TB-500: what the studies show, status and safety
Summary
TB-500 is a lab-made piece of seven building blocks taken from the human protein thymosin β4. No authority has approved it, and the FDA states that it found no data whatsoever on people taking it. Every published effect comes from animals or from cells in a dish. Almost every clinical trial in this field tested the complete protein of 43 building blocks instead, and the two largest of those trials failed on the questions they set out to answer.
Key findings at a glance
- There are no data from people at all. The FDA states that it found no data on people taking preparations containing this fragment [1]. No genuine trial in people is registered anywhere [2].
- 19 of the 20 registered trials study a different molecule. They test the complete protein thymosin β4. The one entry that names TB-500 describes itself as a made-up example [2].
- Both large late-stage trials of the parent protein failed. One of them enrolled 601 people and the other 700, and neither showed a difference on either of its two main questions [3], [4].
- In rats, 60 µg/kg a day made the treated tendons hold more load. Over four weeks in 32 rats, the force needed to tear the tendon rose by more than chance would explain (p < 0.05). Adding BPC-157 on top brought nothing further [5].
- In the dish, a breakdown product closed wounds, not TB-500 itself. In a 2024 study, only one of the fragments the body cuts the peptide into showed a clear effect [6].
- Most of the samples tested contained no peptide at all. A university racing laboratory reported that most products labelled TB-500 held no proteins, no peptides and no amino acids [7].
- Banned in sport around the clock. Section S2.3 of the 2026 list names "Thymosin-β4 and its derivatives e.g. TB-500", and files it in the stricter of the two categories [8].
What it is
TB-500 is a lab-made peptide of seven building blocks, written as Ac-LKKTETQ. It copies positions 17 to 23 of the human protein thymosin β4 and carries a small chemical cap at the front [9]. It is neither a natural molecule nor a medicine, and its name comes from the veterinary trade and the grey market rather than from any drug company.
What is actually inside the vials sold under that name was worked out by forensic chemistry. In 2012, the doping control laboratory in Ghent identified the capped fragment with high-resolution mass spectrometry and then made it again in the laboratory to compare [10].
The authorities treat the fragment and the complete protein as two different substances. Australia lists them separately in its poisons schedule [11], and the FDA lists the fragment apart from the programmes for the whole protein [1].
Quick facts
| Field | Value | Ref |
|---|---|---|
| Common names | TB-500, TB500, Ac-LKKTETQ | [9] |
| Name used by the authorities | Thymosin beta-4, fragment (LKKTETQ) | [1] |
| Class | Lab-made peptide of seven building blocks, a piece of a human protein | [9], [10] |
| Sequence | Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln | [9] |
| Formula and mass | C38H68N10O14, 889.0 g/mol | [9] |
| The protein it comes from | Thymosin β4, 43 building blocks, about 4.9 kilodaltons | [12] |
| How long it lasts in people | Never published | [6] |
| Status | Not approved in any country, for any species | [1], [11] |
| Who developed it | Nobody; there is no pharmaceutical development history | [1] |
| CAS registry number | 885340-08-9 | [9] |
| UNII | QHK6Z47GTG | [9] |
| PubChem CID | 62707662 | [9] |
How it works
Nothing about how it works has ever been measured in a person, so every point below is a hypothesis carried over from cells and animals [1].
- Gripping the cell scaffold. The stretch LKKTET is the part of thymosin β4 that grips actin, the building material of the cell scaffold, so a peptide carrying it may grip actin too and affect how cells crawl [12]. How firmly it grips depends heavily on what surrounds the stretch, so the piece on its own need not behave like the whole protein [13].
- New blood vessels and repair. Within the complete protein, this region has been linked to the growth of new blood vessels, to wound healing and to cell movement [12].
- A stand-in for the whole protein. In old mice, the uncapped version of the peptide healed skin about as well as the complete protein did [14]. That single comparison from 2003 carries much of the reasoning that came afterwards.
