Section 01
What it's used for
Faster wound healing in animals
In animal studies, TB-500 sped up healing of skin wounds, corneal injuries and burns, helping skin cells migrate, boosting collagen buildup, and growing new blood vessels in the wound. Closure was 30-50% faster than in untreated animals.
▸Clinical wording
Extensive preclinical research demonstrates TB-500 accelerates healing in skin wounds, corneal injuries, and burns. It promotes keratinocyte and fibroblast migration, increases collagen deposition, and enhances angiogenesis in wound beds. Studies show 30-50% faster wound closure rates in animal models with topical or systemic TB-500 administration.
Animal heart data, thin human data
In animal heart-attack models, thymosin beta-4 helped heart cells survive and repair, but a 35-50% damage-reduction claim is unsupported. In humans, only safety trials exist, plus one small trial using pre-treated cells, not TB-500 itself.
▸Clinical wording
In animal models of ischemia/reperfusion injury, thymosin beta-4 activates integrin-linked kinase and supports cardiac cell migration, survival, and repair, but a specific 35-50% infarct-size reduction figure is not supported by the cited literature. In humans, completed studies are limited to Phase I safety trials in healthy volunteers and one small pilot randomized trial using autologous endothelial progenitor cells pre-treated with thymosin beta-4 -- a different intervention from direct TB-500 dosing -- in ST-elevation MI patients. No trial has directly dosed acute MI patients with TB-500 itself, so describing "Phase 1/2 clinical trials for acute myocardial infarction recovery" overstates the current human evidence.
Muscle-cell data only, not tendons
In an animal model, thymosin beta-4 released after muscle injury attracts cells that rebuild muscle. No study covers tendon or ligament healing, and no peer-reviewed horse study exists — claims about equine tendon repair are unsupported.
▸Clinical wording
In an animal model of muscle injury, thymosin beta-4 released after injury acts as a chemoattractant for myoblasts, supporting a role in muscle repair at the cellular level. No published study was found on tendon or ligament healing, collagen organization in tendons, or reduced fibrotic scarring, and no peer-reviewed veterinary or equine study exists in the literature; claims about equine sports medicine use and tendon or ligament repair are not supported by any publication found.
Brain-repair signals in animal studies
In preclinical animal studies, TB-500 encouraged brain stem cells to migrate, nerve fibers to regrow, and protective nerve coatings to rebuild after brain injury and stroke, while reducing brain swelling, inflammation and cell death.
▸Clinical wording
Preclinical studies show TB-500 promotes neural stem cell migration, axonal regrowth, and remyelination following traumatic brain injury and stroke. It reduces brain edema, inflammation, and apoptosis while enhancing functional neurological recovery.
Eye-drop healing in animal models
In animal models, TB-500 eye drops sped up healing of the cornea's surface layer and reduced inflammation and abnormal new blood vessel growth in the eye. The drops also showed benefit in animal models of dry eye disease.
▸Clinical wording
TB-500 accelerates corneal epithelial wound healing and reduces corneal inflammation and neovascularization. Eye drop formulations have shown efficacy in preclinical models of corneal injury and dry eye disease.
Hair regrowth signals in mice
In mouse studies, TB-500 activated and moved hair-follicle stem cells housed in a region called the bulge, and this was linked to enhanced hair regrowth. These findings come from preclinical mouse research, not human trials.
▸Clinical wording
Research suggests TB-500 promotes hair follicle stem cell migration and activation, with preclinical studies showing enhanced hair regrowth in mouse models through activation of follicular stem cells in the bulge region.
Section 02
Mechanism of Action
Keeping building blocks ready for repair
- The peptide binds single actin units, the building blocks of a cell's internal scaffolding.
- Holding a ready pool of those units lets a cell rebuild its shape quickly.
- That flexibility underlies cell movement, cell division and the shape changes of tissue repair.
▸Clinical wording
Actin Sequestration and Cytoskeletal Regulation
TB-500's primary molecular function is sequestering G-actin (monomeric actin) to regulate cytoskeletal dynamics. By binding G-actin through the LKKTETQ motif, TB-500 maintains the pool of available actin monomers, enabling rapid cytoskeletal reorganization essential for cell migration, division, and morphological changes during tissue repair.
Helping cells crawl into a wound
- The peptide adds scaffolding at the leading edge of a moving cell.
- It switches on a branching complex (Arp2/3) that builds the cell's crawling projections.
- Faster movement of vessel-lining, skin and connective-tissue cells is described as critical for wound healing.
