The effect of a soluble c-Met receptor on phosphorylation of c-Met and tumor growth in preclinical models Free

2087A

Background: c-Met is a receptor tyrosine kinase that is frequently over expressed and amplified in many types of human cancers. Hepatocyte Growth Factor (HGF, also known as scatter factor) is the only known ligand for c-Met. We have generated soluble c-Met receptor-Fc fusions that bind to HGF and prevent activation of c-Met. The effects of human or murine c-Met.Fc were evaluated on HGF-induced phosphorylation and invasion in vitro, and on tumor growth in animals.

Methods: Human and murine c-Met.Fc wereexpressed and purified from CHO cells transfected with an expression construct comprising the extracellular domain of human or murine c-Met fused to the Fc fragment of human IgG1. Human and mouse HGF were expressed and purified from transfected CHO cells. FACS data were generated for human and mouse HGF binding to human c-Met.Fc using an anti-human IgG antibody directed against HGF and labeled with phycoerythrin. Biacore binding data were generated for human and mouse ligand and receptors by measuring free HGF binding to c-Met.Fc immobilized on a CM5 chip at various solution concentrations of c-Met.Fc. HGF induced c-Met phosphorylation was evaluated by an immuno-assay. Invasion assays were performed using Matrigel coated filters and the FluoroBlok^® Invasion System.

The activity of human and murine c-Met.Fc (at doses up to 100 µg twice weekly) was evaluated in U-87 MG (human glioblastoma carcinoma) and CT26 (murine colon carcinoma) tumor xenograft models in CD-1 NU/NU mice (n=10/group).

Results: Human and mouse HGF bound equally well to both human and mouse c-Met, as evidenced by FACS and Biacore measurements. This binding led to robust inhibition of c-Met phosphorylation in human and mouse cells and to a dose-dependent inhibition of human or mouse HGF stimulated cellular invasion of normal murine mammary gland cells.

Systemic administration of human c-Met.Fc significantly inhibited tumor growth in the human HGF-dependent U-87 MG xenograft model at doses of 30 and 100 µg daily (p<0.0001). Furthermore, regression of established tumors was achieved at a dose of 100 µg (p<0.05). Similarly, murine c-Met.Fc demonstrated significant tumor growth inhibition at 100 µg twice per week in the CT26 syngeneic tumor model (p<0.002). Pharmacokinetic analysis was performed for both human and murine c-Met.Fc administered via both subcutaneous and intraperitoneal routes and the half-life was found to range from 27 to 45 hours. In all animal studies, c-Met.Fc was well tolerated.

Conclusion: We have generated a novel c-Met soluble receptor that effectively blocks HGF-induced activation of c-Met and inhibits the growth of tumor xenografts. These data further support Met as an oncology therapeutic target.