Questions, answered at the source
TB-500 FAQ: the common questions, answered from the literature.
Direct answers, the fragment-versus-protein line drawn each time, every quantitative claim cited.
What is TB-500?
TB-500 is the synthetic N-acetylated heptapeptide Ac-LKKTETQ, corresponding to residues 17–23 — the actin-binding motif — of the 43-amino-acid protein thymosin beta-4 [1]. It has a molecular weight near 889 Da and is supplied as a research and veterinary peptide [5]. Most published efficacy data, though, come from the full-length protein, not this seven-residue fragment [5].
What does TB-500 stand for and what does TB stand for in TB-500?
"TB" references thymosin beta-4, the parent protein; "TB-500" is a research and veterinary designation for the synthetic Ac-LKKTETQ fragment of that protein [5]. It is not an abbreviation for a tuberculosis compound. The name points back to thymosin beta-4 and the LKKTETQ actin-binding core the fragment carries [1].
What is TB-500 used for in research?
In animal and in-vitro work, the parent peptide is studied for wound healing, tissue repair, angiogenesis, and cardiac and neurological recovery [5]. The strongest single figure is a +61% gain in rat wound re-epithelialization by day 7 with full-length thymosin beta-4 [3]. Human efficacy of the seven-mer is unproven; no completed controlled trial of the fragment exists [5].
How does TB-500 work?
The LKKTETQ motif is thymosin beta-4's actin-binding region. The parent protein sequesters monomeric G-actin one-to-one, capping both ends to buffer the unpolymerized pool, and that cytoskeletal control links to cell migration, angiogenesis, and anti-inflammatory signaling [1][5]. A 2 Å crystal structure fixed the 1:1 sequestration as the structural basis [1]. The fragment carries the binding core; whether it reproduces the full repertoire is unproven.
Does TB-500 promote angiogenesis and is that a safety concern?
Thymosin beta-4 is reported to drive endothelial migration and new-vessel formation, and yes — the same pro-angiogenic activity is exactly why a tumor/angiogenesis safety signal is taken seriously [7]. Repair and tumor support are the same mechanism pointed at different tissue: the protein is overexpressed in several cancers and implicated in tumor angiogenesis [5]. The full treatment is on the TB-500 angiogenesis research page.
Does TB-500 increase VEGF and new blood vessel formation?
In vitro, thymosin beta-4 induced VEGF expression in a HIF-1α-dependent manner — a defined molecular route to its reported pro-angiogenic effects [8]. VEGF is the principal driver of endothelial sprouting, and reviews describe the downstream result as enhanced endothelial migration and tube formation [7]. Whether the seven-mer reproduces this VEGF induction at research doses is not established.
Does TB-500 work for muscle tears and recovery from exercise?
Muscle-injury-induced thymosin beta-4 acts as a myoblast chemoattractant, which is the rationale for recovery interest. But a six-month mdx-mouse study found more regenerating fibers without gains in strength — a notable null functional result [5]. There is no controlled human trial showing the fragment improves muscle-tear recovery or exercise outcomes.
Can TB-500 help with tendon injuries and ligament repair?
Thymosin beta-4 enhanced medial collateral ligament healing in rats — one of the few direct connective-tissue findings underpinning the athletic-recovery rationale [5]. But human ligament and tendon data are absent, and that single rat ligament result used the full-length protein, not the fragment. No controlled human trial supports tendon or ligament benefit from TB-500 [5].
Does TB-500 affect the heart?
Thymosin beta-4 activated PINCH–ILK–Akt survival signaling and improved cardiac function after coronary ligation in mice [2]. The story is not uniform, though: systemic thymosin beta-4 failed to attenuate myocardial ischemia-reperfusion injury in a porcine study [9]. Both are full-length-protein results; no human cardiac efficacy is established for the seven-mer.
Does TB-500 have neuroprotective effects on the brain?
In a rat embolic-stroke dose-response study, intraperitoneal thymosin beta-4 improved neurological function at 2 and 12 mg/kg but not at 18 mg/kg, with a modeled optimum near 3.75 mg/kg [4]. The response is non-monotonic — higher was not better. That finding is full-length protein in rats; there is no human neuroprotection trial of the fragment.
Does TB-500 reduce inflammation?
Thymosin beta-4 inhibited TNF-α-induced NF-κB activation and IL-8 expression in vitro, the mechanistic basis for its reported anti-inflammatory effects [5]. It is also reported to reduce myofibroblast number, lowering scar formation [12]. These are in-vitro and animal findings for the full-length protein; no controlled human anti-inflammatory trial of the fragment exists.
Does TB-500 help wound healing?
In a rat full-thickness wound model, full-length thymosin beta-4 raised re-epithelialization by 42% at 4 days and up to 61% at 7 days versus saline, with increased contraction, collagen deposition, and angiogenesis [3]. As little as 10 pg stimulated keratinocyte migration two- to three-fold [3]. This is rodent data for the protein, not human evidence for the seven-mer.
