What types of clinical trials are there?

Before any new treatment for pancreatic cancer is tested on humans in a clinical trial, it is thoroughly tested in a laboratory.

Watch our video to find out about the types of clinical trials.

All clinical trials must also be approved by an independent ethics committee and by government agencies. They check that the trial will be carried out in a safe way. There is more information about this on the  NHS website.

The new treatments being tested must then pass through several different types of clinical trials, known as phases. Each phase involves more people.

Find out about the different phases.

• Phase 1 trials
• Phase 2 trials
• Phase 3 trials
• Phase 4 trials

Phase 1 trials

Phase 1 trials are the first stage in testing a new treatment on people. Phase 1 drug trials for cancer in the UK usually involve a small number of people (around 10–30). They may have different types of cancer. The aim is to find out:

• the safe dose of a drug and how often it can be given
• what the side effects might be
• how well people’s bodies cope with the drug
• signs that the drug may have an effect on the cancer.

Phase 1 trials usually take place at specialist cancer centres. This may mean you need to travel to another hospital if the trial is not available in your local hospital.

There may be a waiting list to join the trial. Your doctor or nurse will be able to advise you on this. 

Phase 2 trials

If the results of a phase 1 trial are good, the treatment will move to a phase 2 trial. A phase 2 trial usually involves more people – there may be around 100 people taking part.

In a phase 2 trial, the research team already know which dose to use from the phase 1 trial results. They now want to learn more about how effective this treatment may be for specific types of cancer.

A phase 2 trial will also look at:

• whether the new treatment works well enough to test it in an even bigger trial (a phase 3 trial)
• gathering more information about what dose to use
• how the treatment affects people’s quality of life
• understanding more about the side effects and how to manage them.

If the results of the phase 2 trial are good, the treatment may move into a larger phase 3 trial.

Phase 3 trials

Phase 3 trials compare new treatments with the best treatment currently available. They can do this by directly comparing a new treatment with an existing one, or by comparing different doses or different ways of giving the treatment.

A phase 3 trial will also look at:

• how effective the treatment is
• any side effects
• the impact on a person’s quality of life
• any other problems that could develop, to learn more about how to provide the treatment safely.

Most phase 3 trials are randomised controlled trials (RCTs) and usually involve many more people than phase 2 studies. Larger numbers of people are needed so that even small differences in results can be seen more easily, which means the results of the trial will be more reliable. Some phase 3 trials are blinded trials.

A new treatment usually has to show better results than the standard treatment before it can be introduced as a treatment on the NHS. Sometimes, a treatment needs to be tested in several trials before it is introduced. But if the trial is big enough and the results are good, several trials may not be needed.

Phase 4 trials

Phase 4 trials are usually carried out soon after new drugs have passed all the previous stages and have been licensed for use in the UK. Phase 4 trials aren’t needed for every drug.

Phase 4 trials aim to find out as much as possible about how safe the drug is by monitoring very large numbers of people. They also look at how well the drug works, learn more about side effects and what the long term risks and benefits are for people taking part. Phase 4 trials can also provide more information on the cost of the new treatment.

Published January 2025

Review date January 2028