- Possibly a breakdown product does the work. A 2024 study of how the body cuts the peptide up suggests that the wound-healing effect may belong to one of those fragments rather than to the peptide that was given [6].
- Not the part that calms inflammation. The calming effect of thymosin β4 on inflammation is attributed to a completely different piece of the protein, one that TB-500 does not contain [12], [7].
- Not the route described for the heart. The chain of proteins that was said to protect the heart in mice was described for the complete protein, not for this fragment [15].
That split matters. Much of what is claimed for TB-500 is attributed in the original literature to parts of thymosin β4 that this fragment leaves out entirely.
What the trials found
There are no trials of TB-500 in people. What follows is the animal and cell work on the fragment, and after that the human record of the complete protein, which is a different molecule.
ClinicalTrials.gov, searched with nine different terms on 6 September 2026. The single entry naming TB-500 describes itself as a made-up example and is not counted. Source [2].
Tendon
Animal data In 32 rats, the Achilles tendon was cut through and stitched back together, and the animals then received 60 µg/kg a day into the belly for four weeks. The tendons withstood more force before tearing than those of untreated animals, by more than chance would explain (p < 0.05). Two standard scores for tissue quality also improved, the Bonar score (p = 0.016) and the Movin score (p = 0.017). BPC-157 on its own reached neither of those scores, and giving both together added nothing. The authors describe their work as a first exploration [5].
Skin wounds
Animal data In mice aged 26 months, the uncapped peptide of seven building blocks healed skin about as well as the complete protein did [14]. That peptide is not the same molecule as the capped fragment sold as TB-500. For the complete protein in rats, the new skin covering the wound grew 42 percent further along by day 4 and up to 61 percent further by day 7 than with salt water, and the wounds had pulled themselves at least 11 percent tighter by day 7 [16].
Which molecule is active
In vitro A 2024 study followed TB-500 and the fragments it breaks into, in human blood serum, in enzyme mixtures and in rats. One short fragment dominated the first six hours, and another could still be found after 72 hours. In the wound-healing test, only one particular fragment produced a clear effect, and the peptide that had been given produced none [6].
Cornea and brain
Animal data A gel containing TB-500 helped the surface of the cornea grow back faster after a burn with alkali [17]. The peptide was chemically bonded into the gel, so the result says something about that preparation rather than about the loose substance. In mice bred to develop Alzheimer-like changes, peptides derived from thymosin β4 improved performance in maze and recognition tests and calmed the supporting cells of the brain, while the amount of amyloid deposits stayed the same [18].
The parent protein in people
Phase 1 Forty healthy volunteers were given the complete protein into a vein at 42, 140, 420 or 1260 mg, and then the same amount daily for 14 days. Side effects were rare and mild to moderate, and no dose had to be capped because of them [19].
Phase 2 Two trials with 72 patients each tested a gel applied to the skin, and both were designed above all to check safety. By day 84, 8 pressure sores had closed against 3 in the comparison group, and 12 leg ulcers against 4 [20].
A review written by the developers reports healing almost a month sooner, but only among those wounds that closed at all [21]. Neither line of work went on to a late-stage trial.
Phase 3 One late-stage trial tested 0.1% eye drops in a condition where the cornea loses its nerve supply and stops healing. After four weeks the surface had healed completely in 6 of 10 treated eyes against 1 of 8 on dummy drops, a difference that just missed the usual threshold for being more than chance (p = 0.0656). The trial stopped after 18 participants [22].
Endpoints that were missed
One large trial assigned 601 people with dry eyes by chance to treatment or dummy drops, and it failed on both of its two main questions [3]. Its successor did the same with 700 people and also failed on both, with the damage to the lower cornea improving by 0.41 points against 0.46 points on the dummy drops [4].
Both main questions failed. Late-stage trial with 601 participants, using drops of the complete protein and not the TB-500 fragment. Source [3].
