Now reading Entry 088 / 102 Last revised Sep 28, 2026 39 sources 1 comparisons Methodology →
A specimen of the Repair & Recovery drawer Drawer B · Repair & Recovery

TB-500

Research Only

TB-500 commonly denotes N-acetyl-LKKTETQ, a seven-residue fragment of thymosin beta-4. Full-length thymosin beta-4 trial results do not establish this fragment's efficacy or safety. No human TB-500 exposure data were identified in FDA's compounding review.

Thymosin Beta-4 Fragment · TB4-FRAG

Research evidence
Very Low

No established human efficacy for TB-500 in these sources; clinical trials listed below concern parent thymosin beta-4.

Preclinical
5%
Human research
0%

Based on 39 cited sources

39 visible records: 18 publications, 19 registrations for parent thymosin beta-4, and two FDA records. The two direct preclinical papers do not establish therapeutic efficacy of TB-500. Registrations, reviews and parent-compound papers are excluded from the direct human/preclinical buckets.

!!
Evidence Level
very low
Not currently in FDA's Category 2; FDA records the nomination of "Thymosin beta-4, fragment (LKKTETQ), also known as TB-500" as withdrawn by the nominator (FDA, "Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks"; page content curren…
Research Only
Identity
SCALE · 1:1 N-TERMINUS C-TERMINUS 7 AA · 889.01 Da (N-acetylated free base)
Also Known As
Thymosin Beta-4 Fragment • TB4-FRAG
Class
N-acetylated heptapeptide fragment of thymosin beta-4
Length
7 amino acids
Mol. weight
889.01 Da (N-acetylated free base)
Sequence
Ac-LKKTETQ
Molecular Structure
L
K
K
T
E
T
Q
Hydrophobic
Polar
Positive
Negative

TB-500 commonly refers to N-acetyl-LKKTETQ, the seven-residue segment corresponding to thymosin beta-4 residues 17–23. FDA’s 2026 substance review gives the free-base mass as 889.01 Da and warns that the name has also been used for different salts and active moieties. Full-length thymosin beta-4 is a distinct 43-residue molecule; results from its wound, cardiac, corneal and neurologic experiments cannot be assigned to TB-500. FDA identity review

What the fragment research shows

A 2012 analytical study identified N-acetyl-LKKTETQ in a veterinary preparation and detected it and its metabolites in equine samples. It was a detection study, not evidence of tissue repair in people. In a 2024 metabolism and fibroblast scratch-assay study, the Ac-LKKTE metabolite, rather than parent TB-500, showed statistically significant wound-healing activity against control. That result is limited to the assay and does not establish clinical efficacy or the full parent protein’s mechanisms for TB-500. PMID:23084823 · PMID:38382158

Full-length thymosin beta-4 has a larger preclinical literature. For example, Bock-Marquette et al. studied cardiac repair pathways in mice; those ILK/Akt results concern the parent molecule. RGN-259 is a full-length thymosin beta-4 ophthalmic development program, not a TB-500 trial. Its small published corneal phase 3 study did not reach the primary endpoint. These studies help explain scientific interest in the parent protein but remain indirect for Ac-LKKTETQ. PMID:15565145 · PMID:36613994

Evidence and safety boundary

No controlled human efficacy study of Ac-LKKTETQ was identified. FDA says it has identified no human exposure data for drug products containing the fragment and cites potential immunogenicity from aggregation and peptide-related impurities in compounded products. Its interaction and combination effects with other peptides are unknown. FDA compounding safety review

