The HER2 (ErbB-2) is a class of epidermal growth factor receptors, which is overexpressed in 20-30% breast cancer cases that consequently show poor prognosis, cancer growth, and progression. Trastuzumab is a humanized, monoclonal antibody widely used as a first line therapeutic against HER2(+) breast cancers. However, recent clinical observations reveal that approximately half of patients with HER2(+) disease do not benefit from trastuzumab or have disease that becomes refractory to it. The combination therapy based on antibody-drug conjugates is a promising strategy to overcome the immunotherapeutic resistance of tumors. Since single delivery components face the barriers of extravasation from vessels and diffusion to the target site, we have developed a sequential two-component delivery system where components are assembled on the target cell surface and internalized delivering high dose of therapeutics. In this study, trastuzumab was functionalized with PEGylated azide groups and labeled with rhodamine or NIR CF-680 dyes, to obtained T(PEG4-Az)8(Rhod/CF-680)2 as a first delivery component. Albumin (BSA) was functionalized with strain-promoted alkyne (DIBO), substituted with paclitaxel, and labeled with Alexa Fluor 488 or CF-750 to obtained A(DIBO)10(Pac)2(Alexa 488/CF-750)2 as the second delivery component. Substitution of paclitaxel was carried out with sulfo-NHS-paclitaxel which increases the solubility of the drug in reaction medium. While reduced solubility of paclitaxel modified BSA was observed for the substitution of >5 paclitaxel molecules, one to four paclitaxel substitutions on BSA shows no precipitations in PBS. The in vivo cytotoxicity of the two-component delivery system was assessed using HER2(+) overexperssing BT-474 breast cancer cells and a standard WST-8 assay. For in vitro therapeutic study, we used T(PEG4-Az)8(CF-680)2 and A(DIBO)10(Pac)2(CF-750)2 (with non-functionalized trastuzumab as the first component in controls). We observed an increased cytotoxicity of the two-component delivery system with IC50 of 0.101 μM, comparing to IC50 of 0.247 μM for the control.

Citation Format: Sudath Hapuarachchige, Yoshinori Kato, Dmitri Artemov. Cytotoxicity of two-component drug delivery systems targeting HER2(+) cancer cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5667. doi:10.1158/1538-7445.AM2013-5667