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]. FDA's safety-risk page, marked current through April 22, 2026, records the LKKTETQ fragment's nomination as withdrawn and no longer carries it in Category 2, while keeping the agency's stated safety rationale beside it; FDA has not stated whether a pharmacy may compound it after the withdrawal [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].