhibited growth of tumor xenografts in vivo. In biochemical assays, 107_A07 competes with both HGF/SF and its truncated splice variant NK1 for MET binding, despite the location of the antibody epitope on a domain (Ig1) not reported to bind NK1 or HGF/SF. Overlay of the Fab-MET crystal structure with the InternalinB-MET crystal structure shows that the 107_A07 Fab comes into close proximity with the HGF/SF-binding SEMA domain when MET is in the “compact”, InternalinB-bound conformation, but not when MET is in the “open” conformation. These findings provide further support for the importance of the “compact” conformation of the MET extracellular domain, and the relevance of this conformation to HGF/SF binding and signaling.

A Review of Anti-Angiogenic Targets for Monoclonal Antibody Cancer Therapy

Tumor angiogenesis is a key event that governs tumor progression and metastasis. It is controlled by the complicated and coordinated actions of pro-angiogenic factors and their receptors that become upregulated during tumorigenesis. Over the past several decades, vascular endothelial growth factor (VEGF) signaling has been identified as a central axis in tumor angiogenesis. The remarkable advent of recombinant antibody technology has led to the development of bevacizumab, a humanized antibody that targets VEGF and is a leading clinical therapy to suppress tumor angiogenesis. However, despite the clinical efficacy of bevacizumab, its significant side effects and drug resistance have raised concerns necessitating the identification of novel drug targets and development of novel therapeutics to combat tumor angiogenesis. This review will highlight the role and relevance of VEGF and other potential therapeutic targets and their receptors in angiogenesis. Simultaneously, we will also cover the current status of monoclonal antibodies being developed to target these candidates for cancer therapy.

A "Prozone-Like" Effect Influences the Efficacy of the Monoclonal Antibody ABT-700 against the Hepatocyte Growth Factor Receptor

ABT-700 is a therapeutic antibody against the hepatocyte growth factor receptor (MET). At doses or regimens that lead to exposures exceeding optimum in vivo, the efficacy of ABT-700 is unexpectedly reduced. We hypothesized that this reduction in efficacy was due to a "prozone-like" effect in vivo. A prozone-like effect, which is a reduction in efficacy beyond optimum exposure, is caused due a mechanism similar to the generation of false negative flocculation tests by excessive antibody titres. In vitro, we demonstrate that at higher ABT-700 concentrations, this "prozone-like" effect is mediated by a progressive conversion from bivalent to ineffective monovalent binding of the antibody. In vivo, the efficacy of ABT-700 is dependent on an optimum range of exposure as well. Our data suggest that the "prozone-like" effect is operative and independent of target expression. ABT-700 dose, regimen, exposure, and tumor burden are interdependent variables influencing the "prozone-like" effect and mediating and in vivo efficacy. By optimization of dosage and regimen we demonstrate that the "prozone-like" effect can be alleviated and ABT-700 efficacy at varying tumor loads can be further extended in combination with cisplatin. Our results suggest that optimization of exposure taking tumor burden into account may alleviate "prozone-like" effects without compromising efficacy.

Hepatocyte Growth Factor/c-Met Signaling in Head and Neck Cancer and Implications for Treatment

Aberrant signaling of the hepatocyte growth factor (HGF)/c-Met pathway has been identified as a promoter of tumorigenesis in several tumor types including head and neck squamous cell carcinoma (HNSCC). Despite a relatively low c-Met mutation frequency, overexpression of HGF and its receptor c-Met has been observed in more than 80% of HNSCC tumors, with preclinical and clinical studies linking overexpression with cellular proliferation, invasion, migration, and poor prognosis. c-Met is activated by HGF through a paracrine mechanism to promote cellular morphogenesis enabling cells to acquire mesenchymal phenotypes in part through the epithelial-mesenchymal transition, contributing to metastasis. The HGF/c-Met pathway may also act as a resistance mechanism against epidermal growth factor receptor (EGFR) inhibition in advanced HNSCC. Furthermore, with the identification of a biologically distinct subset of HNSCC tumors acquired from human papillomavirus (HPV) infection that generally portends a good prognosis, high expression of HGF or c-Met in HPV-negative tumors has been associated with worse prognosis. Dysregulated HGF/c-Met signaling results in an aggressive HNSCC phenotype which has led to clinical investigations for targeted inhibition of this pathway. In this review, HGF/c-Met signaling, pathway alterations, associations with clinical outcomes, and preclinical and clinical therapeutic strategies for targeting HGF/c-Met signaling in HNSCC are discussed.

