Metabolically competent stem cell systems: novel means to implement 3Rs in better drug safety assessment

Drug discovery and development consummates £400,000,000 per approved drug. 90% of potential drugs that enter the clinical stages of development fail. This is frequently due to inaccurate predictions made in the preclinical stages of development, which employ many animals or animal-based in vitro systems. Important predictions on drug safety are being made, employing embryotoxicity/teratogenicity tests in animals. In vitro platforms have been developed to reduce and replace the number of animals employed in these chronic embryotoxicity tests. However, while predicting the adverse effects of strong teratogens with high accuracy, these platforms frequently fail to identify weak to moderate teratogens. This failure is due to reliance on rodent endpoints for teratogenicity and also because of absence of appropriate human drug metabolism, frequently a prerequisite for teratogenicity. The proposed research is designed to alleviate these severe obstacles, which hamper acceptance of these valuable systems by regulators and industry. Consequently the implementation of 3R principles is also prevented. We propose to overcome this obstacle by incorporating human drug metabolism into the mouse EST test, thus creating the human mmmEST platform. In parallel we will develop a second platform that makes use of commercially available pluripotent human umbilical cord stem cells (hUCSC) supplemented with and without hepatic drug metabolising enzymes. hUCSC have the valuable property to differentiate into different tissue lineages (cardiac, neuronal and bone) in presence of commercially available media. This feature enhances the predictive power of this entirely human-based platform further. It is anticipated that the improved platforms resulting from the proposed research will greatly reduce the number of animals (by at least 10,000) employed in chronic embryotoxicity/teratogenicity tests in the EU per annum. It is hoped that these powerful approaches will counteract the demand for more animal experimentation, due to increased commercial pressures and due to the implementation of the REACH initiative.