Last updated: May 18, 2026
What TB-500 is
TB-500 (also called Thymosin Beta-4 Fragment 17-23, or simply the active fragment of Tβ4) is a synthetic peptide with the sequence Leu-Lys-Lys-Thr-Glu-Thr-Gln. It corresponds to a biologically active region of full-length thymosin beta-4, a 43-amino-acid endogenous protein.
Both TB-500 and full-length thymosin beta-4 are used interchangeably in many research contexts, though they differ in molecular weight and pharmacokinetics.
Mechanism
The primary action is regulation of actin polymerization. Tβ4 sequesters G-actin and prevents its polymerization to F-actin, which:
- Promotes cell migration (key for wound healing)
- Reduces inflammation
- Stimulates angiogenesis (via stem cell mobilization)
- Decreases scar formation
Secondary effects include modulation of bone marrow stem cell mobilization, cardiac progenitor cell activation, and corneal epithelial regeneration.
Research applications
Muscle and tendon healing
Rodent studies show accelerated recovery from muscle injury, tendon transection, and ligament damage. Mechanical strength returns faster than untreated controls.
Cardiac repair
Mouse models of myocardial infarction show TB-500/Tβ4 administration reduces scar size and improves cardiac function via activation of epicardial-derived progenitor cells.
Wound healing
Topical and systemic application accelerates wound closure in animal models. A Phase 2 trial in venous stasis ulcers showed promising results but did not progress to Phase 3.
Eye applications
Tβ4-based corneal repair products have undergone clinical trials for dry eye and neurotrophic keratitis.
Dosing protocols (research community use)
Commonly cited research-community protocols use 2-2.5 mg per week, often split into 2 weekly subcutaneous doses, for 4-6 weeks. A “loading phase” of 5-10 mg per week for 2-3 weeks followed by maintenance dosing is also described. These protocols are not FDA-approved or clinically validated.
BPC-157 + TB-500 stack
The most common research-community pairing. The hypothesis: BPC-157 promotes angiogenesis (new blood vessels at injury sites) while TB-500 promotes cell migration into those new vessels. No published clinical or animal study directly tests the combination, but anecdotal reports describe synergistic effects.
Safety profile
Rodent and limited human data show favorable tolerability. Reported side effects: mild fatigue, occasional injection-site reactions, head-rush sensation immediately post-injection. No serious adverse events reported in available literature.
Regulatory status
- US: Sold as research peptide; not FDA-approved
- WADA: Banned since 2011 (S2 peptide hormones)
- Australia (TGA): Restricted
Is TB-500 the same as thymosin beta-4?<br />
TB-500 is a fragment of thymosin beta-4 that contains the biologically active region. Full-length Tβ4 is the larger endogenous protein. They are often used interchangeably in research but differ in pharmacokinetics.
How does TB-500 work?<br />
It regulates actin polymerization, promoting cell migration and tissue regeneration. It also has anti-inflammatory and angiogenic effects.
What’s the typical research dose?<br />
Common research-community protocols use 2-2.5 mg per week subcutaneously, often loaded at 5-10 mg/week for 2-3 weeks then maintained at 2 mg/week.
Why pair TB-500 with BPC-157?<br />
Theoretical synergy — BPC-157 promotes new blood vessel growth while TB-500 promotes cell migration. The combination is studied informally but not in published controlled trials.