TB-500 / Thymosin Beta-4
TB-500 is used as a systemic tissue-repair peptide, marketed for tendon, ligament, and muscle recovery in injury and post-training protocols. It's derived from thymosin beta-4, a natural protein the body uses to help cells migrate to a wound and rebuild damaged tissue. It's frequently paired with BPC-157 in recovery stacks aimed at faster return-to-training after soft-tissue injury.
$75 / 10 mg vial
Dosing
TB-500 fragment, published human dose – No citable dose
No citable figure. No published human trial has established a dose of TB-500 for any indication. The first human trial of TB-500 itself was only recruiting as of 2026, with dosing not yet public.
Community reported
| Timeframe | Dosage | Frequency | Note |
|---|---|---|---|
| Weeks 1-2 | 500 mcg | once daily | Starting dose1 |
| Weeks 3-4 | 600 mcg | once daily | |
| Weeks 5-8 | 750 mcg | once daily | |
| Weeks 9-12 | 1,000 mcg (1.0 mg) | once daily | Maintenance ceiling2 |
- Cycle length 8-12 weeks, extendable to 16. TB-500 is a synthetic fragment/analog of full-length Thymosin Beta-4, not simply an abbreviation for it; if the storefront SKU is full-length Thymosin Beta-4 rather than the TB-500 fragment, this schedule should not be assumed to transfer directly.
- Community discussion pairs TB-500 almost exclusively with BPC-157 as a combined stack rather than discussing it standalone.
Batches on hand
Availability
30 vials on hand.
MKM-TB10-26072630 vials
Full research
Evidence tier
TB-500 (short fragment, as commercially sold): Anecdotal, no controlled dataThymosin Beta-4 (full-length, distinct from TB-500): Human trials, not approved for this use
TB-500 (short fragment, as commercially sold): TB-500 itself has zero completed human trials. The first TB-500-specific human study (TBRIDGE-CV, NCT07487363) began recruiting only in February 2026, with no results yet, and its marketed healing claims are extrapolated from the pharmacologically related but distinct, larger full-length thymosin beta-4 molecule.
Thymosin Beta-4 (full-length, distinct from TB-500): Completed human Phase III RCT data exists for a topical ophthalmic indication (RGN-259, neurotrophic keratopathy) and Phase 1 safety data exists for an intravenous cardiac formulation (RGN-352), but neither trial supports the soft-tissue-recovery use TB-500 is marketed for, and full-length thymosin beta-4 holds no regulatory approval anywhere.
Original dosing schedule
The Dosing table above this section now shows a community- or vendor-sourced schedule (peptidedosages.com). The regulatory-label or clinical-trial dosing this entry was originally built on is kept here, unchanged, rather than removed.
Clinical trial
| Timeframe | Dosage | Frequency | Note |
|---|---|---|---|
| Ongoing | 0.1% solution | five times daily | Different molecule1 |
- TB-500 is a synthetic fragment/analog of full-length Thymosin Beta-4, not simply an abbreviation for the same molecule; this dosing does not transfer directly to a TB-500 fragment product.
Clinical trial
| Timeframe | Dosage | Frequency | Note |
|---|---|---|---|
| Trial design | 450-1200 mg | dosing-design range | Program halted1 |
- This program did not proceed to completion.
Identity
| Full name | TB-500 (Ac-LKKTETQ fragment) and full-length Thymosin Beta-4 (T-beta-4) |
|---|---|
| Class | Actin-binding synthetic peptide fragment (TB-500) and the naturally occurring, highly conserved intracellular actin-sequestering protein it is derived from (thymosin beta-4) |
| Sequence | Full-length thymosin beta-4: a 43-amino-acid protein, molecular weight approximately 4,921 Da, present in nearly all mammalian cell types except mature red blood cells. TB-500, as commercially sold: Ac-LKKTETQ, an acetylated heptapeptide corresponding to residues 17-23 of thymosin beta-4, the historically identified actin-binding motif region. |
Mechanism of action
Plain language
Thymosin beta-4's core, best-established job inside cells is to bind and hold in reserve the building-block protein actin, controlling how and when cells build and dismantle their internal skeleton, which governs cell movement such as skin cells migrating to close a wound or immune cells migrating to a repair site. TB-500 is intended to mimic a piece of that activity.
