No abstract

Introduction Under normal conditions, hepatocyte growth factor (HGF)-induced activation of its cell surface receptor, the Met tyrosine kinase (TK), is tightly regulated by paracrine ligand delivery, ligand activation at the target cell surface, and ligand activated receptor internalization and degradation. Despite these controls, HGF/Met signaling contributes to oncogenesis and tumor progression in several cancers and promotes aggressive cellular invasiveness that is strongly linked to tumor metastasis. Area covered The prevalence of HGF/Met pathway activation in human malignancies has driven rapid growth in cancer drug development programs. The authors review Met structure and function, the basic properties of HGF/Met pathway antagonists now in preclinical and clinical development, as well as the latest clinical trial results. Expert opinion Clinical trials with HGF/Met pathway antagonists show that as a class these agents are well tolerated. Although widespread efficacy was not seen in several completed phase 2 studies, promising results have been reported in lung, gastric, prostate and papillary renal cancer patients treated with these agents. The main challenges facing the effective use of HGF/Met-targeted antagonists for cancer treatment are optimal patient selection, diagnostic and pharmacodynamic biomarker development, and the identification and testing of optimal therapy combinations. The wealth of basic information, analytical reagents and model systems available concerning HGF/Met oncogenic signaling will continue to be invaluable in meeting these challenges and moving expeditiously toward more effective disease control.

Under normal conditions, hepatocyte growth factor (HGF)-induced Met tyrosine kinase (TK) activation is tightly regulated by paracrine ligand delivery, ligand activation at the target cell surface, and ligand activated receptor internalization and degradation. Despite these controls, HGF/Met signaling contributes to oncogenesis and tumor progression in several cancers and promotes aggressive cellular invasiveness that is strongly linked to tumor metastasis. The prevalence of HGF/Met pathway activation in human malignancies has driven rapid growth in cancer drug development programs. Pathway inhibitors can be divided broadly into biologicals and low molecular weight synthetic TK inhibitors; of these, the latter now outnumber all other inhibitor types. We review here the basic properties of HGF/Met pathway antagonists now in preclinical and clinical development as well as the latest clinical trial results. 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 optimal therapy combinations. The wealth of basic information, analytical reagents and model systems available concerning HGF/Met oncogenic signaling will continue to be invaluable in meeting these challenges and moving expeditiously toward more effective disease control.

PurposeThe receptors for hepatocyte and vascular endothelial cell growth factors (MET and VEGFR2, respectively) are critical oncogenic mediators in gastric adenocarcinoma. The purpose is to examine the safety and efficacy of foretinib, an oral multikinase inhibitor targeting MET, RON, AXL, TIE-2, and VEGFR2 receptors, for the treatment of metastatic gastric adenocarcinoma.Patients and MethodsForetinib safety and tolerability, and objective response rate (ORR) were evaluated in patients using intermittent (240 mg/day, for 5 days every 2 weeks) or daily (80 mg/day) dosing schedules. Thirty evaluable patients were required to achieve alpha = 0.10 and beta = 0.2 to test the alternative hypothesis that single-agent foretinib would result in an ORR of ≥25%. Up to 10 additional patients could be enrolled to ensure at least eight with MET amplification. Correlative studies included tumor MET amplification, MET signaling, pharmacokinetics and plasma biomarkers of foretinib activity.ResultsFrom March 2007 until October 2009, 74 patients were enrolled; 74% male; median age, 61 years (range, 25–88); 93% had received prior therapy. Best response was stable disease (SD) in 10 (23%) patients receiving intermittent dosing and five (20%) receiving daily dosing; SD duration was 1.9–7.2 months (median 3.2 months). Of 67 patients with tumor samples, 3 had MET amplification, one of whom had SD. Treatment-related adverse events occurred in 91% of patients. Rates of hypertension (35% vs. 15%) and elevated aspartate aminotransferase (23% vs. 8%) were higher with intermittent dosing. In both patients with high baseline tumor phospho-MET (pMET), the pMET:total MET protein ratio decreased with foretinib treatment.ConclusionThese results indicate that few gastric carcinomas are driven solely by MET and VEGFR2, and underscore the diverse molecular oncogenesis of this disease. Despite evidence of MET inhibition by foretinib, single-agent foretinib lacked efficacy in unselected patients with metastatic gastric cancer.Trial RegistrationClinicalTrials.gov NCT00725712