FAQ ~ answered from the record
TB-500 questions, answered from the research record
Direct answers on safety, side effects, legal status, and the science — each one sourced, and each one clear about whether the data are on the fragment or the parent protein.
Definitions and identity
The most common TB-500 questions are about what the molecule is and what separates it from the protein it is derived from. These are the frequently asked questions about TB-500, each answered directly and cited to the published record.
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 [5]. Most published efficacy research uses the full-length protein, not the fragment [5]. Its molecular weight is ~889 Da versus the protein's ~4963 Da [5].
What does TB-500 stand for and what does TB stand for in TB-500?
TB references thymosin beta. TB-500 is a research and veterinary designation for the synthetic Ac-LKKTETQ fragment of thymosin beta-4 [5]. The related veterinary product TB1000 uses the same naming convention, denoting the same actin-binding fragment family [5].
How does TB-500 work?
TB-500 carries the LKKTETQ actin-binding motif of thymosin beta-4, the body's main G-actin-sequestering peptide [5]. The parent protein binds monomeric actin 1:1 to regulate cytoskeletal dynamics, cell migration, angiogenesis and survival signaling [1]. Whether the isolated seven-mer reproduces this at research doses is unestablished in controlled human trials [5].
Is TB-500 safe? What the evidence does and does not show
There is no completed controlled human trial of the TB-500 fragment, so its safety in people is not established [11]. The nearest human safety data are for full-length thymosin beta-4: intravenous dosing was well tolerated to 1260 mg in a Phase 1 study with only mild or moderate adverse events [6]. The main theoretical concern is the tumor and angiogenesis signal [9].
What are the side effects of TB-500?
No controlled human safety profile exists for the TB-500 fragment [5]. In the Phase 1 study of full-length thymosin beta-4, intravenous dosing to 1260 mg produced only infrequent mild or moderate adverse events with no dose-limiting toxicities or serious adverse events [6]. The principal theoretical concern is the tumor and angiogenesis safety signal tied to the protein [9].
What is the difference between TB-500 and BPC-157?
Both appear in the research literature as unapproved peptides studied for tissue repair — a 2026 Sports Medicine review lists them together [11]. TB-500 is the Ac-LKKTETQ actin-binding fragment of thymosin beta-4; BPC-157 is a separate pentadecapeptide with a distinct mechanism. They are different molecules, and neither is FDA-approved [11]. See TB-500 and BPC-157 compared above.
Is TB-500 safe for long-term use?
Long-term safety of TB-500 in humans is unknown; there are no completed controlled trials of the fragment [11]. Chronic dosing in animal studies showed mixed results — six months of thymosin beta-4 in mdx mice increased regenerating fibers without improving strength — and the tumor and angiogenesis signal remains an unresolved long-term concern [11][9].
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 and tissue-repair categories, banned in and out of competition for the relevant classes, and detected by LC-MS anti-doping assays in equine and human matrices [16]. See TB-500 legal status for the full regulatory picture.
Is TB-500 FDA approved?
No. TB-500 has no FDA-approved therapeutic indication; it is a research chemical and veterinary-context substance, not an approved medicine [18]. The FDA lists the LKKTETQ fragment as a 503A Category 2 bulk substance that may present significant safety risks [17].
Are there any human clinical trials on TB-500?
There are no completed controlled trials of the TB-500 heptapeptide [5]. Human data exist only for full-length thymosin beta-4: a Phase 1 intravenous safety and PK study (well tolerated to 1260 mg), topical ophthalmic RGN-259 dry-eye randomized trials, and registered cardiac trials; one injectable trial was withdrawn [6][10].
Does TB-500 cause cancer or promote tumor growth?
Thymosin beta-4 is overexpressed in several cancers and implicated in metastasis and tumor angiogenesis; the same pro-migratory, pro-angiogenic properties that aid repair could theoretically support tumor progression [9]. This is a theoretical concern, not a demonstrated outcome in people — human safety data for the fragment are scarce [9].
Can TB-500 be taken orally?
Research routes studied for thymosin beta-4 are predominantly intraperitoneal, intravenous, and topical or ophthalmic [16]. Oral dosing of the TB-500 peptide is not supported by controlled efficacy data, and as a research chemical it is not intended for human consumption [16].
What is TB-500 used for in research?
In animal and topical-human models, thymosin beta-4 — the parent protein of the TB-500 fragment — is studied for tissue repair, wound healing, muscle and ligament recovery, cardiac and neurological repair, and angiogenesis [5]. Efficacy of the isolated heptapeptide in humans is unproven [5].