TB-500

It is like quoting a glowing review of a whole novel to sell a single torn-out page. Thymosin beta-4 has been through human trials; TB-500 is just one fragment of it, tested mostly in mice, yet sold as if the full book's evidence applies.

Thymosin beta-4 is the body's main actin-sequestering peptide and orchestrates cytoskeletal remodelling, cell migration, angiogenesis, anti-apoptotic signalling and dampening of inflammation and fibrosis in injured tissue. TB-500 is the short acetylated 17-23 fragment containing the actin-binding motif (Ac-LKKTETQ), proposed to reproduce some of these regenerative actions. It is typically delivered by injection in grey-market use. Most mechanistic evidence is preclinical; effects demonstrated for the full-length protein cannot be assumed to hold for the fragment.

Research contexts. Not proven uses, and not recommendations.

Thin and often misrepresented. The credible human trials, including Phase 2 dermal ulcer/epidermolysis bullosa studies and the Phase III RGN-259 ophthalmic study in neurotrophic keratopathy, all used full-length thymosin beta-4, not the TB-500 fragment sold to consumers. Those results are at best preliminary and have not produced any approved medicine anywhere. Essentially the only human-relevant data on the TB-500 (17-23) fragment come from anti-doping metabolism and detection studies. The first early-phase human trial of the fragment, a cardiovascular biomarker study, was registered in 2025 and only began recruiting. No robust human efficacy evidence supports the recovery claims made for TB-500.

• !Human efficacy unproven: marketing leans on animal data and on trials of a different (full-length) molecule.
• !Unlicensed in the UK – not an approved or prescribable medicine; sold as a 'research chemical, not for human consumption', so purity, identity and sterility are unverified.
• !Theoretical cancer/angiogenesis concern: a peptide that promotes cell migration and new blood-vessel growth could in principle aid tumour growth or metastasis; this has not been adequately characterised in humans.
• !No established human safety profile, long-term data or quality control for the fragment.
• !Banned at all times by WADA (class S2) – a positive test can end a sporting career; also relevant to drug-tested professions.
• !Grey-market supply means real risk of contamination, mislabelling and incorrect content.

Not a licensed medicine and not approved by the MHRA for any use. There is no marketing authorisation for thymosin beta-4 or the TB-500 fragment. It is not prescribable. In practice it is sold as an unlicensed research chemical labelled 'not for human consumption'. Supplying or marketing it for human use would breach the Human Medicines Regulations 2012.

• · Phase 3· Completed / reported (2023)

  0.1% RGN-259 (Thymosin β4) Ophthalmic Solution in Neurotrophic Keratopathy (SEER-1)

  Used FULL-LENGTH thymosin beta-4, not the TB-500 fragment. Positive epithelial-healing signal in a small cohort; no resulting approval.

• NCT00311766· Phase 2· Completed

  Thymosin Beta 4 on Wound Healing in Patients With Epidermolysis Bullosa

  Full-length Tβ4 dermal wound-healing study.

• NCT07487363· Phase 1/2· Recruiting (registered 2025)

  TB-500 (Thymosin Beta 4 17-23 Fragment) for Cardiovascular Biomarkers in Stable ASCVD

  First trial of the TB-500 fragment itself in humans; biomarker/safety endpoints, no efficacy results yet.

1. 01
   0.1% RGN-259 (Thymosin β4) Ophthalmic Solution Promotes Healing and Improves Comfort in Neurotrophic Keratopathy Patients in a Randomized, Placebo-Controlled, Double-Masked Phase III Clinical Trial, International Journal of Molecular Sciences (2023)

   Human Phase III trial of FULL-LENGTH thymosin beta-4, not the TB-500 fragment – illustrates that the real human data are for the parent peptide.

2. 02
   Synthesis and characterization of the N-terminal acetylated 17-23 fragment of thymosin beta 4 identified in TB-500, a product suspected to possess doping potential — Esposito S et al., Drug Testing and Analysis (2012)

   Confirms TB-500 is the Ac-LKKTETQ (17-23) fragment; the fragment-specific literature is anti-doping/analytical, not efficacy.

3. 03
   Investigation of in vitro/ex vivo TB-500 metabolism, synthesis of relevant metabolites and detection limits in urine and plasma, World Anti-Doping Agency (WADA) funded research (2018)

   Anti-doping work on the TB-500 (17-23) fragment specifically – most fragment-specific human-relevant data are detection/metabolism, not efficacy.

4. 04
   Thymosin Beta 4 on Wound Healing in Patients With Epidermolysis Bullosa, ClinicalTrials.gov (2006)

   Phase 2 dermal wound-healing trial using FULL-LENGTH Tβ4, not the TB-500 fragment.

5. 05
   TB-500 (Thymosin Beta 4 17-23 Fragment) for Cardiovascular Biomarkers in Stable ASCVD, ClinicalTrials.gov (2025)

   First early-phase study of the fragment itself in humans; recruiting from 2025, no efficacy results.