TB-500

TB-500 is a synthetic peptide seven amino acids long. A doping-control laboratory that analysed marketed product identified it as Ac-LKKTETQ: leucine, lysine, lysine, threonine, glutamate, threonine and glutamine, with an acetyl group attached to the leucine at the front [1]. Those seven residues are positions 17 to 23 of thymosin beta-4, a 43 residue protein the body makes throughout its tissues, and the reason anyone assembled them into a separate molecule is that the stretch is the part of the protein that binds actin, the structural filament cells use to hold their shape and to move [2].

What it is sold for is injury: tendon, muscle and ligament recovery, injected. FDA compiled the full marketed claim set from fourteen vendor and clinic websites for its 2026 evaluation, and it runs well past that, through wound healing, angiogenesis, cardiovascular health, hair growth, neurogenesis and immune function [20]. Every one of those claim areas is graded separately below.

Two identity questions decide what any of the published record is evidence for, and this page turns on both. The first is the one the market blurs: thymosin beta-4 has a clinical programme and TB-500 is a fragment of it, so the protein's trials belong to the protein. FDA states the rule in its own footnote, that thymosin beta-4 and TB-500 are not the same substance [20]. The second is finer and it cuts through the fragment's own literature: FDA also holds that the pharmacological profile of the plain heptapeptide LKKTETQ cannot be carried across to the acetylated form that is actually sold [20]. The reference list runs to 29 numbered sources: 19 primary papers and reviews with every identifier transcribed from its PubMed record, five FDA documents read in full with their page counts checked, three registry reads through the ClinicalTrials.gov API, the 2026 Prohibited List read from the primary PDF, and one protein database record. The regulatory section is current to 9 August 2026.

Key takeaways

• TB-500 and thymosin beta-4 are two molecules of very different size, and FDA says so in its own evaluation: several websites use the terms interchangeably, and the agency records that the two are not the same substance.
• No human being has been given TB-500 in any published study, for any purpose, by any route. FDA searched PubMed, Embase, ClinicalTrials.gov, DailyMed, Drugs@FDA and professional-society sources and stated the same finding twice, in two separate documents.
• One registry record names TB-500, and its registered brief summary opens by stating that it is a fictional study and an example of a ClinicalTrials.gov-style record. It has posted no results, and on the registry as read on 9 August 2026 it is the only record naming the compound.
• The whole published record in the tissue TB-500 is sold for is one rat Achilles tendon study with eight animals per group, delivered into the abdominal cavity, whose own authors call it an exploratory rat model study and ask for longer follow-up. [Animal] [4]
• In the one direct laboratory test of the marketed use, TB-500 did not close scratched fibroblast cultures at the concentration tested, while one of its own breakdown products, Ac-LKKTE, did. The paper's authors propose that the wound-healing activity reported in the literature belongs to the metabolite rather than to the parent fragment. [In-vitro] [5] [20]
• FDA draws a second identity line the market does not: because acetylation changes a peptide's charge, water-repellency and size, the agency holds that the profile of the plain heptapeptide LKKTETQ cannot be carried across to the acetylated form sold as TB-500. The 2003 aged-mouse study behind most of the wound-healing reputation used the plain form.
• There is no toxicology package for either form: no acute study, no repeat-dose study, no genotoxicity study, no reproductive and developmental study and no carcinogenicity study was submitted with the nomination or found by FDA.
• FDA lists Thymosin beta-4, fragment (LKKTETQ), also known as TB-500, in the 503A category for substances that may present significant safety risks, citing immunogenicity, aggregation and peptide-related impurities, and stating that it has identified no human exposure data at all.
• TB-500 is named on the face of the 2026 WADA Prohibited List at class S2.3, by its own name, as the example given in the thymosin beta-4 entry. That class is prohibited in and out of competition, and every substance in it is a non-Specified Substance, which is the harsher of the two sanctioning categories.

Who researches TB-500?

Three groups arrive at this compound, and the published record answers them very differently.

The largest is reading about a tendon, a muscle or a ligament, usually after an injury that is healing slowly. That interest is what the product is built around, and the entire published record in those tissues is one rat study of a surgically cut Achilles tendon with eight animals in the treated group. There is no registered trial of either molecule in tendon, muscle or ligament, which is a short sentence covering a wide gap.

The second group arrives having already read a trial count. Search engines and vendor pages attach the thymosin beta-4 registrations to the fragment, so a reader can reach a page listing a phase 3 programme with the right-sounding name on it. Those registrations exist and they were run in eyes and in skin. The human-record section below lists all of them with what each one tested, so the count can be checked rather than repeated.

