Thymosin Beta-4

Sequesters G-actin monomers via its WH2 domain, regulating actin dynamics and cell migration. Upregulates metalloproteinases and growth factors for tissue remodeling. Promotes cardiomyocyte survival and angiogenesis post-injury.

Thymosin beta-4 (Tb4) is an endogenous 43-amino-acid protein ubiquitously expressed in mammalian tissues, best characterized for its role in G-actin sequestration, cell migration promotion, and tissue repair signaling across multiple organ systems. Tb4 exerts reparative effects by upregulating angiogenesis, modulating inflammation, and generating the anti-fibrotic tetrapeptide Ac-SDKP through enzymatic cleavage; preclinical models in cardiac, renal, and musculoskeletal tissue have demonstrated measurable regenerative outcomes following exogenous administration. Published literature supports anti-fibrotic activity in animal models of renal fibrosis and cardiovascular injury, and the Tb4-Ac-SDKP pathway has been characterized as a plausible target in fibrosis biology; however, clinical translation has been limited, with a Phase 2 cardiac repair trial that did not demonstrate efficacy sufficient to advance to Phase 3. Exogenous thymosin beta-4 has no FDA approval for any indication; it is available only as a research compound, and the substantial gap between preclinical findings and human clinical outcomes represents an important limitation of the current evidence base. Thymosin beta-4 vs TB-500 TB-500 is a commercial label used for synthetic thymosin beta-4 in the peptide research market. The underlying compound is the same 43-amino-acid sequence as endogenous Tb4; "TB-500" originated as a brand name from veterinary product contexts and has since become the predominant research market name for synthetic thymosin beta-4. When research suppliers, athletes, or forum communities reference TB-500, they are referring to synthetic Tb4 — the same compound profiled here. The TB-500 label is commonly associated with injectable research peptide use; the thymosin beta-4 label is associated with the biochemical and medical literature. Some suppliers sell "TB-4 Frag" (the Ac-SDKP tetrapeptide fragment), which is a distinct, smaller molecule derived from enzymatic cleavage of Tb4, not the full-length thymosin beta-4 protein. Thymosin beta-4 dosage in research contexts: Research protocols described in preclinical literature and anecdotal human use reports typically reference doses in the range of 2–5 mg per injection, administered subcutaneously or intramuscularly, with a loading phase of 2–4 injections per week followed by a maintenance phase of 1–2 injections per week. These dosage figures are derived from research compound use and veterinary contexts, not from FDA-approved human clinical protocols — no approved human dosing exists. The Phase 2 cardiac repair trial that administered intravenous Tb4 used significantly different dose and route parameters. Thymosin beta-4 is available only as a research compound; it is not FDA-approved for any human indication and is not available through licensed prescription channels.