MET Inhibitors for the Treatment of Gastric Cancer: What's Their Potential?

Gastric cancer remains a disease with a dismal prognosis. Extensive efforts to find targetable disease drivers in gastric cancer were implemented to improve patient outcomes. Beyond anti-HER2 therapy, MET pathway seems to be culprit of cancer invasiveness with MET-overexpressing tumors having poorer prognosis. Tyrosine kinase inhibitors targeting the HGF/MET pathway were studied in MET-positive gastric cancer, but no substantial benefit was proven. Some patients responded in early phase trials but later developed resistance. Others failed to show any benefit at all. Etiologies of resistance may entail inappropriate patient selection with a lack of MET detection standardization, tumor alternative pathways, variable MET amplification, and genetic variation. Optimizing MET detection techniques and better understanding the MET pathway, as well as tumor bypass mechanisms, are an absolute need to devise means to overcome resistance using targeted therapy alone, or in combination with other synergistic agents to improve outcomes of patients with MET-positive GC.

Comprehensive review of targeted therapy for colorectal cancer

Colorectal cancer (CRC) is among the most lethal and prevalent malignancies in the world and was responsible for nearly 881,000 cancer-related deaths in 2018. Surgery and chemotherapy have long been the first choices for cancer patients. However, the prognosis of CRC has never been satisfying, especially for patients with metastatic lesions. Targeted therapy is a new optional approach that has successfully prolonged overall survival for CRC patients. Following successes with the anti-EGFR (epidermal growth factor receptor) agent cetuximab and the anti-angiogenesis agent bevacizumab, new agents blocking different critical pathways as well as immune checkpoints are emerging at an unprecedented rate. Guidelines worldwide are currently updating the recommended targeted drugs on the basis of the increasing number of high-quality clinical trials. This review provides an overview of existing CRC-targeted agents and their underlying mechanisms, as well as a discussion of their limitations and future trends.

Status of Agents Targeting the HGF/c-Met Axis in Lung Cancer

Hepatocyte growth factor (HGF) is the ligand for the tyrosine kinase receptor c-Met (Mesenchymal Epithelial Transition Factor also known as Hepatocyte Growth Factor Receptor, HGFR), a receptor with expression throughout epithelial and endothelial cell types. Activation of c-Met enhances cell proliferation, invasion, survival, angiogenesis, and motility. The c-Met pathway also stimulates tissue repair in normal cells. A body of past research shows that increased levels of HGF and/or overexpression of c-Met are associated with poor prognosis in several solid tumors, including lung cancer, as well as cancers of the head and neck, gastro-intestinal tract, breast, ovary and cervix. The HGF/c-Met signaling network is complex; both ligand-dependent and ligand-independent signaling occur. This article will provide an update on signaling through the HGF/c-Met axis, the mechanism of action of HGF/c-Met inhibitors, the lung cancer patient populations most likely to benefit, and possible mechanisms of resistance to these inhibitors. Although c-Met as a target in non-small cell lung cancer (NSCLC) showed promise based on preclinical data, clinical responses in NSCLC patients have been disappointing in the absence of MET mutation or MET gene amplification. New therapeutics that selectively target c-Met or HGF, or that target c-Met and a wider spectrum of interacting tyrosine kinases, will be discussed.

C-MET inhibitors for advanced non-small cell lung cancer

INTRODUCTION

The role of the c-mesenchymal-epithelial transition factor (c-MET) signaling pathway in tumor progression and invasion has been extensively studied. C-MET inhibitors have shown anti-tumor activity in NSCLC both in preclinical and in clinical trials. However, given the molecular heterogeneity of NSCLC, it is likely that only a specific subset of NSCLC patients will benefit from c-MET inhibitors. Emerging data also suggest that MET inhibitors in combination with EGFR-TKIs (epidermal growth factor receptor tyrosine kinase inhibitors) may have a role in therapy for both EGFR-TKI resistant and EGFR-TKI naïve patients. The challenges ahead are in the identification of the molecular subtypes that benefit most.

