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Phases of clinical trials

Phases of clinical research

The phases of clinical research are the steps in which scientists do experiments with a health intervention in an attempt to find enough evidence for a process which would be useful as a medical treatment. In the case of pharmaceutical study, the phases start with drug design and drug discovery then proceed on to animal testing. If this is successful, they begin the clinical phase of development by testing for safety in a few human subjects and expand to test in many study participants to determine if the treatment is effective.

Phases of clinical trials

This page is about the different phases of clinical trials. It has information about

What trial phases are Trial phases at a glance Phase 0 trials Phase 1 trials Phase 2 trials Phase 3 trials Phase 4 trials Trials covering more than one phase

What trial phases are

Clinical trials testing new treatments are divided into different stages, called phases. The earliest phase trials may look at whether a drug is safe or the side effects it causes. Later phase trials aim to test whether a new treatment is better than existing treatments.

There are 3 main phases of clinical trials – phases 1 to 3. Phase 1 trials are the earliest phase trials and phase 3 are later phase trials.

Some trials have an earlier stage called phase 0, and there are some phase 4 trials done after a drug has been licensed.

Some trials are randomised. This means the people taking part are put into one of treatment groups at random. Doing this means the results are more reliable.

Phase 0 trials

Phase 1 trials are usually the earliest trials of drugs in people. But your doctor might ask if you would like to join a phase 0 study. These studies aim to find out if a drug behaves in the way researchers expect it to from their laboratory studies.

Phase 0 studies usually only involve a small number of people and they only have a very small dose of a drug. The dose of the drug is too small to treat your cancer, but you are also less likely to have side effects.

Phase 0 trials aim to find out things such as:

  • whether the drug reaches the cancer cells

  • what happens to the drug in the body

  • how cancer cells in the body respond to the drug

You might have extra scans and give extra samples of blood and cancer tissue (biopsies) to help the researchers work out what is happening.

Phase 1 trial

Phase 1 is sometimes written as phase I. They are usually small trials, recruiting only a few patients. The trial may be open to people with any type of advanced cancer, usually those who have already had all other available treatments.

Phase 1 trials aim to find out:

  • how much of the drug is safe to give

  • what the side effects are

  • how the body gets rid the of drug