Technical
Thymosin beta-4's primary, best-characterized biochemical function is sequestration of monomeric G-actin, preventing its polymerization into filamentous F-actin, by steric occlusion and by inhibiting nucleotide exchange on the actin monomer, until a cellular signal triggers release. The LKKTET motif at residues 17-22, the basis of TB-500, was historically identified as the principal actin-binding motif, though crystallographic work indicates essentially the full length of the thymosin beta-4 sequence participates in the actin interface, meaning the short fragment may not fully replicate full-length activity. Full-length thymosin beta-4 additionally has documented roles in keratinocyte migration, angiogenesis, and anti-inflammatory signaling in animal and in-vitro wound-healing models. Whether TB-500, the isolated 7-residue fragment, reproduces these full-length effects in humans is proposed by extrapolation, not established directly, since TB-500 itself has essentially no human data.
Sources: Thevis M, et, Thymosin Beta-4 and, 2026
Why: Fragment lacks human data
TB-500, the short Ac-LKKTETQ fragment actually sold, has zero completed human clinical trials. The first TB-500-specific human study began recruiting only in February 2026, and no results exist yet.
Sources: ClinicalTrials.gov NCT07487363, TB-500, 2026
Why: Evidence from wrong molecule
Most of the healing literature vendors cite for TB-500 was actually generated using the distinct, 43-amino-acid full-length thymosin beta-4, not the short marketed fragment. Crystallographic work indicates the full-length sequence participates in the actin interface, so the fragment may not fully replicate full-length activity.
Sources: Thymosin Beta-4 and, 2026
Why: Full-length data, different use
Full-length thymosin beta-4 does have real human trial data, a Phase III topical ophthalmic trial and a Phase 1 intravenous cardiac safety trial, but neither indication is the injectable soft-tissue recovery use TB-500 is marketed for today.
Sources: Cao Y, et, 2022, ClinicalTrials.gov NCT01311518, A, 2011
What it’s used for
Human trials, not approved for this use
- Topical ophthalmic full-length thymosin beta-4 (RGN-259, 0.1% solution, five times daily) was tested in a randomized, placebo-controlled, double-masked Phase III trial (SEER-1) in 18 subjects with neurotrophic keratopathy. Complete corneal healing at 4 weeks occurred in 6 of 10 treated versus 1 of 8 placebo subjects, with the healing advantage remaining significant two weeks after treatment stopped. This is human RCT-tier evidence, but for a topical ophthalmic formulation unrelated to injectable soft-tissue recovery.
Sources: Cao Y, et, 2022
- Injectable full-length thymosin beta-4 (RGN-352) completed a Phase 1 safety and tolerability trial in humans and was reported safe and well tolerated. A planned Phase 2 trial in acute myocardial infarction patients, at doses of 1,200 mg or 450 mg intravenously, was placed on clinical hold in 2011 due to a contract manufacturer's manufacturing-compliance issue, and the intravenous cardiac program did not proceed to completion.
Off-label / community use
- TB-500 is widely used off-label in fitness, veterinary, and injury-recovery communities, often alongside BPC-157, for tendon, ligament, and muscle injury and general recovery. This use rests on extrapolation from full-length thymosin beta-4 animal and limited human data to a different molecule, the short fragment, that itself has no human trial data.
Sources: Thymosin Beta-4 and, 2026
Pharmacokinetics
| TB-500 (short fragment), human pharmacokinetics |
Not established No citable figure. No published human pharmacokinetic data exist for TB-500. Route, half-life, time to peak, and duration of effect in humans for the injectable recovery use case are unknown and unpublished. |
|---|---|
| Full-length thymosin beta-4, intravenous (RGN-352) |
Clinical trial Phase 1 human safety and tolerability data exist; no detailed public pharmacokinetic profile has been identified in available sources. |
Reconstitution
| Vial strength | Most commonly 5 mg or 2 mg lyophilized powder per vial |
|---|---|
| Diluent | Bacteriostatic water |
| Diluent volume | 1 mL or 2 mL for a 5 mg vial; 1 mL or 2 mL for a 2 mg vial, per vendor convention |
| Concentration | 5 mg vial with 1 mL yields 5 mg/mL; with 2 mL yields 2.5 mg/mL. 2 mg vial with 2 mL yields 1 mg/mL; with 1 mL yields 2 mg/mL. |
Worked example
On a U-100 insulin syringe at 5 mg/mL, 1 unit delivers approximately 50 mcg.