i. Actin-Binding Pathway · Cell Migration
Full-length thymosin beta-4 (contains LKKTETQ motif)G-actin binding in parent-protein researchPrevents polymerizationCytoskeletal reorganizationCell migration in parent-protein models
ii. ILK-Akt Pathway · Cell Survival
Full-length thymosin beta-4ILK activationAkt phosphorylationBcl-2Cell survival in parent-protein models
NCT ID Title Peptide Phase Status Completion
NCT00832091
Parent thymosin beta-4 (not TB-500): Study of Thymosin Beta 4 in Patients With Venous Stasis Ulcers
Venous Stasis Ulcers
Thymosin beta-4 (parent; not TB-500) Phase 2 Completed Jan 2009
NCT01387347
Parent thymosin beta-4 (not TB-500): Safety and Efficacy of Thymosin Beta 4 Ophthalmic Solution in Patients With Dry Eye
Dry Eye Syndrome, Dry Eye
Thymosin beta-4 (parent; not TB-500) Phase 2 Completed Dec 2011
NCT01311518
Parent thymosin beta-4 (not TB-500): A Study of the Safety and Efficacy of Injectable Thymosin Beta 4 for Treating Acute Myocardial Infarction
Acute Myocardial Infarction, ST Elevation Myocardial Infarction +1 more
Thymosin beta-4 (parent; not TB-500) Phase 2 Withdrawn Jul 2020 (estimated)
NCT07586865
Parent thymosin beta-4 (not TB-500): Recombinant Human Thymosin Beta 4 for Injection(NL005) for Acute Myocardial Infarction
Acute Myocardial Infarction (AMI), Acute Myocardial Infarction of Anterior Wall +3 more
Thymosin beta-4 (parent; not TB-500) Phase 2 Not yet recruiting May 2028 (estimated)
NCT05555589
Parent thymosin beta-4 (not TB-500): Assessment of the Safety and Efficacy of 0.1% RGN-259 Ophthalmic Solution for the Treatment of NK: SEER-2
Neurotrophic Keratopathy
Thymosin beta-4 (parent; not TB-500) Phase 3 Recruiting May 2026 (estimated)
NCT05984134
Parent thymosin beta-4 (not TB-500): Efficacy and Safety Study of Thymosin Beta 4 in Patients With Acute Myocardial Infarction
Acute Myocardial Infarction
Thymosin beta-4 (parent; not TB-500) Phase 2 Completed May 2023
NCT05485818
Parent thymosin beta-4 (not TB-500): Safety and Efficacy Study of Thymosin Beta 4 in Patients With Acute Myocardial Infarction.Infarction
Acute Myocardial Infarction
Thymosin beta-4 (parent; not TB-500) Phase 2 Completed Nov 2021
NCT03937882
Parent thymosin beta-4 (not TB-500): Assessment of the Safety and Efficacy of RGN-259 Ophthalmic Solutions for Dry Eye Syndrome: ARISE-3
Dry Eye Syndromes, Dry Eye
Thymosin beta-4 (parent; not TB-500) Phase 3 Completed Oct 2021
NCT04555850
Parent thymosin beta-4 (not TB-500): A Phase 1b Study of Thymosin Beta 4 in Healthy Volunteers
Healthy
Thymosin beta-4 (parent; not TB-500) Phase 1 Completed Jul 2019
NCT04555824
Parent thymosin beta-4 (not TB-500): A Phase 1a Study of Thymosin Beta 4 in Healthy Volunteers
Healthy
Thymosin beta-4 (parent; not TB-500) Phase 1 Completed Jun 2018
NCT02974907
Parent thymosin beta-4 (not TB-500): Assessment of the Safety and Efficacy of RGN-259 Ophthalmic Solutions for Dry Eye Syndrome : ARISE-2
Dry Eye Syndrome
Thymosin beta-4 (parent; not TB-500) Phase 3 Completed Mar 2018
NCT02600429
Parent thymosin beta-4 (not TB-500): Assessment of the Safety and Efficacy Study of RGN-259 Ophthalmic Solutions for Neurotrophic Keratopathy : SEER-1
Neurotrophic Keratopathy
Thymosin beta-4 (parent; not TB-500) Phase 3 Terminated Mar 2020
NCT02597803
Parent thymosin beta-4 (not TB-500): Assessment of the Safety and Efficacy of RGN-259 Ophthalmic Solutions for Dry Eye Syndrome: ARISE-1
Dry Eye Syndrome
Thymosin beta-4 (parent; not TB-500) Phase 2/3 Completed Jul 2016
NCT02668055
TB4-labelled scaffold (exact construct unverified; not evidence for Ac-LKKTETQ): Slow-release Tb4 Collagen and Chitosan Porous Sponge Scaffolds Skin Substitute Treatment is Difficult to Heal Wounds
Wounds
TB4-labelled scaffold (identity unverified) Phase 1 Completed Dec 2015
NCT01393132
Parent thymosin beta-4 (not TB-500): Comparative Study of Thymosin Beta 4 Eye Drops vs. Vehicle in the Treatment of Severe Dry Eye
Dry Eye, Sjogren's Syndrome +1 more
Thymosin beta-4 (parent; not TB-500) Phase 2 Completed Dec 2012
NCT00743769
Parent thymosin beta-4 (not TB-500): A Phase 1 Safety Study of the Intravenous Administration of Thymosin Beta in Healthy Volunteers
Myocardial Infarction, Myocardial Ischemia
Thymosin beta-4 (parent; not TB-500) Phase 1 Withdrawn Jan 2017
NCT00598871
Parent thymosin beta-4 (not TB-500): A Phase 2 Study of the Safety and Efficacy of Thymosin Beta 4 for Treating Corneal Wounds
Diabetes
Thymosin beta-4 (parent; not TB-500) Phase 2 Terminated Feb 2009
NCT00382174
Parent thymosin beta-4 (not TB-500): Study of Thymosin Beta 4 in Patients With Pressure Ulcers
Pressure Ulcers
Thymosin beta-4 (parent; not TB-500) Phase 2 Completed Dec 2008
NCT00311766
Parent thymosin beta-4 (not TB-500): A Phase 2 Study on Effect of Thymosin Beta 4 on Wound Healing in Patients With Epidermolysis Bullosa
Epidermolysis Bullosa
Thymosin beta-4 (parent; not TB-500) Phase 2 Terminated Nov 2012
NCT00832091 Completed