An independent Cochrane review looked at that trial and calculated that healing was nine times as likely under treatment (relative risk 9.00), but the range around that figure runs from far below to far above it (0.57 to 141.88), so the evidence counts as weak [23]. A European late-stage trial also failed on its main question according to the trade press [24]. A further trial was still recruiting on 6 September 2026 [25].
What is still unknown
- Everything about people. For the fragment there is no safety study, nothing on how the body handles it, no evidence that it works, not even a series of case reports [1], [2].
- Whether the evidence for the whole protein carries over. Several of the things thymosin β4 does are attributed to parts of it that the fragment does not copy [12], [15].
- Which molecule would actually do the work. The finding about the breakdown products leaves it open which substance is the active one [6].
- Questions about cancer and blood vessels. Something that encourages new vessels and makes cells move raises obvious questions about undetected tumours, and no study has looked at them [12], [26].
- What happens over the long run. For the fragment, no cancer study and no standard set of tests for damage to genetic material has ever been published.
Side effects and safety
There is no list of side effects for TB-500, because nobody has studied it in people. That nothing has been reported is not the same as nothing having happened [1].
- Immune reactions and impurities. The FDA names both as risks for pharmacy-made preparations of the fragment, pointing to possible clumping and to impurities that come with the peptide itself [1].
- No damage to skin cells in one test. Neither the peptide nor its breakdown products killed cells in a single laboratory test [6]. One cell line is not a safety assessment.
- The complete protein was tolerated by 40 people. Up to 1260 mg a day into a vein for 14 days caused nothing that forced the dose down [19]. That is a different molecule, 40 people and two weeks.
- Nobody knows what is in the vial. A university racing laboratory reported that many samples sold under this name contained neither thymosin β4 nor any peptide derived from it. Most held no proteins, peptides or amino acids at all, and only a single sample actually contained the capped fragment [7].
- A second laboratory found the same. In 2023, a French racing laboratory examined products sold as TB500 and TB1000 as wrongly labelled and adulterated medicines, and found that the contents did not reliably match the descriptions [27].
- The reviews all point the same way. A 2026 sports medicine review notes encouraging animal results but scarcely any safety data from people, and the possibility of serious harm [26]. A systematic overview found that 67 percent of the publications are laboratory work, and advises against using the peptide alongside standard orthopaedic care [28].
The gaps are the safety picture. Nothing is known about injecting it repeatedly, about pregnancy, about children, or about people whose liver or kidneys work poorly, because nobody has looked [1].
Doses used in studies
The doses below are simply what the cited studies gave, listed so that the results can be understood. They are not advice on how to use anything. Watch the substance column: only the first four lines concern the fragment sold as TB-500.
| Study | Substance | Model | Dose | Route | Duration | Ref |
|---|---|---|---|---|---|---|
| Biçer 2026, Achilles tendon | The fragment | Rat | 60 µg/kg per day | Into the belly | 4 weeks | [5] |
| Ho 2012, detection method | The fragment | Horse | One dose of a preparation containing 10 mg | Not stated | Once | [29] |
| Philp 2003, skin repair | The fragment, uncapped | Old mouse | Not given in numbers in the abstract | Applied to the wound | Until day 8 | [14] |
| Rahaman 2024, breakdown | The fragment | Rat, and in the dish | Not given in numbers in the abstract | Not stated | Samples taken up to 72 h | [6] |
| Ruff 2010, phase 1 | The complete protein | Human | 42, 140, 420 or 1260 mg | Into a vein | 14 days | [19] |
| SEER-1, cornea without nerve supply | The complete protein | Human | 0.1% solution | Dropped into the eye | 28 days | [22] |
| Ulcer trials, phase 2 | The complete protein | Human | Three rising levels, not given in numbers in the registry | Gel on the skin | Up to 84 days | [20] |
The only published doses for people in this entire field belong to the complete protein [19]. The dosing plans circulating in marketing material have no study behind them, and they are not repeated here.
