TB-500
Thymosin Beta-4 Fragment · Tβ4(17-23) · TB500
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TB-500 is a synthetic heptapeptide corresponding to residues 17–23 of the 43-amino acid protein Thymosin Beta-4 (Tβ4). The fragment sequence is Ac-Ser-Asp-Lys-Pro-Asp-Met-Ala (7 residues, MW ~889 Da). TB-500 is not the same molecule as full-length Tβ4 (MW 4,963 Da) — they are distinct compounds with different synthesis scope and different pharmacokinetic profiles. TB-500's primary research mechanism is actin sequestration: it binds G-actin (monomeric), regulates the ratio of free actin to filamentous F-actin, and through this mechanism promotes cell migration, wound healing, and tissue remodelling. A downstream effect of actin regulation is reduced pro-inflammatory cytokine signalling. Full-length Tβ4 additionally drives cardiac progenitor cell differentiation and cardiac regeneration in injury models — effects that have not been independently established for the fragment TB-500.
In-depth Research Guide
TB-500 (Thymosin Beta-4): Mechanisms, Recovery Research, and What the Evidence Shows
In-depth Research Guide
BPC-157 vs TB-500: Mechanism, Evidence, and When Each Makes Sense
Zero published human clinical trials exist specific to TB-500 (the Tβ4 fragment 17–23). The ongoing Phase II cardiac surgery trial examines full-length Thymosin Beta-4, not TB-500 — these are different molecules and results cannot be directly extrapolated. The preclinical literature is consistent for soft-tissue repair, anti-inflammatory effects, and cardiac progenitor activation (in full Tβ4). MW verification is critical for purchase: TB-500 (fragment, MW ~889 Da) vs full-length Tβ4 (MW 4,963 Da) — vendors conflating the two are selling different compounds. WADA-specific detection methods have been validated for TB-500 metabolites since 2011.
TB-500Also known as: Thymosin Beta-4 Fragment, Tβ4(17-23), TB500
Mechanism of Action
TB-500 is a synthetic heptapeptide corresponding to residues 17–23 of the 43-amino acid protein Thymosin Beta-4 (Tβ4). The fragment sequence is Ac-Ser-Asp-Lys-Pro-Asp-Met-Ala (7 residues, MW ~889 Da). TB-500 is not the same molecule as full-length Tβ4 (MW 4,963 Da) — they are distinct compounds with different synthesis scope and different pharmacokinetic profiles. TB-500's primary research mechanism is actin sequestration: it binds G-actin (monomeric), regulates the ratio of free actin to filamentous F-actin, and through this mechanism promotes cell migration, wound healing, and tissue remodelling. A downstream effect of actin regulation is reduced pro-inflammatory cytokine signalling. Full-length Tβ4 additionally drives cardiac progenitor cell differentiation and cardiac regeneration in injury models — effects that have not been independently established for the fragment TB-500.
Reported Research Benefits
- Actin sequestration: binds G-actin to regulate F-actin dynamics, promoting cell migration in wound and tissue repair models
- Anti-inflammatory: reduces pro-inflammatory cytokine expression (IL-1β, TNF-α) in injury models
- Connective tissue repair: accelerated tendon, muscle, and ligament healing in rodent models
- Cardiac progenitor cell activation: full-length Tβ4 data (Phase II cardiac surgery trial ongoing) — not directly extrapolatable to fragment
- WADA prohibited since 2011: detection metabolite assays developed and validated
- No published randomised human clinical trials specific to TB-500 as of 2026
Dosing Protocol & Reconstitution
Reported Research Dosing — Not Clinical Recommendations
TB-500 has no FDA-approved dosing protocol and no published human orthopaedic or performance trials. The ranges below come from practitioner-level protocols and extrapolation from ophthalmic and dermal Tβ4 human studies.
Dosing by Protocol Phase
| Phase | Dose | Frequency | Duration |
|---|---|---|---|
| Loading | 4–10 mg | Twice weekly | 4–6 weeks |
| Maintenance | 2–5 mg | Once weekly | 4–8 weeks |
| Taper | 2 mg | Once weekly | 2 weeks |
Total typical cycle: 10–16 weeks including taper. 2–4 week washout recommended between cycles.
