What is a clinical trial?

A clinical trial is a research study where people are invited to try a new medicine. Clinical trials test if a new medicine works and if it is safe.

Before a new medicine can be tested in a clinical trial, it must first be tested in the laboratory. This is done to make sure that it is safe to test the medicine in people. New medicines are typically tested in 4 phases:

Phase 1:
Testing the safety of a new medicine in a small group of people – most often healthy people, but sometimes people with a certain disease. When the trial doctors and researchers are sure the medicine is well tolerated, it can go to phase 2.

Phase 2:
Testing the new medicine in a larger group of people with a certain disease. In this phase, the medicine is often tested for a longer time than in phase 1. This is done to see if or how the medicine works – also known as the ‘efficacy’ of the medicine.

Phase 3:
Testing the medicine in even larger groups of people with a certain disease. In this phase, the new medicine is compared with a standard medicine used for the disease, or with placebo. Placebo is a dummy medicine that looks, feels, or tastes like the trial medicine but does not have any medical ingredients.

Phase 4:
Testing a medicine that has already been approved for use. Phase 4 trials include the largest group of people taking part. Phase 4 trials are also sometimes called post-marketing surveillance trials.

All clinical trials have a detailed plan for how the trial should be done – a kind of ‘recipe’ for the trial doctors. This plan is called the trial protocol.

The trial protocol describes:

  • which people may take part in the trial
  • how people that take part will be treated and looked after
  • how long the trial will take
  • how the results will be measured.

Before a trial can start, an independent ethics committee and the local government’s health authorities must approve the trial protocol.

Clinical trials will only take place, if there are more benefits than risks for the people taking part. There must also be a scientific and medical reason for the trial.