To guarantee safety of patients and meet scientific demands of ever more complex research, clinical trials now consist of several stages or phases, each of which contain specific information:
- Phase I trials
- Phase II trials
- Phase III trials
Phase I trials : During a phase I trial, experimental treatment is given to a small number of patients (10-40). The treatment has already been tested in laboratories on cell cultures and animals, but nobody yet knows how human beings will react to it. Doctors search for the best way of administering the treatment, with full patient safety, and watch carefully should any side effects appear.
When the medicines in question are a priori not greatly toxic (anti-hypertensive, stomach antacids etc), phase I is often conducted on healthy subjects. These are people in good health who devote time to clinical research and to new developments in the pharmaceutical industry. If you require more information on the possibility of participating in a clinical trial as a volunteer, talk to your GP, who will refer you to the appropriate research units.
When more toxic drugs (such as anti-cancer drugs) are involved, administration of the product in phase I is dedicated to patients whose condition is advanced and for whom no known treatment is effective. Although the therapeutic effect is unknown during phase I, patients have been helped through their participation to the trial.
Phase II trials : aim to study the efficacy of a given medicine in a very specific condition. In addition to immediate efficacy, phase II also tests safety of experimental treatment. Phase II generally requires 40-80 patients to participate.
Phase III trials : If the phase II trials suggest that the treatment is effective, the researchers go on to phase III, that is, comparing the new treatment with the best known treatment (or standard treatment). If there is no alternative treatment, the new molecule is compared to a placebo (a simple sugar coated pill or an injection of physiological serum for treatments involving injections).
Even slight differences in efficacy can be very significant: for example, an improvement of only 5% in survival rates for an anti-cancer medicine means several thousand human lives saved in Europe alone. Phase III trials are held on a large scale (several hundreds or even thousands of patients).
Phase III is a crucial stage, as it precedes the marketing and provision of new, more effective and/or less toxic treatments. New medication can also be combined with other medicines, surgery and/or radiotherapy, in new treatment procedures that further improve patients' survival and/or quality of life.