The third group is a tested athlete, or somebody advising one. That question has the clearest answer on this page and it does not depend on the evidence at all: the compound is named on the Prohibited List by its own name, and the anti-doping section sets out the class, the sanctioning category and what has been published about detection.

• TB-500 against thymosin beta-4: the fragment and the protein it was cut from
• The 503A Bulks List and the July 2026 advisory committee

What is TB-500?

Plain-English version: a chain of seven amino acids copied out of the middle of a much larger protein, with a chemical cap added to one end that the protein does not carry there.

Thymosin beta-4 is a small protein. The reference record for accession P62328 carries a 44 residue precursor whose annotated mature chain runs from residue 2 to residue 44, giving the 43 residue protein with the sequence SDKPDMAEIEKFDKSKLKKTETQEKNPLPSKETIEQEKQAGES [29]. Counting from that first serine, residues 17 to 23 read LKKTETQ, and a 2010 review from the group that characterised the protein describes that stretch plus its terminal glutamine as the central actin-binding domain [2].

TB-500 is those seven residues with a synthetic acetyl group on the leucine at the front: Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln. FDA gives it the UNII code QHK6Z47GTG, the CAS number 885340-08-9, the formula C38H68N10O14 and a molecular weight of 889.01, and treats the acetate salt as a separate bulk drug substance with no identifier of its own [20]. Two independent laboratories established the identity from marketed product rather than from a supplier's claim: a 2012 doping-control paper isolated the compound from a product sold under the name, characterised it by high-resolution mass spectrometry, and then synthesised it separately to confirm the match [1], and a second 2012 paper analysing a veterinary preparation reported the same, LKKTETQ with an artificial acetyl group at the N-terminus [6].

That acetyl group is small and it is not cosmetic. FDA's evaluation quotes the reason directly: acetylation permanently alters a peptide's charge, its water-repellency and its size, which can change how long it lasts, how it folds and what it binds to [20]. The agency's conclusion from that is the one this page carries throughout, that a result obtained with the plain heptapeptide does not transfer to the acetylated one.

A third identity question applies to the container rather than to the chemistry. A 2023 analysis of products sold online under these names reports that their content is not consistently what the descriptions say it is [9], and FDA reaches the same place from the paperwork side: TB-500 is a common name rather than a USAN, INN or IUPAC name, and the agency records having encountered multiple salts and derivatives, including different active moieties, sold commercially under it [20].

Ac-LKKTETQ · C38H68N10O14, 889.01 g/mol for the free base

How strong is the evidence, claim by claim?

Every claim area this compound is discussed for gets a row, including the ones with the weakest support. The tier records what the row rests on, and the last column states what that work can and cannot show. Each tier links to its definition on the methodology page.

Rolled up, that puts TB-500 at evidence grade D Animals and anecdote . No completed human study of this compound for any use. The claim set is animal, in-vitro, and anecdote. A grade describes the quality of the research, not whether something works and not whether anyone should use it. The derivation is published.

How TB-500 is thought to work

Mechanism writing about this compound almost always describes the parent protein and then attaches the description to the fragment. The four blocks below separate what was measured on which molecule, in strength order, and the last two are the ones specific to TB-500 itself.

What we do not know

Whether the acetylated fragment does anything the plain one does is unmeasured. No published experiment puts Ac-LKKTETQ and LKKTETQ side by side in the same system, and FDA's stated position is that the two cannot be assumed to behave alike [20].

No molecular target of TB-500 itself has been identified. Actin binding is attributed to the sequence within the parent protein [2], and no published work has measured the acetylated peptide binding anything.

How much of an administered amount becomes Ac-LKKTE, the one breakdown product with a measured activity, is unknown in every species. The 2024 study identifies the metabolite and quantifies its appearance in rats but does not connect that to the activity it measured in a dish [5].

No rodent or equine number converts into a human one, because the human measurement that would anchor it has never been made [20].

Whether the compound reaches an injured tendon in any species is unmeasured. The one exposure study is in horses and measured blood [6]; no published work has measured concentrations in tendon, muscle or ligament tissue after administration.

Has TB-500 been tested in humans?

No published study has given TB-500 to a person. The table sets out every human-facing record that a search for this compound returns, which molecule each one tested, and what it found.

The first two rows are the registry record naming TB-500 and the sponsor account it belongs to, read in full through the ClinicalTrials.gov API on 9 August 2026. The rows after them are the parent protein's trials, labelled as the parent's, because those are what the trial counts published for this compound are actually counting. The last two rows record a study of a third molecule and the limits on this page's own sourcing.

