TB-500
Thymosin Beta-4 fragment · Ac-LKKTETQ · TB500 · Thymosin β4 (17-23)
- healing
- tendon
- muscle
- cardiac
- actin
- angiogenesis
- anti-inflammatory
TB-500 is a synthetic, N-acetylated heptapeptide (Ac-LKKTETQ) corresponding to the actin-binding fragment (residues 17-23) of thymosin beta-4 (Tβ4), a naturally occurring 43-amino-acid peptide involved in tissue repair, cell migration, and angiogenesis. It is frequently marketed as 'Thymosin Beta-4,' but the two are not identical. TB-500 is not FDA-approved, is prohibited in sport, and has no completed human efficacy trials as of 2026.
There is an important distinction often blurred in the marketplace: full-length thymosin beta-4 (Tβ4) is a 43-amino-acid endogenous peptide (CAS 77591-33-4, MW ~4963 Da) that is among the most abundant G-actin-sequestering molecules in mammalian cells and has a substantial independent research literature, including cardiac-repair and wound-healing work. 'TB-500' as sold by research-chemical vendors is typically the much smaller synthetic heptapeptide Ac-LKKTETQ (CAS 885340-08-9, MW ~878 Da), the N-acetylated active actin-binding fragment. Most of the strong basic science (cardiac regeneration, corneal/dermal wound healing) was conducted on full-length Tβ4 or its pharmaceutical formulation (RGN-259), not on the LKKTETQ fragment specifically. Evidence for systemic injectable TB-500 in musculoskeletal injury is preclinical and anecdotal; no completed randomized controlled trials exist for that use as of 2026. TB-500 is commonly stacked with BPC-157 (informally the 'Wolverine stack'), again without controlled human data.
Mechanism of Action
The parent peptide thymosin beta-4 acts primarily by sequestering globular (G-)actin, modulating actin dynamics, cell migration, angiogenesis, and inflammation. In cardiac models, Tβ4 forms a complex with PINCH and integrin-linked kinase (ILK), activating the survival kinase Akt and promoting cardiomyocyte survival and migration. The LKKTETQ fragment (TB-500) corresponds to the actin-binding site and is proposed to retain much of this actin-related activity, though fragment-specific mechanistic data are more limited than for the full peptide.
For research and educational purposes only. This is not medical advice. TB-500 is not approved by the FDA for any use and is prohibited in sport. Consult a licensed healthcare provider before using any peptide.