Thymosin Beta-4 is the natural 43-amino-acid peptide, present in virtually all nucleated cells and concentrated in platelets and wound fluid. TB-500, as the FDA defines it, is a synthetic N-acetylated fragment 17-23 of that peptide — the seven-residue LKKTETQ motif. Full-length synthetic Tβ4 is sold under the same name, so the certificate of analysis decides.
Key parameters side by side
Parameter
TB-500
Thymosin Beta-4
Evidence status
Clinical Trial
Experimental
Sequence length
7
43
Molecular weight
889.01 Da
4963.44 Da
Same for both: Category — Tissue Repair
Frequently asked questions
By length. Thymosin beta-4 is the endogenous 43-amino-acid peptide, the most abundant member of the beta-thymosin family, first isolated from the thymus. TB-500, as the FDA defines it, is a synthetic fragment 17-23 of that same peptide: seven residues, N-acetyl-LKKTETQ, 889 Da against roughly 4963 Da for the full-length molecule. Sellers use the name for both, so the certificate of analysis settles which one a vial holds.
Almost all published evidence concerns full-length Tβ4 (RGN-259 and related programmes), whose ordinary drug programme stalled. The fragment keeps actin binding and cell migration but carries neither the Ac-SDKP domain (residues 1-4) nor residues 1-15, and it sits under a separate FDA compounding review. WADA bans both forms.
Tissue Repair
TB-500
Clinical Trial
TB-500 is a synthetic, N-acetylated heptapeptide: fragment 17-23 of thymosin beta-4 (Tβ4), which is the actin-binding motif LKKTETQ. That is how the FDA defines it — N-acetyl-LKKTETQ, C38H68N10O14, 889.01 g/mol as the free base and 949.1 as the acetate, UNII QHK6Z47GTG — and calls it the presumed active moiety of full-length Tβ4, a naturally occurring 43-amino acid peptide present in virtually all human and animal cells (Briefing Document for the Pharmacy Compounding Advisory Committee, 23 July 2026).
The same name is also sold on the research-peptide market for full-length synthetic Tβ4 of 43 amino acids, so what a particular product contains is settled by its certificate of analysis, not by its label. The distinction decides what the evidence covers: almost everything published concerns full-length Tβ4 (RGN-259 and related programmes). The fragment keeps actin binding and the cell migration that follows from it, but carries neither the Ac-SDKP domain (residues 1-4, anti-inflammatory and antifibrotic) nor residues 1-15 (anti-apoptotic).
The peptide has generated substantial research interest for its therapeutic potential in wound healing, cardiac repair following myocardial infarction, neurological recovery, and musculoskeletal injury. It is widely used in equine and veterinary medicine for tissue repair. TB-500 is not approved for human clinical use and is prohibited by WADA.
Thymosin Beta-4 (Tβ4) is a 43-amino acid, naturally occurring peptide and the most abundant member of the beta-thymosin family. Originally isolated from the thymus gland, Tβ4 is found in virtually all nucleated cells and is particularly concentrated in blood platelets, wound fluid, and developing tissues. TB-500 is its synthetic 17-23 fragment (Ac-LKKTETQ); Tβ4 itself serves as the primary intracellular G-actin sequestering protein, fundamentally regulating cytoskeletal dynamics.
Tβ4 plays essential roles in embryonic development (cardiac, vascular, and neural morphogenesis) and adult tissue repair. Its central actin-binding motif LKKTETQ drives cell migration, angiogenesis, and wound healing across virtually all tissue types. RegeneRx Biopharmaceuticals has advanced Tβ4 through clinical trials for cardiac repair, wound healing, and ophthalmological applications, making it one of the most clinically studied regenerative peptides.
TB-500 is a synthetic, N-acetylated heptapeptide: fragment 17-23 of thymosin beta-4 (Tβ4), which is the actin-binding motif LKKTETQ. That is how the FDA defines it — N-acetyl-LKKTETQ, C38H68N10O14, 889.01 g/mol as the free base and 949.1 as the acetate, UNII QHK6Z47GTG — and calls it the presumed active moiety of full-length Tβ4, a naturally occurring 43-amino acid peptide present in virtually all human and animal cells (Briefing Document for the Pharmacy Compounding Advisory Committee, 23 July 2026).
The same name is also sold on the research-peptide market for full-length synthetic Tβ4 of 43 amino acids, so what a particular product contains is settled by its certificate of analysis, not by its label. The distinction decides what the evidence covers: almost everything published concerns full-length Tβ4 (RGN-259 and related programmes). The fragment keeps actin binding and the cell migration that follows from it, but carries neither the Ac-SDKP domain (residues 1-4, anti-inflammatory and antifibrotic) nor residues 1-15 (anti-apoptotic).
The peptide has generated substantial research interest for its therapeutic potential in wound healing, cardiac repair following myocardial infarction, neurological recovery, and musculoskeletal injury. It is widely used in equine and veterinary medicine for tissue repair. TB-500 is not approved for human clinical use and is prohibited by WADA.
Thymosin Beta-4 (Tβ4) is a 43-amino acid, naturally occurring peptide and the most abundant member of the beta-thymosin family. Originally isolated from the thymus gland, Tβ4 is found in virtually all nucleated cells and is particularly concentrated in blood platelets, wound fluid, and developing tissues. TB-500 is its synthetic 17-23 fragment (Ac-LKKTETQ); Tβ4 itself serves as the primary intracellular G-actin sequestering protein, fundamentally regulating cytoskeletal dynamics.
Tβ4 plays essential roles in embryonic development (cardiac, vascular, and neural morphogenesis) and adult tissue repair. Its central actin-binding motif LKKTETQ drives cell migration, angiogenesis, and wound healing across virtually all tissue types. RegeneRx Biopharmaceuticals has advanced Tβ4 through clinical trials for cardiac repair, wound healing, and ophthalmological applications, making it one of the most clinically studied regenerative peptides.