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Research information only. Not medical advice. 18+ only. Not FDA-approved for human therapeutic use.

TB-500 Fragment (17-23)

Also known as: LKKTETQ, Thymosin Beta-4 Fragment 17-23, Tβ4 fragment, TB4 fragment 17-23, Ac-LKKTETQ, N-acetyl-LKKTETQ

Peptide fragment — actin-sequestering heptapeptide derived from Thymosin Beta-4 (Tβ4); amino acids 17–23 of the full 43-amino-acid parent sequence

Research chemicalLast updated: October 10, 2026Based on 7 peer-reviewed studiesPreclinical data only — no human trials
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What it is

TB-500 Fragment (17-23) is the seven-amino-acid core of the healing peptide TB-500, used by athletes and biohackers for injury recovery and tissue repair. It works by binding actin to drive cell migration, new blood vessel formation, and reduced scarring at wound sites. It is not FDA-approved, and community protocols for the isolated fragment are less established than for full TB-500.

The scientific side

TB-500 Fragment (17-23) — sequence LKKTETQ — is the actin-binding domain of the full Thymosin Beta-4 protein. Its primary biochemical role is sequestering G-actin (monomeric actin), which keeps the cytoskeleton in a dynamic state that allows cells to migrate. This cell migration activity underpins several downstream biological effects: wound healing, angiogenesis, and anti-fibrotic signalling. Research confirms the LKKTETQ heptapeptide retains wound-healing and angiogenic activity comparable to the full 43-amino-acid parent molecule (PMID 12581423, PMID 20179146). In diabetic and aged mice, subcutaneous application of synthetic LKKTETQ accelerated full-thickness dermal wound closure to a degree matching intact Thymosin Beta-4 (PMID 12581423). In hepatic stellate cells, the 17-23 fragment — but not the 1-15 fragment — specifically blocked PDGF-BB-driven activation, proliferation, and Akt phosphorylation, identifying the actin-binding domain as the anti-fibrogenic effector region (PMID 30063851). Metabolic studies in rats found the fragment is rapidly cleaved in serum; the primary detected metabolite is Ac-LK, with the intermediate Ac-LKKTE also detected, and evidence suggests wound-healing activity may be partly mediated by these metabolites rather than the intact parent heptapeptide (PMID 38382158). Cell biology studies show that actin-binding competence is required for LKKTETQ's cytoskeletal effects, and nuclear shuttling of the peptide follows passive but regulated diffusion (PMID 17567947). The fragment has also been incorporated into an enzyme-instructed self-assembling hydrogel (ALP-triggered EISA) for corneal alkali burn repair, where it accelerated epithelial regeneration and reduced inflammation in animal models (PMID 41359360). No cytotoxicity of the parent fragment or its metabolites was detected in rat pharmacokinetic studies (PMID 38382158).

Class: Peptide fragment — actin-sequestering heptapeptide derived from Thymosin Beta-4 (Tβ4); amino acids 17–23 of the full 43-amino-acid parent sequence

Administration & storage

Administration
subcutaneous (inferred from animal study context)topical hydrogel (PMID 41359360experimental)
Storage
No storage data described in reviewed abstracts. By analogy with peptide standards: lyophilised powder stored at -20°C; reconstituted solution used promptly or refrigerated at 4°C for short-term use.
Cautions
No cytotoxicity detected in rat in vitro / in vivo metabolic studies (PMID 38382158), but this is insufficient for human safety conclusions.,No human clinical trial data identified in any reviewed source.,The parent compound TB-500 is banned by WADA; the fragment is detectable in plasma and urine by validated anti-doping methods (PMIDs 23084823, 23318763).,Rapid in vivo proteolysis to Ac-LK and Ac-LKKTE means the active species in vivo may differ from the administered peptide (PMID 38382158).,No data on immunogenicity, long-term safety, carcinogenicity, or drug interactions in humans.

Legal & regulatory status

US FDA

Not approved. The parent compound Thymosin Beta-4 / TB-500 is not FDA-approved for any indication. The isolated fragment LKKTETQ is not separately reviewed or approved by the FDA. No IND or NDA identified in reviewed…

WADA

Not explicitly confirmed for the fragment in reviewed literature. The parent compound Thymosin Beta-4 / TB-500 is prohibited under WADA's Prohibited List (S2 — Peptide Hormones, Growth Factors, Related Substances and…

Health Canada

Not stated in reviewed literature — requires manual verification. The fragment is not listed as an approved drug in Canada. As a synthetic peptide fragment sold outside pharmaceutical channels it would be regulated as…