ENMD-2076 is an orally active kinase inhibitor with antiangiogenic and antiproliferative mechanisms of action.

ENMD-2076 is a novel orally active, small molecule kinase inhibitor with a mechanism of action involving several pathways key to tumor growth and survival: angiogenesis, proliferation, and the cell cycle. ENMD-2076 has selective activity against the mitotic kinase Aurora A, as well as kinases involved in angiogenesis (VEGFRs, FGFRs). ENMD-2076 inhibited the growth in vitro of a wide range of human solid tumor and hematopoietic cancer cell lines with IC(50) values ranging from 0.025 to 0.7 µmol/L. ENMD-2076 was also shown to induce regression or complete inhibition of tumor growth in vivo at well-tolerated doses in tumor xenograft models derived from breast, colon, melanoma, leukemia, and multiple myeloma cell lines. Pharmacodynamic experiments in vivo showed that in addition to inhibiting Aurora A, single doses of ENMD-2076 had sustained inhibitory effects on the activation of Flt3 as well as the angiogenic tyrosine kinases, VEGFR2/KDR and FGFR1 and 2. ENMD-2076 was shown to prevent the formation of new blood vessels and regress formed vessels in vivo at doses equivalent to those that gave substantial activity in tumor xenograft models. These results indicate that ENMD-2076 is a well-tolerated, orally active multitarget kinase inhibitor with a unique antiangiogenic/antiproliferative profile and provides strong preclinical support for use as a therapeutic for human cancers. Several phase 1 studies involving ENMD-2076 have been recently completed, and the compound is currently being evaluated in a phase 2 clinical trial in patients with platinum-resistant ovarian cancer.

Disease modifying and antiangiogenic activity of 2-methoxyestradiol in a murine model of rheumatoid arthritis.

BACKGROUND: A critical component of disease progression in rheumatoid arthritis (RA) involves neovascularization associated with pannus formation. 2-methoxyestradiol (2ME2) is a naturally occurring molecule with no known physiologic function, although at pharmacologic concentrations it has antiproliferative and antiangiogenic activities. We investigated the impact of orally administered 2ME2 on the initiation and development of proliferative synovitis using the anti-collagen monoclonal antibodies (CAIA) model. METHODS: Severe polyarticular arthritis was induced in Balb/c female mice by administration of 2 mg of a monoclonal antibody cocktail intravenously into the tail vein of mice. Twenty-four hours following monoclonal antibody administration, mice were injected with 25 microg of LPS (E. coli strain 0111:B4) via the intraperitoneal route. Treatment with 2ME2 (100, 75, 50, 25, 10, 1 mg/kg, p.o., daily), or vehicle control began 24 hrs following LPS challenge and continued to day 21. Hind limbs were harvested, sectioned and evaluated for DMARD activity and general histopathology by histomorphometric analysis and immunohistochemistry (vWF staining). In a separate study, different dosing regimens of 2ME2 (100 mg/kg; q.d. vs q.w. vs q.w. x 2) were evaluated. The effect of treatment with 2ME2 on gene expression of inflammatory cytokines and angiogenic growth factors in the joint space was evaluated 5 and 14 days after the induction of arthritis. RESULTS: Mice treated with 2ME2 beginning 24 hours post anti-collagen monoclonal antibody injection, showed a dose-dependent inhibition in mean arthritic scores. At study termination (day 21), blinded histomorphometric assessments of sectioned hind limbs demonstrated decreases in synovial inflammation, articular cartilage degradation, pannus formation, osteoclast activity and bone resorption. At the maximal efficacious dosing regimen (100 mg/kg/day), administration of 2ME2 resulted in total inhibition of the study parameters and prevented neovascularization into the joint. Examination of gene expression on dissected hind limbs from mice treated for 5 or 14 days with 2ME2 showed inhibition of inflammatory cytokine message for IL-1beta, TNF-alpha, IL-6 and IL-17, as well as the angiogenic cytokines, VEGF and FGF-2. CONCLUSION: These data demonstrate that in the CAIA mouse model of RA, 2ME2 has disease modifying activity that is at least partially attributable to the inhibition of neovascular development. Further, the data suggests new mechanistic points of intervention for 2ME2 in RA, specifically inhibition of inflammatory mediators and osteoclast activity.

An angiogenesis inhibitor, 2-methoxyestradiol, involutes rat collagen-induced arthritis and suppresses gene expression of synovial vascular endothelial growth factor and basic fibroblast growth factor.

