TB-500 Dosage Guide: Thymosin Beta-4 Fragment, Evidence & Reconstitution

TB-500 at a glance

What it is

A synthetic acetylated 7-amino-acid peptide, Ac-LKKTETQ - residues 17 to 23 of Thymosin Beta-4 plus the adjacent glutamine. It is a fragment of that 43-amino-acid protein, not the protein itself, and the distinction runs through everything else on this page.

Human trials of the fragment

None located. A registry entry previously cited here as the first such trial, NCT07487363, describes itself in its own brief summary as a fictional example record; that citation was withdrawn on 2026-08-26. Every controlled human study in this area used full-length Thymosin Beta-4, not the 17-23 fragment.

Where the evidence actually comes from

Full-length Thymosin Beta-4, not TB-500. That includes three completed dry-eye trials of the ophthalmic formulation RGN-259 enrolling 317, 601 and 700 patients, and recombinant Tb4 (NL005) in Phase 2 for acute myocardial infarction. None of them administered the 7-mer.

Does the fragment do what the protein does?

Not established. LKKTETQ is documented as the central actin-binding domain and is associated with angiogenesis, wound healing and cell migration, but the literature does not demonstrate that the isolated 7-mer reproduces the full protein's activity, and Thymosin Beta-4 has several active regions rather than one.

Commonly reported range

Roughly 2-5 mg per administration during a reported loading phase, then a lower weekly figure. These are community-reported numbers with no human dose-finding study behind them - the trial above is the first study that will produce real dose data.

Route reported

Subcutaneous or intramuscular injection. Reported as injectable only; not oral or nasal.

Half-life

No published human half-life exists for the fragment. Figures of roughly 2-3 hours circulating online belong to the parent protein, and the new trial's pharmacokinetic objective is precisely because this number is missing.

Regulatory status

Not FDA-approved in any form. On the WADA Prohibited List under class S2, banned in and out of competition since 1 January 2012. Supplied for research and educational use only.

Reported ranges from research/community — examples, not recommendations.

What it is / mechanism

TB-500 is a seven-residue peptide with a very specific provenance: acetyl-LKKTETQ, corresponding to amino acids 17 through 23 of Thymosin Beta-4 plus the glutamine that follows them. Thymosin Beta-4 itself is a 43-amino-acid protein found in essentially every mammalian cell type and in high concentration in platelets and wound fluid, and its best-characterised job is binding monomeric G-actin. By sequestering G-actin it acts as a buffer on the cytoskeleton, holding a reservoir of actin monomers that can be released into filaments when a cell needs to change shape, migrate or close a wound. LKKTETQ is the part of the protein that does the actin binding. It is described in the review literature as the central actin-binding domain, residues 17 to 23 plus one additional amino acid, and it is associated with angiogenesis, wound healing and cell migration. That is the entire rationale for the existence of TB-500: if one short stretch carries the actin-binding function, a seven-residue synthetic peptide should be cheaper to make, easier to handle and more stable than a 43-residue protein while doing the same work. The difficulty is that the inference has never been demonstrated in the way the market's confidence implies. The same literature that identifies LKKTETQ as an active site also describes Thymosin Beta-4 as having multiple active regions with different functions, which means the protein's overall effect is not obviously the sum of one domain acting alone. Whether the isolated 7-mer reproduces the full protein's activity is not something the published record settles, and it is worth being direct about that rather than assuming the fragment inherits the parent's results. This matters more than a taxonomic quibble, because it determines which evidence is admissible. When a supplier page cites cardiac repair work, corneal healing, or the dry-eye programme, it is almost always citing work done with full-length Thymosin Beta-4 or with recombinant Thymosin Beta-4. Those are studies of the protein. A page that presents them as the evidence base for a 7-amino-acid fragment is performing a substitution it has not earned, and the substitution is invisible unless someone checks what the intervention column of each trial actually says. There is a second, more mundane identity problem that compounds this one. Products sold as "TB-500" do not reliably contain the fragment. Some contain full-length Thymosin Beta-4, which is a different molecule with a different molecular weight - roughly 4,900 daltons for the protein against roughly 890 for the acetylated 7-mer. Mass spectrometry on a certificate of analysis distinguishes them immediately, because the masses are not close. A buyer who does not check has no way to know which of the two molecules is in the vial, and the reconstitution arithmetic, the reported dosage figures and the evidence discussion all differ depending on the answer. Beyond actin, the parent protein has been described in preclinical work as promoting angiogenesis, modulating inflammatory signalling and supporting cell survival and migration in injured tissue. Those are the mechanisms that motivated the clinical programmes described in the evidence section. They are mechanisms of Thymosin Beta-4. Their applicability to Ac-LKKTETQ is the open question the new trial exists to start answering.

