TB-500

TB-500 is a synthetic version of thymosin beta-4 (Tβ4), a 43-amino acid peptide naturally present in virtually all human and animal cells. Thymosin beta-4 is the primary intracellular G-actin sequestering peptide, playing a central role in cytoskeletal dynamics, cell motility, and tissue repair. The designation "TB-500" refers specifically to the synthetic research-grade form used in investigational settings.

The active fragment Ac-SDKP (N-acetyl-seryl-aspartyl-lysyl-proline) is a four-amino acid peptide released by enzymatic cleavage of thymosin beta-4. This tetrapeptide mediates several of the anti-inflammatory and anti-fibrotic effects attributed to the parent molecule. TB-500 remains an unregulated research compound with no clinical approval, though Tβ4-based formulations have entered clinical trials for dermal and ophthalmic applications.

Thymosin beta-4 functions primarily through its interaction with monomeric actin (G-actin), preventing premature polymerization into filamentous actin (F-actin). This regulation of actin dynamics is essential for cell migration, a prerequisite for wound healing and tissue repair. Beyond cytoskeletal regulation, Tβ4 activates integrin-linked kinase (ILK), which triggers downstream Akt/PKB survival signaling, reducing apoptosis in damaged tissues.

The peptide also promotes angiogenesis by upregulating VEGF expression and stimulating endothelial cell differentiation. Its anti-inflammatory effects involve downregulation of NF-κB-mediated pro-inflammatory cytokines including IL-1β, IL-6, and TNF-α. The Ac-SDKP fragment specifically inhibits TGF-β-driven fibrosis, reducing collagen I deposition in models of cardiac and renal fibrosis. These parallel mechanisms of reduced inflammation, enhanced cell migration, and suppressed fibrosis collectively contribute to its observed regenerative effects.