Assessment of pharmacokinetic interaction between rilotumumab and epirubicin, cisplatin and capecitabine (ECX) in a Phase 3 study in gastric cancer

AIMS

Rilotumumab is a fully human monoclonal antibody investigated for the treatment of MET-positive gastric cancer. The aim of this study was to evaluate the potential pharmacokinetic (PK)-based drug-drug interaction (DDI) between rilotumumab and epirubicin (E), cisplatin(C) and capecitabine (X).

METHODS

This was a Phase 3 double-blind, placebo-controlled study, in which rilotumumab, epirubicin and cisplatin were administered intravenously at 15 mg kg^-1 , 50 mg m^-2 , and 60 mg m^-2 Q3W, respectively, while capecitabine was given orally at 625 mg m^-2 twice daily. Rilotumumab PK samples were taken at pre-dose and at the end-of-infusion from all patients in cycles 1, 3, 5 and 7. ECX PK samples were taken in cycle 3 from patients who participated in the intensive PK assessment. ECX PK was assessed by non-compartmental (NCA) analyses and PK parameters were compared between two arms. Rilotumumab PK was assessed by comparing the observed rilotumumab serum concentrations with model-predicted concentrations using a population PK model developed from previous Phase 1 and Phase 2 studies.

RESULTS

The study enrolled 609 patients. ECX plasma concentrations in the presence and absence of rilotumumab were similar, as demonstrated by the geometric mean ratios for C_max and AUC, which were close to 1.0, suggesting ECX PK was not affected by co-administration of rilotumumab. The observed rilotumumab serum concentrations were similar to the values predicted by population PK modelling on the basis of a prediction-corrected visual predictive check, indicating rilotumumab exposure was not affected by co-administration of ECX.

CONCLUSIONS

The results suggest lack of PK-based DDI between rilotumumab and ECX.

Incomplete target neutralization by the anti-cancer antibody rilotumumab

The antibody rilotumumab, which has been tested in multiple Phase 2 and Phase 3 trials, has been reported to neutralize hepatocyte growth factor (HGF), the ligand for the oncogene MET. However, we report that rilotumumab does not prevent HGF from directly binding to MET on conventional and primary patient-derived human gliomasphere lines, a trait driven by the HGF α-chain, which remains free to engage cell-surface glycosaminoglycans and the receptor MET. This binding induces MET phosphorylation, initiates robust AKT and ERK signaling and potentiates biological effects such as cell scattering. This partial antagonism was highly exacerbated in the presence of activated epidermal growth factor receptor, which is common in several cancers. Hence, we confirm that rilotumumab is only a partial antagonist of HGF activity, a finding that has considerable implications for the therapeutic use of rilotumumab.

A novel antagonist anti-cMet antibody with antitumor activities targeting both ligand-dependent and ligand-independent c-Met receptors

c-Met is a prototypic member of a sub-family of RTKs. Inappropriate c-Met activation plays a crucial role in tumor formation, proliferation and metastasis. Using a key c-Met dimerization assay, a set of 12 murine whole IgG1 monoclonal antibodies was selected and a lead candidate, m224G11, was humanized by CDR-grafting and engineered to generate a divalent full antagonist humanized IgG1 antibody, hz224G11. Neither m224G11 nor hz224G11 bind to the murine c-Met receptor. Their antitumor activity was investigated in vitro in a set of experiments consistent with the reported pleiotropic effects mediated by c-Met and, in vivo, using several human tumor xenograft models. Both m224G11 and hz224G11 exhibited nanomolar affinities for the receptor and inhibited HGF binding, c-Met phosphorylation, and receptor dimerization in a similar fashion, resulting in a profound inhibition of all c-Met functions in vitro. These effects were presumably responsible for the inhibition of c-Met's major functions including cell proliferation, migration, invasion scattering, morphogenesis and angiogenesis. In addition to these in vitro properties, hz224G11 dramatically inhibits the growth of autocrine, partially autophosphorylated and c-Met amplified cell lines in vivo. Pharmacological studies performed on Hs746T gastric cancer xenografts demonstrate that hz224G11 strongly downregulates c-Met expression and phosphorylation. It also decreases the tumor mitotic index (Ki67) and induces apoptosis. Taken together, the in vitro and in vivo data suggest that hz224G11 is a promising candidate for the treatment of tumors. This antibody, now known as ABT-700 and currently in Phase I clinical trials, may provide a novel therapeutic approach to c-Met-expressing cancers.