Development and approval status
How the field developed
- 1999The complete protein speeds up wound healing in ratsNew skin covered 42% more of the wound by day 4, ref [16]
- 2003The short fragment matches the whole protein in old miceThe comparison on which TB-500 rests, ref [14]
- 2004Paper in Nature on heart repair by the complete proteinA chain of signalling proteins in mice, ref [15]
- 2010Different effects traced to different parts of the proteinOne piece calms inflammation, another drives new vessels, ref [12]
- 2012Doping laboratories work out what TB-500 actually containsGhent and Hong Kong, refs [10], [29]
- 2013Racing bulletin reports that most labelled samples hold no peptideThe strictest penalty class recommended, ref [7]
- 2016Sports court bans 34 Australian footballers over thymosin beta-4Not one positive test was involved, ref [30]
- 2018-2021Two large eye trials fail on every main question601 and 700 participants, refs [3], [4]
- 2022A small trial reports 6 of 10 healed against 1 of 8Stopped after 18 participants, and the result just missed significance, p = 0.0656, ref [22]
- 2024Australia lists TB-500 separately from thymosin β4Prescription-only, plus the appendix that bans possession, ref [11]
- 2025-2026The anti-doping lists name TB-500, and Cochrane rates the evidence weakRefs [8], [23]
- 1999 to 2004 — the complete protein produces results in animals, for wounds and for the heart [16], [15].
- 2003 — the fragment of seven building blocks matches it in a single mouse model [14].
- 2012 — doping laboratories establish what the marketed TB-500 actually is [10], [29].
- 2013 — the racing bulletin documents wrongly labelled product and advises the strictest penalty class [7].
- 2018 to 2022 — the three large eye trials of the complete protein come back negative or inconclusive [3], [4], [22].
- 2024 — Australia lists TB-500 by name, separately from thymosin β4 [11].
| Market | Status | Note | Ref |
|---|---|---|---|
| United States | Not approved | Named in the oversight of pharmacy compounding | [1] |
| European Union | Not approved | No marketing authorisation | — |
| Germany | Not approved | Follows the European position | — |
| United Kingdom | Not approved | An unlicensed medicine | — |
| Australia | Restricted | Prescription-only, plus the appendix that bans possession | [11] |
| Canada | Not approved | No drug identification number | — |
| Switzerland | Not approved | No marketing authorisation | — |
Two lines of this table rest on original documents. The American entry comes from the FDA compounding page as it stood on 22 April 2026 [1]. The Australian entry comes from the Poisons Standard in force since 1 June 2026, which carries the entry first made in June 2024 [11].
For the other markets, no authority document could be retrieved on 6 September 2026. Those lines record that no approval exists rather than a checked statement from a register. In Australia the appendix goes further than a prescription requirement: possessing the substance without a permit is unlawful [11].
Anti-doping
TB-500 is banned at all times, both in and out of competition. Section S2.3 of the 2026 Prohibited List names "Thymosin-β4 and its derivatives e.g. TB-500", and the heading of that section states that everything in it counts as non-specified, the stricter of the two categories [8]. That is harsher than the treatment of BPC-157, which sits in another section as a specified substance. The American college sports association names TB-500 as well [31].
Detecting it is not the obstacle it is often made out to be. Methods have existed since 2012, and the peptide is part of the routine screening laboratories run for small peptides, including in dried drops of blood [10], [32].
In horses, the reported detection limits are 0.02 ng/mL in blood plasma and 0.01 ng/mL in urine [29]. The racing body advises testing outside competition, because the peptide can only be found for a short while [7]. The wider picture is at peptides banned in sport.
One case shows that a positive sample is not even needed. In January 2016 the Court of Arbitration for Sport banned 34 Australian footballers over a supplement programme built around thymosin beta-4. Not one of them had ever tested positive [30].