Why we are not calling this proof

The absence at the centre of this page is unusual enough to be worth stating precisely, because it is stronger than the usual version of it. The common situation in this category is a compound with no human trial. This compound has no human trial and no registration that is not a self-declared example, which means there is not even a date on which the position might change.

The parent protein's record is the thing most often substituted for it, and read whole that record is weaker than its citation count suggests. Three phase 3 dry-eye trials totalling 1,618 participants have completed and none of them has been published. The one that posted results moved in the worse direction on both primary endpoints. A reader who arrives having been told that thymosin beta-4 has phase 3 evidence has been told something true about the number of trials and misleading about their outcome.

The FTC sets the substantiation bar for a health claim at randomized controlled human trials, and says animal work, laboratory work and observational data are generally not enough on their own. TB-500 has none of the first and, in the one direct laboratory test of its marketed use, the compound itself did not separate from control.

What would change this page is narrow and specific: a trial that gives TB-500 to people, or a study that puts the acetylated fragment and the plain heptapeptide side by side in the same system. Neither is registered, and the one document that looked like the first says of itself that it is an example.

Benefits: what the research shows

Each heading below is a claim made for TB-500, not a finding. Under each one is what was measured, in what, and which molecule was in the experiment.

The claim inventory itself comes from FDA, which compiled it from fourteen vendor and clinic sites for its 2026 evaluation and published the list [20]. Using the agency's inventory rather than a hand-picked one is deliberate: it means no claim was dropped for being weak.

The honest bottom line on benefits

Read as a whole, the file has an unusual shape. Most compounds in this category have thin evidence pointing the way the seller wants. This one has thin evidence pointing two ways at once: a positive rat tendon result in the marketed tissue, and a negative direct test of the marketed use in the simplest system anyone could have used.

The great majority of published work naming TB-500 is analytical chemistry written to detect it, and that is a finding about the field rather than an accident of searching. Doping-control laboratories characterised the molecule, mapped its breakdown products, and built the methods to find it in blood and urine. Nobody built a comparable programme to find out what it does.

The parent protein's record cannot be borrowed and, on a full reading, would not help much if it could. Its three completed phase 3 dry-eye trials are unpublished and the one with posted results did not move its endpoints in the right direction.

What anyone does with that is a judgement rather than a fact, and it belongs to the reader. This site reports what has been documented. It does not prescribe what should be done.

How long TB-500 stays in the body

Two questions sit under this heading and each is answered in one species only. How long an administered amount lasts was measured once, in horses, and the figures are in the benefits section above [6]. What it turns into was mapped in rats and across five laboratory systems, and the products are listed in the mechanism section [5] [10].

What neither answers is the question a reader is actually asking. Every figure this compound has belongs to an animal given it by a route nobody uses, and body-weight scaling between species is unreliable even between two mammals dosed the same way. There is no conversion factor to apply and nothing to apply one to.

So any half-life, clearance or bioavailability figure in circulation for TB-500 came from somewhere other than a measurement of it in a human being: an animal experiment carried across without a stated basis, a figure for the parent protein, or nothing at all.

No half-life, clearance or bioavailability figure has been published for TB-500 in a person on any route, and the only in-vivo exposure measurement in any species was made in horses by a laboratory whose purpose was detection. [Animal] [5] [6] [10] [20]

What is documented about dosing

No study has established an amount of TB-500 for a person, so there is no dosing section on this site in the sense other properties use the phrase. What can be reported is which molecule each published study gave, in which species and by which route, and what kind of figures circulate elsewhere.

Commonly cited protocols (extrapolated, not validated)

Nothing here is a dosing recommendation. Statements about dosing reflect community and research reports only.

Two features of that table decide how much any of it is worth. The first is the route. Every in-vivo figure for the acetylated fragment comes from the abdominal cavity of a rodent or from under the skin of a horse, and neither maps onto anything a person would do. Scaling an amount between species is unreliable even between two mammals given the same way, and none of these was.

The second is which molecule each row describes. Three of the eight rows are not TB-500 at all: one is the plain heptapeptide, one is a breakdown product, and one is a nomination document rather than an experiment. Reading the table as a single set of amounts for one substance is the error the whole page exists to prevent.

Main routes people compare, and what each source class actually reported, are set out on the documented protocols page.

Reported effects and what has been measured

What FDA's adverse event searches returned, and what the searches can support

FDA's Office of Surveillance and Epidemiology searched the FAERS database for reports naming TB-500 through 26 March 2025 and retrieved none, and the agency's literature search identified no cases either. That sentence has to travel with FDA's own footnote, which the agency attaches to it: reporting to FAERS is voluntary, there is no certainty that a reported event was caused by the suspect product, FDA does not receive all reports that may occur, especially for compounded products, and considering those limits the agency cannot draw definitive conclusions about the safety of TB-500.