Researched effects

The honest structure of this section is three separate columns that are routinely collapsed into one: what has been shown for the full-length protein in humans, what has been shown for the fragment in humans, and what is reported anecdotally. For full-length Thymosin Beta-4 in humans, there is a substantial and largely serious clinical record, and it is concentrated in ophthalmology. The ophthalmic formulation RGN-259 has been through three sizeable dry-eye trials - ARISE-1 with 317 patients, ARISE-2 with 601, and ARISE-3 with 700 - all completed, and a Phase 3 study in neurotrophic keratopathy is recruiting. That is a real development programme with real enrolment numbers, and it is not a programme most TB-500 pages mention, presumably because eye drops do not sell injectable vials. Separately, recombinant human Thymosin Beta-4 under the code NL005 has completed Phase 2 work in acute myocardial infarction, with trials enrolling 62 and 90 patients and a further study of 189 not yet recruiting; two Phase 1 safety studies in healthy volunteers, enrolling 54 and 30, have completed. The programme also contains failures and abandonments, and those are equally informative. A Phase 2 study in epidermolysis bullosa was terminated. A study in corneal wounds in diabetic patients was terminated. Two cardiac studies - an injectable Thymosin Beta-4 trial in STEMI and an intravenous study in myocardial ischaemia - were withdrawn before enrolling anyone. A page that lists only the completed dry-eye trials is describing half a programme. For the fragment itself, the human column is empty. An earlier version of this page said it contained one entry, NCT07487363, and described what that trial was designed to measure; the record is a self-declared fictional example and the entry was withdrawn on 2026-08-26. Nothing has replaced it. There is no registered, completed or published controlled trial of the acetylated 17-23 fragment in humans, which means there is no human tolerability record, no human pharmacokinetics and no human efficacy signal for the molecule sold under this name - and no trial pending that would produce one. The third column - reported effects - describes faster recovery from soft-tissue injury, improved joint mobility and reduced inflammation, largely from athletic and community settings. There is no controlled human data supporting any of it for this molecule. The preclinical basis is genuine but belongs to the parent protein and to animal models of wound, cardiac and corneal injury, and animal repair models are notoriously generous compared with human outcomes. Nothing here is a claim that TB-500 treats, prevents or improves any condition, and nothing here is medical advice. It is not approved for any use, and the molecule sold as a research chemical is not a medicine.

Dosage — reported ranges (overview)

