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Thymosin beta-4

Also identified as Tβ4, Thymosin β4, TB-4

43-residue actin-binding peptide

CAS
77642-24-1
Published studies reviewed
3

CAS number sources: U.S. FDA Global Substance Registration System (GSRS), Thymosin β-4, UNII 549LM7U24W. UNII 549LM7U24W; U.S. National Library of Medicine, ChemIDplus record for Thymosin beta-4, as deposited in PubChem (Substance SID 381122663). PubChem SID 381122663

FOR RESEARCH USE ONLY. NOT FOR HUMAN OR VETERINARY USE. NOT FOR HUMAN CONSUMPTION.

Compounds described on this site are supplied solely for laboratory research. They are not offered for human or veterinary use or for clinical use, and they are not intended to diagnose, mitigate, cure or prevent any disease.

Thymosin beta-4 is a naturally occurring 43-residue peptide, and this page covers the full-length molecule rather than the seven-residue TB-500 fragment. Three publications are reviewed: a 1991 laboratory study in which it bound actin monomers one-to-one, a 2010 randomised, placebo-controlled study in healthy volunteers that reported safety and pharmacokinetics only, and a 2007 study-design report with no outcome figures. None of them establishes what the peptide does in a person, and no finding here carries over to TB-500.

At a glance

Also identified as
Tβ4, Thymosin β4, TB-4
Class
43-residue actin-binding peptide
Target or mechanism
G-actin (actin monomers)
Evidence types represented
in vitro, human
Published studies reviewed
3
Last reviewed
2026-09-26

Overview

Thymosin beta-4 is a 43-residue peptide that occurs naturally and is described in the literature as binding actin. A 1991 study found that the main actin-binding peptide of human platelets had the same complete sequence as thymosin beta-4, and that the peptide forms a one-to-one complex with actin monomers and inhibits their polymerisation — laboratory biochemistry, not a study in a person.

Two human publications are collected here. The first, from 2010, is a randomised, placebo-controlled study in healthy volunteers: four cohorts of ten, each given synthetic Tβ4 once and then, after a safety review, repeatedly over 14 days. What it reports is safety and pharmacokinetics, and nothing else. The second, from 2007, describes the design of a study in venous ulcers; at the time of writing it was still enrolling, and it reports no outcome figures.

This page is not about TB-500. TB-500 is the acetylated fragment Ac-LKKTETQ — seven residues, with its own registry number and molecular formula. The publications here studied the full-length 43-residue peptide. Whether a finding about one applies to the other is not established by anything on this page, and this page does not link to a research material for that reason: the compound these studies used is not a material PepGenex supplies.

Mechanism under investigation

Thymosin beta-4
Actin-binding peptide
  • G-actin (actin monomers)

A 1991 in-vitro study reports that thymosin beta-4 forms a 1:1 complex with actin monomers and inhibits their polymerisation. The human publications measured safety and pharmacokinetics, or described a study design, rather than mechanism.

Scope of the published work

Areas investigated
  • Safety and tolerability
  • Pharmacokinetics
  • Venous ulcer study design
Models used
  • Purified peptide with actin (in vitro)
  • Randomised study in healthy volunteers
  • Randomised study protocol

The only completed human study recorded here measured safety and pharmacokinetics in healthy volunteers; it supports no statement about what the compound does. The second publication reports a study design and no results. These studies used full-length thymosin beta-4, not the TB-500 fragment, and no finding here transfers to that material or to any material PepGenex supplies.

Limitations

Evidence represented on this page: in vitro and human. No animal research is represented. The page reviews 3 published studies, and each figure is reported for the study that published it; results are not pooled across studies.

Common questions

What is Thymosin beta-4?

Thymosin beta-4 is a 43-residue peptide that occurs naturally and is described in the literature as binding actin.

How does Thymosin beta-4 work, according to the published research?

A 1991 in-vitro study reports that thymosin beta-4 forms a 1:1 complex with actin monomers and inhibits their polymerisation. The human publications measured safety and pharmacokinetics, or described a study design, rather than mechanism.

  • Authentic thymosin beta-4 was functionally equivalent to Fx: it formed a 1:1 complex with actin monomers and inhibited their polymerisation. The authors state that its widespread distribution and high intracellular concentration strongly suggest a significant role in regulating actin polymerisation in many cell types. (Safer et al., 1991, PMID 1999398)

What has published research on Thymosin beta-4 found, and what are its limits?

This page records 3 publications, reporting laboratory (in vitro) work in 1, human work in 2. Each is listed with its identifier under References.

Human studies represented: Guarnera et al., 2007, PMID 17495250; Ruff et al., 2010, PMID 20536472.

Evidence represented on this page: in vitro and human.

No animal research is represented.

The page reviews 3 published studies, and each figure is reported for the study that published it; results are not pooled across studies.

The only completed human study recorded here measured safety and pharmacokinetics in healthy volunteers; it supports no statement about what the compound does. The second publication reports a study design and no results. These studies used full-length thymosin beta-4, not the TB-500 fragment, and no finding here transfers to that material or to any material PepGenex supplies.

Is Thymosin beta-4 approved by the U.S. FDA?

This page cites no FDA approval record for Thymosin beta-4; PepGenex Science states a U.S. regulatory status only where a sourced record exists.

PepGenex research materials are not FDA approved and are not for human or veterinary use.

