TB-500 / Thymosin Beta-4
TB-500 is the peptide people reach for when an injury needs systemic help, not just a local fix, and it is usually run alongside BPC-157 rather than alone. It is built to help cells migrate to damaged tissue and rebuild it, the same job its parent protein does throughout the body. Athletes and lifters run it for tendon, ligament, and muscle injuries that have stopped healing on their own, generally as part of a broader recovery stack. Dosing follows a daily injection schedule that steps up over several weeks.
What it does
Injuries that stopped healing
The same injuries that do not respond to rest are usually why people start TB-500: old tendon and ligament damage, tears that scarred over wrong the first time, muscle strains that plateaued. It is meant to help cells travel to the injury site and rebuild what is there, the same job its parent protein performs throughout the body. People typically run it daily by injection for several weeks, stepping the dose up gradually, often paired with BPC-157 for a broader effect. The molecule actually sold as TB-500 has no completed human trials behind it.
Sources: Thymosin Beta-4 and, 2026, peptidedosages.com, TB-500 5
Paired with BPC-157
Most people do not run TB-500 alone; it gets stacked with BPC-157 because the two are believed to work through different mechanisms toward the same goal, getting a stalled injury moving again, and that combination shows up constantly in shared recovery protocols. Both run on daily injection schedules that step up over the first several weeks, adjusted together as recovery progresses. Stacking logic aside, TB-500 is sold as an unregulated research chemical, and what is actually in a given vial has not been independently verified.
Sources: Thymosin Beta-4 and, 2026, BSCG (Banned Substances, Thevis M, et al.
Related human trial data
The protein TB-500 comes from does have real human trial results, just not for the injury recovery it is marketed for. A topical eye-drop version of the full-length protein completed a Phase III trial for a corneal-healing condition and beat placebo on complete healing at four weeks. An injectable version of the same protein was tested for safety in a small heart-attack study and came back well tolerated, before the program was shelved. Neither trial used TB-500, the short fragment actually sold for recovery, so neither result transfers to what is in the vial.
Sources: Sosne G, et al., 2022, ClinicalTrials.gov NCT01311518, A, 2011, ClinicalTrials.gov NCT07487363, TB-500, 2026
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 reportedCommunity subcutaneous or intramuscular titration (peptidedosages.com)500 mcg to 1,000 mcg (1.0 mg), once daily
| 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.
Primary structure
AcLLeuKLysKLysTThrEGluTThrQGln
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 al., Thymosin Beta-4 and, 2026
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: Sosne G, et al., 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. |
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.
This calculator needs JavaScript. The arithmetic it runs is: concentration = vial strength in mg divided by diluent volume in mL; dose volume in mL = dose in mg divided by concentration; units on a U-100 syringe = dose volume in mL times 100.
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: Sosne G, et al., 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 al.
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)
- Sosne G, 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.