Reference:WHO WHO - Guidelines for GCP for trials on pharmaceutical products* 1995 Glossary - clinical trial Phases

Document information
Reference	WHO WHO - Guidelines for GCP for trials on pharmaceutical products* 1995
Validity area	WHO
Scope(s)	HM
Document name	WHO - Guidelines for GCP for trials on pharmaceutical products*
Version / Revision	1995
Status	Current
Document type	International guideline
Language(s)	EN
Description	World Health Organization WHO Technical Report Series, No. 850, 1995, Annex 3 Guidelines for good clinical practice (GCP) for trials on pharmaceutical products*
Official source	Official link
Restricted access	No
Submitted by	Florian Adragna
Contributors

Reference Details
Module	Module 1 — Unit 1.2.5
Scope	HM
Document part	Glossary - clinical trial Phases
Language	EN
Original entry by	Florian Adragna
Contributors
Tags	Trial phase, Clinical trial, Healthy volunteer

Content

clinical trial [...] Clinical trials are generally classified into Phases I to IV. It is not possible to draw distinct lines between the phases, and diverging opinions about details and methodology do exist. A brief description of the individual phases, based on their purposes as related to clinical development of pharmaceutical products, are given below:

Phase I These are the first trials of a new active ingredient or new formulations in man, often carried out in healthy volunteers. Their purpose is to establish a preliminary evaluation of safety, and a first outline of the pharmacokinetic and, where possible, a pharmacodynamic profile of the active ingredient in humans.

Phase II These trials are performed in a limited number of subjects and are often, at a later stage, of a comparative (e.g. placebo-controlled) design. Their purpose is to demonstrate therapeutic activity and to assess short-term safety of the active ingredient in patients suffering from a disease or condition for which the active ingredient is intended. This phase also aims at the determination of appropriate dose ranges or regimens and (if possible) clarification of dose response relationships in order to provide an optimal background for the design of extensive therapeutic trials.

Phase III Trials in larger (and possibly varied) patient groups with the purpose of determining the shortand long-term safety/efficacy balance of formulation(s) of the active ingredient, and of assessing its overall and relative therapeutic value. The pattern and profile of any frequent adverse reactions must be investigated and special features of the product must be explored (e.g. clinically-relevant drug interactions, factors leading to differences in effect such as age). These trials should preferably be of a randomized double-blind design, but other designs may be acceptable, e.g. long-term safety studies. Generally, the conditions under which these trials are carried out should be as close as possible to normal conditions of use.

Phase IV Studies performed after marketing of the pharmaceutical product. Trials in phase IV are carried out on the basis of the product characteristics on which the marketing authorization was granted and are normally in the form of post-marketing surveillance, or assessment of therapeutic value or treatment strategies. Although methods may differ, these studies should use the same scientific and ethical standards as applied in premarketing studies. After a product has been placed on the market, clinical trials designed to explore new indications, new methods of administration or new combinations, etc. are normally considered as trials for new pharmaceutical products.