Compound
TB-500, Wounds & Tendons: What Evidence Is Actually Direct
A wound literature exists in this family. Almost none of the usual citations is a direct TB-500 trial.
Common online claims
Commercial pages often claim that TB-500 repairs tendons, closes wounds, or speeds recovery. Those sentences mix three records: full-length thymosin β4, non-acetylated LKKTETQ, and the name TB-500. FDA recorded that mix and rejected it as identity.1
This page does not build a story that “TB-500 heals tendons.” It asks, for each citation, which molecule was studied. If the answer is not Ac-LKKTETQ, the citation is not direct evidence.
Full-length Tβ4 preclinical evidence
Studied moleculeFull-length thymosin β4
Malinda 1999 is a classic example of wound work with thymosin β4, not with TB-500. It measures repair in preclinical models of the 43-amino-acid peptide. It helps explain why a Tβ4 literature exists. It does not label a fragment vial.3
That literature is real and it is preclinical. Animal or culture work does not establish a human treatment, and Tβ4 does not establish TB-500.
Non-acetylated LKKTETQ mouse evidence
Studied moleculeNon-acetylated fragment
Philp 2003 applied thymosin β4 and the non-acetylated heptapeptide LKKTETQ in db/db diabetic mice and in aged mice. The paper reports epidermal closure and collagen content in those models. FDA reads it as pharmacology of the non-acetylated fragment, not as a TB-500 trial.2,1
We do not convert the study’s amounts into a regimen. The topical route in mice matters for classifying the experiment. It does not translate into use instructions.2
Acetylation blocks the leap. FDA states that the profile of non-acetylated LKKTETQ cannot be directly extrapolated to TB-500 because the acetyl group changes charge, hydrophobicity, size, stability, and binding.1,8
Direct TB-500 evidence
Studied moleculeTB-500 / Ac-LKKTETQ
Esposito 2012’s analytical identification says what was in a product called TB-500: Ac-LKKTETQ. That is identity evidence, not tissue-repair evidence.7
The direct wound experiment FDA describes is in vitro. In fibroblasts with a controlled scratch, TB-500 free base did not produce a statistically significant closure difference versus vehicle. A metabolite, N-acetylated LKKTE, produced a small significant effect under the same conditions.4,1
The correct reading is narrow. One laboratory assay, under specific conditions, did not show significant closure for the free base. That does not prove that TB-500 “does not work” in every context. It shows that parent, metabolite, and full-length Tβ4 cannot be merged into one wound claim.
Human TB-500 evidence
FDA did not identify clinical studies or human exposure data using TB-500 in the 2026 evaluation. There is, on that record, no tendon, skin-wound, or other indication trial that administers TB-500 to people.1
Human full-length Tβ4 evidence
Human Tβ4 trials do exist. The dry-eye and venous-ulcer studies are detailed on the human-evidence page. They exist. They are not TB-500 trials. The venous-ulcer study is topical and the dry-eye study is ophthalmic: they do not even share the route the compounding nomination imagined.5,6,1
Tendon-specific claims
We did not identify, for this inventory, a controlled human trial that administers TB-500 and measures a tendon outcome. We also do not convert the Tβ4 or LKKTETQ literature into a generic “TB-500 and tendons” page.
If a text claims that TB-500 repairs ligaments or speeds return to sport, it is using performance language and human-use language. This cluster does not make that claim. The studied molecule, when traced, is usually something else.
FDA listed a long catalog of uses that appear on websites: tissue repair, tendon damage, angiogenesis, inflammation, muscle growth, endurance, hair, dry eye, and more. That list documents marketing. It does not document a TB-500 clinical program. Several of those uses, when they rest on anything, rest on thymosin β4 literature.1
There is also a route mismatch. The compounding nomination imagined a lyophilized powder for injection. The human Tβ4 trials that do exist are ophthalmic or topical. Even if they shared the molecule — and they do not — the route would still not match.1,5,6
Evidence-transfer matrix: which molecule was studied and what that allows for TB-500.
| Study or source | Molecule actually studied | Evidence type | Direct TB-500 evidence? |
|---|---|---|---|
| Esposito 2012 | Ac-LKKTETQ / TB-500 | Analytical identification | Yes for identity. No for clinical efficacy. |
| Ho 2012 | TB-500 in horses | Animal anti-doping analysis | Yes for analytical detection. No for human efficacy. |
| Philp 2003 | Non-acetylated LKKTETQ and full-length thymosin β4 | Mouse preclinical | No. Not human TB-500 evidence. |
| Malinda 1999 | Full-length thymosin β4 | Preclinical wound study | No. This is Tβ4 evidence, not TB-500 evidence. |
| Dry-eye Phase II | Full-length thymosin β4 | Human randomized trial | No. Not a TB-500 trial. |
| Venous-ulcer Phase II | Full-length thymosin β4 | Human trial | No. Not a TB-500 trial. |
| Rahaman 2024 / FDA in vitro | Acetylated TB-500 free base | In vitro | Yes as a direct TB-500 experiment. No as human efficacy evidence. |
References
Regulatory source
Studied moleculeTB-500 / Ac-LKKTETQ
July 23-24, 2026 Pharmacy Compounding Advisory Committee — FDA Briefing Document for TB-500-Related Bulk Drug Substances (TB-500 (free base) and TB-500 acetate)FDA PCAC briefing. 2026
Regulatory source — United States
FDA staff evaluation for a 503A nomination. The Agency stated that it did not identify clinical studies or human exposure data using TB-500. Not a final rule and not drug approval.
