RESEARCH DIGEST · FREQUENTLY ASKED QUESTIONS
TB-500: Frequently Asked Questions
Direct answers to the most common questions about TB-500 and thymosin beta-4, drawn from the published research literature.
Questions and Answers
The following questions and answers derive from the published research record. Quantitative claims are cited to the studies that measured them. This is a literature digest — not clinical guidance, not a recommendation for human use.
What is TB-500?
TB-500 (Ac-LKKTETQ) is a synthetic N-acetylated heptapeptide corresponding to amino acids 17–23 of thymosin beta-4, a 44-amino-acid endogenous protein ubiquitous in human and animal cells. The seven-residue sequence constitutes the active actin-binding domain of the parent protein. TB-500 was first formally characterized in a 2012 equine anti-doping study detecting the compound by LC-MS/MS in plasma and urine following a single 10 mg dose [1].
What does TB-500 do?
TB-500 sequesters G-actin monomers, preventing their polymerization into filaments. This redirects cellular actin dynamics toward migration and wound closure. Downstream effects include VEGF and VEGFR2 upregulation (angiogenesis), NF-κB inhibition (anti-inflammation), and AKT/Bcl-XL activation (apoptosis resistance). These mechanisms have been documented across wound, cardiac, corneal, and neurological animal models [6][7][13].
What is TB-500 used for?
In preclinical research, TB-500 has been studied for: wound closure acceleration (42–61% improvement in rat models [2]); tendon and ligament repair [10]; cardiac regeneration [5][16]; angiogenesis in ischemic tissue [7]; neuroprotection after traumatic brain injury [14]; renal fibrosis reduction [15]; and hair follicle activation [8]. No human indication has been approved.
What is TB-500 peptide?
TB-500 is a synthetic analog of the active actin-binding region of thymosin beta-4, a naturally occurring intracellular protein. The synthetic heptapeptide (Ac-LKKTETQ) retains the core G-actin sequestering activity of the 44-amino-acid parent protein [6]. It is classified as a research compound; it is not approved for human therapeutic use by any regulatory agency.
Is TB-500 safe?
Phase I trials of full-length thymosin beta-4 administered intravenously in healthy human volunteers at doses up to 1,260 mg found no dose-limiting toxicities and mild-to-moderate adverse events [11][12]. These data apply to the full-length protein, not the TB-500 heptapeptide fragment specifically. Long-term human safety data for TB-500 are not available in the published literature.
How does TB-500 work?
TB-500 binds G-actin at the LKKTETQ sequence, sequestering it from polymerization into F-actin. The freed actin dynamics redirect toward cell migration. VEGF and VEGFR2 upregulate, driving angiogenesis; NF-κB nuclear translocation is inhibited, reducing pro-inflammatory cytokines; AKT activates, upregulating Bcl-XL and HIF-1α [6][7][13][17]. The unifying model is actin-directed cell reprogramming from structural to migratory and reparative phenotype.
How long does TB-500 stay in your system?
Human plasma half-life data for the TB-500 heptapeptide are not published. For the full-length thymosin beta-4 IV, half-life was 0.95–2.1 hours in Phase I trials [11][12]. WADA anti-doping detection window is approximately 30–45 days post-administration in urine and blood by LC-MS/MS [1] — this reflects tissue metabolite accumulation, not active plasma half-life.
Can I take TB-500 every day?
Published research protocols describe twice-weekly injections during a loading phase and once-weekly during maintenance. Daily administration protocols have not been evaluated in controlled trials [1]. Animal studies using daily dosing (skin flap models at 2–10 mg/kg/day [20]) address specific vascular endpoints and are not clinical dosing recommendations.
Does TB-500 increase hair growth?
Thymosin beta-4 activates hair follicle stem cells in the bulge region in murine models. Philp et al. (2007) documented that Tβ4 stimulated follicle stem cell migration, MMP-2 upregulation, and accelerated hair regrowth; transgenic overexpressing mice showed faster regrowth than controls [8]. Hair growth is a downstream inference from this thymosin beta-4 research — no human trial has evaluated TB-500 specifically for this indication.
How long should I take TB-500 for?
Published clinical-adjacent protocols reference a four-week loading phase followed by a four-week maintenance phase. No controlled human study has evaluated optimal cycle duration for TB-500. Animal studies use periods ranging from single post-injury doses to multi-week repeated administration depending on the tissue endpoint studied [10][14][20].
How soon does TB-500 start working?
In animal studies, measurable tissue-repair outcomes appear within two to four weeks. Wound reepithelialization differences were significant at days 4 and 7 [2]; ligament histological improvements were documented at four weeks [10]; neurological improvements after TBI were measurable at two to four weeks [14]. Human onset data for TB-500 have not been published.
What is the difference between TB-500 and BPC-157?
TB-500 sequesters G-actin and signals via VEGFR2 upregulation and NF-κB inhibition — more angiogenic and systemic in documented tissue effects [6][7]. BPC-157 modulates nitric oxide synthesis via a distinct VEGFR2-upstream pathway and is more gastroprotective and locally targeted. The two compounds affect overlapping (angiogenesis, cell migration) and non-overlapping biology. No controlled head-to-head comparison study has been published.
