Phase II Trial
Definition
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.
What this means for research sourcing
Understanding evidence quality helps researchers prioritize compounds. Volta's research library summarizes the literature behind stocked compounds.
Related Terms in Evidence & Research
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.
Blinding
Withholding treatment allocation from participants, investigators or outcome assessors. It fails in practice whenever a compound has obvious effects, which is a known weakness of trials in this area.
Double-Blind
Neither participants nor investigators know who is in which arm, so expectation cannot colour reported symptoms or outcome assessment. It is a design feature, not a guarantee, and papers increasingly report whether blinding held.
Open-Label
Everybody knows who is receiving what. Open-label extensions following a blinded trial give useful long-term safety data, and their efficacy figures are not placebo-controlled and should not be read as though they were.