Does TB-500 cause cancer or promote tumor growth?
Thymosin beta-4 is overexpressed in several cancers and implicated in metastasis and tumor angiogenesis, so the pro-migratory, pro-angiogenic activity that aids repair could in principle support tumor progression [5]. Whether the isolated fragment carries this risk in humans is not established — there is no controlled trial — but the signal is grounded in the protein's documented cancer biology, which is why caution is warranted [13].
Does TB-500 increase hair growth?
Nanomolar thymosin beta-4 stimulated hair-follicle bulge stem cells and hair growth in rodents [5]. That is animal data for the full-length protein, not human evidence for the fragment. No controlled human trial has shown TB-500 increases hair growth in people.
Are there any human clinical trials on TB-500?
No completed controlled trials of the seven-mer exist [5]. Human data are limited to full-length thymosin beta-4: a randomized, placebo-controlled Phase 1 intravenous safety study (well tolerated to 1260 mg) and topical ophthalmic thymosin beta-4 (RGN-259) dry-eye trials [6][5]. None of those tested the Ac-LKKTETQ fragment, and none measured efficacy of TB-500 in people.
How long does it take for TB-500 to work for injury healing?
No validated human timeline exists. Rodent wound studies showed re-epithelialization gains within days — +42% by day 4, +61% by day 7 — but those used full-length thymosin beta-4 in animals, not the fragment in humans [3]. Any human-recovery timeframe is unsupported by controlled data.
What are the side effects of TB-500?
Human safety data for the fragment are scarce. A Phase 1 intravenous study of full-length thymosin beta-4 was well tolerated to 1260 mg, with no dose-limiting toxicities or serious adverse events [6]. The chief concern is not an acute adverse-event profile but the theoretical tumor/angiogenesis signal tied to the protein's biology [5].
What is the difference between TB-500 and BPC-157?
They are chemically unrelated peptides studied for overlapping repair endpoints. TB-500 is the thymosin beta-4 actin-binding fragment (Ac-LKKTETQ), while BPC-157 is a separate gastric-derived sequence [5]. Neither is FDA-approved [1]. The shared marketing as "healing peptides" obscures that they have different sequences, different proposed mechanisms, and separate evidence bases.
Is TB-500 safe for long-term use?
There are no long-term human safety data for the fragment [5]. The absence of any completed controlled trial, combined with the tumor/angiogenesis signal, means long-term safety is unestablished [5][13]. Stating otherwise would go beyond what the literature supports.
Is TB-500 FDA approved?
No. TB-500 has no approved therapeutic indication; the FDA lists the LKKTETQ fragment under the TB-500 name and placed it in 503A Category 2 for significant safety risks, and it is not within the enforcement-discretion policy for compounding [1][2]. It is a research-chemical and veterinary-context substance, not an approved medicine. Full detail is on the TB-500 legal status and 503A access page.
Is TB-500 banned by WADA and in competitive sports?
Yes. TB-500 and thymosin beta-4 fall under the World Anti-Doping Agency's prohibited peptide and growth-factor / tissue-repair categories and are banned in and out of competition for the relevant classes [5]. The substance is detected by LC-MS anti-doping assays in equine and human matrices [5]. WADA prohibition is independent of the FDA compounding question.
Why is TB-500 used in racehorses?
TB-500 was marketed as a veterinary preparation and was encountered as a designer drug in racehorses, which prompted the first equine LC-MS detection methods to control its misuse in sport [5]. That veterinary and anti-doping history is part of why the fragment carries a research and veterinary designation, and why analytical detection of the seven-mer dominates much of the non-academic literature on it.
Is TB-500 legal?
Legality depends on context. By FDA status, TB-500 is not an approved drug and is in 503A Category 2, not eligible for routine 503A compounding while that status stands [1][2]. In sport it is prohibited by WADA [5]. It is sold by research suppliers for laboratory use and classified as a prescription medicine in some jurisdictions [5]. See TB-500 legal status and 503A access.
Can you get TB-500 from a compounding pharmacy?
Under the framework as it stands, not through routine 503A compounding. A 503A pharmacy may use a bulk substance only if it has a USP/NF monograph, is a component of an approved drug, or appears on the FDA 503A bulks list; TB-500 meets none and, as a Category 2 substance, is not eligible while that status stands [2][1]. Any lawful access still requires a prescriber evaluation and valid prescription [2].
What is the FDA 503A status of TB-500?
TB-500 is in 503A Category 2 — a bulk drug substance the FDA identified as one that may present significant safety risks, placed there effective with the September 29, 2023 nominated-substances update [1]. Category 2 substances are not covered by the enforcement-discretion policy that applies to Category 1 [2]. The fragment is also on the July 23–24, 2026 PCAC agenda as a candidate under evaluation — a scheduled discussion, not a decision [3].