Synthetic acetylated heptapeptide corresponding to the actin-binding region of thymosin beta-4 (residues 17–23)
TB-500
An acetylated heptapeptide fragment of thymosin beta-4. It is frequently confused with two different substances — full-length thymosin beta-4, and the unrelated Ac-SDKP fragment — which are chemically distinct.
Also listed as: Thymosin beta-4 fragment (LKKTETQ), Ac-LKKTETQ-OH, TB500
Chemical identity
- 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
- Research categories
- Peptide fragments, Preclinical research compounds
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- Listed on FDA's table of bulk substances nominated for compounding and withdrawn by the nominator.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.
- Considered at FDA's Pharmacy Compounding Advisory Committee meeting of 23 July 2026. No vote outcome had been published at the time of review.
Anti-doping status
Named at S2.3 — “Thymosin-β4 and its derivatives e.g. TB-500”. Prohibited at all times; non-Specified.
Regulatory status describes how a substance is classified. It is not a safety assessment, and it says nothing about the quality of any particular material.
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
- WADA 2026 Prohibited ListEffective 1 January 2026.
Last reviewed 3 September 2026 · Compiled by Therapept Editorial · How these records are built