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Anti-Vascular Endothelial Growth Factor Receptor-1 Antagonist Antibody as a Therapeutic Agent for Cancer

Authors' Affiliations: Departments of ¹ Experimental Therapeutics, ² Protein Sciences, ³ Antibody Technology, and ⁴ Cell Engineering and Expression, ImClone Systems, Inc., New York, New York

Requests for reprints: Yan Wu, Department of Experimental Therapeutics, ImClone Systems, Inc., 180 Varick Street, New York, NY 10014. Phone: 212-645-1405; Fax: 212-645-2054; E-mail: Yan.Wu{at}imclone.com.

Purpose: Vascular endothelial growth factor receptor-1 (VEGFR-1) plays important roles in promotion of tumor growth by mediating cellular functions in tumor vascular endothelium and cancer cells. Blockade of VEGFR-1 activation has been shown to inhibit pathologic angiogenesis and tumor growth, implicating VEGFR-1 as a potential therapeutic target for the treatment of cancer. We have thus developed a VEGFR-1 antagonist human monoclonal antibody designated as IMC-18F1 and evaluated its antitumor activity in preclinical experimental models to show the therapeutic potential of the antibody for cancer treatment in clinic.

Experimental Design: Human IgG transgenic mice were used for generation of anti-VEGFR-1 antibodies. Anti-VEGFR-1-specific blocking antibodies were identified using solid-phase binding and blocking assays. Inhibitory antitumor cell activity of IMC-18F1 was assessed in cell-based kinase and growth assays. Pharmacokinetic/pharmacodynamic studies were done to determine the association of antibody blood level with antitumor efficacy of the antibody in vivo. Antitumor efficacy of the anti-VEGFR-1 antibodies as monotherapy and in combination with cytotoxic agents was evaluated in human breast cancer xenograft models.

Results: A fully human neutralizing antibody, IMC-18F1, was shown to be a high-affinity (K_D = 54 pmol) inhibitor of VEGFR-1 ligand binding (VEGF-A, VEGF-B, and placental growth factor). IMC-18F1 inhibited ligand-induced intracellular activation of VEGFR-1 and mitogen-activated protein kinase signaling and prevented ligand-stimulated in vitro growth of breast cancer cells. In vivo, IMC-18F1 suppressed the growth of human breast tumor xenografts in association with reduced mitogen-activated protein kinase and Akt activation, reduced tumor cell proliferation, and increased tumor cell apoptosis. Pharmacokinetic/pharmacodynamic studies established a plasma elimination half-life of 5 days for IMC-18F1 and a steady-state trough plasma therapeutic threshold of 88 µg/mL. Importantly, inhibition of mouse and human VEGFR-1 with MF1 and IMC-18F1, respectively, enhanced the antitumor efficacy of cytotoxic agents commonly used to treat breast cancer.

Conclusions: Based on preclinical validation studies, IMC-18F1 anti-VEGFR-1 has potential to provide clinical benefit to cancer patients.

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