Novel therapeutic target for head and neck squamous cell carcinoma: HGF-MET signaling pathway

Head and neck squamous cell carcinoma (HNSCC) represents a devastating type of malignancy characterized by its high incidence of regional and distant metastases at the time of diagnosis. Vital physiological functions in the upper aerodigestive tract are often impaired as a result of the disease and treatment for the disease, giving rise to severe morbidity in patients suffering from this type of cancer. It is crucial to delineate the aberrant growth signaling pathways in HNSCC cells and develop specific target therapies for the disease to improve the treatment outcome. Although the epidermal growth factor receptor pathway has been extensively studied in HNSCC and anti-epidermal growth factor receptor therapy has already shown promise in treating HNSCC in phase III clinical trials, the signaling pathway that accounts for the highly invasive phenotype of HNSCC needs to be defined and also therapeutically targeted. The hepatocyte growth factor-MET signaling pathway has been studied extensively over the past two decades and it is now clear that it plays an important role in mediating invasive growth of many types of cancer. Here, we review comprehensively the evidence on hepatocyte growth factor-MET cascade being a key in the signaling pathway in mediating invasive growth of HNSCC and the potential of this signaling pathway to be a therapeutic target for the treatment of HNSCC.

A phase II study of the efficacy and safety of AMG 102 in patients with metastatic renal cell carcinoma

OBJECTIVE

• To evaluate the efficacy and safety of single-agent AMG 102, an investigational, fully human monoclonal antibody to hepatocyte growth factor/scatter factor (HGF/SF), in renal cell carcinoma (RCC).

PATIENTS AND METHODS

• This open-label phase II study included patients ≥ 18 years old with histologically confirmed, advanced or metastatic RCC (mRCC) and Eastern Cooperative Oncology Group performance status 0 to 2. AMG 102 was administered i.v. at 10 or 20 mg/kg once every 2 weeks. • A two-stage design was used at each dose level and the primary endpoint was objective best confirmed response (by Response Evaluation Criteria in Solid Tumours) at any time.

RESULTS

• Sixty-one patients with mRCC enrolled and received AMG 102 (40 at 10 mg/kg; 21 at 20 mg/kg). Overall, 70.5% were men, median age was 59 years (range, 39 to 84 years), and 92% had received previous anti-vascular endothelial growth factor therapy. RCC histologies were: clear cell (75.4%), papillary (11.5%), chromophobe (4.9%) and unclassified (8.2%). • One confirmed partial response occurred at 10 mg/kg, maintained for over 2.5 years; 26 patients (43%) had stable disease, 10 (16%) for ≥ 32 weeks. The median profression-free survival was 3.7 months at 10 mg/kg and 2.0 months at 20 mg/kg. The commonest adverse events were oedema (45.9%), fatigue (37.7%) and nausea (27.9%). Grade 3 or 4 adverse events occurred in 33% of patients, the most common being oedema (9.8%). • Baseline levels of plasma HGF/SF and soluble c-Met as well as archival-tumour c-Met did not correlate with measures of efficacy.

CONCLUSION

• Single-agent AMG 102 was tolerable, but it is unclear if AMG 102 was growth inhibitory in this population of patients with mRCC.

Novel medical therapeutics in glioblastomas, including targeted molecular therapies, current and future clinical trials

The prognosis for glioblastoma is poor despite optimal therapy with surgery, radiation, and chemotherapy. New therapies that improve survival and quality of life are needed. Research has increased our understanding of the molecular pathways important for gliomagenesis and disease progression. Novel agents have been developed against these targets, including receptor tyrosine kinases, intracellular signaling molecules, epigenetic abnormalities, and tumor vasculature and microenvironment. This article reviews novel therapies for glioblastoma, with an emphasis on targeted agents.

A phase Ib study of AMG 102 in combination with bevacizumab or motesanib in patients with advanced solid tumors

PURPOSE

This phase Ib study evaluated the safety, pharmacokinetics, pharmacodynamics, and antitumor activity of AMG 102, a fully human monoclonal antibody against hepatocyte growth factor/scatter factor (HGF/SF), in combination with bevacizumab or motesanib in patients with advanced solid tumors.

EXPERIMENTAL DESIGN

Patients with treatment-refractory advanced solid tumors were sequentially enrolled into four cohorts (3, 10, or 20 mg/kg AMG 102 plus 10 mg/kg bevacizumab i.v. every 2 weeks, or 3 mg/kg AMG 102 i.v. every 2 weeks plus 75 mg motesanib orally once daily).

