Editing Embryonic stem cell (section)

===Drug discovery===

Besides becoming an important alternative to organ transplants, ESCs are also being used in the field of toxicology, and as cellular screens to uncover new chemical entities that can be developed as [[small-molecule drug]]s. Studies have shown that cardiomyocytes derived from ESCs are validated ''in vitro'' models to test drug responses and predict toxicity profiles.<ref name="davila" />  ESC derived cardiomyocytes have been shown to respond to pharmacological stimuli and hence can be used to assess cardiotoxicity such as [[torsades de pointes]].<ref>{{cite journal|pmid=19277978|year=2009|last1=Jensen|first1=J|last2=Hyllner|first2=J|last3=Björquist|first3=P|title=Human embryonic stem cell technologies and drug discovery|volume=219|issue=3|pages=513–519|doi=10.1002/jcp.21732|journal=Journal of Cellular Physiology|s2cid=36354049}}</ref>

ESC-derived hepatocytes are also useful models that could be used in the preclinical stages of drug discovery. However, the development of hepatocytes from ESCs has proven to be challenging and this hinders the ability to test drug metabolism. Therefore, research has focused on establishing fully functional ESC-derived hepatocytes with stable phase I and II enzyme activity.<ref>{{cite journal|pmid=17346923|year=2007|last1=Söderdahl|first1=T|last2=Küppers-Munther|first2=B|last3=Heins|first3=N|last4=Edsbagge|first4=J|last5=Björquist|first5=P|last6=Cotgreave|first6=I|last7=Jernström|first7=B|title=Glutathione transferases in hepatocyte-like cells derived from human embryonic stem cells|volume=21|issue=5|pages=929–937|doi=10.1016/j.tiv.2007.01.021|journal=Toxicology in Vitro}}</ref>