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Phase 1 trial

A Phase I trial is the first stage of testing in human subjects[1]. These trials are designed to test the safety, side effects, best dose and formulation method for the drug[2].

Normally, a small group of 20–100 healthy volunteers is recruited[3]. Phase I trials most often include healthy volunteers, but clinical patients are sometimes used, such as patients with terminal cancer or HIV when the treatment is likely to make healthy individuals ill[4]. Phase I trials are not randomized, and so are vulnerable to selection bias[5].

In the United States, the sponsor must submit an Investigational New Drug application to the FDA before beginning a Phase I trial, detailing the preliminary data gathered from cellular models and animal studies[6]. Phase I trials normally include dose-ranging, also called dose escalation, so that the best and safest dose can be found and the point at which a compound is too poisonous to administer can be discovered[7].

In single ascending dose studies, small groups of subjects are given a single dose of the drug and are observed and tested for a period of time to confirm safety[8]. Dose escalation continues until pre-calculated pharmacokinetic safety levels are reached or intolerable side effects start showing up, at which point the drug is said to have reached the maximum tolerated dose[4]. Multiple ascending dose studies investigate the pharmacokinetics and pharmacodynamics of multiple doses of the drug, looking at safety and tolerability[8].

Why it matters to investors

Phase I trials are designed to test the safety, side effects and best dose of a drug[2]. Once a dose or range of doses is determined, the next goal is to evaluate whether the drug has any biological activity or effect[4].

On this site

Related: Investigational New Drug (IND), Phase 2 trial, Phase 3 trial, Randomized controlled trial

Sources

  1. "Types and phases of clinical trials" . American Cancer Society. 18 August 2020 . Retrieved 15 September 2020 . cancer.org (via Wikipedia: Phases of clinical research)
  2. "NCI Dictionary" . National Cancer Institute. 2 February 2011. cancer.gov (via Wikipedia: Phases of clinical research)
  3. "Types and phases of clinical trials" . American Cancer Society. 18 August 2020 . Retrieved 15 September 2020 . cancer.org; "Step 3. Clinical research" . US Food and Drug Administration. 14 October 2016. Archived from the original on 22 November 2014 . Retrieved 1 February 2017 . web.archive.org (via Wikipedia: Phases of clinical research)
  4. 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)
  5. Van den Eynde BJ, van Baren N, Baurain JF (2020). "Is There a Clinical Future for IDO1 Inhibitors After the Failure of Epacadostat in Melanoma?" . Annual Review of Cancer Biology . 4 : 241– 256. doi : 10.1146/annurev-cancerbio-030419-033635 . hdl : 2078.1/232835 . doi.org (via Wikipedia: Phases of clinical research)
  6. "The drug development process" . US Food and Drug Administration. 4 January 2018. Archived from the original on 26 August 2019 . Retrieved 17 August 2020 . web.archive.org (via Wikipedia: Phases of clinical research)
  7. Shamoo AE (2008). "The myth of equipoise in phase 1 clinical trials" . Medscape Journal of Medicine . 10 (11): 254. PMC 2605120 . PMID 19099004 . ( registration required ) medscape.com (via Wikipedia: Phases of clinical research)
  8. "Types and phases of clinical trials" . American Cancer Society. 18 August 2020 . Retrieved 15 September 2020 . cancer.org; Norfleet E, Gad SC (2009). "Phase I Clinical Trials". In Gad SC (ed.). Clinical Trials Handbook . John Wiley & Sons. p. 247. ISBN 978-0-470-46635-3 . (via Wikipedia: Phases of clinical research)

Checked 8 October 2026. How we check sources