▸Clinical wording
Cell Migration Promotion
TB-500 upregulates cell migration by promoting actin polymerization at the leading edge of migrating cells. It activates Arp2/3 complex-mediated actin branching, enabling formation of lamellipodia and filopodia. This migration-promoting effect is critical for wound healing, as it accelerates the movement of endothelial cells, keratinocytes, and fibroblasts into damaged tissue.
Growing new blood vessels in tissue
- The peptide pushes vessel-lining cells to migrate and to form new tubes and sprouts.
- It raises a vessel-growth signal (VEGF) and switches on the Ang1/Tie2 pathway.
- New vessels carry oxygen and nutrients to tissue that is repairing itself.
▸Clinical wording
Angiogenesis and Vascularization
TB-500 is a potent promoter of angiogenesis — the formation of new blood vessels from existing vasculature. It stimulates endothelial cell migration, tubule formation, and vascular sprouting through upregulation of VEGF expression and activation of the Ang1/Tie2 signaling pathway. This angiogenic activity is fundamental to tissue repair, providing oxygen and nutrients to healing tissues.
Turning down several inflammation signals
- It lowers three main alarm messengers of inflammation (TNF-α, IL-1β, IL-6).
- It stops a master inflammation switch (NF-κB) from moving into the cell nucleus.
- It shifts clean-up cells (macrophages) toward their tissue-repair mode rather than their attack mode.
- Fewer fast-response white blood cells (neutrophils) enter the tissue, and oxidative stress falls.
▸Clinical wording
Anti-inflammatory Effects
TB-500 reduces inflammation through multiple mechanisms: downregulation of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6), inhibition of NF-κB nuclear translocation, and promotion of anti-inflammatory M2 macrophage polarization. It also reduces neutrophil infiltration and oxidative stress in damaged tissues.
Protecting heart cells after blood-supply injury
- In heart tissue it switches on a survival kinase (Akt) inside muscle cells.
- That signal keeps heart muscle cells alive and blocks their programmed self-destruction after ischemic injury.
- It also activates the heart's own progenitor cells and pushes them to specialise.
▸Clinical wording
Cardiac Repair and Protection
In cardiac tissue, TB-500 activates Akt/protein kinase B signaling, promoting cardiomyocyte survival and inhibiting apoptosis following ischemic injury. It also activates resident cardiac progenitor cells and promotes their differentiation, contributing to myocardial regeneration.
Section 03
Biological Pathways
- Actin Sequestration & MotilityTB-500 binds G-actin via its LKKTETQ motif, keeping monomers available for reorganization, and drives Arp2/3-mediated actin branching that speeds endothelial, keratinocyte, and fibroblast migration into wounds.
- PI3K/Akt/mTOR Survival SignalingTB-500 activates PI3K/Akt, phosphorylating mTOR, GSK-3β, and Bad to promote survival and the protein synthesis needed for repair; in cardiac tissue this is the primary cardioprotective mechanism.
- VEGF/Ang1 Angiogenic PathwayAngiogenesis is driven by dual upregulation of VEGF, which promotes endothelial proliferation and vessel sprouting, and Ang1/Tie2 signaling, which stabilizes and matures the new vessels.
- NF-κB Inflammatory RegulationTB-500 inhibits IκB kinase, blocking NF-κB nuclear translocation and downregulating TNF-α, IL-1β, and IL-6; it also promotes anti-inflammatory M2 macrophage polarization.
Section 04
Dosage Information
Ac-SDKPDMAEIEKFDKSKLKKTETQEKNPLPSKETIEQEKQAGES| Route / system | Context | Range studied | Limitation |
|---|---|---|---|
| Subcutaneous — self-administration | Vendor protocols, outside any trial | 2–5 mg twice weekly for 4–6 weeks, then 2–2.5 mg weekly or every two weeks — about 22–71 µg/kg per injection for a 70–90 kg adult | Practice, not a finding: no controlled human trial of TB-500 exists for any use, and the numbers come from sellers copying each other. |
| Subcutaneous or intramuscular — horses | Equine sports medicine; unapproved and banned in sport | 5–20 mg per dose, twice weekly for four weeks, then weekly for 8–12 weeks — about 10–40 µg/kg for a 500 kg horse | A vet's judgement, not a study: the schedule was never tested and the product is not approved for animals. A horse dose does not transfer to a person. |
| Into the abdomen or by mouth — rats | Rat stroke and kidney models, whole thymosin β4 | 6 mg/kg into the abdomen every third day; 1 and 5 mg/kg a day by stomach tube — 6 mg/kg is 420–540 mg for a 70–90 kg adult | They gave the whole 43-amino-acid protein, not the seven-amino-acid fragment sold as TB-500, by routes nobody uses. No human conversion was published. |
| Intravenous — a different molecule | Phase 1 in healthy people, whole thymosin β4 | 42, 140, 420 and 1260 mg — one dose, then daily for 14 days; roughly 0.5–18 mg/kg for a 70–90 kg adult | The safety record quoted for TB-500 belongs to the whole protein, given another way in amounts hundreds of times larger. Not to the fragment. |
Results
Syringe Fill Level (100u syringe)
Set positive values for: Recommended dose per kg.
