EVIDENCE TIERS: HOW WE RATE EACH ENTRY
Not all evidence is equal. PepVault classifies every claim about every peptide by evidence tier so you can calibrate your confidence appropriately — and distinguish what is well-established from what is promising-but-early.
1.Tier 1: FDA-approved and Phase III clinical evidence
The highest evidence level. A compound has completed randomized, double-blind, placebo-controlled Phase III trials in humans and received FDA approval (or equivalent from EMA, TGA, or other major regulatory bodies) for at least one indication. This means safety and efficacy have been rigorously established for that specific use, at that specific dose, in the studied population.
Examples in the peptide adjacent space: semaglutide (Ozempic for diabetes, Wegovy for obesity), tirzepatide (Mounjaro for diabetes, Zepbound for obesity), and in Russia specifically, Semax and Epithalon have regulatory approval. FDA-approved compounds can be prescribed by physicians for approved indications, and safety monitoring is ongoing post-approval.
Tier 1 evidence does not mean a compound is risk-free or that the approved dose is optimal for all uses. It means the specific indication has been studied with sufficient rigor to establish a meaningful evidence-based risk-benefit assessment.
Most research peptides do not reach Tier 1 because the clinical trial pathway is prohibitively expensive for compounds that cannot be patented or that lack a corporate sponsor willing to fund hundreds of millions in trials. Evidence tier reflects regulatory status, not necessarily true biological effectiveness.
When we label a compound Tier 1, we link to the specific approval documentation and landmark trials. We also note if Tier 1 status is specific to one indication (e.g., semaglutide for diabetes, not for athletic performance) and what is extrapolated beyond the approved use.
2.Tier 2: Human clinical trials (Phase I/II)
Phase I and Phase II human trials establish safety (Phase I) and preliminary efficacy (Phase II) but are not sufficient for FDA approval on their own. These trials are often smaller (20-200 participants) and may not be fully randomized or placebo-controlled. They provide meaningful human data but with more uncertainty than Phase III.
Thymosin Alpha-1 has Phase II human data for hepatitis and immune support — it has gone through enough clinical evaluation to have a meaningful safety and efficacy picture in humans, even without FDA approval. Some GH peptide work (particularly in elderly and growth hormone deficient populations) exists at Phase I/II level.
Tier 2 evidence means we have human pharmacokinetic data, some human efficacy signals, and safety data from at least small-scale human exposure. The gap between Tier 2 and Tier 1 is largely the scale of evidence, not necessarily the quality of the underlying biology.
A key limitation of Tier 2 evidence: Phase I/II trials often study specific populations (sick patients, elderly, growth hormone deficient individuals) whose responses may not generalize to healthy adults seeking performance or wellness optimization. A Phase II trial showing BPC-157 heals ulcers in sick patients does not directly establish that it heals athletic soft tissue injuries in healthy adults, even if the mechanism suggests it should.
We cite specific Phase I/II studies when labeling a compound Tier 2, and note the study population and endpoint so you can assess how well the study generalizes to your use case.
3.Tier 3: Animal and pre-clinical evidence
The majority of research peptide evidence sits here. Rodent models (rats and mice, primarily) have been used extensively to study BPC-157, TB-500, Epithalon, the melanotan peptides, cognitive peptides, and many others. In vitro (cell culture) studies also fall into this tier.
Animal results are meaningful but not definitive. Species differences in receptor distribution, metabolism, pharmacokinetics, and physiology mean that rodent results do not reliably predict human outcomes. This is a well-known limitation of pre-clinical research — the majority of compounds that succeed in animal models do not make it through Phase II human trials.
What animal data does give us: mechanistic insight (how the compound works), dose-response relationships (though these require human body surface area scaling), tissue distribution patterns, and acute toxicity assessment. BPC-157's extensive, multi-decade rodent literature from multiple independent labs provides a meaningful mechanistic case for its effects, even in the absence of Phase III human trials.
The distinction within Tier 3 matters: one small rat study from 1995 is much weaker evidence than 20 independent studies from different labs over 20 years consistently showing the same effects. We try to convey this within Tier 3 citations by noting replication level and consistency of findings across research groups.
In vitro studies (cell culture) are included in Tier 3 but with the additional caveat that cell culture conditions are far from the complexity of whole-organism biology. A peptide that activates a receptor in isolated cells may or may not produce the same effect when competing with serum proteins, metabolized by enzymes, and distributed across multiple tissue types in a living organism.
4.Tier 4: Anecdotal and community evidence
Anecdotal evidence from user communities — forums, Reddit, social media, personal communications — is the weakest evidence tier but not zero information. Consistent patterns across thousands of independent user reports over years carry statistical weight that cannot be entirely dismissed, even without controls.
The limitations of anecdotal evidence are well-established: no blinding, no placebo control, strong publication and selection bias (people who have dramatic positive results are more likely to post than people who had no result), variable product quality from uncontrolled sources, confirmation bias in self-reported outcomes, and regression to the mean (injuries heal and symptoms improve naturally, and people attribute the improvement to whatever they were taking).
We include Tier 4 evidence where scientific data is absent or limited, labeled explicitly. 'Anecdotal reports consistently indicate X' conveys different confidence than 'Phase II trials demonstrate X.' The labeling is intentional and should inform your interpretation.
Community bloodwork data adds value to Tier 4 evidence when it exists. Users who test their IGF-1 before and after GH peptide protocols and post results publicly produce a form of community-aggregated data that approaches observational study quality, even without formal controls. We treat this as a stronger form of anecdotal evidence than purely subjective reports.
The most valuable anecdotal evidence is negative evidence — reports of compounds failing to produce expected effects, or producing unexpected side effects. Negative anecdotal reports are underrepresented on public forums (unsuccessful protocols are rarely shared), making them more informative when they do appear consistently.
Sources & Studies
Sackett DL. et al., BMJ, 1996
Petrisor B, Bhandari M., Indian J Orthop, 2007