Evidence Rankings

Our evidence grading system evaluates each peptide based on the totality of published scientific literature, from large-scale randomized controlled trials to early in vitro studies. The goal is to give researchers a transparent, at-a-glance assessment of how well-supported each compound's proposed mechanisms and effects are by credible, peer-reviewed data.

Grades range from A (FDA-approved with robust Phase III data) down to F (theoretical or insufficient data). This system reflects the current state of research as of our most recent literature review and is updated as new studies are published. A lower grade does not necessarily mean a peptide lacks therapeutic potential — it means the evidence base has not yet matured to the point of clinical confirmation.

We consider several dimensions when assigning grades: the number and quality of published studies, whether human clinical trials exist, sample sizes, study design (randomized controlled vs. open-label), reproducibility across independent laboratories, regulatory status, and the overall mechanistic plausibility. Our ratings are conservative — we require substantive published evidence, not just theoretical rationale, to assign higher grades.

For detailed information about each peptide's mechanism, dosing protocols, safety profiles, and individual study citations, visit the peptide's dedicated research page. You can also explore our learning center for educational content about peptide science, or use our research tools for dosing calculators, reconstitution guides, and more.

Our evidence grading methodology draws on established frameworks used in evidence-based medicine, including the Oxford Centre for Evidence-Based Medicine (OCEBM) levels of evidence and the GRADE (Grading of Recommendations, Assessment, Development, and Evaluations) approach. We adapted these frameworks specifically for the peptide research context, where the landscape ranges from FDA-approved therapeutics to novel research compounds with minimal published data.

Each peptide is evaluated across five core dimensions: (1) Clinical trial evidence — the number, phase, size, and design quality of human clinical trials; (2) Preclinical evidence — the depth and reproducibility of animal model studies across independent research groups; (3) Mechanistic understanding — how well the molecular mechanisms of action are characterized; (4) Safety data — the extent of published safety, toxicology, and adverse event reporting; and (5) Regulatory status — whether the compound has received regulatory approval or is under active review.

We weight clinical trial evidence most heavily, as human data provides the strongest signal for translational relevance. A compound with extensive animal data but no human trials will typically not exceed Grade D, regardless of how promising the preclinical results appear. This conservative approach reflects the well-documented challenge of translating animal study results to human outcomes — historically, roughly 90% of compounds that succeed in animal models fail in human clinical trials.

Our database is reviewed quarterly. When significant new studies are published — particularly Phase II or Phase III trial results — peptide grades are reassessed. All grade assignments are reviewed by our research team and referenced against the current PubMed, ClinicalTrials.gov, and FDA databases. For the most detailed and up-to-date evidence analysis, visit each peptide's individual research page, which includes direct links to source publications.

The peptide therapeutics field is experiencing rapid growth, with the global peptide therapeutics market projected to exceed $80 billion by 2030. Yet the evidence landscape remains highly uneven. A handful of peptides — primarily GLP-1 receptor agonists like semaglutide and tirzepatide — have amassed enormous clinical datasets through multi-billion-dollar development programs. Meanwhile, many promising research peptides remain in early-stage investigation, often limited by funding constraints or the inherent challenges of peptide drug development (stability, bioavailability, delivery route optimization).

It is important to understand that evidence grades are not static. The peptide research landscape is evolving rapidly, with new clinical trials launching regularly. Compounds currently rated Grade D or E based on preclinical data may advance to clinical trials within the next few years. Conversely, peptides in early clinical trials (Grade C) may see their evidence base strengthen or weaken as trial results are published.

Researchers should also be aware of publication bias — positive results are more likely to be published than negative findings, which can inflate the apparent evidence base for certain compounds. Our grading attempts to account for this by weighing registered clinical trials (even those without published results), known safety signals, and the overall balance of published literature. For compounds with red flags — such as cancelled trials, unreported results, or significant safety signals — these factors are noted on each peptide's individual research page.

For a deeper understanding of peptide science fundamentals, visit our glossary or explore the peptide basics guide. For information about safe handling and storage, see our safety resources.