Developing new medicinesSpec 5.20
In short
Developing a new medicine has four stages: discovery, development, preclinical testing and clinical testing. In preclinical testing the medicine is tested on cells, tissues and then live animals to check whether it is toxic and whether it works. In clinical testing it is given first to a few healthy volunteers, then to patients to find the right dose.
Developing a new medicine, including a new antibiotic, takes many stages. Each stage checks that the medicine is safe and that it works.
- Discovery: finding a chemical that might treat the disease. These may come from natural sources, such as plants or microorganisms, or be designed in a laboratory.
- Development: the chemical is studied and improved, and a way to make it as a medicine is worked out.
- Preclinical testing: the medicine is tested in the laboratory on cells and tissues, and then on live animals, to find out if it is toxic and whether it works.
- Clinical testing: the medicine is tested on people. It is first given to a small number of healthy volunteers to check it is safe, then to patients to check that it works and to find the right dose.
Only a medicine that passes all the stages can be used to treat patients. The testing protects people from harmful or ineffective medicines.
Learn the four stages in order: discovery, development, preclinical, clinical. Preclinical comes before any testing on humans.
Quick check
Why can antibiotics not be used to treat viral infections?
Show answer
Antibiotics inhibit cell processes in bacteria; viruses are not cells and reproduce inside host cells.
Triple only: why is an inoculating loop heated in a flame before use?
Show answer
To sterilise it by killing any microorganisms on it.
Triple only: in the core practical, what does a larger clear zone show?
Show answer
The substance is more effective at stopping bacteria growing.
Name the four stages in developing a new medicine in order.
Show answer
Discovery, development, preclinical testing, clinical testing.
Triple only, Higher tier: what is a hybridoma cell?
Show answer
A cell made by fusing an antibody-producing lymphocyte with a tumour cell; it divides and produces antibodies.
Written and checked against the Edexcel GCSE Combined Science (1SC0) specification · Updated October 2026