TB-500
A short synthetic peptide fragment derived from Thymosin Beta-4, researched in laboratory models for actin regulation and cellular migration.
TB-500 Biological Classification
A short synthetic peptide fragment derived from Thymosin Beta-4, researched in laboratory models for actin regulation and cellular migration.
Actin Sequestration
Binds actin monomers, preventing premature polymerization and keeping cells mobile.
Endothelial & Fibroblast Migration
Helps repair cells travel into damaged tissue to lay down new cellular matrix.
What is TB-500?
TB-500 is a synthetic peptide fragment that reproduces the active actin-binding site (amino acids 17 through 23: Ac-LKKTETQ) of the larger, naturally occurring human protein Thymosin Beta-4 (Tβ4).
Why are people interested in it?
Widely discussed in athletic and equine recovery circles for muscle repair, flexibility, tendon resilience, and recovery from acute injury. Often stacked with BPC-157.
Primary Research Categories
- Peptide fragments
- Thymosins
- Preclinical research compounds
How does it work in the body?
TB-500 interacts with actin, a key cellular protein that governs cell structure, flexibility, and migration. By sequestering actin, it promotes cell motility toward wounded tissue.
Molecular Interaction
Actin Sequestration & Cell Migration
Actin Cytoskeleton Remodeling
The Ac-LKKTETQ heptapeptide binds monomeric G-actin, preventing premature filament assembly and keeping a pool of actin ready for immediate cellular crawling and tissue repair.
Cellular Motility & Wound Closure
Facilitates rapid migration of keratinocytes, fibroblasts, and endothelial cells into tissue defects, accelerating re-epithelialization in laboratory wound assays.
Actin Sequestration
Binds actin monomers, preventing premature polymerization and keeping cells mobile.
Endothelial & Fibroblast Migration
Helps repair cells travel into damaged tissue to lay down new cellular matrix.
What has actually been demonstrated in humans?
There are no published human clinical trials for the synthetic fragment TB-500. Clinical trials in humans were conducted with the full-length 43-amino acid Thymosin Beta-4 protein (Timbetasin), not TB-500.
Pharmaceutical Reality vs. Unregulated Research Chemicals
TB-500 is not approved by the FDA for any indication. It is placed on the FDA Category 2 compounding restriction list and is banned by WADA under Category S2.
What is still uncertain or unknown?
TB-500 has zero human clinical trials. It is frequently marketed under misleading descriptions that cite studies performed on full-length Thymosin Beta-4 rather than the fragment itself.
Clinical Perspectives & Expert Discussions
Explore all perspectivesWhat identifiable clinicians, researchers, and professional bodies have publicly discussed regarding TB-500.
Dr. Brad Stanfield, MBChB
MBChB (University of Auckland School of Medicine); registered General Practitioner in New Zealand; clinical trial investigator and medical educator.
Dr. Stanfield provides critical appraisal of popular biohacking peptides (notably BPC-157, TB-500, and Epitalon), highlighting that the overwhelming majority of claims circulate on rodent and cell-culture data that have never been verified in rigorous human randomized controlled trials. He warns that online suppliers often sell unpurified chemicals with significant batch variability and unknown long-term human toxicity.
U.S. FDA Pharmacy Compounding Advisory Committee (PCAC)
Federal scientific advisory committee composed of physicians, toxicologists, pharmacologists, and compounding experts.
FDA briefing materials presented to the PCAC advised against including BPC-157 and TB-500 on the 503A bulks compounding list. FDA scientists highlighted serious safety concerns, including lack of human pharmacokinetic and exposure data, potential immunogenicity (formation of anti-drug antibodies), and the risk of uncharacterized peptide-related peptide impurities arising during complex chemical synthesis.
Dosing Reference
Open TB-500 Dosing ReferenceThe published human dose picture for the TB-500 fragment specifically is effectively empty: the wound-healing literature concerns full-length thymosin β4, a different molecule. Compound-specific confusion is the story here.