Parent thymosin beta-4 (not TB-500): Study of Thymosin Beta 4 in Patients With Venous Stasis Ulcers

Thymosin beta-4 (parent; not TB-500) Phase 2 Completion: Jan 2009
NCT01387347 Completed

Parent thymosin beta-4 (not TB-500): Safety and Efficacy of Thymosin Beta 4 Ophthalmic Solution in Patients With Dry Eye

Thymosin beta-4 (parent; not TB-500) Phase 2 Completion: Dec 2011
NCT01311518 Withdrawn

Parent thymosin beta-4 (not TB-500): A Study of the Safety and Efficacy of Injectable Thymosin Beta 4 for Treating Acute Myocardial Infarction

Thymosin beta-4 (parent; not TB-500) Phase 2 Completion: Jul 2020 (estimated)
NCT07586865 Not yet recruiting

Parent thymosin beta-4 (not TB-500): Recombinant Human Thymosin Beta 4 for Injection(NL005) for Acute Myocardial Infarction

Thymosin beta-4 (parent; not TB-500) Phase 2 Completion: May 2028 (estimated)
NCT05555589 Recruiting

Parent thymosin beta-4 (not TB-500): Assessment of the Safety and Efficacy of 0.1% RGN-259 Ophthalmic Solution for the Treatment of NK: SEER-2

Thymosin beta-4 (parent; not TB-500) Phase 3 Completion: May 2026 (estimated)
NCT05984134 Completed

Parent thymosin beta-4 (not TB-500): Efficacy and Safety Study of Thymosin Beta 4 in Patients With Acute Myocardial Infarction

Thymosin beta-4 (parent; not TB-500) Phase 2 Completion: May 2023
NCT05485818 Completed

Parent thymosin beta-4 (not TB-500): Safety and Efficacy Study of Thymosin Beta 4 in Patients With Acute Myocardial Infarction.Infarction

Thymosin beta-4 (parent; not TB-500) Phase 2 Completion: Nov 2021
NCT03937882 Completed

Parent thymosin beta-4 (not TB-500): Assessment of the Safety and Efficacy of RGN-259 Ophthalmic Solutions for Dry Eye Syndrome: ARISE-3

Thymosin beta-4 (parent; not TB-500) Phase 3 Completion: Oct 2021
NCT04555850 Completed