RESULTS

Fourteen patients were enrolled and received AMG 102. The combination of AMG 102 with bevacizumab (n = 12) seemed to have acceptable toxicity. The number of patients (n = 2) who received AMG 102 plus motesanib was insufficient to adequately assess safety. No dose-limiting toxicities were reported. Enrollment in the motesanib cohort was suspended because of reports of cholecystitis in other motesanib studies. Treatment-emergent adverse events among patients receiving AMG 102 plus bevacizumab were generally mild and included fatigue (75%), nausea (58%), constipation (42%), and peripheral edema (42%). No anti-AMG 102 antibodies were detected. Bevacizumab did not seem to affect AMG 102 pharmacokinetics. Circulating total HGF/SF increased from baseline throughout the study. Eight of 10 evaluable patients had reductions in tumor dimensions, and stable disease at > or =8, > or =16, and > or =24 weeks occurred in 9, 7, and 4 patients, respectively. Progression-free survival ranged from 7.9 to 121.9 weeks.

CONCLUSIONS

AMG 102 in combination with bevacizumab was well tolerated. Further evaluation of AMG 102 in combination with antiangiogenic agents is warranted.

Selection criteria for c-Met-targeted therapies: emerging evidence for biomarkers

Extensive development of targeted therapies emphasize the critical need for biomarkers and major efforts have been engaged to identify screening, prognostic, stratification and therapy-monitoring markers. One of the challenges in translating preclinical studies into effective clinical therapies remains the accurate identification of a responsive subsets of patients. Studies on trastuzumab demonstrated that patient response could be specifically correlated with the amplification of the Her2 gene. However, for the EGF receptor, it has been more difficult to find the right stratification biomarker and recent data demonstrate that genetic alterations for the EGF receptor have to be considered. Taken together, these data underline the need for a deeper understanding of both targeted receptor and human disease to determine pathways that might be investigated during early clinical trials in order to define relevant biomarkers for patient selection. This article, dealing with the c-Met tyrosine kinase receptor, provides an overview of c-Met alterations observed in cancer and proposes approaches for stratification biomarker selection.

Safety, pharmacokinetics, and pharmacodynamics of AMG 102, a fully human hepatocyte growth factor-neutralizing monoclonal antibody, in a first-in-human study of patients with advanced solid tumors

PURPOSE

The aims were to assess the safety, pharmacokinetics, maximum tolerated dose, and antitumor activity of AMG 102, a fully human hepatocyte growth factor/scatter factor (HGF/SF)-neutralizing monoclonal antibody, in patients with solid tumors.

EXPERIMENTAL DESIGN

Patients (N = 40) with refractory advanced solid tumors were enrolled into six sequential dose-escalation cohorts (0.5, 1, 3, 5, 10, or 20 mg/kg AMG 102 i.v. every 2 weeks) and a dose-expansion cohort (20 mg/kg AMG 102 every 2 weeks). Safety, anti-AMG 102 antibody formation, pharmacokinetics, tumor response, and exploratory biomarkers were assessed.

RESULTS

AMG 102 was well tolerated up to the planned maximum dose of 20 mg/kg, and the maximum tolerated dose was not reached. Treatment-related adverse events were generally mild and included fatigue (13%), constipation (8%), nausea (8%), vomiting (5%), anorexia (5%), myalgia (5%), and hypertension (5%). Two patients experienced dose-limiting toxicities: one patient (0.5 mg/kg cohort) experienced grade 3 hypoxia and grade 3 dyspnea and one patient (1 mg/kg cohort) experienced grade 3 upper gastrointestinal hemorrhage. No anti-AMG 102 antibodies were detected, and AMG 102 had linear pharmacokinetics within the dose range investigated. Sixteen of 23 (70%) evaluable patients had a best response of stable disease with progression-free survival ranging from 7.9 to 40 weeks. Circulating levels of the biomarker HGF/SF (bound and unbound) increased in a dose-dependent manner, whereas soluble c-Met concentrations were generally similar across doses.

CONCLUSIONS

AMG 102 is safe and well tolerated, has a favorable pharmacokinetic profile, and will be further investigated as a monotherapy and in combination with other agents.

The plasticity of oncogene addiction: implications for targeted therapies directed to receptor tyrosine kinases

A common mutation of the epidermal growth factor receptor (EGFR) in glioblastoma multiforme (GBM) is an extracellular truncation known as the de2-7 EGFR (or EGFRvIII). Hepatocyte growth factor (HGF) is the ligand for the receptor tyrosine kinase (RTK) c-Met, and this signaling axis is often active in GBM. The expression of the HGF/c-Met axis or de2-7 EGFR independently enhances GBM growth and invasiveness, particularly through the phosphatidylinositol-3 kinase/pAkt pathway. Using RTK arrays, we show that expression of de2-7 EGFR in U87MG GBM cells leads to the coactivation of several RTKs, including platelet-derived growth factor receptor beta and c-Met. A neutralizing antibody to HGF (AMG102) did not inhibit de2-7 EGFR-mediated activation of c-Met, demonstrating that it is ligand-independent. Therapy for parental U87MG xenografts with AMG 102 resulted in significant inhibition of tumor growth, whereas U87MG.Delta 2-7 xenografts were profoundly resistant. Treatment of U87MG.Delta 2-7 xenografts with panitumumab, an anti-EGFR antibody, only partially inhibited tumor growth as xenografts rapidly reverted to the HGF/c-Met signaling pathway. Cotreatment with panitumumab and AMG 102 prevented this escape leading to significant tumor inhibition through an apoptotic mechanism, consistent with the induction of oncogenic shock. This observation provides a rationale for using panitumumab and AMG 102 in combination for the treatment of GBM patients. These results illustrate that GBM cells can rapidly change the RTK driving their oncogene addiction if the alternate RTK signals through the same downstream pathway. Consequently, inhibition of a dominant oncogene by targeted therapy can alter the hierarchy of RTKs resulting in rapid therapeutic resistance.

