Thymosin Beta-4 Fragment — Actin Regulator
TB-500 is a synthetic version of the naturally occurring 43-amino-acid peptide Thymosin Beta-4 (Tβ4), the primary G-actin sequestering molecule in mammalian cells. Thymosin Beta-4 was originally isolated from the thymus gland in 1981 by Allan Goldstein and colleagues, though it was later discovered to be expressed ubiquitously in virtually all nucleated cells. TB-500 represents the full-length Thymosin Beta-4 sequence and is used in research interchangeably with Tβ4, though commercial preparations may focus on the active domain. The peptide plays a fundamental role in cellular processes by regulating the polymerization of G-actin (globular actin) into F-actin (filamentous actin), which forms the cytoskeletal framework necessary for cell migration, adhesion, and tissue organization. By sequestering G-actin monomers, TB-500 maintains a pool of available actin that can be rapidly deployed when cells need to migrate — as occurs during wound healing, angiogenesis, and tissue repair. TB-500 was first demonstrated to accelerate wound healing by Malinda et al. in 1999 and subsequently shown to promote cardiac repair following myocardial infarction in a landmark 2007 Nature publication by Smart et al. This cardiac research demonstrated that Thymosin Beta-4 activates adult epicardial progenitor cells, promoting neovascularization and cardiomyocyte survival — findings that generated significant interest in its systemic repair properties.
Promotes directional cell migration through G-actin sequestration and cytoskeletal remodeling — essential for wound closure.
Promotes new blood vessel formation throughout the body, improving perfusion to damaged tissues.
Nature publication showed epicardial progenitor activation and neovascularization following myocardial infarction in mice.
Reduces inflammatory cytokines and modulates NF-κB signaling, decreasing tissue damage from excessive inflammation.
Accelerated dermal wound closure, corneal epithelial healing, and hair regrowth in preclinical models.
Enhances migration of stem and progenitor cells to injury sites, supporting endogenous repair mechanisms.
Acts systemically regardless of injection location — does not require injection near the injury site like locally acting peptides.
TB-500's primary mechanism centers on its role as the principal intracellular G-actin sequestering peptide. In resting cells, TB-500 binds G-actin monomers in a 1:1 stoichiometric complex, preventing spontaneous polymerization into F-actin filaments. When cellular signals (growth factors, chemokines) trigger migration, TB-500 releases G-actin monomers that rapidly polymerize at the leading edge of the cell, forming lamellipodia and filopodia that drive directional movement. The actin-binding domain responsible for this activity is a 17-amino-acid sequence (LKKTETQ) within the peptide that directly contacts actin. This domain also promotes actin cross-linking and branching via interactions with Arp2/3 complex, enabling the complex cytoskeletal remodeling required for cell migration through three-dimensional tissue matrices. Beyond actin dynamics, TB-500 exerts anti-inflammatory effects through downregulation of NF-κB and inhibition of pro-inflammatory cytokines including IL-1β, IL-6, and TNF-α. In cardiac research, TB-500 activates Akt (protein kinase B) signaling in cardiomyocytes, promoting survival through inhibition of apoptotic caspase cascades. The peptide also activates integrin-linked kinase (ILK) and PINCH pathways that regulate cell-extracellular matrix interactions during tissue remodeling. Collectively, these mechanisms — enhanced cell migration, angiogenesis, anti-inflammation, and pro-survival signaling — produce a systemic tissue repair response.
Epicardial progenitor cell activation, neovascularization, and cardiomyocyte survival following experimental myocardial infarction.
PreclinicalAccelerated dermal wound closure, corneal repair, and hair follicle stem cell activation in multiple animal models.
PreclinicalEnhanced muscle, tendon, and ligament repair through improved cell migration to injury sites and angiogenesis.
PreclinicalOligodendrocyte differentiation and myelination promotion following traumatic brain injury in rodent models.
PreclinicalCorneal epithelial wound healing acceleration — RegeneRx Biopharmaceuticals has conducted human trials for dry eye.
Phase 2/3| Period | Dose | Frequency | Notes |
|---|---|---|---|
| 1–2 | 2–2.5 mg | 2× per week (SC/IM) | Loading phase — higher frequency for initial tissue response |
| 3–4 | 2–2.5 mg | 2× per week (SC/IM) | Continued loading phase |
| 5–8 | 2.5 mg | 1–2× per week (SC/IM) | Transition to maintenance frequency |
| 9+ | 2.5–5 mg | 1× per week (SC/IM) | Maintenance phase — can extend to 12–16 weeks |
No. Unlike some locally-acting peptides, TB-500 acts systemically. Subcutaneous injection in the abdominal area or deltoid will distribute the peptide throughout the body via the bloodstream. The peptide promotes cell migration, angiogenesis, and anti-inflammatory signaling regardless of injection location. This is a key advantage for research protocols involving injuries in difficult-to-inject locations.
TB-500 is a synthetic version of the naturally occurring Thymosin Beta-4 (Tβ4) peptide. In most commercial preparations, TB-500 represents the full 43-amino-acid Tβ4 sequence. The terms are often used interchangeably in research contexts. Some preparations may focus on the active domain containing the LKKTETQ actin-binding sequence, but this varies by supplier.
Yes — this is one of the most studied peptide combinations in the research community. BPC-157 works primarily through VEGF/NO/growth factor modulation while TB-500 works through actin-mediated cell migration. The mechanisms are complementary rather than competitive. The GLOW blend (BPC-157 + TB-500 + GHK-Cu) is a pre-formulated example of this multi-pathway approach.
Reconstitute lyophilized TB-500 with bacteriostatic water at 2.5 mg/mL (e.g., 2 mL BAC water for a 5 mg vial). Inject water slowly against the vial wall and swirl gently — do not shake. The solution should be clear and colorless. Store at 2–8°C and use within 21 days.
Standard research protocols run 4–8 weeks, with a 2–4 week loading phase (twice weekly) followed by a maintenance phase (once weekly). Extended protocols may run 12–16 weeks depending on the research endpoint. The twice-weekly loading frequency reflects the relatively short 2-hour half-life, ensuring consistent tissue exposure during the initial repair phase.
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