Preclinical study — animal
Studied moleculeNon-acetylated fragment
Philp D, Badamchian M, Scheremeta B, Nguyen M, Goldstein AL, Kleinman HK.
Thymosin beta 4 and a synthetic peptide containing its actin-binding domain promote dermal wound repair in db/db diabetic mice and in aged mice.Wound Repair Regen. 2003;11(1):19-24. 2003
DOI 10.1046/j.1524-475x.2003.11105.x
Mouse study of full-length thymosin β4 and the non-acetylated heptapeptide LKKTETQ. Not a TB-500 study and not a human trial.
Preclinical study — animal
Studied moleculeFull-length thymosin β4
Malinda KM, Sidhu GS, Mani H, Banaudha K, Maheshwari RK, Goldstein AL, Kleinman HK.
Thymosin β4 accelerates wound healing.J Invest Dermatol. 1999;113(3):364-368. 1999
DOI 10.1046/j.1523-1747.1999.00708.x
Preclinical wound study of full-length thymosin β4. Not TB-500 and not a human trial.
In-vitro study
Studied moleculeTB-500 / Ac-LKKTETQ
Rahaman KA, Muresan AR, Min H, Son J, Han HS, Kang MJ, Kwon OS.
Simultaneous quantification of TB-500 and its metabolites in in-vitro experiments and rats by UHPLC-Q-Exactive orbitrap MS/MS and their screening by wound healing activities in-vitro.J Chromatogr B Analyt Technol Biomed Life Sci. 2024;1235:124033. 2024
DOI 10.1016/j.jchromb.2024.124033
In-vitro fibroblast scratch assay and analytical work. FDA summarized that TB-500 free base did not differ significantly from vehicle under the tested conditions. Not a human clinical study. Metabolite detection details are not used here as anti-doping operational information.
Human trial — thymosin β4, not TB-500
Studied moleculeFull-length thymosin β4
Sosne G, Ousler GW.
Thymosin beta 4 ophthalmic solution for dry eye: a randomized, placebo-controlled, Phase II clinical trial evaluating the first 28 days of treatment.Clin Ophthalmol. 2015;9:1015-1025. 2015
Reported sample size: 72
Phase II trial of full-length thymosin β4 ophthalmic solution. Primary endpoints were not statistically significant at the specified evaluation. Not a TB-500 trial.
Human trial — thymosin β4, not TB-500
Studied moleculeFull-length thymosin β4
Guarnera G, DeRosa A, Camerini R.
The effect of thymosin treatment of venous ulcers.Ann N Y Acad Sci. 2010;1194:207-212. 2010
DOI 10.1111/j.1749-6632.2010.05490.x
Reported sample size: 73
Phase II study of topical full-length thymosin β4 in venous ulcers. Not a TB-500 trial and not summarized here as established human efficacy for TB-500.
Analytical / anti-doping research
Studied moleculeTB-500 / Ac-LKKTETQ
Esposito S, Deventer K, Goeman J, Van der Eycken J, Van Eenoo P.
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 potential.Drug Test Anal. 2012;4(9):733-738. 2012
Analytical identification of Ac-LKKTETQ in TB-500 for anti-doping purposes. Not a human clinical efficacy study.
Scientific reference
Ree R, Varland S, Arnesen T.
Spotlight on protein N-terminal acetylation.Exp Mol Med. 2018;50(7):1-13. 2018
General biochemistry of N-terminal acetylation. Cited for why acetylation can change peptide properties, not as TB-500 efficacy evidence.
Peptra Health materials are for laboratory research use only. This article is educational and is not medical advice.
Related research
- TB-500 and LKKTETQ: Understanding the Thymosin β4 Fragment
LKKTETQ names one fragment. Ac-LKKTETQ names another. A proposed mechanism is not a healing proof.
- TB-500 in Humans: What Studies Actually Exist
Short answer: on FDA’s 2026 review, there is no direct human TB-500 evidence.
Related documentation
Note on nomenclature: the commercial name TB-500 has been used for materials with different molecular descriptions. A lot’s analytical documentation must be reviewed separately and does not automatically imply equivalence with the molecular identity described in the literature or in regulatory documents.