Overview
A synthetic fragment related to thymosin beta-4, a naturally occurring actin-sequestering protein. Research focuses on cell migration, angiogenesis and soft-tissue repair, with a substantial veterinary literature.
Mechanism of Action
Thymosin beta-4 is the major actin-sequestering protein in mammalian cells. TB-500 corresponds to the active binding region of that protein.
By binding G-actin, the peptide is reported to influence actin polymerisation, a process central to cell motility — the movement of repair cells such as fibroblasts and endothelial cells into damaged tissue.
Animal work describes promotion of endothelial cell migration and new blood-vessel formation in ischaemic and injured tissue.
Anti-inflammatory and antifibrotic effects have been reported in cardiac and corneal injury models.
Areas Being Studied
- Soft-tissue and tendon repair
- Cardiac tissue injury models
- Corneal and dermal wound healing
- Equine and veterinary recovery research
Listing a research area does not imply efficacy, approval, or suitability for any use.
Research Summary
- Thymosin beta-4 has been evaluated in early-phase human trials for dermal wound healing and dry eye, sponsored under the designation RGN-259 and related programmes.
- Cardiac research in animal models reports improved cardiomyocyte survival and reduced scar formation after induced infarction.
- The peptide has a longer effective duration than most repair peptides, which is why study protocols typically use weekly or twice-weekly dosing intervals with a loading phase.
- Human data for the TB-500 fragment specifically, as distinct from full-length thymosin beta-4, is limited.
Potential Adverse Effects Reported in Research
- Published studies report few adverse observations at studied doses; the toxicity profile is described as favourable in animal work.
- Transient lethargy and injection-site reactions appear in anecdotal and veterinary reports.
- As with other angiogenic peptides, researchers note theoretical concerns regarding tissue with existing abnormal growth.
- Human safety characterisation remains incomplete.
Reconstitution Basics
Commonly supplied in 5 mg or 10 mg vials. Because doses are in the milligram range, small reconstitution volumes produce very small draw volumes.
Bacteriostatic water
Sterile water containing roughly 0.9% benzyl alcohol as a preservative, which inhibits bacterial growth in multi-access vials.
Sterile technique
Laboratory documentation describes disinfecting the stopper, using a fresh sterile needle for each access, and avoiding contact with non-sterile surfaces.
After reconstitution
Solutions are refrigerated, protected from light, and not subjected to repeated freeze–thaw cycles.
This section is educational background on laboratory handling. It is not an instruction or protocol.
Open the reconstitution calculator →Dosing & Reconstitution Guide
Reference protocols for a 10 mg TB-500 vial describe reconstituting with 3.0 mL of bacteriostatic water for ~3.33 mg/mL (3,333 mcg/mL), then a once-daily subcutaneous dose titrated from ~500 mcg to ~1,000 mcg across an 8–12 week course (roughly 5 mg per week). At that concentration 1 unit on a U-100 syringe ≈ 33.3 mcg, so every dose reads at 15 units or more.
Protocol overview
- One 10 mg vial reconstituted with 3.0 mL yields ~3.33 mg/mL; 500 mcg ≈ 15 units and 1,000 mcg ≈ 30 units on a U-100 syringe.
- Subcutaneous administration once daily is the route and frequency described in the reference protocols.
- A 10 mg vial covers roughly two weeks at the ~5 mg/week average, so an 8-week course uses about 4 vials and a 16-week course about 8.
- The large 3.0 mL dilution is chosen so doses land at 15 units or more, where U-100 markings are most precise.
- There are no completed human efficacy trials of the TB-500 fragment; TB-500 is prohibited in competitive sport under WADA rules.
