TB-500

TB-500 is a synthetic version of Thymosin Beta-4, a naturally occurring 43-amino-acid protein found throughout the human body. Thymosin Beta-4 constitutes 70-80% of all beta-thymosins and plays roles in cell migration, tissue repair, angiogenesis, and inflammation regulation. The key active region is the actin-binding domain (amino acids 17-23), which enables cells to migrate toward injury sites — the foundation of its research interest for recovery applications.

Despite its name suggesting a fragment, most commercial TB-500 products contain the full 43-amino-acid Thymosin Beta-4 sequence. The key active region is the actin-binding domain at amino acids 17-23 (the sequence LKKTETQ), which a 2003 study showed produces comparable wound repair effects to the full-length protein. The published human clinical trials (RGN-259 for dry eye) used pharmaceutical-grade Thymosin Beta-4, not commercial TB-500 — meaning human clinical data technically applies to the regulated form of the protein.

Both are research peptides studied for tissue repair, but through different mechanisms. BPC-157 works through growth hormone receptor upregulation and nitric oxide modulation, while TB-500 promotes repair through actin polymerization and cell migration. BPC-157 has more gastrointestinal evidence; TB-500 has stronger cardiac and hair follicle data. They are commonly combined in the "Wolverine Stack" based on complementary mechanisms, though no published research has tested this combination.

TB-500 is legal to purchase for research purposes in most jurisdictions but is not FDA-approved for human use. The FDA classified it as a Category 2 compound, restricting compounding pharmacies from preparing it. In February 2026, HHS announced plans to potentially reclassify certain peptides including Thymosin Beta-4. TB-500 is prohibited by WADA for athletes and by the DoD for military personnel. Legal status varies by country — check local regulations.

The most commonly reported side effects in community use are headache, fatigue during the loading phase, mild nausea, and lightheadedness after injection. The only published human safety data comes from topical eye drop trials (not injectable) described as safe and well tolerated in 72+ subjects. Long-term safety data for injectable TB-500 does not exist. The theoretical cancer concern from angiogenesis has no supporting human evidence but warrants caution in individuals with active malignancies.

Animal studies show promising results. Thymosin Beta-4 overexpression in transgenic mice led to faster hair re-growth, higher hair shaft counts, and follicle clustering through VEGF-mediated signaling (PMID: 26083021). A 2021 review confirmed that exogenous Tb4 accelerates hair follicle stem cell migration and cycle transitions (PMID: 33393222). However, no human hair growth trials have been published, and community reports of hair effects are mixed and often temporary.

Community-reported protocols typically use a loading phase of 4-8 mg per week split into two subcutaneous injections for 4-6 weeks, followed by maintenance of 2-4 mg every 1-2 weeks. These are not FDA-approved doses — all dosing information comes from community protocols and research contexts. Gradual dose escalation and proper reconstitution with bacteriostatic water are standard practice. Individual responses vary significantly.

Community reports typically describe initial effects within 2-3 weeks of beginning the loading phase, with more noticeable results at 4-6 weeks. The loading phase protocol exists specifically because tissue saturation appears to require consistent dosing before effects become apparent. Results are highly individual and depend on the type and severity of the condition being addressed. No clinical trial data exists to define onset timelines.

The combination of TB-500 and BPC-157, called the "Wolverine Stack" in peptide communities, is one of the most commonly discussed protocols. Both peptides work through different tissue repair mechanisms — TB-500 through actin-mediated cell migration and BPC-157 through growth hormone receptor upregulation and nitric oxide modulation. They are administered as separate injections at their respective standard doses. No published research has studied this combination for safety or efficacy.

Yes. TB-500 is prohibited by the World Anti-Doping Agency (WADA) at all times, classified as a Non-Specified Substance under category S2 (Peptide Hormones, Growth Factors, and Related Substances). First-offense violations carry a four-year ban from competition. USADA follows WADA classifications. The U.S. Department of Defense has also adopted WADA categories, making TB-500 prohibited for all military personnel. Detection methods exist and are actively used in anti-doping testing.

No dedicated TB-500 tendon repair studies exist on PubMed. The evidence for tendon use is extrapolated from general tissue repair mechanisms — specifically, TB-500's ability to promote cell migration, angiogenesis, and anti-inflammatory activity in other tissue types. Veterinary use in horses for tendon and ligament injuries predates the research peptide market, and community reports of tendon improvement are common. However, these remain anecdotal without controlled human trial data.

TB-500 promotes angiogenesis (new blood vessel formation), which theoretically could support tumor growth by supplying blood to existing cancers. This is a mechanistic concern, not an observed clinical outcome — no human cases linking TB-500 to cancer development have been published. The porcine cardiac study (PMID: 34335970) specifically monitored for tumor formation and found none. Individuals with active malignancies should avoid TB-500 as a precaution given the theoretical risk.

The only published human trials used full-length Thymosin Beta-4, not the TB-500 fragment specifically. RegeneRx completed two Phase 2 randomized controlled trials for dry eye disease using RGN-259 (topical 0.1% Thymosin Beta-4 eye drops). Both trials were described as safe and well tolerated, though the second trial's primary endpoints did not reach significance (PMID: 25826322, 26056426). No published human trials exist for injectable TB-500 or for any indication beyond dry eye.

The Wolverine Stack is a community-coined name for the combination of TB-500 and BPC-157, two research peptides studied for tissue repair through complementary mechanisms. The name references the Marvel character's regenerative abilities. Both peptides are administered separately at their standard doses — typically TB-500 at 4-8 mg/week with BPC-157 at 250-500 mcg/day during a loading phase. No published research has validated this combination.

TB-500 is supplied as a lyophilized (freeze-dried) powder that requires reconstitution with bacteriostatic water before injection. Add the water slowly along the inside wall of the vial — do not inject directly onto the powder or shake vigorously, as this can damage the peptide. Swirl gently until fully dissolved. Store the reconstituted solution refrigerated at 2-8 degrees Celsius and use within 3-4 weeks. Use an alcohol swab on vial tops before each draw.

TB-500 is a peptide that would be largely broken down by digestive enzymes if taken orally, significantly reducing bioavailability. The standard administration route is subcutaneous injection. The published human clinical trials for Thymosin Beta-4 used topical eye drops (not oral or injectable). Some vendors market oral or sublingual TB-500 products, but no published data supports oral bioavailability for this peptide.

Cardiac repair is the most researched preclinical application for Thymosin Beta-4, with multiple animal studies showing protection after myocardial infarction — reduced infarct size, improved ventricular function, and new blood vessel formation (PMID: 34335970, 35712678). RegeneRx planned Phase 2 cardiac trials in STEMI patients but results were never published. No published human cardiac data exists. TB-500 should not be used as a substitute for evidence-based cardiac treatment.

A 2024 study (PMID: 38382158) found that when TB-500 is metabolized in the body, it breaks down into several fragments. Only one of these fragments — Ac-LKKTE — showed significant wound repair activity in laboratory testing. The parent TB-500 molecule itself did not show this activity. This suggests that TB-500's previously reported tissue repair effects may actually be produced by this metabolite rather than the intact peptide, potentially reframing how researchers understand the compound's mechanism.