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Synthetic thymosin beta-4 fragment (7 amino acids)

TB-500

TB-500 is a lab-made seven-amino-acid fragment of the protein thymosin beta-4, sold for injury recovery although no study of it in people has been published.

Medical review in progressLast reviewed

US regulatory status

Not approved for human use in the US

TB-500 is not approved by the FDA for any use and is not the same substance as thymosin beta-4. As of April 2026 its nomination had been withdrawn from the FDA’s Category 2 safety-risk list. In July 2026 an FDA advisory committee narrowly voted, against FDA staff advice, to recommend adding it to the 503A bulks list; the vote is not binding, and as of October 16, 2026 no rule had been published. WADA bans thymosin beta-4 and its derivatives, naming TB-500, at all times (S2.3).

As of

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On this page
  1. US regulatory status
  2. At a glance
  3. What the research shows
  4. Side effects and safety
  5. Vial math
  6. Questions people ask
  7. Sources
  8. Related compounds

At a glance

Also known as
Thymosin beta-4 fragment, Ac-LKKTETQ, Thymosin β4 (17-23), TB-500 acetate
Supplied as
Freeze-dried powder, mixed before use
Research
Animal or lab studies only
US status
US status: Not approvedchecked

What the research shows

Evidence grade

Animal or lab studies only

Studied in cells or animals, not properly in people. Animal results may not apply to humans.

TB-500 is residues 17 to 23 (LKKTETQ) of thymosin beta-4, a natural 43-amino-acid protein, with an acetyl group added. It was first made in 2003, and a veterinary preparation appeared in 2011, marketed to boost performance in horse and greyhound sports. The FDA’s 2026 review found no published study in which TB-500 was given to people, and no animal study testing whether it heals wounds. The one lab study it found reported that TB-500 did not heal scratch wounds in cultured fibroblasts (connective tissue cells), although one of its breakdown products appeared to. A 2015 review reports that thymosin beta-4, the full protein, has been used in several clinical trials of tissue repair, with trials in eye injuries, skin wounds and heart repair after a heart attack ongoing or planned. The FDA stresses the two are not the same substance, so those findings do not carry over. The first registered human trial of TB-500, a placebo-controlled safety study in 80 adults with stable heart disease in China, began recruiting in February 2026 and has posted no findings.

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How we grade evidence

  1. Strong human evidence

    Consistent results from large randomized controlled trials in people.

  2. Limited human evidence

    Some studies in people, but they are small, short, early-phase or uncontrolled.

  3. Mixed evidence

    Studies in people disagree, or strong evidence for one use sits beside weak evidence for another.

  4. Animal or lab studies only · this page

    Studied in cells or animals, not properly in people. Animal results may not apply to humans.

The grade describes how much research exists and in whom. It is not a judgment that a compound works or is safe.

Side effects and safety

Safety in humans is unknown. The FDA found no human exposure data for TB-500 by any route and no animal toxicity studies, and said it is particularly concerned about that absence. It warns that injected peptides like TB-500 can trigger immune reactions, made more likely by clumping (aggregation) and impurities. Its adverse event database had no TB-500 reports through March 26, 2025, and a second FDA database had two cases of blended TB-500 and BPC-157 with no safety assessment. A later FDA search found one report of skin and gum darkening with a BPC-157 and TB-500 product sold for research. Tests for impurities, aggregates, microbial quality and bacterial endotoxin in TB-500 are not publicly available, and the products the FDA found online were powders labeled for research use only. A 2026 review of these peptides found rigorous human safety data scarce and warned of potential for serious harm.

Sources1289

Vial math

Pre-filled calculators turn your vial, water and prescribed dose into syringe units.

Pre-filled for your vial size

These pages do the arithmetic for a vial you already have. They don’t suggest a dose.

This is arithmetic, not medical advice. Confirm with your prescriber or pharmacist.

Questions people ask

What are the side effects of TB-500?

They are unknown, because no human study of TB-500 has been published. The FDA’s adverse event database had no TB-500 reports through March 2025, but absence of reports is not evidence of safety when nobody has studied it. The FDA’s main concerns are immune reactions to injected peptide, made worse by clumping and impurities, and the lack of any toxicity studies. One later report described darkening of the skin and gums with a product containing both BPC-157 and TB-500; the FDA could not tell which peptide was responsible.

Sources

Is TB-500 the same as thymosin beta-4?