OBJECTIVE: Rheumatoid arthritis (RA) pannus may be dependent on angiogenesis and several critical growth factors including vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF). 2-Methoxyestradiol (2ME2), an endogenous metabolite with low estrogen receptor affinity, has both antiangiogenic and antiproliferative activity. 2ME2 was assessed in the rat collagen-induced arthritis (CIA) model to determine if it could prevent or involute established synovitis. METHODS: Rats were immunized on Day 0 with collagen and randomized to a vehicle control or two 2ME2 prevention arms. In additional studies, multiple parallel treatment arms were initiated at Day 10 after arthritis onset. RESULTS: 2ME2 in preventive protocols at 30 or 100 mg/kg significantly delayed the onset and reduced the severity of clinical and radiographic CIA. In established CIA, oral 2ME2 at 50 mg/kg/bid, 100 mg/kg/day, and 300 mg/kg/day reduced severity compared to vehicle controls. Efficacy of 2ME2 delivery by osmotic pumps at 60 mg/kg/day was equivalent to 300 mg/kg/day by daily gavage. The 3 oral treatment protocols all significantly reduced radiographic scores in a dose-dependent fashion, with the greatest benefit at 300 mg/kg. 2ME2 showed marked suppression of synovial gene expression of proangiogenic bFGF and VEGF, with parallel reduction of synovial blood vessels. Serum antibody levels to native type II collagen were not reduced, suggesting that 2ME2 did not influence humoral immunity. CONCLUSION: Our results indicate that 2ME2 may represent a novel agent for the treatment of inflammatory autoimmune diseases such as RA.

Synthesis and in vivo antitumor evaluation of 2-methoxyestradiol 3-phosphate, 17-phosphate, and 3,17-diphosphate.

A prodrug strategy was investigated to address the problem of limited aqueous solubility and the resulting limited bioavailability of the antitumor agent 2-methoxyestradiol. The 3-phosphate, 17-phosphate, and 3,17-diphosphate of 2-methoxyestradiol were synthesized. 2-methoxyestradiol 3-phosphate was metabolized more efficiently to the parent compound in vivo than 2-methoxyestradiol 17-phosphate, and it was also more cytotoxic in cancer cell cultures than either the 17-phosphate or the 3,17-diphosphate. These results agree with the in vivo anticancer activity of 2-methoxyestradiol 3-phosphate in a mouse Lewis lung carcinoma experimental metastasis model as opposed to the 17-phosphate and 3,17-diphosphate, both of which were inactive. The in vivo antitumor activity of 2-methoxyestradiol 3-phosphate at a dose of 200 mg/kg per day was comparable to that of a maximally tolerated dose of cyclophosphamide.

Generation of a specific immunological response to FGF-2 does not affect wound healing or reproduction.

Angiogenesis, the process of new capillary formation from pre-existing vessels, has been established as an important mechanism involved in pathologic processes, such as cancer, as well as in normal physiology (Ribatti, D.; Vacca, A.; Roncali, L.; Dammacco, F. Angiogenesis under normal and pathological conditions. Haematologica 1991, 76 (4), 311-320). Basic fibroblast growth factor (FGF-2) is a critical mediator of angiogenesis that is important for normal reproduction and wound healing. FGF-2 mediates its pro-angiogenic effects by binding to heparin sulfate proteoglycan in addition to a tyrosine kinase receptor (Baird, A.; Schubert, D.; Ling, N.; Guillemin, R. Receptor and heparin-binding domain of basic fibroblast growth factor. Proc. Natl. Acad. Sci. U. S. A. 1998, 5 (7), 2324-2328; Richard, C.; Roghani, M.; Moscatelli, D. Fibroblast growth factor (FGF)-2 mediates cell attachment through interactions with two FGF receptor-1 isoforms and extracellular matrix or cell-associated heparin sulfate proteoglycans. Biochem. Biophys. Res. Commun. 2000, 276 (2), 399-405; Casu, B.; Guerrini, M.; Naggi, A.; Perez, M.; Torri, G.; Ribatti, D.; Carminati, P.; Giannini, G.; Penco, S.; Pisano, C.; Belleri, M.; Rusnati, M.; Presta, M. Short heparin sequences spaced by glycol-split urinate residues are antagonists of fibroblast growth factor 2 and angiogenesis inhibitors. Biochemistry 2002, 41 (33), 10519-10528; Murphy, P.V.; Pitt, N.; O'Brien, A.; Enright, P.M.; Dunne, A.; Wilson, S.J.; Duane, R.M.; O'Boyle, K.M. Identification of novel inhibitors of fibroblast growth factor (FGF-2) binding to heparin and endothelial cell survival from a structurally diverse carbohybrid library. Bioorg. Med. Chem. Lett. 2002, 12 (22), 3287-3290). We developed a liposomal-based peptide vaccine, L(HBD) that targets the heparin binding domain of the FGF-2 molecule. This vaccine, when inoculated into mice, inhibits angiogenesis in response to FGF-2 in a hepatic sponge model as well as tumor progression in two models of pulmonary metastatic disease. In the present studies, we further characterize the immunological and physiological responses to this vaccine. Vaccinated animals generated a specific anti-FGF-2 antibody (titer of 1:5000) that was able to inhibit FGF-2 binding to heparin sulfate in a dose dependent fashion. Cell mediated immunity was evidenced by a delayed type hypersensitivity response following challenge with the heparin binding domain peptide. Despite an immune response toward FGF-2, vaccination with L(HBD) did not result in alterations in mean time to wound healing when compared to unvaccinated animals or those treated with a liposome control. In reproductive studies, vaccinated females were not impaired in their ability to: 1) become pregnant, 2) support the growth and development of their embryos, and 3) deliver viable offspring. Furthermore, when assessed histologically, these offspring did not demonstrate any alterations in organogenesis when compared to pups born to untreated or liposome control treated females. Thus, while vaccination against FGF-2 induces a specific FGF-2 antibody response, and inhibits angiogenesis and tumor development in a pathological setting, it does not adversely alter normal physiological events dependent on FGF-2.

