Preclinical vs pilot vs RCT vs approved — and FDA vs compounded vs research-use-only
The evidence ladder
Not all "studies" are equal. Grade any claim by where it sits on this ladder:
Tier
What it means
Preclinical
Cells / animals only. Hypothesis-generating, not proof in people.
Pilot / early human
Small, often uncontrolled human studies. Signal, not proof.
RCT (Phase 2/3)
Randomized, controlled, powered trials. This is real evidence.
Approved
Regulator reviewed the full trial package.
This is exactly why every profile in our compound library shows an evidence tier — so BPC-157 ("0 Phase III") reads very differently from semaglutide ("large Phase 3 RCTs").
Three legal categories people confuse
FDA-approved drug — reviewed and approved; prescription-only (e.g., semaglutide, tesamorelin, PT-141).
Compounded drug (503A/503B) — made by a pharmacy for specific needs; NOT the same as FDA approval. The FDA is moving to exclude compounded semaglutide/tirzepatide as supply stabilizes.1
Research Use Only (RUO) — a research chemical, not a medicine, not for human use. Most "peptides" sold online are here.
WADA — for anyone tested
Many performance-adjacent peptides (GH secretagogues, BPC-157, TB-500, IGF-1) are prohibited by WADA — often at all times. If you're a tested athlete, "research use only" doesn't make it allowed.
How to use the News feed
Put it together: our This Week in Peptides feed tags every new paper and trial by tier and links the primary source. Read the tier first, the headline second — that habit alone puts you ahead of most of the internet.
Further reading — primary sources
FDA — proposal to exclude semaglutide/tirzepatide/liraglutide from the 503B bulks list. fda.gov
FDA — policies for compounders as GLP-1 supply stabilizes. fda.gov
This free curriculum is made possible by our sponsor, PureLux Bio — U.S.-made research-grade peptides.
For educational and research purposes only. This content is not medical advice. Compounds referenced are research use only unless noted as approved drugs, and nothing here is an instruction to use, prepare, or administer anything. Free Peptide University does not sell compounds.