**3. Classes of epigenetic enzymes targeted with repurposed market drugs**

As discussed in previous sections, epigenetics is pivotal to the etiology and progression of different human diseases. And multiple studies have shown that targeting epigenetic enzymes has a profound effect on attenuating the severity or progression of diseases [59]. Given that the traditional approach to drug discovery is costly and time-inefficient, it is more valuable to reposition readily available market drugs for new disease indications. In this section, we will discuss the major epigenetic enzymes being targeted with repurposed drugs or preclinical compounds and examples of the repurposed drugs with their old and new indications.
