A Vascularized Blood-Brain Barrier Model for In Vitro Testing of Drug and Immunotherapy Delivery

PROJECT SUMMARY The brain is a highly-specialized, finely-tuned organ that depends for its function on maintaining homeostasis within narrowly-defined limits. This is achieved in large part by the Blood-Brain Barrier (BBB), which tightly regulates what can and can’t get into the brain. Functionally, the BBB is the combined work of endothelial cells (EC), pericytes and astrocytes, the latter two of which act on the EC to maintain an extensive network of tight junctions, promote the expression of specialized transporters, and limit the rate of transcellular pinocytosis. This lack of free transfer between blood and brain for non-lipophilic species severely limits the entry of many, otherwise useful, small molecule drugs. For example, cisplatin (lt3% Brain/Plasma ratio), is effective in non-brain tumors, but has poor penetrance and low efficacy against brain tumors such as glioma. Similarly, delivery of immunotherapeutics such as bevacizumab (0.2%) and bi-specific antibodies is also limited, and much is still to be understood regarding the delivery of immune cells to the brain, including CAR-Ts, NK cells, γδ T cells and the patient’s own monocytes and lymphocytes. Finally, there are significant differences between mouse and human physiology including in the immune system. Many drug developers are therefore turning to human cell- based systems rather than mouse models. The primary goal of this Phase I SBIR application is to demonstrate the feasibility of Aracari Biosciences’ proprietary technology to model appropriate drug and immunotherapeutic delivery across the human BBB. Aracari’s patented core technology is a perfusable human vascular network within a microfluidic device that fits in a convenient 96-well plate format. This technology has been successfully developed into commercialized products including the vascularized micro-organ (VMOTM) and the vascularized micro-tumor (VMTTM). Importantly, leukocytes can be perfused through the vessels and on stimulation they will adhere and extravasate as they do in vivo. We have also developed a vascularized micro-brain (VMB), which is the focus of this application. This incorporates a perfused neurovascular unit (NVU) comprised of human BBB EC, pericytes and astrocytes, all embedded in a brain-mimicking extracellular matrix. The vessels show upregulation of BBB transporters and junctional proteins, and greatly-reduced permeability compared to non- NVU vessels. Tumor cells (glioma) can be added to model brain tumors (VMB-T) and the potential compromise of the BBB. This model will provide unprecedented opportunities to study drug responses of glioma and other brain tumors in a more natural environment. Our preliminary data show the feasibility of our goals which are: Specific Aim 1: Characterize permeability of a small panel of brain-targeted drugs in the VMB and VMB-T Specific Aim 2: Characterize delivery of a small panel of immunotherapeutic drugs in the VMB and VMB-T Specific Aim 3: Characterize delivery of immune cells in the VMB and VMB-T Completion of these aims will provide us with a unique tool we can offer to pharmaceutical companies for studies on BBB properties, and delivery of neuroactive drugs and immuno-oncology drugs and cells.