TB-500 (N-acetylated LKKTETQ fragment)
FDA's compounding assessment identifies no FDA-approved drug product containing TB-500 and no identified human exposure data for drug products containing the fragment.
Current sourceTB-500
What is known about the synthetic fragment—and what full-length thymosin beta-4 research cannot prove
TB-500 is commonly described as an N-acetylated version of the LKKTETQ fragment from thymosin beta-4. It is not interchangeable with full-length recombinant thymosin beta-4 studied in humans. FDA reports that it has identified no human exposure data for drug products containing the TB-500 fragment and highlights unresolved immunogenicity, impurity, and safety questions.
Editorial status
This page aggregates regulatory documents and published human research. Its claims, citations, populations, and limitations received an independent editorial evidence check. Last editorial audit: .
It has not been medically reviewed by a clinician. It provides general education, not diagnosis, treatment, dosing instructions, or advice for an individual. Use the product-specific official information and consult a qualified clinician or pharmacist for personal decisions.
Product and regulatory distinctions
A compound name is not one interchangeable set of instructions. Product, formulation, indication, labeling, and jurisdiction matter.
TB-500 as a compounding bulk substance
FDA lists the substance among nominated bulk substances that may present significant safety risks and cites potential immunogenicity, aggregation, and peptide-related impurities.
Current sourceTB-500 in sport
TB-500 is named on the 2026 World Anti-Doping Agency Prohibited List.
Current sourceClaim-by-claim evidence map
Each finding is tied to the population and product actually studied. Trial results are not personal predictions.
TB-500 is a short synthetic peptide related to, but distinct from, full-length thymosin beta-4.
- Population
- Chemical and equine anti-doping analysis of N-acetylated LKKTETQ.
- Finding
- Investigators identified TB-500 as an N-acetylated synthetic version of amino acids 17–23 of thymosin beta-4 and characterized it and its metabolites in horses.
- Limits
- Chemical identity and detection in horses do not establish safety or therapeutic effectiveness in humans.
Laboratory findings involving the LKKTETQ region do not establish injury recovery in people.
- Population
- Cultured human hepatic stellate cells exposed to a non-acetylated thymosin beta-4 fragment.
- Finding
- The 17–23 amino-acid fragment altered selected signaling, proliferation, and migration measures in this cell model.
- Limits
- This was an in-vitro fibrosis model using a related fragment, not a clinical study of marketed TB-500, sports injury, wound healing, or human outcomes.
TB-500 metabolism and wound-healing assays remain preclinical.
- Population
- Human serum in vitro, enzyme systems, rats, and fibroblast assays.
- Finding
- A 2024 study characterized TB-500 metabolites and reported that a metabolite, rather than the parent peptide, may account for activity in its in-vitro assay.
- Limits
- Rat metabolism and cell migration assays cannot establish a clinical effect, safe formulation, or appropriate human use.
Products sold under TB-500-related names may not match their descriptions.
- Population
- Laboratory analysis of non-approved products obtained for veterinary anti-doping research.
- Finding
- Researchers reported that tested TB500/TB1000 product contents were not systematically consistent with their descriptions.
- Limits
- This product sample does not estimate the prevalence of mislabeling across all sellers, but it demonstrates why a label alone is not proof of identity.
What this evidence does not answer
- FDA reports no identified human exposure data for drug products containing the TB-500 fragment.
- Human studies of full-length recombinant thymosin beta-4 must not be presented as trials of TB-500.
- There is no adequate clinical evidence establishing that TB-500 accelerates muscle, tendon, ligament, or wound recovery in people.
- Human pharmacokinetics, long-term safety, immunogenicity, interactions, reproductive effects, and reliable product specifications are not established.
Useful information to organize between visits
- Exact label name and whether it states TB-500, LKKTETQ, thymosin beta-4, or another sequence
- Seller or dispensing pharmacy, lot number, labeled ingredients, storage instructions, and packaging photographs
- Route and timing of any exposure, without using this page to select a regimen
- Symptoms with onset, severity, duration, and any medical evaluation
- Concurrent rehabilitation, medicines, supplements, and procedures that could affect the same outcome
Questions to bring to a clinician or pharmacist
- 1.Is this product the TB-500 fragment, full-length thymosin beta-4, or something that cannot be verified?
- 2.What evidence-based options exist for the injury or condition being targeted?
- 3.What symptoms after exposure require urgent assessment or reporting to a regulator?
- 4.Do my sport rules prohibit this substance even outside competition?
Primary sources
- Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety RisksU.S. Food and Drug Administration · Published Updated 2026 · Accessed July 12, 2026
- FDA Briefing Document: TB-500 for Pharmacy Compounding Advisory CommitteeU.S. Food and Drug Administration · Published 2026 · Accessed July 12, 2026
- Doping control analysis of TB-500 in equine urine and plasmaJournal of Chromatography A via PubMed · Published 2012 · Accessed July 12, 2026
- Thymosin beta-4 inhibits activation, proliferation, and migration of human hepatic stellate cells via its actin-binding domainPubMed · Published 2018 · Accessed July 12, 2026
- Simultaneous quantification of TB-500 and its metabolites and screening by wound-healing activities in vitroPubMed · Published 2024 · Accessed July 12, 2026
- TB500/TB1000 and SGF1000: A scientific approach to misbranded and adulterated drugsDrug Testing and Analysis via PubMed · Published 2023 · Accessed July 12, 2026
- 2026 Prohibited ListWorld Anti-Doping Agency · Published 2026 · Accessed July 12, 2026
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