Administration
- Route: subcutaneous or intramuscular injection
- Site rotation: abdomen, thigh, deltoid — rotate to avoid local tolerance
- Systemic distribution: TB-500 distributes widely, so injection site does not need to match target tissue (unlike BPC-157, which is typically injected near the injury)
Pharmacokinetics That Drive Weekly Dosing
TB-500's long tissue residence (G-actin binding is stoichiometric and slow-release) supports weekly dosing despite a shorter plasma half-life. Published ophthalmic and dermal Tβ4 studies use dosing intervals of 2–7 days without loss of effect.
Reconstitution
- 5 mg vial + 2 mL bacteriostatic water = 2,500 mcg/mL. A 2 mg dose = 0.8 mL.
- 10 mg vial + 2 mL bacteriostatic water = 5,000 mcg/mL. A 2 mg dose = 0.4 mL.
- Use a 1 mL syringe (not insulin U-100) — insulin syringes don't reliably deliver volumes above 0.5 mL at this concentration.
- Reconstituted solution stable 28 days refrigerated at 2–8°C. Do not freeze.
Contraindications and Cautions
- Active malignancy: Tβ4's role in angiogenesis and cell migration creates theoretical concern in tumour biology; oncology populations have not been formally studied.
- Active infection: anti-inflammatory activity via NF-κB suppression may interfere with immune response.
- Corneal neovascularisation risk: Tβ4 can drive pathological corneal revascularisation — caution in ophthalmic conditions.
- Pregnancy and lactation: no data; avoid.
- Drug interactions: not characterised.
- WADA status: prohibited in competitive sport.
Stacking with BPC-157
The "Wolverine Stack" combines TB-500 weekly with BPC-157 daily. The mechanistic rationale (systemic cell migration + local angiogenesis) is real, but no controlled trial has compared the stack against either compound alone. See the BPC-157 vs TB-500 comparison for the full evaluation.
Research Notes
Zero published human clinical trials exist specific to TB-500 (the Tβ4 fragment 17–23). The ongoing Phase II cardiac surgery trial examines full-length Thymosin Beta-4, not TB-500 — these are different molecules and results cannot be directly extrapolated. The preclinical literature is consistent for soft-tissue repair, anti-inflammatory effects, and cardiac progenitor activation (in full Tβ4). MW verification is critical for purchase: TB-500 (fragment, MW ~889 Da) vs full-length Tβ4 (MW 4,963 Da) — vendors conflating the two are selling different compounds. WADA-specific detection methods have been validated for TB-500 metabolites since 2011.
Research Summary
TB-500 (Tβ4 fragment 17–23) has no published human RCTs. Full-length Thymosin Beta-4 has a Phase II cardiac surgery trial in progress. Preclinical evidence for TB-500 includes soft-tissue repair, reduced inflammation, and cardiac progenitor activation across rodent injury models. WADA banned since 2011 with validated detection assay. Minimum research quality: HPLC ≥98%, MS at ~889 Da (not 4,963 Da), independent lab COA with verifiable lot number.
Side Effects & Safety
Human adverse event data is limited to observational clinical practitioner reports: injection site reactions (erythema, mild induration) are the most commonly noted. No serious adverse events have been systematically reported. The Tβ4 cardiac Phase II trial reported acceptable tolerability. Theoretical concerns include: angiogenic promotion in neoplastic tissue (same concern as BPC-157); unknown long-term effects on endogenous Tβ4 production. WADA prohibited — detectable in competitive doping testing.
Stability & Storage
Lyophilised powder: stable at -20°C for 2–3 years. After reconstitution with bacteriostatic water: store at 4°C, use within 21–28 days. Do not freeze reconstituted solution. Sensitive to repeated temperature cycling.
Molecular Data
- Sequence
- Ac-Ser-Asp-Lys-Pro-Asp-Met-Ala (fragment of full Tβ4; residues 17–23)
- Molecular Formula
- C36H60N10O12S
- Molecular Weight
- ~889 Da (fragment 17–23) — NOT 4,963 Da (full-length Tβ4)
- CAS Number
- 77591-33-4 (Thymosin Beta-4 fragment; verify for specific salt form)
- Half-Life
- Not formally characterised for fragment; full Tβ4 IV half-life several hours in animal models
Primary literature: https://pubmed.ncbi.nlm.nih.gov/?term=thymosin+beta+4+healing