What are the different phases of a Clinical Trail ?
Before a new treatment can become part of standard treatment it needs to go through a series of testing in what are called ‘phases‘. Following on from trials using animals, the main aim of early phase trials is to test if the treatment is safe for humans. Later phase trials investigate if the treatment is more effective than the currently available standard treatment. You may be asked to participate in any one of these phases of testing if you decide to take part in a clinical trial.
Phase 0 trials
Phase 0 trials are the first-in-human studies for drugs that have been previously tested in animals. Usually a single drug dose is given to 10-15 people to gather preliminary data on how the drug is metabolised and what effect the drug has on the body. The dose of drug given is below what is thought to have a therapeutic effect.
Phase 1 trials
These are the first tests of a treatment in humans and involve approximately 15-30 people. They aim to see if the trial treatment is safe and to find the best dose. The research team notes major and minor side effects. This helps researchers to work out the best dose and the best way to give the trial treatment.
Phase 1 trials are usually only suitable for people with incurable cancer who have had all the known effective treatments for their cancer. People take part in these trials in the hope that the treatment may extend their life or improve their quality of life. Most often though, the reason to enter Phase 1 trials is to help people with cancer in the future.
If a Phase 1 trial shows that the new treatment is safe it will go on to Phase 2 testing.
Phase 2 trials
Phase 2 trials usually involve less than 100 people. The trials aim to see how well the new treatment works against cancer and to monitor for side effects.
Phase 2 trials generally involve people who have already had cancer treatment. The chance of the treatment being tested in a Phase 2 trial being effective depends on the type and extent of the cancer and its response to previous treatment.
If the new treatment shows promising effects (efficacy) against cancer and is safe then it is tested in Phase 3 trials.
Phase 3 trials
Phase 3 trials involve from hundreds to thousands of people. The trials are usually conducted through doctors’ offices, hospital clinics and cancer centres around the country or even around the world. They aim to test if the new treatment (the intervention treatment) is better than the current best standard treatment. They test treatments in real life settings, not the controlled circumstances under which Phase 1 and 2 trials are usually conducted.
Participants in Phase 3 trials are put in either the new treatment group or the standard treatment group at random. People in the trial are monitored carefully to see the effect of the treatment on the cancer, and on the length and quality of life.
If the new treatment works better, it may become the new standard treatment. In general, the new treatment needs to go through more than one Phase 3 trial for the treatment results to be accepted.
Phase 4 trials
‘Phase 4 trial’ refers to the long-term monitoring that sometimes occurs after a drug has been licensed for use and put on the market. Phase 4 trials are to assess any long-term side effects of a new treatment. There are very few Phase 4 trials.