Biomarker development in MET-targeted therapy

Activation of the MET receptor tyrosine kinase by its ligand, hepatocyte growth factor (HGF), has been implicated in a variety of cellular processes, including cell proliferation, survival, migration, motility and invasion, all of which may be enhanced in human cancers. Aberrantly activated MET/HGF signaling correlates with tumorigenesis and metastasis, and is regarded as a robust target for the development of novel anti-cancer treatments. Various clinical trials were conducted to evaluate the safety and efficacy of selective HGF/MET inhibitors in cancer patients. There is currently no optimal or standardized method for accurate and reliable assessment of MET levels, or other biomarkers that are predictive of the patient response to MET-targeted therapeutics. In this review, we discuss the importance of accurate HGF/MET signal detection as a predictive biomarker to guide patient selection for clinical trials of MET-targeted therapies in human cancers.

Prognostic impact of tumor MET expression among patients with stage IV gastric cancer: a Danish cohort study

PURPOSE

We aimed to investigate the prevalence and prognostic impact of tumor mesenchymal epithelial transition factor (MET) expression in stage IV gastric cancers in a real-world clinical setting because existing evidence is sparse.

METHODS

The study included archived cancer specimens from 103 stage IV gastric cancer patients (2003-2010). We analyzed MET-protein expression by immunohistochemistry (MET-positive if ≥25% of tumor cells showed MET expression). We calculated overall survival using the Kaplan-Meier method and hazard ratios comparing mortality among MET-positive and MET-negative patients using Cox regression adjusted for age, gender, and comorbidity.

RESULTS

We found that 62.1% (95% confidence interval, 52.0-71.5) of patients had MET-positive tumors. Median survival was lower among patients with MET-positive tumors (3.5 months) than among patients with MET-negative tumors (9.6 months), corresponding to an adjusted hazard ratio of 2.2 (95% confidence interval, 1.3-3.7).

CONCLUSIONS

Tumor MET expression is prevalent and has substantial prognostic impact in stage IV gastric cancer patients.

In Vitro and In Vivo Activity of AMG 337, a Potent and Selective MET Kinase Inhibitor, in MET-Dependent Cancer Models

The MET receptor tyrosine kinase is involved in cell growth, survival, and invasion. Clinical studies with small molecule MET inhibitors have shown the role of biomarkers in identifying patients most likely to benefit from MET-targeted therapy. AMG 337 is an oral, small molecule, ATP-competitive, highly selective inhibitor of the MET receptor. Herein, we describe AMG 337 preclinical activity and mechanism of action in MET-dependent tumor models. These studies suggest MET is the only therapeutic target for AMG 337. In an unbiased tumor cell line proliferation screen (260 cell lines), a closely related analogue of AMG 337, Compound 5, exhibited activity in 2 of 260 cell lines; both were MET-amplified. Additional studies examining the effects of AMG 337 on the proliferation of a limited panel of cell lines with varying MET copy numbers revealed that high-level focal MET amplification (>12 copies) was required to confer MET oncogene addiction and AMG 337 sensitivity. One MET-amplified cell line, H1573 (>12 copies), was AMG 337 insensitive, possibly because of a downstream G12A KRAS mutation. Mechanism-of-action studies in sensitive MET-amplified cell lines demonstrated that AMG 337 inhibited MET and adaptor protein Gab-1 phosphorylation, subsequently blocking the downstream PI3K and MAPK pathways. AMG 337 exhibited potency in pharmacodynamic assays evaluating MET signaling in tumor xenograft models; >90% inhibition of Gab-1 phosphorylation was observed at 0.75 mg/kg. These findings describe the preclinical activity and mechanism of action of AMG 337 in MET-dependent tumor models and indicate its potential as a novel therapeutic for the treatment of MET-dependent tumors. Mol Cancer Ther; 15(7); 1568-79. ©2016 AACR.

Targeting the MET Pathway in Gastric and Oesophageal Cancers: Refining the Optimal Approach

Gastric and oesophageal cancers are a major cause of global cancer-related morbidity and mortality. Improvements in treatment for locoregional and metastatic gastric and oesophageal cancer have been incremental and the overall prognosis remains poor. Increasingly, molecular classification has identified recurrent, therapeutically relevant, somatic alterations in gastroesophageal malignancies. However, other than ERBB2 amplification, molecularly directed therapies have not translated to improved survival. Amplification of the receptor tyrosine kinase MET is found in about 5% of gastroesophageal cancers and represents an oncogenic driver and therapeutic target. Small series have shown activity of MET-directed tyrosine kinase inhibitors, but the clinical benefit of anti-MET antibodies has been disappointing. Here we discuss the MET pathway in gastroesophageal cancers, the clinical data for MET small molecule tyrosine kinase inhibitors, anti-MET antibodies and future clinical directions for targeting MET in gastric and oesophageal cancers. To our knowledge, this is the most comprehensive review of the clinical experience with MET-directed therapies in gastric and oesophageal cancers.

