The use of biological organisms or enzymes to create, break down or transform a material.
How well the drug works
A polymer made up of amino acids joined by peptide bonds. The amino acids present and the order in which they occur vary from one protein to another.
Ideas for new medicines come from all sorts of places. Sometimes there is a traditional plant that has been used to treat a disease. Identifying why this plant works and what the actual substance is that is affecting the disease is one source of new medicines. Or there may be an existing way of treating a disease which could be improved - for example existing medicines might need to be taken several times a day, or may not work for all people. But mainly it is knowledge of how the body works, what proteins it makes, and how they work, which leads to discovery of new medicines. Increasingly knowledge about human genes help scientists come up with ideas of how to treat a disease.
Scientists who discover new medicines might work in universities, in research labs run by charities or research councils, in small biotechnology companies or in the laboratories of large pharmaceutical companies. However, wherever they work, they are aiming for the same thing - to discover medicines to improve the health of patients.
There are a number of stages that a new medicine has to go through before it can be tested in people. And once it has been shown to be safe enough to use in man it then has to go through three stages of clinical trials before the company has enough information on the medicine's safety, quality and effectiveness (efficacy) to apply for authorisation to market the medicine so that it can be prescribed by a doctor.
The stages are explained in more detail in the timeline below.
This chart can be downloaded here.
Most medicines being developed by pharmaceutical companies never make it through the research and development process to become marketed medicines.
There are many reasons for this. Some are found to be toxic when given to animals, or to have too many side effects when taken by volunteers or patients. Others just don't work as well as had been expected. New medicines are expensive because of the high cost of development and the high likelihood of failure.
For every 25,000 chemical compounds tested, on average 25 of these will have gone into clinical trials and five received approval for marketing. And only one will make enough money to pay for its development.