Clinical trials are defined as research studies performed in human beings to provide evidence of the efficacy and long term safety of pharmaceutical products (drugs) and that follow very strict worldwide rules and regulations. These studies are divided into three phases (Phase I trials, Phase II trials and Phase III trials), all of which are necessary prior to Marketing Authorization for the drug by competent regulatory authorities such as the Food and Drug Administration (FDA) in the United States or equivalent regulatory authorities in other countries. Participation of patients in any of these phases of clinical trials is voluntary and a participant can discontinue their involvement at any time without harming his/her future medical treatment.
Before any research in humans is conducted, the pharmaceutical product is extensively tested in relevant animal species to demonstrate its efficacy and safety. These studies, as well as the manufacturing of the pharmaceutical product for use in clinical trials, are highly regulated to ensure the lowest risk for humans.
Phase I clinical studies are the first test of the pharmaceutical product in humans and involve a low number of volunteers. The objective is to evaluate the safety and toleration of the pharmaceutical product and the doses that would be studied in the following Phase II study. The pharmacokinetics of the product (including absorption, distribution and elimination within the body) are also characterized. In some cases it is also possible to obtain preliminary information on the efficacy of the product. For anticancer products these studies are conducted in cancer patients. For other products, this phase is usually conducted in healthy volunteers.
Phase II clinical studies are designed after confirmation of the initial safety in Phase I trials and involve a larger group of participants. The aim is to assess the short-term efficacy in the target patient population and as well further evaluating the safety of the pharmaceutical product. These studies may involve the evaluation of a range of doses, combination of therapies compared with single therapies alone, different dosing regimens, etc.
Phase III clinical studies involve large patient groups and are aimed at being the definitive assessment of the long term efficacy and safety of the pharmaceutical product in comparison with placebo (no treatment) or current standard of care treatments. Due to the length of these studies and the number of patients involved, they are the most expensive, time-consuming and difficult trials to design and run, especially in therapies for chronic or life threatening medical conditions such as cancer.
Once a pharmaceutical product has proved to be efficacious and safe at the end of Phase III, all of the results from human and animal studies are combined into a registration dossier which is submitted to regulatory authorities for Marketing Authorization. If the Marketing Authorization is approved then the drug becomes available as a treatment for patients.
Following approval and in order to gather additional information for different purposes, Phase IV clinical studies may also be conducted.
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