TB-500: what it is, what the research shows and how it differs from thymosin beta-4

TB-500 is the name used for a short synthetic peptide with the sequence Ac-LKKTETQ: seven amino acids with an acetyl group on the first one. Researchers at Ghent University identified this acetylated 17–23 fragment of human thymosin beta-4 as the active content of products sold as TB-500, and synthesised it as a reference standard for anti-doping tests ^[2]. The FDA uses the same description, “thymosin beta-4, fragment (LKKTETQ), also known as TB-500” ^[12].

Thymosin beta-4 (Tβ4) is a natural 43-amino-acid protein. It was first isolated from calf thymus and its full sequence was published in 1981 ^[1]. It is one of the main proteins that bind actin, the building block of the cell’s internal skeleton ^[5]. The LKKTETQ stretch sits inside Tβ4’s actin-binding region, which is why it was chosen as a small stand-in for the whole protein ^[3].

This distinction matters. TB-500 is not the same molecule as thymosin beta-4, and results obtained with one cannot simply be assumed for the other. Throughout this page we say which molecule each study used. TB-500 is often discussed alongside BPC-157, which is an unrelated peptide, and it should not be confused with thymosin alpha-1, a different thymus-derived peptide with an immune role.

A 2012 paper from the Hong Kong Jockey Club racing laboratory described TB-500 as a veterinary preparation whose key ingredient is N-acetylated LKKTETQ, and developed a test to control its misuse in equine sport ^[21]. It is now sold online as a TB-500 peptide in freeze-dried vials, usually labelled for research use.

Full-length thymosin beta-4 binds and holds individual actin units, which affects how cells change shape and move. In laboratory and animal work it stimulated migration of skin cells (keratinocytes) and increased new blood-vessel formation and collagen deposition in wounds ^[4]. In the heart, a 2004 Nature study found that Tβ4 formed a complex with the proteins PINCH and integrin-linked kinase, activated the survival signal Akt, and improved heart-muscle survival and function after induced heart attacks in mice ^[5].

Whether the seven-amino-acid fragment reproduces these effects is less clear. In a 2003 study from the US National Institutes of Health, the synthetic peptide LKKTETQ (without the acetyl group) promoted skin-wound repair in aged mice to a degree comparable with full-length Tβ4 ^[3]. A 2024 study that tracked how TB-500 is broken down found that its main metabolite in rats was the fragment Ac-LK, and that in cultured fibroblasts only the metabolite Ac-LKKTE, not TB-500 itself, significantly improved wound closure. The authors suggested that wound-healing activity attributed to TB-500 may come from this metabolite ^[6].

A 2012 review by researchers who worked on thymosin beta-4 for decades summarised its proposed roles. After injury, Tβ4 is released by platelets, macrophages and other cells; in laboratory and animal models it reduced cell death, inflammation and microbial growth, promoted the migration of stem and progenitor cells, and reduced the number of scar-forming myofibroblasts in wounds ^[18]. These are properties of the whole protein. How many of them TB-500 shares has not been tested directly.

Much of the wound-healing literature uses full-length Tβ4. In a 1999 rat study, Tβ4 applied to the skin or injected into the abdomen increased re-epithelialisation of full-thickness wounds by 42% over saline at four days and by up to 61% at seven days, and treated wounds contracted at least 11% more ^[4]. The 2003 NIH study extended this to diabetic and aged mice, and is the main published animal evidence that the LKKTETQ fragment itself has wound-healing activity ^[3].

Heart research, again with full-length Tβ4, has attracted wide attention because of the 2004 mouse study described above ^[5]. None of this cardiac work used TB-500.

The eye is where thymosin beta-4 has gone furthest in clinical development. A 2018 review by the ophthalmologist who led much of this work described Tβ4 as a candidate treatment for corneal wound healing disorders and said phase 3 trials in dry eye and neurotrophic keratopathy were under way ^[25]. ClinicalTrials.gov lists three completed trials of RGN-259, a Tβ4 eye drop, for dry eye (ARISE-1, ARISE-2 and ARISE-3, with 317, 601 and 700 participants) and a phase 3 trial in neurotrophic keratopathy that was still recruiting when we checked ^{[26] [27]}. We did not find a peer-reviewed report of the phase 3 outcomes. These thymosin beta-4 corneal wound healing studies use the whole protein in eye drops, not TB-500.