AREAS COVERED

This review summarizes the current understanding of c-MET biology in relation to studies evaluating c-MET inhibitors in the treatment of NSCLC.

EXPERT OPINION

MET inhibitors have the potential to benefit subsets of NSCLC patients with specific genetic alterations. Exon-14 skipping mutations appear so far to be the most promising molecular subset that is sensitive to MET inhibitors, whereas overexpression, amplification and point mutations of MET seem more challenging subgroups to target. Combination with other target agents, such as EGFR inhibitors, may represent a promising therapeutic strategy in specific areas (e.g. EGFR-TKI resistance).

Targeting the hepatocyte growth factor/Met pathway in cancer

Hepatocyte growth factor (HGF)-induced activation of its cell surface receptor, the Met tyrosine kinase, drives mitogenesis, motogenesis and morphogenesis in a wide spectrum of target cell types and embryologic, developmental and homeostatic contexts. Typical paracrine HGF/Met signaling is regulated by HGF activation at target cell surfaces, HGF binding-induced receptor activation, internalization and degradation. Despite these controls, HGF/Met signaling contributes to oncogenesis, tumor angiogenesis and invasiveness, and tumor metastasis in many types of cancer, leading to the rapid growth of pathway-targeted anticancer drug development programs. We review here HGF and Met structure and function, basic properties of HGF/Met pathway antagonists now in clinical development, and recent clinical trial results. Presently, the main challenges facing the effective use of HGF/Met-targeted antagonists for cancer treatment include optimal patient selection, diagnostic and pharmacodynamic biomarker development, and the identification and testing of effective therapy combinations. The wealth of basic information, analytical reagents and model systems available regarding normal and oncogenic HGF/Met signaling will continue to be invaluable in meeting these challenges and moving expeditiously toward more effective cancer treatment.

Targeting c-MET in gastrointestinal tumours: rationale, opportunities and challenges. Nat Rev Clin Oncol. 2017;14:562-576. [PMID: 28374784 DOI: 10.1038/nrclinonc.2017.40]

Data from many preclinical studies, including those using cellular models of colorectal, gastric, gastro-oesophageal and gastro-oesophageal junction cancers, indicate that the hepatocyte growth factor (HGF)-hepatocyte growth factor receptor (c-MET) pathway is vital for the growth, survival and invasive potential of gastrointestinal cancers. Following the availability of data from these various studies, and data on c-MET expression as a biomarker that indicates a poor prognosis in patients with gastrointestinal cancer and increased c-MET expression, inhibitors targeting this pathway have entered the clinic in the past decade. However, the design of clinical trials that incorporate the use of HGF/c-MET inhibitors in their most appropriate genetic and molecular context remains crucial. Recognizing and responding to this challenge, the European Commission funded Framework 7 MErCuRIC programme is running a biomarker-enriched clinical trial investigating the efficacy of combined c-MET/MEK inhibition in patients with RAS-mutant or RAS-wild-type metastatic colorectal cancer with aberrant c-MET expression. The design of this trial enables the continued refinement of the predictive biomarker and co-development of companion diagnostics. In this Review, we focus on advances in our understanding of inhibition of the HGF/c-MET pathway in patients with gastro-intestinal cancers, the prominent challenges facing the clinical translation and implementation of agents targeting HGF/c-MET, and discuss the various efforts, and associated obstacles to the discovery and validation of biomarkers that will enable patient stratification in this context.

Progress of antibody-based inhibitors of the HGF-cMET axis in cancer therapy

Dysregulated receptor tyrosine kinase signaling in human cancer cells leads to tumor progression, invasion and metastasis. The receptor tyrosine kinase cMET is frequently overexpressed in cancer tissue, and activation of cMET signaling is related to drug resistance and the processes of carcinogenesis, invasion and metastasis. For that reason, cMET and its ligand, hepatocyte growth factor (HGF), are considered prime targets for the development of anticancer drugs. At least eight anti-cMET and four anti-HGF antibodies have been tested or are being tested in clinical trials. However, to date none of these HGF/cMET inhibitors have shown significant efficacy in clinical trials. Furthermore, no receptor tyrosine kinase inhibitors primarily targeting cMET have been approved. Given that neutralization of HGF or cMET does not cause significant adverse effects, inhibition of the HGF/cMET signaling pathway appears to be safe. In this review, we summarized the completed and ongoing clinical trials testing antibody- or protein-based anticancer drugs targeting cMET and HGF.

