Clinical trials: The phases
Clinical trials are conducted by physicians or hospital teams and proceed along 3 successive phases:
At this point, the compound is tested mainly on a limited number of healthy subjects*, who may receive compensation and are under strict medical supervision. The compound is tested over a short period of time. The purpose is to evaluate the product’s safety, how it evolves within the body, the tolerance threshold and adverse events.
Testing involves larger groups of patients. The purpose is to test the product’s efficacy and determine optimal dosage regimen. These studies are usually comparative: one of two groups of patients is administered the product whereas the other group is given a placebo.
Testing involves large number of patients, with the purpose of comparing the therapeutic efficacy of the compoundto a reference treatment (if there is one) or to a placebo (when there is no alternative therapy). Such studies are very frequently multicentric (i.e. involving many study centres). Generally, neither the patient, nor the medical profession are aware of what each patient is being treated with (double blind trial): this is to avoid any bias or prejudiced opinion on either side regarding efficacy or adverse events.
* Patients are recruited to phase I studies especially in cases such as cancer therapies.
Once these 3 phases have been successfully completed, the resulting data, together with the results of preclinical testing, are collected to compose a registration file that will be submitted to public health authorities for license to market.
Trials do not cease once the pharmaceutical has been put on sale; they continue throughout its marketing life.Trials called Phase IV, are carried out after approval in conditions close to those of usual medical care. Specific targets at this point are to detect possible rare undesirable side effects which had escaped attention in the previous phases (pharmacovigilance) and to define conditions of use for certain groups of at-risk patients.
During this phase, drug interactions can be listed and new galenic forms and therapeutic indication extensions can be developed.