Direct studies of TB-500 are few. The clearest is a 2026 rat study from Turkey in which 32 rats had their Achilles tendons cut and repaired, then received a product described as TB-500 (60 µg/kg/day), BPC-157 (10 µg/kg/day), both, or nothing for four weeks. The TB-500 group had significantly higher maximum load to failure than controls and better tissue scores on two histology scales; combining the two peptides gave no extra benefit ^[7]. It was a small, exploratory study, and the authors called for dose-finding and longer-term work.

A 2026 Sports Medicine review of peptides marketed for injuries and performance, which covered both Tβ4 and TB-500, concluded that many unapproved peptides show favourable repair outcomes in animals but that rigorous human safety data are scarce ^[11]. A separate 2026 scoping review in the American Journal of Sports Medicine, covering TB-500 with BPC-157 and four other peptides, found that two-thirds of the relevant publications were animal studies and that claimed benefits for musculoskeletal recovery are not supported by current human trials ^[22].

Hair: a 2004 study found that full-length thymosin beta-4 stimulated hair growth in normal rats and mice, and that nanomolar concentrations increased the migration and differentiation of hair follicle stem cells in culture ^[16]. No study has tested TB-500 for hair growth, and no human hair study of either molecule has been published.

Heart: the animal heart findings described above, and the human heart trials described below, all used full-length Tβ4 ^{[5] [20]}. There are no heart studies of TB-500 itself.

Muscle, joints and general recovery: the only TB-500 study in injured tissue is the rat Achilles study ^[7]. Claims that TB-500 builds muscle, improves flexibility or speeds recovery from training have no published support in animals or people. We also found no study of TB-500 and erectile function, in either direction, including in combination with BPC-157.

We found no published human trial of TB-500. The human trials that exist used full-length synthetic thymosin beta-4, usually given at doses and by routes quite different from those discussed online.

In a phase 1 randomised, placebo-controlled study, healthy volunteers received intravenous Tβ4 at 42, 140, 420 or 1,260 mg as a single dose and then daily for 14 days. Adverse events were infrequent and mild or moderate, with no dose-limiting toxicity or serious adverse events ^[8]. In a phase 2 double-blind trial in 73 patients with venous leg ulcers across eight European sites, topically applied Tβ4 had a safety profile comparable to placebo; the authors reported that a 0.03% strength “may have the potential” to speed healing ^[9]. In a small phase 2 eye study, nine patients with severe dry eye used 0.1% Tβ4 eye drops (RGN-259) or vehicle six times a day for 28 days, with statistically significant improvements in discomfort and corneal staining in the treated group ^[10].

These results are for a different, much larger molecule and do not show that TB-500 is effective or safe.

Heart attack trials have produced mixed results. A planned phase 2 trial of intravenous Tβ4 (RGN-352) in heart attack patients was withdrawn from ClinicalTrials.gov with the note that it was never started, so no RGN-352 outcomes exist ^[24]. In China, a recombinant form of human Tβ4 (NL005) was tested in a phase 1 study in 54 healthy volunteers given single intravenous doses and 30 given daily doses for 10 days; adverse events were mild to moderate, with no serious ones ^[19]. A later randomised, double-blind trial in 96 patients with ST-elevation heart attack found no significant difference in infarct size between recombinant Tβ4 and placebo overall; in the 43 patients who received the first dose within eight hours of their procedure, infarct areas were significantly smaller at 90 days ^[20]. That subgroup finding needs confirmation, and it concerns the full protein, not TB-500.

Other registered thymosin beta-4 trials used a topical gel or eye drops. A placebo-controlled trial in 72 people with pressure ulcers applied 0.01%, 0.02% or 0.1% Tβ4 gel once daily for up to 84 days and is listed as completed ^[33]. A trial of Tβ4 gel in the inherited skin-blistering condition epidermolysis bullosa enrolled 30 people and was terminated, the registry says, because of lack of patient availability and expiry of the study drug ^[34]. A trial of Tβ4 eye drops for corneal wounds in people with diabetes enrolled 12 people and was stopped for slow recruitment ^[14]. None of these trials tested TB-500.

