Another application is drug repositioning using disease-specific iPSCs. In drug repositioning, existing drugs already approved for specific diseases are tested to find new applications for other diseases. For example, a human iPSC model derived from achondroplasia patients with fibroblast growth factor receptor 3 (FGFR3) mutations showed that patient iPSCs did not differentiate well into cartilage tissue136. Using this model, a screen for molecules that rescue chondrogenically differentiated iPSCs from the defective cartilage phenotype identified several statins, which are approved drugs for cardiovascular disease. The same study found that statins could promote the growth of shortened limbs in a mouse model of FGFR3-linked disease. These results indicate that statins may be repositioned as candidate drugs for achondroplasia136. As another example of drug repositioning, the anti-epileptic drug ezogabine was found to be effective in an iPSC model of the motor neuron disease amyotrophic lateral sclerosis (ALS) and is now undergoing clinical trial137. In this study, the authors showed the effect of ezogabine on an iPSC model derived from not only ALS patients with mutations in the superoxide dismutase 1 (SOD1) gene, but