Parent thymosin beta-4 (not TB-500): A Phase 1b Study of Thymosin Beta 4 in Healthy Volunteers

Thymosin beta-4 (parent; not TB-500) Phase 1 Completion: Jul 2019
NCT04555824 Completed

Parent thymosin beta-4 (not TB-500): A Phase 1a Study of Thymosin Beta 4 in Healthy Volunteers

Thymosin beta-4 (parent; not TB-500) Phase 1 Completion: Jun 2018
NCT02974907 Completed

Parent thymosin beta-4 (not TB-500): Assessment of the Safety and Efficacy of RGN-259 Ophthalmic Solutions for Dry Eye Syndrome : ARISE-2

Thymosin beta-4 (parent; not TB-500) Phase 3 Completion: Mar 2018
NCT02600429 Terminated

Parent thymosin beta-4 (not TB-500): Assessment of the Safety and Efficacy Study of RGN-259 Ophthalmic Solutions for Neurotrophic Keratopathy : SEER-1

Thymosin beta-4 (parent; not TB-500) Phase 3 Completion: Mar 2020
NCT02597803 Completed

Parent thymosin beta-4 (not TB-500): Assessment of the Safety and Efficacy of RGN-259 Ophthalmic Solutions for Dry Eye Syndrome: ARISE-1

Thymosin beta-4 (parent; not TB-500) Phase 2/3 Completion: Jul 2016
NCT02668055 Completed

TB4-labelled scaffold (exact construct unverified; not evidence for Ac-LKKTETQ): Slow-release Tb4 Collagen and Chitosan Porous Sponge Scaffolds Skin Substitute Treatment is Difficult to Heal Wounds

TB4-labelled scaffold (identity unverified) Phase 1 Completion: Dec 2015
NCT01393132 Completed

Parent thymosin beta-4 (not TB-500): Comparative Study of Thymosin Beta 4 Eye Drops vs. Vehicle in the Treatment of Severe Dry Eye

Thymosin beta-4 (parent; not TB-500) Phase 2 Completion: Dec 2012
NCT00743769 Withdrawn

Parent thymosin beta-4 (not TB-500): A Phase 1 Safety Study of the Intravenous Administration of Thymosin Beta in Healthy Volunteers

Thymosin beta-4 (parent; not TB-500) Phase 1 Completion: Jan 2017
NCT00598871 Terminated

Parent thymosin beta-4 (not TB-500): A Phase 2 Study of the Safety and Efficacy of Thymosin Beta 4 for Treating Corneal Wounds

Thymosin beta-4 (parent; not TB-500) Phase 2 Completion: Feb 2009
NCT00382174 Completed

Parent thymosin beta-4 (not TB-500): Study of Thymosin Beta 4 in Patients With Pressure Ulcers

Thymosin beta-4 (parent; not TB-500) Phase 2 Completion: Dec 2008
NCT00311766 Terminated

Parent thymosin beta-4 (not TB-500): A Phase 2 Study on Effect of Thymosin Beta 4 on Wound Healing in Patients With Epidermolysis Bullosa

Thymosin beta-4 (parent; not TB-500) Phase 2 Completion: Nov 2012
39 Sources 0 Human 2 Preclinical

Use the source links in the research discussion above to inspect the referenced records.

This dossier synthesizes available evidence from peer-reviewed literature, regulatory documents, and clinical trial registries. Evidence strength labels summarize the cited material for this entry and should be read alongside its population, model, and study limitations.

For complete methodology details, see our Methodology page.

Important Disclaimer

This dossier is for educational purposes only and does not constitute medical advice. Always consult a qualified healthcare provider before making health decisions.

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Compare TB-500

TB-500 vs BPC-157
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Safety profile TB-500: adverse events, contraindications and monitoring →

Compared With

6 comparisons

Conditions Studied

7 entries

Related Content

Peptide

BPC-157

Repair & Recovery · low evidence

Guide

What is TB-500?

An introduction to TB-500, a fragment of thymosin beta-4 mar...

Comparison

BPC-157 vs GHK-Cu vs TB-500

View side-by-side analysis

Comparison

BPC-157 vs TB-500

View side-by-side analysis