Identification and characterization of a very low density lipoprotein receptor-binding peptide from tissue factor pathway inhibitor that has antitumor and antiangiogenic activity.

Tissue factor pathway inhibitor (TFPI) is the major physiologic inhibitor of the extrinsic coagulation pathway. We have previously shown that TFPI is also a potent inhibitor of endothelial proliferation in vitro and of primary and metastatic tumor growth in vivo. Surprisingly, the antitumor activity of TFPI was demonstrated to be independent of its anticoagulant activity, suggesting a possible nonhemostatic mechanism of action for TFPI in these models. This antitumor mechanism may involve the very low density lipoprotein (VLDL) receptor because the in vitro antiproliferative activity of TFPI is mediated through interaction with the VLDL receptor. In the current study, we identify a 23-amino acid fragment of TFPI (TFPIc23) localized to the C-terminus, which mediates binding to the VLDL receptor. The TFPIc23 peptide inhibits endothelial cell proliferation through an apoptotic mechanism and blocks vessel outgrowth in the in vitro assays, and this activity is mediated through interaction with the VLDL receptor. In vivo, this peptide potently inhibits angiogenesis in Matrigel and chick chorioallantoic membrane models and also inhibits metastatic tumor growth. Our data demonstrate that this VLDL receptor-binding fragment of the TFPI molecule has apoptotic, antiangiogenic, and antitumor activity and suggests a possible mechanism whereby TFPI can regulate angiogenesis and tumor growth independently of its anticoagulant activity.

Anti-angiogenic vaccines as a treatment modality for cancer.

Targeting angiogenesis to inhibit tumor development is now considered a valid approach to disease modulation. Recently, a number of laboratories have focused their research on the development of cancer vaccines that target modulators of angiogenesis. In this review we describe a number of novel vaccines that target mediators of angiogenesis and inhibit tumor progression in preclinical models.

Synergistic activity of recombinant human endostatin in combination with adriamycin: analysis of in vitro activity on endothelial cells and in vivo tumor progression in an orthotopic murine mammary carcinoma model.

PURPOSE: Current combination treatment strategies in malignancy are designed to evaluate the use of cytotoxic drugs and antiangiogenic agents. Endostatin, a fragment of collagen XVIII, specifically inhibits proliferation, migration, and differentiation of endothelial cells in vitro as well as angiogenesis and tumor progression in in vivo models. In this study, we determine the antitumor effect of rhEndostatin administered alone or in combination with Adriamycin against established orthotopic murine mammary carcinoma. EXPERIMENTAL DESIGN: Mice bearing orthotopically established DA-3 mammary adenocarcinoma tumors received varying doses of rhEndostatin alone and in combination with Adriamycin to assess tumor growth inhibition. Additional studies of this in vivo combination included a determination of Adriamycin-induced cardiotoxicity and in vitro effects on human umbilical vein endothelial cell proliferation and cord formation. RESULTS: For single-agent activity, optimal tumor growth inhibition was observed after s.c. administration of 50 mg/kg/day rhEndostatin or 5 mg/kg Adriamycin injected i.v. every 4 days. Combination of Adriamycin with optimal or suboptimal doses of rhEndostatin resulted in synergistic inhibition of DA-3 tumor growth. Importantly, unlike other antiangiogenic agents, rhEndostatin did not exacerbate the cardiotoxicity of Adriamycin. The synergistic interaction between rhEndostatin and Adriamycin was also observed in vitro for inhibition of human umbilical vein endothelial cell proliferation and inhibition of cord formation. CONCLUSIONS: These data suggest that the synergy observed with rhEndostatin in combination with Adriamycin is exerted at the level of the endothelial cell and can result in enhanced tumor growth inhibition. The potential benefit of Adriamycin used in combination with rhEndostatin is being considered for clinical evaluation.