How New Drugs Are Discovered and Developed
Learn how new drugs are discovered, tested in preclinical studies and developed through clinical trials for AQA GCSE Biology examinations.
New drugs are discovered from natural substances or synthesised by chemists. They are then tested in preclinical studies and clinical trials to check their toxicity, efficacy and optimum dose.
This answer assumes AQA GCSE Biology Higher tier and separate science, although the content explained here is assessed at both tiers and is also shared with Combined Science.
Discovering potential medicines
Traditionally, useful drugs were discovered in plants and microorganisms. Examples include:
- digitalis, a heart drug originating from foxgloves
- aspirin, a painkiller originating from willow
- penicillin, discovered by Alexander Fleming from Penicillium mould
Most new drugs are now synthesised by chemists in the pharmaceutical industry, although development may begin with a chemical found in a plant.
Preclinical testing
Before a drug is tested on humans, it undergoes preclinical testing in a laboratory. It is tested using:
- cells
- tissues
- live animals
These tests investigate:
- toxicity — whether the drug is poisonous or causes harmful effects
- efficacy — whether the drug produces the intended effect
- dose — the amount that should be given
Clinical trials
If preclinical testing is successful, clinical trials are carried out using healthy volunteers and patients.
Very low doses are given at the start to reduce risk. If the drug is found to be safe, further trials determine its effectiveness and the optimum dose—the dose that gives the best effect with acceptable side effects.
Some patients may receive a placebo, which looks like the drug but contains no active medicine. This allows researchers to compare results fairly.
In a double-blind trial, neither the patients nor the doctors assessing them know who receives the drug or the placebo until the results have been collected. This reduces bias.
Common exam mistake
Do not say that drugs are tested on humans immediately. Preclinical testing using cells, tissues and live animals happens before clinical trials. Also remember that efficacy means how well the drug works, not how safe it is.
