Peptide research

TB-500 Peptide: Matching a Listing Name to FDA, PubChem and WADA Records

Romio

— 2 min read
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TB-500 peptide listings rarely agree on what the name covers. This note walks through the public records that tie the name to a specific molecule and shows what each record confirms. The TB-500 peptide guide gives the same material question by question.

Step 1: the sequence

The reference sequence is N-acetyl-Leu-Lys-Lys-Thr-Glu-Thr-Gln, seven amino acids. PubChem holds it as CID 62707662, with the formula C38H68N10O14 and a molecular weight of 889.0 g/mol. FDA's Substance Registration System holds the same molecule as UNII QHK6Z47GTG, preferred name TB-500, and lists the N-terminal acetylated 17-23 fragment of thymosin beta 4 among its mappings. Sources: PubChem record for TB-500 and FDA UNII record for TB-500.

Step 2: the neighbors

Two other records sit close to TB-500 and are easy to confuse with it. Thymosin beta-4, the protein from which TB-500 was copied, has its own UNII and 43 amino acids. The acetate form of TB-500 appears in FDA's 2026 briefing document with a different formula and weight. The list keeps them apart.

  • PubChem CID 62707662: TB-500. C38H68N10O14, 889.0 g/mol.
  • FDA UNII QHK6Z47GTG: TB-500. CAS 885340-08-9.
  • FDA UNII 549LM7U24W: thymosin beta-4. 43 amino acids.
  • FDA briefing, Table 1: TB-500 acetate. C38H68N10O14·CH3COOH, 949.1 g/mol.

Sources: PubChem, FDA UNII for TB-500, FDA UNII for thymosin beta-4 and the FDA briefing document.

Step 3: the printed CAS number

A CAS number looks like proof of identity, and FDA's briefing shows why it is not always one. A footnote to its comparison table states: "On several suppliers' websites, the CAS number for TB-500 (free base) (885340-08-9) is used for TB-500 Acetate." A listing that pairs that number with the acetate's weight gives two records that do not match.

Step 4: the sport list

The WADA Prohibited List names "Thymosin-ß4 and its derivatives e.g. TB-500" in section S2.3. The entry names a substance family and gives no sequence, so the entry alone does not say which molecule a listing contains. WADA's research page for a 2013 TB-500 project records that the original product was presented without an amino acid sequence or molecular weight. Sources: WADA 2026 Prohibited List and WADA project page.

Step 5: the lot

Records name molecules, and a lot report describes a vial. FDA's briefing reviewed a representative public certificate for TB-500 (free base) and reported that it covered appearance, identity and purity, while assay, impurities, bacterial endotoxins and aggregates were not tested or controlled. The TB-500 for sale listing checks go through the report fields. One supplier defines its fields on Curo's testing page, publishes lot reports in Curo's lot-certificate library and lists the 5 mg material as Curo's TB-500 5mg listing.

Sources checked October 15, 2026. Reference information for laboratory research.

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