John W. Madsen

Administration of a liposomal FGF-2 peptide vaccine leads to abrogation of FGF-2-mediated angiogenesis and tumor development

Basic fibroblast growth factor (FGF-2) is an important stimulator of angiogenesis that has been implicated in neoplastic progression. Attempts to neutralize or modulate FGF-2 have met with some success in controlling neovascularity and tumor growth. In the present study, two peptides: one corresponding to the heparin binding domain and the other to the receptor binding domain of FGF-2, exerted dose-dependent inhibition of FGF-2-stimulated human umbilical vein endothelial cell proliferation (IC(50)=70 and 20 microg/ml, respectively). The identification of these functional regions suggested that targeting these domains might be an approach for the modulation of FGF-2 function. To investigate this possibility, we vaccinated mice with either the heparin binding domain peptide or the receptor binding domain peptide of FGF-2 in a liposome/adjuvant format, and analyzed the effect of vaccination on FGF-2-driven angiogenesis, tumor development and immune status. Mice vaccinated with the heparin binding domain peptide generated a specific antibody response to FGF-2, blocked neovascularization in a gelfoam sponge model of angiogenesis, and inhibited experimental metastasis by >90% in two tumor models: the B16BL6 melanoma and the Lewis lung carcinoma. These effects were not observed in mice treated with the receptor binding domain peptide conjugated to liposomes or liposomes lacking conjugated peptide. These data suggest that a heparin binding domain peptide of FGF-2, when presented to a host in a liposomal adjuvant formulation, can ultimately lead to inhibition of angiogenesis and tumor growth.

Zinc ligand-disrupted recombinant human Endostatin: Potent inhibition of tumor growth, safety and pharmacokinetic profile

Endostatin, a potent endogenous inhibitor of angiogenesis, inhibits the growth of primary tumors without induction of acquired drug resistance in mice. We report that a soluble recombinant human (rh) Endostatin produced with characteristics of the native Endostatin, effectively inhibited the growth of primary tumors and pulmonary metastases in a dose-dependent manner. We also show that deletion of two of the four zinc ligands of rhEndostatin did not affect this potent tumor inhibiton. The growth of established Lewis lung primary tumors implanted into mice was inhibited (80–90%) upon systemic treatment with 50 mg/kg/12 h of rhEndostatin. Using the B16-BL6 murine experimental pulmonary metastases model, rhEndostatin administered at 1.5 mg/kg/day or 4.5 mg/kg/day beginning 3- or 11-days post tumor cell injection, respectively, resulted in an approximate 80% inhibition of tumor growth. At effective anti-tumor doses of 1.5 and 50 mg/kg, pharmacokinetic modeling in mice showed (a) the protein was 100% bioavailable, (b) the AUC ranged from 16 to 700 ngml/h and (c) the Cmax ranged from 161 to 4582 ng/ml. At the highest dose tested (300 mg/kg), delivered as a single bolus, no drug-related toxicity was observed in a Cynomolgus monkey infused with rhEndostatin. No toxicity was observed even at AUC and Cmax values that were 1.3- to 56-fold higher than those observed in mice with tumors that were potently inhibited. Our production system yields a well characterized, soluble and potent rhEndostatin at quantities sufficient for human use. The preclinical studies described herein are an important first step toward the assessment of Endostatin in the clinic.