Research board / questions answered
TB-500 FAQ: direct answers, each one cited.
Side effects, mechanism, the muscle and wound and cardiac findings, and the regulatory status — answered from the published record, with the human-data gaps left in plain sight.
What is TB-500?
TB-500 is the synthetic N-acetylated heptapeptide Ac-LKKTETQ — residues 17–23, the actin-binding motif, of the 43-amino-acid protein thymosin beta-4 [1]. It has a molecular weight of about 889 Da. Most efficacy data are on full-length thymosin beta-4, not the seven-mer, which is the central caveat across this site [5].
What does TB-500 stand for and what does TB stand for in TB-500?
"TB" is a thymosin-beta designation. TB-500 denotes the LKKTETQ actin-binding fragment of thymosin beta-4, supplied as a research and veterinary-context peptide [1]. So what TB stands for in TB-500 is thymosin beta; the "500" is a product-style designation, not a chemical descriptor [1].
What is TB-500 used for in research?
In research it is studied for tissue repair, cell migration, and angiogenesis, and — as full-length thymosin beta-4 — for cardiac, neurological, and hair-follicle endpoints in animal models [4][7][9]. It has no approved human use [17]. These are investigational endpoints in animals, not demonstrated human applications of the fragment [5].
How does TB-500 work?
The LKKTETQ motif binds monomeric (G-) actin 1:1, capping both ends to buffer the unpolymerized actin pool and regulate cytoskeletal dynamics, cell migration, and motility [3]. X-ray crystallography established this dual-end-capping sequestration as the structural basis for the wider WH2 protein family [3].
Does TB-500 work for muscle tears and recovery from exercise?
Thymosin beta-4 acts as a myoblast chemoattractant, but a six-month mdx-mouse study found more regenerating fibers without gains in muscle strength or cardiac function [11]. The animal evidence is mixed, and there is no human efficacy data for exercise recovery with the TB-500 fragment [5].
Can TB-500 help with tendon injuries and ligament repair?
In one rat study thymosin beta-4 enhanced medial collateral ligament healing, and it recruits myoblasts to injured muscle, which underpins athletic-recovery interest [7]. Direct connective-tissue evidence is limited and animal-only; no human tendon or ligament trial of TB-500 exists [5].
How long does it take for TB-500 to work for injury healing?
Timelines come only from animal models — for example, +42% re-epithelialization at four days and +61% at seven days in a rat wound study [2]. No validated human healing timeline exists for the fragment, so any "weeks-to-results" figure is not grounded in controlled human data [5].
Does TB-500 help wound healing?
In animal models, yes — topical or intraperitoneal thymosin beta-4 accelerated dermal and corneal re-epithelialization and wound contraction in rats [2]. Human wound data are limited to full-length thymosin beta-4 formulations, not the TB-500 seven-mer [5].
Does TB-500 affect the heart?
In mice, thymosin beta-4 activated PINCH–ILK–Akt survival signaling, improved early cardiomyocyte survival and cardiac function after coronary ligation, and mobilized epicardial progenitors [4]. A porcine study, however, showed no benefit against ischemia-reperfusion injury — so the cardiac record is promising but not uniform.
Does TB-500 have neuroprotective effects on the brain?
In rat stroke and brain-injury models, thymosin beta-4 improved neurological outcome, but the embolic-stroke dose-response was non-monotonic: benefit at 2 and 12 mg/kg, none at 18 mg/kg [11]. The effect is animal-only, and higher doses were not better [11].
Does TB-500 promote angiogenesis and is that a safety concern?
Thymosin beta-4 promotes endothelial migration and angiogenesis [7]. The same pro-angiogenic activity that aids repair is part of the theoretical tumor-safety concern, because new-vessel growth can also support tumors [10]. It is a benefit and a flagged risk for the same biological reason.
Does TB-500 reduce inflammation?
Thymosin beta-4 has anti-inflammatory and pro-resolving activity — suppression of NF-κB/IL-8 signaling and engagement of specialized pro-resolving pathways — plus anti-fibrotic effects in animal models [7][8]. This is among the better-characterized mechanistic effects, though still measured in non-human systems [8].
Does TB-500 cause cancer or promote tumor growth?
Thymosin beta-4 is overexpressed in some cancers and implicated in metastasis and tumor angiogenesis; the same pro-migratory, pro-angiogenic biology that aids repair is a theoretical tumor-safety concern [10]. Human safety data for the fragment are scarce, and the question is unresolved [5].
What are the side effects of TB-500?
Human safety data for the fragment are scarce, so a defined profile of TB-500 side effects is not established [5]. The main theoretical concern is the tumor and angiogenesis signal [10]. Intravenous full-length thymosin beta-4 was well tolerated to 1260 mg in a Phase 1 study, but that is the parent protein, not the seven-mer [6].
Is TB-500 safe for long-term use?
There are no long-term human studies of the TB-500 fragment, so long-term safety is unknown [5]. The tumor and angiogenesis signal is reason for caution [10], and the substance remains research-use-only with no FDA-approved indication [17].
Are there any human clinical trials on TB-500?
No completed controlled trials exist for the TB-500 fragment [5]. Human data are limited to full-length thymosin beta-4: an intravenous Phase 1 safety study [6] and topical ophthalmic trials. A 2026 Sports Medicine review lists TB-500 as unapproved with scarce human safety data [10].
What is the difference between TB-500 and BPC-157?
Both are unapproved research peptides studied for tissue repair, but they have distinct sequences and mechanisms — TB-500 is the actin-binding fragment of thymosin beta-4, while BPC-157 is a separate pentadecapeptide [10]. The 2026 Sports Medicine review lists both as unapproved with limited human data [10].
Why is TB-500 used in racehorses?
TB-500 was encountered as a designer tissue-repair drug in racehorses, which prompted equine LC-MS detection methods [10]. It is used in a veterinary and doping context, not as an approved equine medicine, and its presence in horses drove the forensic analytical work [10].
Is TB-500 banned by WADA and in competitive sports?
Yes — TB-500 falls under WADA's prohibited peptide, growth-factor, and tissue-repair categories and is detected by LC-MS anti-doping assays [10]. It is banned in and out of competition for the relevant athlete classes. See the TB-500 legal status page for the full regulatory record.
Is TB-500 FDA approved?
No. TB-500 has no FDA-approved therapeutic indication; it is handled as a research chemical and veterinary-context substance [17]. FDA placed it in 503A Category 2, outside the enforcement-discretion policy for compounding [17]. The full detail, including the scheduled 2026 review, is on the TB-500 legal status page [18].
Is TB-500 legal?
TB-500 is a 503A Category 2 substance, not FDA-approved and not within FDA's enforcement-discretion policy for compounding [17]; it is WADA-prohibited in sport [10] and is on a scheduled July 2026 FDA compounding-review agenda as a discussion, not a decision [18]. This is general information, not legal advice.
Can you get TB-500 from a compounding pharmacy?
Not through routine 503A compounding while its current status stands: a Category 2 substance FDA has flagged for significant safety risks is not eligible for that compounding [17][19]. The lawful framework requires a licensed-prescriber evaluation and a patient-specific prescription, but the ingredient-eligibility rule is the binding constraint [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 — significant-safety-risk bulk substances — effective with its September 29, 2023 update, citing immunogenicity for certain routes and a lack of important safety information [17]. It is also named on the July 23–24, 2026 PCAC agenda as a bulks-list candidate under evaluation [18].