Dosing protocol — standard titration
| Phase | Reported dose | Notes |
|---|---|---|
| Weeks 1–2 | 500 mcg once daily (~15 units / 0.15 mL)Entry phase at the largest practical dilution. | Entry phase at the largest practical dilution. |
| Weeks 3–4 | 600 mcg once daily (~18 units / 0.18 mL)First step up. | First step up. |
| Weeks 5–8 | 750 mcg once daily (~22.5 units / 0.225 mL)Mid-course figure in cited schedules. | Mid-course figure in cited schedules. |
| Weeks 9–12 | 1,000 mcg once daily (~30 units / 0.30 mL)Top of the documented range; ~5 mg/week average. | Top of the documented range; ~5 mg/week average. |
Dosing protocol — gradual titration
| Phase | Reported dose | Notes |
|---|---|---|
| Weeks 1–2 | 250–500 mcg once daily (~8–15 units)Conservative entry below the cited start. | Conservative entry below the cited start. |
| Weeks 3–6 | 500 mcg once daily (~15 units)Held longer before escalating. | Held longer before escalating. |
| Weeks 7–10 | 750 mcg once daily (~22.5 units)Slower step-up than the standard track. | Slower step-up than the standard track. |
| Weeks 11–12 | 1,000 mcg once daily (~30 units)Reached only at the end of the course. | Reached only at the end of the course. |
Schedules summarise what appears in published studies, trial protocols or manufacturer documentation. They are reference material, not a recommendation.
Where to Buy Compounds & Supplies
External link. PepDex does not sell products and does not endorse any supplier.
Supplies needed
Lyophilised peptide vial
Sealed vial with an intact stopper and a legible mass label (mg or mcg).
Bacteriostatic water
Sterile water with ~0.9% benzyl alcohol, used where a vial will be accessed more than once. Sterile water for injection is used for single-access work.
Reconstitution syringe
A 1–3 mL syringe with a larger-gauge needle for drawing and transferring solvent.
Insulin syringe (U-100)
Fine-gauge syringe graduated in units; 100 units = 1 mL. Used for accurate small-volume measurement.
Alcohol prep pads
70% isopropyl swabs for disinfecting both vial stoppers before every access.
Sharps container
Rigid, puncture-resistant container for single-use needle disposal.
Refrigeration and light protection
2–8 °C storage plus an opaque box or the original carton for reconstituted vials.
Labels
Date of reconstitution, resulting concentration and compound name on every vial.
Reconstitution steps
- 01
Bring the vial to room temperature
Lyophilised powder is allowed to equilibrate out of the refrigerator before the stopper is pierced, which reduces condensation inside the vial.
- 02
Disinfect both stoppers
The peptide vial and the bacteriostatic water vial are each swabbed with 70% isopropyl alcohol and allowed to air dry.
- 03
Draw the calculated solvent volume
Solvent volume is chosen to produce a convenient concentration — the reconstitution calculator converts vial mass and solvent volume into concentration and syringe units.
- 04
Add the solvent slowly down the vial wall
The stream is directed against the glass rather than onto the powder cake. Peptides are shear-sensitive and direct jetting is avoided.
- 05
Dissolve without shaking
The vial is left to stand, then gently swirled or rolled. Shaking introduces foam and mechanical stress that can denature peptide chains.
- 06
Inspect the solution
Documentation describes checking for a clear, particle-free solution. Cloudiness, visible particulate or discolouration is treated as a failed preparation.
- 07
Label and refrigerate
The vial is labelled with compound, concentration and date, then stored at 2–8 °C protected from light.
Storage instructions
- Lyophilized vials: store at −20 °C (−4 °F) until reconstitution.
- After reconstitution: refrigerate at 2–8 °C (35.6–46.4 °F) and do not freeze the mixed solution.
- Protect the reconstituted vial from light and label it with the date and concentration.
- Avoid freeze–thaw cycles, which can denature the peptide.
- Reconstituted solution is commonly cited as usable for ~30 days refrigerated.
Half-Life
~2–3 days
The relatively long duration reported in the literature is the basis for weekly rather than daily study schedules.
Storage
- Before reconstitution
- Lyophilised vials stored refrigerated or frozen.
- After reconstitution
- Refrigerated at 2–8 °C after reconstitution.
- Light protection
- Kept away from direct light.
- Shelf-life considerations
- Reconstituted solution typically described as stable for several weeks refrigerated.
Frequently Asked Questions
References
- Thymosin beta4: a multi-functional regenerative peptide
Annals of the New York Academy of Sciences
- Thymosin β4 and cardiac repair
Annals of the New York Academy of Sciences
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Educational reference only. Figures are compiled from published research literature. PepDex does not provide medical advice, dosing recommendations, or instructions for use.