Antiangiogenic therapy in malignant gliomas

PURPOSE OF REVIEW

Antiangiogenic drugs are increasingly used in malignant glioma therapy. This article reviews the rationale for targeting angiogenesis in malignant gliomas, summarizes relevant clinical trial results, and discusses promising avenues of investigation in antiangiogenic therapy.

RECENT FINDINGS

Combination therapy with bevacizumab, the humanized monoclonal antibody against vascular endothelial growth factor, and irinotecan has emerged as the treatment of choice for recurrent malignant gliomas, prolonging progression-free survival markedly in comparison with historical controls. Several small molecule tyrosine kinase inhibitors of the vascular endothelial growth factor receptor are under investigation and show promise as well.

SUMMARY

Antiangiogenic treatments are effective and well tolerated options for recurrent malignant glioma. Future studies will determine whether these drugs have a role in first line therapy. Studies are in progress to elucidate mechanisms of resistance and suggest approaches to further improve survival in patients with these challenging tumors.

Role of c-Met in cancer: emphasis on lung cancer

Lung cancer remains the leading cause of cancer death. It is often diagnosed at late stages and is treated systemically with cytotoxic chemotherapy, which is generally ineffective. Research efforts have focused on developing therapies targeted to growth factor receptor pathways, such as epidermal growth factor receptor (EGFR), but the results from clinical trials overall show very small improvements in survival. Research on signaling pathways dysregulated in lung cancer is ongoing, including investigation of the hepatocyte growth factor receptor (HGFR) or c-Met. Protein tyrosine kinases, such as EGFR and c-Met, are a family of oncogenes that regulate important cellular processes, such as differentiation, proliferation, cell cycle, motility, and apoptosis. Hepatocyte growth factor (HGF), a ligand for c-Met, is secreted by mesodermal cells during development. It produces multiple effects upon binding to its receptor (HGFR/c-Met) and regulates proliferation, motility, mitogenesis, and morphogenesis. Studies in cell lines isolated from various tumors show that several intracellular pathways participate in c-Met signaling, including growth factor receptor-bound protein 2 (Grb2), mitogen-activated protein (MAP) kinase, phosphoinositol 3-kinase (PI3K), and phospholipase C-gamma (PLC-gamma). c-Met is overexpressed in many tumors. However, overexpression may not be sufficient to cause increased activity; the receptor needs to be activated. In some cases, the kinases are constitutively active due to mutations in the gene. The cytoskeletal protein paxillin also appears to be activated along with c-Met. Correlative studies from patient tissue samples and cell lines have rendered the same information, indicating that the signaling pathways dysregulated are complex and interdependent. Mutations in human c-Met have been exogenously expressed in Caenorhabditis elegans, which can serve as a model for determining the role of gene mutations in a whole organism. Several inhibitors of c-Met/HGF binding are in development, including some in phase I trials. Their effectiveness in improving cancer outcomes will be determined in the near future.

Novel therapeutic inhibitors of the c-Met signaling pathway in cancer

A wide variety of human malignancies exhibit sustained c-Met stimulation, overexpression, or mutation, including carcinomas of the breast, liver, lung, ovary, kidney, and thyroid. Notably, activating mutations in c-Met have been positively identified in patients with a particular hereditary form of papillary renal cancer, directly implicating c-Met in human tumorigenesis. Aberrant signaling of the c-Met signaling pathway due to dysregulation of the c-Met receptor or overexpression of its ligand, hepatocyte growth factor (HGF), has been associated with an aggressive phenotype. Extensive evidence that c-Met signaling is involved in the progression and spread of several cancers and an enhanced understanding of its role in disease have generated considerable interest in c-Met and HGF as major targets in cancer drug development. This has led to the development of a variety of c-Met pathway antagonists with potential clinical applications. The three main approaches of pathway-selective anticancer drug development have included antagonism of ligand/receptor interaction, inhibition of the tyrosine kinase catalytic activity, and blockade of the receptor/effector interaction. Several c-Met antagonists are now under clinical investigation. Preliminary clinical results of several of these agents, including both monoclonal antibodies and small-molecule tyrosine kinase inhibitors, have been encouraging. Several multitargeted therapies have also been under investigation in the clinic and have demonstrated promise, particularly with regard to tyrosine kinase inhibition.