TB-500, answered

What is TB-500?

TB-500 is the synthetic N-acetylated heptapeptide Ac-LKKTETQ — residues 17-23 (the actin-binding motif) of the 43-amino-acid protein thymosin beta-4 ^[1]. Its molecular weight is 889.02 Da. Most efficacy data are on the full-length parent protein, not the 7-mer, which is the central caveat to every TB-500 claim.

What does TB-500 stand for and what does TB stand for in TB-500?

TB is a thymosin-beta designation. TB-500 denotes the LKKTETQ actin-binding fragment of thymosin beta-4, supplied as a research and veterinary-context peptide ^[1]. The "500" is a product-style designation, not a chemical descriptor; the meaningful identity is the Ac-LKKTETQ sequence.

What is TB-500 used for in research?

In research it is studied for tissue repair, cell migration, angiogenesis, and — as full-length thymosin beta-4 — cardiac, neurological, and other repair endpoints in animal models ^[5][3][4]. It has no approved human use. The findings are preclinical and mostly on the parent protein rather than the marketed fragment.

Does TB-500 have neuroprotective effects on the brain?

In rat stroke and traumatic-brain-injury models, thymosin beta-4 improved neurological outcome ^[4][7], and a 2024 zebrafish study showed it promotes axon regeneration via actin dynamics ^[12]. The embolic-stroke dose-response was non-monotonic — benefit at 2 and 12 mg/kg, none at 18 ^[4]. This is animal-only; there is no human efficacy data.

What dose of thymosin beta-4 was used in stroke studies?

Intraperitoneal thymosin beta-4 was given at 2, 12, and 18 mg/kg starting 24 hours post-stroke, then every three days for four more doses; 2 and 12 mg/kg improved function while 18 mg/kg did not, and a modeled optimal near 3.75 mg/kg was proposed ^[4]. These are animal-study parameters, not a human dose.

Does TB-500 work for muscle tears and recovery from exercise?

A 2026 Sports Medicine review lists TB-500 among unapproved peptides studied for musculoskeletal injury and athletic performance, noting favorable tissue-repair signals in animal models but scarce human safety data and no regulatory approval ^[11]. Recovery claims rest on preclinical evidence, mostly from full-length thymosin beta-4.

Does TB-500 cause cancer or promote tumor growth?

Thymosin beta-4 is overexpressed in some cancers and implicated in metastasis and tumor angiogenesis; the same pro-migratory, pro-angiogenic biology that aids repair is a theoretical tumor-safety concern ^[5]. Human safety data for the fragment are scarce, and a 2026 review flags potential for serious harm ^[11]. This is the most-cited caution in the record.

Is TB-500 banned by WADA and in competitive sports?

Yes. TB-500 falls under WADA's prohibited peptide, growth-factor, and tissue-repair categories and is detected by LC-MS anti-doping assays ^[11]. It is banned in and out of competition for the relevant classes, and it has been encountered as a designer drug in racehorses, prompting equine detection methods.

Is TB-500 FDA approved?

No. TB-500 has no FDA-approved therapeutic indication; FDA placed "Thymosin beta-4, fragment (LKKTETQ), also known as TB-500" in 503A Category 2 ^[17]. It is a research-chemical and veterinary-context substance, not an approved medicine. See /legal-status for the full regulatory record.

Are there any human clinical trials on TB-500?

No completed controlled trials exist for the TB-500 fragment. Human data are limited to full-length thymosin beta-4: an intravenous Phase 1 safety study (40 volunteers) ^[6] and topical ophthalmic RCTs. A 2026 Sports Medicine review lists TB-500 as unapproved with scarce human safety data ^[11].

How does TB-500 work?

The LKKTETQ motif binds monomeric (G-)actin 1:1, capping both ends to buffer the unpolymerized actin pool and regulate cytoskeletal dynamics, cell migration, and motility ^[1]. That actin-sequestration mechanism is the basis for the parent protein's repair, migration, and angiogenic activity ^[5].

How long does it take for TB-500 to work for injury healing?