Novel c-Met inhibitor suppresses the growth of c-Met-addicted gastric cancer cells

BACKGROUND

c-Met signaling has been implicated in oncogenesis especially in cells with c-met gene amplification. Since 20 % of gastric cancer patients show high level of c-Met expression, c-Met has been identified as a good candidate for targeted therapy in gastric cancer. Herein, we report our newly synthesized c-Met inhibitor by showing its efficacy both in vitro and in vivo.

METHODS

Compounds with both triazolopyrazine and pyridoxazine scaffolds were synthesized and tested using HTRF c-Met kinase assay. We performed cytotoxic assay, cellular phosphorylation assay, and cell cycle assay to investigate the cellular inhibitory mechanism of our compounds. We also conducted mouse xenograft assay to see efficacy in vivo.

RESULTS

KRC-00509 and KRC-00715 were selected as excellent c-Met inhibitors through biochemical assay, and exhibited to be exclusively selective to c-Met by kinase panel assay. Cytotoxic assays using 18 gastric cancer cell lines showed our c-Met inhibitors suppressed specifically the growth of c-Met overexpressed cell lines, not that of c-Met low expressed cell lines, by inducing G1/S arrest. In c-met amplified cell lines, c-Met inhibitors reduced the downstream signals including Akt and Erk as well as c-Met activity. In vivo Hs746T xenograft assay showed KRC-00715 reduced the tumor size significantly.

CONCLUSIONS

Our in vitro and in vivo data suggest KRC-00715 is a potent and highly selective c-Met inhibitor which may have therapeutic potential in gastric tumor with c-Met overexpression.

Anti-vascular therapies in ovarian cancer: moving beyond anti-VEGF approaches

Resistance to chemotherapy is among the most important issues in the management of ovarian cancer. Unlike cancer cells, which are heterogeneous as a result of remarkable genetic instability, stromal cells are considered relatively homogeneous. Thus, targeting the tumor microenvironment is an attractive approach for cancer therapy. Arguably, anti-vascular endothelial growth factor (anti-VEGF) therapies hold great promise, but their efficacy has been modest, likely owing to redundant and complementary angiogenic pathways. Components of platelet-derived growth factor (PDGF), fibroblast growth factor (FGF), epidermal growth factor (EGF), and other pathways may compensate for VEGF blockade and allow angiogenesis to occur despite anti-VEGF treatment. In addition, hypoxia induced by anti-angiogenesis therapy modifies signaling pathways in tumor and stromal cells, which induces resistance to therapy. Because of tumor cell heterogeneity and angiogenic pathway redundancy, combining cytotoxic and targeted therapies or combining therapies targeting different pathways can potentially overcome resistance. Although targeted therapy is showing promise, much more work is needed to maximize its impact, including the discovery of new targets and identification of individuals most likely to benefit from such therapies.

Tissue invasion and metastasis: Molecular, biological and clinical perspectives

Cancer is a key health issue across the world, causing substantial patient morbidity and mortality. Patient prognosis is tightly linked with metastatic dissemination of the disease to distant sites, with metastatic diseases accounting for a vast percentage of cancer patient mortality. While advances in this area have been made, the process of cancer metastasis and the factors governing cancer spread and establishment at secondary locations is still poorly understood. The current article summarizes recent progress in this area of research, both in the understanding of the underlying biological processes and in the therapeutic strategies for the management of metastasis. This review lists the disruption of E-cadherin and tight junctions, key signaling pathways, including urokinase type plasminogen activator (uPA), phosphatidylinositol 3-kinase/v-akt murine thymoma viral oncogene (PI3K/AKT), focal adhesion kinase (FAK), β-catenin/zinc finger E-box binding homeobox 1 (ZEB-1) and transforming growth factor beta (TGF-β), together with inactivation of activator protein-1 (AP-1) and suppression of matrix metalloproteinase-9 (MMP-9) activity as key targets and the use of phytochemicals, or natural products, such as those from Agaricus blazei, Albatrellus confluens, Cordyceps militaris, Ganoderma lucidum, Poria cocos and Silybum marianum, together with diet derived fatty acids gamma linolenic acid (GLA) and eicosapentanoic acid (EPA) and inhibitory compounds as useful approaches to target tissue invasion and metastasis as well as other hallmark areas of cancer. Together, these strategies could represent new, inexpensive, low toxicity strategies to aid in the management of cancer metastasis as well as having holistic effects against other cancer hallmarks.

