Stages in the Life of a Drug

Optimisation finding the best biological candidate(s) on the basis of safety and effectiveness. 

Chemical development finding a suitable medium-scale synthesis (maybe 1 kg) for initial clinical trials and later a large-scale synthesis for production. 

Clinical trials (several stages) initially, proof of the biological concept and finally demonstration of clinical effectiveness and safety in a substantial number of patients. 

Approval by the regulatory authorities, such as the US Food and Drug Administration (FDA) and the European Medicines Agency (EMEA), as having clinical advantages over current treatments and a suitable safety prohle. 

Release for marketing, with appropriate post-marketing surveillance to detect low-level and unexpected side-effects. 

---

The well-known drug Aspirin can demonstrate the various stages in the life of a drug substance. It was known since ancient times that the bark and leaves of the willow tree can provide relief from pain and fever. In 1832, the German chemist Piria isolated salicylic acid as the active substance in the plant material. Salicylic acid became the lead substance for further development. Soon a synthetic route was developed that replaced the tedious extraction process. Salicylic acid was used as a pain remedy, but because of its high acidity it had severe side effects when applied orally. In 1887, Felix Hoffmann, a chemist at Bayer AG, realized that the ester form of salicylic acid, acetylsalicylic acid, had fewer side effects and was even more efficacious than the free acid. The Bayer Company marketed the ester under the trade name Aspirin, which soon became the number one selling drug worldwide and is still a synonym for pain relief today. 

---