TB-500

TB-500 is the synthetic N-acetylated 17-23 fragment of thymosin beta-4, a 43-amino-acid peptide first isolated from calf thymus and chemically characterized in the early 1980s ¹¹. The fragment contains the sequence LKKTETQ, the core actin-binding region mapped on the parent peptide ¹.

Most direct evidence for TB-500 is preclinical. A scoping review of 80 thymosin beta-4 and TB-500 studies found direct TB-500 evidence restricted to a single rat Achilles tendon study ⁸. No human RCTs of TB-500 exist for any indication ¹⁰. Human clinical data are concentrated in the parent peptide thymosin beta-4, including a 96-patient trial in ST-elevation myocardial infarction and late-stage ophthalmic trials ²⁵.

Products marketed as TB-500 are frequently misbranded or adulterated, so identity and purity are not guaranteed from a label ³.

TB-500 contains LKKTET, the principal actin-contact site of thymosin beta-4 ⁵. By binding monomeric actin (G-actin), the peptide buffers the pool available for filament assembly, and this actin regulation enables directional migration of fibroblasts, keratinocytes, and endothelial cells ⁶.

Migration and remodeling

Matrix metalloproteinases are required for this effect. Thymosin beta-4 upregulates MMP-1 in wounded corneal epithelium, and blocking MMPs abolishes the peptide-stimulated migration ³⁰. Downstream of actin buffering, the peptide class is reviewed as driving cell migration, blood vessel growth (angiogenesis), inflammation resolution, and extracellular matrix remodeling ⁶.

Downstream pathways

The parent peptide activates cell-survival signaling through Akt, Bcl-2, and caspase-3 in injured hearts ¹². It also suppresses NF-kB-driven gene expression and reduces inflammatory cytokines such as IL-6 and IL-1β in sepsis models ³¹. In coronary injury, thymosin beta-4 converts adult epicardium-derived progenitor cells into vascular cells, promoting neovascularization ³⁶.

What is not established

TB-500 lacks the N-terminal Ac-SDKP sequence of full-length thymosin beta-4, so antifibrotic effects reported for the whole peptide do not automatically transfer to TB-500 ⁹. Whether the isolated fragment recapitulates the angiogenic, anti-apoptotic, and anti-fibrotic activities of full-length thymosin beta-4 is unresolved ¹.

Direct evidence for TB-500 is limited, and most human-use claims are extrapolated from the parent peptide thymosin beta-4 ⁹.

Animal evidence

• Achilles tendon repair: In a rat tendon transection model, TB-500 at 60 µg/kg per day intraperitoneally for 4 weeks produced significantly higher maximum load to failure and better histology scores, with improved type I collagen organization ¹⁸. This is the only direct musculoskeletal efficacy study identified in an 80-study scoping review ⁸.
• Neuroinflammation: In 5×FAD Alzheimer's disease mice, TB500 with Ac-SDKP improved maze and object-recognition performance, reduced glial activation and neuronal apoptosis, and restored perirhinal axon density without reducing amyloid plaque burden ¹⁹.
• Corneal repair: An enzyme-responsive hydrogel loaded with TB500 promoted human corneal epithelial cell migration and tight-junction recovery in vitro, and accelerated epithelial regeneration in a murine alkali-burn model ².

Parent peptide data

A randomized trial of recombinant human thymosin beta-4 in 96 STEMI patients showed no significant overall infarct-size reduction, but a significant reduction in the subgroup dosed within 8 hours of reperfusion ²⁵. No TB-500-specific human musculoskeletal benefit has been documented ¹⁰.

There are no human RCTs of TB-500, and no dose-finding or route-comparison studies have been published ⁸. Published dosing patterns are therefore dominated by animal models and community-derived injectable regimens.

Published animal protocol

• Rat Achilles tendon transection: 60 µg/kg per day by intraperitoneal injection for 4 weeks improved biomechanical strength and collagen organization ¹⁸.

Parent peptide human anchor

A randomized, double-blind trial of recombinant human thymosin beta-4 in 96 STEMI patients used an intravenous first dose within 8 hours of PCI, with reduced infarct area observed in the early-treated subgroup ²⁵. This is the parent peptide, not TB-500.

Community injectable patterns

The most-used community regimen for soft-tissue injury is 2.0-2.5 mg subcutaneously twice weekly for 4-8 weeks, sometimes followed by weekly or fortnightly maintenance ⁸. Practitioner-circulated acute courses may start higher and taper, but all human TB-500 dosing remains extrapolation without clinical validation ²³.

TB-500 is a water-soluble peptide fragment, and community protocols use bacteriostatic water as the diluent ⁶. Handling should be gentle: let the powder dissolve without vigorous shaking, and use sterile technique.

Analytical stability data show TB-500 degrades completely in serum within one week at 4°C or 22°C, but remains detectable for at least 2 months at -20°C and in dried matrices at ambient temperature ²⁰. Therefore lyophilized powder should be stored frozen, and reconstituted solution refrigerated at 2-8°C with minimal time at room temperature. Community guidance recommends using reconstituted vials within 14 days and avoiding repeated freeze-thaw cycles ²⁰.

Products labeled TB-500 have been documented as misbranded or adulterated, so product identity should be confirmed before preparation ³. The interactive calculator in this section handles dilution math, rather than stating specific volumes and concentrations here.

No formal drug-drug interaction studies exist for TB-500, so assessments below are extrapolated from the parent peptide thymosin beta-4 ⁹.

