What is a Phase 3 Clinical Trial?

Phase 3 clinical trials follow phase 1 and 2 clinical trials. In a phase 1 clinical trial, the tolerability and safety of the new drug is studied, usually in a small number of healthy volunteers. Phase 2 is aimed at determining the drug's efficacy and optimal dosing regimen. After phase 2, the drug is entered into the next phase of testing in a phase 3 trial.

The main focus of phase 3 trials is to demonstrate and confirm the prelimary evidence gathered in the previous trials that the drug is, a safe, beneficial and effective treatment for the intended indication.

Phase 3 is the last phase of testing to be completed before the drug's details and clinical trial results are submitted to the regulatory authorities for approval of the drug's release on the open market. Phase 3 is therefore a vital phase of drug development and billions may be spent progressing the drug to a phase 3 trial, only for the drug to prove ineffective in a larger patient population or have serious safety concerns that prevent its approval.

Phase 3 trials are often multicentre trials involving up to 3,000 participants. Aside from testing safety and efficacy variables again, other aspects of the drug that may be studied in phase 3 are further exploration of the dose-response relationship, the drug's effects in wider populations and its efficacy at different stages of disease or when used in combination with other agents.

The drug may also be tested in subgroups with co-morbidities such as kidney or liver disease or heart disorders. Much of the information that is given on the label of a drug is derived from the phase 3 trial results.

Other factors that may be considered inphase 3 include improvement in patients' quality of life and secondary benefits of the drug.

Further Reading

Last Updated: Jan 2, 2023

Dr. Ananya Mandal

Written by

Dr. Ananya Mandal

Dr. Ananya Mandal is a doctor by profession, lecturer by vocation and a medical writer by passion. She specialized in Clinical Pharmacology after her bachelor's (MBBS). For her, health communication is not just writing complicated reviews for professionals but making medical knowledge understandable and available to the general public as well.


Please use one of the following formats to cite this article in your essay, paper or report:

  • APA

    Mandal, Ananya. (2023, January 02). What is a Phase 3 Clinical Trial?. News-Medical. Retrieved on June 08, 2023 from https://www.news-medical.net/health/What-is-a-Phase-3-Clinical-Trial.aspx.

  • MLA

    Mandal, Ananya. "What is a Phase 3 Clinical Trial?". News-Medical. 08 June 2023. <https://www.news-medical.net/health/What-is-a-Phase-3-Clinical-Trial.aspx>.

  • Chicago

    Mandal, Ananya. "What is a Phase 3 Clinical Trial?". News-Medical. https://www.news-medical.net/health/What-is-a-Phase-3-Clinical-Trial.aspx. (accessed June 08, 2023).

  • Harvard

    Mandal, Ananya. 2023. What is a Phase 3 Clinical Trial?. News-Medical, viewed 08 June 2023, https://www.news-medical.net/health/What-is-a-Phase-3-Clinical-Trial.aspx.


The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of News Medical.
Post a new comment
You might also like...
NVX-CoV2373 COVID vaccine safe and effective in preventing COVID-19 in adolescent