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Trial Phases

Following a positive outcome in preclinical testing, the sponsoring organization (usually a drug manufacturer) will seek approval to conduct clinical trials. Once approval has been granted, the sponsor will usually complete three phases of clinical testing in order for the applicable regulatory authority to approve the new treatment. An optional fourth phase typically follows approval.

For each phase of a clinical trial, the sponsor collaborates with physicians to conduct the clinical trial, prepares a plan (or protocol) that describes the clinical trial, and submits detailed paperwork to applicable regulatory authority and independent review body to obtain approval to conduct the trial.

Phase I—The process of testing an investigational drug on a smaller number of subjects to establish that it is safe for use in humans.

  • Scope: A series of small tests to determine how healthy people (those without the condition or illness the drug will treat) react to and are affected by the treatment
  • Subjects: Healthy volunteers who are not taking other medicines
  • Number of volunteers: Less than 100
  • Duration: Several months
  • Goal: To determine the optimal dose and establish that the drug is generally safe

Phase II—The process of testing an investigational drug on a small number of subjects to show it is generally safe and effective in treating or preventing a specific condition or illness.

  • Scope: A limited number of studies that help establish the drug’s safety and effectiveness and identify its side effects
  • Subjects: Patients who have the condition or illness to be treated
  • Number of volunteers: Several hundred
  • Duration: Several months to 2 years
  • Goal: To establish how doctors should use the drug to treat patients with the specified condition or illness

Phase III—The process of testing an investigational drug on a larger population of subjects to show that it is safe and effective in treating or preventing a specific condition or illness.

  • Scope: A large number of studies designed to establish a drug’s safety and effectiveness and to identify its side effects
  • Subjects: Patients who have the condition or illness to be treated, who may have other illnesses, and who may be taking medications in addition to the investigational drug
  • Number of volunteers: Several thousand
  • Duration: Several months to several years
  • Goal: To establish how doctors should use the drug to treat patients with the specified condition or illness

Phase IV—The process of testing an approved drug in order to determine additional information.

  • Scope: Multiple studies to determine how a drug compares with other drugs, to ascertain its safety in large number of patients and to identify its effects in patients with conditions that were excluded from phase III trials
  • Subjects: Patients who have the condition or illness to be treated, who may have other illnesses, and who may be taking medications in addition to the study drug
  • Number of volunteers: Several thousand
  • Duration: Several months to several years
  • Goal: To determine if the drug’s use can be broadened to include more patients and/or whether additional safety issues need to be addressed
Laboratory Assistant Jack Walker verifies the identity, volume and integrity of a sample in the SPE area at the Plasma Logistics Center in Knoxville, Tennessee.
 

Phase II and phase III both assess the safety and effectiveness of the investigational drug and often involve controlled studies in which the study drug is compared to a placebo (sugar pill) or to an existing drug. This comparison helps minimize bias in interpreting the study results. However, this does NOT mean that those in the placebo group never receive the investigational medication.

Phase III clinical trials are the most significant because they involve a large number of people who receive treatment for an extended period of time. The outcome of phase III trials provides the basis for FDA approval and establishes exactly how the drug is to be used.

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