Two further records exist and they are usually left out. A search of FDA's Human Foods Complaint System covering 1 January 2004 to 10 March 2025 retrieved two cases about a blended TB-500 and BPC-157 product, and those reports carry no safety assessment. And in the BPC-157 section of the same advisory committee presentation, one of three FAERS reports records a 40-year-old woman who used BPC-157 and TB500 and had diffuse hyperpigmentation and gingival darkening that returned when she used the products again.

So the accurate statement is narrower than the headline. FAERS holds no report naming TB-500 as the suspect product; two complaint reports naming a blend exist in a different FDA system without safety assessments; and a report filed against a different compound records concomitant TB-500 use with a finding that recurred on re-exposure.

What the toxicology record contains

The toxicology record for this compound is empty, and empty in a specific and checkable way. FDA's evaluation records that the nominator did not submit, and the agency did not identify, nonclinical toxicity studies of TB-500 free base or TB-500 acetate. That covers acute toxicity, repeat-dose toxicity, genotoxicity, developmental and reproductive toxicity, and carcinogenicity.

None of the animal studies on this page was designed to measure harm. The rat tendon study measured tendon healing, the rat metabolism study measured concentrations, and the equine study measured detection windows. An observation made in passing inside an experiment built for something else is not a toxicology result.

Long-term exposure has been characterised in no species. The longest administration in any published experiment with this compound is four weeks, in eight rats.

Immunogenicity, which is the risk FDA names

The one hazard FDA identifies specifically is immunogenicity, meaning the possibility that an immune system reacts to the injected material. The agency's language in the briefing document is that peptides given by injectable routes may pose a significant risk for immunogenicity, potentially amplified by aggregation and by potential peptide-related impurities, and that the nomination did not include and FDA has not identified information suggesting these substances do not present such risks.

Aggregation is worth a plain-language line, because it is the mechanism behind the concern. Peptide molecules can clump together into larger particles, and an immune system is more likely to react to a clump than to a single small molecule. Impurities left over from synthesis can do the same. FDA raises both as unassessed possibilities rather than as things measured in this compound.

Two precisions belong beside that. A risk the agency calls potential is one it has not ruled out rather than a harm it has documented. And the concern is carried on a second FDA record as well, the 503A category 2 listing set out in the regulatory table below, which adds that no human exposure data for products containing the fragment has been identified at all.

What has not been characterised, and what is in the vial

FDA concludes that both the free base and the acetate are not physically and chemically well characterized, and gives its reasons: naming outside the INN, USAN and IUPAC standards, and no public data on impurities, aggregates, microbial bioburden or bacterial endotoxin. Neither form has a USP or NF monograph, and neither is a component of any approved drug product.

The nomination package itself illustrated the problem. FDA itemises four internal inconsistencies in it: the nominated substance is the free base while the accompanying certificate of analysis is for the acetate, the certificate's CAS number, formula and molecular weight are the acetate's, the formula in the package matches neither substance, and an additional CAS number given in the package matches neither either.

The container is a separate question from the paperwork, and the opening section sets out the one published measurement of what is actually in products sold under this name [9] [20]. What follows for safety is that an impurity profile cannot be described for a substance whose composition is described more than one way, which is the gap FDA names when it raises aggregates and peptide-related impurities. [In-vitro] [9] [20]

Talk to a licensed clinician about anything concerning your health.

Sourcing and quality

What a credible product should show

A certificate of analysis is the document that matters, and for this compound it has to answer a question that does not arise for most: which of the substances sold under this name is in the container. The free base and the acetate are separate bulk drug substances with separate identifiers, FDA records suppliers reusing the free base's CAS number for the acetate, and the agency states it has encountered multiple salts and derivatives under the one common name.

Three things make any certificate checkable: a lot number that matches the container in front of you, a test date, and the name of the laboratory that ran the test rather than the name of the company selling the material.

What the common tests establish is narrower than it looks. High performance liquid chromatography separates what is in a sample and reports relative peak area, which is a statement about chromatographic purity rather than about identity. Mass spectrometry addresses identity by measuring molecular weight, and for the free base that should land at 889.01. Neither test says how much material is in the container, which is net peptide content and is reported separately if at all, and neither addresses whether the acetyl group is present, which is the single feature separating this molecule from the plain heptapeptide.

Red flags

A certificate with no lot number cannot be tied to the container in your hand, whatever else it says. A certificate reproduced from a supplier without an independent test is a supplier's claim rather than a verification. A certificate dated well before the material was made covers a different batch.

