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Clinical trials may also be called clinical studies or just ‘trials’. Here we describe clinical trials that are used in the development of medicines. Clinical trials can also be used to develop methods for the diagnosis and prevention of illnesses.
Our information on clinical trials will help you talk with your doctor or medical team about your condition and the possibility of taking part in a clinical trial. Participating in a clinical trial may not directly benefit you, but it may help others who need treatment at a later time; this is how treatments that were once experimental have become standard practice.
This information should not be used as a substitute for professional care.
Clinical trials are medical research studies involving people. They provide answers to scientific questions. Clinical trials are carried out to test new medicines or to look at new aspects of existing medicines.1, 2, 3
Medicines take many years to develop, from identifying a promising chemical compound in the laboratory to it being available for patients. Clinical trials are part of a long development process that ends with a medicine being licensed for use by people. The main stages are shown below:7
Clinical trials provide one of the most reliable and effective ways of developing new medicines. They provide evidence for doctors to see if a new treatment:
Clinical trials may also be used to collect information on an existing treatment that is being used in a new way or to treat more medical conditions. Carrying out clinical trials is the only way to find out if a new approach to cancer care is better than the standard treatments currently used.1 Without clinical trials, there is a risk that patients could be given treatments which provide no advantage or might even be harmful to them.1 Clinical trials that look at different cancer treatments are the only reliable way to find out if a different option, or type of chemotherapy or radiotherapy, is better than that which is already available.
Clinical trials can be divided into four main types depending on the phase of development of the medicine or method:
Phase 1: this is usually the first stage and involves small numbers of healthy people or, in the case of cancer clinical trials, small numbers of patients whose cancer has come back or spread and there is no other standard treatment available that may help them. Phase 1 trials are normally performed to find out how safe a medicine or technique is. For cancer treatments, Phase 1 clinical trials test a drug or treatment that has already been tested in the laboratory on cancer cells, and Phase 1 is the first stage in which the drugs are given to people. The new treatment is not expected to cure the cancer, but the aims of the trial are to see if the treatment has an effect on the body, how much treatment can be given safely, what side effects (if any) it causes and to see if the treatment has any effect on the cancer.
Phase 2: these are usually performed after Phase 1 trials and involve more people, usually patients who have the medical condition that the new medicine is being developed to treat. Phase 2 trials collect more information on the safety of the medicine, and may also look at the effectiveness of the medicine in treating a specific medical condition.
Phase 3: these trials are generally very large, involving hundreds and sometimes thousands of patients, often at several research centres or hospitals around the world. Phase 3 trials are carried out to collect additional information in a much broader population of patients to get an even better understanding of the safety and effectiveness of the medicine. If the information from the Phase 3 trials shows that the medicine works and has a good safety profile, then it is given a licence and will be available for patients to use.
Phase 4: these are carried out after a medicine has been shown to work and has been given a licence. Phase 4 trials provide more extensive information about the medicine – possibly to treat a broader range of patients or illnesses.
Within the four phases described above, clinical trials can be further sub-divided. You may hear the following terms being used to describe the different designs of clinical trials:
Controlled trials: clinical trials often look at more than one treatment so they may compare the new medicine against a standard medicine that is already licensed. Those people in the trial who are assigned the new medicine may be called the trial treatment group; those people who are assigned the standard treatment are called the control group. The control group is necessary to be able to compare the new medicine to see how safe and effective it is.
Placebo: some trials may compare the new medicine with a placebo – in cancer trials, placebo is used when there is no standard treatment to compare with the trial treatment. A placebo is an inactive or ‘dummy’ treatment. During a trial, those people who are assigned to take the placebo are called the placebo group and a trial containing placebo is often called a placebo-controlled trial.
Randomisation: this is a process by which people are assigned to the different treatments when they take part in a clinical trial. The randomisation process is usually done by a computer. It assigns each person to a trial treatment, or sequence of trial treatments, randomly, like tossing a coin. Randomisation is done so that the researchers and doctors cannot choose who gets what treatment, which could introduce bias and therefore make the results unreliable.
Blinded trials: in a blinded trial, the people taking part are not told what treatment they are being given and therefore which treatment group they are in. If a trial is double-blind, then neither the participant nor the researchers or doctors know what treatment is assigned to whom. This is another way of preventing bias in a clinical trial. For example, knowing what treatment a person is taking may influence whether they feel positive or negative. Similarly, if the doctor knew the assignment then it may influence how they report the participant’s responses.
You can also have a combination of these different trial types, so you may hear of a randomised controlled trial, or a double-blind placebo-controlled trial.
People who take part in clinical trials may be called ‘trial participants’ or ‘subjects’. They can be healthy individuals or patients, depending on the type of clinical trial and what medicine is being investigated.
All clinical trials have guidelines describing who can participate. These guidelines are called eligibility criteria. They may also be called ‘inclusion and exclusion criteria’. They help the researchers to decide who can and can’t take part in the clinical trial. This ensures that the right people take part so that the benefits of the medicine under investigation can be properly tested.
If someone chooses not to take part in a clinical trial, then they will still get the best standard treatment available for their condition, so there is no disadvantage if someone doesn’t want to take part. Doctors will regularly monitor trial participants during the clinical trial, for example, by taking blood samples, and they will ask the trial participant questions to find out how they are feeling. This means that any changes to a subject’s health – whether or not these changes are related to the treatment being given – can be noticed and dealt with earlier than if they weren’t taking part in a trial.
Trials are designed to minimise any risks to the people taking part and to ensure the best quality information is obtained. Clinical trials are reviewed and approved by ethics committees and regulatory agencies before they can begin. In the UK, clinical trials are approved, and new medicines are licensed, by the Medicines and Healthcare Products Regulatory Authority (MHRA). Legal standards, set by the European Union Clinical Trial Directive (2004), must also be met for clinical trials carried out in the UK.
These stringent processes and regulations are in place to protect the rights, dignity, safety and well-being of the participants. Anyone taking part in a clinical trial must be given clear information and have the opportunity to ask questions about the trial, including potential risks and benefits, before they give their consent. Participation is entirely voluntary so that anyone can stop taking part in the trial at any point at their own choice. Trial participants are looked after and monitored throughout the trials.
The duration of clinical trials varies with some taking years to complete while other take a few weeks or months. At the end of a clinical trial, all the information is gathered together and analysed to look at the safety and effectiveness of the medicine, including any side effects. This also enables researchers to find out what doses of medicine are needed and how often it should be taken. Researchers are obliged to make this information available, for example, by presenting at scientific or medical conferences, or publishing in journals and sometimes the mainstream press. Sometimes, researchers work with charities, like Brain Tumour UK, to make sure that the information reaches those patients most likely to benefit.
Many different types of organisations support clinical trials including:
Version 1.2 14 August 2012 - Review date: 14 August 2014
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