Thymosin Beta-4 (TB-500)

Thymosin beta 4 · Thymosin beta4 · Thymosin beta-4 · TB-500

Snapshot

Indications	Contraindications
Moderate to severe dry eye¹ Severe dry eye² Venous leg ulcers³ Myocardial infarction, investigational⁴	Tested competitive athletes⁵

Thymosin beta-4 (Tβ4) is a naturally occurring 43-amino acid peptide thought to support tissue repair by promoting cell migration, new vessel growth, and collagen deposition³. TB-500 is the name used for a synthetic fragment of it, thymosin beta-4 fragment (LKKTETQ)⁵. The United States (US) Food and Drug Administration (FDA) previously placed that fragment in a compounding category for significant safety risks until nominators withdrew it⁵, and the World Anti-Doping Agency (WADA) prohibits it at all times⁵. Clinical research on full-length Tβ4 has addressed dry eye^{1, 2}, venous leg ulcers³, and, in early safety work, acute myocardial infarction⁶.

Evidence comes from full-length Tβ4, not TB-500.¹ In dry eye, a placebo-controlled phase 2 trial missed both primary endpoints but improved several secondary measures, and a small trial in severe dry eye reported symptom and sign gains. An FDA review for its 2026 compounding advisory committee noted a lack of evidence on TB-500 effectiveness⁷. A 2021 first-in-human randomized trial of intravenous recombinant Tβ4 in healthy volunteers found it well tolerated across single and repeated administration; it tested tolerability, not efficacy⁶. Six products list thymosin beta-4 in US supplement label records; see Form comparison.

The FDA's stated concern is immunogenicity of injected peptide, from aggregation and peptide-related impurities, and it reports no human exposure data for TB-500 products⁵.

Last updated October 17, 2026. Read how we make monographs.

In the full monograph

31 sources, 16 studies

When to useThe situations practitioners use it for, each with the reason and the study behind it.
SafetyWho should avoid it, who needs extra care, and the side effects reported in studies.
Protocol notesThe doses used in studies, how and when they were taken, and how the forms on the market compare.
How it worksWhat it is and how it works in the body, in plain terms.
Published studiesThe studies behind each use, popular claims checked against them, and trials still under way.
Word of mouthWhat patients and practitioners report online, kept separate from the clinical evidence.
Clinical perspectiveA closing read of where the evidence is solid, where it is thin, and what has not been studied.

Snapshot

In the full monograph

Sources