A purity figure with no method named is not a purity figure. Ninety-nine percent by which measurement, against which reference standard, and with how much material in the container are separate questions, and one percentage answers none of them.

A document naming only TB-500 has not identified the substance, because the name covers at least two, and FDA's evaluation records the nomination package itself getting that distinction wrong in four separate places.

Widely circulated statistics about what fraction of products in this market are underdosed, or what fraction of certificates are fabricated, trace back to affiliate content sites rather than to a published testing programme. This site does not publish them, because nobody has traced them to primary data.

This site names no company adversely and names none favourably either. There is no best-vendor list here, no rating and no top pick, and there will not be one.

Will it show on a drug test?

This is the clearest question on the page. TB-500 is named on the face of the 2026 WADA Prohibited List, by its own name. Class S2, peptide hormones, growth factors, related substances and mimetics, is prohibited at all times, in and out of competition, and within it S2.3 covers growth factors and growth factor modulators. The entry reads Thymosin-ß4 and its derivatives e.g. TB-500, so the compound appears as the worked example of its own class entry [28]. FDA states the same class independently in its presentation to the advisory committee.

One property of that class is a sanctioning fact and is easy to miss. The class heading states that all prohibited substances in it are non-Specified Substances, which is the category that carries the harsher default sanction and a narrower route to reduction. Compounds reached only by the S0 catch-all, which is where most unapproved peptides sit, are Specified Substances. This one is not.

Detectability is established rather than theoretical, and the reason is chemical. The parent protein is endogenous, so a test for it would have to separate an administered amount from what a body already carries. Ac-LKKTETQ is synthetic and the acetyl group it carries is not something the body puts there, so there is no natural background to separate it from. A 2012 doping-control study detected the compound in equine plasma at 0.02 nanograms per millilitre and in equine urine at 0.01 [6], and the analytical literature on this compound is substantially larger than its pharmacology literature, including work mapping its breakdown products specifically so screening methods can look for those too [5] [10].

Anti-doping status is decided by an athlete's own anti-doping organization against the current list, and that is the only body whose answer counts. Workplace testing is a different system with a different panel and publishes no position on this compound.

Storage

No stability or shelf-life study of TB-500 has been published, in any presentation. No degradation product formed during storage has been characterised, and no published work describes what happens to the material in a container over time or under handling.

The gap is worth naming precisely for this molecule, because the one structural feature that defines it is a chemical group attached to one end. A measurement establishing that the peptide is intact is not a measurement establishing that the acetyl group is still where it should be, and nothing published addresses the second question.

This site publishes no handling or preparation procedure. That is a standing rule and the reasoning is on the editorial policy page.

Regulatory status, as of 9 August 2026

The regulatory file on TB-500 is better documented than most in this category, and the reason is the July 2026 advisory committee: FDA published its own written evaluation of the compound before the meeting, so the agency's reasoning is on the record rather than inferred from an outcome. Two separate FDA records are live at once, and they answer different questions.

Start with what the July meeting did and did not do, because it is the most misreported event in this file. The Pharmacy Compounding Advisory Committee considered whether certain bulk drug substances should be added to the 503A Bulks List, which is the list of substances a pharmacy may lawfully compound with when there is no approved product to use. TB-500 was taken up in the afternoon session of 23 July 2026 on two voting questions, one for the free base and one for the acetate. A committee recommendation is advisory: the agency still has to decide, publish a proposed rule, take comment and issue a final rule, and none of that has happened. Nothing about the legal position of this compound changed on that date. The 503A Bulks List record on this site sets out the meeting, the seven substances, and what a listing would and would not mean.

No vote tally is published here, and the reason is that no primary document carries one. FDA posted eight briefing documents, the webcast information, the voting questions, the final agenda, the final roster and two presentation decks for that meeting, and no minutes and no transcript. Secondary coverage reports a figure for TB-500 and no primary source supports it. What would settle it is the committee minutes, which FDA posts to the meeting page and to the public docket, or the preamble of any proposed rule the agency issues on the list.

The category 2 listing is a separate record from the Bulks List question and it is the one most often missed. FDA maintains a list of nominated bulk drug substances that may present significant safety risks, and Thymosin beta-4, fragment (LKKTETQ), also known as TB-500, is on it, with the agency's immunogenicity rationale published beside it. FDA has also said it does not intend to place substances nominated on or after 7 January 2025 into these categories, so how that listing interacts with the July 2026 recommendation is a question of regulatory process this page does not attempt to resolve. Both records exist and both are stated here.