The HGF inhibitory peptide HGP-1 displays promising in vitro and in vivo efficacy for targeted cancer therapy

HGF/MET pathway mediates cancer initiation and development. Thus, inhibition on HGF-initiated MET signaling pathway would provide a new approach to cancer targeted therapeutics. In our study, we identified a targeting peptide candidate binding to HGF which was named HGF binding peptide-1 (HGP-1) via bacterial surface display methods coupled with fluorescence-activated cell sorting (FACS). HGP-1 showed the moderate affinity when determined with surface plasmon resonance (SPR) technique and high specificity in binding to HGF while assessed by fluorescence-based ELISA assay. The results from MTT and in vitro migration assay indicated that HGF-dependent cell proliferation and migration could be inhibited by HGP-1. In vivo administration of HGP-1 led to an effective inhibitory effect on tumor growth in A549 tumor xenograft models. Moreover, findings from Western Blots revealed that HGP-1 could down-regulated the phosphorylation levels of MET and ERK1/2 initiated by HGF, which suggested that HGP-1 could disrupt the activation of HGF/MET signaling to influence the cell activity. All the data highlighted the potential of HGP-1 to be a potent inhibitor for HGF/MET signaling.

Expression array analysis of the hepatocyte growth factor invasive program

Signaling by human hepatocyte growth factor (hHGF) via its cell surface receptor (MET) drives mitogenesis, motogenesis and morphogenesis in a wide spectrum of target cell types and embryologic, developmental and homeostatic contexts. Oncogenic pathway activation also contributes to tumorigenesis and cancer progression, including tumor angiogenesis and metastasis, in several prevalent malignancies. The HGF gene encodes full-length hHGF and two truncated isoforms known as NK1 and NK2. NK1 induces all three HGF activities at modestly reduced potency, whereas NK2 stimulates only motogenesis and enhances HGF-driven tumor metastasis in transgenic mice. Prior studies have shown that mouse HGF (mHGF) also binds with high affinity to human MET. Here we show that, like NK2, mHGF stimulates cell motility, invasion and spontaneous metastasis of PC3M human prostate adenocarcinoma cells in mice through human MET. To identify target genes and signaling pathways associated with motogenic and metastatic HGF signaling, i.e., the HGF invasive program, gene expression profiling was performed using PC3M cells treated with hHGF, NK2 or mHGF. Results obtained using Ingenuity Pathway Analysis software showed significant overlap with networks and pathways involved in cell movement and metastasis. Interrogating The Cancer Genome Atlas project also identified a subset of 23 gene expression changes in PC3M with a strong tendency for co-occurrence in prostate cancer patients that were associated with significantly decreased disease-free survival.

Hypoxia-inducible factor-1 and associated upstream and downstream proteins in the pathophysiology and management of glioblastoma

Glioblastoma multiforme (GBM) is a highly aggressive brain tumor with an exceptionally poor patient outcome despite aggressive therapy including surgery, radiation, and chemotherapy. This aggressive phenotype may be associated with intratumoral hypoxia, which probably plays a key role in GBM tumor growth, development, and angiogenesis. A key regulator of cellular response to hypoxia is the protein hypoxia-inducible factor–1 (HIF-1). An examination of upstream hypoxic and nonhypoxic regulation of HIF-1 as well as a review of the downstream HIF-1– regulated proteins may provide further insight into the role of this transcription factor in GBM pathophysiology. Recent insights into upstream regulators that intimately interact with HIF-1 could provide potential therapeutic targets for treatment of this tumor. The same is potentially true for HIF-1–mediated pathways of glycolysis-, angiogenesis-, and invasion-promoting proteins. Thus, an understanding of the relationship between HIF-1, its upstream protein regulators, and its downstream transcribed genes in GBM pathogenesis could provide future treatment options for the care of patients with these tumors.

A novel rabbit anti-hepatocyte growth factor monoclonal neutralizing antibody inhibits tumor growth in prostate cancer cells and mouse xenografts

The hepatocyte growth factor and its receptor c-Met are correlated with castration-resistance in prostate cancer. Although HGF has been considered as an attractive target for therapeutic antibodies, the lack of cross-reactivity of monoclonal antibodies with human/mouse HGFs is a major obstacle in preclinical developments. We generated a panel of anti-HGF RabMAbs either blocking HGF/c-Met interaction or inhibiting c-Met phosphorylation. We selected one RabMAb with mouse cross-reactivity and demonstrated that it blocked HGF-stimulated downstream activation in PC-3 and DU145 cells. Anti-HGF RabMAb inhibited not only the growth of PC-3 cells but also HGF-dependent proliferation in HUVECs. We further demonstrated the efficacy and potency of the anti-HGF RabMAb in tumor xenograft mice models. Through these in vitro and in vivo experiments, we explored a novel therapeutic antibody for advanced prostate cancer.

