TB-500 and thymosin beta-4: research summary and UK status

Searches for TB-500 in the UK fall into three groups: people asking what it is and whether it is the same as thymosin beta-4, people asking about results and side effects, and people asking whether it is legal to buy. This guide answers all three from the published literature. It is written for readers who want to understand the compound as a research subject, not for anyone looking for a protocol. Free Muscle sells TB-500 for laboratory research only, to adults, and nothing here is guidance on using it.

What is TB-500?

Thymosin beta-4 (Tβ4) is a 43-amino-acid protein found in almost every human cell, where it is the main protein that binds monomeric actin and so controls how a cell assembles its internal skeleton. That housekeeping role turns out to matter for cell migration, blood vessel formation and the response to injury, which is why the protein has been studied in wound models for three decades (Goldstein 2005).

TB-500 is not the full protein. When doping-control chemists at Ghent University analysed a commercial TB-500 preparation in 2012, they identified its active ingredient as a short peptide covering residues 17 to 23 of thymosin beta-4 with an acetyl group on the N-terminus, written Ac-LKKTETQ (Esposito 2012). A Hong Kong racing laboratory reached the same conclusion the same year while building a test for the horse-racing market, describing TB-500 as a veterinary preparation built around that seven-residue actin-binding segment (Ho 2012). So when a listing says TB-500 is thymosin beta-4, the honest version is that it is a synthetic fragment of thymosin beta-4 carrying the actin-binding motif, and that most of the biology below concerns the full protein rather than the fragment.

Is thymosin beta-4 a steroid?

No. It is a peptide, a chain of amino acids, with no structural relationship to steroid hormones and no action at the androgen receptor. It is also not a SARM. It sits in a different regulatory and pharmacological category from both, which matters for the legal and sport sections below.

How thymosin beta-4 works

The mechanism that is best established is actin sequestration. By holding a reserve of unpolymerised actin, thymosin beta-4 sets how quickly a cell can extend, retract and move, and migrating cells are the first step in closing a wound. Beyond that, the 2004 Nature paper from Srivastava's group reported that thymosin beta-4 forms a complex with the proteins PINCH and integrin-linked kinase, activating the survival kinase Akt, and that after coronary artery ligation in mice the protein was associated with better early cardiomyocyte survival and improved cardiac function (Bock-Marquette 2004). Other laboratories have reported anti-inflammatory signalling and effects on hair follicle and corneal epithelial cells (reviewed in Goldstein 2005). Whether the seven-residue fragment reproduces all of this is not established; the fragment carries the actin-binding motif but not the rest of the protein.

What the published research reports

Animal and cell studies

The animal literature is the largest part of the evidence. Full-thickness skin wounds in rats closed faster with topical or intraperitoneal thymosin beta-4, with more collagen deposited and keratinocytes migrating further into the wound (summarised in Goldstein 2005). Corneal injury models in mice and rats showed faster epithelial repair. The cardiac work described above was done in mice. In every case the material was the full protein, delivered by injection or applied directly to the tissue, in animals, at quantities and by routes with no relation to any capsule product. Animal wound models are also a setting where many candidate molecules look promising and later fail in people.

Human trials of thymosin beta-4

A US biotechnology company has taken full-length thymosin beta-4 into early clinical trials. A European double-blind, placebo-controlled study applied it topically to venous leg ulcers in Italy and Poland, with the stated aim of assessing safety, tolerability and healing (Guarnera 2007); the published paper is a design report on an ongoing study rather than an efficacy result. A small phase 2 trial of thymosin beta-4 eye drops (RGN-259) in nine patients with severe dry eye reported a 35 percent reduction in ocular discomfort and a 59 percent reduction in corneal fluorescein staining versus vehicle at day 56, with 12 treated eyes against 6 controls (Sosne 2015). That is a very small study, in the eye, with a formulation that is not for sale anywhere, and no marketing authorisation for thymosin beta-4 has followed. There are no published human efficacy trials of the Ac-LKKTETQ fragment sold as TB-500, in any form, by any route.

Adverse findings and limitations

Because the human data are thin, the adverse-event profile is largely unknown. A protein whose job is to promote cell migration and blood vessel formation raises an obvious theoretical question about tumour growth, and no controlled study has resolved it. Short peptides are generally broken down quickly by enzymes; the Hong Kong group first identified likely metabolites of the TB-500 fragment in vitro and then found them in samples from horses given a single administration, and peptides taken by mouth are subject to digestion in the stomach and small intestine before they reach the bloodstream (see the related article on oral peptides). None of this is a claim about any product; it is the state of the literature.

Regulatory status

United Kingdom

TB-500 is not a licensed medicine. The MHRA has never granted a marketing authorisation for it or for thymosin beta-4, and it is not an authorised food supplement or novel food. It can be sold lawfully to adults for laboratory research provided it is not presented for human consumption, which is the basis on which Free Muscle sells it. Anyone who buys it is responsible for using it as a research material. The TB-500 collection page sets this out for each brand stocked.

European Union and United States

The position is the same: no marketing authorisation from the EMA, no approval from the FDA. In the United States, thymosin beta-4 formulations remain investigational, and the FDA has taken a restrictive position on peptides being compounded for patients outside trials.