Phase I ficlatuzumab monotherapy or with erlotinib for refractory advanced solid tumours and multiple myeloma

BACKGROUND

Ficlatuzumab, a humanised hepatocyte growth factor (HGF) IgG1κ inhibitory monoclonal antibody, was evaluated for recommended phase II dose (RP2D), safety, pharmacokinetics (PKs), antidrug antibody (ADA), pharmacodynamics (PDs) and antitumour activity as monotherapy or combined with erlotinib.

METHODS

Patients with solid tumours received ficlatuzumab 2, 5, 10 or 20 mg kg(-1) intravenously every 2 weeks (q2w). Additional patients were treated at the RP2D erlotinib.

RESULTS

Forty-one patients enrolled at doses ⩽20 mg kg(-1). Common adverse events (AEs) included peripheral oedema, fatigue and nausea. Three patients experienced grade ⩾3 treatment-related hyperkalaemia/hypokalaemia, diarrhoea or fatigue. Best overall response (44%) was stable disease (SD); median duration was 5.5 months (0.4-18.7 months). One patient has been on therapy with SD for >4 years. Pharmacokinetics of ficlatuzumab showed low clearance (0.17-0.26 ml h(-1) kg(-1)), a half-life of 6.8-9.4 days and dose-proportional exposure. Ficlatuzumab/erlotinib had no impact on the PK of either agent. No ADAs were detected. Ficlatuzumab increased serum HGF levels.

CONCLUSIONS

Recommended phase II dose is 20 mg kg(-1) q2w for ficlatuzumab monotherapy or with erlotinib. Preliminary antitumour activity and manageable AEs were observed. Pharmacokinetics were dose-proportional and consistent with other IgG therapeutics. Ficlatuzumab was not immunogenic, and serum HGF was a potential PD marker.

Monoclonal antibodies as therapeutics in human malignancies

ABSTRACT: 

Monoclonal antibodies (mAbs) are a proven effective therapeutic modality in human malignancy. Several mAbs are approved to targets critical in aberrant oncogenic signaling within tumors and their microenvironment. These targets include secreted ligands (e.g., VEGF and HGH), their receptors (e.g., HER2 and VEGFR2), cell surface counter receptors and their receptor-bound ligands (e.g., PD1 and PD1L, respectively). The ability to genetically engineer the structure and/or functions of mAbs has significantly improved their effectiveness. Furthermore, advances in gene expression profiling, proteomics, deep sequencing and deciphering of complex signaling networks have revealed novel therapeutic targets. We review target selection, approved indications and the rationale for mAb utilization in solid and hematologic malignancies. We also discuss novel mAbs in early- and late-phase clinical trials that are likely to change the natural history of disease and improve survival. The future challenge is to design mAb-based novel trial designs for diagnostics and therapeutics for human malignancies.

Onartuzumab (MetMAb): using nonclinical pharmacokinetic and concentration-effect data to support clinical development

PURPOSE

We characterized the pharmacokinetics of onartuzumab (MetMAb) in animals and determined a concentration-effect relationship in tumor-bearing mice to enable estimation of clinical pharmacokinetics and target doses.

EXPERIMENTAL DESIGN

A tumor growth inhibition model was used to estimate tumoristatic concentrations (TSC) in mice. Human pharmacokinetic parameters were projected from pharmacokinetics in cynomolgus monkeys by the species-invariant time method. Monte Carlo simulations predicted the percentage of patients achieving steady-state trough serum concentrations (Ctrough ss) ≥TSC for every 3-week (Q3W) dosing.