The reported figures for TB-500 are unusually detached from any study, and it is worth being precise about how detached. What circulates is a loading-then-maintenance pattern: roughly 2 to 5 mg per administration, given about twice weekly for four to six weeks, followed by a lower weekly figure - often described as around 2 mg or less. That structure is close to universal across community sources, which gives it an air of consensus it has not earned. There is no human dose-finding study behind any part of it. There is no published human pharmacokinetic study to justify the twice-weekly interval. And the animal work it is loosely derived from used weight-scaled dosing in rodents, which does not convert to a fixed milligram figure for a person by any accepted method. The usual rationalisation for dosing twice weekly rather than daily is that tissue-level actin signalling persists after the peptide has cleared plasma. That is a reasonable-sounding inference and it may even be right, but it is an inference, and it is doing a lot of work: it is the entire justification for the reported schedule, and it rests on a plasma half-life figure that belongs to a different molecule. The new trial is the first thing that will replace any of this with data. It is a sequential dose escalation - low, medium and high cohorts - with pharmacokinetics among its stated objectives, running 8 weeks of dosing in 80 adults. When it reports, there will for the first time be a measured human exposure profile for Ac-LKKTETQ and a dose range that a safety review board was willing to sanction. Until then, every figure in circulation, including the ones on this page, is a report of what people say rather than a finding. One further caution about reading community reports on this compound in particular. Because a meaningful share of material sold as TB-500 may be full-length Thymosin Beta-4, and because the two molecules differ roughly five-fold in molecular weight, a reported milligram figure does not even reliably describe the same number of molecules between one person's vial and another's. Dose reports on this compound are noisier than they look, and the noise is chemical rather than behavioural. All of the above describes what is reported and what is being studied, for educational purposes. It is not a protocol, not a recommendation, and not medical advice. TB-500 has no approved human dose because it has no approved human use.

A printable protocol sheet with a reconstitution reference and an injection log comes with All-Access Lifetime.

Reconstitution — bac-water math

TB-500 ships as a lyophilised powder, most commonly in 10 mg vials, and has to be reconstituted with bacteriostatic water before any amount can be measured. The arithmetic is the same as for any lyophilised peptide: concentration in mg per mL equals the vial's milligram content divided by the millilitres of bacteriostatic water added, and syringe units equal (target mg / concentration) x 100, because a 1 mL U-100 insulin syringe is graduated into 100 units across its full millilitre. The table below works a 10 mg vial at three volumes against the 2 mg and 5 mg figures commonly discussed - as arithmetic examples, not as recommendations. One practical point falls out of the table and is worth stating plainly: at 2 mL of diluent, a 5 mg example is exactly 100 units, a completely full 1 mL syringe. Any more diluent than that and the larger example no longer fits in a single U-100 syringe at all, which is a real constraint on how thin it is sensible to mix a compound dosed in whole milligrams. The calculator on this page runs the same computation for any vial size and volume.

This is concentration math, not a dose recommendation.

Injection / administration basics

Reported administration is subcutaneous - commonly into abdominal subcutaneous tissue - or intramuscular, using aseptic technique with rotation between sites. It is described consistently as injectable only; there is no oral or nasal route in the reported literature or in the trial, which administers it by injection. General handling concepts such as sterile technique, site rotation and consistent timing are covered here as general educational information. This is not a personal administration protocol, and nothing here should be read as instruction to administer anything to a person.

Half-life & frequency rationale

There is no published human half-life for the TB-500 fragment. This is a real absence rather than an oversight in this guide. An earlier version of this page supported that point by noting a registry trial had pharmacokinetics among its objectives; that record turned out to be a self-declared fictional example and the reference was withdrawn on 2026-08-26. The absence itself is unchanged, and rests on the literature: no pharmacokinetic study of the acetylated 17-23 fragment in any species has been located. The figures that circulate - typically around 2 to 3 hours - describe full-length Thymosin Beta-4 in circulation, which is a 43-amino-acid protein rather than the acetylated 7-mer. Quoting the protein's number for the fragment assumes that a molecule roughly one-fifth the size, with different termini and no acetyl group on the protein version, clears at the same rate. That is not a safe assumption for peptides, where chain length and terminal modification are among the main determinants of proteolytic stability; the acetylation on the fragment's N-terminus exists specifically to slow aminopeptidase attack, which would if anything push the two numbers apart. The practical consequence is that the reported twice-weekly schedule has no measured pharmacokinetic basis for this molecule. It may turn out to be reasonable - tissue-level effects genuinely can outlast plasma presence - but at present it is a schedule inherited from inference rather than derived from data, and anyone quoting a specific half-life for TB-500 should be asked which study produced it.

