Abstract 2865: The peptide transporter K16ApoE increases drug delivery across the blood brain barrier in an experimental animal model of melanoma brain metastases
Authors: Aasen Synnøve Nymark , Espedal Heidi , Keunen Olivier , Holte Christopher Florian , Baghirov Habib , Bjerkvig Rolf , Karlsen Tine Veronica , Tenstad Olav , Olberg Dag Erlend , Sarkar Gobinda , Jenkins Robert B , Thorsen Frits 
Published: July 2017

Abstract
Introduction: Patients with brain metastases await a dismal prognosis. Regardless of the continuous progress in drug development, a major problem is the delivery of drugs across the blood brain barrier (BBB) and into the metastatic neoplasms. The BBB excludes almost all compounds, in particular highly charged, hydrophilic or large compounds, and most of the current chemotherapeutic agents are thus unable to penetrate the BBB. Varying strategies to transiently open the BBB have been studied previously. Here, we describe a peptide transporter comprising 16 lysine residues and 20 amino acid residues corresponding to the low density lipoprotein receptor (LDLR) binding domain of apolipoprotein E (ApoE). We show that the peptide (K16ApoE) is able to transiently open the BBB for drug-delivery into experimental brain metastases.
Experimental procedures: A systemic study of the ability of the peptide to open the BBB was conducted by dynamic contrast enhanced magnetic resonance imaging (DCE MRI) in nonobese diabetic/severe combined (nod/scid) mice. The BBB permeability was studied after administering 200 μg of the peptide intravenously. Further, cellular effects after treatment with the peptide was investigated in vitro using confocal microscopy, flow cytometry and impedance experiments. The biodistribution of the peptide was studied in blood plasma and several organs using 125I labeled K16ApoE. Finally, a treatment study was initiated, treating the animals with the peptide in combination with the B-RAF inhibitor Dabrafenib, only Dabrafenib or vehicle.
Summary: After injecting the K16ApoE peptide into the mice, a transient opening of the BBB for up to 4 hours was clearly demonstrated by DCE-MRI. Microscopy showed that the peptide disrupted brain endothelial cell monolayers, reducing the barrier properties of the cells. The impedance experiments displayed that the permeability through endothelial cell barriers was increased after treatment with K16ApoE, and a dose-dependent cell death pattern was observed at higher concentrations of K16ApoE.The peptide did not affect endothelial cell tight junctions. The biodistribution study showed that the peptide was eliminated from blood plasma in less than five minutes through the kidneys. The treatment study displayed that the group of animals receiving K16ApoE followed by Dabrafenib had smaller tumor volumes than the other two animal groups.
Conclusions: We have shown that the peptide opens the BBB and facilitates a therapeutic window of 4 hours. The peptide did in combination with Dabrafenib decrease the number of experimental brain metastases in our studies. Thus, the current strategy could also have the potential to improve the treatment of patients with brain metastatic disease.
Citation Format: Synnøve Nymark Aasen, Heidi Espedal, Olivier Keunen, Christopher Florian Holte, Habib Baghirov, Rolf Bjerkvig, Tine Veronica Karlsen, Olav Tenstad, Dag Erlend Olberg, Gobinda Sarkar, Robert B Jenkins, Frits Thorsen. The peptide transporter K16ApoE increases drug delivery across the blood brain barrier in an experimental animal model of melanoma brain metastases [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2865. doi:10.1158/1538-7445.AM2017-2865