Timelines come from animal models — for example +42% re-epithelialization at four days and +61% at seven days in a rat wound study using thymosin beta-4 ^[3]. No validated human healing timeline exists for the fragment.

Can TB-500 help with tendon injuries and ligament repair?

Connective-tissue interest rests on thymosin beta-4's broad tissue-repair biology — actin binding, cell migration, and reduced myofibroblast and scar formation ^[5] — and on its listing among unapproved musculoskeletal peptides in a 2026 review ^[11]. Direct tendon and ligament evidence is limited and animal-only; there is no human efficacy data.

Does TB-500 affect the heart?

In mice, thymosin beta-4 activated PINCH-ILK-Akt survival signaling and improved early cardiomyocyte survival and cardiac function after coronary ligation ^[2]; a 2021 porcine study reported enhanced cardiac cell proliferation and engraftment ^[13]. The cardiac evidence is animal-only and mixed across models.

Does TB-500 promote angiogenesis and is that a safety concern?

Thymosin beta-4 promotes endothelial migration and angiogenesis as part of its repair biology ^[5]. The same pro-angiogenic activity is part of the theoretical tumor-safety concern flagged in the literature — the biology that rebuilds tissue could in principle support tumor blood supply.

Does TB-500 reduce inflammation?

Thymosin beta-4 shows anti-inflammatory and anti-fibrotic activity in animal models — for example ameliorating liver fibrosis via MAPK/NF-κB pathway modulation ^[15] — and limits inflammation as a regenerative peptide more broadly ^[5]. The data are on the full-length protein.

What are the side effects of TB-500?

Human safety data for the TB-500 side effects of the fragment are scarce. The main theoretical concern is the tumor and angiogenesis signal ^[5]. Intravenous full-length thymosin beta-4 was well tolerated to 1260 mg in a Phase 1 study with no dose-limiting toxicities ^[6] — but that is not the 7-mer and not a human-use endorsement.

What is the difference between TB-500 and BPC-157?

Both are unapproved research peptides studied for tissue repair, but they have distinct sequences and mechanisms — TB-500 is the thymosin beta-4 actin-binding fragment ^[1]. The 2026 Sports Medicine review lists both as unapproved with limited human data ^[11]. No controlled study tests them in combination.

Does TB-500 help wound healing?

In animal models, yes — topical and intraperitoneal thymosin beta-4 accelerated dermal and corneal re-epithelialization and contraction (+42% at day four, +61% at day seven in a rat study) ^[3]. Human wound data are limited to full-length Tβ4 formulations, not the fragment.

Is TB-500 safe for long-term use?

There are no long-term human studies of the TB-500 fragment, so long-term safety is unknown. The tumor and angiogenesis signal means caution ^[5][11], and it remains a research-use-only substance with no approved human indication.

Why is TB-500 used in racehorses?

TB-500 has been encountered as a designer tissue-repair drug in racehorses, which prompted equine anti-doping detection methods ^[11]. It is used in a veterinary and doping context, not as an approved equine medicine, and it is prohibited under anti-doping rules.

Is TB-500 legal?

It depends on context. In the U.S. it is not FDA-approved and sits in 503A Category 2, so it is not eligible for routine 503A compounding while that status stands ^[17][16]; it is prohibited in sport by WADA ^[11] and is a prescription medicine in some jurisdictions. It is supplied for laboratory research use, not human consumption. See /legal-status.

Can you get TB-500 from a compounding pharmacy?

Not through routine 503A compounding as the status stands — FDA placed TB-500 in Category 2, outside its enforcement-discretion policy ^[17][16]. Legally compounded access otherwise requires a licensed-prescriber evaluation and a valid patient-specific prescription, made by a 503A pharmacy or 503B outsourcing facility ^[16]. See /legal-status.

What is the FDA 503A status of TB-500?

FDA lists it as "Thymosin beta-4, fragment (LKKTETQ), also known as TB-500" and placed it in 503A Category 2 — bulk substances that may present significant safety risks — effective with the September 29, 2023 update ^[17]. It is named on the July 23-24, 2026 PCAC agenda for discussion, which is a scheduled evaluation, not a decision ^[18].