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How TB-500 Works: Mechanism and Pharmacology

How TB-500 works: its target and mechanism as the sources state them, how long it acts, and what is still unknown.

Medical review pendingSynthetic fragment of thymosin beta-4Updated
Class
Synthetic fragment of thymosin beta-4
FDA status
Not approved
Off Category 2, 15 Apr 2026
Routes studied
intraperitoneal; local, in the ligament gap; topical hydrogel at the wound
Half-life
[pending]
by route, with source

How long it acts

No published half-life found for TB-500 (PubMed search, 11 Oct 2026)

Full detail, including drug-testing windows, is on the TB-500 half-life page.

Where the TB-500 sequence sits in the protein

TB-500 is the acetylated form of the seven-amino-acid segment LKKTETQ, which a doping-control paper calls the active site of thymosin beta-4 responsible for actin binding, cell migration and wound healing.[10]

The same paper lists what TB-500 is claimed to do, which are claims and not findings.[10]

What full-length thymosin beta-4 did in cell and mouse work

In mouse myoblast cultures, full-length thymosin beta-4 and its sulphoxide form accelerated wound closure and increased chemotaxis.[11]

In mice that overexpress thymosin beta-4, VEGF and the P38, ERK and AKT signalling proteins were raised, and they were lower in knockout mice.[12]

In mice with induced cardiac injury, recombinant full-length thymosin beta-4 prevented cardiac dysfunction and fibrosis, and the authors tied the effect to ErbB2 signalling.[13]

What was seen with TB-500 itself

In rats with a repaired tendon, TB-500 was associated with improved histopathology and matrix organisation; the authors called the model exploratory.[14]

What is unknown

There is no label for TB-500 or thymosin beta-4: the Drugs@FDA lookup returned no matches on 2 October 2026, so no regulator-written mechanism section exists.

Calculated from source s2-legal/api.fda.gov/drugsfda-thymosin-beta.txt; matches 0. Formula: Drugs@FDA matches = 0

Related peptides

TB-500 vs BPC-157Gastric pentadecapeptide

Common questions

How long does TB-500 act in the body?

We found no published half-life for TB-500 (PubMed search, 11 Oct 2026), so how long it acts is unknown.

How does TB-500 work?

The sequence is described as the actin-binding active site of thymosin beta-4; what it does in people is not established.[10]

More on TB-500

DosageDoses used in published studies, with the source for each.CalculatorVial, water and dose to syringe units.Side effectsWhat labels and studies report, and what is unknown.ResultsStudy outcomes and when they were measured.BenefitsClaimed benefits next to what published studies measured.TopicalStudies that gave TB-500 as creams and serums, and what is approved.

Sources

  1. 1PubMed search: ("TB-500"[tiab] OR TB500[tiab] OR "thymosin beta-4"[tiab] OR "thymosin beta4"[tiab] OR Tbeta4[tiab]) (1199 results)PubMed · 2026pubmed.ncbi.nlm.nih.govAccessed 2 Oct 2026
  2. 2PubMed search: ("TB-500"[tiab] OR TB500[tiab] OR "thymosin beta-4"[tiab] OR "thymosin beta4"[tiab] OR Tbeta4[tiab]) AND (humans[mh] OR patients[tiab]) (678 results)PubMed · 2026pubmed.ncbi.nlm.nih.govAccessed 2 Oct 2026
  3. 3PubMed search: ("TB-500"[tiab] OR TB500[tiab] OR "thymosin beta-4"[tiab] OR "thymosin beta4"[tiab] OR Tbeta4[tiab]) AND (randomized[tiab] OR clinical trial[pt]) (18 results)PubMed · 2026pubmed.ncbi.nlm.nih.govAccessed 2 Oct 2026
  4. 4PubMed search: ("TB-500"[tiab] OR TB500[tiab] OR "thymosin beta-4"[tiab] OR "thymosin beta4"[tiab] OR Tbeta4[tiab]) AND (half-life[tiab] OR pharmacokinetic*[tiab]) (16 results)PubMed · 2026pubmed.ncbi.nlm.nih.govAccessed 2 Oct 2026
  5. 5PubMed search: ("TB-500"[tiab] OR TB500[tiab] OR "thymosin beta-4"[tiab] OR "thymosin beta4"[tiab] OR Tbeta4[tiab]) AND (wound[tiab] OR dermal[tiab] OR skin[tiab] OR hair[tiab]) (212 results)PubMed · 2026pubmed.ncbi.nlm.nih.govAccessed 2 Oct 2026
  6. 6PubMed search: ("TB-500"[tiab] OR TB500[tiab] OR "thymosin beta-4"[tiab] OR "thymosin beta4"[tiab] OR Tbeta4[tiab]) AND (tendon[tiab] OR muscle[tiab] OR cardiac[tiab] OR myocardial[tiab] OR heart[tiab]) (246 results)PubMed · 2026pubmed.ncbi.nlm.nih.govAccessed 2 Oct 2026
  7. 7PubMed search: "TB-500"[tiab] OR TB500[tiab] OR "Ac-LKKTETQ"[tiab] (33 results)PubMed · 2026pubmed.ncbi.nlm.nih.govAccessed 2 Oct 2026
  8. 8PubMed search: ("TB-500"[tiab] OR TB500[tiab] OR "thymosin beta-4"[tiab] OR "thymosin beta4"[tiab] OR Tbeta4[tiab] OR RGN-259[tiab] OR RGN-137[tiab]) AND (adverse[tiab] OR "side effect*"[tiab] OR safety[tiab] OR tolerab*[tiab] OR toxicity[tiab] OR "case report"[pt]) (61 results)PubMed · 2026pubmed.ncbi.nlm.nih.govAccessed 11 Oct 2026
  9. 9PubMed search: ("RGN-259"[tiab] OR "RGN-137"[tiab] OR "thymosin beta 4"[tiab]) AND (eye[tiab] OR ophthalmic[tiab] OR neurotrophic[tiab] OR cornea*[tiab]) AND (patients[tiab] OR trial[tiab]) (15 results)PubMed · 2026pubmed.ncbi.nlm.nih.govAccessed 11 Oct 2026
  10. 10Doping control analysis of TB-500, a synthetic version of an active region of thymosin β₄, in equine urine and plasma by liquid chromatography-mass spectrometry.Journal of chromatography. A · 2012PMID 23084823Accessed 2 Oct 2026
  11. 11Muscle injury-induced thymosin β4 acts as a chemoattractant for myoblasts.Journal of biochemistry · 2011PMID 20880960Accessed 2 Oct 2026
  12. 12Thymosin Beta-4 Induces Mouse Hair Growth.PloS one · 2015PMID 26083021Accessed 2 Oct 2026
  13. 13Recombinant human thymosin beta 4 improves ischemic cardiac dysfunction in mice and patients with acute ST-segment elevation myocardial infarction after reperfusion.Cardiovascular research · 2025PMID 41229390Accessed 2 Oct 2026
  14. 14Effects of BPC-157 and TB-500 on Achilles tendon healing in rats: A histopathological and biomechanical study.Joint diseases and related surgery · 2026PMID 42542926Accessed 2 Oct 2026

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