Pharmacokinetics and pharmacodynamics of rilotumumab: a decade of experience in preclinical and clinical cancer research

Rilotumumab is a fully human monoclonal antibody against hepatocyte growth factor, the only known ligand of the MET receptor. Over the last decade, rilotumumab has been extensively tested in preclinical studies and in clinical studies in a variety of cancer types. In this review, we examine the pharmacokinetic and pharmacodynamic data that have been collected in the rilotumumab programme to date, and discuss retrospectively how the knowledge acquired in this programme can be applied to a number of key issues in oncology drug development, including: (i) using preclinical data to inform first-in-human study design; (ii) the role of biomarkers in the identification of a target patient population; (iii) the potential for drug interactions between therapeutic proteins and other anticancer agents; and (iv) pharmacokinetic and pharmacodynamic considerations in phase 3 study design.

Immunoprofile of c-MET/PI3K signaling in human salivary gland tumors

OBJECTIVE

The aim of this study was to analyze the expression pattern of proteins in the HGF/c-MET/PI3K signaling pathway in salivary gland tumors (SGTs) and to correlate the findings with the proliferative index and clinical parameters.

STUDY DESIGN

We assembled tissue microarrays (TMAs) of 108 cases of SGTs, including 69 cases of pleomorphic adenoma (PA), 24 cases of adenoid cystic carcinoma (AdCC), and 15 cases of mucoepidermoid carcinoma (MEC). An immunohistochemical analysis of hepatocyte growth factor (HGF), MET phosphorylation (p-MET), protein kinase B (AKT) phosphorylation (p-AKT), and Ki-67 proteins was performed.

RESULTS

Benign and malignant SGTs presented similar scores of HGF-positive cells (P = .36), whereas, malignant SGTs exhibited higher levels of p-MET (P = .001) and p-AKT (P = .001) than benign SGTs. No correlation of HGF, p-MET, or p-AKT expression was observed with clinical parameters. PA had a lower proliferative index than either AdCC (P = .001) or MEC (P = .001).

CONCLUSIONS

The salivary gland carcinomas exhibited increased activation of the HGF pathway, as evidenced by the phosphorylation of the MET receptor, and increased activation of the PI3K pathway, as indicated by p-AKT. These data suggest that the HGF/c-MET/PI3K signaling pathway is active in SGTs, especially in malignant neoplasms.

Recent Progress and Advances in HGF/MET-Targeted Therapeutic Agents for Cancer Treatment

The hepatocyte growth factor (HGF): MET axis is a ligand-mediated receptor tyrosine kinase pathway that is involved in multiple cellular functions, including proliferation, survival, motility, and morphogenesis. Aberrancy in the HGF/MET pathway has been reported in multiple tumor types and is associated with tumor stage and prognosis. Thus, targeting the HGF/MET pathway has become a potential therapeutic strategy in oncology development in the last two decades. A number of novel therapeutic agents-either as therapeutic proteins or small molecules that target the HGF/MET pathway-have been tested in patients with different tumor types in clinical studies. In this review, recent progress in HGF/MET pathway-targeted therapy for cancer treatment, the therapeutic potential of HGF/MET-targeted agents, and challenges in the development of such agents will be discussed.

Rilotumumab exposure-response relationship in patients with advanced or metastatic gastric cancer

PURPOSE

Rilotumumab is an investigational, fully human monoclonal antibody to hepatocyte growth factor. In a randomized phase II study, trends toward improved survival were observed with rilotumumab (7.5 or 15 mg/kg) plus epirubicin, cisplatin, and capecitabine (ECX) versus placebo plus ECX in gastric/gastroesophageal junction (GEJ) cancer patients, especially in MET-positive patients. Here, we quantitatively characterized the longitudinal exposure-response [tumor growth (TG) and overall survival (OS)] relationship for rilotumumab.

EXPERIMENTAL DESIGN

Rilotumumab concentrations, tumor sizes, and survival time from the phase II study were pooled to develop a longitudinal exposure versus TG model and parametric OS model that explored predictive/prognostic/treatment effects (MET expression, rilotumumab exposure, relative tumor size). Model evaluation included visual predictive checks, nonparametric bootstrap, and normalized prediction distribution errors. Simulations were undertaken to predict the relationship between rilotumumab dose and OS.

