[Code of Federal Regulations]
[Title 21, Volume 5]
[Revised as of April 1, 2001]
From the U.S. Government Printing Office via GPO Access
[CITE: 21CFR312.21]

[Page 61-62]
 
                        TITLE 21--FOOD AND DRUGS
 
CHAPTER I--FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN 
                           SERVICES--Continued
 
PART 312--INVESTIGATIONAL NEW DRUG APPLICATION--Table of Contents
 
          Subpart B--Investigational New Drug Application (IND)
 
Sec. 312.21  Phases of an investigation.

    An IND may be submitted for one or more phases of an investigation. 
The clinical investigation of a previously untested drug is generally 
divided into three phases. Although in general the phases are conducted 
sequentially,

[[Page 62]]

they may overlap. These three phases of an investigation are a follows:
    (a) Phase 1. (1) Phase 1 includes the initial introduction of an 
investigational new drug into humans. Phase 1 studies are typically 
closely monitored and may be conducted in patients or normal volunteer 
subjects. These studies are designed to determine the metabolism and 
pharmacologic actions of the drug in humans, the side effects associated 
with increasing doses, and, if possible, to gain early evidence on 
effectiveness. During Phase 1, sufficient information about the drug's 
pharmacokinetics and pharmacological effects should be obtained to 
permit the design of well-controlled, scientifically valid, Phase 2 
studies. The total number of subjects and patients included in Phase 1 
studies varies with the drug, but is generally in the range of 20 to 80.
    (2) Phase 1 studies also include studies of drug metabolism, 
structure-activity relationships, and mechanism of action in humans, as 
well as studies in which investigational drugs are used as research 
tools to explore biological phenomena or disease processes.
    (b) Phase 2. Phase 2 includes the controlled clinical studies 
conducted to evaluate the effectiveness of the drug for a particular 
indication or indications in patients with the disease or condition 
under study and to determine the common short-term side effects and 
risks associated with the drug. Phase 2 studies are typically well 
controlled, closely monitored, and conducted in a relatively small 
number of patients, usually involving no more than several hundred 
subjects.
    (c) Phase 3. Phase 3 studies are expanded controlled and 
uncontrolled trials. They are performed after preliminary evidence 
suggesting effectiveness of the drug has been obtained, and are intended 
to gather the additional information about effectiveness and safety that 
is needed to evaluate the overall benefit-risk relationship of the drug 
and to provide an adequate basis for physician labeling. Phase 3 studies 
usually include from several hundred to several thousand subjects.