WADA

Thymosin beta-4 and its derivatives, with TB-500 named as the example, are listed under class S2 (peptide hormones, growth factors, related substances and mimetics) of the WADA Prohibited List. That class is prohibited at all times, in and out of competition, and applies to every sport that follows the World Anti-Doping Code, including UK Anti-Doping testing. Detection methods exist: the Ghent group suggested an analytical strategy for detecting the acetylated fragment in plasma and urine (Esposito 2012), and the Hong Kong laboratory confirmed the parent peptide and its metabolites in horse urine and plasma after a single administration, with a confirmation limit of 0.02 nanograms per millilitre in plasma and 0.01 nanograms per millilitre in urine (Ho 2012). A detection window in humans has not been published, so the accurate statement is that it is detectable and the window is not established.

Common questions

Is TB-500 the same as thymosin beta-4?

Not quite. Thymosin beta-4 is the 43-residue protein. TB-500, as characterised by two independent laboratories, is the acetylated 17 to 23 fragment. Product listings that use the two names interchangeably are using thymosin beta-4 as a shorthand for the fragment it comes from.

TB-500 vs BPC-157

The two are often searched together, but they are unrelated molecules. BPC-157 is a 15-residue sequence derived from a gastric protein and studied mostly by one Croatian group in rodent gut, tendon and ligament models. TB-500 is a fragment of a ubiquitous actin-binding protein studied in wound and cardiac models. Neither is a licensed medicine. Under WADA rules BPC-157 falls under S0 (non-approved substances) while TB-500 falls under S2. The BPC-157 collection and the article on what the BPC-157 research shows cover the other compound.

TB-500 benefits, results, before and after

We do not publish outcome claims for any research compound. What exists in the literature is described above: animal wound and cardiac models, and small early trials of the full protein applied to the skin or the eye. None of it describes what happens to a person who takes a TB-500 capsule, and Free Muscle does not sell TB-500 for that purpose.

TB-500 dosage, dosing protocol, TB-500 and BPC-157 together

We do not publish dosing, cycle or combination guidance for any research compound. The products are sold for laboratory research to adults and are not for human consumption. The quantities used in the studies above were chosen for rats, mice, horses or clinical trial patients under medical supervision and have no application outside those settings.

TB-500 side effects

No systematic human safety data exist for the fragment. The small thymosin beta-4 eye-drop trial reported that the treatment was well tolerated in nine patients, which says nothing about a different molecule taken by a different route. The theoretical concern about promoting growth of existing tumours is unresolved. Anyone with a medical question should ask a doctor, not a research supplier.

TB-500 capsules or tablets in the UK

The brands stocked at Free Muscle are capsule products. A capsule delivers a peptide to the stomach, where proteases begin to break peptide bonds; the published animal work delivered thymosin beta-4 by injection or directly to the tissue. This is a real gap between the research and the product format and the article on whether oral peptides work goes through it honestly.

Is TB-500 legal in the UK?

It is not a controlled drug and it is not a licensed medicine. Selling it as a research chemical to adults, not for human consumption, is generally lawful; presenting it as a medicine or supplement is not. It is prohibited in sport at all times.

How to verify a batch

Because no regulator checks TB-500 products, the only evidence that a capsule contains what the label says is a certificate of analysis for that batch. A useful COA states the batch number that also appears on the pack, the identity test (typically HPLC or LC-MS confirming the expected mass of the peptide), a purity percentage, the quantity per capsule where the laboratory tested it, the laboratory's name and the test date. A generic PDF with no batch number, or a certificate for the raw material rather than the finished capsule, does not tell you what is in the bottle in your hand.

  1. Find the batch number on the pack.
  2. Ask the seller for the COA for that batch. Every Free Muscle-brand batch is assayed by Janoshik Analytical, and the certificate for a batch is sent on request by email.
  3. Check the batch number, the compound name and the test date on the certificate match the pack.
  4. Read the purity figure and the identity method. For a peptide, the identity result should name the expected molecular mass.
  5. For other brands, a COA is shown only where the manufacturer supplies one for the batch held. If there is none, treat the label as unverified.

The articles on reading a certificate of analysis and what Janoshik Analytical is go into the detail, and the lab tests page explains how to request a certificate.

Related reading

TB-500 products are sold by Free Muscle for laboratory research only. TB-500 and thymosin beta-4 are not licensed medicines, have not been evaluated by the MHRA, EMA or FDA, are not food supplements and are not for human consumption. Customers must be 18 or over. Nothing in this article is medical, dosing or usage advice, and the studies described do not support any claim about any product.

References

  1. Goldstein AL, Hannappel E, Kleinman HK. Thymosin beta4: actin-sequestering protein moonlights to repair injured tissues. Trends Mol Med. 2005;11(9):421-429. PMID: 16099219.
  2. Esposito S, Deventer K, Goeman J, et al. 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. Drug Test Anal. 2012;4(9):733-738. PMID: 22962027.
  3. Ho EN, Kwok WH, Lau MY, et al. Doping control analysis of TB-500, a synthetic version of an active region of thymosin beta4, in equine urine and plasma by liquid chromatography-mass spectrometry. J Chromatogr A. 2012;1265:57-69. PMID: 23084823.
  4. Bock-Marquette I, Saxena A, White MD, et al. Thymosin beta4 activates integrin-linked kinase and promotes cardiac cell migration, survival and cardiac repair. Nature. 2004;432(7016):466-472. PMID: 15565145.
  5. Guarnera G, De Rosa A, Camerini R. Thymosin beta-4 and venous ulcers: clinical remarks on a European prospective, randomized study on safety, tolerability, and enhancement on healing. Ann N Y Acad Sci. 2007;1112:407-412. PMID: 17495250.
  6. Sosne G, Dunn SP, Kim C. Thymosin beta4 significantly improves signs and symptoms of severe dry eye in a phase 2 randomized trial. Cornea. 2015;34(5):491-496. PMID: 25826322.