The evaluation reached two conclusions and the human-record table above carries the first of them in the agency's own words. The second is about safety rather than effectiveness: FDA records a lack of clinical and nonclinical safety information, and describes itself as particularly concerned about the absence of human data on products containing these substances by any route. Both are conclusions about the record rather than findings about the molecule, which is the distinction the agency is careful with and most writing about this compound is not.

The anti-doping position is the one part of this file that is settled and immediate. TB-500 appears on the face of the 2026 Prohibited List as the named example in the thymosin beta-4 entry at S2.3, prohibited at all times, and every substance in that class is non-Specified. That position was read back from the final English document rather than from any summary of it. An athlete's own anti-doping organization is the body whose reading counts.

TB-500 compared with other peptides sold for injury recovery

Two of the four rows carry a grade and two do not, for different reasons. BPC-157 has no grade because the source review behind one has not been run on this site. Thymosin beta-4 has none because it is a parent molecule this site reports on rather than a compound in the catalogue.

The comparison worth understanding is between this compound and GHK-Cu, because it shows what the letters do and do not measure. GHK-Cu sits at B and TB-500 sits at D, and B is the higher letter. It belongs to the compound that was tested twice in people and did not separate from its control, while D belongs to the compound nobody has tested at all. The letter records how much research exists and how good it is, never which way it came out, which is why the sentence beside each badge carries the direction in words.

The relationship to the parent protein is the one that changes the reading of every trial count published for this compound, and it has its own page.

What TB-500 typically costs

TB-500 is sold as a lyophilised powder in vials, in a market where the name covers at least two substances and where the certificate rather than the label is the only thing that says which one is in the container. What any of it costs is not published here, and the cost page sets out why, along with the four things that actually move a listing.

The point worth carrying away is that nothing in a price says anything about identity, content or testing, and for this compound that includes whether the material is the free base or the acetate. Those are certificate questions, and they are covered in the sourcing section above.

See the price comparison.