What risks have published studies of Thymosin beta-4 reported?

1 published human study on this page reports adverse events or safety measurements. Each is listed with its publication in the adverse-events section of this page.

Trial events do not establish a complete safety profile.

What adverse events have been reported in published studies of Thymosin beta-4?

Adverse events and safety measurements as reported by the published human studies on this page. Each entry is attributed to its publication.

Ruff et al., 2010, PMID 20536472

Design and population
Randomised, placebo-controlled study in four cohorts of ten healthy volunteers. Each cohort received synthetic thymosin beta-4 or placebo once and, following a safety review, repeatedly over 14 days.
Events reported
Adverse events were infrequent and mild or moderate in intensity. There were no amount-limiting toxicities and no serious adverse events across the range studied.

Trial events do not establish a complete safety profile.

Published research

Grouped by the kind of study. Select one to narrow what is shown below.

Laboratory (in vitro)(1)

Laboratory (in vitro)

Thymosin beta 4 and Fx, an actin-sequestering peptide, are indistinguishable

Safer D, Elzinga M, Nachmias VT, The Journal of Biological Chemistry, 1991;266(7):4029-4032

published

  • Fx — an acidic, heat-stable 5-kDa peptide found complexed with the bulk of the unpolymerised actin in resting human platelets — was sequenced in full, and its complete amino acid sequence was found to be identical with that of thymosin beta-4.
  • Authentic thymosin beta-4 was functionally equivalent to Fx: it formed a 1:1 complex with actin monomers and inhibited their polymerisation. The authors state that its widespread distribution and high intracellular concentration strongly suggest a significant role in regulating actin polymerisation in many cell types.
View publication →

Human study (phase not stated)(1)

Human study (phase not stated)

Thymosin beta-4 and venous ulcers: clinical remarks on a European prospective, randomized study on safety, tolerability, and enhancement on healing

Guarnera G, De Rosa A, Camerini R, Annals of the New York Academy of Sciences, 2007;1112:407-412

published

Design report for a double-blind, placebo-controlled, amount-escalation study in venous ulcers across ten sites in Italy and Poland: three sequential groups of 24 participants randomised 3:1 to thymosin beta-4 or to placebo, 72 participants in total, followed for 84 days with a 14-day follow-up.

  • This publication reports no outcome figures. At the time it was written the study was still enrolling, with 21 participants in the first group, and it describes the planned measures rather than any result obtained from them.
Context

This entry is a study design, kept because knowing that a trial was planned and what it intended to measure is worth something — and because a citation that looks like a results paper, but is not one, is exactly the kind of record that acquires figures it never contained.

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Human phase 1(1)

Human phase 1n = 40

A randomized, placebo-controlled, single and multiple dose study of intravenous thymosin beta4 in healthy volunteers

Ruff D, Crockford D, Girardi G, Zhang Y, Annals of the New York Academy of Sciences, 2010;1194:223-229

published

Randomised, placebo-controlled study in four cohorts of ten healthy volunteers. Each cohort received synthetic thymosin beta-4 or placebo once and, following a safety review, repeatedly over 14 days.

  • Adverse events were infrequent and mild or moderate in intensity. There were no amount-limiting toxicities and no serious adverse events across the range studied.
  • The single-amount pharmacokinetic profile was proportional to the amount given, with half-life increasing as the amount increased.
Limitations

A safety and pharmacokinetic study answers one question: what happened to the people given the compound, and what the compound did in their blood. It was not designed to detect an effect on anything, and an absence of harm at the highest amount tested is not evidence of benefit at any amount.

View publication →

Compared with related compounds

Classification, structure, recorded targets, evidence types and FDA status only, each read from the two compounds' own pages. These comparisons do not compare study results.

Thymosin beta-4 and TB-500

Parent and fragment: TB-500 is a seven-residue acetylated fragment of thymosin beta-4. They are different molecules.

Thymosin beta-4TB-500
Classification43-residue actin-binding peptideAcetylated thymosin beta-4 fragment (Ac-LKKTETQ)
StructureNot recorded on its pageSequence Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln; formula C38H68N10O14
Targets recordedG-actin (actin monomers)Actin (the thymosin beta-4 actin-binding site, residues 17 to 23)
Evidence types representedin vitro, humanin vitro, animal
Status with the U.S. FDANot shown (no Drugs@FDA application record verified for this page)Not shown (no Drugs@FDA application record verified for this page)

References

Published studies reviewed (3)

  1. A randomized, placebo-controlled, single and multiple dose study of intravenous thymosin beta4 in healthy volunteers — Ruff D, Crockford D, Girardi G, Zhang Y, Annals of the New York Academy of Sciences, 2010;1194:223-229
    DOI 10.1111/j.1749-6632.2010.05474.x · PMID 20536472
  2. Thymosin beta-4 and venous ulcers: clinical remarks on a European prospective, randomized study on safety, tolerability, and enhancement on healing — Guarnera G, De Rosa A, Camerini R, Annals of the New York Academy of Sciences, 2007;1112:407-412
    DOI 10.1196/annals.1415.003 · PMID 17495250
  3. Thymosin beta 4 and Fx, an actin-sequestering peptide, are indistinguishable — Safer D, Elzinga M, Nachmias VT, The Journal of Biological Chemistry, 1991;266(7):4029-4032
    DOI 10.1016/s0021-9258(20)64278-8 · PMID 1999398

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