Are there any negative side effects of TB-500?
Reported events from animal studies and informal human use include injection-site reactions (redness, swelling), transient fatigue, mild nausea, and dizziness. Phase I IV thymosin beta-4 in humans at doses up to 1,260 mg produced only mild-to-moderate adverse events with no serious adverse events or dose-limiting toxicities [11][12]. A theoretical oncological concern exists due to pro-angiogenic activity, though no carcinogenicity study has demonstrated this risk.
Does TB-500 help the heart?
Multiple animal studies show thymosin beta-4 promotes cardiomyocyte survival, drives epicardial progenitor activation, and reduces infarct size. In mice it was the first molecule identified simultaneously initiating myocardial and vascular regeneration [5]. In a porcine MI model, it improved ejection fraction and reduced infarct size [16]. Clinical application is pre-investigational; human cardiac trials of full-length Tβ4 are listed at ClinicalTrials.gov (NCT04555850).
Is TB-500 a steroid?
No. TB-500 is a synthetic heptapeptide — seven amino acids — structurally and mechanistically unrelated to anabolic-androgenic steroids. It acts on actin dynamics and growth factor signaling, not androgen receptors [6]. Both classes are prohibited by WADA but under different sections (steroids: S1; TB-500: S2).
Is TB-500 FDA approved?
TB-500 is not FDA approved for any human indication. It is classified as a research compound. Full-length thymosin beta-4 has been investigated under FDA IND for cardiac and corneal indications. TB-500 is listed by WADA under S2 (Peptide Hormones, Growth Factors, Related Substances, and Mimetics) and is prohibited at all times in sanctioned sport [1].
Where to inject TB-500?
Research protocols describe both subcutaneous and intramuscular injection sites. Some studies use local injection proximal to the injury site; others use systemic administration. Intraperitoneal injection is used in rodent models; intravenous administration was used in human Phase I trials of full-length Tβ4 [11]. No controlled human study has compared injection sites for the TB-500 heptapeptide specifically.
How much TB-500 should I take?
Published equine and clinical-adjacent protocols describe 2–5 mg per injection for TB-500. Human dosing has not been established in randomized controlled trials. This site does not make dosing recommendations; that is a medical determination requiring consultation with a licensed clinician. What the studies administered to which species at which doses is documented on the TB-500 dosage page.
Can TB-500 be taken orally?
TB-500 is a peptide and is degraded by gastric and pancreatic proteases when taken orally. Published research protocols use parenteral routes exclusively — intraperitoneal (rodents), intravenous (human Phase I), subcutaneous/intramuscular (equine and informal human contexts). No study has demonstrated meaningful oral bioavailability for the Ac-LKKTETQ heptapeptide or the parent thymosin beta-4 protein.
How to reconstitute TB-500?
Laboratory protocols describe reconstituting lyophilized peptide powder with bacteriostatic water using sterile technique. This is a standard peptide-handling procedure. Contamination risk with improperly prepared preparations is a safety consideration noted in the research literature — a procedure-quality concern, not a compound-specific toxicity. Research-grade reconstitution requires standard sterile laboratory technique.
What does TB stand for in TB-500?
TB stands for thymosin beta — TB-500 is the synthetic active-site fragment of thymosin beta-4, a ubiquitous intracellular protein that regulates actin polymerization. The 500 designation identifies the compound as the specific synthetic heptapeptide fragment (Ac-LKKTETQ) of thymosin beta-4 [1].
How does TB-500 compare to thymosin beta-4?
TB-500 is a 7-amino-acid synthetic fragment of the 44-amino-acid thymosin beta-4 protein, spanning the active actin-binding domain (amino acids 17–23). Research indicates the Ac-LKKTETQ fragment retains most of the actin-sequestering and tissue-repair activity of the full-length endogenous protein [6]. Some additional activities of full-length Tβ4 that depend on structural domains outside the 17–23 fragment may not be replicated by TB-500.
What research exists on TB-500 for tendon healing?
Rat medial collateral ligament transection studies show that 1 µg Tβ4 in fibrin sealant applied locally produced significantly superior collagen organization and increased fibril diameters at four weeks compared to controls [10]. Wound healing studies document accelerated fibroblast migration, collagen synthesis, and neovascularization at injury sites across multiple models [2][3][4]. No controlled human tendon trial has been published for TB-500 specifically.
What is the Wolverine Stack?
The Wolverine Stack is a colloquial term for co-administration of TB-500 and BPC-157. The mechanistic rationale: TB-500's actin-sequestering angiogenic activity and BPC-157's nitric-oxide-modulating locally targeted repair activity are proposed to be complementary. No controlled human study has evaluated the combination; the rationale derives from independently published preclinical data on each compound.
How often should TB-500 be administered?
Clinical-adjacent and research reports describe twice-weekly injections during a four-week loading phase, transitioning to once-weekly maintenance injections. This schedule has not been validated in a randomized controlled trial. Daily administration has not been studied in clinical-grade human protocols [1].