Novel Screening Method for Inhibitors of Multidrug-Resistant Transporters
Overview Drug transport is of fundamental importance to the efficacy and toxicity of all drugs. From the route of administration to the site of action, a drug encounters numerous biological barriers, including efflux pumps that pump drugs out of cells. Our novel method uses spheroidal models to screen for drugs that inhibit efflux pumps without blocking gap junctions in tumors; the selected drugs represent potential treatments for tumors.
Market Opportunity Efflux pumps are transport proteins involved in extruding toxic substrates—including virtually all classes of clinically relevant antibiotics—from within cells to the external environment. The efflux pump P-glycoprotein (Pgp), a member of the superfamily of ATP binding cassette (ABC) transporters, is localized to the plasma membrane of cells and is present in both normal and diseased tissues. Though the function of Pgp is protection from toxicity, it is a significant barrier to drug transport and delivery, hindering absorption through the intestine and increasing clearance into bile and urine. It is also up-regulated in diseased tissues and the cells of solid tumors, where it increases resistance to anti-cancer chemotherapeutics. Unfortunately, many drugs of various pharmacological classes are substrates of Pgp. Although effective in vitro, Pgp inhibitors identified thus far have been ineffective in the clinic or have had unexpected drug-drug interactions, leading to increased toxicity. Thus, there is a need for new in vitro models that can be used to predict potential toxicities and unwanted drug-drug interactions or to discover new and more effective inhibitors of drug efflux transporters.
Innovation and Meaningful Advantages We have developed a method to screen for drugs that inhibit efflux pumps and do not block gap junctions in tumors. Our novel method is based on the culturing of cells in media containing the drug of interest to form self-assembled spheroids with a core and outer shell. The spheroids are then incubated in the presence of a substrate for the efflux pump. Uptake of the substrate of the efflux pump and its distribution within the spheroids is imaged. Increased concentration of the substrate in the outer shells of the spheroids relative to spheroids in the absence of drug indicates that the drug inhibits the efflux pump, and an increase in the substrate at the cores of the spheroids indicates that gap junctions have not been blocked. This methodology enables the selection of drugs that can be used to treat a tumor.
Spheroidal in vitro models are superior to 2D models, as they more accurately replicate the phenotype of cancer cells, as well as the complex tumor microenvironment. Because cancer cells grown in 3D are far more resistant to treatment with radiation and chemotherapy than cells grown in 2D, they are thought to be more similar to tumors in vivo.
Our method could easily be extended to numerous cell types that would self-assemble spheroids. Examples of suitable cells include C6 glioblastoma cells, CaCo-2 colon cancer cells, MCF-7 breast cancer cells, HEK-293 human embryonic kidney cells, any primary tumor cells, primary hepatocytes, endothelial cells, and fibroblasts.
Collaboration Opportunity We are interested in exploring 1) startup opportunities with investors; 2) research collaborations with leading pharmaceutical companies to further develop this method of drug screening; and 3) licensing opportunities.
Principal Investigator Jeffrey Morgan, PhD Professor of Pathology and Laboratory Medicine Professor of Engineering Brown University jeffrey_morgan@brown.edu https://vivo.brown.edu/display/jrmorgan
IP Information US9,468,680B2; patent issued, 2016-10-18.
Publications Advances in the formation, use and understanding of multi-cellular spheroids Expert Opin Biol Ther. 2012 Multilayer Spheroids To Quantify Drug Uptake and Diffusion in 3D Mol Pharm. 2014