DiscussionPharmaceutical candidate compounds require extended period of time and large amount of development costs before reaching the market. However, for various reasons, most of the candidates will be canceled in their development process. One major reason is hepatotoxicity. Recently, in the beginning of the drug screening process, simple and fast evaluation by using cell-based assays has been given great importance in terms of safety and cost reduction. Although human primary hepatocytes have been widely used for hepatotoxicity, the following problems still remain: lot-to-lot variation, commercial availability and unstable supply. Moreover, there is a great difficulty in executing long-term tests using hepatocytes from the identical donor.
Human-derived iPS cells are pluripotent stem cells with the ability of infinite proliferation and differentiation into various cells including hepatocytes. Therefore, iPS cells enable unlimited production of hepatocytes possessing the same genetic back ground. Furthermore, it is possible to produce various donor-derived hepatocytes since human-derived iPS cells can be establish from varied race, sex and genetic back ground.