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About Clinical Studies
A clinical trial is a study of a drug or treatment that involves people who volunteer to participate in the trial. Depending on the type of study, clinical trials may enroll healthy individuals or people with a specific medical condition. Initially, small studies are done, and as positive safety data is gathered, the number of patients is increased. Each study is divided into phases to determine if a new treatment can be licensed. In the United States, a drug can only be licensed by the Food and Drug Administration (FDA). It is this organization that defines the specific medical conditions for which a drug may be prescribed.
Pre-clinical Trials
Treatments are thoroughly tested in laboratory trials before they are ever tested with groups of patients. These trials sometimes involve animals to provide important information about the toxicity and safety of an experimental compound. If the results from pre-clinical studies are encouraging, a drug is next tested in clinical studies.
Phase 1 Trials
Phase 1 clinical trials focus primarily on the safety and pharmacokinetics of the drug in question – that is, on how the drug is distributed throughout the body and how the body metabolizes the drug. These studies help researchers determine where the drug becomes concentrated after it is taken and how long it lasts in the blood stream. These trials are also done to determine safe dosage ranges, possible side effects, how the body tolerates the drug, and whether the treatment shows signs of being effective against the disease.
These are usually small trials, recruiting up to 30 patients, but often less. The trial may be open to people with any type of disease. Such trials last a short time, typically a few weeks to a few months.
In a phase 1 study, the first patient to take part will be given a very small dose of the drug. If all goes well, the next person will get a slightly higher dose. With each patient taking part, the dose will gradually be increased and its effect will be monitored. Any side effects will be recorded. In a phase 1 trial, an individual may have a lot of blood tests as the researchers look at how the drug is affecting them.
Phase 1 trials are important because they are an early step in finding new treatments for the future. About 70 out of every 100 new treatments tested in this phase progress to phase 2 trials.
Phase 2 Trials
Phase 2 trials focus on the effectiveness of a drug as a treatment for a particular disease. They are larger than phase 1 trials and usually have a longer duration. These trials may include people who have the same type of disease or several different types of a particular disease.
Phase 2 trials provide additional information about a drug or therapy's safety in addition to new information about its efficacy, or how well the drug works. They also tell researchers about possible side effects and how to manage them, and they provide information about which dose is most effective.
Trials may be designed to demonstrate a drug’s safety and effectiveness in a series of specific cases, or it may be a randomized study that compares two or more groups. In a randomized study, not all participants receive the experimental drug. Two or more groups are created that are as similar as possible. One group may get the standard treatment or a placebo for the disease as a “control” group, while the other receives the new drug. This way, researchers can be reasonably sure that differences between the groups are due to the drug.
Normally if Phase 2 trials show good results, Phase 3 trials are then required before new drugs, doses or drug combinations can be licensed.
Phase 3 Trials
Phase 3 trials compare new treatments with the standard or best available treatment. They may also test different doses or ways of giving a standard treatment.
Phase 3 trials are usually much larger than phase 1 and 2 trials. This is because differences in success rates may be so small that you need many results to show the difference. Sometimes phase 3 trials involve thousands of patients in many different hospitals and even different countries.
These studies are usually randomized. This means the researchers put the people taking part into 2 groups at random. One group gets the new treatment and the other the standard treatment. To ensure objectivity, trials are often blinded so that patients do not know which drug (or dose) they are receiving. Some studies are double-blind which means that no one, not even the researchers conducting the trial, knows who is getting which drug until the end of the trial.