Compared with related peptides
| Peptide | What it is | Human evidence | Status in sport | Strongest result in its own study |
|---|---|---|---|---|
| TB-500 | Lab-made fragment of 7 building blocks | None whatsoever | Banned, S2.3, stricter category [8] | Tendons of 32 rats held more load before tearing [5] |
| Thymosin β4 | Human protein of 43 building blocks | Trials from first to late stage, but no approval | Banned, S2.3, named [8] | 6 of 10 eyes healed against 1 of 8, in only 18 participants [22] |
| BPC-157 | Lab-made sequence of 15 building blocks | A few small and weak observations in people | Banned, S0, milder category [8] | No clear change in the overall score in the same rat study [5] |
| GHK-Cu | A short peptide bound to copper | Used in cosmetics, no approved medicine | Not named on the 2026 list [33] | Assessed as a cosmetic ingredient, not as a trial result [34] |
These four belong together because of how they are marketed, not because of the evidence. Only thymosin β4 has been through controlled trials in people, and its two largest failed on every question they asked [3], [4].
The single study that tested TB-500 and BPC-157 against each other and in combination found no advantage in combining them [5]. GHK-Cu sits in an entirely different regulatory world, as a cosmetic ingredient rather than a drug under investigation [34].
Common misconceptions
- "TB-500 is thymosin beta-4." They are two different substances: 7 building blocks against 43, and 889 g/mol against about 4.9 kilodaltons. Australia and the FDA list them separately [11], [1], [9].
- "The thymosin beta-4 studies are studies of TB-500." Of the 20 registered trials, 19 test the protein itself [2]. The calming effect on inflammation is attributed to a different piece of it, one the fragment does not contain [7], [12].
- "A clinical trial of TB-500 is running." One registry entry names TB-500, and its own summary opens by calling itself a made-up example of a registry entry. Take it away and nothing remains [2].
- "The FDA gave it the green light." The FDA lists the fragment among the substances with identified safety risks and states that it found no data on people taking it. An application that was withdrawn is not an approval [1].
- "What the label says is what is in the vial." Two specialist laboratories on two continents report the opposite, with most samples containing no peptide whatsoever [7], [27].
- "It is legal because it is sold for horses." It is not approved for horses either, and the racing body treats giving it to a horse at all as a prohibited act [7].
Frequently asked questions
Is TB-500 the same as thymosin beta-4?
No. Thymosin beta-4 is a human protein made of 43 building blocks and weighing about 4.9 kilodaltons. TB-500 is a lab-made peptide of seven building blocks weighing 889 g/mol, which copies positions 17 to 23 of that protein and adds a small chemical cap. Australia and the United States list the two as separate substances.
Has TB-500 ever been tested in people?
No. There is no published study in people and no genuine registered trial. The FDA states that it found no data at all on people taking preparations that contain this fragment.
Is TB-500 approved anywhere?
No, in no country and for no species. It is not approved for horses either. The racing industry body states that the FDA has never assessed the peptide for safety or effect in horses, and that products carrying the label are mixed by compounding pharmacies.
Is TB-500 banned in sport?
Yes, at all times, both in and out of competition. Section S2.3 of the 2026 Prohibited List names thymosin-beta-4 and everything derived from it, and gives TB-500 as the example. Every substance in that section counts as non-specified, which is the stricter of the two categories.
Can TB-500 be detected in a doping test?
Yes. Methods for finding it have existed since 2012, and the peptide is part of the routine screening that laboratories run for small peptides, including in dried drops of blood. In horses, the reported detection limits are 0.02 ng/mL in blood plasma and 0.01 ng/mL in urine.
Do the thymosin beta-4 trials apply to TB-500?
Not directly. Of the 20 registered trials in this field, 19 test the complete protein. Several of the effects people quote for TB-500 are attributed in the scientific literature to parts of the protein that this fragment simply does not contain.
Is there a clinical trial of TB-500 running?
No. One entry in the ClinicalTrials.gov registry carries TB-500 in its title, but its own summary opens by stating that it is a made-up example of what a registry entry looks like. It is not evidence that any study exists.
What is in products sold as TB-500?
