TB-500 — Thymosin Beta-4 Fragment

Background

TB-500 is the marketing name for a synthetic peptide fragment derived from Thymosin Beta-4 (Tβ4), a 43-amino-acid actin-sequestering protein abundant in platelets and most mammalian tissues. The native Tβ4 protein is a well-established research target in regenerative medicine.

It is important to distinguish full-length Tβ4 (which has reached early-phase human trials for dermal and corneal wounds under the name RGN-259 and others) from the shorter TB-500 fragment sold in research markets — the literature on the two is not interchangeable.

Mechanism

Tβ4 binds G-actin monomers and regulates polymerisation, modulating cell migration, angiogenesis, and inflammation. Downstream effects in published work include AcSDKP-mediated antifibrotic activity, reduced inflammatory cytokine release, and stimulation of endothelial cell migration.

What is proven

Full-length Thymosin Beta-4 has demonstrated wound-healing acceleration in rodent dermal, corneal, and cardiac injury models with extensive replication. Phase 2 human trials of topical Tβ4 in dry-eye disease and venous stasis ulcers have published positive readouts.

Preclinical work on the shorter TB-500 fragment supports actin-regulatory activity and cell-migration effects consistent with the parent protein.

What is NOT proven

TB-500 (the fragment) has no completed Phase 2 or Phase 3 human efficacy trials. Claims of accelerated soft-tissue injury recovery, tendon repair, or anti-inflammatory benefit in athletes are extrapolations from rodent Tβ4 data — not from controlled human studies of the fragment itself.

Open research questions

Whether the truncated TB-500 sequence retains the full pharmacology of native Tβ4 in humans is not formally established. Long-term safety data in humans are absent.

Regulatory status

Not approved by any major regulator. Added to the WADA Prohibited List in 2011 — that prohibition reflects regulatory caution about its growth-factor activity, not a finding of proven performance enhancement in humans.

All Proteus® compounds are sold strictly for in-vitro research. Nothing on this page is medical advice, a treatment claim, or a recommendation for human use. Where compounds are licensed medicines in any jurisdiction, that approval applies to the licensed product supplied through a regulated pharmacy — not to research-grade material.