Abstract 1953: HER2 functionalized nanoparticles are safe and specific for in vivo HER2+ breast tumor cell detection
Authors: Zhang Marie , Vargas Jose , Dewing Antimone , Bischoff Farideh , Mathieu Kelsey , Hazle John 
Published: August 2019

Superparamagnetic Relaxometry (SPMR) is a highly sensitive in vivo detection technology that can localize and quantify superparamagnetic iron oxide (Fe3O4) nanoparticles when bound to tumor cells. Nanoparticles that reach and bind to the target cells are measureable by superconducting quantum interference device (SQUID) magnetometers (MRX instrument developed in house), while unbound nanoparticles such as those freely circulating in the bloodstream are not detected and bone and normal tissue do not produce any magnetic signal. In this study we demonstrate that anti-HER2 antibody conjugated nanoparticles exhibit great specificity and selectivity towards HER2+ tumor cells, and are safe (non-toxic) in preclinical models.

Anti-HER2 antibody conjugated nanoparticles consist of a 25nm Fe3O4 core covered by a polymer shell with PEG and antibody conjugated on the surface. The overall size of particles is 70-80nm with PDI &lt;0.1 as measured by DLS. Each particle has between 3-5 antibody molecules covalently attached to the surface with PEGylation to reduce opsonization.

Our results have shown that our antibody conjugated nanoparticles can distinguish high, medium and low HER2+ expression cell lines, such as BT474 (3+), ZR75 (2+), MCF7(0/1+) in an in vitro cell based assay. Furthermore, positive signal can be competed out by pre-incubation with free HER2 antibody. In additional, negative cell lines, such as MCF10 produce undetectable SPMR signal, demonstrating good sensitivity, specificity and selectivity. Incubation with PBMC indicates that the nanoparticles do not produce an SPMR signal, suggesting minimum non-specific interaction with lymphocytes. Extensive in vivo studies using xenograph tumor mouse models have shown the nanoparticles can selectively distinguish between MCF7 vs BT474 dual implanted tumors. In addition, as a control, we used PEG only nanoparticles and showed they do not generate measurable signal in tumor. Results are corroborated using other orthogonal detection methods, such as IHC and ICP-MS.

The safety profile of the nanoparticles has been demonstrated by analyzing nanoparticle accumulation in organs when injected at 20mg/kg dose via intravenous, intraperitoneal and subcutaneous delivery routes. All major organs except liver do not generate measurable MRX signal at multiple time points post injection, indicating no significant accumulation of nanoparticles in major organs. A full GLP toxicity study using rats is being conducted to demonstrate the safety of the anti-HER2 antibody conjugated nanoparticle prior to first-in-human use.

Together, these results suggest that our HER2 nanoparticles are safe; can provide targeted and specific delivery to cancerous tissue in vivo and generate measurable signal on our MRX detection instrument. These studies lay out ground work for our future human clinical study for breast cancer detection.

Citation Format: Marie Zhang, Jose Vargas, Antimone Dewing, Farideh Bischoff, Kelsey Mathieu, John Hazle. HER2 functionalized nanoparticles are safe and specific for in vivo HER2+ breast tumor cell detection [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1953.