Clinical trials are used to evaluate potential treatments that have had some effect against disease in the lab, or in animal experiments. The whole point of a clinical trial is to find out if a treatment is effective.
Until sufficient results are available from many different trials, this potential is just that - potential. The effectiveness of a treatment should never be at the expense of safety; the benefit of a treatment must always outweigh the potential risk and this principle is fundamental to the conduct of all clinical trials.
The aim of clinical trials is to determine if a treatment works and is safe. By comparing similar groups of people taking different treatments for the same disease it is possible to show whether any benefits are due to the treatment. Effective treatments identified in this way may then become standard practice. Since the research is experimental, those who take part in early studies may not always benefit.
Different phases in clinical development
Clinical trials are conducted in a series of steps, called phases.
Preclinical trials are early experiments performed in the lab, prior to being tested in humans. This early research helps to identify potential treatments that are unsafe or ineffective.
Phase I trials are the first step in testing a new approach in humans. In these studies, researchers evaluate what dose is safe, how a new agent should be given (by mouth, injected into a vein, or injected into the muscle, for example), and how often. Researchers watch closely for any harmful side effects. Phase I trials usually enroll a small number of healthy volunteers or patients and take place at only a few locations.
Phase II trials study the safety and effectiveness of an agent or intervention, and evaluate how it affects the human body. Phase II studies usually focus on a particular medical condition.
Phase III trials compare a new agent or intervention (or new use of a standard one) with the current standard therapy. Participants are randomly assigned to the standard group or the new group, usually by computer. This method, called randomization, helps to avoid bias and ensures that human choices or other factors do not affect the study's results. In most cases, studies move into Phase III testing only after they have shown promise in Phases I and II. Phase III trials may include hundreds of people across the country or globally.
Phase IV trials are conducted to further evaluate the long-term safety and effectiveness of a treatment. They usually take place after the treatment has been approved for standard use. Several hundred to several thousand people may take part in a Phase IV study. These studies are less common than Phase I, II, or III trials.
Basic principles for conducting a trial
Research with people is conducted according to strict scientific and ethical principles. Every clinical trial has a protocol that acts like a "recipe" for conducting the trial. The protocol describes what will be done in the study, how it will be conducted, and why each part of the study is necessary. The same protocol is used by every doctor or research center taking part in the trial.
To ensure the safety of those in the study various approvals are required; these vary depending on the country but usually include a central review by a government department and also locally. The review ensures participants are treated humanely and ethically and whether the likely benefit of the treatment is worth its risk.
Inclusion in a trial is not a simple case of just joining in. Participants must fully understand the consequences; informed consent is the process by which people learn the important facts about a clinical trial to help them decide. This information includes details about what is involved, such as the purpose of the study, the tests and other procedures used in the study, and the possible risks and benefits.
What happens after the trial
After a clinical trial is completed, researchers look carefully at the data collected during the trial before making decisions about the meaning of the findings and further testing. After a Phase I or II trial, the researchers decide whether to move on to the next phase, or stop testing because it was not safe or effective. When a Phase III trial is completed, the researchers look at the data and decide whether the results have medical importance.
The results of clinical trials are often published in peer-reviewed, scientific journals. Peer review is a process by which experts review the report before it is published to make sure the analysis and conclusions are sound. If the results are particularly important, they may be featured by the media and discussed at scientific meetings and by patient advocacy groups before they are published.
Once a new approach has been proven safe and effective in a clinical trial, it may become standard practice. Standard practice is a currently accepted and widely used approach and would require approval by a government body such as the FDA or EMEA.
Clinical trials are sponsored by private organizations and government agencies.