Phase III clinical studies of medicinal products are conducted on large groups of patients, usually thousands of patients participate in the studies. This carefully controlled study is conducted with the view of maximal and comprehensive assessment of safety and efficacy of the drug during its medical use after launch onto the pharmaceutical market. Moreover, in some cases, given the vast population of patients with different comorbidities, detection of positive or negative effects of the drug not previously defined, is possible. For example, during the phase III studies of doxazosin, the drug designed to treat arterial hypertension, positive effect on the correction of benign prostatic hyperplasia in men was detected. The results were so representative, convincing and statistically significant, that the treatment of prostatic hyperplasia became predominant indication for the use of doxazosin.
Most often this phase of clinical studies is called pre-registration, that is conducted with the purpose of registration of the drug.
Recommendation to wide clinical use is considered justified if in the course of studies it was demonstrated that the new drug:
- is more efficient than the known drugs of similar action, or the “gold standard” for treatment of a disease
- has better tolerance and safety than known drugs of its group while having equal efficacy
- is effective in cases when treatment with other known drugs is not effective
- is easy to use
- has a more convenient dosage form
- is used in combination with other drugs without changes to safety parameters
Phase III clinical studies are sometimes divided into phases a and b.
Phase IIIa studies are conducted when efficacy of the drug was proven, before the submission of reports to regulatory organs. These clinical studies are conducted in specific target groups of patients with pathology the treatment of which is targeted by the drug under study. The data obtained in Phase IIIa may also include economic assessment of treatment methods and assessment of quality of life. These data may be useful for making decision on the inclusion of the drug in various lists, tenders, formularies.
Studies of Phase IIIb are clinical studies conducted prior to receiving approval for a drug and its mass manufacturing. Information obtained in this phase of studies complements the final results of the studies.
The phase III studies clarify characteristics of the drug and detect relatively rare adverse reactions, therefore, information on the safety of the drug under study is supplemented.