There is no human evidence on how long TB-500 takes to work, because it has not been tested in people. In the only TB-500 treatment study, rats were assessed four weeks after Achilles repair ^[7]. The timepoints in studies of full-length Tβ4 range widely: rat skin wounds were measured at four and seven days ^[4], the dry eye trial ran for 28 days ^[10], the pressure ulcer gel trial allowed up to 84 days of treatment ^[33], and the heart attack trial measured infarct size at 90 days ^[20]. These reflect how each study was designed, not a timeline anyone can expect from a vial of TB-500.

No. Thymosin beta-4 (often shortened to TB4 or Tβ4) is the full 43-amino-acid protein that occurs naturally in the body ^[1]. TB-500 is a synthetic seven-amino-acid piece of it, residues 17 to 23, with an acetyl group added ^[2]. The piece contains the part of Tβ4 that binds actin ^[3], but it is only seven of the protein’s 43 amino acids.

The difference shows up in the research. The human trials, the heart studies and the eye drops all used full-length Tβ4 ^{[8] [9] [10]}. The one piece of animal evidence for the fragment’s wound-healing effect used LKKTETQ without the acetyl group ^[3], and a 2024 study found that TB-500 itself did not improve wound closure in cultured cells, while one of its breakdown products did ^[6]. Some sellers label vials as “TB-500 (thymosin beta-4)”; the label alone does not tell you which molecule is inside, which is one reason a certificate of analysis that reports the measured mass matters.

TB-500 itself: the 2026 rat tendon study used 60 µg/kg/day by intraperitoneal injection for four weeks ^[7]. This is an animal dose, and no human dose of TB-500 has been established.

Full-length thymosin beta-4 (not TB-500): the phase 1 study used 42 mg to 1,260 mg intravenously, once or daily for 14 days ^[8]; the venous ulcer trial tested topical strengths including 0.03% ^[9]; and the dry eye trial used 0.1% eye drops six times daily ^[10]. These figures describe what studies used, are not recommendations, and should not be transferred to TB-500. For converting vial contents to a concentration, see the peptide calculator.

In the horse detection study, researchers gave a single dose of a TB-500 product containing 10 mg of the peptide to confirm their test could find it afterwards; it was not a treatment study ^[21]. TB500 dosage charts, weekly schedules and “loading” and “maintenance” phases found online do not come from any published trial.

Questions about TB-500 dosage in units are arithmetic. As an illustration only, a vial labelled 5 mg dissolved in 2 mL of liquid gives 2.5 mg per mL, so 0.1 mL of that solution holds 0.25 mg, and 0.1 mL is 10 units on a U-100 insulin syringe. Adding more or less bacteriostatic water changes the concentration, not the amount in the vial, and the sum only holds if the vial contains what its label states.

BPC-157 and TB-500 are the peptides most often sold as a pair, both as separate vials and as a premixed BPC-157 TB-500 blend, sometimes called a “wolverine stack”. One published study has tested them together. In the 2026 Turkish rat study, animals given both peptides after Achilles tendon repair did no better than those given either peptide alone; TB-500 alone produced the clearest gain in tendon strength at four weeks ^[7]. That is the only direct evidence on the combination. Everything published on the pairing is collected in BPC-157 and TB-500. What is and is not known about these blends is set out in Glow and Klow peptide blends.

No published study has tested a premixed BPC-157 and TB-500 blend, a combined dose, or whether the two peptides remain stable together in one vial. The same is true of three- and four-peptide blends that add GHK-Cu or KPV. A BPC-157 and TB-500 blend dosage calculator can split a vial’s stated contents into amounts, but no trial supplies a dose to split. What is known about the other half of the pair is set out in our BPC-157 guide.

The two peptides are unrelated. TB-500 is a fragment of thymosin beta-4 and is thought to act through actin and cell migration ^[3]. BPC-157 is a 15-amino-acid peptide based on a gastric juice protein, and its research centres on blood-vessel growth and the nitric oxide system. The research base also differs: BPC-157 has many rat studies and a few small, uncontrolled human reports, while TB-500 itself has a handful of animal and cell studies and no human data, with most cited human evidence coming from full-length Tβ4 ^{[8] [22]}. In the one head-to-head rat study, TB-500 gave the larger strength gain ^[7]. Both are prohibited in sport.

