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Clinical Trial Stages
There are 3 main phases of clinical trials – phases 1 to 3. But some trials have an earlier stage called phase 0, and there are some phase 4 trials done after a drug has been licensed.
Phase 1 trials
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 cancer.
When laboratory testing shows that a new treatment might help treat cancer, phase 1 trials are done to find out
- How much of the drug is safe to give
- What the side effects are
- How the body copes with the drug
- If the treatment shrinks the cancer
Patients are recruited very slowly onto phase 1 trials. So although they don’t recruit many patients they can take a long time to complete. The first few patients to take part (called a cohort or group) are given a very small dose of the drug. If all goes well, the next group have a slightly higher dose. The dose is gradually increased with each group. The researchers monitor the effect of the drug until they find the best dose to give. This is called a dose escalation study.
In a phase 1 trial you may have lots of blood tests because the researchers look at how the drug affects you. They also look at how your body copes with, and gets rid of the drug. They record any side effects.
People taking part in phase 1 trials often have advanced cancer. They have usually had all the treatment available to them. They may benefit from the new treatment in the trial but many won’t. Phase 1 trials aim to look at doses and side effects. This work has to be done first, before we can test the potential new treatment to see if it works.
Phase 2 trials
Not all treatments tested in a phase 1 trial make it to a phase 2 trial. Phase 2 is sometimes written as phase II. These trials may be for people who all have the same type of cancer or for people who have different types of cancer.
Phase 2 trials aim to find out
- If the new treatment works well enough to test in a larger phase 3 trial
- Which types of cancer the treatment works for
- More about side effects and how to manage them
- More about the best dose to use
Although these treatments have been tested in phase 1 trials, you may still have side effects that the doctors don’t know about. Drugs can affect people in different ways.
Phase 2 trials are often larger than phase 1. There may be up to 100 or so people taking part. Sometimes in a phase 2 trial, a new treatment is compared with another treatment already in use, or with a dummy drug (placebo). If the results of phase 2 trials show that a new treatment may be as good as existing treatment, or better, it then moves into phase 3.
Most phase 2 trials are randomised. This means the computers put the people taking part into treatment groups at random (by chance).
Phase 3 trials
These trials compare new treatments with the best currently available treatment (the standard treatment). Phase 3 is sometimes written as phase III. Phase 3 trials usually involve many more patients than phase 1 or 2. This is because differences in success rates may be small. So, the trial needs many patients to be able to show the difference.
Sometimes phase 3 trials involve thousands of patients in many different hospitals and even different countries. Most phase 3 trials are randomised. This means the researchers put the people taking part into treatment groups at random.
You must be prepared to be allocated into groups which will influence which treatment you receive.
Phase 4 trials
Phase 4 trials are done after a drug has been shown to work and has been granted a licence. Phase 4 is sometimes written as phase IV. The main reasons for running phase 4 trials are to find out
- More about the side effects and safety of the drug
- What the long term risks and benefits are
- How well the drug works when it’s used more widely
How do drugs get approved for use on the NHS?
A drug is given a license by the European Medicines Agency (EMA) and then a UK license by the Medicines and Healthcare products Regulatory Agency (MHRA) once it is deemed safe to use in a certain group of patients, and has shown to be of some benefit.
Drug manufacturers generally submit applications for licenses once the results of clinical trials are published. This process can take up to a year.
Once a drug is licensed, the National Institute of Health and Care Excellence (NICE) and the Scottish Medicines Consortium will, if asked, assess whether the drug should be used by the NHS.
They look at the clinical and cost effectiveness of the drug. In other words, does the drug in question work better than standard treatments offered (either for all patients, or for a particular group of patients)? Is the price to the NHS acceptable for the amount of benefit seen?
This process can take some considerable time, and countries within the UK may reach different conclusions.
This means it can take up to two years, or more, from results of trials being announced to the drugs being approved for use on the NHS.
Would you like to find a clinical trial?
If you would like to find a clinical trial click here go to our research page and use our Clinical Trial finder app. Please remember to talk to your consultant as they will need to recommend you for any trial you find. And please remember, not everyone is suitable to join clinical trials.