The atlas groups its entries into five non-equivalent types. Understanding which type a peptide belongs to is essential for interpreting its evidence, status, and what online listings can and cannot tell you.
The full inclusion policy is documented in Scope and selection. For the basics of reading evidence grades alongside entry types, see How to read peptide evidence.
The five entry types
The scope policy defines the catalog as 100 high-recognition entries across four non-equivalent classes. The entry_type field in each monograph records the most appropriate category:
approved_drug — A product with current marketing authorization from at least one major regulator (FDA, EMA, or equivalent). The semaglutide monograph is an example: entry_type approved_drug, with FDA approvals across four indications and EMA authorizations. Even so, the grade and status are indication-specific — semaglutide is approved for glycemic control, weight management, and cardiovascular risk reduction, not for every claim made about GLP-1 receptor agonists.
investigational — A clinical-stage candidate with no marketing authorization identified in major regulator databases. The retatrutide monograph is entry_type investigational — Phase 3 data support multiple grade B claims, but no regulator has approved the molecule. The distinction matters: strong trial data and regulatory approval are different facts.
endogenous — A peptide native to the human body, included for its biological or scientific visibility regardless of whether a pharmaceutical product exists. GHK-Cu, LL-37, and humanin are examples. Their presence in the catalog reflects scientific relevance, not endorsement of any supplement or research product.
research_market — A product frequently sold in the commercial "research peptide" ecosystem without identified regulatory approval for human use. The BPC-157 monograph is entry_type research_market. Its regulatory table records no FDA-approved or EMA-authorized product. WADA lists BPC-157 as prohibited under class S0 (non-approved substances). Broad online visibility does not change its regulatory status or evidence grade.
boundary_case — An entry whose identity, composition, or regulatory status does not fit neatly into the other categories. Examples include PEG-MGF (pegylated protein with no defined small-molecule structure), thymalin (undefined peptide mixture from tissue extract), and cerebrolysin (porcine brain-derived peptide mixture).
What "research use only" does and does not mean
Many research-market products carry the label "for research use only." This is a marketing designation, not a regulator's determination that the product is safe, effective, authentic, pure, or sterile. As the scope policy states: a listing can establish that a name is being marketed; it cannot establish that the material matches a clinical-trial product or that any human-use claim has passed regulatory review.
The scope policy also documents that some marketed names refer to fragments, salts, metal complexes, mixtures, pegylated proteins, or poorly standardized products. The catalog classifies these boundary cases explicitly instead of assuming that every item sold as a peptide is a single well-defined peptide.
The catalog does not distinguish between entry types as a ranking. Inclusion reflects scientific, clinical, regulatory, or public visibility — not an endorsement. Approved drugs are not inherently more interesting than investigational candidates; research-market entries are not inherently more dangerous than endogenous peptides. The type tells you what kind of regulatory scrutiny the product has faced.
Evidence-search target differences
The scope policy defines different evidence-search priorities depending on entry type. For approved drugs, priority goes to current official product information, regulatory actions, and pivotal controlled human studies. For investigational candidates, the search emphasises ClinicalTrials.gov registries and published Phase 2 and 3 reports. For research-market entries, the search must also capture decisive negative, terminated, retracted, or safety studies, since these are more likely to be absent from commercial宣传. Preclinical work is included only when human evidence is absent or the mechanism requires it, and it is clearly labeled as non-human.
The refresh policy for time-sensitive claims
Every entry type shares one rule: approval, trial, WADA, and legal-status claims are time-sensitive and carry an as_of or last_verified date. The scope policy requires that these dates be rechecked before publication or decision-making. An investigational peptide with promising Phase 3 data today may receive approval next year; a research-market peptide flagged by a regulator tomorrow changes status. The date tells you when the review was performed, not when the next change will occur.
Reading entry type together with evidence
Entry type and evidence grade answer different questions. Retatrutide (investigational) carries grade B claims — strong Phase 3 data without regulatory approval. BPC-157 (research_market) carries grade D and C claims — limited human data, no approval, and extensive preclinical work. Semaglutide (approved_drug) carries multiple grade A claims and one grade B claim for an accelerated approval that still requires confirmatory evidence.
Before drawing a conclusion from any peptide's status, check both its entry type and its evidence grade, and verify that the claim you are interested in matches the specific indication, product, and jurisdiction described in the monograph. The methodology pages document the rules the atlas uses to keep these dimensions separate.