Anti-vascular endothelial growth factor receptor-1 antagonist antibody as a therapeutic agent for cancer.

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 (KD=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 microg/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.

Anti-transforming growth factor beta receptor II antibody has therapeutic efficacy against primary tumor growth and metastasis through multieffects on cancer, stroma, and immune cells.

PURPOSE: Transforming growth factor beta (TGFbeta) is a pleiotropic cytokine that affects tumor growth, metastasis, stroma, and immune response. We investigated the therapeutic efficacy of anti-TGFbeta receptor II (TGFbeta RII) antibody in controlling metastasis and tumor growth as well as enhancing antitumor immunity in preclinical tumor models. EXPERIMENTAL DESIGN: We generated neutralizing antibodies to TGFbeta RII and assessed the antibody effects on cancer, stroma, and immune cells in vitro. The efficacy and mechanism of action of the antibody as monotherapy and in combination with chemotherapy in suppression of primary tumor growth and metastasis were evaluated in several tumor models. RESULTS: Anti-TGFbeta RII antibody blocked TGFbeta RII binding to TGFbeta 1, 2, and 3, and attenuated the TGFbeta-mediated activation of downstream Smad2 kinase, invasion of cancer cells, motility of endothelial and fibroblast cells, and induction of immunosuppressive cells. Treatment with the antibody significantly suppressed primary tumor growth and metastasis and enhanced natural killer and CTL activity in tumor-bearing mice. Immunohistochemistry analysis showed cancer cell apoptosis and massive necrosis, and increased tumor-infiltrating T effector cells and decreased tumor-infiltrating Gr-1+ myeloid cells in the antibody-treated tumors. Fluorescence-activated cell sorting analysis indicated the significant reduction of peripheral Gr-1+/CD11b+ myeloid cells in treated animals. Concomitant treatment with the cytotoxic agent cyclophosphamide resulted in a significantly increased antitumor efficacy against primary tumor growth and metastasis. CONCLUSIONS: These preclinical data provide a foundation to support using anti-TGFbeta RII antibody as a therapeutic agent for TGFbeta RII-dependent cancer with metastatic capacity.

The vascular endothelial growth factor receptor (VEGFR-1) supports growth and survival of human breast carcinoma.

Vascular endothelial growth factor receptor 1 (VEGFR-1) is present on endothelial cells and subsets of human tumor cells, raising the hypothesis that angiogenic factors may promote tumor growth both by inducing angiogenesis and directly signaling through activation of VEGFR-1 on tumor cells. Here, we report that VEGFR-1 is expressed on a panel of 16 human breast tumor cell lines, and the vasculature and the tumor cell compartment of a subset of breast carcinoma lesions, and that selective signaling through VEGFR-1 on breast cancer cells supports tumor growth through downstream activation of the p44/42 mitogen-activated protein kinase (MAPK) or Akt pathways. Ligand-stimulated proliferation of breast tumor cells was inhibited by specific blockade with an anti-VEGFR-1 neutralizing monoclonal antibody. Treatment with anti-VEGFR-1 mAb significantly suppressed the growth of DU4475, MCF-7, BT-474 and MDA-MB-231 breast xenografts in athymic mice. Histological examination of anti-VEGFR-1 mAb treated tumor xenografts showed a significant reduction of activation of the p44/42 MAPK or Akt pathways in tumor cells resulting in an increase in tumor cell apoptosis. Importantly, cotreatment with mAbs targeting human VEGFR-1 on tumor cells and murine VEGFR-1 on vasculature led to more potent growth inhibition of breast tumor xenografts. The results suggest that VEGF receptors may not only modulate angiogenesis, but also directly influence the growth of VEGF receptor expressing tumors.

Modulation of polymorphonuclear cell interleukin-8 secretion by human monoclonal antibodies to type 8 pneumococcal capsular polysaccharide.

Pneumococcal capsular polysaccharide (PS) vaccines induce type-specific immunoglobulin M (IgM), IgG, and IgA. Type-specific IgG to the PS is sufficient to confer protection against the homologous serotype of the pneumococcus, but the efficacies of type-specific IgM and IgA are less well understood. We examined the in vitro activities and efficacies in mice of two human monoclonal antibodies (MAbs) to type 8 PS, NAD (IgA) and D11 (IgM). MAb-mediated opsonophagocytic killing was evaluated after coculture of type 8 pneumococci with human polymorphonuclear cells (PMNs), type-specific or control MAbs, and human complement sources. The effects of the MAbs on PMN interleukin-8 (IL-8) and IL-6 secretion were determined in supernatants from cocultures containing pneumococci and PMNs by enzyme-linked immunosorbent assay. MAb efficacy was determined in an intratracheal model of type 8 infection in mice with classical complement pathway deficiency. Both MAbs were protective in 100% of infected mice. Neither MAb promoted a significant amount of killing of type 8 pneumococci compared to its isotype control MAb. Both type-specific MAbs mediated complement-dependent modulation of PMN IL-8 secretion, with increased secretion at effector/target (E:T) ratios of 500:1 and 50:1 and reduced secretion at 1:5. Trypan blue staining revealed that PMNs cocultured with D11 were less viable at an E:T ratio of 1:5 than PMNs cocultured with the control MAb. PMN IL-6 secretion was increased by both type-specific and control MAbs. These results suggest that certain type-specific IgM and IgAs might contribute to host defense by modulation of the inflammatory response to pneumococci.