Frequently asked questions

References

1. Esposito S, Deventer K, Goeman J, Van der Eycken J, Van Eenoo P. 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. PMID 22962027 DOI 10.1002/dta.1402
2. Sosne G, Qiu P, Goldstein AL, Wheater M. Biological activities of thymosin beta4 defined by active sites in short peptide sequences. FASEB J. 2010. PMID 20179146 DOI 10.1096/fj.09-142307
3. Philp D, Badamchian M, Scheremeta B, Nguyen M, Goldstein AL, Kleinman HK. Thymosin beta 4 and a synthetic peptide containing its actin-binding domain promote dermal wound repair in db/db diabetic mice and in aged mice. Wound Repair Regen. 2003. PMID 12581423 DOI 10.1046/j.1524-475x.2003.11105.x The peptide arm used the non-acetylated heptapeptide LKKTETQ, which is not the molecule sold as TB-500
4. Biçer O, Adanir O, Güleryüz Y, Balci EC, Dinçel YM, Yenigün MY, Aydin C, Bayrak BY. Effects of BPC-157 and TB-500 on Achilles tendon healing in rats: A histopathological and biomechanical study. Jt Dis Relat Surg. 2026. PMID 42542926 DOI 10.52312/jdrs.2026.2951
5. Rahaman KA, Muresan AR, Min H, Son J, Han HS, Kang MJ, Kwon OS. Simultaneous quantification of TB-500 and its metabolites in in-vitro experiments and rats by UHPLC-Q-Exactive orbitrap MS/MS and their screening by wound healing activities in-vitro. J Chromatogr B Analyt Technol Biomed Life Sci. 2024. PMID 38382158 DOI 10.1016/j.jchromb.2024.124033
6. Ho EN, Kwok WH, Lau MY, Wong AS, Wan TS, Lam KK, Schiff PJ, Stewart BD. 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. J Chromatogr A. 2012. PMID 23084823 DOI 10.1016/j.chroma.2012.09.043
7. Lu P, Shan M, Peng C, Ji W, Yang T, Yang Z, Zhang Z, Wang Y. Alkaline Phosphatase-Triggered Spatiotemporal Repair of Corneal Injury with TB500 Peptide Hydrogel. ACS Appl Mater Interfaces. 2025. PMID 41359360 DOI 10.1021/acsami.5c14652 Administered as a covalent peptide conjugate that self-assembles into a gel, not as free TB-500
8. Ou H, Chen R, Zhou L, Zhang Y, Zhao S, Yang Z. Thymosin β4-derived peptides alleviate neuroinflammation and neurite atrophy in both in vitro models and in vivo 5 × FAD mice: A potential therapy for memory improvement in Alzheimer's disease. Int Immunopharmacol. 2026. PMID 41443105 DOI 10.1016/j.intimp.2025.116097 TB500 is reported together with Ac-SDKP throughout; no arm isolates either peptide
9. Delcourt V, Garcia P, Chabot B, Barnabé A, Bouscarel M, Loup B, Popot MA, Bailly-Chouriberry L. TB500/TB1000 and SGF1000: A scientific approach for a better understanding of misbranded and adulterated drugs. Drug Test Anal. 2023. PMID 36482504 DOI 10.1002/dta.3421
10. Zvereva I, Semenistaya E, Krotov G, Rodchenkov G. Comparison of various in vitro model systems of the metabolism of synthetic doping peptides: Proteolytic enzymes, human blood serum, liver and kidney microsomes and liver S9 fraction. J Proteomics. 2016. PMID 27569051 DOI 10.1016/j.jprot.2016.08.016
11. Sosne G, Dunn SP, Kim C. Thymosin β4 significantly improves signs and symptoms of severe dry eye in a phase 2 randomized trial. Cornea. 2015. PMID 25826322 DOI 10.1097/ICO.0000000000000379 A trial of thymosin beta-4, the parent protein, not of TB-500
12. Sosne G, Ousler GW. Thymosin beta 4 ophthalmic solution for dry eye: a randomized, placebo-controlled, Phase II clinical trial conducted using the controlled adverse environment (CAE™) model. Clin Ophthalmol. 2015. PMID 26056426 DOI 10.2147/OPTH.S80954 A trial of thymosin beta-4, the parent protein, not of TB-500
13. Sosne G, Kleinman HK, Springs C, Gross RH, Sung J, Kang S. 0.1% RGN-259 (Thymosin ß4) Ophthalmic Solution Promotes Healing and Improves Comfort in Neurotrophic Keratopathy Patients in a Randomized, Placebo-Controlled, Double-Masked Phase III Clinical Trial. Int J Mol Sci. 2022. PMID 36613994 DOI 10.3390/ijms24010554 A trial of thymosin beta-4, the parent protein, not of TB-500
14. Sosne G. Thymosin beta 4 and the eye: the journey from bench to bedside. Expert Opin Biol Ther. 2018. PMID 30063853 DOI 10.1080/14712598.2018.1486818 Indexed by PubMed as a review and a personal narrative, not as a study
15. Shah R, Reyes-Gordillo K, Rojkind M. Thymosin β4 inhibits PDGF-BB induced activation, proliferation, and migration of human hepatic stellate cells via its actin-binding domain. Expert Opin Biol Ther. 2018. PMID 30063851 DOI 10.1080/14712598.2018.1478961 Cell work on the parent protein. One of the three references submitted with the nomination
16. Nguyen J, Verma S, Vuong VT, Queener H, Coulson-Thomas VJ, Gesteira TF. Engineered Tandem Thymosin Peptide Promotes Corneal Wound Healing. Invest Ophthalmol Vis Sci. 2025. PMID 41235866 DOI 10.1167/iovs.66.14.31 An engineered dual-domain molecule, distinct from both TB-500 and the parent protein
17. Mendias CL, Awan TM. Safety and Efficacy of Approved and Unapproved Peptide Therapies for Musculoskeletal Injuries and Athletic Performance. Sports Med. 2026. PMID 41966639 DOI 10.1007/s40279-026-02437-0
18. Mayfield CK, Bolia IK, Feingold CL, Lin EH, Liu JN, Rick Hatch GF, Gamradt SC, Weber AE. Injectable Peptide Therapy: A Primer for Orthopaedic and Sports Medicine Physicians. Am J Sports Med. 2026. PMID 41476424 DOI 10.1177/03635465251357593
19. Rahman OF, Lee SJ, Seeds WA. Therapeutic Peptides in Orthopaedics: Applications, Challenges, and Future Directions. J Am Acad Orthop Surg Glob Res Rev. 2026. PMID 41490200 DOI 10.5435/JAAOSGlobal-D-25-00236
