TB-500
TB-500 is a synthetic heptapeptide (Ac-LKKTETQ-OH) modeled on the actin-binding domain of Thymosin beta-4 (Tβ4), a 43-amino-acid protein studied preclinically for roles in cell migration, wound healing, and angiogenesis.
TB-500 reconstitution calculator
Open full calculator →Typical dosing
| Goal | Range | Route | Frequency |
|---|---|---|---|
| Validated human dosing for the TB-500 fragment | None established | n/a | No completed, published human trial of Ac-LKKTETQ-OH — every circulating figure is informal |
| Community protocol (no trial basis) | 2-2.5 mg | SubQ | 2x weekly loading phase, then weekly maintenance |
| Full-length Thymosin beta-4 — Phase 1 safety study in 40 healthy volunteers (Ruff et al. 2010) | 42, 140, 420 or 1260 mg (ascending cohorts) | IV | Single dose, then the same dose daily for 14 days; no dose-limiting toxicity — note this is the 43-aa protein, not TB-500 |
| Full-length Thymosin beta-4 — topical ophthalmic (RGN-259), dry eye and neurotrophic keratopathy trials | 0.1% ophthalmic solution | Topical eye drops | 5-6x daily for ~28 days in published trials |
| Anti-doping status | Any amount | Any route | Prohibited by WADA at all times, in and out of competition |
Ranges compiled from research literature — not a prescription.
How it works
Thymosin beta-4 (Tβ4) is a naturally occurring 43-amino-acid, G-actin-sequestering protein present in nearly all mammalian tissue and cell types. Its actin-binding region spans roughly residues 17-22, where it reversibly binds monomeric G-actin and modulates the equilibrium between G-actin and filamentous F-actin, a process central to cytoskeletal remodeling, cell shape change, and cell migration.
TB-500 is a synthetic peptide fragment, Ac-LKKTETQ-OH, corresponding to residues 17-23 of Tβ4 and encompassing its actin-binding motif. It is marketed as a smaller, more stable stand-in for the full protein that is intended to reproduce Tβ4's actin-regulating activity in a lab-synthesizable form.
In animal and cell-culture studies, full-length Tβ4 has been reported to accelerate dermal re-epithelialization and wound contraction, increase capillary ingrowth and collagen deposition, support corneal epithelial healing and reduce inflammation in keratitis models, and promote cardiomyocyte migration and survival after simulated myocardial infarction via an integrin-linked-kinase/Akt signaling pathway, alongside stimulation of epicardial-derived neovascularization in rodent and ex vivo heart tissue.
A key honesty point: the large majority of this mechanistic and efficacy evidence — the wound-healing, cardiac-repair, and corneal studies cited below — was conducted with the full 43-amino-acid Tβ4 protein or engineered variants, not with the isolated 7-residue TB-500 fragment sold under that name. A 2026 scoping review found no completed, published human clinical trials specifically evaluating TB-500. Whether the short fragment reproduces the full protein's pharmacology, pharmacokinetics, or safety profile in humans has not been established; extrapolation from full-length Tβ4 animal data to the synthetic TB-500 fragment used in research/gray-market settings remains unproven.
Side effects & safety
- No published human clinical trials exist for the TB-500 fragment specifically; human safety and efficacy are unknown and are extrapolated only from full-length Tβ4 animal studies.
- Preclinical tolerability data come from rodent and ex vivo/in vitro models; long-term effects, immunogenicity, and carcinogenic or proliferative risk in humans have not been studied.
- Product purity and sourcing vary widely in the unregulated research-chemical market; contamination, incorrect concentration, and mislabeling are documented risks since these products are not pharmaceutical-grade or FDA-inspected.
- TB-500/thymosin beta-4 is prohibited by the World Anti-Doping Agency (WADA) at all times; competitive athletes risk sanctions from any detectable use.
- TB-500 is not FDA-approved for any human indication. Its compounding status has been under active FDA/Pharmacy Compounding Advisory Committee review in 2026, leaving it in a regulatory gray zone.
- This is not medical advice; consult a licensed clinician before considering use, especially given the absence of human dosing, interaction, or safety data.
Research
Primary sources — PubMed.
- Bock-Marquette I, et al. Thymosin beta4 activates integrin-linked kinase and promotes cardiac cell migration, survival and cardiac repair. Nature. 2004. https://pubmed.ncbi.nlm.nih.gov/15565145/
- Smart N, et al. Thymosin beta-4 is essential for coronary vessel development and promotes neovascularization via adult epicardium. Ann N Y Acad Sci. 2007. https://pubmed.ncbi.nlm.nih.gov/17495252/
- Sosne G, et al. Thymosin beta 4: a novel corneal wound healing and anti-inflammatory agent. Clin Ophthalmol. 2007. https://pmc.ncbi.nlm.nih.gov/articles/PMC2701135/
- Progress on the Function and Application of Thymosin β4 (review). Front Endocrinol. 2021. https://www.frontiersin.org/journals/endocrinology/articles/10.3389/fendo.2021.767785/full
- Thymosin Beta-4 and TB-500 in Tissue Healing, Regeneration, and Musculoskeletal Repair: A Scoping Review. Appl Sci. 2026. https://www.mdpi.com/2076-3417/16/12/6202
- U.S. FDA. Bulk Drug Substances Used in Compounding Under Section 503A of the FD&C Act. https://www.fda.gov/drugs/human-drug-compounding/bulk-drug-substances-used-compounding-under-section-503a-fdc-act