Often not what the label says. A university laboratory reported that many samples sold under this name contained neither thymosin beta-4 nor any peptide derived from it, and that most contained no proteins, peptides or amino acids whatsoever. A French racing laboratory came to the same conclusion in 2023.
Does combining TB-500 with BPC-157 work better?
No study supports that. The only experiment that tested both substances on their own and then together, a 2026 tendon study in rats, found that the combination brought no extra benefit over either one alone. Nobody has ever examined the combination in people.
Sources
- US Food and Drug Administration. Certain bulk drug substances for use in compounding that may present significant safety risks; entry "Thymosin beta-4, fragment (LKKTETQ), also known as TB-500", listed under bulk drug substances nominated but withdrawn. Content current as of 22 April 2026, retrieved 6 September 2026. https://www.fda.gov/drugs/human-drug-compounding/certain-bulk-drug-substances-use-compounding-may-present-significant-safety-risks
- ClinicalTrials.gov API v2. Registry search on 6 September 2026 using nine term variants, returning 20 distinct studies, of which 19 concern full-length thymosin β4; record NCT07487363 ("TBRIDGE-CV") states in its own brief summary: "This fictional study is an example of a ClinicalTrials.gov-style record." https://clinicaltrials.gov/study/NCT07487363
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- Ho EN, Kwok WH, Lau MY, Wong AS, Wan TS, Lam KK, Schiff PJ, Stewart BD (2012). Doping control analysis of TB-500, a synthetic version of an active region of thymosin β4, in equine urine and plasma by liquid chromatography-mass spectrometry. Journal of Chromatography A 1265:57-69. PMID 23084823. DOI 10.1016/j.chroma.2012.09.043
- Court of Arbitration for Sport decision of 12 January 2016 in the Essendon Football Club matter, banning 34 current and former players over a thymosin beta-4 supplement programme; no player had returned a positive sample. Secondary sources: ABC News, AFL.com.au, Sports Integrity Initiative. https://www.abc.net.au/news/2016-01-12/cas-upholds-wada-appeal-essendon-anti-doping-verdict/7081874
- National Collegiate Athletic Association. 2026-27 NCAA banned substances, class 6, peptide hormones, growth factors, related substances and mimetics. Full text extracted 6 September 2026. https://ncaaorg.s3.amazonaws.com/ssi/substance/2026-27/2026-27NCAA_BannedSubstances.pdf
- Multi-analyte screening methods including TB-500: Drug Testing and Analysis 2016 (PMID 26472487); Journal of Chromatography A 2022 (PMID 35802965); Analyst 2026, dried and liquid blood matrices (PMID 42328738)
- PubChem. Compound CID 139035031, GHK-Cu (copper tripeptide), C14H21CuN6O4, 400.9 g/mol, retrieved 6 September 2026; full-text search of the 2026 Prohibited List returned no entry for GHK or glycyl-histidyl-lysine on 6 September 2026. https://pubchem.ncbi.nlm.nih.gov/compound/139035031
- Pickart L, Margolina A (2018). Regenerative and protective actions of the GHK-Cu peptide in the light of the new gene data. International Journal of Molecular Sciences 19(7):1987. PMID 29986520. DOI 10.3390/ijms19071987
Cite this page
The facts on this page were checked on 6 September 2026. Two entries in the status table rest on original documents from the authorities, and the rest record that nothing was found, which is marked as such.
myPeptides Research & Editing. (2026). TB-500: what the studies show, status and safety. Version 1.0, 6 September 2026. myPeptides Peptide Register. Retrieved from https://mypep.app/peptides/tb-500
How pages in this register are compiled and graded is described under methodology; the full register is at peptides.
| Version | Date | Change |
|---|---|---|
| 1.0 | 2026-09-06 | Initial publication |
Last verified: 6 September 2026. Next review: on publication of any human study of the fragment, on a change in the anti-doping classification, or on a change in the FDA or Poisons Standard entries.