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Phase 3 trial

A Phase III trial is a randomized controlled multicentre trial on a large group of patients[1]. It is designed to assess the effectiveness of the new intervention and, thereby, its value in clinical practice[1].

Phase III trials involve large patient groups, from 300 to 3,000 or more depending on the disease or medical condition studied[1]. They are aimed at being the definitive assessment of how effective the drug is, in comparison with the current 'gold standard' treatment[1].

Because of their size and comparatively long duration, Phase III trials are the most expensive, time-consuming and difficult trials to design and run, especially in therapies for chronic medical conditions[1]. An analysis of Phase III pivotal trials leading to 59 US Food and Drug Administration drug approvals over 2015-16 showed a median cost of $19 million, but some trials involving thousands of subjects may cost 100 times more[2].

The design of a trial may be altered along the way, usually during Phase II or III, to accommodate interim results, adjust the statistical analysis, or end an unsuccessful design early, a process called an 'adaptive design'[3]. Once a drug has proved satisfactory after Phase III trials, the results are usually combined into a large document that forms the regulatory submission[4]. Certain Phase III trials continue while the regulatory submission is pending with the regulatory agency[5].

Why it matters to investors

A 2010 review found that about 50% of drug candidates either fail during the Phase III trial or are rejected by the national regulatory agency[6]. The results of successful Phase III trials are usually combined into the regulatory submission that is provided to regulatory authorities for review[4].

On this site

Related: Phase 2 trial, Phase 4 (post-marketing), Randomized controlled trial, New Drug Application (NDA)

Sources

  1. DeMets D, Friedman L, Furberg C (2010). Fundamentals of Clinical Trials (4th ed.). Springer. ISBN 978-1-4419-1585-6 . (via Wikipedia: Phases of clinical research)
  2. Moore TJ, Zhang H, Anderson G, Alexander GC (November 2018). "Estimated costs of pivotal trials for novel therapeutic agents approved by the US Food and Drug Administration, 2015–2016" . JAMA Internal Medicine . 178 (11): 1451– 1457. doi : 10.1001/jamainternmed.2018.3931 . PMC 6248200 . PMID 30264133 . ncbi.nlm.nih.gov (via Wikipedia: Phases of clinical research)
  3. Van Norman GA (June 2019). "Phase II trials in drug development and adaptive trial design" . JACC. Basic to Translational Science . 4 (3): 428– 437. doi : 10.1016/j.jacbts.2019.02.005 . PMC 6609997 . PMID 31312766 . ncbi.nlm.nih.gov; "Adaptive Designs for Clinical Trials of Drugs and Biologics: Guidance for Industry" (PDF) . U.S. Food and Drug Administration. 1 November 2019 . Retrieved 3 April 2020 . [ dead link ] fda.gov; Pallmann P, Bedding AW, Choodari-Oskooei B, Dimairo M, Flight L, Hampson LV, et al. (February 2018). "Adaptive designs in clinical trials: why use them, and how to run and report them" . BMC Medicine . 16 (1) 29. doi : 10.1186/s12916-018-1017-7 . PMC 5830330 . PMID 29490655 . {{ cite journal }} : CS1 maint: overridden setting ( link ) ncbi.nlm.nih.gov (via Wikipedia: Phases of clinical research)
  4. The regulatory authority in the US is the Food and Drug Administration ; in Canada, Health Canada ; in the European Union, the European Medicines Agency ; and in Japan, the Ministry of Health, Labour and Welfare (via Wikipedia: Phases of clinical research)
  5. "Guidance for Institutional Review Boards and Clinical Investigators" . Food and Drug Administration . 16 March 1999. Archived from the original on 6 May 2001 . Retrieved 27 March 2007 . web.archive.org (via Wikipedia: Phases of clinical research)
  6. Arrowsmith J (February 2011). "Trial watch: phase III and submission failures: 2007–2010" . Nature Reviews. Drug Discovery . 10 (2): 87. doi : 10.1038/nrd3375 . PMID 21283095 . S2CID 39480483 . doi.org (via Wikipedia: Phases of clinical research)

Checked 8 October 2026. How we check sources