# TB-500: The Research Record, Set in Order — Every Finding Sourced

> TB-500 (Ac-LKKTETQ) is the seven-residue synthetic fragment of thymosin beta-4. 22 peer-reviewed findings across wound healing, cardiac, neurological, and musculoskeletal models — plotted and sourced.

TB-500 (Ac-LKKTETQ) is the synthetic heptapeptide corresponding to the actin-binding domain of thymosin beta-4. This site indexes the peer-reviewed literature: mechanism, findings by tissue, dosage context, safety data, and regulatory status — every claim sourced.

## What Is TB-500?

TB-500 is the synthetic heptapeptide Ac-LKKTETQ — seven amino acids (leucine-lysine-lysine-threonine-glutamate-threonine-glutamine), N-terminally acetylated, corresponding to residues 17–23 of thymosin beta-4 (Tβ4). Molecular weight: 839.0 Da.

Thymosin beta-4 is a 43-amino-acid endogenous protein found in high concentrations in blood platelets, macrophages, and wound fluid. TB-500 is its active fragment — the actin-binding domain. In a foundational 2003 study, Philp et al. demonstrated that the heptapeptide sequence LKKTETQ is sufficient to drive angiogenic activity in vitro at approximately 50 nM, comparable to full-length Tβ4, and that peptides lacking any portion of this sequence show no angiogenic effect [1].

The domain name frames TB-500 not as a product but as a subject: this site is an evidence index, putting the research record into ordered, classified form. The [TB-500 peptide](/research) literature spans wound healing, cardiac protection, neurological repair, and hair follicle biology — all reviewed here with citations.

TB-500 is not approved by the FDA or any equivalent regulatory body for any clinical indication. It is classified as a research compound. WADA and USADA prohibit TB-500 and its parent compound thymosin beta-4 under the Prohibited List (S2.3, Growth Factors) [2].

## What Does TB-500 Do?

In preclinical models, TB-500 and full-length thymosin beta-4 have been studied for four primary activities:

**Actin sequestration.** TB-500's LKKTETQ sequence binds G-actin monomers in a 1:1 complex, reducing the available pool for F-actin polymerization. This modulates cytoskeletal dynamics and promotes cell migration — the foundational mechanism underlying tissue-repair effects [1].

**Akt pathway activation.** Thymosin beta-4 activates integrin-linked kinase (ILK), which forms a complex with PINCH and activates the pro-survival Akt/PKB kinase. In a 2004 mouse myocardial infarction model, this cascade improved cardiomyocyte survival and cardiac function [4].

**NF-κB suppression.** In human corneal epithelial cells stimulated with TNF-alpha, thymosin beta-4 significantly reduced NF-κB nuclear translocation and p65 phosphorylation, independently of its actin-binding function — a distinct anti-inflammatory mechanism [6].

**MMP upregulation.** The central actin-binding domain (residues 17–23, exactly the TB-500 sequence) accounted for all of thymosin beta-4's ability to upregulate MMP-1, MMP-2, and MMP-9 in keratinocytes, endothelial cells, and fibroblasts — the metalloproteinases that remodel extracellular matrix during wound repair [12].

See the full [TB-500 mechanism of action](/research#mechanism) discussion on the research page.

## What Is TB-500 Used For in Research?

The peer-reviewed literature covers five primary research applications:

**Dermal wound healing.** Topical thymosin beta-4 increased wound re-epithelialization by 42% at 4 days and 61% at 7 days in rats versus saline controls, with keratinocyte migration stimulated 2–3-fold in vitro and enhanced collagen deposition [3]. Phase 2 clinical trials in patients with pressure ulcers, stasis ulcers, and epidermolysis bullosa wounds showed accelerated healing and good tolerability [14].

**Cardiac protection.** In mouse myocardial infarction models, thymosin beta-4 improved cardiomyocyte survival via the ILK-PINCH-Akt cascade [4][5]. A 2025 study further showed that Tβ4 in infarcted mouse hearts decreased ROCK1 expression via miR139-5p upregulation, inhibiting fibroblast-to-myofibroblast transformation and limiting pathological fibrosis [RC1].

**Neurological repair.** In rat embolic stroke models, doses of 2–12 mg/kg improved neurological outcome at 14 and 56 days, with an estimated optimal dose of 3.75 mg/kg; the mechanism involves oligodendrocyte development and myelin preservation rather than infarct-size reduction [17]. In traumatic brain injury models initiated 6 hours post-injury, treated animals showed smaller lesions and increased hippocampal neurogenesis [18].

**Musculoskeletal regeneration.** Thymosin beta-4 mRNA is upregulated in regenerating muscle fibers following injury, where it acts as a chemoattractant for myoblasts [10]. In dystrophin-deficient mdx mice, 150 µg twice weekly for 6 months significantly increased regenerating skeletal muscle fibers [9].

**Hair follicle cycling.** Thymosin beta-4 stimulated hair growth in rats and mice through activation of follicle stem cells in the bulge region; rat vibrissa follicle clonogenic keratinocytes showed increased migration at nanomolar concentrations [7][8].

No approved clinical indication for TB-500 in humans exists as of 2026. See [preclinical injury models](/research#injury-models) for full study details and [frequently asked questions](/faq) for common queries.

## TB-500 vs Thymosin Beta-4: A Structural Note

Thymosin beta-4 is 43 amino acids, molecular weight 4921 Da. TB-500 is the 17–23 fragment: 7 amino acids, 839 Da. The N-terminal acetylation of TB-500 confers protection against aminopeptidase degradation and increases aqueous solubility relative to the full-length parent.

The critical finding, established by Philp et al. (2003), is that the LKKTETQ heptapeptide is sufficient for angiogenic and cell-migration activity — no other region of Tβ4 is required for these effects [1]. However, Tβ4 also exerts ILK-Akt activation and NF-κB suppression via domains not present in TB-500. Research results from full-length thymosin beta-4 cannot be assumed to transfer directly to the shorter fragment without experimental confirmation.

Most published mechanistic work uses full-length recombinant or synthetic Tβ4. Published human Phase I safety data is likewise for full-length Tβ4, not the TB-500 fragment specifically. See the full [thymosin beta-4 relationship](/research#thymosin-beta-4) discussion.

TB-500 is also identified as a human exerkine. Mass spectrometry identified Tβ4 as the most upregulated secreted protein in contracting muscle cell media, and plasma levels rose acutely during human exercise across metabolic conditions and exercise modes [19]. This endogenous role in exercise physiology is part of the rationale for its WADA classification as a growth factor.

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The TB-500 research record, ordered — twenty-two findings plotted by evidence class, each citation indexed, no clinic and no vendor behind the grid.