20. US Food and Drug Administration. TB-500 (free base) and TB-500 acetate. Briefing document for the Pharmacy Compounding Advisory Committee, dated 15 May 2026, 41 pages, downloaded with a browser user agent and read in full on 9 August 2026 with the page count checked against the file. Carries the identity data, the nomination history, the marketed-claims inventory, the acetylation caveat, the FAERS and complaint-system searches, and the agency's proposal against adding either form to the 503A Bulks List. FDA advisory committee materials. 2026. Briefing document
21. US Food and Drug Administration. July 23, 2026 Meeting of the Pharmacy Compounding Advisory Committee: FDA Presentations. 149 pages, page count checked against the file, read on 9 August 2026. The TB-500 evaluation runs from deck page 89 to deck page 118. Numbering inside that section restarts, so its slide 19 is deck page 107 and carries the effectiveness conclusion, its slide 21 is deck page 109 and carries the adverse event search with its footnote, and its slide 26 carries the WADA class. The companion deck for 24 July contains no TB-500 content. FDA advisory committee materials. 2026. FDA presentations
22. US Food and Drug Administration. Questions for PCAC regarding whether FDA should include certain bulk drug substances on the 503A Bulks List, Pharmacy Compounding Advisory Committee, 23 and 24 July 2026. 2 pages, read in full. Item 3 of the 23 July afternoon session is TB-500-related bulk drug substances, on two voting questions covering the free base and the acetate. FDA advisory committee materials. 2026. Voting questions
23. Office of the Federal Register. Pharmacy Compounding Advisory Committee; Notice of Meeting; Establishment of a Public Docket; Request for Comments. Bulk Drug Substances Nominated for Inclusion on the Section 503A Bulk Drug Substances List. Document 2026-07361, published 16 April 2026, Docket No. FDA-2025-N-6895. Its chart of evaluated uses records wound healing for TB-500 free base and TB-500 acetate. Federal Register. 2026. Notice of meeting
24. US Food and Drug Administration. Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks. The category 2 table carries the row Thymosin beta-4, fragment (LKKTETQ), also known as TB-500, with the immunogenicity and aggregation rationale and the statement that FDA has not identified any human exposure data for drug products containing the fragment. Page content current 22 April 2026, read 9 August 2026. FDA human drug compounding. 2026. Category 2 record
25. Hudson Biotech. A Phase 1/2, Randomized, Double-Blind, Placebo-Controlled, Sequential Dose-Escalation Study of TB-500 (Thymosin Beta 4 17-23 Fragment) in Adults With Stable Atherosclerotic Cardiovascular Disease. Registry record read in full through the ClinicalTrials.gov API v2 on 9 August 2026: recruiting, actual start 5 February 2026, first posted 23 March 2026, 80 participants estimated, no results posted. Its registered brief summary begins: this fictional study is an example of a ClinicalTrials.gov-style record. ClinicalTrials.gov, NCT07487363. 2026. Registry record
26. US National Library of Medicine, ClinicalTrials.gov. Registry searches run through API v2 on 9 August 2026. A term search for thymosin beta 4 returned 18 records, of which 17 registered the parent protein or a recombinant version of it, across dry eye, neurotrophic keratopathy, venous stasis ulcers, pressure ulcers, epidermolysis bullosa, corneal wounds in diabetes and acute myocardial infarction, and none in tendon, muscle or ligament. A sponsor search for Hudson Biotech returned 8 records, all recruiting, all first posted between 27 February and 1 April 2026, all single-site at Peking University Shenzhen Hospital, three of which state in their own registered text that they are example records. ClinicalTrials.gov. 2026. Registry searches
27. ReGenTree, LLC. Assessment of the Safety and Efficacy of RGN-259 Ophthalmic Solutions in Dry Eye (ARISE-2). Registry record with posted results, read through the ClinicalTrials.gov API v2 on 9 August 2026: phase 3, 601 participants actual, completed March 2018. Both primary endpoints are change from baseline at day 29 on scales where a higher score is worse; ocular discomfort moved plus 0.07 against minus 0.04 on placebo and corneal fluorescein staining plus 0.07 against minus 0.01. No statistical test is posted alongside them. ClinicalTrials.gov, NCT02974907. 2018. Posted results
28. World Anti-Doping Agency. The 2026 Prohibited List, World Anti-Doping Code International Standard, effective 1 January 2026. Class S2, peptide hormones, growth factors, related substances and mimetics, is prohibited at all times and its heading states that all prohibited substances in the class are non-Specified Substances. On page 8, class S2.3, growth factors and growth factor modulators, carries the entry Thymosin-ß4 and its derivatives e.g. TB-500. Read back from the final English document, 26 pages, retained off-site: the address below serves a zero-byte response to automated requests and is recorded as such in this repository's source ledger. WADA. 2026. Prohibited List
29. National Center for Biotechnology Information. TYB4_HUMAN, Thymosin beta-4, accession P62328. Protein record read on 9 August 2026: a 44 residue precursor, MSDKPDMAEIEKFDKSKLKKTETQEKNPLPSKETIEQEKQAGES, whose annotated mature chain runs residues 2 to 44 and gives the 43 residue protein. Counting from the first serine of that mature chain, residues 17 to 23 are LKKTETQ. NCBI Protein. 2026. Protein record