Research Use Only. This information is for educational and research purposes only. Not intended for medical advice or self-medication.
Section 05
Protocols
- Protocol 01
Wolverine Stack - Injury Recovery
The most popular healing stack combining BPC-157 and TB-500 for comprehensive tissue repair. Ideal for tendon, ligament, and muscle injuries.
- Focus
- Healing & Recovery
- Level
- Intermediate
- Duration
- 4–8 weeks
- Protocol 02
Joint & Cartilage Recovery
Protocol combining BPC-157, TB-500, and collagen for joint pain, osteoarthritis, and cartilage repair.
- Focus
- Healing & Recovery
- Level
- Intermediate
- Duration
- 8–12 weeks
Section 06
Stability & Storage
Lyophilised powder
Kept sealed, away from light and moisture: unopened vials last up to 2 years at −20 °C, or up to 6 months at 2–8 °C. It is reconstituted with bacteriostatic water (0.9% benzyl alcohol) added slowly down the vial wall to limit foaming, then swirled gently — vortexing or vigorous shaking can cause the protein to aggregate and lose activity.
After reconstitution
The N-terminal acetylation that protects TB-500 from aminopeptidase degradation gives it comparatively good stability, though the methionine residue remains prone to oxidation; some preparations add methionine to the reconstitution solution to limit this. The solution is kept at 2–8 °C and used within 21–28 days.
Section 07
Side Effects & Precautions
Reported effects with TB-500 are mostly mild and transient, but human safety data remain limited, and there are unresolved theoretical concerns about its effect on tumor growth.
Injection Site Reactions
Mild pain, redness, and swelling at injection sites are common, particularly with subcutaneous administration. Rotating injection sites minimizes local irritation.
Commonly Reported Symptoms
- Lightheadedness or mild headache right after injection is the most commonly reported effect, usually resolving in 15-30 minutes; may relate to vasodilatory effects.
- Temporary fatigue or lethargy has been reported, particularly during the initial loading phase, typically resolving as the body adjusts.
- Mild nausea has been reported, particularly at higher doses.
Theoretical Cancer Concerns
TB-500 promotes cell migration and angiogenesis (new blood vessel formation) — processes also involved in tumor growth and metastasis — raising theoretical concerns about its use in people with active or undiagnosed cancer. No direct evidence links TB-500 to cancer promotion in research subjects.
Limited Human Safety Data
TB-500 has not undergone comprehensive clinical trials, so its full safety profile in humans remains incompletely characterized. Most safety data comes from animal studies and anecdotal reports.
Section 08
Regulatory Status
It remains an investigational compound with a long history in veterinary recovery medicine and, as of mid-2026, a live FDA compounding review.
FDA / United States
Not approved
TB-500 was not on the 503A Bulks List as of 5 August 2026, and section 503A lets a pharmacy compound from a bulk substance only when it carries a USP/NF monograph, is a component of an approved drug or appears on that list — so no lawful compounding route is open.
FDA review
A committee has recommended easing
On 23 July 2026 the Pharmacy Compounding Advisory Committee voted 8 to 6 to add TB-500 to the 503A Bulks List; the vote does not bind the FDA, and the list changes only through formal rulemaking, which had not been completed as of this check.
WADA
Prohibited under category S2
TB-500 and its parent protein, Thymosin Beta-4, are named explicitly and banned at all times, in and out of competition.
Horse & greyhound racing
Banned in competition
Several racing jurisdictions prohibit TB-500 in competing animals, reflecting its long use in equine and canine injury recovery.
Clinical trials
Only early-phase data exists
Small Phase 1/2 studies for cardiac indications ran under FDA IND protocols, but no Phase 3 trial has been completed for any indication.
A Pharmacy Compounding Advisory Committee vote is a recommendation, not a decision — formal rulemaking can take 8 to 12 months, and status differs between jurisdictions and changes over time. Check current documents from your own regulator before relying on any of this.
