What types of clinical trial are there? 

For a treatment to enter everyday use – it must pass through different types of clinical trial.

Phase I studies

These are the first time the treatment is tested in people.
They are usually small trials recruiting only a few patients and may be open to people with any type of cancer.
The first few patients are given a very small dose and then providing there are not too many side effects the next group are given a slightly higher dose.
These studies usually have a complex design and include lots of blood tests and clinical measurements.
People taking part in Phase I trials often have advanced cancer and have usually had all the treatment available to them. They may benefit from the new treatment but many won’t.

They aim to find out:

  • The safe dose range
  • What type of side effects
  • How the body copes with the drug
  • Does the treatment shrink the cancer

Phase I trials at UCLH are conducted at the NIHR/Wellcome UCLH Clinical Research Facility.

Phase II studies

These are usually larger than Phase I trials with up to 100 people taking part.

Phase II studies aim to find out:

  • If the new treatment works well enough to test in a larger Phase II trial
  • What type of cancer the treatment works for
  • More about side effects and how to manage them
  • More about the best dose

Sometimes in a phase II trial, a new treatment is compared with another treatment already in use, or with a dummy drug (placebo).

If the results of phase II trials show that a new treatment may be as good as existing treatment, or better, it then moves into phase III (3).

Phase III studies

These trials compare new treatments with the best currently available treatment (the standard treatment). Phase 3 is sometimes written as phase III. These trials may compare:

  • A completely new treatment with the standard treatment
  • Different doses or ways of giving a standard treatment
  • A new way of giving radiotherapy with the standard way

If the differences between the new treatment and the existing treatment are small, hundreds of patients may need to take part before one is identified as better than the other. Studies may take place in several different hospitals at the same time, including hospitals in other countries.

What is a clinical trial?
The research team
Current (open) clinical trials
Contact the clinical trials team