RESULTS

Rilotumumab exhibited linear time-independent pharmacokinetics not affected by MET expression. The TG model adequately described tumor size across arms. A Weibull distribution best described OS. Rilotumumab exposure and change in tumor size from baseline at week 24 were predictive of OS. MET-positive patients showed shorter survival and responded better to rilotumumab than MET-negative patients. Simulations predicted a median (95% confidence interval) HR of 0.38 (0.18-0.60) in MET-positive patients treated with 15 mg/kg rilotumumab Q3W.

CONCLUSIONS

Rilotumumab plus ECX demonstrated concentration-dependent effects on OS, influenced by MET expression, and tumor size in gastric/GEJ cancer patients. These findings support the phase II testing of rilotumumab 15 mg/kg every 3 weeks in MET-positive gastric/GEJ cancer (RILOMET-1; NCT01697072).

Exposure-response analysis of rilotumumab in gastric cancer: the role of tumour MET expression

BACKGROUND

Rilotumumab, an investigational, monoclonal antibody, inhibits MET-mediated signalling. In a randomized phase 2 trial of rilotumumab±epirubicin/cisplatin/capecitabine in gastric or oesophagogastric junction cancer, patients receiving rilotumumab showed a trend towards improved survival, especially in MET-positive patients, but no clear dose-response relationship was observed. Exposure-response and biomarker analyses were used for dose selection and to differentiate patient subpopulations that may benefit most from treatment. Here, we analyse rilotumumab exposure-survival and exposure-safety and the impact of MET expression on these relationships.

METHODS

Individual rilotumumab exposure parameters were generated using population pharmacokinetic modelling. Relationships among rilotumumab dose (7.5 and 15 mg kg(-1)), exposure, and clinical outcomes (progression-free survival (PFS) and overall survival (OS)) were evaluated with Cox regression models and Kaplan-Meier plots. MET status and other baseline covariates were evaluated in subgroup and multivariate analyses. Treatment-emergent adverse events were summarised by exposure.

RESULTS

Among MET-positive patients, higher rilotumumab exposure, vs placebo and low exposure, was associated with improved median PFS (80% CI: 7.0 (5.7-9.7) vs 4.4 (2.9-4.9) and 5.5 (4.2-6.8) months) and OS (13.4 (10.6-18.6) vs 5.7 (4.7-10.2) and 8.1 (6.9-11.1) months) without increased toxicity. No rilotumumab benefit was seen among MET-negative patients.

CONCLUSIONS

Rilotumumab had an exposure-dependent treatment effect in patients with MET-positive gastric or oesophagogastric junction cancer.

Targeting the epithelial to mesenchymal transition in glioblastoma: the emerging role of MET signaling

Glioblastoma multiforme (GBM) is the most common human primary brain malignancy and has a dismal prognosis. Aggressive treatments using maximal surgical resection, radiotherapy, and temozolomide result in median survival of only 14.6 months in patients with GBM. Numerous clinical approaches using small molecule inhibitors have shown disappointing results because of the genetic heterogeneity of GBM. The epithelial to mesenchymal transition (EMT) is a crucial biological process occurring in the early development stages of many species. However, cancer cells often obtain the ability to invade and metastasize through the EMT, which triggers the scattering of cells. The hepatocyte growth factor (HGF)/MET signaling pathway is indicative of the EMT during both embryogenesis and the invasive growth of tumors, because HGF potently induces mesenchymal transition in epithelial-driven cells. Activation of MET signaling or co-overexpression of HGF and MET frequently represents aggressive growth and poor prognosis of various cancers, including GBM. Thus, efforts to treat cancers by inhibiting MET signaling using neutralizing antibodies or small molecule inhibitors have progressed during the last decade. In this review, we discuss HGF/MET signaling in the development of diseases, including cancers, as well as updates on MET inhibition therapy.

