TB-500

Overview

TB-500 is a synthetic N-acetylated heptapeptide (Ac-LKKTETQ) corresponding to amino acids 17–23 of thymosin β4, the actin-binding region of the native 43-residue protein. Despite widespread vendor labeling, TB-500 is NOT identical to full-length thymosin β4 (Tβ4); it is a short 7-amino-acid fragment. It is sold as a research chemical, is not FDA-approved for any human indication, and is banned by WADA.

Mechanism of Action

Native thymosin β4 is the principal G-actin–sequestering peptide in mammalian cells, regulating cytoskeletal dynamics and cell migration. Preclinically Tβ4 promotes endothelial and epithelial cell migration, angiogenesis, ILK/Akt survival signaling, and downregulation of pro-inflammatory cytokines. The TB-500 fragment retains the actin-binding motif, but whether it fully reproduces Tβ4's activity in humans has not been established.

Research Summary

Animal studies of full-length Tβ4 show accelerated dermal wound reepithelialization (Malinda et al., 1999, PMID 10469335), increased angiogenesis, improved cardiac function after ischemic injury via an ILK/Akt pathway (Bock-Marquette et al., Nature 2004, PMID 15565145), and corneal healing (Sosne & Kleinman review, 2015, PMID 26241398). The short Ac-LKKTETQ peptide sold as TB-500 was characterized analytically in the anti-doping literature as a substance with suspected doping potential (Esposito et al., 2012, PMID 22962027); controlled human efficacy trials of injected TB-500 do not exist. Full-length synthetic Tβ4 (RGN-259) has been evaluated in Phase II/III ophthalmic trials for dry eye disease and neurotrophic keratopathy with mixed results — one Phase III NK trial met healing endpoints, while a later European Phase III missed its primary endpoint. No clinically validated human injection dose exists for the short TB-500 peptide; all circulating dosing figures derive from vendor and forum protocols, not controlled trials.

Vendors selling TB-500

Scored vendors carrying TB-500, ranked by trust grade. Grades are computed from indexed Certificates of Analysis. Full $/mg pricing is on the comparison page.

Prescribers who offer TB-500

252 prescribers in our directory work with TB-500, each confirmed from their own website. Peptides like TB-500 require a prescription from a licensed provider — telehealth options are available.

Reported Side Effects

• Injection site reactions
• Headache and lethargy reported anecdotally
• Theoretical risk of promoting growth of occult tumors via angiogenesis and cell migration (not established in humans)
• Unknown long-term safety profile in humans

Biomarkers researchers track for TB-500

These biomarkers appear in the research literature as measures of response and safety for this compound.

Related Peptides

Research Guides

• Cheapest verified TB-500: live prices, vendors & COA data

Compare TB-500 with Others

Research References

• Malinda KM, et al. Thymosin beta4 accelerates wound healing. FASEB J / J Invest Dermatol. 1999. PMID 10469335.
• Bock-Marquette I, et al. Thymosin beta4 activates ILK and promotes cardiac cell migration, survival and repair. Nature. 2004;432(7016):466-472. PMID 15565145.
• Sosne G, Kleinman HK. Primary mechanisms of thymosin β4 repair activity in dry eye disorders and other tissue injuries. 2015. PMID 26241398.
• Esposito S, et al. Synthesis and characterization of the N-terminal acetylated 17-23 fragment of thymosin beta 4 identified in TB-500. 2012. PMID 22962027.

Frequently asked questions

Has TB-500 been independently lab-tested?

Disclosed Labs has collected 188 Certificates of Analysis (COA) for TB-500 from 16 independent testing labs. 42 vendors have submitted material for testing. Products average 99.3% tested purity across the corpus. Full testing data is available at https://www.disclosedlabs.com/peptides/tb-500/testing.

What is the average purity of TB-500 on the market?

Based on 188 COAs analyzed by Disclosed Labs, TB-500 products average 99.3% (±1.8%) tested purity. Individual vendor results vary; see per-vendor COA data at https://www.disclosedlabs.com/peptides/tb-500/coas.

Which labs have tested TB-500?

Independent labs that have tested TB-500 include: ILS Labs (Grade A), Ethos Analytics (Grade B). Full lab credibility grades and profiles are at https://www.disclosedlabs.com/labs.

Where can researchers source TB-500?

8 vendors with Disclosed Labs trust grades currently list TB-500, including Glacier Aminos, Peptide Partners, OROS Research. Compare live prices and lab-verified COAs at https://www.disclosedlabs.com/prices/tb-500.

Which prescribers offer TB-500 with a prescription?

252 prescribers in the Disclosed Labs directory work with TB-500, each confirmed from their own website, with telehealth options available. TB-500 requires a prescription from a licensed provider. Browse them at https://www.disclosedlabs.com/prescribers?peptide=TB-500.

How does TB-500 work?

Native thymosin β4 is the principal G-actin–sequestering peptide in mammalian cells, regulating cytoskeletal dynamics and cell migration. Preclinically Tβ4 promotes endothelial and epithelial cell migration, angiogenesis, ILK/Akt survival signaling, and downregulation of pro-inflammatory cytokines. The TB-500 fragment retains the actin-binding motif, but whether it fully reproduces Tβ4's activity in humans has not been established.

What does the research say about TB-500?

Animal studies of full-length Tβ4 show accelerated dermal wound reepithelialization (Malinda et al., 1999, PMID 10469335), increased angiogenesis, improved cardiac function after ischemic injury via an ILK/Akt pathway (Bock-Marquette et al., Nature 2004, PMID 15565145), and corneal healing (Sosne & Kleinman review, 2015, PMID 26241398). The short Ac-LKKTETQ peptide sold as TB-500 was characterized analytically in the anti-doping literature as a substance with suspected doping potential (Esposito et al., 2012, PMID 22962027); controlled human efficacy trials of injected TB-500 do not exist. Full-length synthetic Tβ4 (RGN-259) has been evaluated in Phase II/III ophthalmic trials for dry eye disease and neurotrophic keratopathy with mixed results — one Phase III NK trial met healing endpoints, while a later European Phase III missed its primary endpoint. No clinically validated human injection dose exists for the short TB-500 peptide; all circulating dosing figures derive from vendor and forum protocols, not controlled trials.