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Tissue repair

TB-500 / Thymosin beta-4

A genuine biological protein with real research history, and a separate online product that is not quite the same thing.

L2PreclinicalExperimental / researchUnclearVery low confidenceLast reviewed 2026-08-23
OphthalmicTopicalSC injection· unapproved

Also known as: TB4, Tβ4, thymosin beta-4 fragment

Evidence passport

Last reviewed 2026-08-23

Evidence level
L2Preclinical
Confidence
Very low confidence
Human efficacy
18/100
Human safety
20/100
Regulatory status
Experimental / research
Development
Unclear
Routes
OphthalmicTopicalSC injection· unapproved
Evidence base
Mostly preclinical
Furthest stage
Not established
Source curation
Sources fully curated
Clinical maturity
Preclinical for musculoskeletal claims; limited clinical study in narrow indications

Most of this evidence comes from animals and cells

The supporting research for TB-500 / Thymosin beta-4 is predominantly preclinical (Level 1–2). That is a legitimate starting point for science and a poor basis for personal decisions. Human results are not simply a scaled-up version of mouse results.

Overview

Human evidence18/100
Preclinical evidence72/100
Human safety evidence20/100

Clinical maturity: Preclinical for musculoskeletal claims; limited clinical study in narrow indications

Routes & formulations

Studied / approved routes

OphthalmicTopical

Marketed / research routes — never approved

SC injection· unapproved

Clinical study of thymosin beta-4 used ophthalmic and topical/dermal formulations in narrow indications. 'TB-500' sold online is typically an injectable fragment — an unapproved route and product with no controlled human evidence. Evidence for one route or molecule does not transfer to the other.

Route availability is not evidence of efficacy, and evidence from one route does not transfer to another. The Registry never provides dosing or sourcing information.

Peptide lifecycle

  1. Discovery

  2. Preclinical

  3. Phase I

  4. Phase II

  5. Phase III

  6. Approved

UnclearFurthest stage not established in our curated record

Thymosin beta-4 has been studied clinically in narrow ophthalmic and wound indications; there is no established development programme for the 'TB-500' fragment sold online.

What it is

Thymosin beta-4 is a naturally occurring actin-binding protein involved in cell migration and wound repair. 'TB-500' usually refers to a shorter synthetic fragment sold as a research chemical. The distinction matters and is routinely blurred in marketing.

What people claim

  • Accelerates soft-tissue and tendon healing
  • Reduces scar tissue
  • Improves flexibility and recovery in athletes

What the evidence actually says

Thymosin beta-4 has credible cell-biology and animal evidence for wound healing and cell migration, and has been studied clinically in narrow indications such as dry eye and certain wounds. Controlled human evidence for sports injury recovery — the reason most people search for it — does not exist.

Human evidence

  • Clinical studies of thymosin beta-4 in specific ophthalmic and dermal wound indications; not translatable to tendon-repair marketing.
  • No controlled human trials supporting athletic injury-recovery claims for TB-500.

Preclinical evidence

  • Animal models of cardiac, dermal and corneal repair.
  • Cell studies of actin sequestration, migration and angiogenesis.

Animal and cell findings are Level 1–2 evidence.

Mechanism and pathways

  • Binds G-actin, regulating cytoskeletal dynamics and cell migration.
  • Promotes endothelial cell migration and angiogenesis.
  • Modulates inflammatory signalling in injury models.

Safety and unknowns

  • No systematic human safety dataset for the injectable research-chemical form.
  • Banned by anti-doping authorities; a positive test carries real consequences.
  • Unapproved supply quality is a distinct risk from the molecule's own pharmacology.

Cancer relevance

Theoretical / mechanistic concern only

Thymosin beta-4 promotes angiogenesis and cell migration, and elevated expression has been described in some tumour contexts. That is a mechanistic and observational concern worth naming honestly; it is not proof that administering it causes cancer in humans. There is no human evidence either way.

Regulatory status

Not an approved medicine for injury recovery. Thymosin beta-4 has been studied clinically in specific ophthalmic and wound contexts; 'TB-500' as sold online is typically a synthetic fragment marketed outside medical supply. The FDA's 503A Category 2 list flags thymosin beta-4 fragments as a compounding safety concern. It is also prohibited in sport.

Evidence grade

L2PreclinicalVery low confidence

Animal, organoid or tissue studies. Mice are not tiny humans.

What would change our rating?

  • Controlled human trials in musculoskeletal injury.
  • Human safety and pharmacokinetic data for the fragment actually sold as TB-500.

References and sources

Sources fully curated

Source hierarchy: regulatory documents and trial registries first, peer-reviewed work next, sponsor material flagged as non-independent. We never use supplier or clinic marketing as evidence, and where a verified source has not yet been curated we say so rather than inventing one.

Evidence change history

No recorded changes yet. Baseline position set on 2026-08-23.

Related claims we’ve checked

Partly supportedL2PreclinicalTissue repair

“TB-500 and thymosin beta-4 are the same thing.”

Partly supported — related, but not interchangeable, and marketing blurs it deliberately.

  • Thymosin beta-4 is the full naturally occurring protein with a genuine research history.
  • 'TB-500' typically denotes a shorter synthetic fragment sold as a research chemical.
  • Citing thymosin beta-4 clinical work to sell TB-500 for tendon repair is a category error.
Last reviewed 2026-07-10Compound profile