Stacking — overview

TB-500 appears in more named combinations than almost any other research-market peptide, essentially always alongside BPC-157, on the rationale that the two act through different repair mechanisms - actin/cytoskeletal and angiogenic on one side, and BPC-157's growth-factor and vascular signalling on the other. It is worth noting that this pairing rationale is built on two compounds neither of which has controlled human efficacy data for the use in question, so the combination inherits both uncertainties rather than cancelling them. A specific practical warning applies whenever these two share a protocol: reported TB-500 figures are in milligrams while reported BPC-157 figures are in micrograms, a thousand-fold difference, so their syringe-unit numbers are never interchangeable even when both vials are mixed to the same volume. Mechanism-level detail on each combination, and the combination-specific cautions, are covered in the paid TB-500 Stacking Module included with this guide.

For how combinations are grouped by research context, the named blends, and why a pre-mixed blend vial cannot be calculated from its total milligrams, see the peptide stacks guide.

Storage & handling

• Lyophilised and unopened: store cold; the dry powder is the stable form and tolerates shipping without refrigeration for short periods.
• Reconstituted: refrigerate at roughly 2-8 degrees Celsius. Commonly reported usable windows are around four to six weeks, which is a handling convention rather than a stability figure measured for this peptide.
• Avoid repeated freeze-thaw cycles, and avoid shaking - direct the bacteriostatic water down the vial wall and let the powder dissolve rather than agitating it.
• Protect from light, and keep the vial stopper wiped with alcohol before each entry; the benzyl alcohol in bacteriostatic water inhibits bacterial growth but is not a substitute for aseptic technique.

Evidence File

The TB-500 Evidence File: One Fictional Record, Nineteen Real Ones, and the Human PK Table

Almost every TB-500 page inherits its evidence from somewhere else - from trials of a different molecule, by a different route, at doses written in different units. This module rebuilds the record from the registry outward. It maps every ClinicalTrials.gov study in the thymosin beta-4 family, reads the posted outcome tables rather than the abstracts, checks in the sponsors' own words what stopped each halted programme, and traces the human pharmacokinetic data sitting behind the half-life figure the market repeats. It also reads the single registry record that names TB-500 itself, field by field, and reports what those fields say.

• The only registry record naming TB-500 describes itself as a fictional example
• LKKTETQ and Ac-LKKTETQ each return zero studies on ClinicalTrials.gov
• ARISE-2, 601 patients: neither co-primary separated from placebo in the posted table
• Measured human half-life 0.5 to 2.08 hours - for the 43-residue parent protein

Sourcing File

The TB-500 Sourcing File: 889.5, 847.5, and the Forty-Two Daltons Between Them

The usual advice for buying this compound is to check that the mass on a certificate is around 890 rather than around 4,900. That check is real, and it catches the least likely substitution. This module works the identity out to the decimal place from primary databases, counts the residues rather than repeating the count everyone else repeats, and identifies the one substitution that a purity-only certificate is structurally unable to detect. It then works the salt, water and purity arithmetic through a labelled vial line by line, and specifies what a certificate has to state before any concentration figure means anything.

• Neutral monoisotopic 888.492; the ion to look for on a certificate is 889.499
• The unacetylated form is 42.011 Da lighter and has a CAS number of its own
• A compliant, honestly reported 10 mg vial delivers about 7.9 mg of peptide
• Zero Trp, Tyr or Phe: a 280 nm purity figure is meaningless for this sequence

Benefit & Outcome Review

The TB-500 Benefit and Outcome Review: Every Claim Graded Against the Molecule in the Vial

Every marketed claim for this compound is graded here against evidence for the seven-residue fragment specifically, with the parent protein's human record shown separately as context rather than allowed to stand in for it. That separation is the whole exercise, and this module adds a second one the market never makes: between the acetylated peptide actually sold and the unacetylated peptide that most of the published biology used. The module reports what was measured, in what species, against what comparator, over what duration, and then traces each circulating number back to the document it came from.

• Most published biology used the unacetylated peptide, not the acetylated one sold
• In the only head-to-head screen, the parent peptide missed significance
• BPC-157 plus TB-500 gave no additional benefit over either agent alone
• A 5 mg figure is close to 16x the molar amount of the largest human dose given

Guide FAQ

Quick answers about guide scope, access, and educational use context.