TB-500 FAQ: the questions, answered from the record
Direct answers to the most-asked TB-500 questions — definitional, mechanistic, safety, and regulatory — each cited where it states a number.
What is TB-500 used for in research?
TB-500 is studied as a synthetic actin-binding peptide in tissue-repair, wound-healing, cardiac, neurological, and angiogenesis models. The parent protein thymosin beta-4 carries most of that evidence [5]. The fragment inherits the research interest; the demonstrated effects are largely the parent protein's.
How long does it take for TB-500 to work for injury healing?
No human timeline is established for the fragment. In a rat wound model, full-length thymosin beta-4 raised re-epithelialization by 42% at 4 days and up to 61% at 7 days [3] — an animal-model time course, not a human dosing schedule.
Does TB-500 help wound healing?
In animal and topical models, thymosin beta-4 accelerated dermal and corneal re-epithelialization and increased contraction, collagen, and angiogenesis [3]. Human efficacy of the 7-mer is unproven; the strong wound-healing data are on the parent protein in rodents.
Does TB-500 help corneal or eye healing?
Topical thymosin beta-4 promoted corneal wound healing and reduced inflammation in mice [7], and the clinical-grade formulation RGN-259 improved dry-eye signs in placebo-controlled trials. These results are on Tβ4-based formulations, not the TB-500 fragment as marketed.
What is TB-500?
TB-500 is the synthetic N-acetylated heptapeptide Ac-LKKTETQ — residues 17 to 23, the actin-binding motif, of the 43-amino-acid protein thymosin beta-4 [1]. It is ~889 Da; the parent protein is ~4963 Da.
What does TB-500 stand for?
"TB" refers to thymosin beta-4 (Tβ4). TB-500 is the commercial and veterinary designation for the synthetic Ac-LKKTETQ actin-binding fragment of that protein [1]. The name points at the parent; the substance is the fragment.
Does TB-500 work for muscle tears and recovery from exercise?
Injury-induced thymosin beta-4 recruits myoblasts, but a 6-month mdx-mouse study found more regenerating fibers without gains in strength or cardiac function — a notable null functional result. Mechanism did not translate into measured performance.
Does TB-500 cause cancer or promote tumor growth?
Thymosin beta-4 is overexpressed in several cancers and implicated in metastasis and tumor angiogenesis [5]. The same pro-migratory, pro-angiogenic properties that aid repair are a theoretical oncologic concern, and human safety data for the fragment are scarce.
Is TB-500 banned by WADA and in competitive sports?
Yes. TB-500 and thymosin beta-4 fall under WADA's prohibited peptide/growth-factor and tissue-repair categories, banned in and out of competition, and are detectable by LC-MS anti-doping assays in equine and human matrices.
Is TB-500 FDA approved?
No. TB-500 has no approved therapeutic indication. FDA placed "Thymosin beta-4, fragment (LKKTETQ), also known as TB-500" in 503A Category 2 in 2023 as a substance that may present significant safety risks, a nomination its current page shows as withdrawn [16], and it is sold for research and veterinary use only.
Are there any human clinical trials on TB-500?
No controlled trials of the 7-mer exist. Human data are limited to full-length synthetic thymosin beta-4 — a randomized intravenous Phase 1 safety and PK study [6] and topical ophthalmic (RGN-259) dry-eye trials.
Can TB-500 help with tendon injuries and ligament repair?
One rat study found thymosin beta-4 enhanced medial collateral ligament healing — among the few direct connective-tissue findings. Broader tendon and ligament evidence in humans is lacking, and no controlled human trial supports the fragment here.
Does TB-500 affect the heart?
In mice, thymosin beta-4 activated the PINCH–ILK–Akt survival pathway, improved cardiomyocyte survival, and improved cardiac function after coronary ligation [2]. A porcine ischemia-reperfusion study, however, showed no benefit — the cardiac picture is mixed.
Does TB-500 promote angiogenesis and is that a safety concern?
Thymosin beta-4 drives endothelial migration and pro-angiogenic signaling, which aids repair but is also the basis of the tumor-angiogenesis safety concern [5]. The same mechanism cuts both ways.
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 optimal near 3.75 mg/kg [4]. Higher was not better.
Does TB-500 increase hair growth?
Nanomolar thymosin beta-4 stimulated hair growth in rodents by activating hair-follicle bulge stem cells [5]. This is animal data on the full-length protein, not human evidence for the fragment.
What is the difference between TB-500 and BPC-157?
TB-500 and BPC-157 are distinct peptides with different sequences and mechanisms. TB-500 is the actin-binding thymosin beta-4 fragment [1]; BPC-157 is a separate gastric-derived peptide. Both are unapproved, research-only compounds with limited human data, and neither is interchangeable with the other.
TB-500 and BPC-157: How the Research Differs
TB-500 and BPC-157 are often discussed together, but their evidence bases differ. TB-500's case is dominated by full-length thymosin beta-4 data — actin sequestration [1], wound re-epithelialization [3], and a human Phase 1 of the parent protein [6] — with no completed controlled trial of the fragment itself. BPC-157's literature is its own separate body of gastric-peptide research with a different mechanism. The honest summary is that both are unapproved research compounds whose human evidence is thin, and this site makes no stacking or dosing claim about combining them.
Is TB-500 safe for long-term use?
Long-term human safety is unknown. Chronic dosing has only been studied in animals, and the pro-angiogenic and tumor-overexpression signal [5] makes long-term human use an open safety question that clinical data cannot currently answer.
Is TB-500 legal?
TB-500 is not an approved medicine. It is sold for research and veterinary use, classified as a prescription medicine in some jurisdictions, and is WADA-prohibited [16]. Legality depends on context; this is general information, not legal advice.
Can you get TB-500 from a compounding pharmacy?
Any compounding route has to pass FDA's 503A/503B bulk-substance rules. FDA's page, current as of April 22, 2026, shows TB-500 is no longer in Category 2 after the nomination was withdrawn and retains the agency's safety rationale; FDA has not answered what a 503A pharmacy may do with that change [16][19].
What is the FDA 503A status of TB-500?
FDA placed "Thymosin beta-4, fragment (LKKTETQ), also known as TB-500" in 503A Category 2 — substances that may present significant safety risks — effective with its September 29, 2023 nominated-substances update [16]. The 2023 placement remains part of the history, but FDA now records the nomination as withdrawn and has not explained whether pharmacies may compound TB-500.