Abstract 4572: Bioorthogonal, two-component drug delivery in HER2(+) breast cancer mouse models
Authors: Hapuarachchige Sudath , Zhu Wenlian , Kato Yoshinori , Artemov Dmitri 
Published: May 2015

Abstract
The HER2 receptors are overexpressed in ∼25% of breast cancer patients and characterized by poor internalization capability. The humanized monoclonal antibody, trastuzumab (Tz), is used as a first-line treatment for HER2(+) breast cancers. However, approximately 50% of patients with HER2(+) disease do not benefit from trastuzumab or the disease becomes refractory to the drug. We have demonstrated a target-specific intracellular delivery of therapeutics using new two-step/two-component drug delivery system driven by click chemistry that results in the in situ complexation and rapid internalization. Two delivery strategies based on azide (Az)/dibenzylcyclooctyne (DBCO), (Click-1) and trans-cyclooctene (TCO)/tertrazine (Tt), (Click-2) bioorthogonal click reactions were tested in human HER2(+) breast cancer mouse models. Trastuzumab was functionalized with Az or TCO groups and labeled with NIR CF-680 dye, to prepare Tz(Az/TCO)a(CF-680)b as the pretargeting component. Albumin substituted with paclitaxel (Px), functionalized with DBCO or Tt, and labeled with NIR CF-750 dye to prepare Alb(DBCO/Tt)x(Px)y(CF-750)z was used as the second delivery component. BT-474 HER2(+) breast cancer models were grown in athymic nude mice. Five groups of mice (a) untreated/PBS (b) first-component without Az, control for Click-1 (c) treated by Click-1 (d) first-component without TCO, control for Click-2, and (e) treated by Click-2 were used for the study. On day 0 mice were imaged with in vivo Xenogen optical imaging system and injected with the first pretargeting component followed by the second drug delivery component after 6h. Similarly, the second dose was administered on day 7. Mice were imaged at days 0 and 7 after administration of therapy to confirm the accumulation of components in tumors. Tumor volumes were measured every forth day up to day 20. After 21 days mice were sacrificed and tumors were extracted and analyzed by H&E staining for possible necrosis. Accumulation of the pretargeting and delivery components were observed in mice treated under Click-1 and Click-2 conditions compared to the corresponding controls and untreated mice. However, the accumulation was significantly higher in Click-2 group in comparison to all other groups. In addition, both pretargeting and delivery components were retained in the tumor for much longer time in Click-2 group than in other groups. We observed a tumor shrinking and significant decrease of tumor growth rate in Click-2 group. The results were confirmed by H&E immunohistochemistry analysis showing significant necrotic area in the Click-2 treated groups.
Citation Format: Sudath Hapuarachchige, Wenlian Zhu, Yoshinori Kato, Dmitri Artemov. Bioorthogonal, two-component drug delivery in HER2(+) breast cancer mouse models. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4572. doi:10.1158/1538-7445.AM2014-4572