What the Thymosin Beta-4 record actually shows — quietly, plate by plate.

The short version

TB-500 is a synthetic 7-amino-acid peptide — Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln-OH — sold in research channels as a fragment of Thymosin Beta-4, the body's principal actin-sequestering protein. The key thing to know first: virtually all of the encouraging evidence in this literature was generated using the full 43-amino-acid parent protein, not the short synthetic fragment. No registered human clinical trial of TB-500 itself has been published. TB-500 is also WADA-prohibited. None of that makes the underlying biology uninteresting — the parent protein has reached Phase I and Phase III in humans — but it does mean the gap between 'what animal studies show' and 'what TB-500 does in people' is real and unresolved. The plates that follow try to hold that gap open rather than paper over it. For a plain account of what users in research-use communities actually report, see the effects page.

Two molecules, one name

The first thing to know about TB-500 is that it is not the molecule that was studied. The literature people cite for TB-500 was almost entirely written about something else.

Thymosin Beta-4 — the parent peptide — is a 43-amino-acid intracellular protein encoded by the X-chromosome gene TMSB4X. It is one of the most abundant peptides in mammalian cells. It is the molecule that has been administered to rats with stroke, mice with diabetic neuropathy, pigs with cardiac ischemia, and adult human volunteers in two independent Phase I safety trials ^[11][12]. It is the molecule inside RGN-259, the topical 0.1% ophthalmic solution that reached Phase III in neurotrophic keratopathy with a statistically significant healing signal at day 43 ^[13].

TB-500 is a different object. It is a synthetic, N-acetylated 7-amino-acid peptide with sequence Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln-OH — the residues at positions 17–23 of the parent. It contains the LKKTET hexapeptide motif that mediates G-actin binding, which is the structural reason the fragment retains in-vitro affinity for monomeric actin. It does not contain the rest of the molecule.

No registered human clinical trial of the 7-AA synthetic fragment has ever been published. The widely cited '2–3 hour half-life' for TB-500 traces to vendor materials, not to peer-reviewed pharmacokinetic studies ^[22]. The translation from full-length Tβ4 biology to the synthetic heptapeptide is plausible for some endpoints — actin sequestration is preserved — and unresolved for others, especially the downstream cleavage product AcSDKP, which carries a meaningful share of the antifibrotic and pro-angiogenic activity that the literature attributes to 'Tβ4' ^[20].

Where the research has actually been done

Across roughly two decades, recombinant full-length Tβ4 has been administered to:

• Rats with controlled cortical impact traumatic brain injury (6 mg/kg IP every three days for five doses) — reduced hippocampal neuronal loss, increased angiogenesis and neurogenesis, durable sensorimotor and spatial-learning recovery through day 90 ^[1].
• Mice with experimental autoimmune encephalomyelitis and cuprizone-diet demyelination — daily IP dosing increased oligodendrocyte progenitor proliferation and mature myelinating oligodendrocyte counts, with new-OL density correlating with clinical recovery (r = 0.73, p < 0.05) ^[2].
• db/db type-II diabetic mice — 6 and 24 mg/kg IP restored sciatic-nerve vascular density and intraepidermal nerve fiber density, reversed axon-diameter and myelin-thickness deficits, and shifted angiopoietin-1 up and angiopoietin-2 down via PI3K/Akt signaling ^[3].
• Rats with mild compression spinal-cord injury — IP dosing at 30 minutes, three days, or five days post-injury improved BBB locomotor scores, preserved oligodendrocytes, raised myelin basic protein 57.8% above saline controls, and reduced lesion cavity area ^[4].
• Rats with embolic middle-cerebral-artery occlusion — a single 3.75 mg/kg IV dose at 24 hours produced durable adhesive-removal and modified Neurological Severity Score improvements from day 14 through day 56, without changing infarct volume ^[5].
• APP/PS1 Alzheimer-model mice challenged with systemic lipopolysaccharide — 5 mg/kg IV prevented LPS-induced amyloid plaque accumulation and attenuated sickness behavior ^[6].
• Pigs with closed-chest 90-minute ischemia / 24-hour reperfusion myocardial injury — 150 μg/kg IV plus maintenance did NOT reduce infarct size by TTC or MRI versus vehicle ^[23]. The pig negative result is one of the most important footnotes in this literature and is the reason any honest reading of Tβ4 has to distinguish rodent signal from large-mammal translation.

The TB-500 fragment has been detected, by LC-MS, in equine plasma and urine after intravenous dosing ^[22]. That is the published peer-reviewed dataset on the synthetic 7-AA molecule in living animals. Horse-racing was historically the first regulated domain in which TB-500 appeared as a controlled substance, and the analytical chemistry was built there before it was built anywhere else.

How to read this site

This site is structured as a small photographic catalog. Each section of each page is a 'plate' — a single editorial composition with a caption — and the reader is invited to look slowly. We have not tried to compress the record into a single number, a hero claim, or a recommendation. The record does not compress that way.

The Research page assembles the mechanism (G-actin sequestration via the LKKTET motif; AcSDKP cleavage by prolyl-oligopeptidase; NF-κB binding; angiopoietin-1 upregulation in endothelium and Schwann cells; oligodendrocyte progenitor differentiation; epicardial progenitor mobilization), then walks through the animal evidence in TBI, MS, peripheral neuropathy, spinal-cord injury, stroke, Alzheimer's, acute kidney injury, pulmonary fibrosis, and dermal and corneal wound-healing. The Dosage page summarizes the doses, routes, and pharmacokinetic envelope used in those studies, framed strictly as research context, never as a recommendation. The FAQ collects the questions people actually ask. The References page is the source table.

A second editorial point runs through all of it: Tβ4 biology is not uniformly regenerative. Conditional deletion of Tβ4 in hepatic stellate cells in a CCl4 mouse model reduced liver fibrosis ^[21] — direct evidence that Tβ4 plays a pro-fibrotic role in the hepatic compartment, opposite to its anti-fibrotic role in heart, kidney, and lung. Any framing that treats Tβ4 as universally pro-healing is incomplete.

The site does not sell anything, and there is no clinic behind it. The 'Dr.' in the name is an editorial position — a publisher's stance toward a body of research — and not a claim about practice. The About page makes that distinction explicit.

What the record supports and what it does not

Supported, with peer-reviewed citations: actin sequestration as a primary mechanism for full-length Tβ4 ^[16]; angiopoietin-1 upregulation and microvascular restoration in diabetic peripheral nerve ^[3]; oligodendrocyte progenitor proliferation and remyelination in MS models ^[2]; sustained sensorimotor recovery after rodent stroke without acute neuroprotection ^[5]; corneal re-epithelialization after alkali burn in mice ^[14] and in human Phase III neurotrophic keratopathy ^[13]; acute kidney injury attenuation in rats ^[8]; pulmonary fibrosis attenuation by inhaled rhTβ4 in mice ^[9]; acceptable Phase I IV safety in two independent human cohorts at single doses up to 1,260 mg ^[11] and at 0.05–25 μg/kg in Chinese volunteers ^[12].

Not supported by published primary literature: any human pharmacokinetic profile for the 7-AA TB-500 fragment; any human efficacy outcome for the synthetic fragment in any indication; any registered Phase II or Phase III trial of the synthetic fragment; reduction of myocardial infarct size in a large mammal (the porcine Phase III-equivalent translation negative ^[23]); the assumption that the 7-AA fragment releases AcSDKP via prolyl-oligopeptidase cleavage (this is mechanistically open and matters because AcSDKP carries a meaningful share of the antifibrotic activity attributed to Tβ4 ^[20]).

The distance between those two paragraphs is the editorial point of this site.