Clinical trials are experiments or observations done in clinical research. Such prospective biomedical or behavioral research studies on human participants are designed to answer specific questions about biomedical or behavioral interventions, including new treatments (such as novel vaccines, drugs, dietary choices, dietary supplements, and medical devices) and known interventions that warrant further study and comparison. Clinical trials generate data on safety and efficacy. They are conducted only after they have received health authority/ethics committee approval in the country where approval of the therapy is sought. These authorities are responsible for vetting the risk/benefit ratio of the trial – their approval does not mean that the therapy is 'safe' or effective, only that the trial may be conducted.
Depending on product type and development stage, investigators initially enroll volunteers or patients into small pilot studies, and subsequently conduct progressively larger scale comparative studies. Clinical trials can vary in size and cost, and they can involve a single research center or multiple centers, in one country or in multiple countries. Clinical study design aims to ensure the scientific validity and reproducibility of the results.
Costs for clinical trials can range into the billions of dollars per approved drug. The sponsor may be a governmental organization or a pharmaceutical, biotechnology or medical device company. Certain functions necessary to the trial, such as monitoring and lab work, may be managed by an outsourced partner, such as a contract research organization or a central laboratory.
Only 10 percent of all drugs started in human clinical trials become approved drugs
Trials of drugs
Some clinical trials involve healthy subjects with no pre-existing medical conditions. Other clinical trials pertain to patients with specific health conditions who are willing to try an experimental treatment.
When participants are healthy volunteers who receive financial incentives, the goals are different than when the participants are sick. During dosing periods, study subjects typically remain under supervision for one to 40 nights.
Examples of clinical trial goals include assessing the safety and relative effectiveness of a medication or device:
On a specific kind of patient, for example, a patient who has been diagnosed with Alzheimer's disease
At varying dosages, for example, a 10 milligram dose instead of a 5 milligram dose
For a new indication
Evaluation for improved efficacy in treating a patient's condition as compared to the standard therapy for that condition
Evaluation of the study drug or device relative to two or more already approved/common interventions for that condition, for example, device A versus device B, or therapy A versus therapy B)
While most clinical trials test one alternative to the novel intervention, some expand to three or four and may include a placebo.
Except for small, single-location trials, the design and objectives are specified in a document called a clinical trial protocol. The protocol is the trial's "operating manual" and ensures that all researchers perform the trial in the same way on similar subjects and that the data is comparable across all subjects.
As a trial is designed to test hypotheses and rigorously monitor and assess outcomes, it can be seen as an application of the scientific method, specifically the experimental step.
The most common clinical trials evaluate new pharmaceutical products, medical devices (such as a new catheter), biologics, psychological therapies, or other interventions. Clinical trials may be required before a national regulatory authority approves marketing of the innovation.
Trials of devices
Similarly to drugs, manufacturers of medical devices in the United States are required to conduct clinical trials for premarket approval. Device trials may compare a new device to an established therapy, or may compare similar devices to each other. An example of the former in the field of vascular surgery is the Open versus Endovascular Repair (OVER trial) for the treatment of abdominal aortic aneurysm, which compared the older open aortic repair technique to the newer endovascular aneurysm repair device. An example of the latter is clinical trials on mechanical devices used in the management of adult female urinary incontinence.
Trials of procedures
Similarly to drugs, medical or surgical procedures may be subjected to clinical trials, such as case-controlled studies for surgical interventions.