No. Thymosin beta-4 is a natural protein of 43 amino acids. TB-500 is a synthetic piece of it, 7 amino acids long (residues 17 to 23, Ac-LKKTETQ). The FDA notes that websites often call TB-500 a synthetic version of thymosin beta-4 and use the names interchangeably, but says they are not the same substance. Research on thymosin beta-4 does not show what TB-500 does.

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Is TB-500 being tested in human trials?

One trial has started. Registered in March 2026, it is a phase 1/2, randomized, double-blind study in China comparing TB-500 with placebo in 80 adults with stable atherosclerotic heart disease. Its main measures are side effects and serious adverse events. It was recruiting as of October 2026 and has posted nothing yet. Before it, the FDA found no published report of TB-500 given to people.

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Is TB-500 FDA-approved or legal?

TB-500 is not FDA-approved, is not in any FDA-approved drug and has no official drug standard (USP monograph). No outsourcing facility has reported compounding it to the FDA. In July 2026 FDA staff recommended against letting pharmacies compound it, citing no human data and the risk of immune reactions; the advisory committee narrowly voted the other way. That vote is not binding. The FDA would have to publish a proposed rule first, and as of October 16, 2026 it had not.

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Is TB-500 banned in sport, and can tests detect it?

Yes. WADA’s 2026 Prohibited List bans “Thymosin-ß4 and its derivatives e.g. TB-500” at all times, in and out of competition (class S2.3, non-specified). WADA approved a project in 2013 to build TB-500’s breakdown products into peptide screening, and anti-doping chemists have described a way to detect it in plasma and urine. In horse studies, TB-500 and its breakdown products were found in blood and urine after injection under the skin. No half-life in people has been published.

Sources

What is the difference between BPC-157 and TB-500?

They are different molecules. BPC-157 has 15 amino acids and is based on a protein in gastric juice; TB-500 has 7 and comes from thymosin beta-4. BPC-157 has five small human studies; TB-500 has none published. The FDA reviewed BPC-157 for ulcerative colitis and TB-500 for wound healing, and its staff recommended against both. WADA bans both, under different classes. No controlled human trial has tested them together; BPC-157 and TB-500 together covers what is known about the combination. If you already have a blended vial, the blend calculator shows how much of each is in every unit.

Sources

Sources

  1. Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety RisksU.S. Food and Drug Administration, 2026 · Accessed Oct 16, 2026 (opens in a new tab)
  2. FDA Briefing Document for TB-500-Related Bulk Drug Substances (PCAC, July 23-24, 2026)U.S. Food and Drug Administration, 2026 · Accessed Oct 16, 2026 (opens in a new tab)
  3. July 23-24, 2026: Meeting of the Pharmacy Compounding Advisory CommitteeU.S. Food and Drug Administration, 2026 · Accessed Oct 16, 2026 (opens in a new tab)
  4. FDA advisers narrowly vote to add 6 peptides to a drug compounding list. What’s next?ABC News, 2026 · Accessed Oct 16, 2026 (opens in a new tab)
  5. World Anti-Doping Code International Standard: Prohibited List 2026World Anti-Doping Agency, 2026 · Accessed Oct 16, 2026 (opens in a new tab)
  6. Advances in the basic and clinical applications of thymosin β4Expert Opin Biol Ther, 2015 · Accessed Oct 16, 2026 (opens in a new tab)
  7. TB-500 (Thymosin Beta 4 17-23 Fragment) for Cardiovascular Biomarkers in Stable Atherosclerotic Cardiovascular Disease, NCT07487363ClinicalTrials.gov, 2026 · Accessed Oct 16, 2026 (opens in a new tab)
  8. FDA Briefing Document for BPC-157-Related Bulk Drug Substances (PCAC, July 23-24, 2026)U.S. Food and Drug Administration, 2026 · Accessed Oct 16, 2026 (opens in a new tab)
  9. Safety and Efficacy of Approved and Unapproved Peptide Therapies for Musculoskeletal Injuries and Athletic PerformanceSports Med, 2026 · Accessed Oct 16, 2026 (opens in a new tab)
  10. Synthesis and characterization of the N-terminal acetylated 17-23 fragment of thymosin beta 4 identified in TB-500, a product suspected to possess doping potentialDrug Test Anal, 2012 · Accessed Oct 16, 2026 (opens in a new tab)

Related compounds

Guides

Medical review in progressLast reviewed

Every medical and regulatory statement on this page links to a checkable source, listed above. Peptinote does arithmetic and education, not medical advice, and never sells or links to sellers of peptides.

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