Sources: Multiple commercial vendor
Dose calculator
Enter a vial strength, diluent volume, and desired dose to see the resulting concentration, dose volume, and units on a standard U-100 insulin syringe. Nothing entered here is saved, stored, or sent anywhere – the calculation runs only in your browser.
Enable JavaScript to use the interactive calculator. The worked example above already shows a complete calculation for this compound.
Storage and post-reconstitution stability
Unopened storage
Lyophilized material is generally stored refrigerated or frozen and protected from light per standard peptide-handling convention; no published cGMP stability study for either TB-500 or injectable thymosin beta-4 outside pharmaceutical trial material has been identified.
Post-reconstitution stability – Vendor claim
Approximately 30 days refrigerated with bacteriostatic water; approximately 72 hours with plain sterile water. 2-8C
No citable figure. These figures come from vendor guidance, not a published stability study, and should be treated as unverified.
Safety
Notable risks
- No controlled human safety data exist for TB-500 specifically. For full-length thymosin beta-4, the topical ophthalmic RGN-259 Phase III trial reported 16 total adverse events across 18 subjects, only one considered treatment-related, with no serious treatment-related events and no withdrawals due to adverse events. The RGN-352 intravenous Phase 1 program reported the drug as safe and well tolerated, though it did not proceed to a completed Phase 2 efficacy readout.
Sources: Cao Y, et, 2022, ClinicalTrials.gov NCT01311518, A, 2011
- Thymosin beta-4 overexpression has been reported to promote tumor growth, invasion, and metastasis in several cancer cell-line and animal models via VEGF-mediated angiogenesis, with one study reporting a 4.4-fold increase in tumor blood-vessel density and a 2.3-fold increase in melanoma cell migration. This effect appears context-dependent: one study reported thymosin beta-4 downregulation, rather than upregulation, associated with worse prognosis in multiple myeloma. No human clinical trial has established or excluded a causal link between exogenous TB-500 or thymosin beta-4 administration and human cancer risk; this is a theoretical, mechanism-derived concern, not an observed clinical adverse event.
- TB-500 is sold as an unregulated research chemical of uncertain and sometimes misrepresented molecular identity. Materials sold as TB-500 have historically been marketed and described inconsistently, sometimes as the short fragment and sometimes conflated with the full-length protein, so buyers cannot assume which molecule is actually in a given vial without independent laboratory analysis.
Sources: BSCG (Banned Substances, Thevis M, et
Sources
- BSCG (Banned Substances Control Group, a commercially operated supplement-testing and certification company). TB-500 – Status, Risks, and Bans in Sport and Military
- Thevis M, et al. Synthesis and characterization of the N-terminal acetylated 17-23 fragment of thymosin beta 4 identified in TB-500, a product suspected to possess doping potential
- Thymosin Beta-4 and TB-500 in Tissue Healing, Regeneration, and Musculoskeletal Repair: A Scoping Review. Applied Sciences (MDPI) (2026)
- Cao Y, et al. 0.1% RGN-259 (Thymosin ss4) Ophthalmic Solution Promotes Healing and Improves Comfort in Neurotrophic Keratopathy Patients in a Randomized, Placebo-Controlled, Double-Masked Phase III Clinical Trial. Int J Mol Sci (2022)
- ClinicalTrials.gov NCT01311518, A Study of the Safety and Efficacy of Injectable Thymosin Beta 4 for Treating Acute Myocardial Infarction; FierceBiotech, RegeneRx Phase 2 AMI Trial on Clinical Hold Due to GMP Compliance Issues at Contract Manufacturer, 2011 (2011)
- ClinicalTrials.gov NCT07487363, TB-500 (Thymosin Beta 4 17-23 Fragment) for Cardiovascular Biomarkers in Stable ASCVD (TBRIDGE-CV) (2026)
- Cha HJ, Jeong MJ, Kleinman HK. Role of Thymosin Beta4 in Tumor Metastasis and Angiogenesis. J Natl Cancer Inst (2003)
- Haematologica. Thymosin ss4 has tumor suppressive effects and its decreased expression results in poor prognosis and decreased survival in multiple myeloma
- Multiple commercial vendor and dosing-guide pages (e.g. swolverine.com, tb500.org, pathtopeptides.com, peptitools.com, elementsarms.com), cited only to describe commercially sold vial strengths and vendor-stated reconstitution and dosing convention, not as evidence for any efficacy or safety claim
- peptidedosages.com, TB-500 5 mg vial dosage protocol
This is a research and educational reference, not medical advice. Nothing on this site is a recommendation to use any compound.