Therapept separates official product labels, published clinical study interventions, animal research, clinical references, and community-reported ranges — never blended into one number.
Research at a Glance
Open the full evidence file (6 records)6 records in this file
- ANIMAL1
- REVIEW2
- REGULATORY3
Publication span: 1999–2026
What Has Actually Been Studied
- FDA PCAC briefing — TB-500-related bulk drug substances (23 July 2026) (FDA PCAC briefing, 2026) — FDA advisory-committee briefing.
- FDA table of bulk drug substances nominated for compounding and subsequently withdrawn (FDA compounding communications, 2026) — Regulatory listing.
- Injectable peptide therapy: a primer for orthopaedic and sports medicine physicians (The American Journal of Sports Medicine, 2026) — Narrative review.
- Peptide supplements and their therapeutic applications in sports medicine (The American Journal of Sports Medicine, 2026) — Scoping review.
Plus 2 more records in the evidence file.
What is Still Unknown
What we know
- TB-500, as identified by FDA and PubChem, is the acetylated LKKTETQ heptapeptide, not full-length thymosin β-4 and not Ac-SDKP.
- Wound-healing papers commonly cited in vendor material are usually about full-length Tβ4. They are not TB-500 studies.
- FDA states it has not identified human exposure data. WADA lists “Thymosin-β4 and its derivatives e.g. TB-500”.
Editorial reading of the records below, labelled as Therapept analysis. How records are built
What remains uncertain
- Published human data on the fragment itself, as opposed to the parent protein.
- How often a certificate labelled “TB-500” describes LKKTETQ rather than another sequence.
Combinations and Stacks
- BPC-157 + TB-500
Discussed as a pairing of two compounds with connective-tissue research histories — BPC-157 for tendon, ligament, gut and muscle models; TB-500 as a fragment of thymosin β4, whose full-length parent has wound-healing literature.
Preparation and Handling
Lyophilized peptides ship as freeze-dried powders; whatever happens next involves diluents, concentrations and storage conditions that are compound- and product-specific.
United States Regulatory Status
No FDA-approved product
- No approved drug product exists in Drugs@FDA.
- Listed on FDA's table of bulk substances nominated for compounding and withdrawn by the nominator. FDA's published concerns include aggregation and immunogenicity risk, and FDA notes it has not identified human exposure data.
- On 23 July 2026 PCAC discussed TB-500 (free base) and TB-500 acetate (use evaluated: wound healing). FDA briefing materials proposed that they NOT be included on the 503A Bulks List. Nominations had been withdrawn; FDA elected to proceed. Committee recommendations are non-binding; FDA has not published a listing decision as of this review.
WADA Anti-Doping Status
Named at S2.3 — “Thymosin-β4 and its derivatives e.g. TB-500”. Prohibited at all times; non-Specified.
Technical Chemical SpecificationsClick to view CAS, sequence, and molecular formulas
- Molecular weight
- 889.0 g/mol
- Sequence length
- 13 chars
- CAS number
- 885340-08-9
- PubChem CID
- 62707662
- Compound class
- Synthetic acetylated heptapeptide corresponding to the actin-binding region of thymosin beta-4 (residues 17–23)
- Sequence
- Ac-LKKTETQ-OH
- Molecular formula
- C38H68N10O14
- Molecular weight
- 889.0 g/mol
- CAS number
- 885340-08-9
- PubChem CID
- 62707662
Sources
- PubChem CID 62707662
- PubChem CID 16132341 — Timbetasin (full-length thymosin beta-4)Cited for the distinction from the TB-500 fragment.
- FDA — Certain bulk drug substances for use in compounding may present significant safety risks
- FDA — Pharmacy Compounding Advisory Committee, 23–24 July 2026
- WADA 2026 Prohibited ListEffective 1 January 2026.
Last reviewed 12 September 2026 · Compiled by Therapept Editorial · How these records are built