Clinical Trial
Definition
A study testing an intervention in human volunteers under a protocol fixed before enrolment. The protocol, not the published paper, is what defines the question the trial was built to answer.
Where this term comes up
Entries whose definition mentions Clinical Trial.
What this means for research sourcing
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Related Terms in Evidence & Research
Randomized Controlled Trial (RCT)
A study in which participants are allocated to arms by chance, so that known and unknown differences between groups even out. It is the strongest single-study design for showing that an intervention caused an outcome.
Phase I Trial
First administration in humans, typically 20 to 100 volunteers, looking at safety, tolerability and pharmacokinetics rather than at whether the compound works. Most research peptides have never reached this stage.
Phase II Trial
Up to several hundred participants with the condition in question, testing whether there is an effect worth confirming and finding the amount to carry forward. It is where most candidates fail.
Phase III Trial
The pivotal study, commonly 300 to 3,000 participants or more, powered on a pre-specified endpoint and comparing against placebo or standard care. Approval decisions rest on it.
Phase IV Trial
Study after approval, in ordinary clinical use rather than in a selected trial population. Long-term and rare harms surface here, which is why an approval is not the end of the evidence.
Preclinical
Work done before any human administration: cell culture, tissue and animal models. Most peptides discussed in this field have preclinical evidence only, and rodent findings fail to carry across to humans far more often than they succeed.
In Vitro
In glassware: cells, tissue or isolated enzymes outside a living organism. Concentrations used in vitro are frequently unreachable in a body, which caps what such a result can predict.
In Vivo
In a living organism, animal or human. In-vivo work accounts for absorption, distribution, metabolism and clearance in a way cell work cannot, which is why an in-vitro effect so often disappears in vivo.