Drugs only become available for use after years of research and development.
Before a drug is widely prescribed by the NHS, it must have a license and in most cases, an independent advisory body must recommend it.
Across most of the UK, local health bodies use guidance produced by the National Institute for Health and Clinical Excellence (NICE) to decide which drugs to make available through the NHS.
Clinical trials are research studies to determine whether drugs or treatments are both safe and effective for humans.
All new medications and devices must undergo several clinical trials, usually involving thousands of people, before they can be released to the public.
Evidence from clinical trials helps identify which treatments work best. Without this evidence, there is a risk that people could be given treatments that have no advantage, waste NHS resources and might even be harmful.
Clinical trials research is not just for researchers. Patients and the public can be involved too.
New research cannot lead to reliable findings unless the right patients agree to join in.