There are no human safety data for TB-500. The reassuring phase 1 and 2 safety findings apply to pharmaceutical-grade full-length Tβ4 given under trial conditions ^{[8] [9] [10]}. The FDA has said that compounded TB-500 may carry a risk of immune reactions (immunogenicity) for some routes of administration and of peptide-related impurities ^[12].

Product quality is a specific concern. A 2023 analysis by French anti-doping researchers found that the contents of products sold online as TB500 and TB1000 were not consistently what their descriptions claimed ^[13]. Without independent testing, buyers cannot assume a vial contains what its label states.

Does thymosin beta-4 cause cancer? No study has shown that Tβ4 or TB-500 causes cancer. The concern comes from the other direction: a 2012 review summarised evidence that Tβ4 is expressed at higher levels in a number of metastatic tumours, together with the blood-vessel growth factor VEGF, and proposed blocking Tβ4 as a possible cancer treatment ^[17]. That association does not show that taking Tβ4 or TB-500 starts or speeds a cancer, but no study has tested that question. A 2026 review of unregulated injectable peptides listed pathological blood-vessel growth and cancer among potential risks of TB-500, BPC-157 and similar products ^[23].

Side effects described in online anecdotes have not been recorded in any published study of TB-500, so their nature and frequency are unknown. Our guide to third-party peptide testing explains what independent tests can and cannot confirm about a vial.

No study has published a half-life for TB-500 in people. In the 2024 rat study, the metabolite Ac-LK was the most abundant in the first six hours after dosing, while a longer fragment, Ac-LKK, was still detectable in urine up to 72 hours later ^[6]. For full-length Tβ4 given intravenously to volunteers, the half-life increased as the dose increased ^[8]. Anti-doping laboratories can detect the acetylated peptide and its metabolites in horse plasma and urine ^[21].

TB-500 has been studied by injection only, in rats ^[7]. We found no published study of TB-500 nasal spray, oral TB-500 or TB-500 capsules. Full-length Tβ4 has been studied intravenously, as a topical gel and as eye drops ^{[8] [9] [10]}.

TB-500 is not approved as a medicine anywhere we are aware of. In the US, the FDA previously placed “thymosin beta-4, fragment (LKKTETQ), also known as TB-500” in category 2 of its interim compounding policy, the list of bulk substances that may present significant safety risks; the nomination was later withdrawn and the FDA now lists it among substances previously in category 2 ^[12]. On 23 July 2026, the FDA’s Pharmacy Compounding Advisory Committee met and considered TB-500 for the list of bulk substances US pharmacies may compound. The FDA’s meeting page posted no votes or outcome, and as of September 2026 the FDA has not acted ^[32]. The committee’s advice is not binding and would not amount to approval.

The World Anti-Doping Agency lists “thymosin-β4 and its derivatives, e.g. TB-500” under S2 (peptide hormones, growth factors and related substances), so it is prohibited at all times for athletes in WADA-compliant sport ^[15]. Country-level rules on buying research peptides are covered on our legal status pages, including the UK page.

In Australia, TB-500 and thymosin beta-4 are listed in Schedule 4 (prescription only) of the Poisons Standard and in Appendix D, clause 5, which restricts possession without authority ^[28]. The TGA gives TB-500 as an example of an unapproved peptide product ^[29]. In New Zealand, Medsafe classifies TB-500 and thymosin beta-4 as prescription medicines ^[30], and a Health Canada advisory in April 2026 named TB-500 among seized unauthorised peptide products ^[31]. See the Australia page for more detail.

TB-500 is sold as a freeze-dried powder. As with other peptides, the dry powder is generally kept cold, dry and away from light, and reconstituted solutions are refrigerated and used within a limited time. See how to store peptides for general principles.

Because products labelled TB-500 vary in what they contain, independent testing matters more than usual. You can compare prices, read our guide on how to read a COA, and filter for third-party tested suppliers.

We track listings for TB-500 UK prices and US prices, but availability does not mean a product is legal to buy where you live. A mass spectrometry result that matches the mass of Ac-LKKTETQ (about 889 g/mol) is the most direct check that a vial holds TB-500 rather than full-length thymosin beta-4 or something else. Our guide to spotting a fake peptide supplier covers other warning signs.