Targeting the gatekeepers: Bolstering blood-brain barrier function using targeted nanomedicine in acute ischemic stroke

Project Summary/Abstract: Pharmacologic treatment of acute ischemic stroke (AIS) is very challenging, largely due to the difficulty of rapidly and specifically delivering drugs to the ischemic region of the brain. Targeted drug delivery using affinity moieties (e.g., antibodies) can increase the local concentration of drugs, thereby improving

the therapeutic index. But targeting to blood brain barrier (BBB) epitopes such as transferrin and insulin receptors achieves poor delivery with intravenous administration (e.g., with intravascular targeted-nanocarriers, T-NCs) and is not selective to the injured region of the brain. New targeting/delivery approaches are needed for AIS.

We and others have demonstrated that Vascular Cellular Adhesion Molecule (VCAM) is highly overexpressed in the endothelial cells of the penumbra (brain regions at risk of death). Here, we will exploit this for targeted drug delivery with T-NC. We have demonstrated how VCAM T-NC provides unprecedented

enhancement of drug delivery to the brain after IV administration (>20 times higher vs. precedent approaches), specifically to the injured brain. In our pilot studies in an animal model of AIS, we observed rapid and specific uptake of CAM-targeted mAbs and T-NCs encapsulating mRNA encoding for interleukin 10/IL-10 (anti-

inflammatory cytokine), providing targeted treatment that reduced stroke volume by >60% and improved survival from 60% to 100%. Central hypothesis: VCAM-directed T-NCs can restore BBB function by delivering therapeutic RNAs to endothelial cells in the ischemic penumbra and core, limiting sustained inflammation and brain

damage after AIS. We will deliver IL-10 mRNA and siRNA against ICAM with T-NCs, to promote a local anti- inflammatory environment that will restore BBB homeostasis. Our T-NCs: i) Will target RNAs to the BBB to decrease BBB permeability to plasma proteins and reduce leukocyte infiltration; ii) Will deliver RNAs with

complementary temporal effects to act at different phases of the disease – IL-10 will reduce inflammation in the acute phase of AIS, and ICAM siRNA will protect during the subacute one. In the current proposal, we suggest: Aim 1: Vascular immunophenotype and nanocarrier delivery in AIS. Aim 2: CAM T-NC to enhance the BBB after AIS. Our deliverables are: i) generate a spatiotemporal

map for the expression of CAMs in the AIS of mice and its vascular accessibility to deliver T-NC, ii) Independently of the therapeutic efficacy of our approach will validate our central hypothesis as we are going to quantify: i) expression of the therapeutic mRNA, ii) silencing of ICAM in the BBB, and iii) cellular infiltration. We will also

identify in an unbiased way different pathways affected by ischemic stroke and how these pathways are altered after the treatment with anti-inflammatory molecules. This will help to identify new targets for treatment. In addition, we will identify the possible toxicities associated with this therapeutic approach. These results will be

key for further investigations in large animal models.