Gathering the record
Relay is organizing the evidence and source boundaries.
N-acetylated thymosin beta-4 heptapeptide fragment
An experimental peptide often discussed for injury recovery. It is a small fragment of thymosin beta-4, not the full molecule.
Evidence is explained by question. Dosing references show their own check dates.
60-second overview
Why people look into it, what studies found, and what is still unknown.
Educational information only. Evidence reviewed through July 25, 2026. Published studies, sponsor announcements, and trials without results are labeled separately. Evidence gaps apply to the specific finding beside them.
Research questions
Each label shows how much evidence supports that question.
What studies show
None located. FDA found no clinical study or human exposure data for TB-500 free base or acetate by any route.
FDA identifies TB-500 free base as Ac-LKKTETQ, corresponding to residues 17-23 of the 43-amino-acid thymosin beta-4 molecule.
FDA searched the medical literature and trial registry and found no TB-500 administration in humans by any route.
FDA explicitly distinguishes the 43-amino-acid molecule from the seven-amino-acid TB-500 fragment.
The 2024 laboratory study found activity for one shorter metabolite, not for parent TB-500 at the tested concentration.
FDA found mismatched names, salts, formulas, identifiers, and certificates.
The July 23 committee recommendation favored inclusion despite FDA's negative review. FDA makes the final decision, and compounded drugs are not FDA approved.
Risks & unknowns
No human TB-500 exposure, pharmacokinetic, safety, or efficacy study was located.
No direct evidenceNo reported case does not mean proven safety. Human benefits, adverse effects, and repeated-exposure risks remain unknown.
Open sourceThe available information does not reliably show how often particular side effects occur.
Evidence boundaryUnder-detected or under-reported events must not be described as rare.
Relay has not verified which side effects led people to stop treatment in studies.
Evidence boundaryThis is an evidence gap, not proof that discontinuations did not occur.
Relay has not verified a compound-specific warning summary for this profile.
Evidence boundaryNot FDA approved. On July 23, 2026, PCAC voted 8-6 with one abstention to recommend adding TB-500 free base and acetate to the 503A Bulks List despite FDA's negative recommendation. The vote is nonbinding and final FDA action was not located by July 25. WADA prohibits thymosin beta-4 and derivatives including TB-500. Whether TB-500 has any clinically meaningful human effect, how it behaves in people, repeated-exposure safety, and whether a labeled material is actually the stated free base or acetate.
This profile does not contain verified, product-specific emergency instructions.
Evidence boundaryRelay does not infer emergency guidance from study discontinuations, mechanism, or incomplete adverse-event reporting.
Dosing references
Each table labels its source and applies only to the named route, product, or study. An online example or community report is not an approved dose.
TB-500 can refer to a thymosin-beta-4 fragment or be used loosely for full-length material. Full-length thymosin-beta-4 trials cannot establish a fragment's dose.
What would fill this gap: Sequence-confirmed identity and a human protocol for that exact material.
Dosing review checked Oct 20, 2026. Additional sources are available below.No route-specific preparation instructions were verified. A different route or product does not supply them.
Concentration = total mass ÷ final volume. The calculator performs user-entered math; it does not choose a dose or diluent.
Open concentration calculatorStarting dose: the amount used at the beginning of the named label schedule or trial.
Maintenance: the ongoing amount described by that product label.
Trial target: the amount assigned to a study group. Different groups may stop increasing at different targets.
Published research investigated TB-500 in human-derived laboratory systems, cultured fibroblasts, and rats to characterize breakdown products and experimental wound-closure signals.
Population: Human serum and microsomal systems, cultured fibroblasts, and rats
Design: TB-500 metabolism in human-derived in-vitro systems and rats, with fibroblast scratch-wound assays
Mechanisms
TB-500 free base is N-acetyl-LKKTETQ, corresponding to thymosin beta-4 residues 17-23. The acetate salt is a distinct bulk drug substance. Located evidence covers analytical identity, animal and in-vitro metabolism, and a fibroblast scratch-wound assay. FDA found no human exposure, PK/PD, safety, or efficacy studies by any route.
A plausible mechanism can explain why a study was attempted. It does not prove that the compound improves a human outcome.
Research reference
A reference for the studies, populations, and routes behind this profile.
The traceable evidence consists of analytical, cell, rat, and equine work on the seven-amino-acid fragment.
Research depth describes how large and mature the overall record is. It does not tell you whether the results were positive.
No human exposure, pharmacokinetic, safety, or efficacy study of verified TB-500 was located.
Confidence describes how reliable and consistent the conclusions are. It can be high for one outcome and low for another.
The strongest evidence type shows what the best-supported conclusions are actually based on.
Human findings are more directly relevant than animal or laboratory results, but they still apply only to the populations and outcomes studied.
Route-specific record
These are exposures used in cited research for a specific route and population—not an instruction for an individual.
Half-life describes how long it takes the measured amount in the body to fall by half. It is not a dosing recommendation.
Evidence can change by administration method. Findings from one route should not automatically be applied to another.
Evidence boundary: No verified human administration, pharmacokinetic, efficacy, or safety study was located. A laboratory metabolite signal does not establish benefit from the parent fragment, and full-length thymosin beta-4 is a different identity. Amounts shown describe cited research exposure—not a dosage recommendation.
Studies
Study arms are reported for transparency. They describe what researchers did in a defined record and do not transfer across identities, routes, formulations, or populations.
A later trial phase can ask a more mature question, but it does not guarantee a positive result, regulatory approval, or relevance outside the studied population.
TB-500 metabolism in human-derived in-vitro systems and rats, with fibroblast scratch-wound assays
Human serum and microsomal systems, cultured fibroblasts, and rats
TB-500 was broken down into shorter acetylated peptides. Parent TB-500 did not improve fibroblast scratch-wound closure at the tested concentration; one shorter metabolite, Ac-LKKTE, showed activity.
Study administration: TB-500 free base and synthesized metabolites under laboratory protocols
Limitations: Laboratory and rat findings do not demonstrate healing, effectiveness, pharmacokinetics, or safety in people. A metabolite result cannot be assigned to the parent peptide without human evidence.
Liquid chromatography-mass spectrometry identification after research administration in horses
Horses
The parent peptide and multiple C-terminally shortened metabolites were detected in equine plasma and urine.
Study administration: Protocol-defined subcutaneous TB-500 free base administration
Limitations: Animal detection and metabolism study, not a wound-healing or efficacy study. It cannot establish a human dose, route, benefit, or safety profile.
Community
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2026-07-23
2026-07-21
2026-01-01
2024-03-15 · PMID 38382158 · DOI 10.1016/j.jchromb.2024.124033
2012-11-23 · PMID 23084823 · DOI 10.1016/j.chroma.2012.09.043
2012-09-07 · PMID 22962027 · DOI 10.1002/dta.1402