Abstract A18: Modified ZD6474 (Vandetanib) derivatives with VEGFR2 and non-peptide integrin antagonist (IA) slows tumor growth
Authors: Kim Yoo-shin , O'Neill Brian E. 
Published: December 2015

Abstract
Tumor angiogenesis is an important component of cancer biology driven in part by the hypothesis that tumor vessel growth is a necessary requirement for tumor growth. Angiogenesis does not only depend on endothelial cell invasion and proliferation, it also requires pericyte coverage of vascular sprouts for vessel stabilization. These processes are coordinated by vascular endothelial growth factor (VEGF). Vandetanib, also known as ZD6474, is an orally bioavailable small molecule tyrosine kinase inhibitor of multiple growth factors that is an antagonist of the vascular endothelial growth factor receptor-2 (VEGFR-2). ZD6474 was purchased and modified to add a fluorescent dye (6-FAM). A linker was used to couple the ZD6474 monomer to create dimers, and similarly linked to FAM fluorescent dye. The two compounds were compared using human endothelial cell (HUVECs) and the cancer cell lines U-87-MG and MDA-MB-231. We compared cellular uptake and binding specificity, as well as effects on cellular viability and angiogenesis in a series of in vitro and in vivo studies. ZD6474 dimer demonstrated improved uptake in HUVECs and other VEGFR expressing cells over ZD6474 monomer in vitro. Therapeutic effects were mixed, with in vitro studies showing the dimer having the same or weaker effects compared to the monomer, while an in vivo study using pseudotumors (matrigel plug assay) seemed to indicate stronger effects could be obtained from the dimer. Finally, in biodistribution study in a xenograft tumor model, the dimer accumulated 20× greater concentration in the tumor than in the liver, spleen, or kidneys, and also 20× greater than the accumulation of the monomer or the dye alone, all at 24 h following compound injection. This study provides a rationale for the evaluation of dimeric ZD6474 as a potent imaging agent of angiogenic activity in vivo. Multiagency is a powerful strategy for achieving high-affinity molecular binding of compounds to increase their therapeutic potency or imaging potential. In our study, multivalent non-peptide integrin αvβ3 antagonists (IA) were designed for antitumor therapy. Docking and molecular dynamics were employed to explore the binding modes of IA monomer, dimer, and trimer. In silico, one IA unit binds tightly in the active site with similar pose to native ligand RGD and other parts of dimer and trimer contribute extra binding affinities by interacting with residues in vicinity of the original site. In vitro studies demonstrated that increasing valency results in increasing antiproliferative and antiorganizational effects against endothelial cells (HUVECs), and a much weaker effect on melanoma B16F10 cells. The antitumor efficacies of the IA multivalent compounds were evaluated in subcutaneous B16F10 melanoma tumor-bearing mice. At 30 mg/kg dose, the mean masses of tumors harvested 18 days after inoculation were significantly reduced (p &lt; 10-7) by 36 ± 9%, 49 ± 8%, and 71 ± 7% for the IA monomer, dimer, and trimer groups, relative to control. The importance of multivalency was demonstrated to be highly significant beyond the additive effect of the extra pharmacological sites (p = 0.00011). These results suggest that the major target of these anti-αvβ3 compounds is the neovasculature rather than the cancer cells, and the success of a multivalent strategy depends on the details of the components and linker. This is the first integrin αvβ3 multivalent ligand showing clear enhancement in antitumor effectiveness.
Citation Format: Yoo-shin Kim, Brian E. O'Neill. Modified ZD6474 (Vandetanib) derivatives with VEGFR2 and non-peptide integrin antagonist (IA) slows tumor growth. [abstract]. In: Proceedings of the AACR Special Conference: Tumor Angiogenesis and Vascular Normalization: Bench to Bedside to Biomarkers; Mar 5-8, 2015; Orlando, FL. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl):Abstract nr A18.