We cover the 23–24 July 2026 vote of the FDA's Pharmacy Compounding Advisory Committee (PCAC) separately, in «The 2026 PCAC Peptide Vote» (/en/articles/fda-pcac-2026-peptides). In short: on 23 July the committee recommended adding TB-500 to the 503A Bulks List — 8 votes to 6, against the written position of the FDA's own reviewers. The recommendation binds no one: the list changes only through formal rulemaking, which usually takes 8–12 months, and even a place on it would not make TB-500 an approved medicine.
Section 09
Research Studies
- [1]Thymosin β4 and Fx, an actin-sequestering peptide, are indistinguishableSafer D, Elzinga M, Nachmias VT. · Journal of Biological Chemistry · 1991
- [2]Thymosin β4 stimulates directional migration of human umbilical vein endothelial cellsMalinda KM, Goldstein AL, Kleinman HK. · The FASEB Journal · 1997
- [3]Thymosin β4 accelerates wound healingMalinda KM, Sidhu GS, Mani H, Banaudha K, Maheshwari RK, Goldstein AL, Kleinman HK. · Journal of Investigative Dermatology · 1999
- [4]Thymosin β4 enhances endothelial cell differentiation and angiogenesisGrant DS, Rose W, Yaen C, Goldstein A, Martinez J, Kleinman H. · Angiogenesis · 1999
- [5]Thymosin β4 activates integrin-linked kinase and promotes cardiac cell migration, survival and cardiac repairBock-Marquette I, Saxena A, White MD, DiMaio JM, Srivastava D. · Nature · 2004
- [6]Thymosin β4: actin-sequestering protein moonlights to repair injured tissuesGoldstein AL, Hannappel E, Kleinman HK. · Trends in Molecular Medicine · 2005
- [7]Thymosin β4 induces adult epicardial progenitor mobilization and neovascularizationSmart N, Risebro CA, Melville AA, Moses K, Schwartz RJ, Chien KR, Riley PR. · Nature · 2007
- [8]Thymosin beta 4 suppression of corneal NFκB: A potential anti-inflammatory pathwaySosne G, Qiu P, Christopherson PL, Wheater MK. · Experimental Eye Research · 2007
- [9]Thymosin β4 Is an Essential Paracrine Factor of Embryonic Endothelial Progenitor Cell-Mediated CardioprotectionHinkel R, El-Aouni C, Olson T, Horstkotte J, Mayer S, Muller S, et al. · Circulation · 2008
- [10]Thymosin β4 and prothymosin α promote cardiac regeneration post-ischaemic injury in miceGladka MM, Johansen AKZ, van Kampen SJ, Peters MMC, Molenaar B, Versteeg D, et al. · Cardiovascular Research · 2023
Section 10
Frequently Asked Questions
Almost everything cited in its favor comes from animal research on the whole 43-amino-acid Thymosin Beta-4 protein, not the short fragment sold as TB-500. Even widely repeated claims about equine tendon and ligament repair are not supported by any publication found, despite being standard marketing language; the fragment itself has no controlled human trial behind it for any use.
WADA explicitly prohibits both TB-500 and Thymosin Beta-4 under its S2 category, banned in and out of competition, and several horse-racing jurisdictions ban its use during competition as well. It is not approved by the FDA, EMA or any major regulator for human use and exists only as a research and veterinary compound.
Self-administration protocols circulating online use 2–5 mg twice weekly tapering to 2–2.5 mg weekly or every two weeks, but no controlled human trial of TB-500 exists for any indication, so these figures are seller practice, not research findings. The human safety data that does exist — doses of 42 to 1,260 mg in a Phase 1 trial — tested the whole 43-amino-acid protein given differently, at doses hundreds of times larger than what is sold as TB-500.
No oral human data exist for TB-500 or for the whole Thymosin Beta-4 protein it comes from. The only related oral evidence is rat studies giving the full-length protein by stomach tube at 1–5 mg/kg — a different molecule, in a different species, never repeated in a person.
Pairing the two is a common self-administration pattern, but it is a vendor and community practice, not a tested protocol. No controlled human trial has evaluated TB-500 alone, let alone in combination with anything else, so there is no data on whether combining changes the outcome either way.
Reported effects include transient lightheadedness or head rush after injection, injection-site pain and swelling, fatigue and mild nausea. Because TB-500 promotes cell migration and new blood vessel growth — processes also involved in tumour growth — there is a theoretical concern about use in anyone with an active or undiagnosed malignancy, though no direct evidence of cancer promotion has been reported in research subjects.
Unopened lyophilised vials last up to 2 years at −20°C or 6 months at 2–8°C, kept sealed and away from light and moisture. It is reconstituted gently with bacteriostatic water — vigorous shaking can make the protein clump and lose activity — and the resulting solution is kept at 2–8°C and used within 21–28 days.