In phase 1, a small number of volunteers receive the substance to assess its safety, tolerability and pharmacokinetics. In phase 2, hundreds of participants with the condition of interest make it possible to explore whether there is efficacy and which range of amounts is appropriate. In phase 3, large, randomised studies, usually controlled with placebo or another treatment, confirm efficacy and broaden the safety data.
Only after phase 3 is approval requested from health authorities. Afterwards, phase 4, or pharmacovigilance, follows the real-world use of the medicine in the population.
Knowing which phase a compound is in helps place it: semaglutide and tirzepatide completed phase 3 programmes and are approved; other metabolic agonists such as retatrutide or survodutide are still in clinical development.
A molecule in phase 2 has promising signals, not an established safety profile. The development phase is the best quick measure of how much is really known about a compound in humans.
Related terms
Learn it in depth at the Peptide University
- Hierarchy of evidence and development phases · Module 13
- Evidence and comparison · Module 3
- Longevity and mitochondrial function · Module 6
- Neuroimmunomodulation: VIP, α-MSH, KPV and ARA-290 · Module 12
- Common biases and scaling between species · Module 13
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Definition for educational and scientific purposes. It is not medical advice or a recommendation for use. NeoPeptidos products are sold labelled for research use only (RUO).