Targeting met mediated epithelial-mesenchymal transition in the treatment of breast cancer

Mesenchymal epithelial transition factor receptor (Met) is a receptor tyrosine kinase that plays a critical role in promoting cancer cell malignant progression. Met is activated by its ligand hepatocyte growth factor (HGF). HGF-dependent Met activation plays an important role in stimulating epithelial-mesenchymal transition (EMT) in tumor cells, resulting in increased tumor cell proliferation, survival, motility, angiogenesis, invasion, and metastasis. The HGF/Met axis has thus attracted great interest as a potential target in the development of novel cancer therapies. In an effort to suppress tumor cell malignant progression, efforts have been made to develop agents capable of inhibiting inhibit Met-induced EMT, including specific Met tyrosine kinase inhibitors, HGF antagonists that interfere with HGF binding to Met, and antibodies that prevent Met activation and/or dimerization. Tocotrienols, a subgroup within the vitamin E family of compounds, display potent anticancer activity that results, at least in part, from inhibition of HGF-dependent Met activation and signaling. The present review will provide a brief summary of the increasing importance of the HGF/Met axis as an attractive target for cancer chemotherapy and the role of tocotrienols in suppressing Met activation, signaling and HGF-induced EMT in breast cancer cells. Evidence provided suggests that γ-tocotrienol therapy may afford significant benefit in the treatment of breast cancers characterized by Met dysregulation.

LY2875358, a neutralizing and internalizing anti-MET bivalent antibody, inhibits HGF-dependent and HGF-independent MET activation and tumor growth

PURPOSE

MET, the receptor for hepatocyte growth factor (HGF), has been implicated in driving tumor proliferation and metastasis. High MET expression is correlated with poor prognosis in multiple cancers. Activation of MET can be induced either by HGF-independent mechanisms such as gene amplification, specific genetic mutations, and transcriptional upregulation or by HGF-dependent autocrine or paracrine mechanisms.

EXPERIMENTAL DESIGN/RESULTS

Here, we report on LY2875358, a novel humanized bivalent anti-MET antibody that has high neutralization and internalization activities, resulting in inhibition of both HGF-dependent and HGF-independent MET pathway activation and tumor growth. In contrast to other bivalent MET antibodies, LY2875358 exhibits no functional agonist activity and does not stimulate biologic activities such as cell proliferation, scattering, invasion, tubulogenesis, or apoptosis protection in various HGF-responsive cells and no evidence of inducing proliferation in vivo in a monkey toxicity study. LY2875358 blocks HGF binding to MET and HGF-induced MET phosphorylation and cell proliferation. In contrast to the humanized one-armed 5D5 anti-MET antibody, LY2875358 induces internalization and degradation of MET that inhibits cell proliferation and tumor growth in models where MET is constitutively activated. Moreover, LY2875358 has potent antitumor activity in both HGF-dependent and HGF-independent (MET-amplified) xenograft tumor models. Together, these findings indicate that the mechanism of action of LY2875358 is different from that of the one-armed MET antibody.

CONCLUSIONS

LY2875358 may provide a promising therapeutic strategy for patients whose tumors are driven by both HGF-dependent and HGF-independent MET activation. LY2875358 is currently being investigated in multiple clinical studies.

The Hepatocyte Growth Factor (HGF)/Met Axis: A Neglected Target in the Treatment of Chronic Myeloproliferative Neoplasms?

Met is the receptor of hepatocyte growth factor (HGF), a cytoprotective cytokine. Disturbing the equilibrium between Met and its ligand may lead to inappropriate cell survival, accumulation of genetic abnormalities and eventually, malignancy. Abnormal activation of the HGF/Met axis is established in solid tumours and in chronic haematological malignancies, including myeloma, acute myeloid leukaemia, chronic myelogenous leukaemia (CML), and myeloproliferative neoplasms (MPNs). The molecular mechanisms potentially responsible for the abnormal activation of HGF/Met pathways are described and discussed. Importantly, inCML and in MPNs, the production of HGF is independent of Bcr-Abl and JAK2V617F, the main molecular markers of these diseases. In vitro studies showed that blocking HGF/Met function with neutralizing antibodies or Met inhibitors significantly impairs the growth of JAK2V617F-mutated cells. With personalised medicine and curative treatment in view, blocking activation of HGF/Met could be a useful addition in the treatment of CML and MPNs for those patients with high HGF/MET expression not controlled by current treatments (Bcr-Abl inhibitors in CML; phlebotomy, hydroxurea, JAK inhibitors in MPNs).

Targeting the oncogenic Met receptor by antibodies and gene therapy

The receptor for hepatocyte growth factor (HGF), a tyrosine kinase encoded by the Met oncogene, has a crucial role in cancer growth, invasion and metastasis. It is a validated therapeutic target for 'personalized' treatment of a number of malignancies. Therapeutic tools prompting selective, robust and highly effective Met inhibition potentially represent a major step in the battle against cancer. Antibodies targeting either Met or its ligand HGF, although challenging, demonstrate to be endowed with promising features. Here we briefly review and discuss the state of the art in the field.