Synthetic Chemical Medicines

3. How are chemical medicines discovered?

By studying a disease, scientists can understand what causes the illness and which cells and their receptors are involved. This research can help scientists to develop new medicines to treat diseases and to relieve symptoms.

Once a target receptor molecule or an enzyme has been identified, scientists begin to look for potential substances that will interact with the target to correct disease-related activity. This research can involve searching through enormous libraries of millions of molecules that have been developed by pharmaceutical companies to speed up medicines development. Large-scale testing of potentially useful molecules from the libraries (also called high-throughput screening) is conducted to discover which ones will bind to the target receptor.

Although this process will help to identify potential active substances, more work is needed to select the molecules that are likely to bind to the target, but not to other receptors, because this may cause side effects. The most promising molecules that are discovered will then be modified in many ways to try to make an effective medicine that has few side effects. It is also important that the molecule has other properties that will allow it to be used as a medicine. For example, the active ingredients in medicines that need to be swallowed must be able to reach their target without being broken down by the digestive system.

When scientists find a molecule with the desired properties of a potential medicine, testing in animals is necessary. If this testing shows the substance is safe, testing in humans follows. Finally, regulatory authorities will consider whether or not to approve the medicine for use in humans.

The ideal molecules should:

• Hit the target (ideally only the target and no other healthy cells or enzymes).
• Have few side effects.
• Be absorbed by the body.
• Reach the right part of the body to hit the target.
• Remain in the body long enough to have an effect.
• Be able to be manufactured in large quantities.
• Be stable and have a long shelf life.
• Be convenient for patients to use.