Drug interactions

• Anticoagulants and antiplatelets: Thymosin beta-4 inhibits extrinsic coagulation triggering in rats and is released from activated platelets, so additive hypocoagulability is a theoretical concern ⁴⁴.
• Taxanes: Thymosin beta-4 overexpression activates ERK and induces paclitaxel resistance in cell lines ⁵¹.
• Anti-VEGF biologics: TB-500 and thymosin beta-4 are pro-angiogenic, so combined use with bevacizumab or similar agents is mechanistically opposed in oncology ⁶.
• Fluoroquinolones, ocular: Adjunctive thymosin beta-4 with ciprofloxacin improved corneal nerve regeneration and visual function in P. aeruginosa keratitis in mice ⁴⁷.
• MAPK-modulating drugs: Thymosin beta-4 suppresses JNK1/2, p38, and ERK1/2 phosphorylation in LPS-induced acute kidney injury, so co-use with BRAF/MEK inhibitors may blunt or amplify their effects ³².

Supplement interactions

• High-dose zinc: Thymosin beta-4 binds zinc and undergoes low-solubility aggregation at physiological pH; avoiding high-dose zinc during a cycle and separating dosing by at least 2 hours is common practitioner guidance ⁴².
• Fish oil, ginkgo, high-dose vitamin E, garlic: Their antiplatelet activity could stack with thymosin beta-4's platelet and coagulation involvement ⁴⁴.
• Copper (GHK-Cu): Copper-peptide coordination differs from zinc aggregation, and this combination is a common healing stack without direct interaction data ⁴².

No human RCT establishes a TB-500 cycle, and the only controlled weight-scaled data are from a 4-week rat tendon study ¹⁸. Community protocols commonly run 4-8 week cycles with twice-weekly dosing, followed by off-periods of at least 4 weeks; some practitioners use time off equal to time on ⁸.

Pulsed dosing fits the available pharmacology. A short 7-day course of the parent peptide prevented cardiac dysfunction at 28 days in mice, and early dosing within 8 hours of PCI was associated with smaller infarct area at 90 days ²⁵. This durability supports the assumption that brief exposures can produce structural effects that outlast drug clearance, although this has not been tested for TB-500 in humans.

There are no reported tolerance, rebound, or withdrawal phenomena for TB-500. Effect plateau after roughly 2 weeks without further improvement is the main practical signal used to decide when to stop a cycle, rather than any established biological endpoint ¹⁸.

TB-500 is often discussed in combination with other healing peptides, but direct combination data are sparse.

BPC-157

In the rat Achilles transection model, TB-500 60 µg/kg/day combined with BPC-157 10 µg/kg/day produced no additive benefit over TB-500 alone, suggesting convergence on shared downstream pathways ¹⁸. Mechanistically BPC-157 acts mainly through angiogenesis, while TB-500 and thymosin beta-4 act through actin regulation and cell migration ⁹.

GHK-Cu and KPV

GHK-Cu targets fibroblast migration and extracellular matrix remodeling, overlapping TB-500's mechanism, and is a common community stack without direct interaction data ⁹. KPV also shares anti-inflammatory signaling through NF-kB ⁹.

Growth hormone secretagogues

CJC-1295, ipamorelin, and similar peptides operate through the growth hormone axis, distinct from TB-500's actin and angiogenic pathways, so they are sometimes combined, but no interaction data exist ¹⁴.

TB-500 is not FDA-approved for any indication, and it lacks marketing authorization in the EU, UK, and Australia ¹⁰. It is characterized as an unapproved, experimental peptide worldwide ¹.

The World Anti-Doping Agency prohibits TB-500 under Class S0, which covers substances with no governmental approval for human therapeutic use ¹⁴. Detection methods are operational in human and equine anti-doping laboratories, with limits of detection of 0.05-1.25 ng/mL in blood matrices ²⁰. The N-terminal metabolite Ac-Tβ(1-14) has been characterized as a urinary biomarker of Tβ4-family administration ²¹. Equine anti-doping programs have applied TB-500 testing since 2012 ¹³.

Analytical work has documented misbranded and adulterated products sold as TB-500, adding regulatory and safety risk beyond the unapproved status itself ³.

No systematically collected human adverse-event database exists for TB-500 ⁴. The profile below triangulates parent peptide data, animal tolerability, and community reports.

Common community-reported effects

Injection-site redness, stinging, mild itching, transient fatigue for 1-4 hours after injection, headache, and flushing are reported in community use. Mechanistic support exists for histamine-type reactions, because thymosin beta-4 and derived peptides directly induce mast cell granule release in vitro ⁴⁶.

Rare or theoretical risks

• Tumor progression: Thymosin beta-4 promotes breast cancer proliferation, migration, and blood vessel growth, and inhibits apoptosis and ferroptosis via SLC7A11 ²⁸. Fragment-level tumorigenicity is unstudied ⁴.
• Pathological angiogenesis: Pro-angiogenic activity is flagged as a hazard of unapproved injectable peptide use ⁴.
• Bleeding: Thymosin beta-4 inhibits extrinsic coagulation pathway triggering in rats and is involved in platelet aggregation ⁴⁴.
• Zinc aggregation: Thymosin beta-4 forms low-solubility zinc adducts, though this is likely only in zinc-rich microdomains ⁴².

Contraindications from the literature

Theoretical concerns support avoidance with active cancer, bleeding disorders, the perioperative window, proliferative retinal disease, and pregnancy ⁴. Competitive athletes are absolutely prohibited from use under WADA rules independent of health effects ⁵.