A Research Codex ~ Chapter I
TB-500 is the Ac-LKKTETQ fragment of thymosin beta-4, summarized from the published literature.
A solemn digest of what the thymosin beta-4 record establishes, where the human evidence stops, and how compounded access actually stands — every quantitative claim sealed to a study.
What the TB-500 record actually establishes
TB-500 is the synthetic, N-acetylated heptapeptide Ac-LKKTETQ — seven residues, roughly 889 Da — corresponding to positions 17 through 23 of thymosin beta-4, the body's principal actin-sequestering protein [9]. Those seven residues are the conserved actin-binding motif of the beta-thymosins. They are not the whole molecule. This distinction governs everything that follows on this site, because the overwhelming majority of efficacy data was generated with full-length thymosin beta-4 (~4963 Da), not the fragment that commerce and anti-doping science call TB-500.
The parent protein has a deep and reproducible record. X-ray crystallography resolved a 1:1 complex of thymosin beta-4 with monomeric (G-) actin, capping both ends of the monomer to hold a buffered pool of unpolymerized actin [1]. In a rat full-thickness wound model, thymosin beta-4 raised re-epithelialization by 42% at four days and up to 61% at seven days versus saline [3]. In mice, it activated the PINCH-ILK-Akt survival pathway and improved cardiac function after coronary ligation [2]. These are inscriptions worth setting plainly.
The caveat is equally plain, and it is the first crimson seal of this codex: there is no completed controlled clinical trial of the TB-500 heptapeptide for any indication. The only human evidence is for full-length thymosin beta-4 — a randomized, placebo-controlled Phase 1 intravenous study in 40 healthy volunteers, well tolerated to 1260 mg [6]. Whether the isolated seven-residue fragment reproduces the parent protein's effects at the doses used in peptide research is unproven. This site reads the TB-500 mechanism of action and the surrounding evidence as a record, not a recommendation.
TB-500 Peptide Identity: The Ac-LKKTETQ Fragment of Thymosin Beta-4
The TB-500 peptide is a short, defined sequence: Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln, molecular formula C38H68N10O14, molecular weight approximately 889.02 Da [9]. It is supplied as a lyophilized powder for laboratory use, reconstituted in sterile or bacteriostatic water. Because it is a short acetylated peptide rather than a folded protein, it is more chemically robust than its 43-residue parent, though still subject to proteolysis and freeze-thaw degradation.
The name encodes a lineage, not an indication. The first rigorous chemical characterization of the N-terminally acetylated 17-23 fragment was published as a doping-control reference, precisely because the substance had surfaced as a designer peptide outside any approved use [9]. That paper anchors the fragment's exact identity. It is also a reminder that the analytical world treats TB-500 as the seven-residue motif, while the therapeutic literature largely studies the whole protein — a gap this codex does not paper over.
Thymosin Beta-4: The Parent Protein Behind TB-500
Thymosin beta-4 (gene TMSB4X, UniProt P62328) is a ubiquitous 43-amino-acid peptide present in nearly all human cells and released by platelets and macrophages at sites of injury [5]. It is the body's major intracellular G-actin sequestering molecule. The LKKTETQ segment carried by TB-500 is its actin-binding core, but the full protein does more than bind actin: a 2012 review consolidated its roles in cell migration, reduced myofibroblast number and scarring, anti-inflammatory and anti-apoptotic signaling, and angiogenesis — the basis for clinical development in dermal wounds, corneal injury, and heart and CNS repair [5].
One further detail belongs to the parent and not the fragment. Full-length thymosin beta-4 yields Ac-SDKP, an N-terminal cleavage product with its own anti-fibrotic and angiogenic activity. The C-terminal-region TB-500 fragment does not generate it. When marketing for TB-500 leans on the parent protein's breadth, it is borrowing a record the seven-mer has not earned in controlled human work.
What this codex is, and what it is not
This is an independent editorial digest of the peer-reviewed literature on TB-500 and thymosin beta-4. It is not a clinic, a pharmacy, or a vendor. It does not sell, supply, or dispense any substance, and the word "pharmacy" in the name marks the editorial position this publisher occupies relative to the medicinal-access question — not a counter or a service.
Four chapters follow. The TB-500 mechanism of action chapter sets the actin-sequestration biology and the cardiac, wound, and neurological findings. The TB-500 anti-fibrotic research chapter reads the renal, hepatic, and pulmonary fibrosis models. The dosage chapter records what was administered, to which species, by which route — never a human dose. The TB-500 legal status chapter sets the FDA, 503A compounding, and WADA standing as a canon of record, with all regulatory facts cited to the FDA. The frequently asked questions gather the TB-500 side effects and safety signals and the rest of the record into one index.