Thymosin alpha-1 vs thymosin beta-4 (and TB-500): different proteins, similar names
Thymosin alpha-1 and thymosin beta-4 share a name because both were first described in extracts of the thymus gland. They are otherwise unrelated: different genes, different sizes and different research areas. TB-500, a common research product, is a short fragment of thymosin beta-4, not of alpha-1.
- Thymosin α1 is a 28-amino-acid immune-modulating peptide, licensed as thymalfasin in some countries.
- Thymosin β4 is a 43-amino-acid actin-binding protein studied in tissue repair.
- TB-500 is a synthetic 7-amino-acid fragment (Ac-LKKTETQ) of thymosin β4.
Side-by-side comparison
| Thymosin α1 | Thymosin β4 | |
|---|---|---|
| Length | 28 amino acids, N-acetylated | 43 amino acids |
| Molecular weight | 3108.28 g/mol | ≈4963 g/mol |
| Origin | Fragment of prothymosin alpha | Product of the TMSB4X gene, found in most cells |
| Main role studied | Immune modulation, T-cell maturation | Actin sequestration, cell migration, tissue repair |
| Related research products | Thymalfasin | TB-500 (Ac-LKKTETQ fragment) |
| Approval | Thymalfasin licensed in some countries outside the US, UK and EU | Not approved anywhere we cover |
| WADA | Not approved in major jurisdictions; treat as S0 | Named on the WADA Prohibited List, with its derivatives |
Why the mix-up matters in the lab
Because the names are similar, orders and labels get confused. Check the sequence and molecular weight on the certificate of analysis: about 3108 g/mol for thymosin α1, about 4963 g/mol for full thymosin β4, and about 889 g/mol for TB-500. Our COA guide explains how.
Profiles: Thymosin α1 and TB-500. See also BPC-157 vs TB-500.
Frequently asked questions
Is thymosin alpha-1 the same as thymosin beta-4?
No. They are different proteins from different genes. Alpha-1 has 28 amino acids and is studied in immunology; beta-4 has 43 and is studied in tissue repair.
Is TB-500 thymosin alpha-1 or beta-4?
TB-500 is a short synthetic fragment of thymosin beta-4.
Are thymosins banned by WADA?
Thymosin beta-4 and its derivatives, including TB-500, are named on the WADA Prohibited List. Thymosin alpha-1 is not approved in major jurisdictions and should be treated as falling under S0.
Is thymosin alpha-1 FDA-approved?
No. It has orphan-drug designations for some conditions, which is not approval.