# TB-500 FAQ: Safety, Side Effects, Legal Status, and the Research, Answered > TB-500 questions answered from the research record: is TB-500 safe, side effects, the difference between TB-500 and BPC-157, long-term use, FDA and WADA status, and the thymosin beta-4 evidence. 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](/faq), 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](/faq) 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](/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]. --- TB-500 Store runs the thymosin beta-4 literature as a single luminous pipeline — the Ac-LKKTETQ fragment traced from actin binding to tissue repair, every full-length-protein substitution flagged in line, the empty human-trial node left lit, and FDA's 503A standing read before anything else; a research repository, not a clinic, a vendor, or a prescription.