RESULTS

Onartuzumab clearance (CL) in the linear dose range was 21.1 and 12.2 mL/d/kg in mice and cynomolgus monkeys with elimination half-life at 6.10 and 3.37 days, respectively. The estimated TSC in KP4 pancreatic xenograft tumor-bearing mice was 15 μg/mL. Projected CL for humans in the linear dose range was 5.74 to 9.36 mL/d/kg with scaling exponents of CL at 0.75 to 0.9. Monte Carlo simulations projected a Q3W dose of 10 to 30 mg/kg to achieve Ctrough ss of 15 μg/mL in 95% or more of patients.

CONCLUSIONS

Onartuzumab pharmacokinetics differed from typical bivalent glycosylated monoclonal antibodies with approximately 2-times faster CL in the linear dose range. Despite this higher CL, xenograft efficacy data supported dose flexibility with Q1W to Q3W dose regimens in the clinical setting with a TSC of 15 μg/mL as the Ctrough ss target. The projected human efficacious dose of 10 to 30 mg/kg Q3W should achieve the target TSC of 15 μg/mL. These data show effective pharmacokinetic/pharmacodynamic modeling to project doses to be tested in the clinic.

MET: a promising anticancer therapeutic target. Nat Rev Clin Oncol. 2012;9:314-326. [PMID: 22566105 DOI: 10.1038/nrclinonc.2012.71]

The MET pathway is dysregulated in many human cancers and promotes tumour growth, invasion and dissemination. Abnormalities in MET signalling have been reported to correlate with poor clinical outcomes and drug resistance in patients with cancer. Thus, MET has emerged as an attractive target for cancer therapy. Several MET inhibitors have been introduced into the clinic, and are currently in all phases of clinical trials. In general, initial results from these studies indicate only a modest benefit in unselected populations. In this Review, we discuss current challenges in developing MET inhibitors--including identification of predictive biomarkers--as well as the most-efficient ways to combine these drugs with other targeted agents or with classic chemotherapy or radiotherapy.

Genetic activation of the MET pathway and prognosis of patients with high-risk, radically resected gastric cancer

PURPOSE

To investigate whether prognosis of patients with high-risk gastric cancer may depend on MET copy number gain (CNG) or an activating truncation within a deoxyadenosine tract element (DATE) in the promoter region of the MET ligand HGF.

PATIENTS AND METHODS

A single-institution cohort of 230 patients with stage II/III gastric cancer was studied. Formalin-fixed paraffin-embedded tumor specimens were used for DNA extraction. Quantitative polymerase chain reaction (qPCR) for MET CNG and sequencing for HGF DATE truncation (< 25 deoxyadenosines instead of 30) were used. Results were analyzed for association with disease-free survival (DFS) and overall survival (OS). To assess the reliability of the qPCR measurement, a random sample of cases was reanalyzed using an alternative assay (fluorescent in situ hybridization [FISH]) with calculation of the intracorrelation coefficient (ICC).

RESULTS

In 216 assessable patients, MET CNG five or more copies and homozygous HGF-truncated DATE occurred in 21 patients (10%) and 30 patients (13%), respectively. Patients with MET CNG five or more copies (MET-positive) showed significantly worse prognosis with multivariate hazard ratio (HR) of 3.02 (95% CI, 1.71 to 5.33; P < .001) for DFS and multivariate HR of 2.91 (95% CI, 1.65 to 5.11; P < .001) for OS. The agreement between qPCR and FISH was high, with ICC = 0.9% (95% CI, 0.81% to 0.95%; the closer the ICC is to 1, the greater is the agreement). HGF-truncated DATE did not show relevant prognostic effect.

CONCLUSION

In this study, qPCR revealed approximately 10% of white patients with gastric cancer harboring MET CNG of five or more copies. This marker was significantly associated with unfavorable prognosis. This information is relevant to the current clinical development of anti-MET compounds.