Abstract 3638: MM-302, HER2-targeted liposomal doxorubicin, does not impair cardiomyocyte function in vitro

Abstract

Abstract In HER2+ (ErbB2+) breast cancer, the ability to combine anthracyclines, such as doxorubicin, with anti-HER2 targeted therapies is limited clinically due to potential synergistic cardiotoxicity: doxorubicin directly damages heart cells and HER2 is an important mediator of cardiac repair signaling. Herein we detail findings for MM-302, a novel HER2-targeted liposomal doxorubicin formulation. The liposomal encapsulation is designed to protect the heart from doxorubicin exposure and the HER2-targeting component mediates uptake in HER2-positive cells without blocking HER2 signaling. In order to study the potential effects of MM-302 on the heart, we performed studies using Embryonic Stem Cell (ESC)-derived cardiac cells. Total cell uptake of free doxorubicin and MM-302 into ESC-derived cardiac cells was measured using HPLC. We found that, despite expressing low levels of HER2, the ESC-derived cardiac cells do not take up MM-302, whereas doxorubicin freely enters the cells in a time and dose-dependent manner over a 3 hour time course. Subsequent to delivery, cell viability was assessed in response to free doxorubicin or MM-302 at 24 hours post 3-hour exposure. Doxorubicin resulted in cell death in a dose-dependent manner, whereas MM-302 had no effect on cardiac cell viability. To understand the mechanism underlying the cardiotoxicity associated with doxorubicin exposure, and to differentiate MM-302 from existing therapies, we measured cell functional responses in ESC-derived cardiac cells, including cell stress (phopsho-p53), DNA damage (gamma-H2AX) and apoptosis (cleaved-PARP) with high-content microscopy. We demonstrated that, while doxorubicin treatment results in DNA damage, cell stress, apoptosis, and ultimately cell death in a dose-dependent manner, MM-302 does not. Our findings demonstrate that MM-302 provides a means to deliver doxorubicin to high HER2-expressing cancer cells, while sparing exposure, accumulation, and toxicity in non-target (low HER2-expressing) cells, such as cardiomyocytes. This opens an exciting avenue for potentially introducing a novel anthracycline product for the treatment of HER2+ breast cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3638. doi:10.1158/1538-7445.AM2011-3638