What is the first challenge in developing a new drug that acts on an enzyme?

1. One of the first challenges in drug development is identifying the specific molecule that the drug is intended to target. 2. In the case of statins, HMG-CoA reductase is that drug target. 3. Identifying the target alone is not sufficient, since scientists also need to know how it acts inside the cell and which reactions go awry in disease. 4. Only once the target and the pathway are known does the actual process of drug design begin. 5. Clinical trials and regulatory approval come much later, after a prototype has already proved successful in vitro. 6. Scaling up synthesis is a manufacturing question rather than the first scientific challenge. _Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 6 "Metabolism", section 6.5 Enzymes_